Power loss after each shift under moderate load and moderate acceleration

[macsnjets]

Hi, I have a 2008 GTI BPY engine with DSG. I’m getting a power loss with each shift under moderate load and acceleration. It’s happening when it shifts for about one second and then recovers. It occurs in the range from about 1500 rpm to 2500 rpm. If I go up three gears it will happen at every upshift. Rpm will drop approx 500 at the shift point and it’s accompanied by what sounds like an air discharge and almost screeching in nature but I do feel a loss of power. Overall I do get a lot of air sucking noise which might be my CAI. I initially thought maybe a boost leak but correct me if I’m wrong, these cars aren’t really making boost in that rpm range. On three occasions I did get what almost seemed like the engine just choked, sort of like a backfire.

if i accelerate light everything is fine and if I go hard above 3000 rpm, it takes off like a rocket, nice and smooth like a gti should be. Also downshifting to get the rpms high results in normal behavior.

now, the car has 114k miles. I’ve recently fixed all my system lean and system lean at idle codes. There are no other engine codes for weeks now. I’ve done plugs, coils, timing belt, water pump, cam follower, pcv, pcv hoses, new diverter rev d, brake booster hoses, resealed vacuum pump, DSG service. Only mods are a Unitronic CAI which I installed to make it easier to find my many air leaks and a GFB+ diverter valve which I thought would help. I’m sure I could use a carbon cleaning at this point.

could it be a N75 or wastegate problem? I was also thinking did I get a bad diverter? What can I try at this point? It’s driving me nuts.

thanks for any input

 

[BurgerGuy]

I too had the GFB+ diverter valve, but removed it down the road. The stock rev. D DV on its own is just fine for this car. The GFB+ was actuating too quickly for my Unitronic tuned K04 and, at times, actually caused the car to suffer from compressor surge because the DV would shut before all the unused compressed air had been recirculated back to the turbo inlet. If the DV is shut and the throttle plate is closed, charged air only has one place to go, back the way it came. Look up compressor surge videos to see if that might be what you're hearing. It kinda sounds like a squeak/honk in the intake system.

 

[macsnjets]

I too had the GFB+ diverter valve, but removed it down the road. The stock rev. D DV on its own is just fine for this car. The GFB+ was actuating too quickly for my Unitronic tuned K04 and, at times, actually caused the car to suffer from compressor surge because the DV would shut before all the unused compressed air had been recirculated back to the turbo inlet. If the DV is shut and the throttle plate is closed, charged air only has one place to go, back the way it came. Look up compressor surge videos to see if that might be what you're hearing. It kinda sounds like a squeak/honk in the intake system.

Compressor surge sounds more like a flutter. I don’t get any flutter. If you’re familiar with turbine engines it sort of sounds like a bleed valve opening and dumping compressor air. I also had the same problem with the new stock rev d DV.