Moderators Zedman240® Posted May 16, 2011 Moderators Posted May 16, 2011 Hello all, Dropped off the zed this morning to the dyno tuner to get the new fuel/ignition map setup and got a call later on in the day to tell me there was a couple of issues; one that he found (and thankfully rectified) was a cylinder randomly dropping out then coming back which turned out to be an injector connector with one pin not locked in its housing completely and making a contact now and then. Just needed to be pushed in further for the locking tab to locate itself. With that sorted, now when the engine is revved to 6100 rpm, a sharp (approx) 20rwKw drop is measured. He can do it several times and it always happens at the same rpm. He worked out its like a cylinder again dropping out because if you divide the power by 6, that is the same figure of power being lost. Question is, anyone ever experienced anything similar? New leads, new coilpack and with the previous L24, nothing was wrong before. Could the engine itself (like valve springs etc) cause a drop in power like that at such a fixed rpm? Injector duty cycle doesn't go over 75%, fuel pressure is where it should be and I'm running out of things to think of.. Quote
peter mc Posted May 16, 2011 Posted May 16, 2011 yes i have had valve springs do this mate , but your engine builder is the main man so i don't think this will be the problem he knows his stuff. it may be a pickup problem for the ignition but it will be only guessing need to see the problem to fix it Quote
NZeder Posted May 16, 2011 Posted May 16, 2011 you still using the oil pump - dizzy drive system/shaft? it is a known issue that as the revs climb (however usually higher than 6500rpm - so your find is interesting) the length of the dizzy drive can flex = changing in timing. These issue were found in period by Nissan and others. Best to try a crank trigger that is off the crank and see if the issue is removed. You will get much better stable timing than using the stock dizzy drive. Quote
260Coupe Posted May 16, 2011 Posted May 16, 2011 Dimitri.............are you using Stewart Wilkens equal length headers the same problem was found on a number of engines fitted with these headers Alan Quote
peter mc Posted May 16, 2011 Posted May 16, 2011 yes it did but not at 6100 it happens at 4000. it has on 3 engines i have with his pipes and efi . and my engine has the trigger in the distributor and it revs to 8500 with no misfire .no point guessing only sound work with a scope and the dyno will tell you the problem Quote
NZeder Posted May 16, 2011 Posted May 16, 2011 yes it did but not at 6100 it happens at 4000. it has on 3 engines i have with his pipes and efi . and my engine has the trigger in the distributor and it revs to 8500 with no misfire .no point guessing only sound work with a scope and the dyno will tell you the problem Cool so I assume you are not using a Zed dizzy then but something that has a trust bearing in side to keep the shaft true - this is one what to fix it. Quote
Moderators Zedman240® Posted May 16, 2011 Author Moderators Posted May 16, 2011 Mike, I'm using an L28 turbo distributor just as the crank trigger. But what is strange, with the same exhaust/intake and ignition system, the previous stock L24 had no issues. Headers are in pic below and run to the rear with twin 2" all the way through. (copy though but look identical).. Quote
MaygZ Posted May 17, 2011 Posted May 17, 2011 Dimitri, what's happening at 6200 rpm? How long does this power drop last and does it come back after this? It sounds like an ignition issue to me - on what we've got so far. Could it be something as the discharge capacitor braking ( ) down at 6100? Although as I think of it that would probably cause a drop bigger that what you are having. Maybe a plug is failing if it appears to be just one cylinder. Try new/different (maybe cooler) plugs. Having said that, and acknowledging that your engine builder is Da Man, you're first theory regarding a valve bouncing or valve spring resonating to not fully close, may be on the money. We need to know if it stops at higher rpm. MaygZ Quote
Scando Posted May 17, 2011 Posted May 17, 2011 Something we had happen with my car. When we installed the new computer we didn't run the power to the coil through the tacho as per the factory wiring. The car would get to around 4,000rpm and the timing would go haywire causing it to start missfiring. We spent a long time chasing it and in the end found it was because we had used the power supply from the computer to power the coil instead of the factory power supply which runs through the tacho. We changed it back to the factory Z power supply and it's been fine since. There is something in the tacho that takes away the electrical interference we were experiencing. Anyway, I hope whatever it is isn't too hard to sort out Quote
peter mc Posted May 17, 2011 Posted May 17, 2011 the car has been fixed it had a glitch in the tune all good now Quote
Moderators Zedman240® Posted May 17, 2011 Author Moderators Posted May 17, 2011 Problem has been solved... what was happening was the ECU was switching to a secondary map that didn't exist at exactly 6200 rpm! Somebody somewhere set it but the strange thing is I'm not sure when it was done...anyways, it made just over 150rwKw (200hp) out of 2627cc's - not bad in my books! never questioned Les' work on the motor and as it turned out, it was just an ECU hickup that had to be found. As I told him when I called him earlier today, he's probably built more L series engines than I have had hot meals! Thanks for all of your help guys...print will follow when I receive it.. Quote
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