Reads Sir Rev Alot’s Thesis
… so what are you really trying to say? :think:
j/k 
quote:
Originally posted by Integra Style
SO it turns out that Hondas don’t need backpressure, they need as high a flow velocity as possible with as little backpressure as possible.
quote:
Originally posted by Formz TSi
um… thats what EVERY car needs. Not just hondas. But its impossible to have peak velocity with zero backpressure. It’s a tade off:
Best velocity with huge backpressure
Huge backpressure but zero velocity
You have to find that point. And an exhaust cut out is NOT the answer. Most people feel its 2.25" piping.
OK, i talked to my auto mechanics teacher about this today, he made me thouroghly confused. You are right Formz TSi about cars needing some backpressure (says my teacher) and i was wrong :shy: . He has a book with some equations for backpressure and velocity which i will ask him to bring in.
And thats what i was saying: “You have to find that point.” And yes, it is impossible (even theoretically) to have 0 backpressure because of the stagnant air that is sitting at then end of the tailpipe and because of the friction in the tailpipe.
I still don’t understand why an exhaust cutout will not be good, i know that my dads race car has a striaght pipe that ends about 6 feet from the exhaust manifold. oh well
90 Teg LS w/ stock piping 
:shy:
how does a testpipe and aftermarket muffler relate to low end loss if the pipe diameters are not really changed, but paths just unblocked?
it falls on the same principal of pipe diamteres. You’re making the exhaust less restrictive.
With a striaght pipe exhuast setup, would you lose low end also? and if so, why?
well, just replacing the cat with a straight pipe on a stock exhaust system wont gain you anything but a swift kick in the butt by local law enforement. But lets say you had an upgraded header, cat back, and then put the straight pipe on. Yes you would lose some low end power. I’m not sure EXACTLY the reason, however I’m convinced it has something to do with NA low displacement motors needed more backpressure to produce torque then FI or higher displacement motors.
To clear some of that up if you’re confused:
1.8L NA motor needs more backpressure to produce torque then a 1.8L turbo or 5L V8. But then again, if you’re running a turbo, the turbo itself produces ass loads of backpressure anyways, thats why no exhaust is the best exhaust for turbo cars.
I thought about the same Idea and might still go along with it. But I would only open the valve on the track. For street use it would be extremly loud and annoying, but the track who cares, and you are always trying to get every last hp number out of our engines. I say go for it! But just don’t be stupid and open the valve while your on the street driving down a residential area or just on the street period. Use it for TRACK ONLY!
rcn acura: that is what i was thinking about doing, but i have been convinced otherwise. So how does backpressure benifit a low displacement motor?
there is a point where backpressure is too much, and when it is too little. most people consider a header, high flow cat, and 2.25" piping perfect for an integra.
Well I use to have a flowmaster muffler on my exhaust setup I have and then took the car into midas where they installed a regular muffler and MAN WHAT A DIFFERENCE! The backpressure helps out alot with the low end torque significantly. I like the midas muffler alot more than the flowmaster anyday! But I still think that for track applications backpressure is of no concern because you are trying to get to redline the quickest! But I was also thinking about putting one of the Nissan mufflers on the car because they have a valve within the muffler that opens and closes depending on airflow and which helps out backpressure and low end torque.
Originally posted by rcnacura
Well I use to have a flowmaster muffler on my exhaust setup I have and then took the car into midas where they installed a regular muffler and MAN WHAT A DIFFERENCE! The backpressure helps out alot with the low end torque significantly. I like the midas muffler alot more than the flowmaster anyday! But I still think that for track applications backpressure is of no concern because you are trying to get to redline the quickest! But I was also thinking about putting one of the Nissan mufflers on the car because they have a valve within the muffler that opens and closes depending on airflow and which helps out backpressure and low end torque.
ya but do you not miss the high end? dont use it as much?
Well depends on what your doing. The track, no backpressure is not that important since you are not really using low end, but for everyday street usage, backpressure is what you need no doubt! Without it it would be like having a vtec engine with the vtec broken! And that would suck
edit
what are all the components of an “cat-back exhaust system?” besides the muffler of course.
starting from the end of the catalytic converter: pipe, possibly a resonator, more pipe, muffler, tip. not much to it. “cat-back”. if anything, all the piping should be mandrel bent, not crushed with wrinkles.
My exhaust setup… B18A1
Street:
DC 4-1 header.
test pipe.
stock muffler.
Weekend nights:
DC 4-1 header.
test pipe.
Track:
DC 4-1 header.
when I race on the street I take the muffler off. When i race at the track If i’m not lazy I just run open header. These are not streetable. Its not cool going deaf at 25mph, and needing to downshift on the freeway just to go up over small hills or bridges.