Need throttle-position sensor

[syncroandy]

Having installed an AEB Leonardo LPG kit, which has a proper ECU with various inputs, I find I may need to rig up a throttle-position sensor onto my 2.1. It is optional, (I can simply configure the ECU to say I don't have one) but I should get better performance with one (eg. get proper overrun cut-off, richening at WOT).

Although the 2.1 has switches on the throttle body they don't produce quite the signal the LPG ECU wants. Ideally I need a potentiometer, rigged to produce 0-5v from closed to fully-open.

Does any one know of a source for a ready-made unit I can bolt-on, or will I have to make one from components ?

[steve8090]

Andy - you will need a spurious unit to drive this and a careful setup on the software, leave it connected for a while and watch the lambda reading, basically you will have around 83 degrees of throttle movement, it is not 90 degrees as some are because the throttle actually sits angled in its rest position, I have had a couple of these units for trial from http://www.bba-reman.com you will need to contact them and let them know exactly what you want, not cheap though, make sure when you mount it that you cut slots in the plate to allow you to alter tha plane angle on the plate, this will enable you to alter the injector angle in the software to eliminate any leaning off of the gas at high revs, two parameters are crucial in this type of setup, tickover and 3000rpm, don't ask why 3000rpm its just what is recommended by most LPG tuners, hope you find what you need and unless you have an engineers key for the software there is very little you can alter apart from the initial setup.

[syncroandy]

Cheers Steve,

Have you used the TPS units on a waterboxer or a.n.other vehicle ? Ideally the TPS wants to fit coaxial to the butterfly spindle itself, but I may have to settle for it being mounted separately with a 'meccano' linkage. Which configuration have you used ?

I didn't fully understand your mention of 'injector angle', can you put it another way ?

On the setup, my understanding is that at idle, I do the basic adjustment using the screw on the vaporiser whilst checking the lambda. At 3k rpm, the mixture is set dynamically by the ECU based on the lambda. There is also an override function for stepper position over/under the default at both idle and non-idle.

Andy

[steve8090]

Used a TPS on other vehicles I'm afraid, the open loop suits the waterboxer so well I have not bothered to fit anything else, by the way if you were to fit a TPS to it then you could in effect use a Dream C injection setup too. The TPS I have used in the past came with a claw type fitting that clamped to the spindle, only thing I had to fabricate was a backing plate to mount it and adjust the angle.
"Injector angle" this is the amount of gas supplied by the ECU, on full throttle you will be putting something like 4.8v through the TPS, the ECU picks this up and adjusts the gas accordingly, however if you were only putting say 3.6v through on full throttle then the ECU would think you were in mid throttle and you would end up with a lean hot engine.
When you initially set the ECU software you will run the engine at over 2000rpm you will then see two scales appear as the unit self calibrates, a figure of around 144 as default is a good set for the waterboxer, but it could vary, when on idle you then adjust the vapouriser so that the floating needle is somewhere within the blue bar, not the outer red bar, similarly at 3000rpm you will rotate the TPS until you have the correct fuel mix for the engine, the stop switch on the waterboxer can be used to indicate throttle stop and negates the TPS if you cannot get an idle voltage of 0 - 0.1v
Hope this helps and the description is a little better.