Exhaust Guru's need some help!

harley_man · April 22, 2016

Range is a company that makes a device that plugs into your computer and it disables the AFM mode(4 cylinder mode), they also make a device that keeps it in v4 mode longer.

Txjose · April 23, 2016

I felt a bit of a loss on low end with my headers and 3" single exhaust but man that top end wow.

07Softail is spot on. With that much flow you will suffer from an excessive loss in back pressure resulting in a loss of power. I would only do dual 3" if i were running a cam and a blower and even then i still think a single 3" would be better.

Hell i think the 6.2Ls are dumb from the factory with the 3.5" exhaust. Should be a 3" i bet they would make the same top end but more low end.

Sent from my Note 4 on Tapashit

Jon A · April 23, 2016

Well, with headers and a 4" single I gained a ton of low end on my 6.2. I guess I must be doing something wrong?

07Softail · April 26, 2016

Well, with headers and a 4" single I gained a ton of low end on my 6.2. I guess I must be doing something wrong?

How bout some numbers i'm curious?

RT

Badass69 · April 26, 2016

Jon A, on 23 Apr 2016 - 1:21 PM, said:Jon A, on 23 Apr 2016 - 1:21 PM, said:

Well, with headers and a 4" single I gained a ton of low end on my 6.2. I guess I must be doing something wrong?

No kidding lol. I am the stock 3.5" pipe size on my 6.2 and make right around 400 ft lbs to the tires with tune, intake tube and exhaust only..... and that's power starting at 350 ft lbs just over 2000 rpm... and peaking at 4100 rpm as they do stock. 3" pipe would not benefit me in any way, shape or form. Achieving proper scavenging is the goal.... and what I have is working just fine. When I went from the stock catback with it's necks and goofy valve to the free flowing MBRP it was a noticeable gain throughout the power band.... including right off idle. Makes sense getting rid of all the of the elements that just get in the way of proper gas flow.

And if I read one more "backpressure" comment about exhaust I am going to snap ( not really but it's really annoying). Your engine is not a steam generator where a measurable restriction of flow is desirable...... it's not! You want flow velocity and scavenging.... not measurable pressures! And no saying "backpressure" is not the same thing.... it's not even related lol.

Jon A · April 26, 2016

How bout some numbers i'm curious?

Sure:

An increase of 36 lb-ft at only 2000 RPM and 40 lb-ft at 3000 RPM. The other significant "power adding" mod was a CAI which should have little to no effect at low RPM after tuning. I guess people can say if I had stuck a 3" exhaust behind the headers instead of the 4" one maybe I would have gained 50 or 60 lb-ft at 3000 RPM instead of only 40, but it's a pretty fantastical claim that I'd need to see to believe. They're ARH 1 3/4" longtubes, not Tri-Y's or anything odd that could dramatically change the torque curve like that.

In short, I added big-ass cat-back exhaust and headers and gained a bunch of torque EVERYWHERE!

That said, it is a 6.2, I don't think the 4" is going to show much difference either way on a stock 5.3 vs a 3", and dual 3" on a stock 5.3 is certainly more than needed. But the idea going bigger than a 3" single is going to cause large losses of torque on the low end is something lots of people say but nobody actually has a dyno showing such a result.

07Softail · April 26, 2016

Damn... That's Nice. These 5.3's run good but the cylinder heads need a lot to be desired and just don't flow as well as the LT-1 heads. I guess the 4" is suited for the 6.2 definitely not the 5.3. Good Show

RT