Misfire at 5800rpm 750 formula car with 1108cc FIAT engine

[Dave R]

Just fitted megajolt to my 750 Formula car and got it working well in the garage. I get a solid strobe flash and spot on advance, even the 2 position configuration switch works. I can't say that I'm fully up to speed with the PC side of things because the instructions are a bit thin on the ground (hint).

However, in it's first race all is fine until I hit 5800rpm and then I have a misfire, just like a rev limiter. Any ideas what may be the problem?
Set-up: I have the TPS version, but similar to the Westfield chap who wrote recently, I'm only allowed a 2D map by the regulations. I've shorted out the TPS pin to earth to stop it drifting. I actually chose the wrong pin and have a 100% TPS all the time. I don't think this should be the problem because I set all throttle configuration advances to the same value so it shouldn't matter what the throttle value is. I've programed up to 7000rpm then put 10deg at 7500rpm as a sort of rev limiter, but I get nowhere near that.
The VR sensor is in a ridid block of aluminium with gap to toothed wheel of 0.85mm. The wheel is about 120mm dia and 8mm thick
Pin 4 of the EDIS connector had an earth wire from it which I left in place but I note that this is missing from the Megajolt diagram, could this be the problem?

Any ideas on what could be the problem? Or any recommendations on how to test for a problem....use of the time trace facility (and how to work it) or pin measurements with an meter.
Hopefully,
Dave
PS I got pole position for the first time inspite of the misfire!!!

[brentp]

Hi Dave,

A quick test to narrow down the source pf the problem would be to disconnect the MJLJ and run the EDIS in 'limp home' mode. Do you still experience a mis fire under these conditions?

Aside from that, does the misfire occur regardless of engine load?

PS. Congrats on the pole!

[david jenkins]

Dumb question...

Although you've set your own rev limit at 7500 in the map, have you set the actual rev limit value to a sensible value? By this I mean the value you set on the options view, which knocks back the advance at the pre-set rev limit.

If you have set it, just ignore me...

David

[Dave R]

Wow, what a quick reply!
Brent, The EDIS limp home (10deg) works fine but I have yet to try to rev to 5800 with only 10 deg advance. I'll do that tomorrow. I don't think I can easily test it in that condition under load without a track to play on.

David J, Sorry you've lost me with the Options View reference. An idiot's guide to that aspect would be most appreciated. As I said, the Configurator side of the game is still fuzzy!!

Thanks again for the prompt responses,
Dave

[rbalmford]

Sorry you've lost me with the Options View reference. An idiot's guide to that aspect would be most appreciated. As I said, the Configurator side of the game is still fuzzy!!

See the first screenshot on http://www.autosportlabs.net/MJLJ_Confi ... n_Software, there is an "options" tab below the menu bar. On the page that this gives, there is a "rev limit" box with a value in (the default might be 6000, what is yours set to?). This also shows up as the red hatched area on the tacho display on the screenshot. What this does is retard the ignition 100rpm before the set value (the yellow area on the tacho display), so you won't have to do it manually in the map as you have at the moment.
Rich.

[Dave R]

Thank guys, Analysis spot on......(with the Megajolt connected and switched on), I looked at the configuration and found the Tab....It was under the configuration table, not above, but when open the default was 6000rpm, less 100rpm is near enough 5800rpm. It's now reset to 7500rpm so I reckon that the problem is solved. Thanks again.

Now for the critisism, and this is ment in a positive way........ what you get for the money is brilliant, the self assembly works well, the instructions with the kit is truely excellent even for a soldering novice like me. The wiring and EDIS instructions work well and there there is help from Ford and Megasquirt sites tofill in the gaps (sensor gap for example). However when I got to the Configurator bit there was a dead stop, a hole that I fell right into. Have I missed a part of the site that covers this or is it just not there? I feel sorry for those who perhaps follow my path and get all excited having buillt the box etc and then can't work out how to program it. Here are just a few questions...

• how do you program the two configurations?
  Is Flash different to Write and how does that wotk?
  How do you save a time history?
  What happens at zero revs when starting?
  What is acceleration advance?
  How does the TPS calibration work?
  Is there a rev limiter??........oops!!
  
  Anyway you get my drift. I know it's free software and It's so close to being perfect.
  
  Now the positive bit. Is it possible to create sections within the forum to collect 'Instructions' for each of the software selection opportunities? If you could do that I'm sure each of us can write up what we know as we work it out. This saves 'someone' the whole task to writing a softare manual. It also would save lengthy searching the FAQs (I'm convinced I read there that a rev limiter would be added to the program in the future).
  
  Please treat my comments as positive and supportive of a truley excellent product at great value for money.
  With thanks,
  Dave

[brentp]

Hi Dave,

Thank you for the great feedback. I agree, an Instruction Manual for the software is needed, and it is something we have on our near-term to-do list (see http://www.autosportlabs.org/viewtopic.php?t=1350 for what we're currently working on)

So, what we will have in the wiki is an "Operation guide" to compliment the Assembly and Installation guides. This will primarily focus on using the configuration software and also cover tuning concepts.

Note that the informational pages in the wiki are editable by all of you as well. For example, if you discover something that would be useful in the installation guide you can go right ahead and add it!

Regards,

[Dave R]

Brent,
That's great news. I can see the smiling faces already!
As a treat to my ego, this is me at Cadwell Park