Cylinder Compression Pressure (4g63t)

[XPaYaNtX]

Hello, I saw on my Haynes book that the standard cylinder compression pressure (at 250 to 400 rpm) should be at 164 psi per cylinder. I was wondering if a engine has 150 psi per cylinder is the engine in good condition?

Can someone explain what cylinder compression means? how will it affect the performance.

thanks
Charles

 

[Mr. Talon]

hey,

150 sounds good, how many miles on it? apart form just the numbers, how close they are to each other is also importnat, meaning the 150 for all 4 cylinders is just normal wear, as apposed to having one cylinder with signifacantly lower compression = problem.

as far as what compression is, its the pressure in the cylinder when the piston comes up on the 'compression' stroke. You want to have as close to pefect compression because this gives u the best effeciency/performance. say if ur cylinder could only hold 1/2 the compression it should, this means that 1/2 of ur air/fuel mixture is in the cylinder at the time of cumbustion, and tehre for 1/2 the power (roughly). low compression can be caused from bad valves, blown head gasket, worn piston rings, or a hole in the piston eek: )


hope that helps

trevor

 

[Defiant]

Compression is a measure of how well the rings, valves and gasket (where present- some motors [Offenhauser] don't have a separate head) seal against the decreasing volume and increasing pressure of the rising piston. Generally, if a bit of oil squirted into the chamber raises the compression, your rings are worn. If it doesn't, it tends to indicate valves or valve seats.

A leakdown is a more worthwhile test:

http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

And vacuum is excellent for diagnosing:

http://www.iwemalpg.com/Vacuum_gauge.htm

 

[xXeclipstasyXx]

As long as all of the cylinders are mostly near eachother, then your ok, thats just plain engine wear.... if one cylinder is significantly lower, than either your rings are shot, or your valves or valve guides are shot, usually its the guides before the valves....

 

[XPaYaNtX]

Okay Thanks the engine as 175000 km so that's about 110 000 milles, and YES the 4 cylinder as 150 psi each, and there's no oil leaking.

From what I hear this engine is a pretty good shape for the milles then?

Thanks
Charles

 

[xXeclipstasyXx]

110k on a 92, thats pretty good, my 97 already at 70k when i got it

 

[XPaYaNtX]

In fact the car is an talon awd tsi 90 that as 135 000 km on it.

here's the spec :
- 135 000km
- Leather
- Black Leather Shift knob Momo
- Radio cd Pioneer 50Wx4
- Original Exhaust with test pipe and high flow muffler
- K&N Filter
- 4 bolts transfer case
- Brand New (hankook K104)*4
- A-pillar gauge pod triple Lotek with a/f ratio, boost et egt. (Autometer and Westach)
- 4 KYB AGX Shocks
- Front polyuréthane Bushing
- Battery Optima (red top) relocated in the trunk
- New Synchros 1-2 and 2-3
- New 2G Original clutch kit with disk and bearing
- Bg Synchroshift in transmission
- Engine 6 bolts 175 000km ( 150psi on each cylinder.)
- Timing belt and Polleys (25 000km on it ~)
- Ball joints, tie rod end, Front sway bar link, Back Wheel bearings ( 25 000km on it ~)
- Back and front breaks (20 000km)
- New Slave and clutch master cylinder
- Front Driveaxles are Rebuilt with (5000km)

the only problem is that it need to be repeint.

hes asking 5000 CND $
it sound like a good buy for me...?


criminy, re-size that picture

 

[Cesar]

do you meam a 4 bolt rear end? I would give him no more than 3300CDN.
I know it's got a lot of maintenace work done to it, but cars devalue with age regardless of condition.

 

[XPaYaNtX]

4 bolt rear end... if that the (Différentiel en francais)

yeah I know what you mean... but at least some usual problems are already solve for a periode of time...
but yeah it high a bit...