Lift off?

Today I managed to complete the wiring and get the engine started. I’ll let you read further in the Done section to get the gist of my troubles.

I’m dissapointed that the car is not mobile, as I promised my son Hamish that he could drive it to a car event tomorrow.

As Malcolm Fraser once said “Life wasn’t meant to be easy”.


  • Completed all the sensor wiring and Mini electrics.
  • Tested Mini electrics, lights indicators etc.
  • Tested MegaSquirt connectivity to all sensors and peripherals e.g. fuel pump, radiator fan…
  • Adjusted VR sensor to get it to trigger properly. Discovered it was out of phase, so adjusted the “Ignition Input Capture” value from “Rising edge” to “Falling Edge”. I used the TunerStudio “Tooth Logger” which showed two long bars instead of one long bar when it passed the missing tooth. This indicated that the phase was out. I also adjusted the position, of the VR sensor a little further away from the trigger wheel.
  • Checked and tried to adjust the fuel pump pressure using the FP test O/P in TunerStudio and the Fuel regulator. Fuel pump was making a right racket, much louder than the original SPI pump, and the return hose in the boot (trunk) was banging back and forth. I haven’t fully come to a conclusion, but I think the pump (a MPI/SPI replacement from Mini Spares) is a 255L/Hr 3Bar whereas the original OEM SPI pump I replaced was a 1Bar unit, flow rate unknown, but obviously less.
    I ultimately adjusted the regulator to ~ 12PSI, the gauge in TS was jumping around a bit… maybe +- 0.75PSI or more. Never had this problem with the original pump! My theory is that setting it to 12PSI which is 30PSI or so less than the MPI setting, the flow rate is overpowering the FP regulator causing it to fluctuate.
    I wired up the Main and FP SSR’s using the DIYAutotune wiring diagram. This allows the FP to be used both as in a ON/OFF and PWM mode without any wiring changes. So I might try bypassing the FP regulator and use  the ‘T’ piece with the FP pressure sensor, I have nothing to loose, and this was my original intent to use PWM to effect a returnless fuel system.
    Any ideas folks?
  • Noticed the Knock Sensor gauge was running around 60% when car was idling (surging more like it). I will turn this off until I get a stable idle and tune. Good to know though that it’s sensing something!
  • Started engine and got it to run sort of. It was running lean and hunting, pretty badly.
    I’ve abandoned trying to get it to idle, until I get the FP sorted. One interesting thing I tried to get it to run better was to change the injector flow rate from 622cc/min @ 12PSI to 400cc/min which equates to running the injector @ 5PSI. This richened it up a bit, but still had hunting. I’m confused; the injector is a brand new one, but could they have supplied an incorrect or badly flowing one?

    My Air Fuel and Volumetric Efficiency tables are pretty much as per my original tune, so why the lean running?

Eddie my dog, in his usual repose!
Eddie my best mate, in his usual repose!

To Do

  • Find a solution for fuel pump pressure regulation (maybe PWM) and flow.
  • Test injector flow rate, and check P/No is correct.
  • Test and set-up PWM for radiator fan control
  • Check timing and adjust the index position using TunerStudio to give the base timing value.
  • Adjust VE table to get it running OK
  • Take it for a drive to dial in VE table using TunerStudio’s VEAL.
  • Use and enjoy it!

Nice to do, but not required!

  • Fit the new heater. (Not doing until I have car on the road and tuned in… it is summer after all!)
  • Get a wheel balance and alignment.

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Installed the Wells TPS

I had some time today, so I installed the new Wells TPS. I had to change the wires around as the previous TPS had a CCW rotation or was it CW, depends on which side you look from I suppose.

Anyway, it is a little ripper, once I calibrated it to the MegaSquirt, it went from 0% to 100% and was completely repeatable. No more couple percent variation like I had from all of the previous TPS’s! Yeah!

Hopefully this will be the last I have to do with TPS’s for a long while.


Hall Effect TPS

Some of the things wrong with my existing/previous TPS’s were:

  • They wore out very quickly; being just variable resistors, constant movement around the idle and cruise portion of the track caused premature wear. This caused problems with MS.
  • They constantly needed re-calibrating in MegaSquirt. Repeatability was poor. After a day or even less I had to re-calibrate.

I have been looking for a while for non-contact TPS’s, utilising Hall Effect technology, but TPS’s that I did find were very expensive and/or not available locally here in Australia. Another issue is if I continue to use the SU carb as my throttle body (very likely) I have to use the same style as my current TPS.

All I knew about my current TPS was that it is standard fitment on many GM vehicles including the local GMH 3.8L VS, VT, VX, VY, WH, WK, V6 Holden Commodore’s and some Daewoo’s. I stumbled upon Wells Vehicle Electronics web site and discovered that they had the same part TPS112 and also they made brief mention that they also made non-contact versions! A brief online chat with a sales rep gleamed that all new TPS112’s were of the non-contact variety!

All the retailers that I could find in the US either didn’t know if their stock was the newer no-contact technology or they didn’t ship to Australia. Did a quick search on EBay, and presto found a local supplier Eagle Auto Parts that listed a Wells TP112 for AU $92.00. I guessed at that price it must be one of the new parts, as a standard no name brand goes for around AU $27.00, or at least I hoped!

Anyway, it arrived today, and a quick check with a multimeter confirmed that it was not a simple resistive TPS. I then connected it up to a 5V power supply and monitored the output with a CRO. Perfect, nice and smooth!

 Below is a picture along with the pin outs and MS Wire colours.

Wells TPS112 TPS
Wells TPS112 TPS