pipe size

[ontarian_frog]

You will lose some of your torque if you got w/ a 2" all the way back but gain a little hp.
Any bigger than that and there wont be enough back pressure.

Umm... Horsepower is a measure of torque * rpm / 5252. SO if you gain hp, you automatically gain torque.

[sappy96]

Uhm, not necessarily.

Horsepower = Torque * RPM/ 5252

So you can have less tq at your current peak RPM but at a higher rpm it would be the same or slightly less. Sooo you can have less tq and more hp.
Look at honda engines, no tq but all kinds of hp and the same displacement motor from someone else could have more tq but less hp.
Its all about where you make your power.


So
Car Z
has 100 lb ft of tq at 6000 rpm =60000/5252=114.242 hp
Car Y
has 95 lb ft of tq at 9000 rpm = 855000/5252=162.795hp

See, less tq, more hp.

[ontarian_frog]

If you take the same engine and make more horsepower with modifications, you have more torque somewhere you previously didn't.

[sappy96]

If you take the same engine and make more horsepower with modifications, you have more torque somewhere you previously didn't.

Sure, but not a higher peak torque value necessarily. If it drops your old peak torque down 5 foot lbs then increases 3 foot lbs high in the rpms you have more torque somewhere, just not where you want it or need it.


Not to mention that you will probably end up hurting hp and tq if you go too big of a diameter.

There is no reason for a 2.5" pipe for an aveo unless you are using boost.

[exodus]

hit the nail on the head... you can have 500 peak hp... but if it's for 200 rpms... it doesn't do you much good.

No matter what racing you're doing, you always looking to accelerate faster. A long linear high ft-lb torque band is what you should aiming for.

Take drag racing into account... the majority of your time is lost during shifts.

If you have a car with a short range where you produce a high amount of HP, you have to shift more often to keep it within that range (talking professionally here, you'll swap out the gears to compliment your engine, or at least the final drive in semi-pro).

Then lets say you have a car that produces less peak HP(gotta keep it in the ballpark of the other car), but delivers the power in a more linear way, and for a longer duration. That car can use a longer gearing, which means fewer shifts, and a higher (mechanical) top speed.

The latter car will have a faster 0-60 and 0-100... while the first may have a faster 60-100. Though, overall the second car should win.

Of course there's a lot of if-ands-or-buts in this scenario, though for all intensive purposes the linear, long, and consistent torque curve is what you should be looking for.

In drag racing you can deal with a power spike, although think about track/rally... you don't want to jump up 20 hp out of nowhere mid corner. You can end up sideways (more than you want) and meet an immovable object. If you can't finish the race/stage, it doesn't matter how much power you have.

[ontarian_frog]

Back to piping. I agree with anyone saying there is a size limit, never said there wasn't. I just don't like it when people say things without back up. How the hell does anyone here have an opinion on which size to go for? Who can truly say you'll loose torque or horsepower if you go with this or that?

Ahh yes... the butt dyno. The best way, without a dyno run to know for sure if your car runs higher numbers than before, is with a quarter mile finish speed average of before and after.

http://autospeed.com/A_108704/cms/article.html

[xtreme 2]

there's nothing wrong with the butt dyno... but access to a dyno is much more accurate...

[sappy96]

Lets see, my GTO has dual 2.5 exhaust for a 400hp+hp car.
The aveo is about 1/4 of that w/ even less than 1/4 displacement. Sooo 2.5 is way to big.

This is actual math equations I am sure to figure out the optimum size of exhaust tubing.

[y2dgone]

Lets see, my GTO has dual 2.5 exhaust for a 400hp+hp car.
The aveo is about 1/4 of that w/ even less than 1/4 displacement. Sooo 2.5 is way to big.

This is actual math equations I am sure to figure out the optimum size of exhaust tubing.

Unfortunently it has more to do with displacement then with horsepower

[AVE0SAM]

go with 2" exhaust...no one on here has an aveo with enough modifications to warrant anything bigger...i believe brian was the only one who ever went for a 2.25 exhaust to 2" and felt a better pull for the two inch