Jumpy tach on CAS 4/1 mode - Jimstim

[The_Pipefather]

I'm using the jimstim v1.3 on an MS-I modded for CAS 4/1 input (miata), running 029y4. The problem is that the tach jumps around in Megatune. Between the set rpm and exactly 1/3rd of set rpm. Example if the pot is turned to 1500 it drops to 500 momentarily, then jumps back up to 1500 and keeps doing that.

I checked and double checked every single connection but am unable to solve the problem. The CKP and CMP signals are apparently pulled up to 12V internally in the MS so I removed both pullup jumpers to no avail.

Can anyone suggest a solution?

Thanks.

[The_Pipefather]

Somebody?

[jsmcortina]

Do you have the second trigger polarity set correctly in Megatune?

James

[racingmini_mtl]

If you increase RPM, does it still do that?

Jean

[The_Pipefather]

Yes, it does that at all RPMs. If I set it to x RPM it will jump intermittently between x and 0.333x.

My Megatune settings are

2nd trigger active edge: rising

trigger pos A: 2

trigger pos C: 1

All others 0.

[Wilder21]

I have just finished building my MS-I Version 3.0 with all the mods on the DIYautotune.com guide to firing a 1993 miata. I have also flashed the MS ECU with the MSPNP base map.

I have the Jimstim connected, it is setup as a CAS wheel simulator, and trigger 2 is jumpered to pin 25 (I1A)

The inj1 and in2 show they are "firing" in relation to engine RPM. But here are my issues;

The Spark output 1 and spark output 2 LEDS on the MS only "both" light up at certain RPMS, sometimes only output 1 is lit. and at higher RPM settings, they just don't light at all.

Also i have the same issue with the tach signal.
examples are at high RPM would be 4000, and it will jump down to 1300rpm, and at 7000rpm it jumps down to 2200 rpm. Also noted that RPM Fine adjustment on jimstim only effects the upper limit of the RPM set. Ane the lower the fine adjustment is, the less fequency that the rpm jumps between the upper and lower limits.

The amount that the RPM jumps up and down and the "timing" of it appears random.. i cannot think of what could be causing this.

Any help is appreciated!

Tyler

Here is a show video showing what exactly is happening.. don't mind the free entertainment in the background LOL, my 3 year old's favorite show.

http://s67.photobucket.com/albums/h285/ ... ure188.flv

Edit: I don't think it's the signal that the jimstim is providing.. i jumpered the primary tach and 2nd trigger to LED 1 and 2, and they both flash even and at a 4:1 ratio..

[Wilder21]

I have solved the situation that i was experiencing.. Seems the jimstim need s to be setup as a 4G63 wheel.. not the CAS 4/1 that i was led to believe.. The whole system works flawless now, and is ready to be integrated into my Mazda powered 77 triumph spitfire..

Thanks to Matt @ DIYAUTOTUNE for the help.