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Author Topic: Duel exhaust  (Read 3918 times)
Rick 74 MC-8
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« on: May 05, 2010, 01:41:25 PM »

Has any one here with a na engine put duels on I want to run two 3" pipes from the manifolds Thu mufflers and out.  Don't want it to be to loud but a low rumble would be nice. I think After removing the otr compresser there would be plenty room.  After reading the earlyer post about straight pipes and performance and MPG boost I think there must be a happy medium. Besides maybe I could pick up some extra revenue blowing the leafs out of the curb lol. Just thinking out loud


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« Reply #1 on: May 05, 2010, 06:03:42 PM »

3" doesn't sound very big. How about 5"? How big is it off the manifolds?

JC
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« Reply #2 on: May 05, 2010, 06:41:31 PM »

Has any one here with a na engine put duels on I want to run two 3" pipes from the manifolds Thu mufflers and out.  Don't want it to be to loud but a low rumble would be nice. Just thinking out loud


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Rick,
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Rick 74 MC-8
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« Reply #3 on: May 05, 2010, 06:51:13 PM »

The manifolds are 3" Does anyone have part # for mufflers I might jump 4" seems they are more common Does anybody know if they make a 4" manifold of a source for used manifold  street side will work good curb side will word but a different style would make a cleaner install


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« Reply #4 on: May 05, 2010, 11:02:26 PM »

In the auto world they shy away from just upping the pipe size.  Seems that  the size increase makes the gas heavier due to the reduced temp that results from gas expansion.  This "problem" is part of the reason that wet wrapping the turbo and manifold and piping up to the muffler increases power and efficiency. I know that back pressure kills the D power but can it be any worse for the gas engine?  I had charts and graphs for my Z car and they showed serious drops in dyno power for an increase in the header pipe diameter and similar losses for increasing the ex tube dia by only 1/16 over the opt.

Getting rid of the muffler is a sure fire good move all around.  Problem is that if you maticulosly engineer the system you can get equal perf from a muffled system.  Lots of spendy engineering on that.

But what I would really like to hear is "are we better off going to twin 4 inch or 3 inch if the manifold is three inch"??  Hope that gets answered.

John
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Rick 74 MC-8
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« Reply #5 on: May 06, 2010, 02:16:28 PM »

Just measured again manifolds are 3.5". The current exhaust takes the two 3.5" into a 5" then into muffler then exits  4.5" Its like a leaf blower. Just seems like duels would get rid of the constipation The current muffler is fine I need to do some other exhaust work Any was looking for real world experience

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« Reply #6 on: May 06, 2010, 03:05:10 PM »

Rick,

The straight thru pie will be very loud....from what they say.  I listened to the film of one running and it seemed ok  to me.  What I do know is that if you split the system and run a separate pipe for each bank, well, the noise goes up dramatically.  Didn't that film n the board show the engine running straight out the manifolds and then he re-posted with them run into a common 5 inch pipe.  You be the judge  Its been done and recorded for your listening pleasure.

A turbo quiets it down some.

What do you think?

John
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« Reply #7 on: May 06, 2010, 03:15:53 PM »

What is different on the manifold you need Eagle uses a cast 90 on the curb side and just regular truck mufflers same as C65 Chevy truck with the 366 or 427 engine, duals on a 8v71 will help and they sound nice too.



good luck
« Last Edit: May 06, 2010, 03:19:01 PM by luvrbus » Logged

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Rick 74 MC-8
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« Reply #8 on: May 06, 2010, 03:36:08 PM »

Thanks luvrbus that's what I was thinking I don't want straight pipes  just want it to breath I could live with a rumble I but not draw any more attention when pulling into a campground and maybe pickup a little milage and performance Maybe wishfull thinking but shouldn't be that hard to do



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« Reply #9 on: May 06, 2010, 05:52:53 PM »

If you already have a good 5" muffler, why not go for dual 5"?
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« Reply #10 on: May 06, 2010, 06:16:44 PM »

We have dual exhaust on our 8v71N. I thought they would have duals, guess not. I think it's 3" in and I know it's 3" out. Not sure of the brand of muffler, because they were on there when we bought the bus. It sounds good and not too loud.

Paul
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« Reply #11 on: May 06, 2010, 07:01:46 PM »

You could try Pittsburgh Power.  They run a high performance diesel shop and have designed free breathing mufflers for big trucks.  I don't know how much 2 stroke Detroit work those guys do but they were big into N14 Cummins and some Cat motors.

http://wwwpitsburghpower.com
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Dennis Watson
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« Reply #12 on: May 06, 2010, 07:04:28 PM »

sorry but that link won't work.  Try this one.

http://www.pittsburghpower.com
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Dennis Watson
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Rick 74 MC-8
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« Reply #13 on: May 08, 2010, 11:02:40 AM »

While doing some research om my back psi vs HP I came across some intresting reading Might be of use in findind cfm scroll to pages 108
http://www.eigenbrodt.se/webmotor/nyhetsfunktioner/f110028%20medium%20and%20heavy%20duty%20exhaust%20catalogue.pdf

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« Reply #14 on: May 08, 2010, 12:12:31 PM »

Rick,

The Donaldson site was neat.  I spent 45 min going back and forth in there.  Thanks.

I have always thought that "back Pressure" should be a percent loss per psi.  No doubt I am wrong but I too have that question.  I hope you will post the results.

Thanks,

John
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« Reply #15 on: May 08, 2010, 02:00:32 PM »

I have run thousands of miles with a straight through, no muffler 5" pipe on my 8V71N.  Way too loud!!!!!  Painfully loud, but very noticeable gain in HP.

FWIW!
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« Reply #16 on: May 08, 2010, 02:40:21 PM »

Beware, most all of the videos of running engines without mufflers are on idle and free wheeling with no load.

And the camera does a good job of making it difficult to gauge the true noise level.

Way different from what noise will come out at full throttle on the road.

You can only barely get a blip of REAL noise by goosing the throttle, the governor backs the fuel rack off almost as soon as it opened, as it spins up to speed too rapidly for you to get the full effect.

Just so long as you do a little experimenting before committing dollar$ to an unexpected ugly baby...

happy coaching!
buswarrior


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Rick 74 MC-8
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« Reply #17 on: May 08, 2010, 03:03:48 PM »

For the time being I think I'm just going to repair the 5" 90 going into the muffler and see if I can in large the 4.5" muffler outlet.  We have a trip planed for June. I can check mpg and performance and decide if I want to take things further I know I don't want straight pipes.

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« Reply #18 on: May 08, 2010, 05:11:13 PM »

BW

I was parked next to a MCI9 years ago.  Never saw the owner in the three days that we were neighbors.  I peered in the screen on the passenger side and could only tell that it looked like a 8V92.  It was a DD though.  He must have aired up using his genny and run his block heaters in prep for starting and making a fast getaway.  He fired off at 8 AM and I was knocked from my bed in an ignominious pile on the floor.  It was a straight pipe,,,must have been...and, HOLY CRAP BATMAN!!!!  But he lit her off and pulled out in the same instant and if I made that much noise I would beat a hasty retreat,as well.  Maybe he was a real little guy without a gun and was tired of being beat upon. Who knows but had I been within arms reach....well that is another fiction.  It had duals o it cause one ex pipe came out the passenger side where I was sleeping before my heart attack.

Still more power is a really attractive thing.

John
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« Reply #19 on: May 09, 2010, 08:07:37 AM »



My Stock Tailpipe was damaged when I bought my bus, looked like it had been backed into a curb.  I took it off and bought a 5" Chrome tip at the truck place with a slight 900 exit.  I had some pieces of steel and made spacers to bolt/clamp it to the muffler extension.  Made a noticeable improvement in fuel use over the crumpled one Wink.

I do think I need to clock it at about 450 to the outside so I can observe smoke in the mirror better.
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« Reply #20 on: May 09, 2010, 11:26:51 AM »

I do think I need to clock it at about 450 to the outside so I can observe smoke in the mirror better.

That will also help prevent stirring up as much of a dust/leaf cloud when driving "off road"  Jack
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« Reply #21 on: May 09, 2010, 01:29:34 PM »

My muffler was shot so I built a 5" J pipe to replace it and came off of it with a Borla 4" ss straight through muffler designed for racing. I exited it out the side at an angle so I could see the exhaust in the mirror much as the original exit was. It's still pretty loud. Generally by the time I get up and moving around it's time for the neighbors to get up anyways! Cheesy One thing good about it is nobody sits on my left rear for long when we're rolling down the interstate!
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