High tooth count wheel not reving over 2900

[jlturpin]

datalog200807081919.xls

[grippo]

I ran your msq as is except for one change - alpha-beta-gamma went to last interval prediction as it is certainly not needed with 132 teeth. I was able to run it stably up to 5500 rpm. At 6400 rpm it was missing badly. This makes sense because the time between teeth at 6400 rpm is just under .1 ms, which is really pushing it to do error checking on the teeth.
I even ran it with alpha-beta-gamma at 5500 and it made no difference - it was still stable, but nevertheless I would still use Last Interval.

I didn't try running the rpm up and down, but I don't think this will matter - at high rpm there is not enough time for tooth timing to change from tooth to tooth.

I see by your rev limit you might be planning to go to 10000 rpm. For an ordinary street car 5500 is tolerable, but it won't cut it for a Porsche, so I recommend you go to a 36-1 tooth front mounted wheel.

As far as why you can't get past 2700 rpm - I don't know. You are definitely missing teeth as shown by the trigger+/- column counting down right after 2700 rpm. VR sensors are driven by the change in magnetic field, so the amplitude goes up the faster it turns. So does the noise. We are working on a small, cheap board that will analyze the signal and allow you to tweak the filtering. Then you would leave it in line with the VR sensor wiring. Everything else would stay the same. But that will only get you up to 5500 rpm.

[jlturpin]

Thanks for your time and testing my .msq I had also tried last interval, but noticed no difference. One problem with the 2700 rpm drop, which is about half of what you were able to achieve on the bench is noise. I am using the factory wiring harness. Even thought the VR sensor wires are in shielded, the coil wire, and injector wires go through the same loom through the firewall. My plan this afternoon was to Reroute a separate harness (out the window, under the hood for the coil and injectors. I am in the ITI field and am going to build a wiring harness for the injectors, and sensors out of CAT 7 cable. It is 4 pair, each pair is shielded, covered by a braided ground and insulated. may be a bad idea, but should eliminate and EMI.

I don't know if I have immediate access to a 36-1 wheel, but think I have access to a 60-2. I am only looking to turn 7K max, I think I had just raised the rev limit in the MSQ to eliminate that as being a brickwall during this stage of tuning.

If you feel that I'll be better served with the 36-1 wheel, I'll try to source one soon for testing.

Thanks again for your time.

[grippo]

60-2 is fine - people use that all the time.

[jlturpin]

I did the mod to the mS that is listed here http://www.microsquirt.com/viewtopic.php?f=87&t=23063 With a pot in place for resistance, I can cleanly run 5K rpm, much over that and I get trigger loss, but this is a huge improvement from the 2600-3000 limit I could run before. I have my rev limiter set to 5K, and it is 100% driveable no trigger loss, I have driven approximately 200 miles using the high tooth count factory ring gear (132), with this MOD, in commute traffic. I have tried adding in a cap, a .01 uf on the VR+ input, but this caused a loss of revving to about 4200 RPM.

[jlturpin]

After doing a lot of reading, and testing and primarily help from Bruce and SQLGUY I have successfully turned up my rev limiter to 6800 RPM with no TACH loss. Thats right, 132 teeth at 6800 rpm.

This was accomplished by performing the mod that Bruce posted, and the Mod that SQLGUY explained in the same thread, removing the capacitor at C30. I am still running a trimmer pot on the vr+ input now, but will try removing it when I have a chance.

132 teeth trigger wheel, running 6800 RPM CLEAN

[reclaimer]

jlturpin, are you still running this?

[robh]

last I heard- he switched to another fuel management system but still uses ms for datalogging I believe.

There are a few us that are using very similar setups though

[thenextdon13]

For those that are running similar setups to jlturpin, or for jturpin -

jturpin mentions using a pot inline to be able to adjust the resistance. Is this R26, directly inline with VRIN+?

Has jturpin or anyone else removed the pot / figured out what resistance is needed fior R26 on a 944?

Thanks!