84z31 Posted January 14, 2006 Share Posted January 14, 2006 hey i have a stupid question i have a 84' 300zx. do you think a 3" exhaust is going to kill it? i plan on adding a turbo later. after i gather all the parts. i have some 3" stainless steel tubing i want to use. i have a bender i can use out at work. so it wouldn't cost me much to bend up the tubing. i just need to get a muffler. i don't think backpressure is a big deal unless i was driving a truck. then its good for torque. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted January 14, 2006 Share Posted January 14, 2006 actually the back pressure thing isn't quite true. not sure where it all started but actually backpressure is never really a good thing to have. i believe its more of you want to keep velocity up. Quote Link to comment Share on other sites More sharing options...
84z31 Posted January 15, 2006 Author Share Posted January 15, 2006 i think i am going to hook up my exhaust right before where the cat would be.. then run it under the crossmember for the diff. and up to a muffler. it'll take take a little over 7' of tubing. i have about 14' of stainless steel 3" tubing. so i think i'm set. i just got to get up to the bender and bend the tubing up. and then sneak into the bosses shop to weld it all up. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted January 15, 2006 Share Posted January 15, 2006 actually the back pressure thing isn't quite true. not sure where it all started but actually backpressure is never really a good thing to have. i believe its more of you want to keep velocity up. Yeah, it's pretty much a myth. If you're going turbo, then it definately doesn't matter. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted January 15, 2006 Share Posted January 15, 2006 I agree, but there are some times that back pressure thing is true. I guess it depends on the engine. For example. I have a 93 jeep cherokee 4.0 and recently I had the whole exhaust changed (headers, cat, pipe, muffler) and I noticed that it have more HP but when winter came around and I had to put in into 4x4, I found out that I lost alot of torque on the lower end and now I'm using more gas than I would usually be using. Same thing with my moped. Not saying that its true or false, but just what I've noticed. you shouldn't be concerned about it. Quote Link to comment Share on other sites More sharing options...
RedBeauty84ZX Posted January 15, 2006 Share Posted January 15, 2006 actually the back pressure thing isn't quite true. not sure where it all started but actually backpressure is never really a good thing to have. i believe its more of you want to keep velocity up. True to an extent, yes. Your never actually "losing" any power, but your shifting it to a different place in the powerband. My car lost quite a bit of low end grunt when I removed my cat and added 2.5 piping, it did gain some high end power however but I dont think it was worth the trade. Quote Link to comment Share on other sites More sharing options...
84z31 Posted January 15, 2006 Author Share Posted January 15, 2006 i had a toyota truck and replaced the exhaust with a 2.5" exhaust. i lost all my low end torque. i went down to a 2.25" pipe and muffler and it was much better. i think since i'm keeping the stock headers and piping up to the cat i shouldn't lose too much power. besides the fact that i don't want to redo the exhaust twice. all i'll have to do is rip off everything up to where i'll put the turbo. Quote Link to comment Share on other sites More sharing options...
ngrimm Posted January 26, 2006 Share Posted January 26, 2006 Seems to me there would be a need to tune the a/f when increasing exhaust size to compensate for additional flow thru the engine. Perhaps some of the torque could be recovered that way? Quote Link to comment Share on other sites More sharing options...
84z31 Posted January 27, 2006 Author Share Posted January 27, 2006 bigger injectors and a turbo:-D Quote Link to comment Share on other sites More sharing options...
AK-Z Posted January 27, 2006 Share Posted January 27, 2006 i had a toyota truck and replaced the exhaust with a 2.5" exhaust. i lost all my low end torque. i went down to a 2.25" pipe and muffler and it was much better. i think since i'm keeping the stock headers and piping up to the cat i shouldn't lose too much power. besides the fact that i don't want to redo the exhaust twice. all i'll have to do is rip off everything up to where i'll put the turbo. same here. This seems to be the case for suv/trucks, might not for cars. my jeep wants to shift at 45mph instead of 40mph which is killing my gas milage inless i drive it hard (how ironic). Quote Link to comment Share on other sites More sharing options...
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