max. boost for cast pistons

speedwheel · Post by **speedwheel** » Tue Dec 25, 2001 5:02 pm

Hi guys!!! first of all i would like to great you all a merry christmas and a happy new year!!!!
Now for the question. I would like to know what is the maximum boost that you can set for a cast piston???

Thanks

vw505 · Post by **vw505** » Tue Dec 25, 2001 9:18 pm

not much!!!!!!!!

JohnConnolly · Post by **JohnConnolly** » Tue Dec 25, 2001 9:57 pm

I don't recommend it. When you find out, let us know!

John
Aircooled.net Inc.

speedwheel · Post by **speedwheel** » Tue Dec 25, 2001 10:38 pm

I've heard that AJ's 1600T uses the stock pistons??? anyone know if this is correct???
Stock pistons are cast right???

panel · Post by **panel** » Tue Dec 25, 2001 11:46 pm

I'm running around 5-6psi with stock pistons. I'll try 10lbs maybe soon on my 1600T 65 split window bus!

JohnConnolly · Post by **JohnConnolly** » Tue Dec 25, 2001 11:59 pm

AJ is using cast pistons. The fatigue and stress on an 85.5mm piston is vastly different than a 94 or 96mm piston (leverage, so to speak). We know the limit on a T-1 piston, your guess is as good as mine on a T-4 with cast pistons. I still recommend forged for the T-4.

john
Aircooled.Net Inc.

gert · Post by **gert** » Wed Dec 26, 2001 4:27 am

I use 2bar,that is about 28psi,boost on a 2l type 4 turbo engine.I have been racing this engine for 8 years and never had any problems with the pistons (KS).I use racing- fuel and water-methanol injection(boost injected).I use the car for 1/4 mile 12.2 sec and 1/2 mile 232kph racing.

Evill Ed · Post by **Evill Ed** » Wed Dec 26, 2001 7:37 am

I'm with Gert on this one. I run a 1.7L type 4 with Mahle cast pistons and 14-psi with water / aclohol injection for cooling. This is in a 914 that spends alot of time on the track. I have 2 seasons on this engine with no troubles. I just tore down the engine and inspected all of the internals. So far, no signs of stress or damage. No cylinder to head leaks either.

BTW- Corky Bell, turbo specialist, says that the thickness of the top ring land is an important factor for tubo engines. With the correct thickness, a cast piston is easily good for 1 bar.

Ed

JohnConnolly · Post by **JohnConnolly** » Wed Dec 26, 2001 9:24 am

Gert,

don't take this the wrong way (I'm trying to help), but if you are running 12.2s and 28psi, there is a MASSIVE restriction in your intake somewhere. Find it and unleash 150 more hp. You should have over 400hp with 28psi, which would put you in the 9s.

a barameter would help you find out where the pressure is backing up.

John
Aircooled.Net Inc.

JemMoses21 · Post by **JemMoses21** » Tue Jan 01, 2002 2:38 pm

How would that be done Mr. Connolly.

Jeremy

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Computer games don't affect kids, I mean, if pac man affected us as kids, we'd all be running around in darkened rooms, munching pills and listening to repetitive music.

JohnConnolly · Post by **JohnConnolly** » Tue Jan 01, 2002 4:02 pm

typically, you need to make a manometer. Plumb one end to the engine compartment, and the other end to where you are testing (in the intake). You need to measure the vacuum DIFFERENT from one side of something to another. for example, on many cars, the air horn on the air cleaner assy is responsible for around 7" of vacuum! Remove it, and you get a lot more power.

in your case, you need to get a boost gauge, a second one, and plumb it right next to the cylinders. do the gauges read the same? I'll bet they don't. I'll bet you are getting 10psi at the cylinders. so, you back it up getting further and further away from the cylinders until you get a big increase in pressure and THAT is the restriction. Your pressure and flow are backing up somewhere, it's not reaching the cylinders, you have to find out WHERE and you'll unleash a ton of power.

John
Aircooled.net Inc