Exhaust Position?

Bruiser

Getting ready to run the exhaust on the M880. Since I moved the fuel tank to the bed I have plenty of room to run dual mufflers with the Thorleys so I won't have a crossover pipe to get in the way of the driveshaft.

My question is should I dump the tailpipes right after the mufflers or run them in front of the axles or behind the axle. I'm going to tuck everything up high and close the frame rails as possible. Any other tips or hints would be great. Oh yeah, going with 2.5 inch dia. pipe with 40 series flowmasters.

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1985 Dodge Crew Cab Cummins--Full Resto Underway....
2015 RAM ECODiesel--DD/Tow Rig

primetimek5

Dump The Pipes After The Axle. Due To The Exhaust Will Heat Up The Fluid
& Cause It To Heat Up Faster. It Will Also Streeeeetch The Emergency Brake
Lines.
It Happend Already To Me.
I Really Missed That Sound.

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bye bye k5 build.

OldGoat

Sometimes the crossover pipe is needed for equalization of exhaust gas pressure and may affect your low end torque. I am getting away without it on my 318. My exhaust pipes end 1' in front of the rear axle and have turn downs. They are 2.5" If you go on over the axle and turn them down or to the side it should be a little quieter.

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Official "WEB WHEELER" and arm chair Quarterback.

Bruiser

Does the crossover pipe have to be right after the collectors? Can you maybe run it a little futher down stream before you get to the mufflers? How much torque difference is there to loose without the crossover pipe? Are we talking major difference??????


primetimeK5---Thanks for the tip-didn't even think about it heating up the diff fluid or getting the e-brake or brake lines hot.

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1985 Dodge Crew Cab Cummins--Full Resto Underway....
2015 RAM ECODiesel--DD/Tow Rig

OldGoat

Actually there is a formula for this and it is Cu. inches divided by 9.7 so 360/9.7 =37.1 inches from the header flange would be the optimum spot for your crossover or 111.3" from the exhaust header flange. The reason for skipping the 74.2", it is the second harmonic and the backwave sort of cancels at that point. It is a complicated process to explain but the math is straightforward which is rare. Of course there are problems with a lot of vehicles with enough room at just the right spot so the crossover gets put wherever on most vehicles. By the way those figures are for 1.5" collector tubes so if yours are a different diameter just figure the percent of change and adjust the formula.
Does it work and is it worth it? For an example my 98 model Harley with a 88 Cu. inch engine had pipes about 27" long with a crossover right at the 27" mark and then Screamin Eagle mufflers and made 97HP and 97 lb ft of torque, those pipes were perfect. I wanted more sound and went with 36" straight ARII drag pipes and got a great sound but lost 5 HP and 10 lb ft of torque, needless to say I went back with the 1st set of pipes. I do plan on getting my crossover in but it is way down on the list for now.
IMO with a doubler you are going to have so much torque going on it will be a mute point.

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Official "WEB WHEELER" and arm chair Quarterback.

Bruiser

How did you know?

Lots of good info OldGoat , once again your wealth of knowledge exceeds my little brain.

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1985 Dodge Crew Cab Cummins--Full Resto Underway....
2015 RAM ECODiesel--DD/Tow Rig

JDKing

i was told by an old hot rodder to paint the ex pipe about 2 feet after the flange drive the piss out of it and cut the holes where the most paint burned off and crossover from there. it workded good on my 84 mustang back in 86...

OldGoat

Just a good guess on my part. Am anxious to see it in action.

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Official "WEB WHEELER" and arm chair Quarterback.

Bruiser

Me too! Ordered the doubler today!

__________________
1985 Dodge Crew Cab Cummins--Full Resto Underway....
2015 RAM ECODiesel--DD/Tow Rig