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-   -   Compression test results (https://www.rx7club.com/3rd-generation-specific-1993-2002-16/compression-test-results-680438/)

st4rk 08-16-07 05:36 PM

Compression test results
 
86000 miles on stock 13b (never opened).

Quoted from the paper:

"One is 6.3 # 6.4 #3 6.5 Compression at 2 75 # 5.7 #2 6.0 #3 6.0"

Is this good, bad?

Thanks.

WanKeL FD RX-7 08-16-07 05:39 PM

its not really good, you gotta start saving money for a rebuild pretty soon. good luck.

GoodfellaFD3S 08-16-07 06:08 PM

With that mileage, that's about what I would have expected, maybe a little bit lower. The #s are fairly even, which is a plus. I wouldnt recommend pushing the engine, as far as more power or boost. If you want it rebuilt I know where you can bring it ;)

st4rk 08-16-07 07:15 PM

Thought so, what are normal numbers it should be getting if it's a healthy engine?

fendamonky 08-17-07 08:14 AM

8.0 across the board is damn near perfect.

DaveW 08-17-07 08:26 AM


Originally Posted by st4rk (Post 7243622)
Thought so, what are normal numbers it should be getting if it's a healthy engine?

Factory recommended minimum: 6.0.

As long as it's running and starting OK, it's probably going to last a while yet (10-20K miles) if you use it conservatively (no race events, or long runs at full throttle). However, as Rich said, don't add more boost or HP.

t-von 08-17-07 02:15 PM


Originally Posted by st4rk (Post 7243251)
86000 miles on stock 13b (never opened).

Quoted from the paper:

"One is 6.3 # 6.4 #3 6.5 Compression at 2 75 # 5.7 #2 6.0 #3 6.0"

Is this good, bad?

Thanks.



My engine had higher compression numbers than that and it had over 100k on it. Given your even numbers, all you need is a good carbon cleaning to furthur free up those seals.

By the way, my engine blew due to over boosting while running a lower octane. This had nothing to do with age or mileage. Hell I was even fully boosting with 87 octane at that mileage all the time, up untill a really cold day when I forgot to back my boost down. It spiked to 13psi so my engine called it quits. LOL Ooops my fault!

MrNizzles 08-17-07 02:51 PM

I had an engine that scored 5.8, 6.0 and 5.9 on the rear rotor and the engine blew up 3 days after I drove it home ... never went over 75mph, so I would be VERY VERY careful.

It was smoking on startup too, but if your's isn't, then maybe it's not that bad, but still, expect to rebuild soon.

DaveW 08-17-07 03:11 PM


Originally Posted by MrNizzles (Post 7246230)
I had an engine that scored 5.8, 6.0 and 5.9 on the rear rotor and the engine blew up 3 days after I drove it home ... never went over 75mph, so I would be VERY VERY careful.

It was smoking on startup too, but if your's isn't, then maybe it's not that bad, but still, expect to rebuild soon.


You may be right, but "blowing up" is not necessarily a result of low compression. It could have been caused by detonation due to a tank of low-octane gas in combination with a cool night, etc.

Obviously, low compression isn't the greatest thing to have, but I wouldn't panic over it. There are certainly a lot of 60-120K-mile FD engines around still running well with low compression #'s, and because they are still running well, and haven't been checked for compression, the owners don't know their compression is "low."

sr4rk, just be careful with getting good gas (I use only Sunoco 94-octane), and enjoy it.

RotaryResurrection 08-18-07 01:55 AM

Engines that get weak like this can last for another couple of years, or a couple of days. NA rotaries can usually hold off until they dip into the mid/low 80psi range, but turbo rotaries have a way of turning 95psi or less into zero quite quickly.

I would not bother with any band aids...just continue to drive it without raising hell, and save for future plans/mods/rebuild/swap.


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