had a compression test done today as im planning on a bigger turbo and remap and this is what the mechanic said, the two cylinders on the passenger side were 125psi and 130psi, the 2 drivers side cylinders were 150psi and 155 psi. should i be worried by these results? i was told by a previous owner that it has had a rebuild not long ago so maybe they just rebuilt one side of the engine thats why theres 20-30psi difference?, any way what do you think should i go ahead with the bigger turbo injectors and an esl remap or not?

 

btw its a uk turbo 2000 1998 with 129k on the clock

 

There should not be more than +-10% difference from cylinder to cylinder and it seems that you are just above the border.

I wouldn't do anything to the car as it would shorten its lifespan IMHO.

I don't see why anyone would rebuild half the engine.

 

Unless you have budgeted for a rebuilt I wouldn't bother, never take people's word for anything, unless you have paperwork to back it up. Personally I wouldn't fit a bigger turbo to a 16 year old engine.

 

was the engine hot when the compression test was done? Also as far as Im aware the accelorator should be fully pressed aswell.

 

not sure if it was hot or not i might do a second test myself if i can find one to borrow or hire, could it be the valves being coked up cause one side to be down on compression?

 

i did mine last month and recorded 160/150/160/150 just to give you a idea of maybe where it should be??

 

I did mine the other day on my 2004 Sti with 92k standard engine and my comp results are 110 on all cylinders.
Test done in th correct manor.
No smoke or anything and runs like a dream.
Gets used hard on track and 2 weeks ago had a remap @ Enginetuner with my DIY rotated td06 20g and made 424/415 on v power.
Cars can be random.
Cheers

 

think im gonna try seafoaming it ive read it helps bring compression up, theres nothing wrong with the way it drives my narrow band afr is saying rich when i put my foot down, but it goes from rich to lean up and down a lot when idleing and lightly accellorating

 

That's what narrow band sensors are supposed do; they switch from rich to lean at 1 second (1hz) intervals during curise and idle where the ECU is running in closed-loop mode. What you are seeing is the ECU constantly adjusting the mixture in response to the oxygen sensor - thats a good thing. If it wasn't switching between rich and lean under these conditions something is wrong.

They'll stop switching and show rich at full throttle due to the extra enrichment and the ECU in running open-loop (as it not using the oxygen sensor to adjust the mixture).

I can actually hear them switching by the engine tone when doing fast idle tests for MOT.

Wideband sensors work different these give a proportional signal as opposed to the "Rich or Lean and nothing inbetween" signals that narrowband sensors give.

Seafoam it if you like (or any other brand of foam intake cleaner), but I doubt it'd do any difference. If it runs smooth (hand on engine, little rocking or vibration) leave it alone. IMHO, because unless you manage to pinpoint the issue, you are looking at pulling out the engine and partially stripping it to see whats going on and thats alot of time and money to spend on a working engine.

Having said that its possible you could have a slight head gasket leak between the to cylinder (yes a head gasket can fail and you won't mix oil with water, nor pressurise the cooling system, although its usually the latter). This should get worse overtime.

On the other hand poor valve seating or piston ring issues could be at fault; It possible to slightly bend the valves during a cambelt change if the workshop manual isn't followed to the by letter, as the passenger side cams are acting on the valves at TDC (Top Dead Centre). The valves also interfere with each other too, so an idiot could screw things up. The engine will run but can sound like its got noisy tappets/lifters (its not lifter noise - its a valve not hitting its seat sqaurely). Of course that'll show up on compression check. However I'd expect it to show worse compression on one cylinder not two.

A cylinder leakage test would be a better test to re-confirm any issues.

 

would you say the pcv line is the best place to seafoam?

 

Facepalm

 

seafoamed it through the pcv valve, its running a lot smoother and more responsive now and got rid some hesitation i had, tiny bit more power and better idle too. gonna get another comp test tomorrow