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Not sure if this should be in ECU/Tech or here since it's related to GTI's, Anyway...
Just a word of warning if you are planning to use an atmospheric or semi-atmospheric BOV on you Polo GTI (or 1.8t for that matter). I recently had the ECU re-tuned and not long after fitted a Turbosmart Kompact dual-port bov as a replacement for the stock diaphragm diverter valve.
I set the dual-port onto the hardest setting with 50% of the flow on closed throttle going to atmosphere and 50% recirculated back into the plenum. No check engine warnings were displayed and the car only displayed the occasional backfire on closed throttle so I thought I was sweet... But there were much bigger problems brewing as indicated by the VAGCOM readings...
I started to notice that timing and boost were being pulled by the ECU at ~4-4.5k in 3rd and 4th gear quite often (I thought it was the ambient temps being QLD summer) but merging onto the freeway Thursday I heard the dreaded 'tap tap tap' of detonation. I lifted the accelerator and began to do some more testing and every time I would hear a 'tap tap tap' then the ECU would cut the boost and timing.
I had Jimmy do some logging when the car was serviced on Saturday and he noted that the timing and boost were being retarded significantly in the load gears (3,4) but we could not figure out the exact cause. He seemed to think it was air fuel mixture as everything else checked out fine.
As only the BOV had been changed since the ECU tune, I removed the trumpet and blanked the atmospheric part off. All of a sudden the car pulls hard and clean in all gears right through to redline.
In the end, the problem seems to have been that the A/F ratios were rich-as on the 1-2 and 2-3 gear changes as half the air was exiting the system through the BOV (as correctly detected by O2 sensors in the exhaust) so the ECU leaned the mixtures off to compensate, resulting in knocking in the 3rd and 4th (load) gears as the ECU tried to figure out what the hell was going on!!! This all but sent the car into limp mode.
It was only a bit of luck and the ECU's knock sensors that saved me from splitting a piston or something worse.... So you have all been warned, don't use an atmospheric or semi-atmospheric BOV on these engines!!!
Jimmy or others, please feel free to elaborate some more if I have left anything out!!
Just a word of warning if you are planning to use an atmospheric or semi-atmospheric BOV on you Polo GTI (or 1.8t for that matter). I recently had the ECU re-tuned and not long after fitted a Turbosmart Kompact dual-port bov as a replacement for the stock diaphragm diverter valve.
I set the dual-port onto the hardest setting with 50% of the flow on closed throttle going to atmosphere and 50% recirculated back into the plenum. No check engine warnings were displayed and the car only displayed the occasional backfire on closed throttle so I thought I was sweet... But there were much bigger problems brewing as indicated by the VAGCOM readings...
I started to notice that timing and boost were being pulled by the ECU at ~4-4.5k in 3rd and 4th gear quite often (I thought it was the ambient temps being QLD summer) but merging onto the freeway Thursday I heard the dreaded 'tap tap tap' of detonation. I lifted the accelerator and began to do some more testing and every time I would hear a 'tap tap tap' then the ECU would cut the boost and timing.
I had Jimmy do some logging when the car was serviced on Saturday and he noted that the timing and boost were being retarded significantly in the load gears (3,4) but we could not figure out the exact cause. He seemed to think it was air fuel mixture as everything else checked out fine.
As only the BOV had been changed since the ECU tune, I removed the trumpet and blanked the atmospheric part off. All of a sudden the car pulls hard and clean in all gears right through to redline.
In the end, the problem seems to have been that the A/F ratios were rich-as on the 1-2 and 2-3 gear changes as half the air was exiting the system through the BOV (as correctly detected by O2 sensors in the exhaust) so the ECU leaned the mixtures off to compensate, resulting in knocking in the 3rd and 4th (load) gears as the ECU tried to figure out what the hell was going on!!! This all but sent the car into limp mode.
It was only a bit of luck and the ECU's knock sensors that saved me from splitting a piston or something worse.... So you have all been warned, don't use an atmospheric or semi-atmospheric BOV on these engines!!!
Jimmy or others, please feel free to elaborate some more if I have left anything out!!
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