Hi guys I’ve done a compression test on my polo. 1.3 gk engine 1984 gl.

 

it’s got a gk cam in it and gn inlet,  exhaust and I ported/polished it on a rebuild a while back. It’s been running strong and fairly reliable since rebuild but I never did the bottom end.

 

Cyl1 - 80psi

cyl2 - 90

cyl3 - 90

cyl4 - 87

 

it’s pretty lumpy on idle but revs well otherwise.

 

what’re your thoughts? I think the compression is too low. I could do a bottom end rebuild but I don’t think I can take anything off the gasket etc because it’s already only just clearing. I had to bore out a little section on each cylinder to fit the new cam.

 

 

cheers

GK cam is not very wild. With high compression GK pistons too?

 

GK wear limit is 8 bar which is 116psi.

 

GL HB-Formel-E AAK AAU HK HZ MH NU NZ RC SC 2G 3F: 7 bar =101psi

 

HH HJ GT PY oldHB: 6 bar = 87psi.

 

Is that cold, dry test?

Do you trust the compression tester?

What does a wet test show?

 

Once I had honed and re-ringed my GK in 2014 I was seeing 15bar=217psi. 

Before was as low as 3.7bar=55psi but the CR tester was a shite Silverline and a borrowed Draper read about 7.3 bar=110psi best case.

 

Re-measured in 2018 (bar)

Cold dry 14.5 16 16 15.2

Cold wet 15.1 16 16 16

Warm 14 15.2 15 14

this was warm with closed throttle, it wasnt my tester just an ebay jobby from a friend so i cant retest for now. I may get a good tester and try again but im not feeling too concerned as the car drives pretty well, definitely not like its got badly low compression anyway. but who knows....

How  did you do your compression tests, engine warm or cold?

 

As already mentioned, are you also using a good quality compression tester with a known good accurate gauge? 

 

A wet test following a dry one will likely tell you the state of the bottom end.

 

How I do mine:

 

Ideally, engine cold, throttle fully open, battery fully charged.

 

Dry test: crank each cylinder until gauge reaches a maximum.

 

Wet Test: squirt of engine oil thru spark plug hole, crank until gauge reaches maximum.

 

If you get a large increase in the wet test results then it’ll be wear in the bottom end, pistons/rings/bores

Edited 15 April, 20215 yr by mk2tastic

Thanks a lot for that info, I’ll buy a tester  and get in the know.

 

can u elaborate a bit more on the wet test.. how much oil is a squirt? I have 1 bottle of engine oil I carry around so what shall I do with that, pour a bit in out the cap?

 

 

Would anyone be interested in a build thread of my car? I’ve done a ton of (‘innovative’, atleast I havnt seen much of it before) development work with bump steer and some things with the handling and also the engine. I work on it most days and have a workshop to make weird diy parts but the car is remarkably different to drive than in stock form. 
 

I’m just interested to share and have a good discussion and learn more. 

53 minutes ago, Bevlesskeg said:

Thanks a lot for that info, I’ll buy a tester  and get in the know.

 

can u elaborate a bit more on the wet test.. how much oil is a squirt? I have 1 bottle of engine oil I carry around so what shall I do with that, pour a bit in out the cap?

 

 

A squirt as in from an oil can, which is what I use.
 

It’ll only be few ML, so yes I suppose a small amount using the cap of your oil bottle to measure would suffice, anymore and it’ll smoke like you’ve put diesel in it, once you restart the engine🙂

 

 

Flexible tube on a small can ( or tube on end of a tiny funnel) or it's too easy to miss the sparkplug hole when pouring.

I do it with clutch and gas pedal pressed to floor just so it spins i a bit faster

 

I find 6or7 revolutions enough to reach max. And i disable the electric fuel pump and ignition if 3 other plugs are fitted. Suppose you could clamp a mechanical pump's inlet pipe.

 

 

Edited 15 April, 20215 yr by dvderlm

the engine is like a pump , the throttle needs to be wide open 

 

warm engine will give a higher reading than a cold one