Black51

I remember reading your thread on that. I was referring to guys who are worried about blowing a HG at 20 psi, or just worried in general of blowing up the motor. I understand someone running 20psi with a sock turbo/exhaust is gonna be more detrimental on the engine than someone running the same boost pressure, with a bigger turbo/exahaust and therefore lower back pressure.

So factor out back pressure being an issue for now. I'm just curious to know what the stink about running higher boost is, I'm not making a stink, just curious about the stink.

Black51

And are you telling me an apple isn't an apple? 20psi of air in the intake is 20 psi in the intake. I was just referring that to different types of fuel being burned is all. Whether you run an engine at 20psi, burning E85, or an engine at 20psi, burning 87 octane, there is still 20psi of air going into the intake...?? Otherwise I need to take a physics class.

Rogue_Ant

Boost is really more of a measure of restriction...
As Sid mentinoned earlier, a poor flowing setup at 20psi does not equal a good flowing setup at 20psi.

Black51

At any rate, my point is being missed. I was asking why guys don't like running high boost in these cars, yet it's ok to run 20-30psi through an Evo or something of the like.

Back on topic now...

schip43

Start a thread, I asked something similar in my 16v /2.5 thread. Our motor is 500cc's bigger than the 2.0 but it doesn't seem to make a difference on paper anyway.

theedge

Modern engine, modern cylinder head, 16 valves, etc etc.

carlege

modern spark and fuel delivery system.

Chris White

Its pretty simple – 20psi @ 90f (an apple) and 20psi @ 250f (an apple flambé) are not the same.

You can run 20psi on a 944, even with a K26/6, just fine if you have tuned it for the right fuel/spark and just for brief periods. As soon as you mention the word ‘track’ it’s a completely different story.

The problem is heat. All sorts of heat. Not just coolant heat (that’s easy enough to deal with) but intake heat and oil heat. The intake heat is the killer for most 944 turbos. If you have a well-chosen turbo for street use it will not be at peak efficiency at 6k rpm and full load, and when turbos are outside of their peak efficiency they generate heat in the intake charge…and lots of it. Not unusual to see compressor outputs over 300f. the intercooler can deal with this for a while – but at track power level demands it will heat soak and the intake temps will climb until you get to detonation….and that’s bad.

So why do Evos not have this problem? Several reasons – the combustion chamber is less prone to detonation, the engine management is more modern/precise and the most important reason is that the typical Evo owner selects a turbo that is in its peak efficiency at very high boost levels – what we in the 951 world would normal call a dyno queen turbo! Not nice for the street unless you are a ‘boy racer’ that needs to hit 7500rpm in the grocery store parking lot.

BTW – here are some pictures of a ‘Hot’ Evo from last Monday at Watkins Glen – the only engine failure at an event with 170 cars.

The last picture is a butt ugly Mercedes – this one is uglier in person…..jut my opinion!

docwyte

My car can deliver all of your goals, but it's a 5.7 liter, not a 2.5 liter...

thingo

But it's not a porsche is it?

docwyte

Really? Badge on the hood coulda fooled me, cause it says "Porsche".

User 52121

I'd consider it more of a "Chevy in drag"

docwyte

I consider it more fixing all that ailed it from the factory.

Wouldn't have gone this way except the motor failed, but once it did, it clearly was the best option for me and how I use the car. Financially too...

schip43

Well yeah there is that!

schip43

Oh Snap!

Yeah but.. I wouldn't throw it out off my garage!