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I have two identical Mega Squirt set ups. Both use the same plug in connections to the car. Both have the same programs in them. One only gives me a problem with my tack in the car jumping around and not giving me a proper reading. The lap top that I have hooked up show all the read out to be smooth on both units. The lap top read outs match to what the car is doing perfectly on both Mega Squirt units. Only one give me this jumping on the tack. Any Ideas??
Thanks,
Kim

 

How are you driving the AutoMeter tach?

 

I have my Auto Meter tack hooked directly to the stock Mazda coil right behind the fire wall. If I remember correctly the green yellow wire on the leading coil. I have not looked at that wiring for two years the tack has all ways worked OK

. I noticed this problem when testing between my two Mega Squirt units making sure that both of them control the relays I installed. And the relays work fine, on off at the right settings.

I read some thing in another thread that maybe I have to adjust the pots. It starts fine, the lap top computer that is installed in the car shows fine with all gages. No jumping around at an Idle or if I rev it up. As I mentioned before one unit is smooth the other I put in is erratic. The car is a 1986 Gen 2 I am using the stock coils and low impedance injectors with the solenoid resistor pack and the Mega Squirt is operating everything.

Note I removed every stock wire from the car and rewired everything new. Also before this the car has run two race season quite well with only one Mega Squirt error. And that was a fried Q15 transistor on the secondary injector circuit. I’m quite happy so far.

This is a strange one for me.
Kim

 

The tach wire I am using, is a white wire with a blue tracer hooked to the trailing coils. I have flashed the firmware to the MS1, and still no change. I also traded out the MS1 chip that is in my 'good' computer (i.e. functional) into the other, and still no change. All of my tests indicate that the problem is on the V3 board.

What I found was that the tach on the dash is reading twice what is displayed on my laptop computer in the car. When I rev it up, the tach jumps all over, then settles back down - but always fluctuating at least a little and seems to read twice as much.

With this new information, can someone help point me in the right direction?

Best Regards,

- Kim

 

If it's reading twice as much, it's probably not the MS that's the problem... the tach itself probably needs reconfigured...

If the MS was doing something weird with trailing ignition, you'd likely notice in the way the engine runs...

Why not just use the MS itself to drive the tach? The MS is capable of driving a tach if you set it up right.

Ken

 

Both units are configured the same and are running the same firmware. One works properly and the other has tack issue, but was running fine last season. Your suggestion of making mega squirt operate the auto meter tack sounds like an good idea. Is there a online guide to do this? Thanks.

Kim

 

it's all in the manual:

http://www.msextra.com/manuals/MS_Ex...nual_Index.htm

 

Hi All,

I found the electrical drawing for the different ways to send out a signal to a tack. I am using a MS 1 chip on a V3 board. What I can not see on the electrical drawings for the Mega Squirt DB37 connector is the out put for a tack I see only the tach input. On the next page I see the U1. On this page I see no reference to a pin on the PCB as referenced in all the Tacho Output drawings that I found in the manual. From these drawings which would be the one to use? I hooked up my Auto Meter tack to the yellow wire with the blue tracer on the trailing coil to get it to operate.

I manage to wire in the operation of my three relays for fan and other items with the use of the Mega Squirt schematics. But I can not see how to tie in the out put for a tach. Are there other drawings that I have not printed off?

Best Regards, Kim

 

I do not know how to edit a previous post so here is another

Hi Again,

I was thinking back to my original problem. When Ken said that I should have a problem with my trailing ignition I just may. I have a very high idle to start with (1500 RPM) And I cut out my trailing ignition at 3500 RPM. So in the shop if I just rev it up it seams to operate Ok. So I test drove it this morning on the computer that was giving me a problem and it stumbled until I got the revs up. I have it wired both Mega Squirts to the car the same way as shown on Ken's thread at the top of the forum list. When I did so I ran 18 gage wire from the V3 board after LED 14 15 and 16 and before the transistors out to the appropriate coils via a three pin connector (Check connector OK). Both of my Mega Squirts are the same way. From all my test I have concluded that my problem is on the board to give me a problem one of my units. If this is the case what would be the most common item or items that could give me this type of problem? Also note after fixing this problem I would like to still set up Mega Squirt to drive the Auto Meter tach .

Thanks Guys

 

do the LEDs appear to be working correctly? do you have an oscilloscope you can use to check that you're getting good square_waves from the LEDs that control trailing ignition?

 

I used an oscilloscope in high school many many years ago. I do not have one or know anyone that has one. Now that you mentioned the LED lights I think I noticed the center LED not as bright as the out side two. It seamed like it could have been flickering some what. To be totally honest I can not say 100% only about 85%. My Mega Squirt is rubber mounted and elevated off the floor several inches on the passenger side floor in the foot area. In that area it stays dry in the rain races and cool from exhaust heat. I can see the LEDS out of the corner of my eye but I was not paying strict attention to them. Does that make any sense with the center one doing what I think it was doing?

Best Regards,
Kim

 

The center one controls coil select... it should flicker at idle (especially at lower rpms), and as revs climb, it'll probably be more dim than the other two LEDs.

Ken

 

In the case of the LEDS it seams to be operating correctly. I also adjusted the pots R52 and 56 but no change to the tach fluctuations on the dash. I have both Mega Squirt units out of the car and on the bench. Are there any test that can be done to compare the good unit to the one that is interfering with the operation of the tack?

 

Hi All,
I have tested the good V3 board in the area of the ignition outputs to the V3 board that is causing a problem with my tach on the dash. For these test I check the resistor and transistors for any difference in resistance or dead shorts. Both units showed the same values. At this point I can not continue due to the fact I am limited to electrical information on how these three systems can effect my tack fluctuations on the dash of the race car. Has any one had this problem related to the V3 board? As I have posted before every test pinpoints to the V3 board and not the car or the program or firm ware issues. The simple fact is one identical unit works fine and the other unit has the tach jumping problem. I am looking out there for help at this time.

Best regards all,
Kim

 

I have attached a data log of the race car idling. In some spots you can see areas were I rev it up. The car idle is not perfect but that’s not the issue. As mention before I have one Mega Squirt unit that operates with my tack on the dash just fine. Unit number two doesn’t. Unit two causes the tach to not show the correct idle and jump radically when revved up. Both units have the same firm ware and programs. I also swap the MS1 chip between the two units and still have the problem on unit number two. I adjusted the pots R52 and R56 in all possible positions and combinations no improvement good or bad. My limitations in the pot area was loosing signal and not having the car start up.

Today I changed out the spark plugs checked the resistance on all the wires between the MS unit and the car, it has great connections. Also good voltage when the car is running at both coils. Both sets of coils are giving great spark. I tested each lead by removing them and physically seeing the bright blue spark transfer over distance of 1 to 1.5 inches. The tack wire of the trailing coil is the correct one. It is the original wire that Mazda used as a signal wire which is the YELLOW/BLUE wire.

Have a look and see if any one has an idea. I’m royally screwed at the moment. I can not see deeper in to this glitch.

THANKS ALL

 

literally the only reason why the dash tach would work with one MS and not the other is if the ignitor/coils are not getting a steady signal from the MS for trailing. A bad CAS signal would show up as the MS tach bouncing around.

The software hasn't changed in that respect, so I would definitely recommend checking your pullup resistors, LEDs, and wires to your spare output pins.

Ken

 

If I look at the board and the drawing in the thread that you have posted, you are talking about the LED out puts for squirt, warm up and accell, correct? If this is correct, I have tested from the U1 chip out put to these areas and the resistance values are the same on all three. I tested from each side of each component on the board with an ohm meter test and they are all the same. The out put from the board to the end of my out put wire test the same. I all so checked the values of each section to the good MS unit I have and they are the same.

At this point I will perform the same tests to insure I did not miss any thing. But before I start please confirm the tests I described are correct methods. If not let me know what is the right way. I am sure it is on the board so that tells me I am not testing all the components or my tests are done incorrectly.

Thanks

 

The things I would check are that the pullup resistors are soldered well, with no shorts to other components, check that the wires from the negative leads on the LEDs have continuity out to the db37, and then check that there is continuity from there to the trailing ignitor plugs.

There should be little to no resistance from the negative leads of the LEDs to the ignitor.

Ken

 

I have tested from the trailing and leading coil plug in connection (Igniters) on the car back to 4.7 K resistors all carry the same values as the good MS unit (OK). I checked all the components on the V3 board R26, R27, R29, R24, R25, R28, D16, D15, D14, Q6, Q7, Q8 and the three resistors (4.7 K) that were add in. All check out with the proper values as to the drawing and have the same values as the unit that is working in the car. I removed the U1 chip and check for any resistance from it's pin hole to the to the R26, R27, R29 all OK.

Is it possible to have a transistor to check out ok as I am testing then as power is applied to it not to perform? The reason I ask is I have change the U1 chip with the good unit and no change. I know that the signal is getting to the R 29 and R27 resistors and they test fine for resistance all the way to the center of the transistors Q7 and Q8. This leads me to belief that the only thing that can turn off and on and falter is the next thing in line the transistor. I have not done any test for power in on the R24, R25 or R28 resistors when in the car. The reason is I'm not sure what values I should have there. Is it safe to do so if powered up and running? If the answer is yes which transistor should I change out?

Best Regards,
SCCA RX7 RACER

 

Hi all,
I changed out the transistors for the trailing coils still have the tack problem on the one MS unit. What test should I perform to find my problem which I have not tried yet? Any ideas please.

Thanks