Ok i just got my 98 spec from hmotorsonline and i decided to do a compression test to see the condition of the motor.. I did the complete swap into a 00 Civic and my results are Cylinder 1. 190 2. 180 3. 190 4. 190

The numbers are good because they are all within 10% of each other... But i looked in the service manual and its saying that it should be closer to 270psi in each cylinder ... why are my numbers so low?

 

My JDM B18C (sir-g) gave me 240psi of compression.

Now 270 psi with high compression pistons.

Cold or hot your compression test?

 

it was fully warm and stock compression of 11to1

 

Push the throttle open?

Mine was 260 across when you WOT it.

 

These numbers depend entirely on the gauge doing the test...

 

+1 this is a crucial step.

 

to be honest with you no its not.. the readings will be basically the same with throttle open or closed .. . but i did it both ways... im gonna go with the gauge and the atmospheric pressure and outside temperature causing low numbers ..
as long as they are well within each other i think its perfectly fine

 

how many times did you crank it? numbers do seem to be close enough to each other though.

 

i cranked each 5 times

 

mine was 220 in all 4 b18c5 2001 type r

 

this is my vote on the reason.

go run the 1/4 mile and see what mph you trap. it's a better judge of power

 

so what trap speed would you expect to see from a fully functional R? i'd like to investigate this theory with the numbers i got.

 

being that they are within 10% i would not worry. does the motor have camgears by any chance? it can affect the static comp from adjusting the overlap. is the o-ring on you comp tester good?

with oem cams my motor pulls around 290-300psi, with the pro2's, cam gears adjusted on dyno, only 245 psi.

my motor will drop about 30-40psi from 100% throttle and 0% throttle when doing a compression test. it does matter!

 

Yes it does matter!

 

pretty sure my B18C-R was 240psi across.

i would try to find another compression tester and give it another try. mine for example now reads about 60psi high lol had a PR3 piston LSVTEC peg it out at over 300psi. but anyway i wouldnt worry too much since they are all close.

 

Exactly.
Regardless of what that gauge is saying.
If the motor is running good and the numbers are close, it's good to go.

Unless you are trying to sell it?

 

the numbers were consistant, so I wouldn't worry.

 

these things are so weird. mine started reading low. i did a test on a 11:5-1 all motor SBC that makes a little over 420rwhp. said it had 130psi LOL

 

It very much does matter if the throttle is open or closed !!! You will get a much higher number with throttle open because more air is getting into the cylinder, yielding much higher pressure... You might not see much difference in variation, but this is the proper way to measure compression.

 

what about valve lash? I just did a compression test on my F20B that I just installed. Its similar to ITR as it has 11:1 compression ratio

I got

CYL 1 - 260
CYL 2 - 250
CYL 3 - 260
CYL 4 - 230

They are pretty much within 10% of eachother. I did wide open throttle on a fully warmed up engine (cooling fan came on atleast 2 times) and with all 4 plugs out. I also had ECU fuse pulled to stop fuel.

I have a loud valve tap coming from the valve cover. I suspect that after a valve adjustment, mainly CYL 4, I should see closer numbers.

Anyone else think valve lash plays a role in compression. If your valves are not opening and closing at the same timing, due to the valve lash being tight or loose, then air should escape the cylinder at different times.

 

so, what is the CORRECT number of times we should be turning the motor over?

 

You have to make sure that spark-plug-adapter fitting for the compression gauge is screwed in properly. If there is any leak where the gauge screws in then you will get lower numbers on whichever cylinder you don't have a good seal.

So:

the guage must be installed properly

The motor should be warmed up (Honda HELMS says this is when the cooling fan has turned on and off atleast twice)

All 4 plugs should be pulled out (this is so there is less resistance from the compression stroke of the other cylinders)

The throttle body should be held WOT (So air has an unrestricted path to the valves - cylinders)


You have 1 person crank the motor over (pull the ECU fuse from the under-HOOD fuse box. This will allow the motor to crank but the injectors won't spray fuel) and the other person watches the gauge. You will see the gauge bounce higher and higher and eventually it stops moving all together. Thats how I measure compression.

 

my 97 jdm itr motor only put 220 220 220 220, but it still ran like a champ and didn't smoke much from the tail pipe except for a tint of black at high rpm since it was tuned.

 

make sure you guys do take the above advice and disable the distributor or ecu. you can fry a coil doing this test if you let the plug wires hang.

 

Hey guys, did someone know what's the specs for compression test on a b18c sir-g! i will do mine in few days!
I heard about 240psi brand knew but i'm not sure can some one help me ?