Piper cams and Boost...

TFD

Hi people,

I'm thinking about putting cams in my turbocharged Z22SE. Now the Piper cams look good specwise (I want more duration to get some more top) but the question is how these N/A cams perform under boost. How is the overlap with these cams? (less overlap seems better so you wont loose to much boost/air because it's presurised now).

Any thoughts/experience?

Thanx

TFD

Got myself some information. Calculated overlap is 46 degrees which is more than the Comp turbo cams at 20 degrees overlap.

vocky

thats the problem with turbo, you do not need too much overlap

TFD

Indeed. I'm still confused on the stock cams..
They are 244/244 duration and according to MarkV they have a 113.4 degree LSA. This would result in an overlap of 17.2 degrees.... That seems very low for a N/A cam and I think it's not correct. Can't find any other information from the stock cams to calculate overlap though.

You got additional info Vocky?

TFD

Answered my own question again (like to get to the bottom of things)
116 degree intake valve timing + 108 exhaust valve timing = 224 / 2 = 112 degrees LSA
This gives a 20 degree overlap with 244/244 duration stock L61 cams.

20 degrees sounds nice (same as Comp turbo's), so no need for timing the cams. Justy get other cams for more lift.

vocky

Piper regrinds might be the answer, they grind 1mm off the base lobe

TFD

According to their specs they have 46 degrees overlap, which is 26 degrees more then stock or Comp Turbo cams...
The Piper ones should work on a BIG turbo car with a big exhausthousing to minimise the backpressure. My T25G turbo is way to small for that kind of overlap..

In my nissan time they used JWT S3 cams with these T25 turbo's with very good result. Those cams are 31 degree overlap with 11mm lift and 260/260 duration.

So, for my application it would be comp turbo cams right now.

evocarlos

108* dont sound right...
2006my l61 103*

TFD

That's interesting cause the GM buildbook says 108 degrees ... 🙁

With 103 exhaust timing the LSA would be 109,5 degrees resulting in 25 degrees overlap.