Silly Boost Question

[Roy]

If there are two cars, one running 15 psi, and the other running 20psi. You would expect the car running the higher boost to create more torque.

But, whilst they are still spooling and ramping up to their set boost level, would you expect the car running more boost to make more power even though its yet to physically run any higher boost then the other car?

I suspect wastegate creep could account for more mid of the car running higher boost, as it is less likely to crack as early?

Anyone with any real experience or dyno print outs showing an increase in mid range from one run to the other, only thing beign changed being boost?

[Adriano]

both cars assuming they are equal,, the one running more boost wil only make more power when its boost is higher than the other

[R31Nismoid]

If the ext gate is correctly setup.

It wont crack before it should.

15psi or 20psi, the gate should only open once the boost has reached that level. If there is creep, then the spring is too soft and so on.

[Roy]

Im not too sure thats true Ash, could be, but the physics doesnt suggets it.

Anyway, its not really the question. If on your old setup, if you ran 16psi, then 22psi, did you find your torque curve was fatter even when the thing was ramping onto boost through the 5-15psi range?

[R31Nismoid]

Why dont they? Would love to know how its different.

I went from a 7psi spring/17psi, and you could clearly see it was creeping, you could hear it cracking open aswell ever so slightly before target boost was reached

Soon as we went to 14psi spring/17psi, you could see it on the dyno fully loaded it wouldnt open till it hit the 17.

Getting a spring as close/spot on to the gate it shouldnt let it open before.

How can it? Should the spring not hold. It is related, you brought it up

I can say i ever checked the 5-15 range to be honest.

Nor did i ask about it. I cant say i noticed a difference before hand, it was only after it was on boost as the thing really wokeup using 24psi as opposed to 17psi.

Felt a lot more lively without even using the extra timing and so on.

[Roy]

Has anyone got dyno sheets of their engine showing torque cruve at different boost levels?

Forget wastegates...i hear what you are saying ...but take a car and run it at 15psi. The run it again at 22psi.

Would you expect their to be a difference in torque range while they are ramping up to 15psi? Sure when you do the 2nd run up to 22psi it will make more power, but will the curve be moved to the left at all?

I wouldnt expect it to, but im a bit confused by some results i saw the other night if a few cars on the dyno. Two same engins, but different turbos. Both makign boost at the same rpm , the boost curves look the same. Only the car running higher boost is making more power earlier. Ok so they run different turbos so thats to be expected. Only the car running higher boost is makign a lot more torque a few humdred rpm earlier????

[RANDY]

Sounds like different setups... even though the motor is the same, a cam, timing, air intake temp, spark, fuel.. they should all make torque differences.

I'd imagine, as Nismoid suggests, that if I dyno'd my car at 7, and then at 10, the curve should be exactly the same up until the boost goes over 7, at which point the first run would have the wastegate open and stop the car from really making any more boost. 2nd run at 10psi would see more boost, and the actuator open later, as more pressure is built up.

The leadup to the wastegate opening shouldn't be any different. The ECU/car doesn't know when the boost is going to be dumped out the wastegate, so nothing else should change before that happens.

Still.. that's what i'd assume from theory, and i'm keen to see any results! (obviously same car, same day, same setup would be the only fair test)

EDIT: hmm... so... if that was confirmed, then possibly the wastegate actuator spring could be a culprit? A guy running more boost may have put in a harder spring, to better match the desired boost pressure, and therefore it holds boost better. Another bloke runs his standard setup on higher boost, and perhaps some of the pressure is lost through the wastegate because it's not holding as well as a stiffer spring. That's the only thing that I can think of that might explain it.

Edited November 11, 2006 by RANDY

[mad082]

if it is the same car with the same turbo and you change the boost from 15psi to 20psi (using a wastegate set at those 2 pressures) then there will be no power difference untill the boost goes above 15psi when you have the boost wound up. from the moment the second setup goes above 15psi the power and torque will change. below that the will be 100% the same.

if it is 2 different turbos then it comes down the compressor properties.

[khunjeng]

Only the car running higher boost is making more power earlier. Ok so they run different turbos so thats to be expected. Only the car running higher boost is makign a lot more torque a few humdred rpm earlier????

I'm not sure what the issue is, more power eariler..then why are u suprised it makes more torque earlier considering they related.

[Roy]

...yeh, another forum guy Fat-GTSR, he seems to have copious amounts of mid range for an RB20, and it seems to coincide with him running way more boost.

[Adriano]

This could be due to the increased compression ratio of the n/a motor making the setup more efficient, hence more torque.

[Roy]

Sorry, typo...an not na

[R31Nismoid]

He isnt using the same turbo as you Troy

The GTS-R turbo is different to the trust item you have

[NISSANR33GTST]

no 2 setup are 100% the same, don’t forget. engine condition, heat, wear exhaust ect etc, everything matters. Even 2 identical cars 1 may be something slightly diffrent causing different outcomes.

As said

"if it is the same car with the same turbo and you change the boost from 15psi to 20psi (using a wastegates set at those 2 pressures) then there will be no power difference until the boost goes above 15psi when you have the boost wound up. from the moment the second setup goes above 15psi the power and torque will change. below that the will be 100% the same. if it is 2 different turbos then it comes down the compressor properties."

is all there is to it, and don’t forget dynos aren’t 100% accurate and are effected my environmental conditions. Just like cars are with heatsoak

..a dirty air filter can be a factor .. if you get what im saying.

[Roy]

Yeh, i appreciate ppl saying they are different engines...but what im sayign is FATGTS-R (from memory) made a lot more mid range and torque when he ran a higher boost level then when he ran lower boost.

Driving my car at the moment on 21psi, im nowhere near hitting or hearing the gate and its driving with more midrange. The comparisonbs between two different motors are pretty inconclusive, you are right. But it just seems that these two particular expamples of RB20s when running pretty high boost...well it seems to wake up the mid range???

Then again if FATGTS-R reads this, he may be able to comment on whether i understand correctly an old post of his

[paulr33]

i cant see any logical reason why car 1 running 10psi and car 2 running 15 psi would make more torque earlier in the rev range. its just manifold pressure, forcing more air into the engine. i see no reason why it would force it to make more torque ealier (if thats what you are expecting). once car 2 reaches the more boost pressure then sure, more torque is possible.

thats assuming car 2's compressor wheel is still in its efficency island as well

[grim32]

Its a shame ive got a 1 bar spring in the wastegate as im getting a tune done in the morning. If i had a 7 psi spring i could get two different boost printouts done, and no im not gonna put 20psi into a na motor, well not yet anyway lol.

In theory i dont think it should make any more torque untill it sees more boost but i do think by seat of the pants feeling they do pull harder down low for some reason on higher boost

[Roy]

Hmmm...thinking about it, i dont see why my car seems nicer to drive on higher boost?

It doesnt make sense, and i dont think its a leakign gate, otherwise i would hear it???

Anyway, doesnt seem to make sense

[iz32]

just my experience to add, no answers here.

my car seems to feel like it has more torque when im running higher boost.

ie: having my controller set to 1.36bar as opposed to 1.05 bar, then whilst general street driving and not winding it out, it seems to pull harder even though im not hitting its max setting

(hitting around 0.7 - 1.0 bar thru the gear changes for example)

i'd be interested to know if this is caused by a fault like the wastegate actuator, as suggested, cos my turbo is in for a rebuild at the moment.

Edited November 12, 2006 by iz32

[NISSANR33GTST]

id just put my time into thinking about other things.

if its the same, nothing will change till more boost

diffrent boost controller are the only think i can say would change it slghtly