Let the drama begin…
I live to fiddle and optimize right up to the last minute, which usually results in a very busy last weekend, or even a busy day before an event. This year, the plan was to do it differently, getting it done earlier. Sunday night, the week before the event, I just had a wheel alignment and swap over to the new tyres/rims – less than an hour, easy right.
Tuesday rolls around, get the car out in the late arvo and let it idle for 10 mins while I wash it, checking that everything is working as it should, all is good.
Drive off, try to climb the first hill right near home and can’t get over 30 kays an hour – its running super lean. Shut it off, get out the laptop, can’t see anything wrong with any temps, TPS, pressures are all good, hmmm. Reset the min and max throttle positions (a mistake in the end), added 10% more fuel and tried again, it wasn’t great, but was better. Cody was operating the laptop, got him to push it to 20%, then 30% and finally got the mixtures right(ish) and we kept going to scrutineering, with all of the possible scenarios running through my head of what has changed that has caused this. Fuel pressure reg maybe – yeah, hopefully thats it.
We get through scrutineering, all passed, and we continue on home. Once home, get the fuel pressure guage out and hook it up. Hmm, fuel pressure is perfect, right where it should be. What have I done wrong when I re-wired the car, as thats the major thing that I’ve changed.
Wed night was a rally panel meeting, so no time to look at the car. Thurs night, hours checking everything, can’t find anything wrong. We’re leaving for the rally tomorrow, and I’m all out of ideas. Got in contact with Shannon at Tune Corp to see what he was doing in the morning. I was fortunate enough that he had enough time to have a look first thing Friday morning. We strap it onto the dyno and everything looks ok, other than its running lean (once my edits to the tune were removed).
Shannon suggested that we check the injectors, they are easy to get out so step one was to test them. The injector on Cylinder 4 was down on flow. Got a spare one and re-tested them and we now have 4 that are flowing the same. So pleased that we found it, running it like that flat out would have resulted in a lean cylinder and a blown engine.
Popped them back in, and he runs it up again. Its better, but its still not good – so there is still something else going on, from releif to despare in moments.
Shannon starts the process of re-tuning it.
When he turned the dyno cooling fan on, it was strong enough to push the bonnet up against the stops on the hinge. I figured as its only 4 bolts, it was easiest to just take it off. I quickly remove the bolts and an I was lifting the bonnet away the car stops – the dash and everything is off – total electrical failure?
With a worried look on his face, Shannon asks me if I touched anything – No. Heart sinks – all my new wiring and something has failed.
Shannon says it looks like the kill switch has failed, everything is off. Then it dawns on me that the outside battery kill is at the base of the windscreen. I pressed it when taking the bonnet off. Turn it back on again and its all fine – heart attack avoided.
After 5 minutes of tuning he soon notices that everything he is setting is exactly 1 column offset from what is already in the fuel map. Shannon has started to peice the problem together.
In looking at the data in the ECU, then next item to look into was the TPS voltage was reading 0.08 volts. Then when I wound the idle down a bit it didn’t change voltage. Repositioned the TPS to read about 0.5 volts at idle, so that we now have some more travel in the sensor. With this discovery, it dawns on me that about 4 months ago I moved the throttle wheel (where the cable attaches) across a bit as it was getting very close to rubbing the throttle body itself. In doing this, I must have moved the positions of the throttles, but as I had the sensor at its lower limit already, moving it has repositioned it, and now the ECU is seeing the same voltage on the low end, but the throttles have moved position.
With quad throttle bodies and no manifold, TPS provides the load signal, so moving it has confused everything. If the TPS was not at the bottom of its travel, it would have been fine. I effectily created a dead spot where 0-4% actual throttle was all read at the ECU as idle, so it never put enough fuel in. I noticed the issue at light throttle, and never pushed past that – If I had the car probably would have come to life again.
With the TPS moved, and min and max throttle reset in the ecu and she did a full power run with no issues. It was good to hear her scream and shoot flames again. Shannon spent a few moments making some tiny tweaks to fueling, and did a final power run to check it. Still the same HP as last time, she is FIXED!
Another case where a whole range of little things causes a big problem. If I had set the TPS to its current position when I first built the car then my other changes wouldn’t have caused a problem, which would have meant that I would not have messed with other things, that just all made it all worse. You learn new things every day, normally by messing it up 🙂
I was so stressed out that I wasn’t going to be able to figure out what was wrong, a huge weight was lifted.
I can’t that Shannon enough for helping me out, could not have fixed it without you mate!
So, after having had enough drama and stress for the month, its time to go home, finishing packing and start the drive to Manjimup. All this and the event hasn’t even started yet!