Problem with calibrating tps accurately

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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jbull
Posts: 2
Joined: Tue Apr 15, 2008 10:18 am

Problem with calibrating tps accurately

Post by jbull »

Hi,

I am in the process of hooking up my MJLJ with a tps.

The software connects to the tps and I think I have it wired up correctly.

I drop 4 volts across two of the wires from the tps and 2 and - 2 across the others.

When I depress the throttle the voltage across one pair goes from 2 to 4 while on the other it goes from -2 to 0.

In the software when I use the calibration routine it correctly detects the beginning and end of throttle travel and interpolates the scaled value between these two points.

The problem is that the voltage increase does not appear to be linear and when I open the throttle a tiny fraction the load indicated rises to 50% almost immediately goes quickly up to 70% with the final 30% of the load being distributed over the remaining 80% of throttle travel.

Anybody got an idea why this might be happening?

When I measured the voltage across the wires it didn't seem to change in the same way.

That is measuring the voltage right by the tps rather than at the mjlj end. I suppose I could start by checking the voltages were the same up by the connector.

brentp
Site Admin
Posts: 6282
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Some thoughts:

You might have a non-linear TPS, and perhaps it's just harder to observe the effect using your meter.

can you physically rotate the TPS's mounting? If so, you might be able to adjust the TPS so that at idle it's in the more linear part of the range.

Another thing I would try is to hook up a known potentiometer to see if the behaviour changes.
Brent Picasso
CEO and Founder, Autosport Labs
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jbull
Posts: 2
Joined: Tue Apr 15, 2008 10:18 am

Post by jbull »

Cheers,

Will have a play tonight and see if I get the same effect through the whole range of movement on the tps.

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