Did a compression test tonight.

Onefast99gsx · 03-22-2006

Well I bought my own Compression gauge tonight at Checker. I ran the car for approximately 8 minutes to warm it up. I held the throttle plate open during the compression test. I cranked engine over for approximately 6 rotations each hole.

Results:

#1 158
#2 155
#3 155
#4 161

This is with the stock 2g motor, 93k miles. The only internal modifications are the HKS 272 cams.

Taken that all into consideration. How do my numbers look guys?

Thanks.

xveganxcowboyx · 03-22-2006

Looks good to me. I believe you'd expect numbers a little lower than stock with those cams and they are all in close range.

**scheides** · 03-22-2006

Looks good! Nice and even, and well within spec. Checked for crankwalk lately?

Onefast99gsx · 03-22-2006

Thanks guys. I checked for crankwalk last winter when I was building the car up. I couldn't really get the dial indicator to move. I did it per the vfaq instructions. I would of had to pry hard enough to bust the crank pulley in order to get the indicator needle to move. Wasn't crankwalk fixed for all 1999 cars?

slowbubblecar · 03-22-2006

Looks pretty good. I just posted about it on the dsmlink forum.
James

Onefast99gsx · 03-22-2006

Thanks much for doing that. I had no suspicions to warrant a test. I just wanted to make sure the car is 100% before she makes a trip to Rock Falls to run my first 11 sec.

**Kracka** · 03-23-2006

Unless the cams affect it, aren't those a bit low for a 2G? Those numbers would be good for a 1G.

tim · 03-23-2006

Quote:

Originally Posted by S2kracka

Unless the cams affect it, aren't those a bit low for a 2G? Those numbers would be good for a 1G.

Why would the cams affect it in a negative way? Wouldnt the extra lift and duration allow more air in for higher compression results?

Not saying you said the cams would affect it but since you refered to it as being a possibility I was kind of curious.

Super Bleeder!! · 03-23-2006

cams are not going to effect your static compression. dynamic though, is another thing entirely.

At-Least-It's-An-Evo · 03-23-2006

Those numbers are good enough. Turn the boost up!

**1ViciousGSX** · 03-23-2006

Quote:

Originally Posted by tim

Why would the cams affect it in a negative way? Wouldnt the extra lift and duration allow more air in for higher compression results?

Not saying you said the cams would affect it but since you refered to it as being a possibility I was kind of curious.

Late closing of the intake valves will reduce compression at cranking speeds.

tim · 03-23-2006

Yeah, I was thinking about that a little more last night after I posted. I would think though that the late closing of the valve would be offset by the extra lift and it wouldnt really affect compression much.

Maybe not, it just seems to make sense to me.

CDeutsch · 03-23-2006

I did a compression test before and after changing cams. My numbers were 10-20psi lower with Crower Stage IIs.

**1ViciousGSX** · 03-23-2006

Quote:

Originally Posted by tim

Yeah, I was thinking about that a little more last night after I posted. I would think though that the late closing of the valve would be offset by the extra lift and it wouldnt really affect compression much.

Maybe not, it just seems to make sense to me.

At cranking speeds, lift has no real effect. The air flow is way too slow for lift, duration or port velocities to make a difference. It's only mechanical closing of the valve in relation to the piston's travel that will change compression at this point.

tim · 03-23-2006

That makes sense too, thanks.

Onefast99gsx · 03-23-2006

Makes sense to me too. Thanks for that additional input on this subject.

joesushi · 03-25-2006

Quote:

Originally Posted by CDeutsch

I did a compression test before and after changing cams. My numbers were 10-20psi lower with Crower Stage IIs.

Hey Chris! I recently just had a head put together by a friends shop. It's got used valves but all checked out ok, crower II's, titanium retainers, and upgraded springs. How did the crower's perform for you?

PS sold that galant yet?

CDeutsch · 03-26-2006

Quote:

Originally Posted by joesushi

Hey Chris! I recently just had a head put together by a friends shop. It's got used valves but all checked out ok, crower II's, titanium retainers, and upgraded springs. How did the crower's perform for you?

PS sold that galant yet?

They're better then stock. I probably should have them degreed to maximize performance.

Still have the galant, someone is looking at it today.