Stage 1 boost has returned to stock levels

[PT-Dave]

quote:Originally posted by 3BarBoost

Sorry guys, but you'll find that we are making more torque than any other front-drive car out there. Rear drive cars have heavy enough trans to handle the extra torque, but there isn't a whole lot of room for a big heavy trans is front drive.

We are giving you as much as the trans will let us. And we'll give the full power rating to you all the time, something your turbo trans am couldn't claim (ie hot weather or altitude).

Let's assume that I go out and purchase a Level 10 Stage 2 tranny and torque convertor that is rated to over 650 HP. How does one then get the extra power still in the Stage 2 PCM? Or will it be necessary to go with an aftermarket big turbo and a piggyback ECM with some kind of additional fuel control? Where do we go from here?

[3BarBoost]

If the tranny and halfshafts are out of the way, the sky is the limit. The stock turbo with everything tweaked to the moon is good for a little less than 300bhp. Stage II has 3 bar (heh) MAP and TIP sensors which will let you run to 30 psi of boost. People are making north of 300 ft-lb with 18 psi. You do the math.

Stage III is the next step, as Stage II runs out of turbo. The Stage III turbo can flow about 50% more air....

[crazyjoe]

At what point does the stock turbo cross the line where increasing the boost isn't efficient anymore? You know, because it begins to blow hot air?

[3BarBoost]

Depends what you mean by efficient. All turbos have a 'choked flow' point where it doesn't matter what you do they won't flow any more (see above for stock limit). If you force it (hard to do), you can overspeed the turbo and usually the turbine separates from the shaft and dies a horrible death.

[Steve03GT]

quote:Originally posted by 3BarBoost

Sorry guys, but you'll find that we are making more torque than any other front-drive car out there. Rear drive cars have heavy enough trans to handle the extra torque, but there isn't a whole lot of room for a big heavy trans is front drive.

We are giving you as much as the trans will let us. And we'll give the full power rating to you all the time, something your turbo trans am couldn't claim (ie hot weather or altitude).

We're making more Tq than the Cadillac 300 Hp NorthStar and Pontiac 3.8L S/C engines??

[hyracer]

Hey guys/gals...I don't think you realize how great our little 2.4 turbo-engine is. My wife is interested in the Mazda RX8 so we recently took one for a test drive. This thing is rated at 250 HP at 8500 RPM (redline is 9,000 RPM!) in the manual version (auto is rated at 210 HP). We took it out for a test drive and the salesman told her to "go for it"...I asked her twice if she had the throttle all the way to the floor because it didn't even compare to our GT's when the turbo kicks in. When we got home I looked at the brochure and their engine is only rated around 160 ft. lbs. torque! The RX8 would whip our a** in the twistys but give me my GT at any stoplight.
I'm talking her into test driving a SRT4 next...
Deen

[crazyjoe]

quote:Originally posted by 3BarBoost

Depends what you mean by efficient. All turbos have a 'choked flow' point where it doesn't matter what you do they won't flow any more (see above for stock limit). If you force it (hard to do), you can overspeed the turbo and usually the turbine separates from the shaft and dies a horrible death.

Yeah, I don't mean overspinning. For example, if tyou take the Garrett T-25 turbo on my Talon, after about 15 - 17psi, you get minimal returns for any psi increase beyond that. Because the turbo is less eficient, it is heating up the air rather than really increasing pressure, thus negating performance gains from increasing boost.

Just curious.

[TurboDanny]

quote:Originally posted by 3BarBoost

Sorry guys, but you'll find that we are making more torque than any other front-drive car out there. Rear drive cars have heavy enough trans to handle the extra torque, but there isn't a whole lot of room for a big heavy trans is front drive.

We are giving you as much as the trans will let us. And we'll give the full power rating to you all the time, something your turbo trans am couldn't claim (ie hot weather or altitude).

Is there any difference between the Auto and 5speed? I would think the 5 speed could handle greater loads. Sounds like DC needs to offer an AWD option! (I know, I know, $$$$$)

[3BarBoost]

crazyjoe:
Most modern turbo compressors can run about 3 to 1 pressure ratio at about 60% of peak flow. So if your wastegate is shut and you are providing enough power to spin the compressor up high enough, you multiply the turbo inlet conditions by 3. At peak torque, which is roughly 60% peak flow - air cleaner depression is about 3 psi vacuum, so 12 psi absolute * 3 = 36 psi. Therefore the turbo can make about 21 psi boost. However, at peak flow the max pressure ratio line drops to around 2.5 to 1. With air cleaner depression down to 10 psi absolute, only 15 psi boost is available. The compressor map is bounded by the maximum compressor speed at the top and max flow on the right. Usually these edges represent around 50% compressor efficiency - which is really poor. Going off the edge of the map usually also means overspeeding.

You can see in order to maximize the use of a compressor, you need a wastegate solenoid running the boost level - because a manually-controlled fixed boost level would try to overspeed if set too high. Bigger diameter compressors can achieve about 3.6:1 pressure ratios or better, however they are just too huge to be used on passenger cars where driveability is important.

TurboDanny:
Yes. Torque converters multiply torque, so we have to reduce boost in first gear. The Getrag has skinny first and fifth gears, so torque is reduced in those gears as well. First isn't so bad because you can still easily spin the tires even at the reduced boost. Fifth, well you should downshift...

[knowyourturbo]

Hey there 3BarBoost, I've been reading all the posts about boost, and returning to stock levels. Something I read years ago stated: every 3 PSI of boost, equals close to ONE compresion ratio increase. So in reality, our 8.1 (or so) compresion ratio jumps to 13.1 at 15 PSI. And I'm sure we all know that a high compresion engine NEEDS high octane fuel, weather N/A or forced induction, does this sound pretty acurate to you???? Stew