Tuned an NB miata turbo using MS with alternator not hooked up by mistake
 

Hi, working on an NB Miata turbo build with a microsquirt ECU. Like most peoples builds there is a fair bit of back story behind were I am up to but it may not be very helpful diagnostically so i can provide more upon request of anyone willing to offer advice and help.

I have gotten the car to the point where it starts and idles quite well, the catch being for a number of reasons, i didn’t have the alternator connected. I was only doing short tuning sessions for idle (hadn't progressed to the point where i was going to look at the rest of the rev range and maps for VE, timing and so on) and i had the trickle charger on over night between tuning sessions so didnt notice a problem.

When i noticed, i connected the alternator and then it stalled the car instantly.

I initially went down the path of thinking my alt was cooked as it was the original that had done 180,000km, however i have now categorically ruled out the alternator as the source of the problem. Have had it tested and also tested a brand new one and it still stalls.

So, when i disconnect the alternator (electrically not taking off the belt) the car starts and runs fine. The voltage is a bit low but things work. If i reconnect the alt electrical connection the engine dies. If i leave the alt connected the car cranks over and fires for a split second but then dies. It feels like its a bit rich from looking at the AFR but im not good at interpreting the data log graphs.

What i wanted to ask, is if this could be tunerstudio/MS not liking the fact that when the alternator kicks in it puts a significantly higher voltage back into the system and then the fuel/timing/spark is out because of that different votage?

There are voltage correction tables for the injectors and the coils right, that adjust the base map if the votage varies?

From my limited knowledge the car should start off the battery but then from that point it runs from power coming directly from the alternator from then on right?
And therefore i have tuned the cars fuel required for cranking to the battery (fine) but tuned the after start enrichment, warmup enrichment and idle to the battery output rather than to the alternator output voltage which is significantly higher. Is that my problem and how would i fix it?

Hoping this makes sense as its so frustrating to have the car run fine on battery but not with the alt hooked up.

Looking for help and advice here please.

Hopefully somone has made a similar mistake as i have and then can advise how to correct.

Cheers.

I don't have any experience doing this, but maybe try to load a base tune again and start from there again. The voltage correction settings can make big differences, but you want to use the correct settings for your specific injectors.
Also bear in mind that the alternator is hard to turn when generating power, so it makes sense that it will kill your engine. Maybe you just need a little more idle valve duty.
Good luck!

The flowforce injectors had their own dead time and voltage correction table that’s already been put into the TS file from me so i feel it must be an issue elsewhere but ill take the advice and start the process again from scratch. Maybe a change to the AS enrichment and idle duty is needed. Thanks.

You have an NB, which has an ECU-controlled alternator. The microsquirt can't control the alternator. Is the alternator's wiring connected to anything?

I am using the microsquirt in piggy back mode so the alternator is being controlled by the stock ECU. I trialled a stand alone speeduino alt control module to sense voltage and engage the alternator and it didnt change the outcome. The alternator is kicking in when the voltage from the battery is low, thats working fine, it just stalls the engine.

I realy appreciate the helpful suggestions.

If you tuned the engine with a low battery, then when the alternator kicks in, all the added PW from battery voltage compensation is removed and the engine runs lean and stalls? I can't think of anything else.

Apparently from looking at the logging while ive been running it on battery and then hooking up the alt which stalls it, its loosing sync with the cam sensor when the alternator jumps the voltage up to 13.5-14v.

So for aome reason its either not getting the signal from the cam at the higher voltage, or theres interference noise being generated so it can get a clear signal. Thats making the computer not know when to fire coils/fuel and it wont start. So something about the cam signal at the higher voltage. Bad ground, shielding, noise etc.

Still lost but continuing to hunt down what to do.