944 Turbo hesitates in 2nd gear under full throttle

[951's]

Hello all,
This is my first post so I wanted to thank everyone for helping me out on my issue below.

I have an 88 951 with:
3 inch Lindsey racing pipe
Billet Fuel pressure regulator
Wider Throttle body
Autothority Racing Mass Air Flow sensor
Boost Enhancer
Autothority stage 2 chips

About a month ago, I was driving and the nice woosh sound that i would get when i would shift from the turbo turned into a fluttering sound when I would shift. I was told by my Porsche mechanic that it was a bad baffle in the Lindsey racing pipe. He also replaced a few vacuum lines in the car along with the BOV and the car really moves now but still makes the fluttering sound because I have the race pipe still on. The problem is that i can floor the car in first gear and the car will pull all the way up to 6K rpm with no problems, I will then shift as fast as possible and then floor it in second and the car will pull crazy hard all the way to about 4K rpm and then the car will take about 2 seconds to get to 6K rpm. If I am just driving around town in second and floor it, the car will pull all the way to 6K rpm with no problems. It only has this issue when doing a straight line push as hard as possible. If i shift slow to second and then floor it, the car is fine. Its almost as if the car is sitting at that rpm and just slowly pulls to 6K rpm when it used to spin the tires and race to 6K rpm from 4K rpm.

I am not sure if the blow off valve is bad and the air is not escaping the turbo all the way before i gun it again when i shift real fast or if it is a vacuum line issue. If you could provide any help, I would really appreciate it. Thanks so much for your help.

[wild man]

The fluttering you are hearing when lifting off the pedal when shifting is an indication that the compressor is stalling due to a bad BOV (technically a bypass valve), or else it is not receiving the vacuum signal that is supposed to open it. But the symptom of it having power immediately after the shift, and then losing it when rpm's go higher, is unusual. I may be unrelated. Make sure your vac lines are correct and have no leaks in them.

[951's]

Hi Wild Man,
I found out that the injectors needed to be replaced on the car. I had that done today and i have been able to have power all the way through the rev range now.

I had the BOV valve and vacuum lines replaced on the car and it is still making the fluttering sound. Could this possibly be a bad baffle in the exhaust or could one of the new vacuum lines be bad? thanks for the help.

[nize]

can you provide a video/recording of the fluttering sound?

i find it unlikely the lindsey exhaust would cause a fluttering sound.

can you test it by removing the muffler to see if it still does it?

[951's]

Hi Nize,
I will try to up load a video of the fluttering sound. It just all of a sudden started to do it one day and it has not stopped since. Its only after i shift. It used to make that nice whoosh sound. My mechanic has spent weeks on the car and he is stating one of the baffles in the exhaust is shot but i am skeptical on this. I actually do have the stock exhaust lying around so i will try to get that on this weekend. If the sound is still there, then its obviously not the exhaust like you said. Ill let you know how that goes. Thanks for your help on all this.

[951's]

Hi Nize,
I was not able take a video of my car because it is still sitting at my mechanics place, but i was able to copy this video from you tube on here. This is obviously not my car, but it is making the exact same fluttering sound that my car is making after i shift. I was looking around on line and i saw a Lindsey bypass valve replacement for my car. ($150) If everyone on here thinks that the bypass valve is shot on my car after watching this video, which bypass valve do you recommend? Thanks and sorry for this crude video, but its making the same noise. Let me know. I am starting to have some major doubts that the problem is in my exhaust system Thanks.

http://www.youtube.com/watch?v=MkkA-vfGWg0

Youll have to copy and paste the video into your tool bar. Thanks.

[nize]

yes it sounds like the BOV/bypass valve/recirculation valve.

you can get a billet aluminum BOV for less elsewhere;
Which BOV to purchase?

[951's]

Perfect. Thank you very much. I will let you know if the fluttering goes away. I am pretty confident it will. Thanks again.

[nize]

by the way, you might want to ditch your 'mechanic' and get one that doesn't lie to you.

[951's]

Hi Nize,
I apologize that i have not been on here to respond to you about the new BOV that i ordered. Unfortunatley, my car was broken in to and i have been waiting for a new window and the police to finish up on checking out my car. I did finally have a chance to have a new BOV aftermarket put in, and the car is perfect. No fluttering at all. You were 100 percent right on this. Thanks so much for your help.

[nize]

good to hear! thanks for the update!