Ed260Z Posted February 6, 2006 Share Posted February 6, 2006 I've been reading a few books, and gone through more threads than I can remember on this subject. This should probably be on the exhaust forum, but I'm more interested specifically on the RB DETT motors, obviously. It seems, based on the books I've read the the best size would be 3.5", but that's going to be a tight fit under the car. And if you use 2 pipes, 2.75" pipes would work. The questions are; Is it a good Idea to run 2 separate pipes for each turbo? Will this cause any kind of power loss, like on a N/A car? My Idea is to run 2 pipes to a muffler located under the drive shaft, with 2 pipes exiting the muffler into a "twin" exhaust. I got this Idea from the early 70's Z rally car set-up. I like this idea for 4 reasons; 1) The 2 pipes combined have a greater flow capacity 1 large one. 2) The exhaust gasses velocity should be quicker through the smaller pipes. 3) The pipes are more easily tucked under the car 4) I don't need to get a rice muffler to reduce the back pressure. If anyone has ever done this, or know a reason why this won't work please chime in. Quote Link to comment Share on other sites More sharing options...
Mike Rowe Posted February 8, 2006 Share Posted February 8, 2006 my local expert here on RB motors told me to use a single 3.5inch exhaust behind the RB26, use HKS downpipes off the twin turbos. I am upgrading to Garrett ballbearing turbos. He advised me to retain the current turbo manifolds but ream them out bigger to match the Garretts Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted February 8, 2006 Share Posted February 8, 2006 I think a single fatty 3.5" should work to be honest. Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 9, 2006 Author Share Posted February 9, 2006 It seems that a single would be best, but a single 3.5" will be a tight fit. I'm thinking that a 3" Oval might be the way to go. Quote Link to comment Share on other sites More sharing options...
dj paul Posted February 9, 2006 Share Posted February 9, 2006 yes in my experience in exhausts, although harder to fit, a single pipe is usually more efficient. one of the main reasons you go for 2 pipes, is if you just simply cant cram a big enough single down there. one pipe would also be quicker because it will be hotter since it will all be together (hotter=less dense=quicker flow). hopefully my ramblings have made since. paul Quote Link to comment Share on other sites More sharing options...
Ed260Z Posted February 13, 2006 Author Share Posted February 13, 2006 I'm going to go with a 3.5" from the down pipe to the muffler. And I'm going to notch the tranny support so that the pipe will fit up higher. I still want a dual look, so I think I'll mount the muff just behind the tranny. It will have two 2.5" outlets to make the "dual" look. A lot of modern performance cars do this the get the look of a dual. I'm going to fab up my own exhaust, and I wanted to know if a MIG welder is OK for this application? I don't have a shop, and I don't want flammable gas around the house. Thanks for the replies guys. Ed Quote Link to comment Share on other sites More sharing options...
BirdmanZ Posted February 13, 2006 Share Posted February 13, 2006 a mig welder will do fine. if you are making it out of stainless then you want a helium, co2, argon mix. for mild steel you can use 75/25. neither gas is flammable Quote Link to comment Share on other sites More sharing options...
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