Saturday, 10 August 2013

Playing with the throttle body setup.......

I had trouble setting up the TBs when I built the car but drew stumps when I got the setup good enough to pass the IVA emission tests.

I've now driven 3,000 enjoyable miles in the car but have never been confident that the setup was right.  My concerns are: 1) lots of popping/banging when de-accelerating especially in 3rd or 4th gear. 2) Judder when in 4th or 5th gear when driving through 30 mph zones with no throttle - clears when accelerator is used but requires running in 3rd gear to stay in the speed limit. 3) The idle appears to be slightly high at ~1,000 rpm when the ECU was set to 900 rpm

When I setup the car originally I set the TBs at 4.5 kg/h having closed all the idle by-pass screws but the left hand inner TB which was 1/2 a turn open as advised by Guy at Omex as the starting position.  Once I'd got the TB balance the TPS reading was 11 and Throttle Max 195 so I set these in the ECU calibration.  Guy at Omex said that 11 was too low and suggested that I should adjust the TPS to give an idle reading of ~20 but having achieved the IVA emissions requirement I wasn't prepared to do anymore.  Mark at Westfield also suggested that the problem with the driving in 30 mph zones might be associated with the ECU switching off the fuel and that he sets the factory cars at 4.0 kg/hr.  In addition, Terryathome's video suggested that all the by-pass screws should be closed as the starting point for balancing the TB.

I followed T@H's initial setup and balance the TB's at 4.0 kg/h.  Once I'd done this the TPS was still reading 11 so I adjusted the TPS until it read 21.  I then set the ECU calibration file to the new idle of 21 and Throttle Max of 200.

And the results........mixed.....the judder has gone and the car is much nicer to drive through town, the popping/banging when de-accelerating appears much reduced but has not gone completely and the idle is now around 900 rpm so all three of my issues have been solved or improved.  However, I've also noticed that the car is now slightly hesitant when accelerating from lowish revs in 3rd and 4th gear, less of a problem than the previous issues but not ideal.

Time for a trip the NMS, so I need to start saving my pennies.......................

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