[Mk2] [Turbo] Compression test results

[JP1]

Replaced the spark plugs on my 1993 rev 3 tubby last week and thought I would do a compression test while I was at it. A little concerned about the results 147-149 psi across all 4, although there are no wild discrepancies between any 2 cylinders I was just a little worried that those readings are a bit low.

The engine has completed around 110000 miles, mixture of miles and kilometers as per usual. What results have you all seen on rev 3 engines?

Mucho thankings

John.

[foxy-stoat]

Done a test on my rev1 the other day and the results where 162-158-156-156 - which i think is a-ok

As long as they are all about the same you havent got a problem. I used a cheap'o old'o compression tester from halfaurds but I dunno how acturate they are anyway.

[black gts]

i have a rev3 turbo and when i got it it had 150ish on 1,2,4 piston 135psi on number 3
i got some forte injector cleaner and put a full bottle in a quarter tank of fuel and give it a blast .
this was done on instruction of an engine builder , the next compression test i got 170ish psi across all of the cylinders
forte chemicals are what vw main dealers use

hth
paul

[JP1]

Cheers guys, I'll try that injector cleaner. It also dawned on me that I didnt hold the throttle open while I cranked, might make a diff.

My tester is a cheapo jobby too, like you say its not so much the number as the diff in the 4. That said 147 ish seemed a little too low at the time, prob worrying over nothing.

Will report back after the cleaner and another go with the throttle open.

John.

[toxo]

http://www.celicatech.com/imagearchive/ ... /EG-37.jpg

[JP1]

Cheers Toxo, going by that I have nothing to worry about. Will do another test just so I've done it correctly tho.

Happy days

John.

[LuizeGT]

deffo hold throttle open. are those results on dry test or wet? smeer a bit of oil on the tester threads

[JP1]

That test was dry from cold, pulled the 3 fuses from in the engine bay, can never remember which is which.

John.

[Slarty]

Yeah try it again from cold with the throttle open, and then do it after you've squirted a small amount of oil into the chambers. You should see the results go up slightly after the oil has been added.

[mr2turbo99]

i have a rev3 turbo and when i got it it had 150ish on 1,2,4 piston 135psi on number 3
i got some forte injector cleaner and put a full bottle in a quarter tank of fuel and give it a blast .
this was done on instruction of an engine builder , the next compression test i got 170ish psi across all of the cylinders
forte chemicals are what vw main dealers use

hth
paul

Is that bottle of forte into a quarter of a tank a safe thing to do? Ive heard a few people mention a similar technique. Will it remove the "good" carbon build up?

[JP1]

Did the test again with the throttle wide open, 169 168 168 169, happy days

Also regapped the plugs to 0.7mm as there is a bit of a hesitation before full boost, cant hurt I guess.

Thanks for the help guys

John.

[black gts]

black gts wrote:
i have a rev3 turbo and when i got it it had 150ish on 1,2,4 piston 135psi on number 3
i got some forte injector cleaner and put a full bottle in a quarter tank of fuel and give it a blast .
this was done on instruction of an engine builder , the next compression test i got 170ish psi across all of the cylinders
forte chemicals are what vw main dealers use

hi mate
if a bit of carbon is not letting the vavles close properly then i dont think its good
but i do know what you mean , i got told right off by my dad years ago for cleaning the top of a set of pistons , he said clean so i did ,down to metal .he said it would lower the comp. readings (means nowt to me)a 11 year old nows nothing ha ha

[jimGTS]

cleaning top of pistons will lower compression readings.

if your comp readings are high, id expect lots of carbon buildup on the piston tops.


pretty dam sure your ment to test compression on a warm/hot wngine, not cold.

[mr2turbo99]

So a bottle of forte into a quarter of a tank should be ok?

Jim's right too, it should be done on a warm engine. Also make sure the battery is tip top. You want the same crankage on each cylinder when you run the test.

[GTS GAV]

wich fuses have to be pulled when doin the compression check? are they always the same fuses on all cars?

[jimGTS]

I don't remove any fuses.
Just unplug the coil lead from the dizzy and that's all I do.
Wedge something to keep the throttle wide open, remove plugs and just crank the car 5-7 times.

[Peter Gidden]

I don't remove any fuses.
Just unplug the coil lead.

The advantage of pulling the fuse is that you stop the injectors from firing neat fuel into the bores repeatedly.

[jimGTS]

Bgb doesn't mention anything about fuses, so I've never bothered.

[RyanRs]

you should pull the efi fuse to prevent the injectors firing. there is a lot of fuel injected when cranking and a lot of that fuel will end up in your oil if its not being burnt. expecially if you have bigger injectors. bore wash is also bad for rings/walls as the oi coating is washed away.

[jimGTS]

Fair enough.
Never been an issue for me tho.
Noted for future