Ok I've been searching but can't find what the reason to have a 4" downpipe would be. If it helps out alot I don't mind spending the money to have one fabbed up. Parts from atp turbo would be about 231 dollars before shipping and then the money to have it welded (cause I don't weld **cries**). Is it just a waste of money or will it get some descent gains? Basically what I will be doing is going from the 3" vband clamp to a 3" to 4" conversion and then 4in" tubing back to right before the presilenser where I would go from a 4 to 3" convsion and then 3" to 2.5" inch conversion and then to my presilenser. Or should I just stay with the 3" downpipe? Thanks for any input. Oh yeah this is going on a t61 turbo with a .96 p trim hotside.

 

I dont know if the 2.5 inch section will be able to keep up at all. you might very well get more gains from replacing the 2.5" part with 3" and leaving the DP alone.

 

well the exaust system is a 2.5" hks system so basically I would just be comming from the 4" downpipe back into the 2.5 inch hks system.

 

can anyone shed some light on the subject, thanks.

 

If you run the larger DP it will help some in response, even with the smaller diameter down stream. If it were me though I would find some way to ditch the 2.5 if possible.

-S-

 

so whats the best flowing catback out there. I have no cats and some straight through mufflers so it's definatley non restrictive but I see what yall are saying about a larger diameter catback. I've always heard though that dual 2.5" is better than a single 3" exhaust and lots of people run a 3" single but whatever yall think.

 

Just a FYI, I saw a 4" down pipe like the thunder fab one at Auto RND when I stopped by there. It is fking huge!

ATP Turbo is not far from my house either.

 

^^^^ that is what I would like to know. I have the dual N1. I would not mind runing a 3" pipe to it if I could.

 

damn thats the one reason I would love to live in cali. They have everything! yeah I bet a 4" downpipe would be freakin' huge and right now I don't really care to much about price so if it costs me an extra 100 or so to fab up a 4" and it really does work well then I want to go in that direction.

 

I have a 4" exhust system. i just need to wait on my laptop for my E6K to start tuning the damn thing. I will tell you in a week or two on how it responds and how loud it is on my GT42. I'm using 1 dyna max bullet 4" in/out muffler to one Apexi N1 muffler.

 

Well I'm probably just going to stick with the 3" exhaust. I don't know seems like no one really has a very strong opinion on the matter.

 

Go 3" all the way. There are gobs of 400whp rotaries running 3" all the way. I'd be thinking 3-1/2" for 400-500, and then 4". I'd get a resonated mid-pipe and single tip. Youd be fine, though, with the quieter duals, but I don't think they flow as well because they stop the vortex of exhaust gases.

 

On my FD, I whent from a 3" dp, to a 3.5" dp. I did'nt realy notice anything major. Maybe a bit faster spool, but the butt dyno could'nt tell anything up top. The only real numbers I have are from the track. On a 83* day, my car ran a 12.5 at 117 with my 3". On a 92* day my car ran a 12.45@117 with the 3.5" Same tune, bolth on pump fuel. So with a nearly 10* different tempature, the car made the same power. Of course, I'm not a profesional driver, so the change in numbers/times could be due to the driver. With my latest tune/3.5" dp, i ran a 12.2@122 on stock sized Faulkens. Take my ramblings for what they're worth- CJ

 

4" all the way with a 4" magnaflow is my route.

 

hum.............thanks pp13bnos I'll take that rameling into consideration This is a hard decision that i'm not sure what to do however I may just go with this 4" dp. I'm looking to get 450 to maybe a bit more then that so the more mods to get me to those numbers the better!

 

Why not go 2.5 inches? lol

 

4" downpipe and goes into the RX7.com race exhaust 3.75" is what ErnieT, Me, and some others run and it is not that bad as far as being loud. You wont have to worry about flow being an issue if you just get it done this way when you want more power down the road. Ditch the 2.5"

 

so general consesus would be to get rid of the 2.5 then huh. lol. Ok well maybe a single 3" corksport catback and a 4" downpipe?

 

hi hondahater, I have a customer that claims he made his 513whp with full 2.5" system that came with the car, he just fabricated a new 2.5" dump to mate up with the 1.15 housing. no cats though.

 

interesting. What turbo was he using? How was the responce? I'm guessing a 1.15 took a little longer to spool up then the .96 Anyways thats some impressive numbers! and on a 2.5 thats awesome.

 

It was t-61 same as yours but with WI so probably had some very agressive ignition tuning. and yea laggy till 4000rpm on stg2 with the garrett 1.15 housing. hes now gone with the smaller original mp1.00ar housing and is making full 3" system. so it will be interesting to compare the difference in hp with the larger system. but i dont see it being possible to make more especially with smaller ar. although both changes to the dump size and ar size will incourage better responce

 

well my alky injection will be here tomorrow or the next day so hopefully those numbers won't be far from reach with me because those are pretty damn inpressive. I may just go with a 4" downpipe and then mate it to the 2.5 I have now and later on go with some sort of 3" system. Wonder what kinda boost he was runnin'?

 

Seriously, save your money and hassel and just go with the 3" dp, which is what your V-band is. The performance difference between a 4"dp and a 3" dp (Not talking about a full 4" system) will be hardly noticable. It's highly unlikely that it would make the difference between winning or losing a race or being happy or unhappy with the car. Also, I'd love to know what the EGT readings were on that 513whp car running a 2.5 exhaust. If you knew, you probably wouldn't be so impressed with that, because you'd know that kinda heat will drastically shorten the life of your motor and turbo.

Reminds me of this discussion I had: https://www.rx7club.com/showthread.p...7+%27bout+egts

 

haha, its funny i also went to max for help on target egt tuning. very helpful guy.

 

Sean, don't you have something like a 5 inch downpipe on your car? One of the last few times I was at A-spec I think Steve said it was 5 inch. I snapped a pic of it. I'll post it up if you want.