Does a larger exhaust cause boost spike? Why?

 

Only those manifolds that have the wg port on a single runner. For example, the Drag has the wastegate port on runner #1. The wastegate cant keep up with the pressure so you get boost spikes. Ive only experienced this with the drag manifold. I have a rev-hard and 3" exhaust and no boost spikes because the wg port is mounted inbetween the 1st and 2nd runner.

Now a good set up I recomend with the drag is keeping the 2.5" downpipe with a 3" exhuast. Ive seen good gains with this and you dont have boost spikes.

art

 

I think I may use your recommendation Art. I was thinking about getting a 3" downpipe, but maybe I'll just stick to getting a 3" Thermal instead. I should be getting my car back this weekend and then will be adding a boost controller. I should be running around 10-12psi and I really don't need it boost creeping.

 

Art, I don´t get it.

When I look at my DRAG manifold I can see 2 runners (cyl 1 + 2) are leading to the wastegate port. Perhaps you are talking of an old style Drag mani?!?!

 

 

So that would be over one runner?

 

correct, it's over runner 1 only.

 

this type dont spike with a 3inch down pipe

 

I would hope not..lol

art

 

Elephant trunk manifold!

drag gen 2 owning you! haha