NecronomiconJules

Hi all,

I'm considering buying a used WCM Ultralite (Lotus Seven-like car) that happens to run a F22C/AP2 engine.

Upon acquiring it 2.5 years/1,800 miles ago, the current owner did a compression and leakdown test that returned, respectively:
- 240 PSI on all 4
- 2.5% to 5%
I have seen the paperwork.

The PPI I ordered yesterday yielded:
- 230 PSI on all 4
- 6% to 7%
This is on an engine that - says seller - has 4k miles from new and has not seen AX or track days.
The PPI shop reports that it idles well, operating temp is a steady 190 degrees, it doesn't smoke/leak, looks bone dry and operates normally.

With zero mechanical experience, I would appreciate comments/thoughts on whether the slight loss is acceptable/can be attributed e.g. to instrument calibration/should raise questions/constitutes a red flag.

Thank you.
Eric

nissanfanatic

Different gauges and/or inflated original numbers. If it still runs well and you have been on point with maintenance, I would just check again in the future with the same gauges.

NecronomiconJules

Thanks Cory - interesting: the original measurements were done at a Honda dealership; yesterday's by an independent race shop.

So you're saying that the recent numbers are in spec given mileage? From what's available on the internet compression is generally reported higher (245+) on older engines - is that the normal course?

Eric

nissanfanatic

The shop isn't really going to make a difference unless they did the procedure differently.

This should help explain:
http://robrobinette.com/S2000Compression.htm

I think your results are fine as long as there isn't a large deviation on any one cylinder.

...

Your best bet would be to find someone local on the forums that is knowledgeable and learn how to do some of the more simple stuff yourself; it eliminates consistency issues. Buy a gauge on Amazon, hit up harbor freight for some tools, and I'd bet for $50 you can do your own compression tests from then on out, plus do other minor maintenance.

CoolGuy094

Comparing compression test numbers from different shops using different systems is like comparing dyno numbers from different shops using different dynos. The numbers sound great especially if they are that consistent. Sounds like a very nice motor and a blast of a car.

Slowcrash_101

New engines have 224psi compression, and leakdown less than 10% is acceptable.

NecronomiconJules

Thanks all - that confirms my tentative thoughts. Much appreciated.