hi,
i have an '87 t2 that i have built from the ground up myself. mods list:
E6K w/3bar
fuel pres gauge
egt (approx 800 deg C under full load)
j&s knock (stupid thing keep lighting up)
FMIC
full exh.
T78
550 pri
1600 sec
walbro 255
fp reg (44psi static)
street port w/ Hurley 3mm
wideband tuning (cruise=14.4, <5psi=12.5-13.5, >10psi 10.0AFR)

i am writing this b/c i am completely frustrated about the fact that i can still see detonation @ 13psi and up!!! this cost me 1 engine already @ 6000miles!
i think that 93 octane on this set up should be able to support 16-18psi. am i right?? please look at the following and tell me any suggestions that you have:

fuel AFR's= cruise=14.4, <5psi=12.5-13.5, >10psi 10.0AFR

timing= from 3k rpm to 8k rpm- 30deg adv @ 0psi, linerized to 12deg adv @15psi

trail split (>2k rpm)= 10deg @0psi, 2deg @ 5psi, 10deg @15psi (linerized between points listed)

corrections:

timing vs. intake air temp= starting @ 100deg 1deg ret per4-6deg temp rise

fuel vs. intake temp= i have it taking away very little to nothing above 100deg inorder to further richen the mixture

the thing is this engine is NOT leaning out. the detonation is coming from something else. i am baffled. i feel those timing values are already too conservative. can an engine detonate from being too rich? is it possible that small imperfections in the rotor housings/side plates could allow blow-by igniting the next charge?
please forward any input that you have. thanks for your time.


justin

513 518 1994

 

I'd say its the J&S hearing some other noise. Your tune is VERY conservative if everything is up to snuff (injectors, pump etc)

 

how hot are your intake air temps?

mike

 

The J&S can easily retard over 10 degrees and with 10 degress split, you end up firing the trailing plugs first.

So a little noise, too little split , too much J&S sensitvivity, and the engine gets blown by detonation that the J&S caused.

That is why I got rid of my J&S when I started running under 15 degrees split. It was causing pinging and detonation.

 

interesting, a system that is supposed to save your engine may very well be killing it. hmm...

 

i'm thinking about hooking up for the display, but not actually putting it into the ignition system

mike

 

Try going wider with the split , when my engine was stock with the E6K running things at settings similar to yours , I would get knock no matter what iI did , I even retarded the ignition to zero and it still rattled , when I checked the split it was at 12 deg , I openrd it up to 15 deg , and there was no sign of knock after that .

 

Ive beent thinking of doing the same thing. Would be a great tool and not risk screwing yourself because of neg split

 

J&S w/low split == bad

K