Guest Hceline17 Posted October 12, 2003 Share Posted October 12, 2003 Hey folks, haven't posted in a while, mostly because I've been working really hard trying to earn money for my Z (oh yeah, and that college thing I do). At any rate, I've gotten pretty good with the search function, but some questions were raised in my mind when trying to visualize my exhaust system. I'm going with a ram-jet zz-4 350... Here's what I think I'm going to do, tell me if its absurd sounding. I'll need a custom made header for the left side of the block, 4-2-1, and then into a 1 3/4" pipe (on each side) that meet at an X pipe and then I'll vent them off to each side just in front of the rear wheels out of two Turbo mufflers. The logic goes each bank will run out of a 1 3/4" pipe (probably put a resonator in each one) and the X piece will help to cancel out wave resonances... This should sound ok, and be plenty of piping to vent the gases sufficiently, right? Otherwise I'd like to hear the upside of a straight shot 3" pipe to the rear with a muffler as close to the headers as I can get it. I read on another post that a 3" exhaust is excessive on a N/A 350, why is this? A 2.5" straight back would be sufficient, but would a 3" hurt performance? I read a technical article the other day that said anything a person can do to reduce backpressure on an engine is a good thing, but I can't remember if it was in regards to a turbo engine or not and what effect that would have on things. Your info on this matter would be most helpful as I decide on what I'm going to put on my car, thank you Quote Link to comment Share on other sites More sharing options...
Guest kustom240 Posted October 12, 2003 Share Posted October 12, 2003 If you're having headers built, why not use merge (or venturi) collectos? Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted October 12, 2003 Share Posted October 12, 2003 A larger exhaust cannot hurt performance, but it will not improve performance. I would recommend going for the smaller of the two because Z's seem to have a problem with exhaust fumes which seems to be attributed to the velocity of the exhaust as it exits the tailpipe. For figuring out how big of pipe(s) you need, use the figure that straight pipe flows at about 115CFM PSI (cubic feet per minute per cfm). This means that a 2" exhaust will flow at about 400 CFM and a 3" exhaust will flow a little over 550 CFM. Depending on how well your heads flow, a 2.5" falls in the middle there and should be ok. Some people also like to use the 1" per 100 HP figure which isnt as accurate, but is pretty good. If you are making 300HP then you would want a single 3" or dual 1.5" minimum. Quote Link to comment Share on other sites More sharing options...
Guest Mike The Vagrant Posted October 13, 2003 Share Posted October 13, 2003 After resolving some issues with my account this is my new name by the way (HCeline17). Where to start... 1) I would love to see some equations or general rules of thumb on how to come up with CFM numbers Rebel 2) The engine my friends are telling me to get makes about 350hp from the crate. 3) I was trying to figure out at work how big of a difference my systems had in terms of Area of the pipe per cylinder bank. Here's what I came up with: A 3" pipe serving both banks gives me this in terms of area of the pipe, 7.06/2 or 3.53 square inches per bank. Duel 1 3/4" pipes will give me an area of 2.4 square inches per bank. That difference is pretty considerable, the 3" pipe is going to be able to flow a lot more exhaust than the duel system. The difference is even greater for those who think that duel 1.5" pipes will flow as much as a 3" pipe (duel 1.5" pipes have a pipe area per bank of just 1.76"... half that of a 3" exhaust pipe) Anyway, I got bummed for a second thinking that duel side exhausts wouldn't be sufficient (I think they'd be pretty cool is all ). Then one of those DOH! lights lit up in my brain... Increase the size of them. Duel 2 1/4" give me the exact same pipe area as a 3" exhaust would, it also gives me some benefits like a shorter overall exhaust and smaller diameter piping to better control gases and keep velocities higher... anyway, I think I'm going to go with the idea of 1 square inch (as opposed to 1" in diameter) per 100hp and go with duel 2 1/2" ummm... any of this sound logical to anyone? I basically just used pi(rxr) and got these numbers... Quote Link to comment Share on other sites More sharing options...
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