thetech

iTrader: (1)

I recently purchased and received a complete V3 assembly from DIT Autotune. Everything appears to be functioning fine, however I am having problems with the ignition input signal. The setup is on an RX7 running fuel only using a distributor for ignition with MSD blaster coils - I have stripped back the shielding on the ignition wire (on the DIY Autotune harness), taped it up with electrical tape, and used a ring terminal on the ignition signal wire and connected to the negative terminal of the leading coil.

The problem I am having is that the ECU resets itself upon cranking. I have confirmed all the power sources, grounds, etc (engine is grounded to chassis, also engine grounded to battery, and MS and sensors grounded on engine at same point as battery) are all good and finally decided to disconnect the ignition signal wire which fixed the resets upon cranking. I am getting a tach signal which occasionally spikes high (sometimes 38k rpm as seen in previous datalogs).

Anyone have any ideas how I can fix this?

Terrh

iTrader: (7)

have you adjusted the two pots on the MS that deal with tach signal? if not, I'd start there.


no idea on your resets, unless you have a really crappy battery. But even then, my MS worked fine all the way down to 7V so I don't think that could be it. You're SURE that the is connected to something that has power with the key set to "start" and not just while it's set to "on?"

thetech

iTrader: (1)

Yes, 100% sure...if I disconnect the ignition wire, there are no resets at all during cranking. Battery is fully charged too

renns

I ran fuel-only MS a few years ago, and needed to add a resistor in series with the tach line to the -ve leading coil terminal. IIRC it was up around 20-40kohm range. Stick a pot in series, and adjust until the noise is gone, then replace it with a fixed resistor of similar value. Depending on how your V3.0 was built, you may be able to do the same thing with the internal adjustment pots. I'd start with R56, adjusting CW a couple turns between each test.

You removed the ignition signal wire, and now you get a tach signal? Doesn't make sense. Please clarify.

thetech

iTrader: (1)

Sorry, what I meant was that if I remove the ignition signal wire from the -ve coil, I no longer get resets when cranking on the MS. This is basically my confirmation that its not a ground or a crank/run +12v issue.

thetech

iTrader: (1)

I've been told by DIY that my board is built not using the circuit that R56 is on. I will try the inline resistor though and report back.

thetech

iTrader: (1)

Good news! I tried a 44k, 33k and 22k resistor in series with the ignition wire. The 44k created a no-reset situation but the RPM was extremely low (too low, 40-100rpm) under cranking. The 33k looked to have roughly correct RPM (100-250rpm) with no resets, but the car would not even come close to starting.

The 22k still has a reset (and spike to 4500rpm) immediately upon cranking, but then stabilizes immediately and the car starts and runs fine. I'm going to do some more testing later, but for now this looks to be good! Slightly confusing as to why the 33k OHM would not start the car (it would crank without ever really sounding like it was about to fire).

I've attached the 22k and 33k ohm datalog. I'd like to use the 33k ohm as it had absolutely no reset during cranking at all.

H4Inf

I think I am having a similar issue... I get random spiking, and when the rpm reads like 65000, no fuel is injected of course... just see the graphs below....



Have you found a solution you are happy with? I have tried 2 dizzy's and they both show the same problem, so i'm guessing it is not them. Also all wiring is new and connections are good.

Could it be to do with the condensors on the dizzy not being hooked up???