Ok I just got this thing running today(fuel pump wiring didn't match the FSM go figure) Anyways, I am having issues getting this thing to rev without breaking up and getting fluxuating tach signal. I checked all my wiring and everything checks out. I am pretty sure Everything on the board is in order (quadruple checked the order of assembly) so I was wondering what can cause this sort of condition. Any Ideas would be greatly appreciated.

It starts and idles fine, but I get this problem.

Anthony Lleras

 

I need more details... are you running fuel only, or ignition and fuel?

 

Fuel and ignition. when the tach fluxes I get break-up while trying to rev. I have set up my wiring and settings according to faq with the requisite changes for my injectors because I am turbo also and I have larger secondaries. I am going to try reloading the code to the processor and see what happens, but any possible leads would be greatly appreciated.

Thanx all

Anthony Lleras

 

oh and I have a stock S4 Tps run as a full range via S5 mounting bracket. Works good, no dead spots.

Anthony Lleras

 

Check the polarity of the CAS wires. I just took a look over Terrh's setup, chasing down a similar problem. His is setup with opposite teeth missing on the CAS, running missing tooth 12-1 configuration in Megasquirt. He had bad ignition breakup in the 3500 to 4000 rpm range, but it ran nice and clean below that. After switching the CAS wires, it pulls clean throughout the range.

The CAS wiring is confusing to sort out due to different models (S4/S5), and also wire colours that change from the vehicle harness to the CAS itself. What we found to work on his S4 CAS was that the CAS white wire (harness green) is +ve, and CAS red wire (harness blue) is -ve. If you do make this switch, be sure to re-check your ignition timing, as your CAS will need to be re-adjusted.

 

ok I realize this now that you say it. Mine was built in '86 (yes it is a turbo one of the first in the U.S.) so there are things about it in the wiring especially. Thanx for the info. I will try this and see what happens. Been working on it for a while now, kinda tired. Really appreciate it dudes. I will keep you updated with it.

 

This is not the correct thing to do. Instead, check to be sure that TSEL is wired to VROUTINV. Every CAS I've seen so far has the same wire colors, and between S4 and S5 models, the CAS has not changed. It even uses the same connector.

The red wire is DEFINITELY Ne+, and the white wire is DEFINITELY Ne-

Wire TSEL to VROUTINV and you'll be fine.

Reversing the CAS wires works because it causes the trailing edge of the square-wave generated by the VR sensor conditioner to occur in the right place again.

I'm sure the wiring in the FAQ is correct because the MS1 only triggers on the trailing edge, and with VROUTINV wired to TSEL, and the wiring in the FAQ, everything works. With the wiring done properly, the vr sensor conditioner will generate a rising edge to coincide with the VR signal going from positive to negative through 0, then a falling edge when it goes back through zero the other way. Since the ms1 chip can only trigger on the falling edge, this makes the MS trigger on the intermediate space between teeth on the wheel. Once you wire VROUTINV to TSEL, this reverses the signal, so the falling edge occurs when the VR signal goes from positive to negative through zero.

renns, I'm sure you could check on your scope and see that this is correct.

 

meh, I changed the wires around, found that they are reversed. I couldn't figure out which image to use from renns from faq or other. because there is 2 cas wire schematics on this forum and I wasn't sure which one to use as far as that went. I did see that you guys had to switch some wires. I also understand about the oscilliscope deal. Sometimes I really wish I had that kind of equipment. We had a handheld one where I took automotive technician training. Twas nice. Anyways, I figured things out. Thanx a ton you guys. All of the information on this forum and msforums made this possible for me. All to be done is fine tuning and (for me anyways) build myself the engine for auto-x that I have been planning
9.4:1 comp turbo. I wanted to get this in before I started work on that because I wanted a stable base map to work from instead of worrying about blowing sheet up.
In short, Thanx I had minimal problems considering this was in fact my first electronic piece of equipment for me to ever build *sigh* I have never spent soo much time soldering in my entire life. (next time will be much faster

Peace

Anthony Lleras

 

The switch can occur in the wiring too muy, this is what happened to me, I kinda forgot which was which when I threw it on again (serial chip problems first time). I only had two spade connecter on there so if I did reverse it it would easily be switched back to the correct way.

 

Ken,

I'm not questioning the TSEL thing, but once the box is mounted in the car, it's often much easier to swap CAS wires to test rather than disassemble the box. Is there any problem with leaving the TSEL to VROUT, and simply reversing the wires at the CAS? Seems like it all works out in the end, and the cpu sees the signal it needs regardless. This aspect of the build is not well documented. Might be a useful detail for the FAQ.

Roger.

 

well I mean the VR sensor is wired backwards... when I had mine on the corolla wired backwards it was much more susceptable to noise but then I had tsel wired to vroutinv.

I realise some people get the wires backwards, and I will be adding something to the FAQ about the TSEL to VROUTINV thing.

 

I wasn't saying the switch couldn't occur in the wiring... what I was saying is that I'm positive that the FAQ is correct about the colors of the wires on the CAS:

red is Ne+
white is Ne-
green is G+
white-black is G-

if switching the wires from this setup fixes problems, then you have TSEL wired to VROUT instead of VROUTINV.

I realise that it's easy to get the wires mixed up when going from under the hood to the ecu though, since mazda didn't think it was necessary to keep wire colors the same from one place to the next.

 

Yup! I have it wired to VROUT instead of VROUTINV. I didn't see anything saying that should be done. However, i may just have to take the ms out of the car and fix that. Perhapse that will fix any tach noise I see. Been pretty good so far though.

Anthony Lleras

 

yeah, I didn't realize that it wasn't in the FAQ because I had said it before *somewhere*

It's in the FAQ now.

 

Damn! Just when I thought I had searched through most everything... JK Thanx dude.

Anthony Lleras

 

After Tuning for a while, I have the fuel and ignition down to where it has lots of power. However, I can't seem to rev past 6k RPM. The tack does the jump up and down thing like it did at 3k with reversed wiring.(which was my bad) I am wondering if this could be caused by noise or if there is another explanation that could help. I have tried many different fuel and spark settings, just can't seem to escape 6k.
And I have tried pulling the CAS harness away from the alternator power wire to see what happens, same deal.
Any help is greatly appreciated


Anthony Lleras

 

Another thing. The rpm doesn't jump above 6k it goes up to where its popping and sputtering and drops down and jumps back up again. Not sure if that helps at all, but I figured I better say something.


Anthony Lleras

 

yeah that is probably noise on the CAS signal. I've never seen it come on that high though. Just to be sure, can you post your msq?

 

give me an hour, I will see if I can do that. Actually, just gimme a minute.

 

it won't let me post this msq
I am going to pm you ok.

Anthony Lleras

 

ok, after some fenagling I got it to be posted. Please don't laugh. Some of my settings are "different".

Anthony Lleras

 

Also, I just found that if I can get it to rev past 6k I don't have any break up after that point, just 6k rpm. So I figure I have to find something that is turning on or off, durring that time to see whats going on with it.

I will keep you posted.


Anthony Lleras

 

You might try the 024s9 style decoder. I think it's supposed to work better for CAS with missing teeth.

 

hmm, I will have to try that. are there any differences in the code other than the decoder settings?

 

oh by the way, I have 029s. it is the latest version on the msns-e site. I think I will try re-burning the firmware to the chip with the 029q2 instead and see what happens. I am also going to see what I can do with the cas wire shield and grounding it to the ms grounds.
Much I have to look into. I am almost inclined to think this noise could be caused by that rev-buzzer in the dash because it comes on at almost the same time. just a thought though.

Anthony Lleras