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The mkiv Supra Owners Club

Compression figures


adi2009

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Had my compression test done with removing the fuel injection fuel and the results were

 

cyl 1) 230psi

" 2) 220psi

" 3) 220psi

" 4) 230psi

" 5) 230psi

" 6) 230psi

 

Now how can this be possible??? only thing i can think of is that i pulled out the wrong fuse instead of the fuel injection fuse.

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We fitted custom spec low compression (8:1) JE forged pistons to a 3S-GTE engine along with Total Seal gapless rings. After running it in, we compression tested it and got 190psi in each cylinder - higher than we were expecting given it was around 180psi standard with 8.5:1 standard compression ratio. Now the spec sheet with the rings was confusing, mentioning both file fitting the rings and saying they came ready to fit with no file fitting required :shrug: so we went with the lube everything up and fit them with a ring compressor method. Anyone any ideas on whether this could effect the compression results obtained? I think I'm confused about this because you measure dynamic compression rather than static compression when you do a compression test, don't you?

 

Cheers,

 

Brian.

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Total Seal, like most American companies, can't or won't make a ring pack to fit a designated bore size, they expect YOU, the end user, to do it for them. I suspect they are too tight, and bore scoring / seizing may result. "Gapless" rings (no such thing, really) have been well proven in Formula race engines to no measurable effect in normal use, they attract attention because at very low RPM's (cranking speeds) they show increased compression due to less leakage, whilst at real world running RPM's they seem to do nothing that a conventional ring pack does.

 

An Omega or Cosworth ring will fit a desinated bore size, bang spot on, with no work at all, as they are actually CAST for that bore size, not generically for X to Y bore sizes, with different tensions and roundness in different bores.

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