Can a Timing belt effect compression?

k20toEVO · Jul 13, 2009, 11:42 PM

I have been doing alot of research and came upon a thread that is pretty close to mine.

I feel my car is losing power, or im just getting used to it hehe..

Has a borg warner s362 ETT turbo on it with a mynes top mount ( 10 pounds until I get a better tune but still faster than sock).

I ran a compression test and have

145, 155, 150, 145

The belt seems pretty loose, but im a ex honda guy where they are TIGHT so what do I know

Can cams effect compression also? cause I have kelford 272's

here is the guys post

"As some of you may remember, I was at one of Al's tuning sessions at Agile Automotive on the 20th of March. I had the black Evo with the boost issues followed by the weak power output. The compression check at Agile showed 150 in each cylinder. Standard for the Evo is 162, minimum is 138. Mitsubishi didn't see a problem because the car runs fine without any CEL's and it is not at or below their minimum. After the tuning session, I ordered cam gears, and as a secondary thought, a kevlar timing belt. The factory timing belt had some noticeable slack when we opened it up so we did a compression check after the install and the readings on 1 through 4 were 160, 162, 164, 162. I was at 22.5k miles when I switched belts. Mitsubishi reccomends replacement before 60k. I hope that this clears up my weak power problems and it looks like it should as the car is wanting more gas at WOT. I spoke with Al recently and he is looking at going back to Agile in the early part of June. A reflash should unlock a substantial amount of power that I have been missing.

Mods - If you feel that this should be in the Tech forum, please move the thread."

k20toEVO · Jul 14, 2009, 06:29 PM

18 views, no one?

kemoly · Jul 14, 2009, 07:47 PM

thats a very low compression!
i think you must run 170 max and 160 minimun
if i were you i will change my rings and also check the torq of the cams gear

kemoly · Jul 14, 2009, 07:47 PM

how is the oiil consume?

N1MR0D · Jul 14, 2009, 07:59 PM

I would suggest a leak down test instead of a compression test as they are more accurate and it will also let you know exactly where your problem is at. The test usually requires a leak down unit and an air compressor. If you don't have these, paid for it to be done by a shop you trust. It will atleast give you an idea of the problem you have to tackle.

k20toEVO · Jul 14, 2009, 11:55 PM

it doesnt burn and oil just alot of gas. lol i dont think it has had the timing belt changed and it has 80k. thats why im askin the question i am.. apparently this guy changed his timing belt and gained 10 to 15 more per cylinder?

smack_evo · Jul 15, 2009, 01:21 AM

the overlap of the cams can effect static compression tests. as stated above, a leakdown is much more telling. with compression you're really just looking for variation between the cylinders.
as far as picking up more pressure after the belt change, the original post also mentions gears. if they didn't set them straight up and just opened the cams up a deg or two that would cause less overlap and pick up a bit more compression.

kpr · Jul 30, 2009, 09:04 PM

As far as the slack in the belt, the belt in the 4G63 fits tight, if you have noticable slack maybe the tensioner is not properly adjusted or if you put too much pressure on it , it could be damaged. Remember if the tensioner is right you can slide a gaugepin through the holes .

Ted B · Aug 3, 2009, 02:23 PM

Quote:

Originally Posted by k20toEVO

Can cams effect compression also? cause I have kelford 272's

You better believe they can, and they will. As soon as one changes cams, he can throw the factory static compression test specs out the window. Increased overlap bleeds cylinder pressure right out the exhaust valve at slow engine speeds, especially as slow as cranking speed. This can cause a deceptively low reading. Pay no attention to that. So long as the cylinders are within a few percent of each other, you're probably ok.

dantegra · Aug 6, 2009, 01:47 PM

Your compression numbers are a bit low. Have a pro check it out.

Ted B · Aug 6, 2009, 04:35 PM

You don't know that, and you shouldn't say that. Low for a stock engine with stock cams, yes. As soon as the cams are swapped to something different, not necessarily. Large cams should be expected to reduce static cranking compression.