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| Turbo Questions Guys-in Here | |
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| Tweet Topic Started: Sun Aug 26, 2007 8:43 pm (29,802 Views) | |
| Racing | Sun Aug 26, 2007 8:43 pm Post #1 |
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Every now and then i get the "occasional" turbo question,so i thought that on a forum as member limited after all as this(no offense) i might cope to explain turbochargers,sizing,engine parameters and such to the best of my knowledge to those interested. No..iīm by no means god at the subject..but as some of you are aware iīve been into this for some time,and i indeed DO tune and alter engines for a living. Seing that,i often react to how much misinformation there is floating around and to pull my fair share as far as stating what is true-again to the best of my knowledge-.....shoot away. No question to "dumb",to "simple" or whatever.. For starters tho,i hope that most of those into asking Qs are in the know how of how an internal combustion chamber works and why. If not..lemme know and weīll start from there. Jesper |
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| Conrad | Mon Aug 27, 2007 12:10 am Post #2 |
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Therapy Needed
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Thanks for the offer! I imagine I'll be bombarding this thread as I think of things. |
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| maggot | Mon Aug 27, 2007 8:33 am Post #3 |
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Do you have any suggestions for a manual gearbox suitable for my car ? Its a w124 and will have an AMG 3.6 with twin Gt28's. Current plan is to use a modified C36 'box , but I would much prefer a manual. Any thoughts or recommendations would be appreciated. |
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| Racing | Mon Aug 27, 2007 8:50 am Post #4 |
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Estimated power and torq goals? Seing the twin huffers,would it be safe to say that you shoot for 600 for the street? Will the car see track use? Lightened in any way?(approx weight) Will ALS/launch be used? Slicks? |
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| hal9000 | Mon Aug 27, 2007 5:32 pm Post #5 |
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I for one would love it if you issued a little tutorial about selecting turbochargers. I think that I've stated it before, but what you're recommending tends to go against what is generally considered "common knowledge" around my neck of the woods.... Though your results bear your ideas out rather well! Until this year, nearly everybody "in the know" tried to tell me that the Holset HX35 which I selected for my 16V was way too big. Though now it seems like the rice kids are leading the way and starting to make use of the new generation of larger turbos on small engines. It would be nice to have somebody with a bit of experience make a clear explanation of the new school of thought on how to pick a turbo. I've yet to seen any such thing. I think that if you came up with a no-frills explanation of the "proper" turbo selection process which is geared towards people who already have enough knowledge to undertake a turbo conversion (eg, no remedial explanation of a 4 cycle engine operation necessary) that you'd have people in your debt. |
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| Racing | Mon Aug 27, 2007 8:31 pm Post #6 |
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Scott. Iīll be happy to,altho i for one believe that in such a case we should keep it "mercedes". Might sound a little...off the rocker...but trust me. Itīll become quite evident why o state that. Gimme a little while here and iīll do a coarse write up why at least I reason the way i do and what the results have been. |
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| maggot | Tue Aug 28, 2007 9:05 am Post #7 |
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Part of things
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It would be nice to see 600 although the build has been such a pain I'm tempted to run bigger turbos so that I never will have to think about getting more power at a later date. Do it now never to return as it were. Car will be mainly street driven but with occasional track and strip use. Its a "full fat" version so weighs about 1600 kg. Motec600 management has a software upgrade for both ALS and launch and when its mapped I will need to decide if they are worth while adding. Car has no lsd :wacko: so for the limited number of times it will used on the strip and the additional stress on the drivetrain I will probably give them a miss. I am hoping Quaife may have the solution to some of the possible traction problems, but will have to see. Thanking you in advance of any advice you may have |
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| Racing | Tue Aug 28, 2007 10:18 am Post #8 |
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K. Seing itīs a street car any straight cut boxes are out IMO. That leaves us with whatīs available from other cars in essence. If we stick merc,the 717.404 can be MADE to handle that. (Ie modded to do so) These gearboxes are at least available,and as with any Getrags they ainīt an arm and a leg.Modding might be an issue tho as there are few around that even understands how a gearbox works. Tremec of course. Sort of a "standard" solution,but as always..thereīs more to it than meets the eye. Gearing could be an issue.Likewise the issue of prop shaft asf. Seldome hear of them,but i suspect that a DNE street would suffice as well. The jap rip offs of very high quality from the supras,lexus asf. These are fairly good boxes.Mostly 6 speed,and of fairly slim dimensions.No matter the last remark really,as they indeed are used to propel approx 4000lbs and 330hp. ZFs from a "newer" Bimmer M3.Might work,but have friends that have had trouble at the approx level youīre at(500+ approx). A couple of pointers to make this live... Please take to heart that it is NOT just a matter of what the engine does. More so what the chassis will transplant back to the box. Alternating loads from wheel hop and what have you will kill ANYTHING drivetrain in a hurry. IOW,for your 124 chassis make sure to take a long,good,hard look at the rear subframe points primarily. This will also make your driveshafts survive to a much higher degree as those ainīt made to take that kind of punishment either(alternating loads). Likewise,take a good look at the engine suspension points. Again...a matter of oscillation. Firm does it,while solid will drive you up the wall in a heartbeat. (Only engine type to ever consider running solids are a V8 due to its inherent balance characteristics) |
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| Racing | Tue Aug 28, 2007 11:45 am Post #9 |
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Turbos then. First mistake the average enthusiast do is to view the turbocharger as some sort of magic entity with set parameters. This is false. The main and primary part of the setup still is...the given engine. Youīve heard me chant about totalt system flow and dynamic cylinder pressures. So,for the sake of argument letīs disect that. An NAs engine power is a function of the same parameters as is a turbo engine,but limited to the flow of the head/intake/exhaust vs the displacement in a way that is controled by the surrounding air. That means..that we canīt really allow us to expect results by more than the air at hand can achieve.A surrounding pressure that is approx 1 atmosphere. Air as we know it of course have a reference,and one of the culprits is that this reference will vary a little depending part on who you ask(where in the world as there are a few different standards around),and by the physical nature of where one is at.(Variances are relatively small tho) None the less,since a number of yrs back the reference really is set by the flying boys...and is referenced as SL. Sea level. Sea level air is known to be 15degC and 1013,25mBar of pressure(easily converted to fractional system if need be) Point is...that due to whatīs known as the common gas law,air will alter in physical condition depending on temps and barometric pressure. Another thing that will affect airs properties as far as how it burns as an emulsion is humidity. Now...what a turbocharger does....is to shovel air. In a BIG way. To give you an idea...letīs say that we look at whatīs known as a compressor map,and this map for a relatively large turbo tells us that the given compressor will flow around 60lbs of air at a pressure ratio of 2.5(the compressor housing/impeller iīm looking at for my new setup flow inxs of that) (A turbocharger is commonly divided into the cold side(compressor),mid section/bearing housing,and the hot side(turbine)) As we have 1 atmosphere surrounding us...that means that this compressor will flow 60lbs at approx 1.5bars of boost.(Not the entire truth,but just to keep this simple at the beginning) K. Important part to understand here is...60lbs. Air weighs approx 0,0125g/liter,and it soon becomes evident that 60lbs of air times those 0,0125g makes for one MASSIVE SHITLOAD of air. The mass flow of a turbo isnīt something taken easily. Now,the thing is that weīre to shovel that air INTO something,and as different engines indeed(due to design specifics mainly) have different biases and therefore different amounts of flow...we soon realize that the RESISTANCE any given engine will set up to take delivery of that given air will vary. A lot even. Here it becomes very evident that when the average enthusiast starts talking about boost from a given turbocharger as some kind of nomer of power it is downright pure folly and nothing else,as different engines will flow so different. Hence..why some engine also NEEDS a lot of boost to make power. Mainly,because their "NA" speced flow in essence suck,and as thatīs the culprit...we OVERCOME that flow hinderance by increasing boost and thereby ask the turbocharger to perform a higher level of work(nothing is for free...) In short,do make a poor flowing engine deliver we simply force feed it with air to a higher degree-which...make no mistake...have some serious drawbacks. (Induced heat being the biggest one as the higher the boost,the more work the turbocharger is asked to perform,and the more work-the more heat is induced into the air mass-that we in turn need to cool) What iīm saying is that boost is a nomer of what the engine DOES NOT inhale,because an engine with superior flow will make a given boost DROP vs the engine with lesser flow at the same static settings(wastegate asf) as the air entering that engine will not have as hard a time reaching into the engine-as well as flowing through it. This in turn means that the higher flower engine will have more capacity for even MORE power if the need arises. This is an area where many many enthusiast stonewall. Monkey see,monkey do...and no one around is "brave" enough to install a compressor housing that will cater to the basic engines REAL flow properties,and will in effect just strangle the engine short of its capacity by installing a turbocharger to small. It was once set by displacement.We soon figured this was wrong,as...look above. Then...some decided it was a matter of NA power...better,but still no cigar if you ask me. But..where weīre currently at is that if we by investigating the flow properties of the engine try to foresee the flow CAPACITY of the given engine...weīre at least starting to get somewhere. If we take the case of our beloved 16 valvers... In stock form the LOWEST amount of power delivered was 170 out of 2.3 liters of engine. Highest...as far as i know..was the 238 out of the EVOII 2.5. Now...when you break it down..the similaritys between the various engines are big to say the least,and the important part is....the head. The head,because that is where to most of us the "hard limit" is set. Intakes and exhausts is something we always can fab up and alter to hearts desire,while the hard set limits of the head is there so to say. (disrearding porting) Now,the head of the valver is a damn gem. Itīll flow like nothing iīve at least ever encountered for a stock 2.3,and seing the dimensions of valves aso itīs no wonder. Cosworth did the job right the first time out. Seing that...it is safe to asume that the head will SUPPORT towards 300hp in NA form.That is NOT to say that a ported head wouldnīt support it better at those levels,only that it air and flow wise CAN. 300 is a far cry from those 170 which in turn means that there is a vast capacity in abundance. This..is something to have in mind when picking a cold side for the turbocharger,and take to heart that MOST NA engines are designed with SOME overcapacity from this respect. It is also a "known" fact that we should expect 100% performance rise from 1 bar of boost. Might very well be,but the Q would be...whatīs the reference then? Just a number of yrs back the ref was the NA power figure,but in that case the specific engine iīm currently running would put out something like 350sh...which it most certainly doesnīt. Is the correct nomer then the flow CAPACITY? Beats me...but it sure looks like it is what we could be had to expect,and that in turn would mean that by me installing a larger compressor still i MIGHT make the engine at hand deliver in the neighbourhood of 600@ 1 bar of boost. IOW..it comes down to HOW i deliver the air the engine can take. Now,most of you have heard of spool. Spool is the turbochargers resistance to deliver the goods. Spool is to a degree a function of the turbine and compressor wheel MASS,and as the inherent resistance is a squared function of diameter it soon becomes evident that large wheels doesnīt take kindly to fast reactions. True. Now,what weīve also learned is that thereīs a LOT more to this than meets the eye. Wastegate tech and placement is most def amongst those,as what weīre talking of here is a transient condition. The better the layout,and whatīs more the BETTER SEALING the wastegate...the better off we are. Iīve personaly lost track of how many setups iīve encountered that has had what is known as "wastegate creep". Ie;the wastegate "sneaks" open way way way b4 the set boost limit,creating a "leak" for the turbocharger to overcome to start to create boost. This will have EXTREME effects on spool. This is EXTREMELY common,and very few around take the time to investigate why and how the wastegate does itīs job. While on the subject,anything but a stand alone wastegate is a damn waste of time seing that reasoning as we by having an integral WG with the turbo donīt have any freedome of choice as far as primary pipes leading to it nor do we have any freedome of choice as to function. Integrated WGs are for space considerations and price ONLY. Spool... Another thing often overlooked is that ALL turbocharger systems leak. They ALL do,and the ONLY way to diminish leaks is to pressurise the system to check.By checking and taking care of leaks-no matter how small-you will again have taken a big step vs making spool less evident. If we diminish the leaks around...we make it easier for the turbocharger to go through the transient area where it tries to build boost in a major way as well(spool). An often overlooked area of spool is oilpressure. Many many enthusiast never even heard of the fact that a journal bearinged turbo will react STRONGLY to to much oil leading to it. Fact is that a turbocharger will survive on minute amounts of oil,and in my book anything more than 30psi at the bearing housing of the huffer at WOT is a damn waste. I often remedy this by welding the fitting for it shut and dril the same fitting with a 0,1" bit.On my new setup i will put an adjustable pressure valve inline to investigate this further,but suffice it to say that oilpressure at the turbo should be kept DOWN,and this will affect spool time in a major way as well. Turbines then... ..and whatīs more important(total system flow) turbine needs and exhaust backpressure. When we ask the turbine to set the compressor wheel going weīre to "balance" where this happens vs the resistance a to small a turbine will create at high flows(power numbers),so again..this will be a matter of what the ENGINE can cope. There is no such thing as a given turbine A/R will create a certain effect. Thereīs WAY to many variables involved,and the turbine A/R is just one of them. The important part here,when power is the goal,is to measure exhaust backpressure and come to an agreement with your turbo supplier when pickin the huffer up that various turbine housing are available for the given turbine wheel at a reasonable cost.(turbine housings are relatively cheap) This way...you can easily swap turbine hosuing to create different effects on the engine. Make no mistake. We measure intake boost vs exhaust backpressure,and at SOME GIVEN POINT the exhaust backpressure will be HIGHER than the intake boost one-which in effect will make the flow properties of the engine go out the door. So..what iīm saying is that you make a reasonable pick DEPENDING on set parameters and goals.(For "our" valvers that would mean an A/R of approx .8 for a 60mm compressor side would be a reasonable starting point) Turbochargers VERY seldome are a matter of "that wonīt work" or "that will work". Itīs is not that clear cut in practice. As ALWAYS it is a matter of bias,and some setups will work BETTER with a bias one direction while another will the other. Therefore...for any serious setup...you ALWAYS measure,monitor,log backpressure vs boost as a function of revolutions and load. Now,backpressure is also influenced by primary piping and downpipe flow(as well as exhaust flow) In essence,the longer the primarys the "slower" the pulse,which in turn means that for a high end turbo engine the ENGINE parameters will get closer and closer towards itīs NA engine counterparts.(camshafts and what have you) Ie,it becomes even MORE important to keep backpressure monitored the higher level of power as the ENGINE becomes more and more dependant of it. Another thing is that the pressure ratio OVER THE ENGINE(backpressure vs boost) will have a big effect on dilution within the combustion chamber,and that in turns means that the better the pressure ratio the more the ignition timing the engine will cope without detonation-at a given amount of boost-which in turns means more power. I think weīll take it from there,and as can be attested by many by now... The points written down here could certainly be argued,but the main fact remains. I DO run a 450bhp+ engine on the street with these ideas carried out in practice,and i DO so on a daily basis. When the flag drops...the bullshit stops.. :lol: ..and to this day(after 2 full seasons) the merc has STILL to be beat on the street around here(in all honesty it HAS been once...by a tuned 900cc fireblade..then again..i wasnīt on slicks at the time) More to come tho,and then with bias towards what i feel many many overlook and/or fail to see. Driveability and dynamics. |
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| Racing | Tue Aug 28, 2007 12:36 pm Post #10 |
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With the reasoning above in mind... Letīs look at the cold side of the setup a little further. We canīt very well dodge the laws of physics. In situ,every time we impose ANY type of bend after the compressor housing we WILL tranform some kinetic energy the air has(induced by the turbo) to pressure as we can not "bend" an airstream without getting this effect. With that reasoning in mind...weīre simply wasting energy with EVERY change in direction we make,and whatīs more is that weīre probably at one point just "dumping" air into a container for better for worse(the intercooler) IOW,it becomes quite evident that by spending some time with the thinking cap on while designing the layout of the pressure system we can diminish the amount of bends we put into the system to our advantage as the lesser the imposed flow hinderance...the easier the job for the turbocharger(again total system flow) This is a little like...damned if you do...damned if you donīt,cause any car will have the intercooler placed at more or less 90deg towards the turbo and in turn towards the intake. What iīm saying is that at the design state it is important to think twice...and cut once,and that this way of thinking WILL as a chain function have its effects on the final,total,results of the setup. Logic really...cause the less flow hinderance you present for the turbocharger...the less work it has to perform to gain a given level of power/flow. To make things even more complicated...be aware that there are instances where inducing turbulence or resistance might be to our advantage. Intercoolers then. The main purpose of it is to make good use of the common gas law...again. By cooling the intake charge we make the intake charge more dense,which will make it contain more oxygen-which in turn is what need to burn the fuel at hand. True. Problem is that in high performance setups another point of view is often overlooked,and that is the flow characteristics of the intercooler,and then mainly how the end tanks of it is designed. Many many many intercoolers on the market(cheap rip offs especially) have end tanks that make half or more of the intercoolers surface area obsolete in that we get "ejector" properties from it. Ie; we create a pressure drop within the cooler due to how the end tanks are setup,whereby the "lower" part of the cooler often becomes inactive. For a given power...everybodyīs happy as the intercoolers capacity still suffice to cope with the given amount of air(280hp for instance),but as we up the flow...it all of a sudden becomes evident that the intercooler isnīt doing its job anymore. First thing to do...is to suspect the end tanks. Now..this is where it gets tricky to say the least,cause the flow properties of an intercooler will take some serious amount of thinking to straighten out,and IMO is therefore best left to boys that have some degree of experience. So..as the craving for power goes up...be prepared that an intercooler of any sort of performance capacity WILL set you back some serious money. For "average" setups...more or less any intercooler will do. Fotnote. Every now and then thereīs someone using the cooler from a truck. Just donīt. Point is that intercoolers for heavy equipment diesels(or more to the point the elements) are NOT designed for the transient speeds of a high performance gas engine. The "cooling" fins within the element of a diesel cooler are WAY beefier,making them absorb heat in a WAY different way. If anything..and you want to save money...a chinese rip off of the old Garett bar&plate element will suffice a LONG way...if the end tanks of it and their layout is just thought through. |
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| Racing | Tue Aug 28, 2007 2:19 pm Post #11 |
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To continue(yup..iīm at home...backpains coupled with an upset stomach :lol:-so..time to waste
).What many IMO disregard in their hunt for more power is engine dynamics. To be blunt,in recent yrs itīs become an internet rage to have the biggest hard-on via some dyno sheet stating X amount of power n torq. I really frown upon that reasoning. Problem is that this tells absolutely NOTHING of the performance of the end product,and to ad insult to injury more often than not the cars with "red hot" numbers are more or less impossible to actualy drive,and especialy so to drive fast. My thinking along these lines-again-is that within given parameters power is a function of flow.Not boost. Boost brings a number of drawbacks,as not only will intake temps go up as a function (which is VERY bad)but engine driveability will go out the door at an alarming rate as well. One could reason that with boost coming on, the engine character becomes sort of DrJekyl and Mr Hyde-and the behaviour becomes "worse" the more boost is added. Therefore,at least i reasons such that we should aim to keep boost DOWN as best as we can by emphasizing different approaches than the easy ones-look above-to enhance driveability as best as we can. Ie;in the case of the valver for instance,and itīs massive flow capacity,it is a good idea to pick a compressor that will suffice power wise on a LESSER pressure ratio as this will deliver the power with LESS ills from a driveability standpoint.(In plain english-go big) From that respect happiness is often stock,and by keeping the "base" behaviour stock(camshafts and what have you) and thereby setting the limits for the engine in boosted form as well, we simply "ad" boost to make the engine/car fast. Car will this way be as a stocker until boost hits,and when it does it will do so GENTLY(relatively speaking) as we have limited the amount of boost needed by careful picking of the cold side. Of course this at a given point will reach diminishing returns,in that we this way also limit what can be done,but for the most part a LOT can be had power wise within these parameters.MUCH MUCH MUCH more than people in general are had to believe-and the better base flow of the engine...the more rewarding the end result with a minimum of boost involved. By careful investigation of whatīs been mentioned above(measuring asf) we can ad a rather large huffer to an otherwise more or less stock engine to get what is downright redicolous amounts of power for most. Make no mistake. 300+hp in a 190 series car makes for one serious hauler,and thatīs exactly my point.A 400hp one even more so. By this way keeping revs as well as boost limited we also get an engine that will survive,and the added loads we impose by boosting it will be less "costly" over the long run.(Less strain on intercooler capacity aso aso aso) Guess what iīm saying is that for most...in the words of Ali G...keep it real. Most wonīt even handle a 450hp BOMB(cause thatīs downright what it is) as drivers,and as such the "costs" involved in such a setup should be avoided. Benefits are plentiful,of which driveability,dynamics,fuel economy are just a few. Such an engine will also take way less service..and frankly speaking this is THE engine for most as far as iīm concerned. Thereby we get into another aspect of this,and that is how to emphasize and program a stand alone fuel injection-which IMO is a downright MUST for any converted engine to realize its performance,but for now weīll leave that be. Again. By careful examination of the hardparts involved,the layout of these parts and general logic as well as application insight we can come a LONG way,and i see no reason to go ape in selection of parts to beat the living crap out of the already dead horse from that perspective. On a sidenote...stuff like this gets REALLY expensive when you start to reach for the sky. The sky as in with a limited displacement you sooner or later is left to start revving the living behemoth out of it to make even more power,and the added revs WILL kill stuff. Sooner or later. One such weak area of the 102 engine is the stock connecting rods,and these should be replaced if you aim anywhere NEAR the 400 mark with any continuence in mind. |
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| Racing | Tue Aug 28, 2007 2:42 pm Post #12 |
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One often overlooked aspect of boosted engines is the pressures involved and the inherent spikes that comes along with it. This is inherent with the flow of any supercharger,and therefore it might be an idea to ponder what these spikes does as they reach the intake tract of the engine. In essence any engine is just a number of cylinders put together,and as such more often than not fed over a common plenum. If we let the pressure spikes of the supercharger lead unrestricted into the plenum we often get air "bounce" within the plenum,and seing the dynamics of the engines operating range this can take effect....whenever in the range vs the chosen compressor side asf. IOW...complex. So. How do we combat this? Audi spent a fortune developing the diffusor setup for common plenum intakes. (Aduis racing engine development) What it in essence does is that we introduce the pressured air into a "pre" plenum from which we feed the "main" one. The two halves are separated-or connected-via a rather long slit,and the idea is that this slit will introduce a "resistance" great enough to take out the main part of the pressure spikes and harmonics while still regaining ample flow to cater to the engine at high revs and WOT. Point is that the harmonics within the plenum might very well through the work of the engine and its phasing make one cylinder digest more than then next,which in context means that weīll have one or more cylinders running lean when setting the engine up at SOME given rev or load. In short...bad news. What weīve investigated at the shop is how to execute diffusor plenums-and much to our surprise it has shown itself to work fantasticly well. What the "calming down" of the air brings is in practice that the engine will -again- make more power at a lesser amount of boost as the air eintering the various cylinders will be more uniform in mass-which in turn makes the engine MUCH easier to setup fuel and timing wise. Now.many reason as far as the volumes involved,and i for one will go on record and AGAIN state that thereīs more to it than meets the eye...and that it to a great extent comes down to bias. Thereīs by my way of thinking no "wrong" way to execute this as long as youīre into the loop on what youīre doing and why. For the most part when we start to build a turbo intake for "real" what sets the physical parameters is really space. Of course...we could cut the car up to make it all fit,and we sometimes do,but...again...seing what this little write up is all about iīd say tahtīs besides the point. Important part here is to understand that thereīs FUNCTION to be had from a "turbo" catered intake. Again...the idea is to keep the "need" of boost DOWN. ONLY positive results from that. |
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| Racing | Tue Aug 28, 2007 3:40 pm Post #13 |
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Further. We often see turbochargers referenced by; T25,T3 asf Hx35,Hx40 asf asf This doesnīt tell all that much to be honest. What is important is the compressor MINOR diameter(also known as inducer)-which tells us the flow capacity within reason The compressor MAJOR diameter-which tells us within reason at what boost level the given wheel is thought to do its job efficiently. Exhaust major diameter coupled with turbine A/R-which tells us the approx pressure ratio to be expected. Exhaust MINOR diameter which tells us turbine capacity. To check any of these dimension just unbolt the compressor or turbine housing. Itīs done in a hearbeat,and measure physicaly at the wheel with calipers. Point being that small increases or decreases can make for a large variance in function. Then...thereīs the matter of turbo "tech"...like number of blades,pitch of blades asf asf.Any "power slits",twin blades asf asf asf... Once and for all. T25,T3,T04 asf are designations of exhaust flanges. Hx35 is of axle and physical dimensions(as is K27 and what have you) It tells absolutely NOTHING specific enough to be of any use. If we take teh case of the Schwitzers...S364E(my current one) Tells us that it is a huffer of the "300" series axle dimensions on a 64mm compressor inducer. |
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| Racing | Tue Aug 28, 2007 3:43 pm Post #14 |
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Oh. Please let me know if you think my rantings are on the money,or if iīm way to tech or whatever. Iīm not trying to impress myself here :lol: It is all to make this area more comprehensable to the average guy that wants to get into the loop. Jesper |
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| RobertE | Tue Aug 28, 2007 3:48 pm Post #15 |
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Serial victim...
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Makes perfect sense! |
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| Racing | Tue Aug 28, 2007 3:51 pm Post #16 |
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Well that was a short "sum it all up" comment if i ever read one!!
:lol:
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| RobertE | Tue Aug 28, 2007 3:55 pm Post #17 |
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Serial victim...
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No, sorry Jesper, I'll respond in more detail a little bit later - the 'phone just went and i'm suddenly up to my arse in crocodiles. Will revert. All I have are questions.. |
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| Racing | Tue Aug 28, 2007 4:13 pm Post #18 |
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Member
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Funny. I thought the rest of the world was off work and at home just like me today. muscleman.gif |
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| Conrad | Tue Aug 28, 2007 4:16 pm Post #19 |
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Therapy Needed
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I am. Upset stomach too, have been rather sick since Sunday. Back to the slaughterhouse tomorrow though.
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| dave_irl | Tue Aug 28, 2007 5:25 pm Post #20 |
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Defector
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What a great read. Keep it all coming. Very informative. Thanks! (says the guy hiding his set of carbs... :unsure: :D) |
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| Racing | Tue Aug 28, 2007 6:01 pm Post #21 |
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Speaking of which. There ARE a number of good "turbo" carbs around. Most fabled iīd say is the dellorto 40DHLA turbo developed for Lotus by dell at one time. These will support downright redicolous amount of power if need be(weīve seen em support past 900bhp on the dyno over here on a 2.3liter 4 banger),and be VERY certain that the carb "need" of an NA engine does NOT translate to a turbo gun. For example. When Lancia developed the early rally engines they did so with supercharger and turbo both. Carburation was via ONE Weber 32DAT,and have in mind that this engine at the time was claimed to spit out around the 600 mark-which i have no reason to disbelieve. |
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| RobertE | Tue Aug 28, 2007 6:15 pm Post #22 |
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Serial victim...
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I doubt that Lotus ever paid for them... OK, the business day is over, sorry about that interruption... Jesper - d'you suppose that there is some 'golden ratio' regarding forced induction? I only ask because it seems to me that this might be the answer to many, many issues. Also, if, as you say, that this engine (by which I imagine you mean the oversquare 2.3-16 engine) has hidden talents, what d'you suppose the ultimate in-line four might look like? Or - could we be close? Or is the Lancia V4 a better prospect? Get well soon. |
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| Racing | Tue Aug 28, 2007 6:20 pm Post #23 |
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"golden ratio" as you call it...nope. Point being that there are to many variables involved. For instance. You mention oversquared. Ok. Then,would and engine with an R ratio of 1 have a different ratio need than "our" valvers? Most likely as weīre talking gas dynamics,which in turn would make the entire reasoning pointless. Might be that there is,but in that case itīs beyond my knowledge iīll tell you that much. Take what iīve written here as guidance and a state of mind for a plan of attack rather than gospel truth. One thing that strikes you like a ton of bricks when working on engines long enough is that there is VERY little that is cut in stone. As for general ideas as well as sought behaviour from a given engine type,my idea at least is to keep the "theories" coming as i think of them. Just that in this case...iīm one of the idiots around that actualy take theories to practical tests from time to time,and as iīm not alone around here...we strike home on occasions-evidently. |
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| Racing | Tue Aug 28, 2007 6:23 pm Post #24 |
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Robert. On the topic of "Rs". Think about it for a second. As exhaust backpressure goes up with boost,so will a resistance to flow over the motor. This in turn will make it harder and harder for the huffer to "push through",which in turn will come to a point where any real benefits from upping boost will be lost. IOW,the "R" is relative with power,flow and boost for a GIVEN engine. Also hence why we ALWAYS pull out timing as we up the boost. |
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| RobertE | Tue Aug 28, 2007 6:37 pm Post #25 |
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Serial victim...
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Plan of attack - I love that... |
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| RobertE | Tue Aug 28, 2007 7:27 pm Post #26 |
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Serial victim...
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I asked him - he told me. Me talking with Jesper is rather the plumber talking to the hydrostatician He is, I think, a great resource. I shall revisit this tomorrow - a bit of distraction. |
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| Racing | Tue Aug 28, 2007 11:41 pm Post #27 |
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Robert. On topic. Performance wise. I run approx 1.25 bar of boost out of the schwitzer. Thing is... By going WOT out on the freeway in third at 120km/h...i start going sideways out of some reason.Noo.....not dumping the clutch or such...just going WFO in third. Funny isnīt it? Further,it is always coupled with the smell of burnt rubber-where ever that comes from which in turn is coupled with the funny smoke behind the car? I donīt mind though. Have gotten used to looking out the drivers side window as i try to keep the car going straight at those speeds. *scratches head while looking like the moron i am* Is it my specific mercedes that has a bent chassis or need an aligment maybe? Do i need a longer throttle wire? |
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| Racing | Thu Aug 30, 2007 8:40 am Post #28 |
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Funny. Thought you guys would be all over this? |
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| cossie connoisseur | Thu Aug 30, 2007 8:51 am Post #29 |
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there can be only one ;-)
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id just get a bigger engine
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| dave_irl | Thu Aug 30, 2007 9:11 am Post #30 |
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Defector
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Its not all about bigger engines! Big Dave and Goliath syndrome going on here.. Besides, bigger = heavier.. I'd like to eventually turbo my lil one eight after the love of keeping her n/a gives way to appetite for more power, and my driving abilities have matched the performance of the car/ However that probably opens up another can of worms re throttle bodies and standalone fuel management? Though there is a certain dark horse round here thats a big advocate of blown bike carbs.. What are your thoughts on turbos & (bike) carbs Jesper? or do "huffers" and standalone go hand in hand pretty much.. Cheers Dave |
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| Big Ben | Thu Aug 30, 2007 9:17 am Post #31 |
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Sneaky 2.5-16 Driver!
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What about superchargers? Which type is best? Are they easier to fit than a turbo? I think we are all trying to come up with some sensible questions Jesper!!
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| Neil | Thu Aug 30, 2007 9:20 am Post #32 |
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Newbie
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I just want to know if you'd like to swap your 450bhp lump for a lovely 1.8 M102 only 121,000 miles young
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| RobertE | Thu Aug 30, 2007 9:53 am Post #33 |
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Serial victim...
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Sorry, Jesper, a bit distracted. I should have thought the handling issue was to do with the diff/rear mounts; if you are getting a rear-wheel steering effect, which sounds like what it is, then perhaps you need to stiffen the back end. Early E-types did this, and so did the first Aston Martin Virages. The E-type problem was cured by stiffer mounting bushes for the rear subframe. In the case of the Virage, it was fixed by reverting to the original V8 suspension! The amount of sheer grunt you are putting through the drivetrain seems to be perfectly OK until it arrives at the rear wheels. Is there another type of differential which could fit? Quaife, Halibrand, or perhaps a bigger Mercedes one? Also, if you are using a stock prop shaft, then I'm seriously impressed if it hasn't twisted under that load! |
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| Conrad | Thu Aug 30, 2007 9:57 am Post #34 |
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Therapy Needed
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Don't buy Quaife! I have a personal vendetta against the guy since his son fucked over my friend on the track (they both drive T-Cars), and when we put in a complaint Quaife used his "influence" (read, money, blackmail and extortion) to oust our team. |
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| RobertE | Thu Aug 30, 2007 10:10 am Post #35 |
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Serial victim...
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Oh, Dear! Sorry to hear that... |
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| Racing | Thu Aug 30, 2007 7:55 pm Post #36 |
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Cool! Dave. No,not at all. Although i have no real personal experience with em,there are a bunch of guys running bike carbs on the boost around here.Works as well as anything else i guess,but the point with the SA is the ability to 3D program the ign timing-which youīll need on the boost with carbs one way or another no matter. BB. Thereīs no saying which is "best". They all cater to different opinions and final goals. From a pure efficieny standpoint tho nothing beats a turbocharger. All the others have way lower "eta". Seing the work involved in putting any type of boost to a motor iīd say...work wise...it about evens out.Make your choices and take your pick in essence. Iīm for turbos,but thatīs also a lot because they will deliver a higher grade of performance by my way of thinking,and i for one am in it for the speed. Evo.... Look broh... Itīs ALL about the money....SHOW ME THE MONEY!!! :lol: Robert. Nah..iīm just pullin your chain. Problem that arises is the minescule 205/40-17 i use for daily transport.They simply canīt cope the torq,and i spin wildly at basicaly any sane speeds out on the freway when i floor it. Comes with the territory Yup.Prop as well as halfs as well as gearbox and rear is stock 16V. Only slightly...."modded". :lol: (the rear is that is-rest really IS overhauled stock pieces) |
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| jimjimthehumanbin | Thu Aug 30, 2007 9:11 pm Post #37 |
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Interesting reading as always Racing. Don't mean to change this thread but I thought the advantage of a supercharger route would be less lag in power/turbo lag. A friend just got himself a XKR supercharger. Beautiful machine and the power is immediate. 400bhp but then it is a 4.2litre v8. Your getting more then his out of hallf that! We can start a new thread on superchargers. So to combat turbolag is this why twin/compound turbos were developed? Are there others ways around that? Will you be going down the twin turbo route or just one massive turbo? Again you mention the flow of the air through the engine. So ultimately in any engine build, whether turbo or NA, I would ideally be aiming to have even and unrestricted flow through the engine? I'm aiming to build a damn good NA engine first before thinking about turbos. I'm guessing that if my total flow in the build is maximised then a turbo/supercharger will take advantage of this. Came across something called CryO2 in a drift mag by DesignEngineering.com CO2 plumbed system to chill the air and other areas of the engine. Cooler denser air = more oxygen. Are these types of systems of use with higher bhp turbo'd engines or just better designed intercoolers will do? J |
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| Conrad | Thu Aug 30, 2007 9:30 pm Post #38 |
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Therapy Needed
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Unless you have seperate banks of cylinders, twin turbos are pointless - I think. I'll let Jesper handle that one. :lol: |
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| Racing | Thu Aug 30, 2007 9:38 pm Post #39 |
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Jim. Yeah,you got the concept.Itīs about....total system flow and dynamic compression ratio. Now,of course turbo lag is a matter of sizes of the turbo at hand,and quite correct the smaller the turbo..the less the lag. However,again,thereīs in that case a LOT more to it than that. 1st iīd say is careful programing of the engine.How you adjust fuel vs ign have a profound effect on lag,and even more so on engine response and dynamics. When people in general speak of turbo lag...they normaly visualize that until boost hits itīll be like putting your foot into a bucket of crap. Might have been...at one time. But the thing is that in recent yrs,as we learned to program the boosted engine,we could keep the static compression up and just compensate for the boost by retarding timing when it hit. This leaves us with an engine behaviour OFF boost thatīs about as any NA euipped one. Ie;youīre left with an engine behaviour like a "normal" car for any routine driving conditions. So..with this setup the boost is there to "fill the void" as you depress the pedal. Further,stuff NOT related to the turbo has a profound effect on lag too. Like...wastegate sealing.If the WG does not absolutely seal(and most donīt) the transit area(for the turbo) where it start to build boost will be advertly delayed as the turbo will have a MUCH harder time passing that "wall",and when it does itīll often do so with a "bang" performance wise. More,due to this weīve learned to control the control PRESSURE for the wastegate by the use of an electronic solenoid in turn controlled by the ECU-and in the long run MAP sensor of the system. This way we can guarantee that NO pressure what so ever reaches the WG to lift it until the set parameter within the ECU,and as such we can focus on the physcial sealing properties alone of the WG. Further still,it CAN make for a rather large difference in spool to keep oilpressure at the turbo under control.Most turbo setups donīt. A turbo will survive on minute amounts of oil,and any excess will slow the spool down in an appreciable manner. Speaking of spool,to give you an idea we are these days comfortable at making boost with a turbo engine from a standstill. There are several ways of making this happen,but one of the more common/fabled ones is something known as ALS. Anti Lag Switch. By depressing this button a "second" map of the ECU will come into play which injects surplus fuel and REATARDS timing making the emulsion burn in excess in the hedder.This exhaust mass is "heavy" enough to get the turbo going,and you will have boost out the ass right off the line. Drwabacks are that the temperatures involved will eat turbines alive...but for racing use it works REALLY well. To go on then...IRL and practice thereīs no reason what so ever to go twin turbo these days.Itīs just a dayum waste of money and time as the turbos of today are THAT much better in materials as well as tech than just 10yrs ago. To make a turbo capable of flowing inxs of 1000hp worth of air work on a 2.3 liter 4 banger FOR STREET USE is an absolute reality,and in all honesty...if you feel the need for more than that to take you to work...youīre WAY off the charts in my book. There IS however as youīre touching on various ways of putting more than one turbo to work.Like Hyperbar turbocharging,sequential turbocharging,two stage(or more for that matter) aso. Various ways of,from a tech standpoint,attacking various goals. |
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| jimjimthehumanbin | Thu Aug 30, 2007 10:13 pm Post #40 |
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Thanks for the indepth reply Racing. Like you said the first part of any modification is to question it and have a goal in mind. As there is a different way to achieve each goal and one way is better than another. The only turbo car I've been in is a subaru impreza and the turbo kicked in hard when he starting going hard on the accelerator. Is that normal? I would prefer a smooth progresive power delivery like the XKR. From what I've been told that it has some fancy variable valve timing to match the engine speed all controlled from the engine management computer. I'm guessing that a similar way of achieving this is as you say getting correct mapping done. So you're aiming for 900+bhp. How are you going about that. I'm guessing one thing you will be addressing is the fuel supply. Would that be upsiezed fuel lines and freer flowing filters, buffer tank? Kinda of drag style? |
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