32 replies to this topic

[zAd -]

backpressure lol i guess people still wont get it but its all good. why do the drag racer run open header what their reason wont they lose power from backpressure the deal is not to have backpressure. no one wants reversion that loses power they make header so that the piping diamater increases and making anti-reversion chamber so that the exhaust gases dont go back up in the motor. its all about velocity and with a 4" exhaust your velocity would be killed on such a small motor.

[rpr]

Perhaps there is a misunderstanding of the word 'exhaust' here. The exhaust system consists of the exhaust manifold (or header), a collector, downpipe, catalytic convertor, perhaps a resonator, and a muffler (and maybe a tip on the end). The diameter is the ID of the tubing on all of these items. You could have a 1" exhaust system with a 4" tip, to say that is a 4" exhaust is plain wrong. Likewise you could have a 1" exhaust system with a 4" diameter muffler. Again, not a 4" exhaust system. I think tyrone means he has a 4" diameter muffler, which has very little bearing on the performance of the system, as a whole.

[tyrone]

thanks that is what i meant i have a 5inch muffler i think the system is 2.5".

[Ghost-One]

that being the case and your hissing problem... chesk for leaks cracks and broken welds happens to even quality exhuast systems

[squareback]

thanks that is what i meant i have a 5inch muffler i think the system is 2.5".

If that's the case, you shouldn't be losing power around 3000 rpm; rather, you should be gaining power about then. I had a 2.5" exhaust on my CRX Si for about a year and felt like I wasn't getting the low-end torque out of turns that I should. About 2 months ago I changed to a 2" system, and the low-end came back.

Just to add on to the "velocity vs. backpressure" debate here . . . In an exhaust system, you want ZERO backpressure. None. Zilch. What you want is to keep the diameter of the tubing the correct size to accelerate the gases out of the system. The airflow capabilities of our engines are such that the tubing needs to be relatively small. Once you have increased the engine's breathing abilities, a larger exhaust pipe is a good investment, since the engine can push out more exhaust. My race car, for example, uses a stock EW4 block but has massive headwork, intake upgrades, and internals. It uses a 2.5" straight pipe that dumps before the rear axle. When we first built the car, we used the only exhaust we had lying around, which was a 1.75" system from another Civic. On the dyno, we lost huge power and torque with the first system. We knew we would, but we were fabricating the permanent exhaust system at the same location, so we ran it just for grins.

Since someone will no doubt ask, the car lost 11 horsepower and 9 lb-ft of torque at the wheels. Remember this is a full race engine, so don't go thinking you can see the same gains on a street car. The torque increase was over the whole rpm range, but the horsepower increase came mostly above 4000 rpm.

Mike

[tyrone]

it starts hissing round about 2500 then stops when you get to 3000 rpm. i mite just change the complete system (header, muffler and exhaust piping) hopefully this will solve the problem, its really starting to sound gay and it seems to do it more when the whether is hot rather than when its cold

[Ruevil]

Hey what do you guys think of ANSA racing mufflers? I came across one that is a 2" inlet and would fit under the car.

The§ilent|3lade
"Veni, Vidi, Vici."

[RexKrazy]

http://members.cox.net/rexkrazy

yes, i put this link in every muffler related topic.

sounds like stock, flows like a straight pipe.

[84crx06]

dont think that is true. i went from 1 inch piping to 2.25 piping and my car is alot faster now. where did you hear that?

<{POST_SNAPBACK}>

one of the guys in my college has a 86-87 Si crx and he said cuz I have the D15A2 that the stock pipe size is like 1 1/4 and a good upgrade would be btween 1 1/2 and 1 3/4. he also said if I went any bigger like a 2 inch piping, I would most likely fuck up a valve or two. 1 1/2 piping sounds really small, but his car is hooked up and 1 1/2 piping is a good balance point. Is this true? whats a good piping size? I have a custom intake setup and I just want some more power without screwing with the back pressure and all that good stuff. make sense??
please help.
thanx

[stevo911_]

you dont want to screw up the velocity, not the backpressure. I'd got a bit bigger personally ~2 inchish. I've got 2 1/4 on mine, mostly because i got the whole system for 80 bucks, no complaints here

[rollz87civic]

plz get rid of the fart can

[cbstdscott]

The Ferrari Enzo has small vanes on the exhaust tips that close down at low rpms and open up at high rpms.

As many people have pointed out, the entire exhasut sytem can be tuned like a violin. Racers have it easy, their engines are tuned for a relatively narrow band of power at higher rpms an dso they can tune their exhaust to maximize high rpm flow. A street engine has to provide low end grunt as well as high rpm power.

Something to consider that gets forgotten is the WEIGHT of your exhasut system. While big shiny tips/mufflers look cool, you pay a penalty in dragging that stuff around. I have found that a glasspack mounted right behind the catalytic converter and a simple side exhaust is light and effecient.

Scott

[1stGenRex]

The Ferrari Enzo has small vanes on the exhaust tips that close down at low rpms and open up at high rpms.

As many people have pointed out, the entire exhasut sytem can be tuned like a violin. Racers have it easy, their engines are tuned for a relatively narrow band of power at higher rpms an dso they can tune their exhaust to maximize high rpm flow. A street engine has to provide low end grunt as well as high rpm power.

Something to consider that gets forgotten is the WEIGHT of your exhasut system. While big shiny tips/mufflers look cool, you pay a penalty in dragging that stuff around. I have found that a glasspack mounted right behind the catalytic converter and a simple side exhaust is light and effecient.

Scott

<{POST_SNAPBACK}>

Scott is a wise old man...and i have taken his advise on the exhaust he speaks of...so far, Im really happy with it!

[ibcnya]

Scott is a wise old man...and i have taken his advise on the exhaust he speaks of...so far, Im really happy with it!

<{POST_SNAPBACK}>

how loud are the packs??? does it sound almost like there is no muffler there?

[1stGenRex]

how loud are the packs??? does it sound almost like there is no muffler there?

<{POST_SNAPBACK}>

i had a fart cannon with 2.25" from the cat back, and this (the glasspack) sounds better...a little quieter and less annoying at HWY speeds...

I should also tell you that i have a DX, so my opinions are based solely on that fact