txturbogs

I checked the compression today and according to the shop these were the numbers:

Rear rotor : 7.1, 7.1, 7.1
Front rotor : 7.0, 7.1, 7.0

SO far the compression is good, now I need to know if the coolant seals are ok. What other test can I perform to determine the engine's health. BTW, the engine had abuot 10k to 20k miles, it was a japanesse motor, and now I managed to put around 3k. Thanks

XSTransAm

sounds low to me

was the engine cold?

sevensheaven

iTrader: (1)

These aren't good numbers, check some threads for proper compression and how to check it your self.

Terry

Badmfer

iTrader: (4)

ive done a search on this topic and from what i found out compression numbers are higher cold then warm.

Enconsiderate

those numbers arent really that bad. while yes, they are not perfect they are consistent. i would just start saving for a rebuild. you know that engine will go soon enough.

txturbogs

By the newbie site, I thought anything above 6 was good. This is kg/cm2. Hmmm, are you sure the numbers aren't ok?

RX7Wishing

7.0's are marginal at best.

fd3s_rx7

iTrader: (13)

at least they are consistent.

t-von

iTrader: (8)

Just because the compression is low doesn't mean that the engine is on it's last leg (especially if it only has 10k to 20k miles). Used rotary engines (like what txturbogs has)will most likely have carbon build-up issues from sitting up so long. This build-up will give off inaccuarate compression readings due to stuck seals.


txturbogs, If I were you I would do the water vacuum hose/carbon cleaning method described here:

https://www.rx7club.com/showthread.p...um+hose+carbon


With the engine free of carbon you will now get a better reading of your engines true health.

HeffBoost

7.1kg/cm2 = 100psi Those are good numbers and the consistency between faces is good as well.

txturbogs

Thanks for the replies, I feel better now. Thanks to you t-von, I will do that and do another compression test.

Enconsiderate

what kind of carbon build up can there be if the motor only has 10-20k. like i said those numbers arent that bad. you should only really worry if the numbers are not consistent.

t-von

iTrader: (8)

Trust me it doesn't take long for carbon to form in a rotary especially if the car was babied around. Example I was sitting in line to get my car washed at a local lazor wash. After 15min of idleing, I finally got through to wash my car. The wash itself took 5 mins. Thats 20mins of idleing. When I left the wash, I began to accelerate onto the interstate and sure enough you could see a crap load of black smoke exit out the exhaust. My car is stock and never smokes. Because rotarys are thermaly inefficiant when compared to pistons, they don't burn the fuel/air mixture properly which will leave carbon deposits behind. Thats why they need to be reved every now and then.