VT V8 Dropping TPS & MAF Reading

[Rhysk94]

Hey Guys,

I have the misso's old mans VT V8 back on the dyno after it has been manual converted.
Every run around 3800 rpm the TPS & MAF reading drops straight down to 0 and obviously power tanks down.
I can't find anything in the bin file that would sort it, was wondering if anyone had any idea at what it could be.

Have attached a picture of the dyno runs so you can see and have also attached a log file.

Cheers once again

[VTXU8]

Look at your Maf readings just before tps drops off. It maxes at 8500hz then starts to drop of as revs keep rising then tps goes. Manifold air flow reading goes crazy too.

[VTXU8]

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[Rhysk94]

Yeah the maf should go a lot higher than that tho
The bin/xdf went up to 16000hz from memory

[VTXU8]

I was just saying perhaps the maf or power to maf is faulty. At that peak, the G/S goes from approx. 195 g/s to 65678.0 g/s. I can't remember if the maf and the tps share the same 5v. Stock Maf will peak around 10,000Hz

[Rhysk94]

Ah yup,
It was only that run it ever did that, all the others were normal like the log I have attached in this one, Can still see the maf and tps drop off with no weird spike.

[Rhysk94]

Reviving this post..
The other day I had a VX L67 do the exact same thing...
90% of the time it did it at the exact same rpm, then everyonce in a while it would rpm out till almost limiter then do it again.
This VX was dead stock tho as opposed to the VT 5L that was manual converted

I have looked everywhere on the datalog and the tune file, cannot find anything.
Anyone brighter than me have an idea on what could cause this?

Cheers

[Knackersjewels]

Has to be wiring, surely

[antus]

Looking at this again in the screen shot above it looks like no data was flowing from around 21 seconds to 28.5 seconds. Those long straight lines in that time period tell me there was no ALDL flowing between the PCM and your PC. So, maybe it was an RFI problem and the data packets that are way out of spec might have been garbage data that just happened to pass the very weak checksum test (1 in 256 corruption probability of a false OK from an 8 bit checksum). If there was big RFI from spark jumping where it was not mean to, that could have also been affecting other sensor data. Its also possible the PCM crashed and reset itself but if that happened, I'd expect it to be back online in less than 6.5 seconds.

[Wade]

Not a ground issue?