I have a 94 GSR sedan. It has 125,600 miles on it.

I have taken Numerous trips to redline and was very concerned that I had perhaps damaged my engine.
It had always idled a bit noisy and now seemed to be consuming a bit more oil.

I was also wondering about going turbo... http://www.c-speedracing.com/howto/c.../comptest.html
Used that link to convince myself how easy it was to do a compression test - it was!

The real surprise -
from right to left
(as if standing in front of the engine like you normally would )
Right cylinder was 210 / 205 / 200 / and 205 for the left cylinder (nearest the distributor).
I did this twice to make sure.

Now - are these unusually high?
Could I have done this test wrong?
I kept cranking the engine with the key until the needle on the compression tester stopped - about 6 cranks

That is what the comp test tool instructions said to do.
The only thing I did not do is open the throttle plate all the way - the online instructions did not say to do this.

Could the tool be out of calibration?
It is brand new craftsmen brand.

I am getting 27-30 MPG

Your feedback is much appreciated.

 

sounds like a health motor, consumption a very little oil at high rpm is also noraml,
as far as your compression test its fine, does seem to be low so you're okay
my old b16a used to have 215psi all across, my new d15b 200psi all across

 

You DO need to have the throttle wide open to perform this test correctly.

 

The online instructions did not say to have the throttle plate open but the tool instructions said to...
I did not have the throttle plate open at all.

How does not having the throttle plate open affect the readings?

Would the readings be too high or too low?

Thanks for any help


[Modified by joeg26er, 10:56 AM 2/2/2002]

 

you have to open the throttle to help get air into the motor

 

i suggest redoing the test with the throttle open.

 

well, actually it says to press the pedal all the way down when u do the test. But like they say 200 psi is good for a b18c. If you do it over with the throtle plate open it will only go up like 10 psi or so, so it will only help u. Also on a side note i have a haynes repair manual, and it says that a b18c1 and b18c5 has a standard 270psi???? WTF? I think they made a mistake, because i also have 200 on all cylinders. can someone check in their repair manual too see if it says diffirent. thanx
manny

 

Well,
I just redid the test with the throttle plate wide open.

I got different numbers this time.

I cranked the engine over with the ignition about 7-8 times.
This is how many times it took until the comp tool would not go up any more.
Was this the correct way? This is the way the tool instructions said to do it.

From right to left (timing belt to distributor side)
206/200/204/205
Same numbers came up twice.

I did it both times with a well warmed up engine.
This time I waited about 1/2 hour before doing the test.

Can I do a leakdown test myself? Does anyone have a link to an online article?

Do you think my engine is good to go turbo?
What is the max psi to run on stock block of this age?
Or should I just buy a used 911?


[Modified by joeg26er, 11:13 PM 2/2/2002]

 

your compression readings look good.. yes, they are a slight bit on the high side, but your methods and/or readings may be inaccurate..

 

High b/c of carbon build up maybe....

Sound real healthy.

 

Yes, Pb is correct.

Remember carbon buildup will give higher compression readings. Engine does not stay squeaky clean in there. Carbon deposit buildup is natural. It wont really build up to dangerous levels, it stays as a layer ..unless something serious is wrong with your engine. Also, you should consider carbon buildup when grinding out material off the head (porting), and when choosing your compression ratio.

You can experience more detonation as the engine gets more miles. If you chose too high of a compression ratio, you might not be able to run on Premium pump gas later on ...gotta keep buying octane booster$ .

 

Also, my compression test readings where also high. @174,000 miles....

195 190 185 195

For some reason, on most engines.. one of the middle cylinders goes bad first.
It has to do with the coolant and oil ducting within the engine.

 

can someone please confirm my books mistake??? thanx

 

270 is the max you should see. I have yet to see a C1 or C5 do that with stock setup. Remember, with a compression test, you are not looking for high number as much as you are looking for numbers to be close...


Jason

 

oic, thanx...so 200 psi is good for a b18c1?

 

FSTASNTZ, wow ur the first person that knows a thing or 2 about cars on all these compression test fourms.
heh u guys crack me up worring about how high ur compression is, when its way more important to look for consistancy's.
ur GSR can compression test at 50 and still be drivable
as long as it was 50 across the board.
it'd feel slow as hell, but it would be drivable

 

I'll back up Jason on this one, the real thing that matters for this is that the numbers are close to each other and that they are in an ok range. The numbers don't really matter unless they are really low, the real key is variance between the cylenders....you guys both look to have good healthy motors

 

thanx ....the only resaon i am worried about my compression being high enough is because i ran a 15.0 with my crx. With the gsr motor it should at least be low 14's. So i started to see if it was my compression that was the problem or not. And now i see its not, so i hope u understand my situation a bit better.
manny