tps accel

V8BUG · Post by **V8BUG** » Thu May 11, 2006 3:51 pm

283 sbc, tpi, MSII, embedded code 2.1, megatune version2.25b717

I ended up changing my cam after realizing that the old cam would never work with my stall converter. So I broke in the cam tonight and the engine sounds very good (no misfires, stumbling...) I have not driven it yet, just running in park right now.

So I get it to idle, and the same thing is happening. The led on the end away from the serial cable will flash and the idle surges. When looking at megatune the tpsAccel light on the bottom turns on very quickly and the pulse width increases shortly. when I was breaking the cam in running about 2000rpm steady the tpsAccel light hardly ever cam on, it just ran real nice like the idle should.

With the engine in gear the under a load the tpsAccel comes on but does not seem to make as much of a difference.

What causes the tpsaccel to turn on when I am not touching the pedal?
How do I fix this?
Should I load a newer embedded code so I can use those lag factor thingy's ?

any help would be great!

Jedrik · Post by **Jedrik** » Thu May 11, 2006 5:39 pm

your tpsThreshold is set to 24.5 so I am guessing the mapThreshold is what is trigering the AE
for a quick test put the proportion to 100% tps
and/or crank the mapDOT threshold up to maybe 100 - 200

see if that stops the AE from trigering.

V8BUG · Post by **V8BUG** » Fri May 12, 2006 3:14 am

I'll try that today.

I don't know if this would matter, but when I wired the 8 pin hei I spliced into the 5v ref for the tps, ran it through a relay and a oil pressure switch so there would 5v only when running. also when I calibrate the tps a window pops up and says the values "look funny" I just use them anyways. The tps works fine though, goes through full range and responds to my foot very well.

Jedrik · Post by **Jedrik** » Fri May 12, 2006 1:21 pm

when I wired the 8 pin hei I spliced into the 5v ref for the tps, ran it through a relay and a oil pressure switch so there would 5v only when running

eww I don't like the sound of that... and don't folow your logic.

The 5v ref is only on when Megasquirt is powered. This is the same power that runs the CPU. The last thing I would want is to have it in any way associated with an ignition circuit!

You want to have all the signal and signal ground wires as isolated as posible from other posible sorces of EM noise.

Having said that... your setup may still work. It just seems like inviting trouble.

Mike_Robert · Post by **Mike_Robert** » Fri May 12, 2006 3:07 pm

Jedrik, I used TPS vRef 5 for HEI bypass activation for 10K+ miles with no indication of trouble in any way. Of course, I scoped things before settling on that scheme, there was no bad stuff coming back from the module. Just a data point, and I fully agree with you that logic level MS connections should be kept away from ignition related devices!

-Mike

Jedrik · Post by **Jedrik** » Fri May 12, 2006 6:44 pm

Yes, I figured out what you were doing with the oil presure activating the ignition. Clever safety feature. It sounds like you found a solution that works for your particular setup.

V8BUG · Post by **V8BUG** » Sat May 13, 2006 10:43 am

quote: "for a quick test put the proportion to 100% tps
and/or crank the mapDOT threshold up to maybe 100 - 200
see if that stops the AE from trigering."

I did that and it just sat there and idle like factory!!!!!, the tps accel did not turn on at all!!!

Now the question, what is causing the map to turn on the tpsaccel?
I would like to use some map for accel enrichment, So how do I fix this?

also, regarding the 5v ref, I am going to leave it the way it is since everything (besides this AE problem) seems to be working perfectly

Any help would be great!!!

thanks

Jedrik · Post by **Jedrik** » Sat May 13, 2006 12:11 pm

You might play with TPS accel, just to see how you like it.
They both have advantages and disadvantages.

The problem with the MAPdot is that there is just naturally fluctuations as the valves open and close. I was getting inclreased fluctuations at higher rpm contrary to expactation. So great settings for starting from idle caused unwanted fueling at cruse. Maybe it was the intake resonating?

I havent persued the subject but maybe use a high MAP lag factor or try a physical damper... just a pleum with a restrictor. Many of the Individual Throtle Body settups seems to need this. So try a search for details.

MSII is still quite young. I suspect in coming months more AE options may be put into the official code.
Of course if you really come accross a quirk you cant work through, it is relitavely easy to modify the code. If you want ot get your hands dirty in that way...

V8BUG · Post by **V8BUG** » Sun May 14, 2006 5:18 am

sounds good.

I think I will try tuning the tps accel and try running 100% on tps accel. I have read that placing a small fuel filter in the map line may help, so I might try that also.

Thanks for the replays, I'll get to work tuning!