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Compression worries


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Hello,

 

Recently, I had a CEL light popping out, which was traced to a faulty coil pack at cyl. 4. While I was there, spark plugs were changed and a compression test took place. Results were as follows - 1st:116, 2nd:116, 3rd:116, 4th:101 - all may be +/-10% because of compression tester scale.

 

Now, this made me worry, as of now I was expecting that the bottom end was okay (was rebuilt at 40k, now is 97k) and I was making plans of going 300-320 whp (now is 250whp).

 

This was the modification list when I bought the car (05 Legacy GT):

  • King Racing bearings
  • Cosworth Pistons, Pins, Clips, and Rings
  • ARP studs
  • TMIC AVO
  • GrimmSpeed tri-port solenoid
  • Custom cat-less DP
  • Mishimoto radiator

 

Turbo atm is unknown - seller stated it was a VF34, but since I started reading about modding - I understood it was a STI turbo and no way it could fit without mods. From what I can see without any dissassemblies - I have VF40/46, but any advice on how to recognize one from another will be welcome.

 

I was intending to inquire 5EAT ATF change / retune, check valve clearances and to plan a budget needed to get to 320ish whp, but now I am confused and don't know if I can rely on this bottom end - I need some advice what can I expect as of now.

 

Car is tuned for 95 octane (EU) fuel, runs great, oil consumption is around 1 quart, oil I use is Ravenol VST/RCS 5w40 full synth, 5EAT shifts nice and fast, no clunks and kicks, mileage is good - I can manage 25 mpg extraurban.

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Sounds like you may not trust your compression tester. If that's the case, I'd re-test with a trusted tester. If your results are still about the same, then that engine is not a great candidate for upping the power.

I'd be looking for 125-130 PSI, but that #4 15 PSI low... sorry, time for leakdown.

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  • 2 weeks later...

Re-tested with a friend, who is a mechanic. All cylinders are within the range 120 to 123 PSI. :) Happy days, happy place.

 

I also ordered a leakdown tester, but the knob broke off and the leakage gauge went ballistic right from the start, so I didn't bother continuing with it...

 

Furthermore, I spoke again with the previous owner and he assured me that the turbo is VF34, the engine builder (who is also the tuner) had said it was capable for more power, but the power target was set at 250whp/400nm to ensure the tranny lives longer.

 

At this point I have many questions about getting to safe ~320whp and it would be wiser to start a new, right? :)

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