Miata Spark - Erratic CAS signal with spark ouputs connected

AlHounos · Post by **AlHounos** » Mon May 15, 2006 8:37 am

V3 board MSnSE 029j

I've done the DSM input and output mods, and the car has been running great on fuel only using the CAS for RPM signal. But when I connect spark, the car backfires and barely idles on two cylinders, like the timing is WAY off. I noticed the Tach on megatune jumps around wildly (from 0-8000rpm) when it is "idling" like this. It worked fine when it was on fuel only.

I have not changed any MSQ settings. The only thing I have changed is to connect the spark output wires to the ignitor.

Thanks a bunch!

AlHounos · Post by **AlHounos** » Mon May 15, 2006 2:15 pm

I just noticed DIYautotune's instructions have changed again. It now specifies 2 470ohm resistors on the input mod instead of all 3 being 1000ohm.

Could this be the problem? I've got some 330s laying around, should I put them in?

md95 · Post by **md95** » Mon May 15, 2006 8:28 pm

Yes, i remeber that post where this was discussed. There were one or two people getting some strange behavior using 1k resistors. The 470 ohm resistor was the one used for both of the "pullups", on for the main 12v crank position signal, and the secondary cam 5v signal. You still need the 1k resistor that goes from pin 11 of U1, for input protection in case of incorrect output settings(pin 11 can be both an input and output). Try this out first, it should take care of your issue. As for using the 330 ohm resistors, i'm not too sure on that. I would think it would work, but the 470 ohm have been proven to work 100%..This is all fresh in my head, since i am currently building a MS for a 91 Talon AWD turbo 4g63..

Aussie Driver · Post by **Aussie Driver** » Tue May 16, 2006 3:29 am

Al, do you want to give it a go with my msq?
My MX/miata is going great guns with the spark.
Send me a pm with your email address if you want the msq.

AlHounos · Post by **AlHounos** » Tue May 16, 2006 10:10 am

Changing resistors didn't work.

I guess I'll try it with aussie's . the only thing left could be my wiring, I guess.

AlHounos · Post by **AlHounos** » Tue May 16, 2006 10:44 am

It appears that I fixed the CAS signal by swapping the wires I connected to. Problem is, it runs worse than it did before. It won't even idle now. At least the tach on MT reads the same as the car's tach. 300rpm.

Using a timing light, spark appears to be occuring at about 20 degrees after TDC.

Edit: Aussie, is your pinout on miataturbo.net for a 1.6 ECU? I had the CAS wires connected as you have in your pinout, and I was getting the strange tach behavior.

Aussie Driver · Post by **Aussie Driver** » Tue May 16, 2006 4:04 pm

Your problem could also be your wheel decoder settings. I run mine at the 024s setting because my car runs like crap with the 025 setting.

Post by **jsmcortina** » Wed May 17, 2006 4:18 am

Upgrade to 029q2. I recall a few bugs in 029j

James

AlHounos · Post by **AlHounos** » Wed May 17, 2006 11:58 am

I upgraded to q2. No help unfortunately. I noticed that when cranking, fidle/spark flashes, although I have D14 for spark A. Output 4 also flashes, but not like a spark output should. I have D16 setup for spark B. I am getting spark if i pull the plugs though. But at nowhere near the right time.

AlHounos · Post by **AlHounos** » Thu May 18, 2006 8:58 am

I got the car to fire and idle by turning spark output inverted off. THis is the opposite of what the other miatas are doing, but the same as the DSMs. The car seemed like it would be idling fine, but the ignitor gets hot quickly, so I haven't let it run long.

Is this spark non-inversion hiding something thats backwards in my car?

md95 · Post by **md95** » Thu May 18, 2006 3:14 pm

AlHounos wrote:I got the car to fire and idle by turning spark output inverted off. THis is the opposite of what the other miatas are doing, but the same as the DSMs. The car seemed like it would be idling fine, but the ignitor gets hot quickly, so I haven't let it run long.

Is this spark non-inversion hiding something thats backwards in my car?

How are you firing the coilpack? Are you using VB921's, or an ingitor module from an OEM setup? If you use the 921's, you MUST invert spark output. If you are using an ignitor module, then do NOT invert spark output. If its getting too hot at idle, then reduce the running dwell time. You run dwell control setting, correct? Run dwell control, and try 3.5-3.8ms running dwell, and .5 - .7 ms discharge period.