[Diy_efi] Problem with TPS on aftermarket ecu

[Steve Ravet]

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org 
> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Robert W Hughes
> Sent: Thursday, March 29, 2007 1:46 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] Problem with TPS on aftermarket ecu
> 
> > I have a problem with my TPS and I'm running out of ideas. 
> Perhaps someone else on here knows whats going on.
> > 
> > The TPS is not reading correctly in the ecu. The ecu is a 
> Walbro BIKE400. Probably haven't heard of it but thats not 
> real important as it uses basically the same principals as 
> most ecu's when it comes to TPS.
> > 
> > I have wired the TPS correctly. It is a standard GMH 3 wire 
> TPS. +5v, GND, TPSsig.
> > 
> > The throttle movement is correct. I could calibrate the 
> opening 0% and 100% without problems. In the datalogging 
> software, the throttle movement works correctly. WOT logs 
> 100% throttle etc. The problem is that the 'dthrottle' value 
> does not change. It remains at 0 with the occasional movement 
> to 1 or so. Just like little blips of interference (noise). 
> Basically the ecu thinks that, although the throttle is 
> moving, there is no change. The result is no accellerator enrichment. 
> > 
> > If anyone knows why it is doing this, it would be a great help.
> 
> > I have a problem with my TPS and I'm running out of ideas. 
> Perhaps someone else on here knows whats going on.
> > 
> > The TPS is not reading correctly in the ecu. The ecu is a 
> Walbro BIKE400. Probably haven't heard of it but thats not 
> real important as it uses basically the same principals as 
> most ecu's when it comes to TPS.
> > 
> > I have wired the TPS correctly. It is a standard GMH 3 wire 
> TPS. +5v, GND, TPSsig.
> > 
> > The throttle movement is correct. I could calibrate the 
> opening 0% and 100% without problems. In the datalogging 
> software, the throttle movement works correctly. WOT logs 
> 100% throttle etc. The problem is that the 'dthrottle' value 
> does not change. It remains at 0 with the occasional movement 
> to 1 or so. Just like little blips of interference (noise). 
> Basically the ecu thinks that, although the throttle is 
> moving, there is no change. The result is no accellerator enrichment. 
> > 
> > If anyone knows why it is doing this, it would be a great help.
> 
> The simplest explanation is that TPSSig is either not 
> connected or poorly connected to the ECU.

If I read the original post correctly, the data log shows that %throttle
changes as he opens and closes the throttle.  In the same log, however,
while the throttle position itself is changing, the delta throttle value
doesn't change.  Damian, is this correct?

If so then the connection from the TPS to the computer must be OK.
delta TPS is a calculated, not measured, value.  It only takes on a
value while the TPS is changing rapidly so by definition is only non
zero for a short period of time.  My question would be what is the
sampling rate of your datalogger?  If you only get a couple data reports
per second then it's entirely possible that delta TPS is changing values
correctly but is being missed in the log.

Or, is there a constant that sets the decay rate of delta TPS that is
causing it to decay too quickly?  Is there a symptom (stumble or
hesitation) that accompanies the lack of delta TPS?

--steve

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