When I get back from business travel (next week), I intend to log injector voltage using a spare ADC input.

 

LOL. the infamous "i have AEM.. i have to start my car like 'this'" issue. haha.

 

I am almost certain that the voltage input to the injector will be higher than the stock injectors however, it is the voltage/current drop at the injector coil that I believe is causing the issue.

Do me a favor and measure the resistance across a stock injector and then the resistance of the resistor box and see what that adds up to... my guess is about 8-9 ohms.

The resistance of the ID1000s are 12 ohms which would in fact interfere with the intended operation of the injector driver...

 

The resistors in the resistor pack are 6 ohms. The stock injectors have a resistance of around 2-3 ohms. (I have measurements somewhere, but can't find them right now.) I'm interested in this idea, but I don't see how a resistance difference would matter, because there is no injector driver, per se. There is only a transistor that opens/closes the circuit ground.

 

Because there is a p/n junction inside the transistor. If the resistance is higher it will also have a higher voltage/current drop which will in turn take longer for the flow of electrons to overcome that junction, in turn taking longer to open the injector... this my theory anyway... why it is only doing this when warm is the kicker...

 

Fred would the coils resistance changing with temperature have a large affect as well?

 

Yes, and I am not taking credit for that hypothesis, that all goes to Dan (0xDEAD) he said that was the problem off the get go...

If the resistance rises with heat, then this may be altering the voltage/current drop at the injector driver (transistor) that tiny bit to act up during warm starts... aka inductive reactance, The injectors may also be experiencing back-EMF or a number of other things that are causing the issue... but I am certain that it has something to do with the circuit and injectors not playing together nicely...

 

makes sense Fred. This would explain why it only happens on the Evo, but only with the stock ecu. Internal circuitry + ID1000's = issues.

 

Soooooooo wonder if a phenolic spacer/composite rail would have enough of an effect on temp to combat this phenomenon. Who was it that was going to try out the Skunk2 rail?

 

But not every stock ECU Evo owner has the issue. 0xDEAD has a stock IM and rail.

 

Yeah and the weird part he tried the ecu that was in my car in his car and it still started 100% the same......mine does not.

 

That was me. I still need to get the rail. Tony has graciously offered to get me cost on it, I've just been waffling with Christmas coming up and a surprise opthamologist visit being sprung on me! My health insurance is the suck when it comes to vision!

 

FWIW, I've played with the cranking enrichment and post start enrichment tables a bit more over the past few days.

The last few warm starts I have had fired right up.

It's also been pretty damn cold out, so maybe the car is just below the temps it happens at.

I'll get a few more days on it and see if I can get the car back to having the hard start issues. If I can repeat the starting issues and fix, I'll post up my all the relevant tables in the stock ECU.

 

I suspect its the cooler weather. Mine has been starting up pretty cleanly after the usual period of time too.

 

I don't know if it's been covered (im not reading the whole thread) but it's easily done and located right on the fire wall.