Compression test results = Bad

[GTR-32U]

Ever since I have owned my R34 GTT  ( 2 yrs + ) the car has always felt lethargic, almost as if it was holding back. So after ruling out many other factors by trial and error a compression test was performed by a reputable workshop in Sydney.

 results are :

Cylinder 1 - 185 psi

Cylinder 2 - 179 psi

Cylinder 3 - 88 psi

Cylinder 4 - 90 psi

Cylinder 5 - 160 psi

Cylinder 6 - 182 psi

Really ugly numbers I know, A leakdown test was performed as well and the end diagnosis was that air was leaking back through the throttle body.

The workshop believed that the failure was a headgasket and a valve not seating properly. They also believed that the problem was isolated to the top end, they didn't believe that it was a bottom end failure

The car doesn't use any oil or blow smoke nor does it stain the rear bar or smell of burnt oil. Of late I can hear a sound very much like a tappet sound if I am slowly driving it revving beyond 2000rpm. It is most noticeable under the lightest of acceleration or holding it at 2000 rpm upwards. but cant be heard under heavy acceleration.

Very soon the Cylinder head will be coming off and sent away for a full freshen up and then visually inspect the bores.

My question is what could have caused this to fail ?

The car is stock ecu and Turbocharger but I believe this wasn't always the case.

The turbo has been removed at some point in its history....

but I'm just looking for answers as to why as I don't want this to happen again once the head is sorted

[GTSBoy]

You won't get an answer until you pull it apart. And even then, it's only 50/50 that the answer will be evident.

[Duncan]

Agreed.  Although head gasket is the most likely (but not) only reason for 2 adjacent cylinders to have low compression