172 Cup Turbo low compression?

[Briank_]

Hi all,

Did a compression test today on my 172 cup turbo. It shows readings that where though all quit the same, a tad low.
Cyl 1 135 psi
Cyl 2 130 psi
Cyl 3 130-135psi, in between
Cyl 4 140 psi

Car runs great, sparks where a tad black, any suggestions or things I can check to adress the problem? Test was done with a cold engine since it ain't rolling at this point.
Car had it's turbokit fitted at engine dynamics 13/08/2016 less than 2K miles ago, the pre-dyno showed it had 178BHP.

Thanks!

 

[scotiamr2t]

cold test will usually give lower figures but they do seem a tad low. That being said they are all pretty much the same, and the car is running great so what is the issue?

Also is it running the standard pistons, HG etc?

 

[Briank_]

All stock motor except for the 230 turbo kit. No real issue, just measured them and checked what they're supposed to be on these engines, and seeing values at 200psi I think mine are just a tad too low.

On the other hand, they indeed are all the same, so I'm not sure if I should be worried about it or not at this point.

 

[bashracing]

Put a little oil down plug hole and see if the figures come up would show bore/ring wear.
Don't count out inaccuracies from the gauge itself if it's a eBay Chinese special too.

 

[T.Trophy]

That is low for stock comp. When I had wossner 8.5:1 pistons in mine it was 145psi on each cylinder

 

[JamesBryan]

What gauge did you use?

Don't say Gunson.

 

[T.Trophy]

Can't remember it was from work.

 

[JamesBryan]

Can't remember it was from work.

Sorry, i meant the OP.

 

[Briank_]

Thanks for the reply's so far!

The compression tester used is one from my father in law and doesn't have any brand on the gauge itself. Used to be a sticker on the casing but it's gone. Don't expect it to be a high end one though. Will try with some oil later on to see if it matters a lot, and maybe get a second gauge in from a workshop down the road.

 

[DanSej6]

Throttle held open while cranking over or not? Closed throttle can create a lower reading.

 

[bashracing]

Not possible to get to the plugs with the upper manifold in place on the f4r, so will be no restrictions

 

[Briank_]

The manifold was indeed not in place so throttle was open. But I did another test on a megane rs250 of a friend of mine, and it showed 8 bar with warm engine. So guess the gauge is a bit shady, will try again with another one when I get the chance.