My car is a CQ20V and with around 1600 miles under its belt is running pretty well following an engine rebuild. Fitted to the engine are: brand new 034 injectors, Tommis adjustable cam pulley adjusted to compensate for maximum skim the head came with, cylinder head is nicely ported with different possibly supertech valves (i didn't get the head done it came on a spare engine), both manifolds matched to head, standard MAF, tubular exhaust, decat pipe and Tony Banks 2 box stainless exhaust.
Yesterday i went for live remap and the following checks were made prior to getting the emulator plugged in and showing how the engine was using the standard map.
Fuel pressure. 3.5 rising to 4 bar without vacuum.
Fuel flow. 2.5 Litres returning to tank per minute
Lambda control. value of 1 and reading 10 times every second, old one was only managing 5.
Idle C.O - 0.5%
HC - 95ppm
VAG fault code reader plugged in. no faults.
Coil voltage. 13.4 with engine running
Alternator output. 14.2v
Spark plug operation. consistent across all 5 plugs, coil building spark nicely - leads all good.
TPS range. no problem. 3.3v at full scale deflection.
MAF receiving 5V and responding but unsure of voltage output (beware not all operating MAFs are equal - some output more signal than others)
Compression. 14.7 BAR across all 5 cylinders with only 5% max variation.
Cam timing all spot on all the marks.
Inlet air / vacuum leaks. None.
Exhaust leaks. None.
Results were interesting. Performance was pretty good mid range but on full load, the emulator was showing that the engine was only making use of 90% of the fuel map. It was interesting to see what was going live as it happened but no matter what was done with the throttle the car just wasn't using all the map. AFR was dropping to around 12 - 12.5:1 as it should when the throttle was pressed all the way down but then quickly returned to 14.7:1 or as near as damn it as revs built to red line. The emulator was able to make changes to the map in the first 90% so was talking and amending things properly but couldn't do the last bit.
Much head scratching followed and the current working theory is that somewhere the car isn't breathing well enough for enough air to pass over the MAF to allow the last 10% load fuel to be generated. There are no obstructions in the inlet right from cold air hose behind headlight, through filter (which i will change as although it wasn't that dirty, for the price of a new one it is easily eliminated), through the michelin man hose and through the throttle body. both butterfly valves are opening fully to their stops on full throttle.
I need to do some investigating before my return visit to finish off.
The only thing which was harder to check was the internal condition of the exhaust. It is only 4 or 5 years old and the center section is straight through with inbound and outbound pipes in line with each other, the pipework over the rear sub frame mirrors the original and the back box has offset in and out pipes leading to a single pipe splitting to 2 tail pipes.
Is it possible that the back box simply can't pass enough gas when on full throttle and high rpm? The offset nature of the pipes leads me to believe there is some kind of chamber in the silencer which the gas needs to navigate before exiting rather than rushing straight through. My idea is that now the head flows well, the exhaust which previously did alright with standard amount of air passing through is now struggling and becomes a limiting factor. There is no crush damage anywhere on the system but I've currently got no idea if wadding is escaping into the gas flow anywhere.
Appreciate your thoughts!
Yesterday i went for live remap and the following checks were made prior to getting the emulator plugged in and showing how the engine was using the standard map.
Fuel pressure. 3.5 rising to 4 bar without vacuum.
Fuel flow. 2.5 Litres returning to tank per minute
Lambda control. value of 1 and reading 10 times every second, old one was only managing 5.
Idle C.O - 0.5%
HC - 95ppm
VAG fault code reader plugged in. no faults.
Coil voltage. 13.4 with engine running
Alternator output. 14.2v
Spark plug operation. consistent across all 5 plugs, coil building spark nicely - leads all good.
TPS range. no problem. 3.3v at full scale deflection.
MAF receiving 5V and responding but unsure of voltage output (beware not all operating MAFs are equal - some output more signal than others)
Compression. 14.7 BAR across all 5 cylinders with only 5% max variation.
Cam timing all spot on all the marks.
Inlet air / vacuum leaks. None.
Exhaust leaks. None.
Results were interesting. Performance was pretty good mid range but on full load, the emulator was showing that the engine was only making use of 90% of the fuel map. It was interesting to see what was going live as it happened but no matter what was done with the throttle the car just wasn't using all the map. AFR was dropping to around 12 - 12.5:1 as it should when the throttle was pressed all the way down but then quickly returned to 14.7:1 or as near as damn it as revs built to red line. The emulator was able to make changes to the map in the first 90% so was talking and amending things properly but couldn't do the last bit.
Much head scratching followed and the current working theory is that somewhere the car isn't breathing well enough for enough air to pass over the MAF to allow the last 10% load fuel to be generated. There are no obstructions in the inlet right from cold air hose behind headlight, through filter (which i will change as although it wasn't that dirty, for the price of a new one it is easily eliminated), through the michelin man hose and through the throttle body. both butterfly valves are opening fully to their stops on full throttle.
I need to do some investigating before my return visit to finish off.
The only thing which was harder to check was the internal condition of the exhaust. It is only 4 or 5 years old and the center section is straight through with inbound and outbound pipes in line with each other, the pipework over the rear sub frame mirrors the original and the back box has offset in and out pipes leading to a single pipe splitting to 2 tail pipes.
Is it possible that the back box simply can't pass enough gas when on full throttle and high rpm? The offset nature of the pipes leads me to believe there is some kind of chamber in the silencer which the gas needs to navigate before exiting rather than rushing straight through. My idea is that now the head flows well, the exhaust which previously did alright with standard amount of air passing through is now struggling and becomes a limiting factor. There is no crush damage anywhere on the system but I've currently got no idea if wadding is escaping into the gas flow anywhere.
Appreciate your thoughts!
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