# No tach signal



## ps2375 (Aug 13, 2003)

We are at the point of starting the car. We have discovered we have no tach signal. We have an MS1v3.0 with the MSnS code loaded. The signal comes in on pin 24 of the harness unlike on the v2.2 it is on pin 25. The diagram for the v3.0 board has it on pin 24 as well. I built the board, and am now going to recheck all the steps for the tach input for the "Hall sender" option. Are there any "tricks" or things I need to know? I also installed the pull-up mod for driving an MSD control module, is this needed or can this be eliminated, since I don't know if this is or could effect the input. A quick inspection seems to show the proper jumper configuration for the Hall sender option and not the VR option. On my MS1v2.2 I made no changes to drive the MSD, so I'm thinking it is not really needed. Any ideas?

And I just verified that the tach input works on the stim(v2.2) in the "pnp" position. Did I do something wrong? Does this mean that the input should be on pin 25?


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## ps2375 (Aug 13, 2003)

I think I am going to install the IGBT components and trigger the MSD with that. But, that still doesn't account for the tach input.


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## ps2375 (Aug 13, 2003)

So, having thought about it, just trigger the MSD off of the pin w/o the pull-up ckt should work and jumpering pin 25 over to pin 24 via the IAC1A pad to either "Tach Select" or "Optoin" for my tach signal. We are not using any idle control and def not the IAC stepper motor.I'll check to see if the "IAC1A" pad goes anywhere, I don't think it does as the manual calls for jumpers to coneect those to JS0 thru JS3.


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## need_a_VR6 (May 19, 1999)

The IAC pads just go to the DB pins, they need to be jumpered to something to make use of them. 

Generally on a V3 I remove XG1/2 jumper, tachselect to xg1 and to a 1k to 5v pullup on optoin. 

You did something to the 2.2 to drive the msd, remember that didn't have 'spark' 'stock'  Just do the same mod but apply it to the V3.


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## ps2375 (Aug 13, 2003)

I didn't build the v2.2, it was a patatron unit we bought from a user on the 'Tex a couple of years ago. I did post a pic of it a year or so ago asking what mods it had on it. I just finished jumping the IAC1A to "Optoin". That should give us a tach signal.


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## ps2375 (Aug 13, 2003)

And I put this back onto the board, MSD output for v3.0 PCB. I think we should be OK now.

The part I don't understand is why does the diagram show pin 24 for input, yet the harness has it on pin 25, it is a DIY harness and they don't show any other for the v2.2 or v3.0 PCB's?


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## ps2375 (Aug 13, 2003)

After much more confusion, we found we had the wrong plug for the dizzy, not deep enough,:banghead:. then we think we have not one but *two* bad dizzies as we still don't get a tach signal from the either dizzy but can get some input by "tapping" the ground wire to ground. I have another (third) dizzy at my house that we will try tomorrow. So, I think the MS box is OK and now the wiring/connector.


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## need_a_VR6 (May 19, 1999)

The DIY harness should have a single conductor with a shield going into pin 24..


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## ps2375 (Aug 13, 2003)

need_a_VR6 said:


> The DIY harness should have a single conductor with a shield going into pin 24..


It does have the shielded cable, but I'm sure it went to pin 25. We checked the pin-outs for it.


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## ValveCoverGasket (Mar 20, 2002)

ps2375 said:


> It does have the shielded cable, but I'm sure it went to pin 25. We checked the pin-outs for it.


i think thatd be a first... but its possible they got an improperly made batch maybe?


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## need_a_VR6 (May 19, 1999)

Seriously, the install I just did used that harness and it definitely went to 24.


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## ps2375 (Aug 13, 2003)

I'll check it again tonite when we try the last dizzy.

Now that I think about it, on my v2.2 diagram it has the tach signal coming in on pin 25 and the v3.0 has it on pin 24 and I do think mow the cable is on pin 24. And as the stim works on the v3.0 board and I don't remember if it works on my v2.2 patatron unit(and the diagram is what came with that unit). Between the connector at the dizzy, the bad dizzy's and the two diff diagrams, I may have over complicated and confused myself.....


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## ps2375 (Aug 13, 2003)

need_a_VR6 said:


> Generally on a V3 I remove XG1/2 jumper, tachselect to xg1 and to a 1k to 5v pullup on optoin.


Let me get this straight, I understand the "remove XG1/2 jumper, tachselect to XG1" part. The "a 1k to 5v pullup on optoin" part is supply 5v to optoin thru a 1k resistor?

On the v3.0 PCB schematics it has a note 1 that is very different than what the assembly guide says about VR input and Hall sender input. Can you clarify that note?









And after plugging both dizzy's into my car, they both do work. But the stim doesn't work on my patatron board and does work on the v3.0 board. But the dizzy's do not work on the v3.0 board and if we input signal on pin 25 on the patatron bd, the dizzy do work in the car we are doing the install on. WTF?


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## ValveCoverGasket (Mar 20, 2002)

ps2375 said:


> Now that I think about it, on my v2.2 diagram it has the tach signal coming in on pin 25 and the v3.0 has it on pin 24 and I do think mow the cable is on pin 24. And as the stim works on the v3.0 board and I don't remember if it works on my v2.2 patatron unit(and the diagram is what came with that unit). Between the connector at the dizzy, the bad dizzy's and the two diff diagrams, I may have over complicated and confused myself.....


thats only because patatron made his more complicated than they needed to be, and seemed to set up a precedent among the vw community of using pin25 as the tach input on v2.2 boards... this creates confusion as many of the older wiring diagrams floating around on the forums here show that as well...

you should really be using pin 24 though as it makes life much easier


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## ps2375 (Aug 13, 2003)

Well, I can agree with that.


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## ps2375 (Aug 13, 2003)

I suppose I need a diagram of the pullup ckt, and I can pick up the parts after work and get it modded.


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## need_a_VR6 (May 19, 1999)

http://www.msextra.com/doc/ms1extra/MS_Extra_Ignition_Hardware_Manual.htm#hall

Use V3 5v low to high


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## ps2375 (Aug 13, 2003)

Thankyou, that looks like what we need.:thumbup::beer::beer::beer::beer:


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## ps2375 (Aug 13, 2003)

So, went to Radioshack yesterday and bought some resistors. And when I went to use them, they were 4.7K ohm instead of 470 Ohm. I pulled them from the correct bin, but didn't check the package for correct-ness, my mistake. So, tonite after work, that'll be my first stop and a solder job, and we should be set. While I was at it, I also put in the stuff for the Launch Control.


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## ps2375 (Aug 13, 2003)

Thanks for the help! We now have a tach signal and the best part is it RUNS!! Amazingly the intake is nearly as loud as the exhaust. We do need to get the battery fully charged or replaced as it seems to have a hard time cranking, as if it has more compression than it should. It has stock pistons and a MLS ABA HG, so maybe a slight bump, but nothing extreme.

And for "proof" video:
It lives! Fixed link.


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## ValveCoverGasket (Mar 20, 2002)

awesome stuff! :thumbup:


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## ps2375 (Aug 13, 2003)

Well, we went to the dyno on Saturday and set about to tune it. Had a hard time getting thru a bad miss-fire from3500-4500 @WOT. Then we finally found that "RPM based" accel enrichment was way better than "TPS based". Minimized the miss-fire, but was never able to eliminate it. Once it got past it, it was incredible! We spent 2 hours trying to tune, and on the last pull to see what we had, at about 5700 rpm something bad happened. It either dropped a valve or broke one or something else. When we tried to pull the plugs, #4 would not turn easily, so something hit it and prolly mushroomed it. We brought it home and put it away. We'll have to pull the head to see what happened. And with no budget for repairs, it'll be sometime before it will be going again. Our race season is over before we had a chance to start it.:thumbdown:

The miss-fire seemed to be only at WOT(hard to tell as I wasn't the one in the car), and getting the accel enrichment correct seemed tough. What do you out there use on ITB setups when running alpha-n? I am looking for some tips that I/we can learn from about tuning this setup. As I said, when it got past the miss-fire, it was a rippin' motor. We have/had Bosch platinum plugs in it and the stock 16V coil w/ an MSD6. Do we need a Blaster coil? Is there a harmonic that causes it to go rich/lean and cause the miss-fires? I haven't found any VE or spark tables for alpha-n yet. And we did try more and less advance in that area to see if we could get around this and also more and less fuel. It did seem to be very sensitive to 1-2% changes to the VE table.

Any additional info on tuning something like this would be very helpful. And as the car is not liscenced, and as loud as it is, street tuning isn't much of an option at this point. And the dyno operator/owner has lots of experience tuning cars, but none with MS, he did move us in the correct direction initially and over-all, but the miss-fires seemed to just stay and all efforts to stop them had no effect.


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## need_a_VR6 (May 19, 1999)

I've *never* had good luck with platinum plugs. Either straight copper or the super fancy iridium stuff for me. 

The more lairy the motor the more likely rpm based accel will work well for you. For any of that to work though the VE table has to be good.

One thing you might have been seeing is intake harmonics. If your torque curve is wavy, you will want to put load points on the high and low spots to be able to accurately fuel it. However, only big changes in A/F should effect power, not what amounts to 1-2% ve unless you were way rich or lean.


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## ps2375 (Aug 13, 2003)

*EDIT* They could be the "iridium" plugs, they are a single electrode plug which I prefer in any motor over the multiple electrode plugs. I will have to check when we do the autopsy.(I mean tear-down.)

And coming into and out of the miss-fire "zone" the AFR was in the 13's. Then it would shoot lean and the come back down when it got past it.


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