4" Exhaust!?
I know they are but they're dumping it out the front bumper. AND they're making 1000whp they have enough exhaust gas to need a 4" pipe.
Last edited by BURNALL_4; Jun 13, 2007 at 11:32 AM.
and?
a 4" exhaust would give you more volume, hence a more free flowing exhaust. now u may or may not see the gains over a 3" because of the displacement of the motor. a 2L is really small. tipping the scales at a whoping 120ci isnt ****.
a 4" exhaust would give you more volume, hence a more free flowing exhaust. now u may or may not see the gains over a 3" because of the displacement of the motor. a 2L is really small. tipping the scales at a whoping 120ci isnt ****.
ok well under certain circumstances, yes, but they are still not running an exhaust. and thats what we are discussing. and isnt the point not to fill the pipe up? i mean if ur filling your exhaust up, then u are getting back pressure. and thats no good when it come to turbo cars
maybe 2.5" can support 600whp but if you have 2.5" TBE and then switched to a 3" or 3.5" tbe i guarantee you'd see an increase of 50whp over 600whp. (all other things considered)
i really think that, we've made valid points.....I really think it wont be benificial to run such a big exhaust. in fact i dont think you would see hardly any gains over a 3" maybe 5whp
well im not sure. because there are the electronic dump valves, and they make good power. as for fitment, cost and weight issues, nope prob not worth it. espically if he were to only do a 4" cat-back
No exhaust is best for turbo car period. If you must run one then as big as you can get under the car is best. Typically wtq is what ismost affected. A real world example of this would be upgrading my dual 2.25" aftermarket cat-back on my M3. I had turboed the car and was running what was supposed to be the highest hp catback for the car. I had a 3" downpipe from the turbo connect to this system then while at the dyno I unbolted it and gained 35whp and 40+wtq. I built a 3.5" cat-back to bolt to the exhisting 3"down pipe to try to recoup the loses with an exhaust on the car. I made almost the same power as no exhaust, but only gained 10 of the 40wtq back.
I'd like to see that thread. If there is no power to be made then why upgrade the exhaust at all? Stock is only .5" smaller than his/most yet upgrading yields large gains. It's not like "3's the magic number" No exhaust is best for turbo car period. If you must run one then as big as you can get under the car is best. Typically wtq is what ismost affected. A real world example of this would be upgrading my dual 2.25" aftermarket cat-back on my M3. I had turboed the car and was running what was supposed to be the highest hp catback for the car. I had a 3" downpipe from the turbo connect to this system then while at the dyno I unbolted it and gained 35whp and 40+wtq. I built a 3.5" cat-back to bolt to the exhisting 3"down pipe to try to recoup the loses with an exhaust on the car. I made almost the same power as no exhaust, but only gained 10 of the 40wtq back.
No exhaust is best for turbo car period. If you must run one then as big as you can get under the car is best. Typically wtq is what ismost affected. A real world example of this would be upgrading my dual 2.25" aftermarket cat-back on my M3. I had turboed the car and was running what was supposed to be the highest hp catback for the car. I had a 3" downpipe from the turbo connect to this system then while at the dyno I unbolted it and gained 35whp and 40+wtq. I built a 3.5" cat-back to bolt to the exhisting 3"down pipe to try to recoup the loses with an exhaust on the car. I made almost the same power as no exhaust, but only gained 10 of the 40wtq back.
Well, if you really wanted to, you can calculate the back pressure/pressure drop based on mass flow rate of exhaust and the temp of the exhaust. Knowing temp, you can calculate the density. Knowing density and mass flow rate you can calculate flow velocity and then calculate the back pressure. You'll have to make 'ball park' assumptions, but it'll give you an idea.
Say.... 40lbs/hr of air should be about 350-400hp worth, guess a temp of 1200F, and 5 feet of exhaust tubing. Throw in a couple bends if you want for those additional losses. That should be a pretty good starting point. If you want to approximate higher HP cars, just up the mass flow rate.
I guess I could do a CFD analysis on it if I had some spare time (which I don't for a few weeks).
Say.... 40lbs/hr of air should be about 350-400hp worth, guess a temp of 1200F, and 5 feet of exhaust tubing. Throw in a couple bends if you want for those additional losses. That should be a pretty good starting point. If you want to approximate higher HP cars, just up the mass flow rate.
I guess I could do a CFD analysis on it if I had some spare time (which I don't for a few weeks).