Z-Gad Posted September 8, 2002 Share Posted September 8, 2002 I posted this on the SDS site as well, since it is more SDS related, but I thought I might get some useful suggestions here from those of you who are familiar with aftermarket engine management... Hello all. I am having an odd problem with my timing when under boost... so here goes... My timing begins at 20 and ramps up to 40. When the boost begins to build, I have been watching my total timing on the SDS programmer. My total timing will go from 38 or so just before to boost begins, to reading all kinds of strange numbers. It will go back to 20, 16, 6,1,0,255, just totally off of the scale. I am retarding about 1 deree per pound of boost up to 15 lbs. I have checked all of my IGN timing and IGN RET values and they all appear to be normal. I also checked the sensor to magnet clearance and it is w/in specs. Any thoughts? The engine is an L28 280zx turbo engine. Thank you in advance for your suggestions, Mike Gadwaw Orlando, Fl Quote Link to comment Share on other sites More sharing options...
SHANE Posted September 8, 2002 Share Posted September 8, 2002 well i cant offer any ideas, but i am wondering what fuel you are running? my timming ramps up to 32 then i retard 1deg per psi boost. do you get any pinging with that timing? i am new at this and after seeing your post i am thinking of upping my timming also. heres a thought, are you running a knock sensor?? could that be going awol?? if you are running a knock sensor maybe it is seeing all kinds of knock and screwing with your timming. try turning the knock to zero maybe and see what that does. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 8, 2002 Share Posted September 8, 2002 Here's a wild idea---Your timing's jumping around under boost (load) right? I've read that as boost builds, cylinder pressure makes it more difficult for the flame to spread thus making it harder for the spark to jump its gap. Is it possible that the increased spark load is causing some electrical noise that is being picked up by sensor wires feeding the ecu? A very similar problem has occured with some megasquirt applications. The problem has been resolved by moving the wires or shielding them and in a few cases relocating the ecu itself. dan 81zxt portland oregon Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 8, 2002 Author Share Posted September 8, 2002 First, thanks for the quick input guys, I'm trying my hardest to get this thing sorted out before Friday. I'd hate to make the trip to Montgomery Alabama as a spectator. Now.. SHANE, I am running 93 octane pump gas and as far as I can tell, no pinging or dieseling of the fuel. As boost builds, I have been getting a little bit of hesitation, but I think that is due to the timing values jumping all over the place. When I accelerate slowly(building no boost), it smoothly accelerates through the rpm band. I am running a knock sensor and will try turning it down to zero and see what happens. Dan, interesting thought as well. I have read about improper shielding of the ECU as well (i.e. keeping it out of the engine bay), I have my sensor wiring along the walls of the engine bay away from the enging) and the ECU is in the stock 77 location on the driver's side where the kick panel is. It seems to effect only the timing values though. This is new ground for me as well. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 8, 2002 Author Share Posted September 8, 2002 Thanks SHANE, it was the knock sensor screwing with the timing. I had the knock sensor attached to the engine block instead of the cylinder head and it must have sensed the pistons slapping around while under boost. Problem solved and now it is on to tuning... Quote Link to comment Share on other sites More sharing options...
SHANE Posted September 8, 2002 Share Posted September 8, 2002 question, i have not installed the knock sensor and will install it in the stock location. i dont think you are supposed to put it in the head, as there is alot more noise there. i thought the stock location would be fine. maybe not? could you adjust the sensitivity to make up for the extra noise? Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 9, 2002 Author Share Posted September 9, 2002 The knock sensitivity can be adjusted. I am just going to disable the knock sensor for the time being and go from there. As far as location, I'm not sure where the best place would be. Quote Link to comment Share on other sites More sharing options...
1FASTKINGCAB Posted September 20, 2002 Share Posted September 20, 2002 My factory Knock sensor is dead center on the manifold. although I have a V6 there may be a better place for it on a L6 Quote Link to comment Share on other sites More sharing options...
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