Duty Cycle Spike?

Bernard Fife · Post by **Bernard Fife** » Thu Feb 16, 2006 6:27 pm

Wes,

Your alternator proabbly isn't 100% in 'top shape', and/or the electric fan may create spikes (mine does), but the idea of a stereo filter is that it protects you even if there is a lot of noise in the supply (for whatever reason).

So it's not fixing the problem, but it does keep any such problems from affecting MegaSquirt.

Lance.

Post by **grippo** » Thu Feb 16, 2006 7:54 pm

I have attached code which will hopefully fix the pulsewidth spike problem for anyone who would like to try it. I probably won't be home this weekend so won't see your results til Tuesday. If it works fine - if it doesn't or you haven't had a chance to test it, then we will resume work on it then.

FixItAgainTony · Post by **FixItAgainTony** » Thu Feb 16, 2006 11:47 pm

Gee, that was quick. 2.35 works well in my setup. I used the burst mode for the logging (roughly ~15ms updates - wow). I had several Vcc spikes, but they only resulted in a minor blip in Duty-Cycle or PW - nothing that could be noticed while driving. The car drove much better - 2nd time out and already on par with the old L-Jet computer. The file was ~10Meg... I cut out the interesting parts and put them into one file <attached>. Looks like my alternator is out to lunch. It will be interesting to see what the scope shows. Not so sure I want to look though.

Wes - I think you were watching the MSTWeak thread on data logs - The .ini file I posted has the entry to log BattV in it. It would be interesting to see if you have similar alternator problems. Here is the link:

http://www.msefi.com/viewtopic.php?t=14966

Thanks for the help,
Charles - have Fiat, may travel.

FixItAgainTony · Post by **FixItAgainTony** » Thu Feb 16, 2006 11:58 pm

Hmmm - maybe that file was still too big.
Here is a yet smaller version of it.

Charles.

wes kiser · Post by **wes kiser** » Fri Feb 17, 2006 4:56 am

THanks, but i had already modified mine to log battery voltage yesterday, and it does spike. I am going to try the code tonight, and even if it fixes it I will likely put a filter on it the power anyway. I would have tried the code this morning, but I have to take my seat out to get the megasquirt out. Thanks again for the help guys, and I am with you, I have mine running at least as good or better than it did with the factory computer.

wes kiser · Post by **wes kiser** » Mon Feb 20, 2006 8:51 am

Car hasn't had the "miss" since Friday. So it looks like the code did the trick. Thanks again.

Turbo4V · Post by **Turbo4V** » Thu Mar 30, 2006 3:04 pm

Bringing this topic back from the dead... This problem sounds a whole lot like a problem that I've been having, and hope maybe someone can give me some clues as to whats been going on.

My car has been running for months now, generally very well, with the exception of an occasional "hiccup" or stall. Every time it's happened, there's a spike in my MAP signal, and it's caught on the datalog. It's a BIG spike, the car can be idling at 30kpa, and spike to 100kpa, sometimes as high as 180kpa. (without any change in the TPS or RPM when it happens)

I've built two MS2's, one with the 2.2pcb, and one with the v3pcb. Both exhibit this problem, generally, the other sensors look to have clean signals. (Both using v2.32 based code, EDIS ignition, and flyback for the lo-z injectors)

I've tried using the lag factors to reduce the problem, but in some ways, they just make it worse (by spreading the spike out over time).

I've attached a datalog of the problem, you'll see right at the end, a map spike, map enrichment, and the stall.

I'm almost thinking maybe there's some kind of mechanical problem with the car, maybe a valve/valvespring problem or something (causing inaudible backfires in the intake maybe???)

Any thoughs appreciated!

Justin