basically what is the most likely culprit for a miss fire on my megasquirt?
plugs are 071's, leads are megaleads escort rs turbo ones with a modified 2i coil pack to allow fitment.
i will get a standard coil pack and get new leads off MSD this week when i can if they are the most likely case, on boost there are no issues, just off boost i'm getting it happening.
any ideas, getting a rough idle at times too and i suspect this could also be to blame.

 

Got a log of it Sean?

 

i'll get one this evening.
i borrowed you timing map and it made it more noticeable, before it was like i was cruising and being held back, mint on boost though.
i was out showing a mate today how well megasquirt runs and the misfire was more noticeable with a little more load with an extra body in the car.

 

Email me a log over mate, see if we can figure it out! Typically it's worse when your trying to show someone how good it is! lol

 

When you get the log can you post it up if you find the problem. It would be good to see what the problem is. ( i need to the learning help )

 

i'll get car out in morning, not had chance this evening and send over on an email tomorrow Karl.
cheers
sean

 

Was the TPSdot% threshold being too low (11%) and triggering AE when it shouldnt be.

 

Hmmm.......This megasquirt gets more confusing lol So seans TPS was triggering afterstart enrichments?

 

lol
Not ASE... AE (acceleration enrichment), when you blip the throttle the ECU gives the engine a little extra fuel to accommodate the big gulp of air it's just taken, this is triggered by the TPS or MAP sensor (TPS in this case).
Seans threshold was too low and so it was squirting extra fuel in when he wasnt moving the throttle making it lumpy/jerky.

 

Ahhhh Now i understand lol. So much to learn and take in. Its going to be very interesting when i start to map.

 

There really is mate, and it's not just about changing values in box's or graphs either... it's understanding why you change the values and by how much to get the desired result, and knowing what the desired result is in the first place, then how those changes roll on and effect other values, and then the engine itself, and how changing pysical parts (cams, turbo's, etc..) then effect all of that to... seeing the whole picture mate!!
I've been researching/studying and asking tuners/mappers for the last year to learn as much as I have now, and thats probably only a very very small part of it... we are lucky we have such simple engines!!

 

as above, i've been following loads of issues with others and it all comes down to understandind how electronics and software work together and error spotting.
i changed my ignition map and to be honest i've lost a bit of power, i may alter it when on the rollers asap, but it's a little safer than the big advance i was running at certain loads, even though i couldn't detect det, but on the road tuning can get distracting.
everything you change has an effect on other bits/behaviours on the way the engine runs, it takes time and sadly there is never enough to get it spot on. if you did it for a living time isn't as relevent.

 

What does det sound like. I have made my det cans but what sound am i listening for? Is it noticable if it is present or not?

 

metallic pinging sound, like a metal hammer on a big metal object.

 

hmm.. I wouldnt say it sounds like a metal hammer on big metal object.
It's more like a "ticker, ticker, ticker,ticker" (say it out loud and quickly) similair to what the valve train sounds like but a bit louder and not in sequence (random) if you get what I mean?

Watch this.... http://www.phormula.co.uk/Player.asp...Analyser%20Pro

It's about 8 mins long but you get to hear a recording of Det towards the end!

 

Sorry for hijacking you thread sean. Watching that video it sounds like somebody clicking a pen lol. I take it the best place to mount the det cnas is on the inlet manifold?

 

Yeah clicking a pen is a good way to describe it, the faster you here that the worse the Det is, if you only here "click" and then a few seconds later another "click" your just starting to Det, if it's "click, click, click, click" then your in trouble and need to let off immediately!!

I have bolted them to the coil pack bracket (old Dizzy) 10mm bolt, or on the inlet manifold, both sound pretty clear.

 

Have you got any information about this stuff karl? I.e at the point of det what to do? retard the ignition ect. I suppose this is where the skills really come into there own

 

This is indeed where the skills come in, you need to know why you are detting... Too lean, too advanced, ACT's too high, etc..
Easiest way to cure it is to pull the timing back a few degree's, if your fuelling is around 11.9:1 then you are not lean, and if your ACT's are under say 50degree's (although apparently up to 60deg is not uncommon) they are ok, so probably just too advanced.
If you are lean or have high ACT's then retard the timing to stop Det immediately, and cure the problem (more fuel, bigger IC, lower boost, whatever is needed) before attempting to advance the timing again.
IMO if everything is good and you've pulled the timing back to 10deg BTDC and your still getting det then drop the boost a fraction as you have probably reached the limit of your spec.
To give you some idea my peek VE (4800rpm 27psi) advance is 16deg BTDC progressing to 18deg at 7000rpm, this will of course vary depending on your CR, Turbo, Cam, headwork etc.. so it's just to give you an idea really.

This is all of course just my opinion from my limited experience!!

 

i always put mine on the block

 

Where abouts do you bolt it on the block Gary? I know ideally in the centre of all 4 cylinders is best at the top, because thats a close as you can get to where it takes place.