Hello everyone. This is my first post on these forums. I have a decent understanding of EFI systems and tuning but the more I learn, the less I know.
Anyways, the test engine I'm using for my masters research is a single cylinder gasoline engine with identical cylinder geometry to the Ford Mustang Cobra engines. I've spent the last year getting it up and running but now that I'm ready to test I'm running into a few issues with the ECU/MegaTune. I didn't set up the ECU or do any of the wiring so I don't understand everything although I've been reading the MegaManual to try and become familiar.
The problem I'm having is that under certain conditions (this was steady state at 2000 rpm and an intake MAP of 54 kPa) the injector pulse width fluctuates. I had the engine running at around 13.5:1 AFR with an injector pulse width of 7.495 msec but every few seconds the pulse width would fluctuate to something around 12-13 msec (it was very brief). You can see the "clear needle" on the Pulse Width 1 gauge that shows where it would fluctuate to. Since the engine is running in the same cell for 2 hours at a time to do testing it messes up the results slightly.
I wanted to see if anyone has encountered this before and if they know of a solution. (Oh and ignore how ugly the map is- it doesn't really matter since we only operate in a few of the cells at steady state)
Issue with injector pulse width occasionally fluctuating
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
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msiddalingaiah
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Re: Issue with injector pulse width occasionally fluctuating
Are you running speed density or alpha-N?
If you are running speed density, it sounds like you are encountering wild swings in manifold pressure which is a problem with single cylinder engines.
Unless you sample MAP synchronous with the cam, you will see aliasing effects that come and go depending on RPM and sample rate of the MAP signal.
If you don't have a cam sensor, alpha-N is a simple solution.
If that's not the problem, look at the logs and see if you find a correlation between pulse width and sensor inputs, e.g. MAP, RPM, CLT, IAT etc.
If you are running speed density, it sounds like you are encountering wild swings in manifold pressure which is a problem with single cylinder engines.
Unless you sample MAP synchronous with the cam, you will see aliasing effects that come and go depending on RPM and sample rate of the MAP signal.
If you don't have a cam sensor, alpha-N is a simple solution.
If that's not the problem, look at the logs and see if you find a correlation between pulse width and sensor inputs, e.g. MAP, RPM, CLT, IAT etc.
Madhu
1990 Suzuki DR350S EFI Conversion
Returnless, adjustable electronic Fuel Pump Controller requires less power
1990 Suzuki DR350S EFI Conversion
Returnless, adjustable electronic Fuel Pump Controller requires less power
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Bernard Fife
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Re: Issue with injector pulse width occasionally fluctuating
Mr.D,
Your best bet is to post a datalog and MSQ.
Without seeing those, my first guess would be that accel enrichment is triggering. Increase the TPSdot (and MAPdot if used) threshold so this doesn't happen. There is more on this here: http://www.megamanual.com/ms2/tune.htm#accel.
Lance.
Your best bet is to post a datalog and MSQ.
Without seeing those, my first guess would be that accel enrichment is triggering. Increase the TPSdot (and MAPdot if used) threshold so this doesn't happen. There is more on this here: http://www.megamanual.com/ms2/tune.htm#accel.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw