Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Piston choice

Engine Building Fundamentals

Forum Posts



Tech Articles

Discussion and questions related to the course Engine Building Fundamentals

= Resolved threads


I’m building a 1993 240sx with a ka24de and going back and forth on the compression ratio for the pistons. I’ve spent a lot of time in the forums lately and trying to weigh out the benefits of higher vs lower compression. Stock compression is between 9-9.5 to 1 ( no good source to find out for sure 100% yet). My question is would it be more beneficial to try out a 10:1 piston or more a 9:1 or lower piston. My fuel choice is e85 permanently and my power goal is 400 to 600 whp range. This will be a turbo setup that will be daily driven so my main goals are for it to be responsive and have a good power band.

I think you should use a professional engine builder to reach those goals. They have the experience to select components they know work together. At least have them build and dyno a long-block. After you've had a pro build your engine, you can rebuild it yourself the next time.

I get what your saying and appreciate the input but Honestly I would rather make mistakes that cost me money vs having somebody build my car for me. I’m a automotive tech by trade and do short blocks at work but don’t touch anything high performance at work but want to do it as a hobby on my personal vehicle. I’m new to choosing engine parts but I’m just trying to learn as much as I can as I go through the process. I guess I was just looking for some input on if someone didn’t have experience with a particular engine if they would start off with a lil higher compression for the goals I had.

Your power goal range is too wild to give you the concrete answer. 400 whp is one story and 600 whp is completely different ball game. You would most likely easily make 400 whp with 10:1 compression ratio pistons on e85 but you might face some issues making 600 whp. 600 whp would require a bigger turbo that will make your car not that responsive for a daily driver. Smaller turbo will provide best response but making 600 whp can become a problem, in particular constant engine overheating even on e85 - unfortunately it is a downside of most old engine models working with high compression ratio and high boost from a small turbo.

I'm talking about Mustang dyno whp. Dyno jet type of dyno would be easier but still hard to avoid constant overheating 100 percent

Thank you for the feedback I’m really Leaning towards the 10 to 1 compression for better throttle response the combustion temperatures was just a worry when it came time to tuning it and being my first high performance engine build it’s nice getting feedback from people that got a little more experience in high-performance then I do. I would just hate to go a little higher in compression and regret it when it came time to tuning it. I will Definitely probably take your advice and stick to under 500 wheel horsepower though

10ish to 1 compression ratio for a daily car making up to 500 whp on e85 would be extremely responsive and comfortable to drive providing the proper camshats are choosen. I drove 2.2L engine with 9.5CR on pump gas with very small duration camshafts (256 intake and 260 exhaust) with gtx3071 turbo and the thing was absolutely pleasure to drive- the response was amazing, very elastic engine with constant acceleration all the way past redline 7000 rpm. The egnine was making around 450 hp at the crank.

Right on, thanks again for sharing your feedback and set up!

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?