you are asking for trouble its a guesstimate which should give around (give or take) 250rwkw on a stock engine which would max out injectors
YOU my friend are so misguided its almost laughable zx299! In fact, it IS laughable and I cackled away, almost hysterically at times for quite some time after a few reads of your stuff!!! You have read NOTHING from either drz400y nor myself who obviously have a far higher grasp of hydrodynamics than most on here. I gave you some relevant analogies in hopefully plain enough Australian but I put it to you that you have blatanly ignored them. Are you are mistakenly thinking of a positive displacement type compressor such as a Roots type blower then you might be juuuusssst a little more in the right direction...... You are caught in this foolish vortex where often other uninformed turbo riceboys somehow seem to believe that pressure and airflow are 2 distinctly different and unrelated animals and believe that you can have 2 distinctly different "7 psi's" One where the motor will pass "X" amount of CFM at 7psi and the other where the same motor will magically flow "Y" amount of air at 7psi because a different turbo was used....OMFG! What?? are there different types of psi and cfm of air around here??????? I particularly love this one: Once more m8...just for you.. it farkenwell DOES....... and engine is a POSITIVE DISPLACEMENT device. Its thew end USER of the air and uses FIXED amounts depending on certain parameters. Lets just say it uses 3000cc of air each cycle at ambient pressure which is 14.7psi, 1 bar, 29.92 Inches of mercury or in laymans terms is atmospheric (atmo) pressure. Now, you KNOW it uses 3000cc of air per cycle at sea level because its 3000cc swept volume. This will result in an airflow figure of *blah* CFM and then that is multiplied by how many cycles (revolutions) it runs at. This is called RPM (I really cannot be bothered working it out and converting it. Do it yourself if your keen) In effect, its a pump.........OK? A positive displacement pump. You can only poke thru it so many CFM @ *X" rpm @ Y psi pressure. Remember, its a POSITIVE displacement device. This means the flow, thu the motor is FIXED at set revs and PSI boot pressure. Now, lets use a little imagination here and increase the air pressure ABOVE ambient, which is 14.7psi, 29,92 "Hg, atmospheric pressure at seal level or whatever else you would like to call it. Now, the pump...sorry engine has air shoved down its nose at TWICE ambient pressure. This equals 2 bar or 29.4psi. DOUBLE the pressure yer? Well, now the engine consumes 6000cc of air per cycle (actually it wont but for the purposes of the exercise its close enough) But ONLY 6000cc of air. Still with me? So now, it should flow double the CFM for the same rpm but at the higher boost pressure. Everything is related and dependant for the purpose of this exercise. DROP the available psi, the CFM drops. Drop the rpm's and the CFM drops. Lift psi and cfm increases. But INCREASE available CFM only and NOTHING happens. Now, a turbocharger is NOT a positive displacement pump. In fact, its a centrifugal compressor relying on wheel speed to compress along with a maximum compression ratio of something like just under 5:1 ( I cant recall exactly). However no matter WHAT size of turbo you attach your POSITIVE displacement pump (engine) at a fixed PSI and given rpm), the airflow (in CFM) thru that positive displacement pump (engine) REMAINS CONSTANT. The boost pressure remains the same because the wastegate says so and the CFM remains the same because the engine says so. So, the size of the turbocharger ALONE has NO effect on the CFM usage of the engine UNLESS the boost pressure is INCREASED or decreased of course. The bigger turbo simply allows a much higher CFM POTENTIAL. This is to say that it will flow MORE CFM of air at HIGHER boot pressure and HIGHER engine RPM's. You still with me? You didnt read my application did you? My VG30det has a T66 turbo. If you know anything about turbos youll know this turbo is capable of flowing up around 750 Hp. Is a big farker. But is big only in POTENTIAL. If the fixed user of air on the end of it cant flow it then it goes NOWHERE at 7psi, the wastegate opens up, bypassing hot exhaust gas past the turbine wheel and slows the shaft speed and lowers the compression ratio of the compressor side of the turbo. Mine runs like a kitten at 7psi all day. Probaly capable of 30 psi + at a guess if a lot of things are equal. However, because the SAME cfm of air passes thru our constant displacement pump....errr sorry engine for the SAME rpm then the SAME amount of fuel is injected. Simple as that my furry friend! Now, any differences in power output at fixed pressures and rpms are directly a result of the efficiency of the whole turbo setup. Pumping losses. The air pressure built up between the cylinder and the turbine. Higher the boost pressure the higher the exhaust gas pressure forcing the piston back DOWN the cylinder during the exhaust stroke. Turns the engine into a bloody compressor = power LOSS. Small wheels in a turbo have limitations with regards to airflow (cfm) and pressure. There comes a point where small increases in boost pressure require hug increases in shaft speedand a further result is gross increases in exhaust backpressure and still furthermore gross heating of the compressed air due to "beating" of the air by the turbine blades whizzing at grossly high speeds so far out of its efficiency "map" its a joke. Exhaust pumping losses can actually in gross cases cause the exhaust gas, at far higher pressures than the inlet charge to travel back up the inlet during the valve overlap phase, diluting the fresh inlet charge and in fact shove it back up the inlet tract and this can be further aggravated by the fact that poppet style engine valves can actually be held off their seat by high gas pressures BEHIND them. Less fuel and oxygen = less BANG High inlet gas pressures result in lower air densities. From memory, its something just under 4 deg.C increase in air temp per PSI. And THEN add inefficiencies of the compressor wheel design (none are anywhere near perfect) = MORE heat added. Higher temps = lower density = LESS oxygen = less BANG. Intercoolers can only account for so much heat. Start adding all these negatives together and you can see gross power losses simply by overboosting (overspeeding) a tiny turbo even tho it still delivers the boost! I suggest YOU ZX 299 do some careful and thorough research rather than relying on vague guestimations, heresay (possibly from the likes of from Nissan Silivia dot com et-al) and just plain ignorance (which is not your fault by the way) and educate yourself on some simple hydrodynamic theory before making such grossly incorrect statements. Now, your post is further full of what amounts to barely half truths down to barely disguised bollocks, accusations of someone being "naive" which is plain crap and taking shortcuts along with a ludicrous and totally unrelated analogy throw in for "good" measure..... You dont comprehend too well for someone who is obviously well educated, spells and puntuates accurately....... I could sit here and type away for the next 2 hours systematically debunking every preposterous claim you have made but really m8, youve done it pretty successfully all by yourself. For now, Ill see where this debate goes. But before you get all hot and bothered, and possibly even decend into the bottomless pit of automatic game saying and flaming, I suggest again that you do some thorough research on the topics you so flippantly diss. but are so glaringly ignorant about. Way it is M8. E
LOL....yes I know But I genuinely want to know the answer. So can I put it up for further discussion to those that know more than I. I'll rephrase the question. When boost pressures are quoted (what ever they are), where are the readings taken from? The reason I ask is because (uh oh..here goes) surely a plenum at constant pressure X (lets say 10psi) must be flowing the same amount of air into the engine regardless of what pump is suppling the pressure (pumps may be working harder or easier doesn't matter here)?? The cylinders would all be exposed to 10psi of air pressure. Therefore at 10psi volume Y of air would be forced into the cylinder during a constant time increment Z. This is all happening down stream of the turbos and therefore at this stage all things are now equal. Admittedly other factors (restriction, air flow, volume etc) may vary between the turbos and the plenum. That's why I'm asking where the pressure is being measured.
Very good explanation Tas. Boost pressure is measured in the plenum for the simple reason being that the air in there is as close as we can get to going into the cylinder. Essentially a given psi is the same volume of air on the same engine, Tas has explained it quite well in his reply above.
I have also never really understood this as 9psi is 9psi. But how is it that Rob260 made 300rwkw@9psi with 2871RS turbo's? Surely they must be flowing alot more than stocko's @ 9psi
They obviously are, bigger turbos WILL FLOW MORE AIR END OF STORY. My dads R33 on a before and after run on the same dyno went from a stock turbo at 12psi to a GT3540R 1.06 on 10psi.....same tune....wanna know the difference? it went from 194rwkw to 225rwkw with less boost, same dyno, same day blah blah. Bigger turbo's will make more power because they can push more air in at the same pressure. If this wasn't the case people wouldn't upgrade turbo's because there would be no point. Would be like saying oh my zed at 14psi will make the same power as that guys with the GT2871's koz we have the same mods, you know.....koz 14psi is 14psi no matter what turbo
Just to be sure... the gt28rs turbos are the 'next size up' from stock? Pretty much yeah? Like I didn't get my turbos mixed up or anything?
Pretty sure it was the GT2560's that were the nextsize up? (but i've heard them referred to as GT28R's aswell?) Wouldn't mind getting my hands on a set of GT2860-5's
yeah i have read what old mate says, it makes sense, but in the same breathe i have seen exact engine with a bigger turbo on the same boost level make more power? double ew tee eff.
ah okay must have gotten GT28RS confused with GT28r's (as in 2 of the GT28r) Still though.... i don't know much.. But from what i assume, the ECU would control the engine based upon the readings from the sensors. So I don't think the sensors would "know" that the turbo's have changed to a slightly bigger size. Therefore, from what the ECU knows, it would just receive slightly different from usual readings from the sensors compared to the stock turbos. But these readings are meant to be "flexible" in a way to cater for different levels of boost and flow and all the other little variables along the way. So what I'm trying to say is.. Wouldn't the ECU be flexible enough to allow for a slight size in turbo change without too much compromise in how the car runs? Sure enough for a big turbo you'd need bigger changes. But if you're still running within the parameters of the stock turbos i can't imagine how it'd send the ECU haywire?
in short yes, i know there is proper ways to do things, and theories and "physics" but shit works. i have had NA rb30s with 170cc injectors turboed using huge fuel pressures making close to 180rwkw. you can trick computers. a dyno helps.
That exhaust housing has a whole heap less restriction than the stock turbo, less restriction means more air volume to achieve the same pressure.
Exactly, same pressure, more air, more power......i don't see why there is even a debate going on about this?
What they are saying is that the engine flows a certain CFM at say 7psi. but they are not taking into account that the stock turbos at 7psi or 14psi isnt using the engines max CFM at any rev where the Gt28rs does . thats where the power difference is..if that makes sense the way I'm explaining it .
Now that makes sense, obviously bigger turbo will make more power and flow alot more. The way i was reading tas' post was that any turbo at 9psi will give you same power. (i was reading it wrong)
Apparently the whole subject is now moot.... It appears Chesutiko has got his turbos confused. His question should have related to a highflowed oem turbo (instead of the 28RS that he stated). This brings his "project" back to the realms of possibility and I would suggest furthering his research on the highflows. Furthering the seemingly endless "debate" that followed: SRB-2NV stated his dad's turbo change figures & was dismissed with the following explanation for the increase : and yet we are to believe that same physical theory doesn't apply to the 28RS (which is huge in comparison to the oem turbos). Tassuperkart, I take my hat off to you in your efforts to test the world of possibilities with your turbo setup. For some reason you appear to be trying to shove that camel through the eye of the needle (but for the life of me I can't understand why) I am 100% sure that Chesutiko's original turbo question did NOT relate to him wanting to emulate your setup
Zx299 there is only one statement you have made so far that makes perfect sense. I gotta say that this thread is one of the funniest threads Ive participated in for a long long time. Baaaahahahahahahahahaha use a bigger turbo at the same pressure and you magically FLOW more thru your engine bwaaaahahahaha!!!!!!!!!! *wipes tears*.............. muwaaahahahahahhahahah! OK then, you must be dead right and some of the smartest tuners and spannermen on this forum along with an aircraft engineer dont know shit!!!!! Some of you guys are farken funny! Believe whatever you want to tho coz you guys sure DONT read/understand anything valid thats for sure! I think this thread is well and truly dead!!!! Lock it please mods if nothing more than posterity! It deserves to live on forever! L8r E
