Slipping liner - how long?

jymmiejamz

jymmiejamz

Well-known member
Dec 5, 2004
6,008
361
35
Los Angeles, Ca
The 4.6 in my d90 has aftermarket pistons that are super shallow with cutouts for the valves. Last time i did a compression test I had over 230 psi on each cylinder. I have only had issues with detonation with the fuel in California, and that was really only under heavy load in high ambient temps. I’ve got 80k miles on that motor with several cross country trips and many miles off road in remote places. I have always kept my timing pretty advanced, but did put it back to the factory setting while living in California because of detonation.
 
  • Like
Reactions: Knightspirit
D

discostew

Well-known member
Sep 14, 2010
7,727
1,022
Northern Illinois
robertf said:
I don't remember the exact #, but compression test was over 200psi. I'm afraid to retest it now, probably a lot lower since the pinging sessions

You can't correlate compression ratio directly from compression test without knowing temps and humidity and stuff. Its a complicated polytropic process that I haven't thought about since college

the stuff was ethanol free. Ethanol would have for sure helped, since the lower combustion temp may have taken it out of the detonation range alone even without raising the octane.
Click to expand...
Yeah 200 psi is ballistic. Thanks for the heads up on that.
 
D

discostew

Well-known member
Sep 14, 2010
7,727
1,022
Northern Illinois
jymmiejamz said:
The 4.6 in my d90 has aftermarket pistons that are super shallow with cutouts for the valves. Last time i did a compression test I had over 230 psi on each cylinder. I have only had issues with detonation with the fuel in California, and that was really only under heavy load in high ambient temps. I’ve got 80k miles on that motor with several cross country trips and many miles off road in remote places. I have always kept my timing pretty advanced, but did put it back to the factory setting while living in California because of detonation.
Click to expand...
What year is your Defender? Being able to move a distributor around would help. GEMS maybe can't figure it out and back off the timing enough.
 
D

discostew

Well-known member
Sep 14, 2010
7,727
1,022
Northern Illinois
jymmiejamz said:
The 4.6 in my d90 has aftermarket pistons that are super shallow with cutouts for the valves. Last time i did a compression test I had over 230 psi on each cylinder. I have only had issues with detonation with the fuel in California, and that was really only under heavy load in high ambient temps. I’ve got 80k miles on that motor with several cross country trips and many miles off road in remote places. I have always kept my timing pretty advanced, but did put it back to the factory setting while living in California because of detonation.
Click to expand...
Maybe your not having any detonation is all the extra fuel CUX dumps. I think that system pops the injector twice per revolution. Really not sure how you could run advanced with all that pressure. Tell us more about those pistons. Also I know they have high compression 4.6 engines and regular old pistons. Sometimes I read that all Bosch 4.6 are high compression engines, not sure what's true.
 
You must log in or register to reply here.
Top Bottom