Exhaust Setup

[SMac92]

On my ITA Civic I currently have a 4-2-1 header which goes into a huge (4ft long) Cherry Bomb muffler and then exits before the fuel tank, which I don't like so it's time to improve. Right now I am thinking of doing a 2.5inch exhaust pipe off the header that leads to a Moroso Spiral Flow Muffler that continues on as 2.5inch pipe that exits out of the passenger side just past the door. Are there any other more effective exhaust and/or muffler options that optimize performance?

Thanks,
Steven

[Ron Earp]

On my ITA Civic I currently have a 4-2-1 header which goes into a huge (4ft long) Cherry Bomb muffler and then exits before the fuel tank, which I don't like so it's time to improve. Right now I am thinking of doing a 2.5inch exhaust pipe off the header that leads to a Moroso Spiral Flow Muffler that continues on as 2.5inch pipe that exits out of the passenger side just past the door. Are there any other more effective exhaust and/or muffler options that optimize performance?

Thanks,
Steven

I'm familiar with the Spiral flow mufflers. Not so great.

If you're intent upon using a muffler I'd look at the Magnaflow series. They have real CFM flow figures which will allow you to calculate what you need. They are well known for low losses in hp/tq.

I think you'd do best with a side exit exhaust with no muffler but you'd really need to do some dyno time to figure out what is optimal.

[JeffYoung]

Call Burns. Model an exhaust and header. Do it once, spend the moolah, and then you don't have to do it again.

[Chip42]

side exit of a 2.5" exhause will leave you with <2.5" of ground clearance inthe rear corner of your car, assuming you are at minimum allowed ride height. most FWD cars sit a bit high so you'll get some of that back, but there's no good reason not to exit it in the tunnel - just make sure you use a good turndown and leave a resonable gap to the tank, maybe add a heat shield (aluminup plate bent and mounted with airspace between it and both the tank and pipe). The only good reason to add length out of the tunnel is if simulation shows that you need it. I'm betting you don't.

there's HP to be had on a D16A6 by getting away from the DCsports headers that are everywhere. I don't know what you have, but I'm betting it's in that vane. I think the header length calcs put the merge on the A6 somewhere around 27" from the head. burns has nice software, there are others in that arena who do that sort of thing, too.

if you're doing the work, might as well use stainless or at minimum get the system coated for heat retention. it helps.

glasspack style mufflers seem to work well in the small confines of the civic tunnel, and shut the noise down adequately. stay away from giant mufflers if you can.

Our FP car has a turn down in tunnel with 2 glasspacks. it's still more of a hodgepodge than a custome rexhaust but it's functional, sounds awesome, runs like a bat outa hell, and it all fits in there without any fuel heating concerns. this is the same chassis as yours (89-91 civic Si)

[SMac92]

Thanks for the tips. I can't afford anything that involves lots of mulah, college requires quite a bit. I'm sure I'll need a muffler, my car sounds like a prod car at idle without one, at high RPM's I'm sure it would be in the high 90 db level. I also want to quiet it down so I don't have to worry if I go to places with low db restrictions unlike Summit. I just wanted a muffler that doesn't decrease my power too much. I bought a Magnaflow race series muffler that is 12in long with 2.5inch entrance/exit pipes. I'll have it turn down after the muffler and have a heat shield installed.

Thanks,
Steven

[Ron Earp]

burns has nice software, there are others in that arena who do that sort of thing, too.


Yes, there are others that do it just as well. PipeMax ($50) returned same info as Burns and actually a bit more with turning for various resonances. When I called Burns back with data and suggestions they were interested, ran their simulation again, then agreed with me there was more than one way to skin a cat and my suggestions might be more on the mark.

Burns has great off-the-shelf collectors (expensive) and a good fabricator can reproduce them, however, that isn't cheap either so you might as well get them from Burns.

[Greg Amy]

I'll have it turn down after the muffler and have a heat shield installed.
A nice little obvious tidbit, but it bears repeating.

This past weekend I was told by a corner worker that I was blowing fuel out the fuel cap during the morning school instruction. That made sense because I could smell it while driving, but I thought it was a student car. I thanked her for coming by and started checking things out, no problem found. The fuel cap released pressure when I opened it. All filler hoses seemed secure. Then after Race 1 Glenn Lawton mentioned I was spewing fuel during the race. I again checked the cap, seemed fine, figured I'd give it a go-through when I got home.

Got the car on the lift last night for maintenance, immediately noticed the bottom of the fuel tank was carbon black, with all the undercoating melted off and paint peeling. A quick look left and I noticed that my exhaust turndown was completely gone. The exhaust clamp was still there but the tip was AWOL. As a result, I was blowing hot exhaust gasses from a 8500-RPM screamer engine directly onto the fuel tank.

I cannot believe I did not melt that whole car into the ground.

I had left the stock heat shields in place in the tunnel, including the one that turned toward the passenger side in front of the tank. That deflected some of the exhaust gasses downward in front of the tank. Without that I'm convinced I'd have had Integra Flambe for dinner...

I'm welding the tip on this time. No more trying to get clever and turning the exhaust away from the sound meter (we're blowing 87-88dB anyway...)

GA

On edit: we're running two of these in series in the exhaust tunnel. Blew 92(?) at Summit Point, 87 at Lime Rock. With exhaust tip.

http://www.summitracing.com/parts/WLK-24236

[JamesB]

Steve,

No need to spend moola, just better setup of the exhaust. A decent magnaflo circular muffler mounted past the shifter area with another 12-18" ending with a 90 downturn to the ground will do and thats what every other ITA civic I have seen is using.

[SMac92]

Steve,

No need to spend moola, just better setup of the exhaust. A decent magnaflo circular muffler mounted past the shifter area with another 12-18" ending with a 90 downturn to the ground will do and thats what every other ITA civic I have seen is using.

Yep that's my plan I'm hoping it will be cheap since it will just be a straight pipe off the headers with a downturn past the muffler. Thanks again for picking me up from Turn 7, even though it seemed to be for no apparent reason.

Steven

[JamesB]

Hey, you thought you where dropping or about to completely loose the motor, why risk it?

[SMac92]

Thought I'd let people know what I ended up doing. After the headers there's a spring joint, the pipe then goes into a 2.5 inch pipe which feeds into a Magnaflow Race muffler (part #14156)which is in the stock muffler location. This then continues for a short section and is bent and pointed out the side (past the drivers compartment) I didn't want it to exit out the bottom b/c it would be insanely loud and this way I don't have to worry about heat problems arising. The bracket for the side exit is adjustable if I ever run into clearance issues.It makes it on and off the trailer fine,so imagine it will be fine on track. The pipe was bent using a Mandrel bender, which doesn't crimp the pipe at all and it maintains it's shape so I see any power loss with the side exit vs. downturn. It is quite a bit louder than before, which is OK because it only read about 85db previously, it almost shakes the ground which is pretty badass. The guy who did all the work talked with me a lot on what I wanted, he tracks a Tercel and knows his stuff so we bounced ideas off each other. He is the guy who made a Spec Miata exhaust that is quieter but produces 2.5hp more than anything else so I trusted what he had to say. If anybody is intrested go to Mandrelbend.com and ask for Greg when you call, he's an awesome guy.

Steven

[jimbbski]

You might want to do some calculations and see if you really need a 2.5 inch pipe. I am using a 2.25 inch pipe on my 1.8L engine and would only go with a 2.5 if I was going to be turning over 7K or I had a 2.0L or bigger engine.

On my last race car, a 5.0L V8, I was making over 300 HP using 2.5 inch pipes from the headers with a "X" pipe crossover and never felt that the exhaust was a restriction.

To big of a pipe will hurt midrange power.

Of course individual cars vary with types of engines, power range, trans ratios, and final drive that may allow a driver to keep an engine in its best power range better then another car. In that case reving the snot out of it might be the best bet!

[SMac92]

My car isn't ever really in the mid RPM range,I'm mostly between 4k and 6800 so I think the large pipe will work well. The header is 2in so I think that may help retain torque and the 2.5in will help it flow. The builder said since I'm at high RPM's most of the time the 2.5in should be good. If not, then it can always be changed I guess, I'm just happy it's going to stay on now...and it sound nasty.

Steven

[shwah]

I know that doing the math will get a more reliable answer on pipe size than thinking a certain size will work well.

You are not doing any harm, and not loosing much, so I would not sweat it at this point.

[EV]

we're running two of these in series in the exhaust tunnel. Blew 92(?) at Summit Point, 87 at Lime Rock. With exhaust tip.

http://www.summitracing.com/parts/WLK-24236I'm using one of these too. Header to straight pipe to muffler to turn down under car and hit 96 at Summit...

[mc-integra111]

I'm sure I'll need a muffler

Sorry, this is obviously late, but I'll provide the info anyway. My B18A1 in ITA trim has no muffler of any kind and only blows in the 95-98 dB range. This meets spec at all the tracks I go to. I tend the think the D16 should not be louder.

[joeg]

2.25" OD tubing is the correct exhaust pipe size for your application.

[mossaidis]

Sorry, this is obviously late, but I'll provide the info anyway. My B18A1 in ITA trim has no muffler of any kind and only blows in the 95-98 dB range. This meets spec at all the tracks I go to. I tend the think the D16 should not be louder.

I have D16z6 with SMSP 4-1 custom header, 2.25" collector into 2.5" midpipe into 4"x22" round magnaflow resonator into 3" downturn. 99db at LRP, 99db at NHMS.

[SMac92]

I think a lot of it is personal preference.As long as the header is good, the exhaust may not have a huge effect. I really can't imagine that I lost any power or torque by having it setup like this. Frankly, I really don't care, I can't afford to do my headers or exhaust again or pay for dyno time to test them. My exhaust is on, stable, and it sounds good and that's good enough for me. I only do 2 or 3 races a year due to college so I just need a car that can complete races so I can keep my license. I do appreciate all the help though guys, it means a lot.

Thanks,
Steven

[raffaelli]

I have D16z6 with SMSP 4-1 custom header, 2.25" collector into 2.5" midpipe into 4"x22" round magnaflow resonator into 3" downturn. 99db at LRP, 99db at NHMS.


I have the same set up just coming from a a6 and using a 3" magnaflow. My car was 99-100-99 at LRP. I still dont believe that it was that loud.