Guest Anonymous Posted May 31, 2003 Share Posted May 31, 2003 i am going to be getting my exhaust system done very soon and i wanted to know what pipe diameter would be better. i have a l26 engine with the 71 SU's in my 71 240Z. it has headers on it and i plan to get the exhaust system done from the headers back. i've heard from many people to go 2.5" but the collector at my headers doesn't even seem that big. it seems 2.25" and the mechanic that is going to do the exhaust system for me says that it's not that good to go 2.5" as i will lose the low end torque. i already know that but don't you gain more in HP with 2.5" over 2.25"? the mechanic also told me it's not good to go bigger than the collector pipe. any suggestions? Quote Link to comment Share on other sites More sharing options...
Mike C Posted June 1, 2003 Share Posted June 1, 2003 I've always run 2 1/2" on my NA L series motors. I have not noticed a reduction in low speed torque, but the opposite. And the 2 1/2" will keep up with most any mods you do for the NA motor. I personally like the Walker Dynomax mufflers. I have a 2 1/2" center in/offset out and it tucks up amazingly well. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted June 1, 2003 Share Posted June 1, 2003 I have 2.5 inch pipe on my 240 engine with MSA headers (the CARB legal ones). I would go with 2.5 inch pipe, but admittedly it probably won't make much difference in performance either way. I think any low end torque enhancement has already been realized once you get out of the headers. The plumbing from the collectors back can only add back pressure, so the larger the better. Ground clearance with the larger pipe is adequate, and the weight difference is negligible. I should say my only real complaint with the exhaust set up is the air pump causes backfires out the tailpipe when decellerating. It caused some issues with the safety inspection here in Maryland. I often wonder if a more restictive exhaust (like the stock set up) would make the difference. Quote Link to comment Share on other sites More sharing options...
fl327 Posted June 1, 2003 Share Posted June 1, 2003 go big. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 1, 2003 Share Posted June 1, 2003 thanks for the replies so far.... so has anyone here gone 2.5" piping with the collector pipe on the header being only 2.25"? Quote Link to comment Share on other sites More sharing options...
Mike C Posted June 2, 2003 Share Posted June 2, 2003 I run the stock 240 manifold and "downpipes" into the fishmouthed 2.5" piping. Everything I have read shows minimal gain on an NA motor with the header, at least not enough for me to endure increased underhood temps and noise. I'm working on an L28 swap with triple Del'Lortos and will keep the same setup. Quote Link to comment Share on other sites More sharing options...
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