projectwrx

found a good deal on a STI tmic and i was wondering if it would benefit the stock turbo. im goin to do a tune soon, so if it helps add some hp i might pick it up for the heck of it.

dypeterc

Good question. I'd like to know too

ride5000

there are some advantages to a larger, free-er flowing ic.

principally at high flow rates, when pressure drop is largest, the turbo will be working less hard than it did with a smaller more restrictive ic. this is because less boost pressure is lost across the core than before.

since less pressure is lost, the compressor will have an easier time achieving target manifold pressure. this will result in larger wastegate opening angles, which leads to less exhaust gas back pressure, which in turn means higher VE.

if by now you've realized that reducing restriction ANYWHERE in the charge air/exhaust gas path of the engine helps VE, then you'd be on the right track.

projectwrx

thanks for the info!! but i was mainly wondering how much hp increase i would gain.

VIBEELEVEN

iTrader: (2)

Curious, why did you sell your accessport if you plan on getting a tune?

ride5000

probably, with no other tuning, just on the limit of perceptibility. iow, 10whp or so. the gains would be largest at high load/high rpm use.

with tuning, otoh, you could unlock considerably more, since you could run more boost while working the turbo just as hard and keeping the charge temp just as cool. by considerable i mean at least another 10whp on top of the inherent 10. maybe even 20.

projectwrx

why you all up in my business? haha jp

i got a ecutek from a friend.

subie OCD

iTrader: (11)

By looking at his past threads, It looks like hes sold 2 AP's already
http://64.119.173.9/forums/showthread.php?t=123849
http://64.119.173.9/forums/showthread.php?t=120527

and already has the STi top mount
http://64.119.173.9/forums/showthread.php?t=120217
weird...

dypeterc

kind of a newb, but what's "ve?"

dypeterc

also, would you have to modify the hood scoop?

i just read up a little on intercoolers and how they work. you would get more hp due to the cooler air and denser charge provided by a larger more efficient intercooler (or is it the sti logo on it?). you'd also be safer because there's less chance of knock. if you can find one for cheap, i'd pick one up

VIBEELEVEN

iTrader: (2)

Volumetric effeciency

ride5000

volumetric efficiency is a measure of how effectively the engine is filling its cylinders with charge air.

it is generally expressed as a percentage. this percentage represents the degree to which the air is ACTUALLY inside the cylinder vs. how much THEORETICALLY could be there. so if you had a 0.5l volume while the piston was at bottom dead center, and you filled it with 0.45l of air, you'd have 90% VE. that's actually pretty decent. it's quite hard to get 100% VE, and it's NEVER accomplished over the whole rpm range from idle to redline.

because of the pulsating nature of the way the engine sucks in air, with careful tuning of the intake tracts cross-sectional area and length you can "tune" their resonant frequencies to give you a bump in VE at certain rpm ranges. in fact, with those effects you can actually stuff MORE air into the cylinder than you would be able to under static conditions, and that leads to VEs greater than 100%. unfortunately these tuned port bumps in VE do not extend over more than a narrow band of rpms. it is possible to trade off "gains" for "bandwidth," in that you can get an extremly high increase of VE but over say a couple hundred rpm, OR a gentle bump in VE over say a couple of thousand, but it is actually physically impossible to get both (at least not without resorting to fancy mechanical stuff like vtec).

VE is directly proportional to torque output, since the degree to which you fill the chamber with charge air represents the force which will be imparted to the piston during the combustion stroke. where VE peaks, so does torque output. the inverse is true, too: torque falls off with VE.

the VE/torque peak is also the rpm range which is the most prone to detonating, and requires the most careful tuning, for the very same reason of the charge being most dense and the greatest combustion chamber pressures developed.

hth
ken

dypeterc

Thanks for the info. It's interesting how a turbocharged engine works. Not so boring as a NA engine. Lots of physics involved too. Who said you would never use the stuff you learned in hs

projectwrx

wow, i have a stalker.

im not even going to bother to explain or waste my time. lol