Exhaust 2.25" VS. 2"

[projectmx]

Well after doing research i feel more confused than when i started... i'm hoping to change my exhaust pretty soon... when i got the car it had a custom exhaust which y'd in the back to make duals.. there are two or three inline resonators or mufflers on it and i have very little high end power because of it... i plan on pulling everything from the cat back and redoing it.. but i don't know if i should go with 2 or 2.25 for the piping... there seems to be a lot of debate on it... i need some real feedback.. please help

[Limegreen mx-3]

Originally posted by mazda78:
Well after doing research i feel more confused than when i started... i'm hoping to change my exhaust pretty soon... when i got the car it had a custom exhaust which y'd in the back to make duals.. there are two or three inline resonators or mufflers on it and i have very little high end power because of it... i plan on pulling everything from the cat back and redoing it.. but i don't know if i should go with 2 or 2.25 for the piping... there seems to be a lot of debate on it... i need some real feedback.. please help

i started with 2in piping with a cat and pro 1 exhaust loved the sound and feel at high end. later on i had the cat removed because i didn't like the way it felt. A year ago i up the piping to 2.25in with no cat and all the wayback to my OBX exhaust. sounds a lot deeper and help out in the top end but hazy in the low end.

(There has been much debate on size of piping form 1in 3/4 piping to 2in with is good for a 1.6 engine. 2.25 in pushing and that the 1.6 needs backpressure. these are some of the things i have read.)

In my opinion i like my setup no cat 2.25in piping with a OBX exhaust. Other may disagree with my setup loosing power,no enought backpressure pipe is to large for the 1.6.

laters

Drifter MX-3

[schwankesmx3]

ive got 2.5in tubing and i have no low end power but it makes up for it at about 5 grand then when the vics hits at 5500 the motor explodes withpower soo im saying i got highend power with 2.5 but its all personal preference

[mykel78]

I've done alot of research, and had discussions with several professionals and have come to this conclusion: It's not backpressure that matters to these engines, it's the matter of airflow inside the pipe. If the pipe is wider, air velocity changes, a pipe that's too wide has air moving too slow - resulting in loss of power at some points in the powerband. While a tighter pipe keeps the air moving. Backpressure is a misconception, and if I can find it, I'll pass on an excellent article I read not very long ago. My 94 RS, has an open system, muffler only, with factory piping - 0 'backpressure', and operates just fine. I'd like wider pipes, but I don't want to slow the flow too much and lose power. I just wanna dispell the myth of backpressure - it's a matter of air velocity, and finding your personal balance of diameter and performance. In fact, enough backpressure will slow your engine, that's why removing a cat can help your engine a little, and a clogging cat can blow the head.

[projectmx]

well right now i've got decent low end power but my high end power sucks... i can barely do over 100 which seems wrong because my protege with the 1.5 could easily hit a little over 110...
i was running quaters against my friend with a mitsu mirage hatchback and i kept up with him until we hit around 80 and he finally pulled away... he seems to think its cause of my exhaust... the person i bought the car from made duals and right now it has the cat / the resonator / and an inline muffler....

[mykel78]

what diameter is your custom exhaust? where does it split for the dual tip? Since it is custom, do you know if your cats have been gutted? Both of mine are still on, both have been gutted, since it's 'illegal' to cut them off.

[mitmaks]

I think youve got too big of exhaust guys, 2-2.5 for little 4 bangers thats too much,

[projectmx]

i think it looks like the stock piping.. just 1.75 and the y comes off at a 90 degree angle just behind the spot where the sparegoes and it moves around it so the duals come out on either side of the spare.

<small>[ September 26, 2004, 04:43 PM: Message edited by: mazda78 ]</small>

[mykel78]

mitmaks, agreed, I think stock diameter is fine on the 4-cyl, maybe 2, that's as far as I'd go. Mazda78, that split may be what's killing your high end, if you don't have an exhaust leak. I'm presuming the split is after the muffler? If so, may be iffy on the cause of loss. Dang it though, you should be able to beat a Mirage!

[projectmx]

what is the point of a high flo cat? i've been looking at them on ebay pretty much all of them say off road use only which means not street legal... seems like it you are going to do that why waste the money.. just cut the cat out and make the pipes go from the header to the muffler

[monty73741]

a i hope not speeding like that on city streets.
b i saw your car domain page......it looks like u are probally suckin in engine heat....that is a problem

[projectmx]

my high end problem was the same as when i bought the car

[mxprecidia]

r stock pipes 1.75" all the way?

[BuGS]

If you are wanting more top end get a junkyard turbo and build your own setup. Or better Yet get some Miata Cams. Josh is the master in my mind of what you can do. PM him. He has the knowledge first hand. Everyone else is all second hand.

[mxprecidia]

how big are the stock pipes?