Tach issue
 

I recently installed my AEM. Using the provided startup calibration I started the car unfortunately the tach didn't work. After some reading I found that 95 does not have a tach signal from the coils to the tach. I then tried this: Setup>Advance setup>Tach/Speedo Control>Options> then change the tach output to 2 which activates LS7 the tach output. After I did this the tach worked however when I would blip the throttle the tach would go to zero while the engine gains RPM, once I take my foot off the throttle the tach would read rpm. Any help with this issue would be greatly appreciated.

Sorry for the thread necromancy but I'm on the edge of buying an AEM and have a late 95' also. Does anyone know the answer to this? If the OP is still around, did you ever figure it out?

I have a 97 and had to change the number on the Tach output as well. Copied rafa's settings for this that he had on his 96.

Its worked for the last 2 engines I blew up along the way.

I'll check and can post up my settings.

Are you running a 30-1710 or a 30-1720?

1710 with a 95 I would think.

I've run both (one with an adapter harness) and the settings were the same.

Yeah, I'm looking at a 1710, I just wondered what you were using. I searched and saw your boomslang conversion thread for the 1710. So, the LS7 output can generate the correct signal then? That's what I was after. According to AEM's pinouts they have both the early car's and the 95.5+ tach pins going to LS7. I'm guessing you just turn on an internal tach driver in the software then?

Yes...just turn the internal tach driver on... there is a number to put in too

Thanks!

So Emilio from 949 just called me (I left him a vm yesterday) and said he didn't think it would run the tach in the cluster. You have any specifics on how you did it?

I guess I'm no help, these are the only options that helped me to get mine working and you already have done that. Its like you have some sort of interference while on the throttle or something.

No, no. That may do it still. I actually don't have the unit yet, I'm just being preemptive! I just thought it was odd that Emilio said he didn't think it would work and wanted to see your settings, so thank you again.

What's your RPM Offset vs TPS Table (in the advanced idle template)? Do you have any values above 1000? Cause if so, then that's your problem.

I doubt you could achieve that with a 1710 without any extra hardware. Most likely not. The reason is if you want the EMS to drive the tach it can be set (the Tacho option field) to invert the LS signal on teeth count. The Miata tach needs 2 pulses per crank rev and the OEM miata crank or cam sensor drives the EMS with 2 significant edges per crank rev. Thus you want the signal inverted twice per each tooth? If a value of 0 in the Tacho field does that, then you're ok, but I doubt it does it.

IIRC we got BikeInDirt's car (same as yours) with a simple transistor hooked to the crank signal wire which grounds the LS7 output per significant crank signal edge which simulates what the stock '90-'95 coil packs are doing. Flyin' Miata were selling a box like that in the past for few bucks too, but it is very easy to DIY if you have to - prolly 5 minutes once you buy the part which should cost cents.

Or the better option is: just upgrade to a 12 tooth wheel from TSE, use the NB crank sensor and let the AEM drive the tach (put 3 in the Tacho field). The main benefit is that the 12 tooth wheel has 6 times better resolution than the stock one (12 teeth vs 2) plus it is not cam driven thus you get much better timing control ...

Got any details on exactly how to do this? It may be how I do it short-term.

I like this idea and will probably do it eventually if I can figure out a way to mount a sensor for the wheel. I'd forgotten about the TSE wheel and it never occurred to me that it would make any difference in driving the tach.

Did some reading on the TSE wheel. Looks like the sensor might just bolt right up, huh? Any good, detailed writeups on this anywhere? If I understand I would need:

-TSE wheel
-NB crank sensor (How does this get wired in?)
-96 + pulley boss

Also need to mod my CAS, correct?

There's a writeup on M.net that J_Man wrote, a quick google search will turn it up. Page 2 of a 3-page thread.

I found this:

http://forum.miata.net/vb/showthread.php?t=387335

and this:

https://www.miataturbo.net/showthrea...light=12+tooth

No 3 pagers though.

Are there any specifics / instructions when I buy the trigger wheel?

Not really, no. It was a pet project for a few AEM guys, and I can provide a little setup help if you are running NB sensors, but if you're going to use the NA cam sensor, it's best to follow J_Man's instructions below.

http://forum.miata.net/vb/showpost.p...8&postcount=28

Thanks. How do I know if I need the spacer or not? Is there a certain distance the wheel needs to sit from the pulley or something?