Spark timing that hunts and drops out at idle and TPS that stops reading position
Turbo Mini Forums

I am trying to sort out my Specialist Components Typhoon ECU/EFI setup for my K1100 head conversion and have some problems that are confusing. I have sent an email off to Simon at SC and he has been very helpful, but it's Friday and his local time is just before 9PM, so I don't expect him to reply before Monday next week.

I'm almost ready to put the Pertronics 123 distributor back in and figure out how to bolt a couple of SUs on the front of this thing...

The spark advance at idle is not consistent. It reads up and down a bit, which I expect is OK, but it will increase to 16383 degrees (!) intermittently and then stay there. The engine hunts up and down at idle and then will hiccup occasionally. The timing light confirms that the advance is off the timing marks and the hunting and hiccups seem to happen when the timing moves or drops out for a split second.

The TPS is new, but the throttle position reading on the ECU scope will get dodgey and then gets stuck at some partially open value when I open the throttle a bit and let it go to what should be an idle.

When I open the throttles the RPMs go up, but it will backfire slightly through the throttle bodies. And when I let go it backfires out the exhaust. This all seems like the spark is retarded and isn't advancing when the throttle is opened.

It could be that the wire harness for this system is faulty, but what are the chances that both of the sensor wires are not connected well?

Thanks in advanced for any insight you may have and I will attempt to answer any questions that come up.
Craig

There are two kinds of people in this world and I'm not sure you're one of them...

Have you checked the configuration options to make sure the ECU is set for the correct TPS and CPS?

Might be worth saving your map off and then downloading a fresh one from S.C.'s site.

The ECU is set for the K1100 TPS and SC's crank sensor set up (36-1 Ford style trigger wheel). SC loaded a map that was specific to my engine. I do have the maps they make available online for download, but they don't match my set up as close as the original is supposed to. I'm kind of reluctant to change the map at this point as I really am new to this and don't want to mess it up even more!

There are two kinds of people in this world and I'm not sure you're one of them...

16383 is 11111111111111 in binary so that is an error code of some sort. SC will be able to tell you.

Sounds like you tach input circuit is playing up.

I would check the VR sensor and wiring. Is it picking up interference? Is the wiring shielded?

Also check that you timing wheel is tight.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Can you log the information ? Log then view in some sort of graph viewer, and you would be able to see any anomalies with any of the inputs, and also the timing the ecu is commanding.

It could easily be a wiring or interference issue.

Mag/VR crank sensors do need to be twisted pair and shielded, and make sure they go nowhere near any HT leads.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

16383 deg (100000000000000 - 1 !)could also be the ECUs interpretation of -1 deg.

Have you got any negative timing values?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Have you reconfigured the ecu for the new tps? There is a procedure in the instructions on the software cd or web download, that get you to wsetup the voltage mine was miles out.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

After email with Simon at SC it turns out that most likely I have to turn the idle screw back to get the idle down to 1000 RPM and approximately 6 degrees of advance. It seems the ECU is retarding the spark to keep the idle down. I also am waiting to get a few connector contact pins and extraction tool so I can repair the 28AWG CAN Low wire that I pulled out of the connector while removing it to check connectivity between the TPS and the ECU. I should have known better to treat that connector with TLC as I used to work as a Manufacturing Engineer in the aerospace industry. Small wires don't take much load before they fail.

There are two kinds of people in this world and I'm not sure you're one of them...

Four pin TPS as originally used on the BMW throttles?.................................

Bin the fucker and buy a propper three pin TPS and adapt it to fit, then re calibrate the TPS.

I have no idea why SC persist in using the 4 wire BMW TPS in such an application

oh, man I had forgotten that little detail. Sprox is right, three wire TPS is sweet and simple.

Well, I spent $175 on the new TPS so I'm going to stay with it at least until it breaks. The wire I broke is on the ECU connector end and allows the ECU and my laptop to talk to eachother. Still waiting for UPS to deliver the contact pins and extraction tool...

Edited by CraigD on 23rd Oct, 2013.

There are two kinds of people in this world and I'm not sure you're one of them...

Well ok but to get it to work somewhere near right in the first 2 to 3 degrees of rotation you'll need to remove the metal inserts from the scew lugs and file the holes a little longer. This will allow the sensor to measure throttle movement from idle but it measures less at full throttle which is less of a concern. The thing with that tps is that it is two sensors in one. A fine scale for the first 10 degrees off idle and a course scale for the cruse and full throttle. You can link the two together with some resistors but that changes the sensor characteristic which would not normally be an issue but if you are using a map that was calibrated to use just the corse scale it might need quite a bit of re calibration.

It's been a while since I was last here with my epic problems. Thanks for everyone who lent a hand with suggestions and such.

As it turns out I have found that the crank trigger sensor is very sensitive to the gap between it and the trigger wheel. I shimmed it to just over .8mm minimum and just under 1mm maximum and it works fine now; the spark is even and consistent at all engine speeds. The TPS needed to be slotted more than what I thought was reasonable and I might just take a file to it a bit more to make sure it is in the high resolution section of the sweep.

As far as using a three pin TPS, I'm not sure if there is one that fits the BMW throttle body shaft like the original does. I may look around for something if I have some time in the future, but for now it's all good.

Once I had the sensors all gapped and set properly the engine idled well. It is still kind of rough at higher RPMs, but that could still be the TPS. Where's my bastard rat tail?

The only thing I don't understand is how my timing light shows the spark about 25 degrees retarded when the ECU shows it at 6 degrees advanced at idle. I also bought a new timing light that allows me to dial in the advance, but it doesn't pick up enough of a high tension signal from the spark plug wires to fire the light. When I input a crank offset of 30 advance the ECU tries to retard the ignition (ends up somewhere around 1 degree advanced) and the engine speeds up like I would expect it to with advanced spark. It shouldn't be running retarded 25 degrees!

There are two kinds of people in this world and I'm not sure you're one of them...

Is the crank trigger a VR sensor ?
If so, yes, they are sensitive to gap.
Next time I'll use Hall switches, like most modern OEM's now use, they are so much more gap tolerant.

Timing light issue is strange - I avoid the ones you can "dial in" the figure like the plague..... just using a coilpack will mess up their calculation.
But if the one you're using doesn't have that feature it should light up at exactly the time the HT fires (assuming it's an inductive pick-up off the HT lead).
Can you try it on another "standard" engine where you have a reasonable idea of what the manufacturer's timing setup is ?

I agree, it should hardly be running if it really is 25 ATDC

Schrödinger's cat - so which one am I ???

I have noticed (what I think) was some weird timing characteristics at cranking with the SC ECU, it appeared to me that the spark advance was 'scattered' during cranking, but that could just have been my missunderstanding. I never had any real time to confirm one way or the other, so i'm still unsure.

The non-adjustable light I have is a very good quality light that has never been off in all the years I've had it. I recently set up timing with a Pertronix distributor on a '63 Chevy II wagon I had; it was dead on for that one. I've never seen an offset with any distributor before this.

I also filed a bit more out of the TPS slots and made sure the minimum reading is in the fine resolution part of the range. It's running better than before.

There are two kinds of people in this world and I'm not sure you're one of them...

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

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Edited by Sprocket on 10th Nov, 2013.