Hi all,

Now that I am gathering parts for my Rotrex build, I have a variety of brands for selecting low compression pistons. Considering I won't be getting past 20psi, what piston brand would you recommend? Here are some more info:

My car will not see any drag racing or drifting, just some occasional WOT runs. Moreover, a Rotrex builds boost gradually so, 20psi would be the absolute maximum at redline. Given these facts, I think that mammoth strength is not a first priority (like for instance the Arias Extreme) but things like reliability, longevity, minimal cylinder bore wear and as less incidents of defective batches as possible...

For what I know, Wiseco, CP, Cosworth and Arias are among the brands I can choose from. What is your experience?

 

Weisco stock compression.

 

Taywan has cosworth stock compression Pistons with low miles he's looking to sell.

 

Do you consider that 10.3:1 compression (this is stock compression if my memory serves me well) for 20psi is ok? Even when considering proper ignition tuning and safe fuel mixtures (11.0-11.5), won't detonation still be a problem?

 

By the way, from a quick search I found out that Cosworth is offering 8.8:1 and 11:1 compression ratio pistons. If anyone could provide me with a link with other compression ratio Cosworth piston options (besides Amazon), I would be grateful...

 

What fuel you using? That has more to do with the comprssion than anything. Im running 11:1 on 91 oct but only 11-12 psi. When I switch to E85 ill run as much boost as I can get out of the procharger.

 

I'm running 11:1 Pistons and making 20psi with my vortech. More about proper tuning than compression causing detonation. Go with higher compression and get better response and more power off boost or at lower rpm

 

This^

The other side of this equation is heat soak. If you dont plan on continuously beat on the car for long periods of time, say at a track, then you can get away with running higher compression. Another alternative is to run something such as meth to keep things cool. All up to you and what you are willing to spend and what you want to do with the car, I do agree with whats been said before though, Weisco stock compression would be a good look probably.

 

FWIW Dynosty recommended 8.5:1 for my build based on a requirement that I wanted to be able to run pump gas and E85. The off boost response is not that much poorer with a lower compression ratio - just a few percent less hp. I believe the difference between 8.5:1 vs 11:1 will be 5-7% difference in peak hp. Reducing potential for knock at high boost easily outweighs the small % gain in compression. Adding 1 psi of boost, gives you 5% right back... Add in 2 psi and you've exceeded whatever you would've lost with lower compression. So if you've got spare boost, I'd recommend a nice safe compression ratio.

 

Oil cooler!

 

one part of the answer...

 

^a step in the right direction

 

With Turbos that works great because boost is all in by 3500rpm or so, but with a Supercharger full boost is at redline. So stock CR or evn 11:1 works well.

 

^ good point