Comp ratio vs Compression test on 4g63t engines

[bazeng]

Hi All,
Just wondering what compression test results you guys get in relation to your compression ratio of your engine.

I know there are variables but just wanted a survey to see if there is any consistency with the results.

Post away.

 

[Jayz-1]

Cams will create the biggest variable.

 

[EVO-00X]

Geez everyones will be different Baz, depending how much wear the engine has. Do you have any cylinder more than 15% out?

 

[bazeng]

Mine are all even across the board. Just very low.
110 psi across the board.
I estimated the cr when I built it to be 8.8cr but am now thinning lower.

 

[4piknup]

Maybe measure compression ratio?
Use gear oil at tdc and fill to bottom of plug threads.
Repeat at bdc.

You will have to back off cams.
And remove oil with syringe and tube on end.
It gunna smoke a bit when you fire it up. Lol

Or run 50psi into it...

 

[bazeng]

Good idea Jack!

I think 50psi would be easier though... lol

 

[DOUGMO]

That does seem low baz. my old 2.3 was 9:1 and had 165 across the board.

My new engine is 8.4:1 but I haven't done a comp test on it.

 

[Advanced Jap]

Cams will create the biggest variable.

+1

 

[OLDIE]

That does seem low baz. my old 2.3 was 9:1 and had 165 across the board.

My new engine is 8.4:1 but I haven't done a comp test on it.

My 8.7 stroker pistons give 162-170 psi

 

[caged]

My 9.5:1 was around 190psi across all 4???

 

[EVO-00X]

Baz, my 8.5:1 CR was compression tested at 190psi across all 4 cylinders last week at Micks Motorsports.
Using Kelford TX272 cams. 0.054" headgasket (1.37mm). Engine only done 5,000kms.
Castrol Edge 10-60 FTW lol

 

[Dave_GSR1.8]

I know this is an old thread but if it helps I have 180 (dry) across all 4 cylinders (4g93T, no mods, done 50k since light overhaul).

 

[khubner1]

Mine (4g93t 8.5:1 (I think)) did 150 dry across all 4 but I suspect that the gauge because a much higher comp 2tr fe did the same. The gauge reading doesn't mean all to much what you want is consistency and little to no change between wet and dry

 

[OLDIE]

Can anyone explain how a wet comp test works seeing that all of our pistons are dished and the oil would pool there and not flow onto the bores like a NA motor.Are you allowing for the cranking speed to do this??

 

[khubner1]

Syringe with a large gauge tip (ink refil syringe works great.) extend the tip and slightly bend it make te piston botom dead center or close insert tip into bore and squirt onto cylinder wall oil will run down the bore pool in the piston to bore gap and coat the upper ring. For best results twist the syringe as you squirt to cover more cylinder wall

 

[trq-str]

[SIZE=10.5pt]9.1:1 CR 2L with stock cams [/SIZE]measured [SIZE=10.5pt]195psi [/SIZE]at 200k's and 190psi at 58,000k's. Both plus or minus a few psi.

Wiseco pistons and rings, .0035PTW
Hard run in with Penrite run in oil
Motul 15W50 every 5k after that