Currently I have the stock Greddy downpipe to Berk 63mm HFC and greddy 70 single. I will be updating the downpipe to 3" but it seems retarded to go from 80mm (3") to 63mm HFC to 70mm single. I live in socal but will be putting my stock downpipe/cat for smog. ATP has a 3" high flow cat also for 150 but its vband and I will have to have more flange/piping work done and I still want to be able to put things back for smog...

Thanks for your opinions

 

I would say option one or two, no need to really buy a whole new exhaust. What about boost creep do you think the new DP will fix the problem?

 

I would go 3" all the way through. Turn the boost up if you are on watermeth or E85, no boost creep.

Cant wait to see the results of this. Ill be doing a 3" and extending the length of the wastegate piping to see if I can avoid the torque drop I am getting in the high rpms.

 

3" DP with the ATP HFC and VBand the entire thing

 

Leaning to go with either option one or two at the moment.

I was going to have my local muffler shop make the downpipe (in mild steel) due to cost... I would still like my tuner to make it all stainless though but thats going to cost more than triple the cost.

 

How much louder is my car going to be with no cat compared to a high flow cat?

 

I have a berk HFC and compared to my 3" TP it a pretty big differnce, I can really tell. I just put the berk on to go through emmisions and can't wait to get the TP back on. It is a bit louder, a bit more rasp, and stinks more. But it's worth the trade off IMO. I jumped 30hp increasing boost 1psi and adding a 3"TP. So I figure the 1psi is 12-14 HP. The TP must have been the rest.

I hope this helps.

 

Have you verified the flange fitment?

I was thinking that I would get the flange, 3" 90deg elbow, 3" 45 deg elbow, 3" x 3' straight pipe, 2 O2 bungs and (2) Vband sets from ATP.

From the Flange I will go Vband to the 90 elbow then down to the 45 elbow, then make a straight shot back to the intermediat pipe. B/C I want to be able to easily put the car back to stock, I will cut off my flange on the test pipe and weld a Vbange flange to it and then bolt it to the cat back.

I have not verified fitment of any of these pipes yet but believe this will be very close. I plan to cut and tack the system in place then remove it for a profesional to do the welding.

 

After reading this I'm just going to go 3" downpipe strait to my 70 single.
Thanks for the info.

 

I havent personally verified the flange but ATP told me it was the correct one and it appears correct.

I'm going v band right off the flange to my downpipe which will be connected to my exhaust via the normal exhaust flange. I'm also fitting a 3" flex in the downpipe. Hoping to get it all done next week and then get on the dyno ASAP. Got to call the tuner today and set a date.