I am not a mechanical guru and I cannot really explain this. The first test I mentioned was done immediately after the car was pulled off the dyno with the engine hot. The second was done after the cam gears and kevlar timing belt install were completed - cold engine. I also has a Mitsu tech check the compression a week before the install to independently verify that the compression was still low and to rule out poor calibration as the cause of the low readings. The Mitsu tech got almost identical readings as the day it was on the dyno.

I think this addresses Shiv's points too.

If this cause seems improbable, please tell me. The solution seemed to be the replacement of the timing belt. The compression came up along with the power of the engine. The belt replacement hapened 20k miles ago and the car is still strong and running great.

 

No, please respond to the compression issue. If there are flaws, then please take some time to educate and enlighten those of us that don't understand.

 

I am not trying to be a smart ***...but your post makes no sense

Gauge calibration over a few months or even a different gauge altogether could have and probably was used...this is what I think was the reason you saw a difference in the results

There is a hydrualic tensioner to regulate tension... old belt or new, Kevlar or stock...If both belts were installed correctly there should have been no difference in tension....If the new one is tighter..then it will fail earlier.

As stated before if a toothed belt stretches the pitch of the teeth must change...this does not occur...

 

Thank you for your reply. The gauge calibration issue did concern me and that is why I had Mitsu check it with their gauge prior to the install. Their readings were almost identical to the readings from the day the car was dynoed. The third time it was checked was right after the install. This was done with a third and different gauge. This time the compression was higher.

I have not checked it again largely in part to the advice I had received from the people I asked about the problem and the difference in tension between the two belts. Also, as I stated, we held the two belts up to each other and the stock belt was slightly longer. All of these factors led me to believe that the problem was with the stock belt. I have put 20k miles on the car since the install without any problems.

I really wouldn't have posted here if I didn't feel that this actually happened. I do not have the sound mechanical background to debate the causes of this problem on any level. I am trying to learn as much as I can and being humble is a good part of that. I appreciate the time you took to give me an honest, informed reply.

 

Andrew, et al,

Just out of curiosity, would the compression change if the cams were retarded/advanced from their stock settings?

l8r)

 

Ludikraut -
Not likely, unless one were to change the cam timing 40 or 50 degrees, which, of course, is not a reasonable idea at all. A couple of degrees - no way that changes compression.

 

Nope....the event of the intake/ exhaust valve as far as time is concerned is altered but regardless of this adjustment both valves still need to close tight at the same time on the comression stroke otherwise you would not have compression as it would all leak out of either valve....
A compression gauge has a one way valve that holds pressure within the gauge