Horsepower and parts

Lord Tin Foilhat

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i was just thinking this. what number would you use to determine your horsepower to pick parts to work the best at that horsepower.

example : would i use the mustang dyno numbers or dynojet numbers when deciding on which exhaust to use to be the most effiecient.

mustang dyno - 233hp which would = 2.5" or 2.75" exhaust
dynojet (conviersion 1.12-1.14) - 260,265 which would = 2.75" or a 3"

also factor if if im running a 50-75 wet shot.

would i be losing power with the 2.5 with the shot? or would the gains be so minimum that it wont matter.

another thing that i noticed is my brother has identical mods, but he is running a 3" header/dp to a 2.5" catback when i was running a 2.5 header/dp to a 2.5" catback and we put down almost identical numbers on the mustang dyno (me 233/211, him 233/214)


basicly this question is out there because i have 2 sets of headers, one with 3" header/dp, one with 2.5" header/dp. i did notice with the 2.5 i have more low end and seemed to pull harder, but i didnt get a chance to floor it because it started leaking and now i need to fix it. and im debating on if i should sell the 3" and keep the 2.5 or swap them again.
 

Bob Kazamakis

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I'd imagine it doesn't matter, your exhaust is only as good as its narrowest point I'd imagine, same goes for intake too typically.


to an extent. ive seen tests done on muscle cars where they do a 3" exhaust (duals) to the mufflers and then 2.5" from the mufflers back and lost no hp but quieted it down a ton.

and any intake with bends a larger dia. will make up the flow loss of the bend. for instance my intake is 4" but my TB is only 3.5" (i think) and it will make up the flow interruption of the 35 degree bend its got in it.
 

Lord Tin Foilhat

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what are your plans for the future? any engine work or just bolt ons? if you plan on taking the car forward i would just go with the 3" header then and dont even worry about it.

after the 50-75 wet im done modding it. Unless theres a big revalation (which seems to be coming with the tvs, twinscrew, twincharge, and hahn turbo) , i think im just going to put all my resources to my camaro (more power to be made) and call it a day after this. but i want this to be the most effiecient and to be runing the best i can get it without worrying about blowing everything up
 

Ron Vogel

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The 2.5 is fine for you. You need to concentrate on increasing TQ and HP. With that 4 banger, I see no need at all for a 3" exhaust. Not only will a 2.5 have more velocity, but it will also be lighter. I don't even see a real need for 3" on a GP, unless you are really pushing big HP. My car was dynoed with only a 2.5 with a single muffler.
 

Euro

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If you are like me and rev high to make good power, a bigger exhaust shouldnt hurt. Just keep the revs up. I normally dont go below 4000 rpms if i can help it.

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