Lost Boost

[pnyxxpress]

OK.. As usual I had to come over the buick site to get my answer. Seems no one on the Ford sites can answer this or maybe I'm just to impatient....Here the scoop.

I recently switched my exhaust.

Old Exhaust= 3" down pipe to a 2.25" y to a 2.5" high flow H pipe to a 3" duel catback system. The car was making 11# of boost.

New Exhaust=3" down pipe to a 3" single high flow cat to the same 3" duel catback system. The car now making 9# of boost.

Did I create more back pressure and this why I'm seeing a loss in boost. If so what can be done to correct this problem. I'm running a T63e with deltagate Mark II wastegate.

Thanks in adavance for any and all replies.

Mike

 

[Reginald West]

Sounds to me like you created a more free flowing exhaust system ( releived a restriction). Do you have a controler on the waste gate? If so turn it up. If not there is a manual adjustment in the center of the delta gate screw it in and the boost should go up.


REG

 

[ijames]

I think that you are seeing that even a "high flow" cat is still not nearly as good as empty tubing . By the way, what was the 2.25" y-pipe and H-pipe for if you only had a single 3" downpipe? Try putting in a 3" test pipe to see if your cat is really the problem, then decide which way you want to run.

 

[pnyxxpress]

ijames,

The H pipe is how the mustang is setup from the factory. The Y pipe was part of the turbo kit so you can use most of the existing dual exhaust. This setup caused everything to hange lower than I care for so that is why I went with the single 3".

My intention is to eventaully go with a 3" without a cat but emissions are due and right now don't have the funds to fabricate a single catless system, so the setup will be with me for a few months.

I have heard 2 sides to this story that is why I asked the question.

One side says as Reginald West did. I freed up some restrictions and that caused the boost to drop. And yes, I can crank it back up but want to do some research first to fully understand what has taken place.

The second side of the story is that I created more back pressure and the wastegate spring and diaphram are being forced open premature of my initial settings due the spring pressure not being adequate.

I guess I could try to crank it up a bit and see what happens but really didn't want the extra strain on the system if is in fact it is the later of the two.

Thanks for the replies,
Mike

 

[ijames]

I was just curious. Seems wacky to use a y and h pipe on a single turbo single downpipe setup. What do you do, add a crossover and cap the non-turbo side manifold end of the y pipe, then plumb the downpipe into the turbo side manifold end of the y pipe?

Anyway, as to boost and backpressure, I can tell you from repeated personal experience that removing post-turbo restriction results in more boost. Started with stock cat, boost went up 3 psi when I put on test pipe and back down when the cat went back on. Later, when the cat was breaking up inside, the boost went up 5-6 psi when the test pipe went back on. Same deal with a 3" THDP and cat, cat lowers boost about 2-3 psi over a test pipe. Yes, you can turn the boost back up but not all the way (if you were octane limited with the test pipe) and you will make less power than before from the increased pumping losses.