Compression

[265bhp gtir]

Hi can anyone tell me how much compression a good engine should have as i did a compression tess the other day and i had about 68psi on all 4. Iv just bin on ebay and seen an engine and the seller is saying the engine has 165psi

 

[Cambridge_pulsar]

If you've done it right and the results are accurate i'd get your wallet out, think about 140 is ok but much less and you should be worried. You could look on the bright side in that you got similar results for all 4...

 

[265bhp gtir]

What sort of compression would it have it was a low compression engine

 

[Rishi]

You are looking at something between 135 - 165 in general but you can of course build to higher compression as i have.

Key thing here is that the compession across the cylinders should not vary by more than 5psi


Rishi

 

[265bhp gtir]

So iv got very low compression then. Any ideas how much a rebuild will cost

 

[Rishi]

Check it again. Was the engine warm or morning cold when you did the test?

Rishi

 

[265bhp gtir]

It was warm. I will check it agen tomorro. Whens the best time to check when it cold or hot.

 

[pulsarboby]

thats my engine im flogging:-D

anything less than 140psi aint good, if all 4 cylinders are the same or there abouts thats what your aiming for, if ones down then you have probs!

but that reading you got is ridiculously low, make sure you crank engine for say 5 seconds per cylinder with the throttle wide open, then you will get a true result. mine was barely warm when i checked them, so if i checked ahen hot it may be 2 or 3 psi higher.

if that is your true reading, then you have a majorly worn engine;-)

 

[265bhp gtir]

How much are you looking for that engine.

 

[pulsarboby]

will accept £800 for the engine, and i wont budge on that price either! as it is a real good one

 

[GTi-R23]

I'm guessing you've read the gauge wrong or done the test wrong, to have that same very low reading in all 4 cylinders seems strange, surprised she'll fire up at all.

 

[stumo]

Did you have the throttle pedal all the way down when doing the test?

 

[265bhp gtir]

Iv tested it again today and im getting about 95 on all 4 that was with abit of oil in the bores. It sill starts up fine and pulls fine. On top of the piston it ses 54c is this a standard piston.

 

[Rishi]

54C is a standard piston


Rishi

 

[MarkTurbo]

Did you have the throttle pedal all the way down when doing the test?

I know thats what everyone says your meant to do but it dosent make any difference ;-)

 

[265bhp gtir]

With my compression beening so low will this cause the car to some times feal a bit flat and some times feal fine or could this be a problem with my maf . And has any 1 got a cheep block for sale.

 

[oap-r]

With my compression beening so low will this cause the car to some times feal a bit flat and some times feal fine or could this be a problem with my maf . And has any 1 got a cheep block for sale.

With compression that low it's surprising that you can even get the engine started never mind actual drive it :shock:

Speak to thunderpants (Odin) although that tight fisted sheep shagger doesn't give anything away cheap ;-) :lol: :lol:

 

[pulsarboby]

why do you want another block?
rip the lump out and get your block rebored with a new set of pistons and rings, job done!

 

[265bhp gtir]

It still runs at the moment and if i get a block i can do it bit by bit because im skint.

 

[Fast Guy]

Do the test again with the engine hot and the throttle floored. Not much air is going to get in the chambers with the throttle closed.
If your engine is starting and driving fine it suggests your comp test may not be right.

With compression that low, your car should be well under performing or smoking like buggery and maybe blowing the dipstick out.