talk to me about External Wastegate with 2.5inch catback

[PIONEER]

I'm cooking up an idea about going total sleeper on the cressida using the stock 2.5inch Catback mated to the Straight 3inch downpipe going to the turbo elbow with the internal wastegate welded shut..

I drill a hole pre turbo on the manifold, and run a pipe to a external wastegate from there.

My reason for doing this is the constant drone of the 3inch exhaust. You think if I'm dumping to external air, I still need a full 3inch setup? I'm thinking the 2.5 should be enough if the internal wastegate is closed..

Give me some input on this.

 

[IJ.]

Pioneer: Depends on boost and flow!

My car with the GT30R was choked to 9psi by the IC being too small.

I ran it with a full 2.5" system then changed to a 3" and saw no difference at all but I suspect if the IC wasn't choking it there would have been.

Maybe ask BIC if he can make you a DDP with a 2.5" flange ?
(will save on an ext gate)

 

[PIONEER]

I was thinking about drilling a hole in the manifold right before the turbo and run a dump tube out of there and hook it up to a external wastegate. The BIC style downpipe still utilize the stock CT wastegate flapper.

 

[IJ.]

I was just thinking of simplicity, it's going to be a bit of a sleeper so not all out for power so the CT WG should cope fine at those flow rates without creep!

I drove a Cressy when I was looking for a beater and the only reason I didn't get it was lack of grunt a GTE would have fixed that nicely!
(I needed something turn key there and then)

 

[spipedong]

Is there any reason you don't want to use an electric cutout on the DP? That would give you a quiet ride around town, and an immediate wide open, straight 3" dump when you want it.

 

[drjonez]

just run a massive DP w/the stock cat back + an electric cut out. max power, max sleepitude.

 

[Blue87T(Dan)]

That would be my recomendation as well.

It has worked out great for me so far.

I make about 30rwhp more with the cut out open.