Howdy,
Just wondering if you guys can help educate me a bit before I get my car re-tuned mid next week. Your insights would be greatly appreciated re what I have been told is a compressor surge problem that is 'normal' ...
Just to put in context, I had vf34 twin scroll conversion on my 04 auto a few weeks ago- did all the recommended mods to run it on E85-202awkw. Was tuned with a TMIC but I have since put a FMIC on after much fiddling, hence the re-tune next week.
Essentially, I have been told I am getting compressor surge from the tuner that did the conversion- I get it under partial (light or moderate) and WOT what seems like almost all the time. I am pretty sure it has been getting progressively worse over the past 2 weeks since picking up the car. Occassionally, there is only the intake noise and in this dynamic it launches really hard and smooth (puts a smile on the face ). However, when there is the concurrent chh-chh-chh-chh sound in addition to the intake whoosh, it doesn't pull very hard and is annoying me as it is most of the time. In this mode it only feels like it is running at about 50% capacity compared to when it does not make this sound.
It is my understanding from what the tuner said that if the turbo makes boost around approx 3300 and the throttle is only partially open then pressure builds in the intake, hence the surging. However, when it doesn't do this, particularly under moderate or WOT, it is completely different. It is the inconsistency that is also doing my head in.
I have tried to research and watch youtube vids of cars with compressor surge and the vids I have seen seem more severe or sudden drop in power and none of them sound the same, whereas with mine, it sounds like a steam train chh-chh-chh sound (sorry about the corny attempts to explain sound!) and seems to rev slower and not pull anywhere near as hard from initial depress of throttle onwards, which is when the chh-chh-chh sound occurs (ie almost immediately after the throttle is depressed).
I am hoping some of the above may be a tuning issue in relation to the change in IC system (? I don't know) but it was doing the same thing before I took the aftermarket TMIC off (but to less of a degree, which is when I got the above explanation from the tuner- he said it was normal and that it can only be heard now because of the CAI). The partial throttle explanation for the surge makes some sense to me but I would have thought that it wouldn't do it under moderate or WOT or at least not the majority of the time? I also don't understand why sometimes it doesn't surge at all and pulls hard?
When I spoke with the tuner about it I initially thought it was the BOV as it sounds very similar to the purge when coming off throttle but he said it is definately not the BOV.
Any info or guidance would be great as to what is going on. It would be nice to have some knowledge about what is going on when before I speak with the tuner next week.
Cheers