Ignition and TPS Errors

[Benzmac16v]

Hey,

I have been trying to tune my VE table (mostly using the tune by statistics feature, really need a co-pilot) and noticed my Ignition advance is, seemingly randomly, dropping to 10° just for an instant then bouncing right back to 'normal'. 

My other issue is that I have quite a noisy TPS signal.  Not quite sure what it is, seems like it could be some sort of electrical noise, but it is routed away form any HV wires and seems a bit too random.  Not really sure, it also seems to turn off ego correction every so often (sometimes very frequently and for very extended periods of time).  I tried bumping up the min dTPS/dt value to offset this and keep EGO running, but it still seems to do it...

My log is here (sorry for the file size, it was about a 300mi trip) http://www.rpi.edu/~smithj16/VEMS/v3.3_n001612-2010.07.06-00.59.25.vemslog  There is a marker on it, but the problems most likely exist on the entire log.

Thanks,
Jim

[rob@vems.co.uk]

first solve your electrical noise problem, check the way that the ECU wiring is grounded, and check your engine grounds - the cars we play with are getting old and their ground points rusting.
I have seen many OEM systems with shielded TPS wiring - the voltages changes down at part throttle can be very subtle, so you might be advised to do such a thing after the grounds are all checked.

[mattias]

Indeed, fix your TPS.

Is your MAP sensor properly calibrated? 20 kPa offset is way too much, if it's the 2.5 bar sensor then set the range to 250 kPa and 0 the offset and find your local atmospheric pressure.

You should also smooth out your VE map by A LOT.  At 1600 rpm/40 kPa you have a big anomaly. Just select corners around that (4x4?) which are decently tuned and press "I" to interpolate a new area of load cells.

I'd set TDC after the trigger to 60 degrees, first tooth to 13 and then rotate the ref tooth table one step. "0" should be in the top row of that table for faster starting.
Re-strobe the timing to adjust "TDC" as it could be 10 degrees off if my calculations were not correct.

I can't see why the ignition drops to 10 sometimes, but you should fix your TPS first.

You're running a lot of dwell, are you sure 3.78 ms is what the coils need? If sure, keep on doing it.

[Benzmac16v]

Haven't been doing too much work... we have had a couple 100 degree days out and that just isn't my thing...

I did do a little smoothing of the table.  I was hoping a 300mile trip would have produced a slightly less bumpy table but it seems ok for now.  But the major ones I try to remove, I must be getting some misses at low rpm high load because it likes to try and make those very rich, but it only contains a few data points so I can filter them out.  The lower load low rpm seem to have more data points and it really likes to make a few spots rich, so I must be getting some misses when the engine starts to fire again after no throttle.

I live basically at sea level and it says 101kPa for a pressure with the engine off, which would be right.  Also, some random website I just found says that the current pressure is 101.6kPa, so it should be pretty spot on...  It is the sensor that came with the VEMS unit.

That dwell time is pretty excessive... Never ment to keep it there...  When I was starting the car I wanted to ensure any issue I ran into was not due to spark but forgot to put it back to something more reasonable.   Looking it up though, thats even more than I thought I had put...  I thought it should have been at about 30kV but thats over 40kV...  That will get turned down to about 25kV or so as that is the minimum on the spec sheet and is well over the stock voltage (which was under 10kV).  Knocking this down could help with my tps signal... The coil I am using is the Bosch Wasted spark on the web shop.

How much quicker will the thing start up?  starts pretty damn fast right now...  But from what I gather, you are reversing the firing order in the ref table, which would require my 'first' tooth to be tooth 18.  Then you are adding 50 degrees of advance, presumably so that it can fire the 'first' time it sees the trigger tooth and knows its the trigger tooth.  This requires 5 teeth to be knocked off the trigger tooth number.  Makes sense to me...  But what values do I put in the ref table?  tooth 0 is no longer my trigger tooth...

I doubt it is grounding, but I will check it.  I bought a pre built wiring harness and the other sensors don't seem to be having the same issue (they should all ground to the same point if I under stand the wiring correctly).  My guess is that its picking up some noise from somewhere... worst comes to worst Ill throw one of those inductive 'dough nuts' we use at work on our signal lines in the HV stuff and see if that fixes the problem.  Hate to patch a problem like that, but if nothing else works...

Thanks,
Jim

[rob@vems.co.uk]

How old is the TPS?

[Benzmac16v]

Brand spanking new. Maybe 2-3k on it.

Jim

[mattias]

Sometimes a brand new TPS can be destroyed at the moment it is mounted because it is physically forced beyond it's end positions, they rarely have much margin above 90 degrees. Check that out.

The "VE tuny by statistics" is very nice, but you have to look at the figures in each square that you let it adjust. The number to the far bottom left is the number of hits, this should be high compared to others because then it's more likely to have had a steady load at that cell. The other important number is to the bottom right is the variance, only adjust cells with a low variance.

 Even if the algorithm drops hits due to acceleration enrichment and such, it can't ignore the lack of it. Given that you have no TPS you don't have any acceleration enrichment, which means you run lean during most transient events at low load - don't adjust those. Do slow sweeps across that area instead, steady part throttle and low gear helps.

You should set the range of your MAP sensor to 250 kPa, not anything else. Then re-calibrate the offset.

Regarding the trigger settings, because I recommended a shift in first tooth and an increase of "TDC..." by 60 degrees, you only rotate the ref tooth table, to compensate for the 180 degree shift. The ignition output table should match those settings as it is.  The numbers in the  reference tooth table are relative to the "first tooth", and never change. '9' is always first, it's the trigger tooth and in your case with a 36-1 wheel the next tooth in the table is always 18.

[Benzmac16v]

The noise appears to be mechanical...  With the engine off I was getting some (not nearly as much as when it is on...) fluttering of the signal while I was slowly increasing/decreasing the throttle...

Jim

[rob@vems.co.uk]

Noisey pot then, you know the thing - when your radio start to crackle and pop when you adjust the volume.
Nail that problem, then you can start tuning without fear of unwanted transients messing up the place.

[z0tya]

Even if the algorithm drops hits due to acceleration enrichment and such, it can't ignore the lack of it. Given that you have no TPS you don't have any acceleration enrichment, which means you run lean during most transient events at low load - don't adjust those. Do slow sweeps across that area instead, steady part throttle and low gear helps.

Is it filter the the fuel film enrichment too? And the deceleration is filtered too?
What is variance multiplier mean?

[Benzmac16v]

Well that suck... The pot is suck a pain to get to... Only place to put it was on the side of the throttle body where merc put the CIS closed throttle/wot switch... Shock is conveniently wedged between the intake manifold and tb...

Jim

[rob@vems.co.uk]

Thing is, it can still pick-up noise even when the engine is off, if its worse when the engine is on then it might still be due to RF/electrical noise.
Worth trying to clean up the signal or at least getting a scope on it to see what the noise source is.

[mattias]

Is it filter the the fuel film enrichment too? And the deceleration is filtered too?
What is variance multiplier mean?

I'm not sure on what exactly is dropped from the analysis, but de-/acceleration enrichment is dropped.

Variance describes how far from the mean value that the values are. A low number is good because that means that the lambda is usually off from lambda target by the same amount each time, which means the suggested adjustment is  likely to fix the tune.  (It's not a "multiplier", variance is a common term in statistics)

[Benzmac16v]

This is true.  I have a 'soft' scope that works really well when it works...  But sometimes the software really doesn't like to work.  So my plan is to try the softscope first, if that doesn't work I will just unplug the tps sensor and use an ohm meter to measure resistance and see if the resistance is fluttering.  If not then it is definitely noise and I most likely have a messed up ground that is screwing with my tps.

Worst comes to it, I can jack a scope from work to really see what is going on.

Jim

[Benzmac16v]

Well, had my crank trigger grenade itself not too long after my last post.  Clearance was always quite tight, but I figured it it was going to blow up it would do it a lot sooner than it did, or at least go when hitting a bump... not idling while parked like it did...  Tried to replace it, but it seems the 1/4in aluminum bracket might have warped. Don't have time to play with it much now but hopefully I will before I go back to school.

I was not getting any trigger errors before it failed, so I don't think it is related to my odd ignition spikes, but who knows.

The one time I did get a sensor in there without it self destructing it wasn't triggering.  The sensor worked (tripping it with a wrench would cause the fuel pump to turn on) but I couldn't tell what it was doing otherwise...  I was trying to use the trigger log feature in VT but I couldn't figure it out/my wheel wasn't triggering it anymore or could have been seeing the wheel instead of the teeth on the wheel...  How do you use the trigger log?  I just used 'V3' as the input expecting a live feed, but got nothing...

Jim