Compression test gauges - can they be trusted?

[wandee 0]

Last week I gave my mate's VR a compression test to see if it was in good health.

 

I used a compression tester that I have had for a couple of years. It's a Sykes Pickavant one so a pretty reputable brand I would say.

 

When we carried out the test we were a little concerned with the results. Not disastrous but not as good as others have recorded on this forum. They were as follows:-

 

1) 150psi

2) 160psi

3) 155psi

4) 160psi

5) 155psi

6) 160psi

 

All within tolerance of course but not as good as the 170/180 readings that most people seem to record here.

 

I noticed, from reading the other threads, that a lot of people used the Draper 37442 tester to record their results so I went and bought one and did the test again. This is what we got :-

 

1) 170psi

2) 190psi

3) 180psi

4) 195psi

5) 180psi

6) 190psi

 

As you would expect, we were overjoyed and just put the initial test readings down to a dud tester.

 

I then decided to test my Mk2 1.8 Golf GTi, with 140K on the clock and pretty much FSH, to see how healthy my engine is. This is what I got.

 

1) 205psi (14 bar)

2) 205psi (14 bar)

3) 205psi (14 bar)

4) 205psi (14 bar)

 

Now call me a miserable sod but I have trouble believing that a 17 year old engine with 140k miles behind it can give such spectacular results, even if it is a VW. And especially as the manual states that a new engine should only give readings of between 11 to 13 bar!

 

Which leads me to my question. Is my mates VR as healthy as this Draper tester suggests? Or can these things really be trusted to give accurate results?

[CorradoVR6-Turbo 0]

VR,s will wear more quickly than the four cyl models,but the readings are close to even all round so i would suspect it normal,why have you done a comp test?

[wandee 0]

Yeah the readings are even but they just seem, in the Golf's case anyway, TOO high.

 

We did the compression test on the Corrado as we sometimes think it might lack a bit of power and there is the odd puff of smoke from the exhaust from time to time.

[paul20v 0]

you dont know if the golf has ever had its head skimmed as this will up compression , the golfs reading are a little high

the vr reading look nice and even i would have no worries at all with them readings , your smoke is more than likely a bit of stem wear there is posts covering this , are you using much oil then ? mine will do a little puff of blue sometimes but it has to be really hot and after a long down hill , it does nt do it otherwise,

and no oil is being used , lots of vag engine get stem wear or seal wear i would not worry about it to much unless you are throwing loads of oil in .

[wandee 0]

Pretty sure the Golf has not had the head skimmed. I have a shoebox full of service and modification history and although it has had the ECU remapped there is no documentation of the head being touched.

 

Whilst I am sure that there is nothing to worry about in the Golf, even if the compression tester is telling fibs, the Corrado may be a cause of more concern if the actual readings are closer to the ones taken with the Sykes Pickavant tester.

 

Would it be possible for a brand new tester, ie the Draper one, to be a dud?

[paul20v 0]

well anything could be dud when its new , have you done a wet test as well to see if that makes any diiference , either way both reading off both cars are good so i realy would not worry , i have done loads of compression tests on many different cars and them readings are all tidy and there all even.

[mattkh 0]

I used a compression tester that I have had for a couple of years. It's a Sykes Pickavant one so a pretty reputable brand I would say.

I noticed, from reading the other threads, that a lot of people used the Draper 37442 tester to record their results so I went and bought one and did the test again.

Which leads me to my question. Is my mates VR as healthy as this Draper tester suggests? Or can these things really be trusted to give accurate results?

Hi

The plugs are very deep in the golf engine. Please put up a picture of the 2 compression gauges especially of the adapters used.

The other thing is did you have a fully open throttle when testing.

[Supercharged 2]

You also have to be careful using cheap testers on the 16V's as they sometimes get stuck! - Stealth have had 2 or 3 cars towed to them before when this has happened - ie make sure there is a nut and you have the correct tool to remove!

 

A lot of people also don't realise you have to set up conditions for the test - ie warm engine, FP relay unplugged or (fuel rail wiring) and throttle held open and crank for 5 secs

[wandee 0]

Nah, I did the test in the correct fashion. Engine fully warmed up, coilpack LV disconnected, fuel pump relay and fuse 18 removed & throttle fully open. I've done countless compression tests before on other cars.

 

Like I say, I wouldn't count a Sykes Pickavant tester as cheap and nasty. It's this one..

 

http://www.cromwell.co.uk/SYK5033140S

 

and as you can see is actually a lot more expensive than the Draper one..

 

http://cgi.ebay.co.uk/A1-QUALITY-NEW-DR ... dZViewItem .

 

The Sykes one is a couple of years old so maybe needs calibrating?