HowlerMonkey Posted June 3, 2009 Share Posted June 3, 2009 Yep......no need to go much bigger than the turbo outlet size as long as your turns are not pinched badly. On my turbocharged maxima (L24e), I was able to only have to go 45 degrees rather than 90 on my downpipe. Quote Link to comment Share on other sites More sharing options...
softopz Posted June 4, 2009 Share Posted June 4, 2009 thats why i said atleast 5hp Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 4, 2009 Share Posted June 4, 2009 To determine where the horsepower came from we would need the motor insanity calculation sheet. NICE TIE IN! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 4, 2009 Share Posted June 4, 2009 No way a stock 280zxt downpipe is 3 inch because the outlet of the turbo is 2.5 ...its 2.5 cast iron with 2 90 degree bends. I think you can pick up another 5hp atleast with a new custom 3" dp. impressive gains though now turn up the booooost baby It is indeed 3". It expands out at the collector a bit. I can take a pic of the downpipe held up next to my 3" exhaust. Seems bassackwards - but it is what it is! Quote Link to comment Share on other sites More sharing options...
Challenger Posted June 4, 2009 Share Posted June 4, 2009 Doesnt it expand to 3 inches? Seems like the opening is ~2 and the exit is about 3 inches. Quote Link to comment Share on other sites More sharing options...
jeffp Posted June 4, 2009 Share Posted June 4, 2009 The cast part of the DP is not 3" the outlet of the turrbo and inlet to the DP is about 2 1/4" I tried to use the stock DP when I went to a stage 5 exhaust side, 2.448" outlet. I could have opened the cast part of the DP, but it would have been thin in places. Now from the flange at the DP and pipe connection is 3" the pipe is 3" and the stock flange for the cat was 2.600" or a little bigger. But by that same token, if you are running a stock stage 3 exhaust turbine, then the 2.5" pipe is fine, you will still get good flow, but the trouble will begin for you if you try to push 400-450hp + with that setup. That is why I went to 3" in the first place. Also after testing the car and system, once I got past 600hp, well 650hp, it appeared that I was not making any more power if I turned up the boost higher then 22psi. I am running a gt35R unit and I am running the .63 A/R exhaust turbine housing. I can get more power I believe with the .82 A/R turbine housing. but I have not tested the system @ 650hp, only 500 hp, and at that point I had not reached crossover on the inlet to the turbo. anyway, Yasin, go with the stage 5 exhaust turbine housing 2.448" minor on the wheel, port match the flange, and neck up to 3" pipe as soon as you can and you should be just fine to 500hp. Quote Link to comment Share on other sites More sharing options...
jonvr4g63 Posted June 5, 2009 Share Posted June 5, 2009 Thanks Yasin!! I really really like how that exhaust came out... although it was a bear making fit! Going through the rear sub assembly is something that I don't have to practice since most of my exhausts are on either DSMs or Evos. I think this particular system is probably my favorite sounding of all the systems I have built. That Burns muffler really set it off. I am going to see about getting it reproduced in 3.5in 304L stainless steel. I know there has been some debate as to why I kept the cast downpipe. The main reason why I kept it was due to the fact that it goes 2.5in to 3in with a GRADUAL gain in size. This keeps the hot gasses from tumbeling and causing turbulance. By keeping these gases happy, you will gain spool up, and have a nice and tight dyno graph. I ported this cast iron downpipe and really took time to clean up the casting flash. I think it flows very well now, and def will support some good power. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted June 5, 2009 Author Share Posted June 5, 2009 Thanks Yasin!! I really really like how that exhaust came out... although it was a bear making fit! Going through the rear sub assembly is something that I don't have to practice since most of my exhausts are on either DSMs or Evos. I think this particular system is probably my favorite sounding of all the systems I have built. That Burns muffler really set it off. I am going to see about getting it reproduced in 3.5in 304L stainless steel. I know there has been some debate as to why I kept the cast downpipe. The main reason why I kept it was due to the fact that it goes 2.5in to 3in with a GRADUAL gain in size. This keeps the hot gasses from tumbeling and causing turbulance. By keeping these gases happy, you will gain spool up, and have a nice and tight dyno graph. I ported this cast iron downpipe and really took time to clean up the casting flash. I think it flows very well now, and def will support some good power. Jon - Thanks for coming on board and chiming in - you do great work! I do have a stock cast DP sitting around at home, I will photograph this weekend and put some pics on this thread, to show the 3" at the bottom flange. I am very very happy with the exhaust (the car sounds tough), the sound and of course the significant power increases, throttle response and driveability from 1K to redline is much imprroved. The comedy is that when I pulled up to the dyno everyone thought that I had put a LS1 in the car, it was funny. I shall do a YouTube Vid to give everyone an idea. I still have to put a tip on the car so that is next. Good thread. Yasin Quote Link to comment Share on other sites More sharing options...
slownrusty Posted June 8, 2009 Author Share Posted June 8, 2009 I stand corrected the stock down pipe is in fact 2.5in as previously mentioned by Drax and a few others. I have to discuss with Jon in regards to fabbing up a full 3" unit. Yasin Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 8, 2009 Share Posted June 8, 2009 I wasn't going to push the point because my memory was a bit fuzzy on the subject, but I seem to remember sticking a 2.5" piece of tube in there and having it fit like a glove. Thanks for the update Yasin! Quote Link to comment Share on other sites More sharing options...
jonvr4g63 Posted June 9, 2009 Share Posted June 9, 2009 Yasin, this is the area in which most of my porting took place. By removing that fire ring step, the dp is opened up to 3in. Your fist bend on the dp fit into the space and the tubing used was 3in out side diameter. Quote Link to comment Share on other sites More sharing options...
soullessjdog Posted June 12, 2009 Share Posted June 12, 2009 I used msa down pipe with 2.5 inch pipe all the way to the rear with no muffler and i went from 7psi to 9psi and car mad 195hp to the rear wheels but this motor has perfect compression and only has 40,000 miles on the motor i to think i found it in a junk yard. Quote Link to comment Share on other sites More sharing options...
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