blau928

You guys need to forget about PSI and focus on charge density, temperature, fuel ratio, and CFM going into the cylinder.

PSI is resistance to flow. You can make more power at a lower PSI if you move more air and fuel at a denser charge ratio through your air pump (engine)

Cheers,

m21sniper

Tammons- "I have read that book a million times and it is a good book, so explain to me how vitesse is getting 330 rwhp out of 2.5L at 15 psi. Thats 380 at the crank. I had a race turbo builder explain the concept to me a while back."

Vitesse has obviously done other mods to the engine that raised the unboosted HP output(such as fuel system enhancements, air flow enhancements, improved exhaust, etc, etc), or is running a very efficient well built system, or both(and i suspect 'both' is the actual case).

What one could do to see exactly how much power the turbo setup is actually giving them is to set the wastegate to full open, and run a dyno run like that(N/A). That will give a baseline HP rating(minus the drag of the turbine/compressor on the unboosted system, of course), and then when you run the test with wastegate function restored you'll see the actual gain you're getting from the forced induction system.

And of course the most important thing is the induction and exhaust system efficiencies of the forced induction system itself.

On a 1000hp output system if you change system efficiency by just 5% you've now changed power output by +/- 50HP.

m21sniper

blau928- "You guys need to forget about PSI and focus on charge density, temperature, fuel ratio, and CFM going into the cylinder.

PSI is resistance to flow. You can make more power at a lower PSI if you move more air and fuel at a denser charge ratio through your air pump (engine)"

Completely true. I've mentioned this many times in other threads and i covered it here under the term 'system efficiency'.

A -90 trim turbo will move FAR more air at 6psi than a T-03 will even at 20psi simply because it is more efficient at moving vast amounts of air.

blau928

M21,

Good to hear.

There are so many comments on just upping the PSI and getting more power that it is silly... Except when the engine grenades...

tammons

Exactly what I was getting at and most people dont seem to understand that point. Raise the volume of cool charge at at the same PSI and you are making more HP at the same PSI, and in Johns case that is via a K26/8 hybrid TC. I have never bolted one on, but its basically a chip, maf, injectors (72#), hybrid TC and everything else is stock. Stock head, stock pistons, stock intake, stock intercooler, stock headers etc. You would probably need a 3" exhaust to get that hp #.

m21sniper

As i suspected, he's made a lot of other changes beyond just bolting on a turbo kit.

JimBob951

The kits from John arn't cheap, but the come highly praised.
http://www.vitesseracing.com
Consists of turbo, MAF, piggyback, chips, software. May need to go with bigger injectors, but that's it.

Jim
87 928S4
87 951

BC

Its a bad habit we must remove from our thinking.

Herr-Kuhn

It's all about mass airflow. Too small a turbo will make lots of boost down low but will be a restriction up top. The cooler and higher pressure the charge the more power...assuming your pumping losses are minimal. I used two K-24s on Goldmember...because of the 3-spd AT. I could have made a lot more power with K-26 at the same boost levels...mainly because the hot sides are larger...we will determine just how much more very soon...I have my first set of "production manifolds" going through the fab shop now. These will fit K-26 in place of Reeve's IHI RHB-6. My goal isn't "more" power, but rather more useable power....this is the key...minimize lag and not choke the top end off. I beleive 385-400 WHP is very possible with two K-26 and moderate boost levels.

Still, for efficiency I stand by the exhaust driven turbine as the way to power a compressor...or two! True, super makes boost without exhaust back pressure...but you pay the penalty at the crank pretty hard...especially for screw type. I have seen some very nice K/B screw units make big power...but they would still be shy of the power two big turbos could pull down. With the 928 there is a limit I'm sure. I'm thinking 600-650 HP max for the driveline to even think of having a reasonable life. I have some documentation from early 1971 showing two large garretts (oops Air Research) on a 400+ CID mopar with two extremely crude looking log manifolds. That car made 1130 HP...crude turbo manifolds can support huge power levels for sure. With the roots blower the same car made like 850-900 or so. I think the delta would be less today because the new blowers are much better, but for mid range and top end I still think the turbo has the edge. All this talk about headers with turbos...I believe it to be over-rated...some advantage...sure, but not enough to justify the added $$$ for a street car. I'm still toying with manifold concepts for the new build...you just never know when I might change my mind.

Yes, Corky is really up on this stuff for sure...check out the Bell Intercooler website for the cobra twin turbo he is building. A header fan running logs! I was told that engine was to make 650 HP on 10 psig. A real nice piece of work for sure. 650 HP on about 2,100 lbs...sounds like a trip to the hospital to me...but so does 600 HP in a 928.

tammons

If you want a real axle breaking, clutch frying setup for your 32v i would go for a similar x 2 setup as vitesse is using. His stage III kit is making a lot of power and that would be x2 for you and the power band in a 2.5L motor is around 3400.

Even his stage 1 kit is making a lot of power.
A k26/7 hybrid would probably be more than enough for your app especially since the trans gives up so early. I contacted Majestic and they will build K26/7 hybrids for a reasonable price.

I was tight on space when I built my TT setup and I used twin WC t3's but did not have room for a T4 compressor side, so I had the guys bore out the compressor side and installed a 2 step bigger compressor wheel.

Dennis Wilson

Tammons,

380 at the crank at 1 bar is equal to 190 HP normally aspirated, which is on par with a chipped low compression 944 engine.

Dennis

Lance J

propane injection and water injection top of with a intercooler. should be safte to run 13psi

BC

Any links on propane? It would seem not so fun with the required large tanks ect.

m21sniper

Propane has actually been used with some success by some drag racers, but it is a heavy system because of the tank.

SMTCapeCod

Proprane is so banal:
http://www.cryofuzion.com/images/3000gt_eng.jpg

Just kidding. Try:
http://www.importpoweronline.com/cat...e8358137b74262

This is also gaining popularity:
http://www.snowperformance.net/products.asp?id=1