The reason I ask is that I have done compression tests on my 99 GSR motor on at least three different occasions and when it ISN'T blown it shows around 150 psi in all 4 cylinders..., is that abnormally low for a GSR which is internally stock?

 

had mine done last week and it read 200, 200, 208, and 210. But mine is a 2000 GSR and i've only been running 8psi for about three months.

 

180-220. In that range

 

how many times did you crank for your tests. I always stop at 5 cranks.

 

my stock was 210's, with 9.8: CR is 200.

i stopped when the needle stopped moving

stan

 

Should be over 200psi in all cylinders...

 

before the snail was put on, i tested it and it had about 190. 95 with about 90K on motor.

yours seems kind of low. did you step on the gas pedal all the down while turning the ign key?

 

gas pedal down. 99 GSR with only 28000 miles

 

I guess this leads to the question, Why? What causes a motor to have such low compression when it is internally stock... I know my altitude has a little to do with it , but not 50-60 psi worth.

 

What elevation are you at?

Is the motor warm?
Did you disconnect the injectors/pull the ecu fuse? (you don't want fuel in the cylinders)

Crank it until the needle stops moving. Compression testers are "peak pressure" gauges.

Dustin

 

where about is the injector fuse ?
is it under the bonnet inside the black box near the battery ?

 

in the black box by the battery, it is the 15amp fuse, looking from the front of the vehicle, it's the top left corner fuse

you can disconnect the distributor harness as well

 

 

I had 180(+-5) but my motor was built 1,500 miles ago too. And it has 9.0:1 pistons in it. Those numbers seem really low. Try adjusting your valves, i think that improves your numbers. I think... A warm car also improves your numbers.

 

I'll try the valve adjustment. It was at normal temp every time I tested it.

 

the only 15amp fuse i have is only for the ECU

oh btw this is for jdm itr

 

whoah 180ish with 9:1 pistons , my damn jdm b18c (1) with 10.6:1 only have bout 190ish , must be almost blow up

 

Can anyone confirm whether or not a valve adjustment can makea difference in the numbers ?

 

Nope.

 

Not that I'm sure it helps, but my B18C w/ USDM ITR pistons runs about 260 all the way accross.

 

Mine was 230 psi across the board. Throttle open and warm. 102k on the odometer.

 

I think the variances between peoples cars have alot to do with the different compression testors.

 

yes, different compression testers are not all created =

 

A vavlve adjustment can through off a compression test. If they are too tight then the valves won't seat all the way and compression will be low. You could also do a leakdown test to see where the pressure's going.

 

only if your valves are staying completely open