Saturday, September 7, 2013

Injector change

So, a little more progress. We managed to sort (I hope) the fuel system problem - by the looks of the tank, pump pickup and filter, the fuel system contaminants were trapped in the fuel rail/regulator itself.

As a result, I obtained a replacement rail. Originally I was looking for an AU rail and regulator, hoping to pick up some OK injectors at the same time; instead I located and acquired the rail, regulator and injectors from a BA XR6 Turbo. These injectors are still a bosch item, still have the EV6 connector (so plug right in) and are actually the same injector on the non turbo as the turbo cars.

  The difference between the turbo and non turbo BAs is in the regulator. The non turbo run a 300kpa/3 bar regulator, and the turbos run a 400kpa/4bar regulator. This means the turbo flows 25% more fuel with these injectors (above the manifold pressure) than the non turbo. In E-series setups, the standard regulator is a 270kpa item and XR's run a 300kpa reg with the same injectors. For some time it's been possible to lean out XR's slightly by running a 270kpa reg and actually make a little more power provided decent quality fuel (hey, it's rough but supposedly works) - a side note is that the EEC-V is pretty smart and actually learns around things like this (or like running AU injectors and reg with an EL tune) given 1-200kms of driving and a working o2 sensor.

While you can get away with running marginally larger injectors and the ECU will learn around it (or it will be just "o.k.") you can't expect to get away with a massive change. For this reason, traditionally you need to upgrade to an aftermarket ECU to change injectors - or use some sort of interceptor to scale the injectors or airflow readings (some Japanese cars use these methods) when upgrading injectors. In this instance, standard E-series injectors are approx 19lb/hr and from what I could find (ex Bosch and the part number on the injectors I now had - the BA ones are 213 grams/min or 28.175lb/hr@ 270kpa. Of course I don't have another regulator that works other than the 400kpa one that came with this rail so I had to adjust for that difference - 400kpa vs 270kpa is a factor of 1.48148x meaning the BA injectors in the rail with turbo reg are effectively 41.74lb/hr injectors - more than double the flow of the standard ones!

Now I say 19lb approx on the standard injectors. I adjust the tuning on my falcon ECU using a J3 chip from Jason at who has been very helpful any time I've needed assistance understanding the processes involved in adjusting the tune. The beauty of this system is that it takes about 1 minute or less to send the tune to the chip and no more than a minute to re-fit the chip to the ECU - add to that I have a switch to effectively disconnect power from the ECU and it makes removing/reprogramming and testing adjustments a very fast process indeed.

The J3 tune I am using (in TunerPro) has a variable called injector slope mapped. This handy variable is set in my base tune to 18.79lb/hr. The Bosch documentation states that my factory injectors are a 19.8lb injector at 270kpa. The reason for this difference I believe is due to the fact that the injector flows published by Bosch are tested using N-heptane and not normal fuel.

I initially set the ECU with 36lb (the internet consensus for turbo injector flow) and after removing all the spark plugs and cleaning them with a wire wheel, the car started and ran, however would not re-start unless the fuel pump was switched off while cranking until the engine sounded like it wanted to start (lucky I have a switch for that!) which to me indicated that there was way too much fuel. Further research garnered the figures above and I tried 41.74 which allowed the car to start without any application of throttle however resulted in some hesitation upon throttle input (to me indicating a slightly lean condition) - it's to be noted that I have no intention of doing any power runs with the car in this condition, purely moving it around the driveway at home so I can get other vehicles in and out of the shed or to test things like the new power steering lines (which I now know work fantastically, along with the alternator charge wiring!!).

Further research lead me to the N-heptane/normal fuel discrepancy. The original injectors were rated at 18.7 in the tune vs their published 19.8lb/hr. Could this mean that standard fuel flows 94% of the published N-heptane flow? I have applied this to the ECU with a resultant reading of  39.42 (I set it to 40) and it now starts and idles without throttle, does not seem to hesitate on throttle input, has decent torque for reversing up the hill that forms part of my driveway, although does still tend to have issues with immediate re-start (overfuelling) - thankfully, now that I have an alternator charging the battery I'm able to turn off the fuel pump when shutting off the engine, then not turning off ignition until the engine starts to stumble. This seems to allow re-starting of the engine without issue.

The next step (while the front is removed) is to make radiator hoses for top and bottom - the top I can make from a commodore top hose as they are the right size and have a nice sharp 90 degree in them as required. The bottom will require more work and may need a metal adaptor made up. The side/reservoir feed will be a bit more difficult and is likely to require modifications to one of the headlight brackets and some tricky hose routing. We'll see how that goes when it comes time! Also to be done - making a thermofan fit. We've got one we modified early to be as trim as possible, it's now a matter of making some sort of bracketry to fit it to the car behind the front grille and in front of the radiator. Hopefully it fits just right!

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