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Discussion and questions related to the course Ethanol & Flex Fuel Tuning
hey guys, having a bit of a drama with my knock detection with my car just freshly running E85. Running the base ignition map that was made on pump gas and the base fuel table however my M150 is detecting a fair amount of knock at WOT and low rpm mid throttle sorta deal. I read a bit that E85 can knock on the rich side so Im wondering if the base fuel map is to rich. Currently .8 - .84 lambda at around 140+kpa absolute or like maybe 8 psi+ ish I think. cars running 8-12psi depending on how far up in the rev range it is as its Supercharged. So my question is should I maybe lean out my fuel mixture or back timing off? I just thought I would be having less knock issues running E85. Even if someone has a good target fuel aim for a 12.5:1 CR car I can try. Thanks in advance.
i would expect to see something like this for e85 approx your compression is pretty high so I would be watch the intake air temps
they could be getting pretty high if its supercharged
what happens if you retard it ?
E85 won't necessarily be more knock prone at rich mixtures but it can be more prone to pre ignition but you'd know if you're getting pre ignition because you'll have a hole in your piston. 0.8-0.84 is fine for low boost on E85. I target 0.80 on our own car on E85 with 12-13 psi boost for a reference. I'd suspect that you need to readdress the knock threshold personally. I suggest using audio knock detection to validate that the M150 is really detecting knock.
Ive been doing a bit of research and I think its because i kept the 98 fuel ignition map which was around 7-10 degs timing in max boost areas. It defs shouldnt be knocking with the same ignition map as 98 but I feel the timing was pretty retarded. I added about 4degs to most of the map which helped and reduced the feedback the knock detection on the M150 was picking up so I have dyno time next week where I can do it fully. Obviously dont want to advance it to far while not on the dyno with actual knock detection. As long as the fueling is good im pretty happy however just wondering if any of you guys have experienced this sort of thing?
also replying to ross, if I retard it more then what the base ignition map for 98 was it gets worse. I think im onto it.
on a side note, took the car for a spin while watching over it again, Noticed its not actually knocking but is missing. I believe the car might not like being made to have this much boost on E85 and its having trouble igniting the mixture under full boost. This may not be the right forum to ask this but im thinking I may need to adjust either sparkplug or coil setup to get the car running awesome in full boost. My question is does this sound right and am I on the right path? will adjusting spark plug gap or dwell time/restrike % (on the m150 ecu) any insight on this would be greatly appreciated. Otherwise ill trial and error and see how it goes.
If you are running the standard coils with the calibration to match, do not change the dwell times, you will not get a gain from doing so and will shorten the life of the coils.
I dont have standard calibrations its an aftermarket ecu and my tuner apparently did all of these. Comparing my settings to similar motors Fa20's they seem a bit low. Say mine is 1.9ms at 14v, Im trying to find the specs but its so hard to get, I feel I could give it a bit more and it would still be ok.
I have attached the correct Ignition Coil Charge Time calibration for the standard Toyota 86 coils.