exhaust

Hey,

I got my downpipe replaced because I guess it had a whole in it, made a horrible sound.


So I got it replaced, and now I feel the exhaust leaking through a seal I think, it sounds normal and then out of no where it makes a loud sound and goes back normal...

Lets say its leaking through the part of the down pipe that connects to the header, or the actual exhaust pipe,

will this make me lose HP?

I have a warranty on the install I guess i gotta take it back.

:grinyes:
take it back.

You wont loose hp the whole back pressure this is bs. Might wsant it fixed so it sounds better though.

You wont loose hp the whole back pressure this is bs. Might wsant it fixed so it sounds better though.



sounds a hell of a lot better even with the leak sound that pops in and out, the leak sound makes it sound kinda cool...


But I dont want to loose hp or anytthinig... What else could a leaky pipe cause (what other probs)?

You wont loose hp the whole back pressure this is bs.

Uh...:uhoh:

You wont loose hp the whole back pressure this is bs. Might wsant it fixed so it sounds better though.

Backpressure is not BS, in fact it's not even the correct terminology. People used backpressure so damn loosely and not even know what they're talking about, they just think that backpressure has something to do with the exhaust.

The correct terminology for backpressure is exhaust velocity, and enough of a loss of exhaust velocity CAN cause you to lose hp. Exhaust velocity=good, loss of exhaust velocity=bad. That's why when people try to put 3" exhausts on their n/t models, they'll actually see a decrease in performance, because the engine can't flow enough air to get enough exhaust velocity running through those massive pipes. Now on the other hand, too much exhaust velocity can cause a "backwards pressure" into the cylinder and causing it to run poorly.

With the amount of leakage that you're talking about, it would be very minimal and you probably won't see any hp loss, but I would get it fixed before it creates anything more of a problem

Theres a really good write up on tuners about back pressure.

You'd be able to feel it if it lost power when it started leaking....

I think ez asumed that he had a turbo car, but we all know he is an idiot so I'll let it slide =P

thanks for the input guys, I am going to take it back real soon!

Yup you do need backpressure on a NT but us turbo guys can just run open exhaust, thats the best thing for us ;)

Hey Thompson The way you explained exhaust velocity I get a picture of a parabala (with horsepower on the Y and velocity on the X) in my mind with too much velocity on one side an apex in the middle and too little velocity on the other. Im pretty sure I understand what your saying I was just wondering if there is an ideal velocity, or possibly some equation which takes into account exhaust diameter.
I don't know how I could measure this velocity I just like knowing these kinda things (kinda like an ideal AF ratio>too rich (too high velocity), too lean(too low velocity), stoich(ideal velocity).

I'm sure there's some sort of formula that you could figure out but you would have to take in account the speed that the gases exit each and every cylinder and the inside diamater of the piping and the length and all those other variables. You could try google it or maybe some day when I'm extremely bored I'll see if I can come up with an "Ideal Velocity" formula. :)

The consensus is that with a N/A Eclipse/Talon, 2.25" is the best exhaust diameter for best flow and velocity if you have a few other basic mods (intake, header), and I think stock is somewhere around 1.75" IIRC. Turbo cars can go anywhere from 2.5"-4.0", and I don't know the stock size off hand but I think I saw 2.25" mentioned.

Stock exhaust is 2.25"

Unless you have intake, ported head, and a header you might as well just retain the 2.25" stock exhaust. When you have those upgrades, 2.5" would be the best size to go with. Alot of times you'll see the "axle-back" mod done to people that don't want to upgrade with an aftermarket system because the stock turbo muffler flows quite a bit more than the NT muffler.

Stock exhaust is 2.25"

Unless you have intake, ported head, and a header you might as well just retain the 2.25" stock exhaust. When you have those upgrades, 2.5" would be the best size to go with. Alot of times you'll see the "axle-back" mod done to people that don't want to upgrade with an aftermarket system because the stock turbo muffler flows quite a bit more than the NT muffler.

Since we are on the subject of exhaust diameter and what not. I will be running either a 14b or S16g no more than 10psi for now on my stock internals. I was thinking of going full 2.5" cat back, 2.5" down pipe, and 2.5" catco cat. Would this exhaust setup be adequate or what do you reccomend? Should I go 3"?
thanks.

If you're putting 10psi through a 14b or small 16g, a full 2.5" will be fine. Now if you eventually upgrade the motor and crank up the boost to ~20psi, then I would go with 3". But then again, if you're never going to be n/a agian on that car, then I would just mod once and go with a 3", but not until you get the turbo installed, otherwise you'll lose an assload of exhaust velocity.

Thanks, I think I'll stick with my original plan for 2.5".

Yeah, a 2.5" will be fine if you just plan on running 10psi on the turbos that you listed.