Does a 6.2 n/a need back pressure?

[HANK1948]

Iam going to put a high flow exhaust system on my 6.2(something like Dr Lee's truck) I was wondering if a n/a diesel needs back pressure like a gasser or is bigger better. I would like one big single exhaust(looks better on a truck)like 3.5 or do I need some back pressure?

[john8662]

Diesels require no backpressure, because they're not dependent on a certain ratio of backpressure effecting intake vacuum.

Here is mine (although turbo), but you mentioned 3.5", you can do it in mandrel, or not.

http://www.thedieselpageforums.com/photopost/data/503/medium/86_Exhaust.jpg

J

[Craig M]

Dr Lee went with dual 3" exhaust. A single 4" would be closer to that than a single 3 1/2".

[john8662]

Was the system comprised of Mandrel Bent components?

IMO, the 3.5" is overkill, especially on a Naturally Aspirated (NA) engine.

GM used 2.25 from factory, but it was crush bent, so you can imagine that at some places the tubing was at or less than 2".

Carry on!

J

[HANK1948]

Was the system comprised of Mandrel Bent components?

IMO, the 3.5" is overkill, especially on a Naturally Aspirated (NA) engine.

GM used 2.25 from factory, but it was crush bent, so you can imagine that at some places the tubing was at or less than 2".

Carry on!

J

John,
over kill, but its not hurting performance right?

[bigeasy]

Our old 6.2 was a loud pig on straight pipes.
It has 1.5 IN dual pipes (Was factory size). Guess that equals 3 inch single?
Anyway put new mufflers and pipes out from mufflers to tail.
It never ran as good, Smooth and powerfull.

[IUPAC]

More friction is present between the wall of the transport device and the fluid the smaller the dia., therefore less flow of any fluid whether its a gas or liquid. Two pipes/hoses of equal dia. do not equal the flow of one pipe/hose equal to the sum of the two. I honestly don't remember the specifics, but I think that one 3 in. can transport more than two 2.5 in. (thinking in terms of water transport through fire fighting appliances). Does that sound right?

[john8662]

Won't hurt anything, but... Your EARS!

Mine's plenty noisy and it's got a pretty big muffler underneath.

N/A engines are really loud straight piped or with glass packs or large pipes with large straight-trough type mufflers.

I concur with the above comment on the two pipes not being equal to a slightly larger pipe in a single.

The way I see it...

Two 2.5" pipes have to make more bends etc. to make it out of the system with less exhaust volume to continue to push (flow) out the back.

With at least one 3" pipe, the exhaust velocity continues to carry out of the back smoothly, with half the restrictions (bends in the system).

For a N/A engine, I stand by 3" Mandrel system being an improvement over the factory crunch bending 2.25" system.

Banks offers a "Power Pack" for the 6.2 that includes a complete 3" Mandrel System with performance muffler, intake snorkel and hi-flow air filter.

There have been improvements observed with this system.

Another interesting note, the Power Pack exhaust system is the same system used on the Banks Sidewinder Turbo system..

It's sufficient.

J

[C.K. Piquup]

My 6.2`Burb has dual 3" crush-bent exhaust w/DynaMax 6"round straight-thru mufflers.There was a noticeable improvement in performance and,IMO,sound(I`m a hopeless hot rodder).It`s nowhere near load as straight pipes,just a respectable low tone @ idle or cruising and a rumble to a crackle when "in it".I finally stopped hemmin`n`hawin` about going turbo and just did it.The Banks single is a great way to go if you think there`s a chance of going turbo in the future.I don`t like exhaust so load it turns heads only to see a vehicle going nowhere fast.Gotta have the performance to match.I feel my Suburban doesn`t go beyond that mark w/sound.And,it`s got 12.50/35 rubber,4.10s,and the 2nd seat-back loaded with carpentry tools(maybe 1,000#).When hauling the trailer it`s in the "goin`nowhere fast category,but, since it`s a slow climb with the revs it doesn`t crack until it is moving along in it`s power band.

[mrpipe]

i am a plumber and a 3 inch pipe is 4 times larger than a 1.5 inch pipe ,should have plenty flow and some noise, have fun

[AJMBLAZER]

So while we're on the subject, any gain to be had from replacing the stock mufflers with longer cherry bombs?
Both of mine are a bit crusty looking but the rest of the pipe looks good. Figured I could throw some 24" Cherry Bombs on and get a bit better flow.
How loud are we talking anyways? Redneck with dual Flowmaster 2-chambers on his 350 like every Z71 around here or worse?

What about a H-pipe?:confused:

I'm a diesel newb so please be gentle if I'm asking silly questions. :p

[john8662]

So while we're on the subject, any gain to be had from replacing the stock mufflers with longer cherry bombs?
Both of mine are a bit crusty looking but the rest of the pipe looks good. Figured I could throw some 24" Cherry Bombs on and get a bit better flow.
How loud are we talking anyways? Redneck with dual Flowmaster 2-chambers on his 350 like every Z71 around here or worse?

What about a H-pipe?:confused:



My '91 Suburban has Glasspacks (aka cherry bombs), and it's kinda loud when you're getting on it.

It's close to the gasser rig sound with the 350 z-71 you're referring to.

It'll also have that "popping" sound that those thigns are so famous for at higher revs, which in a CUCV geared 4.56, you'll get an earfull of.

Performance?

I dunno.

I've got a new set of mufflers sitting in boxes ready to be installed when I get the exhaust shop to do the entire system. It's quite a bit more peppy that other n/a 6.2's I've had, so perhaps there is a gain. If it sucks afterwards I'll know.

J

[AJMBLAZER]

Eh, it's a thought. I like Cherry Bombs for their straight through flow gains and Magnaflow mufflers for the same reason...

...however I just can't see spending $80 for each Magnaflow to put on the stock exhaust. I'd rather save and buy one when I go to a bigger single setup.
I supposed I could just go with a straight pipe but theoretically a Cherry Bomb would be quieter.

It's hard to convince myself to buy a more expensive aftermarket baffled/chambered/whatever muffler or a replacement stock muffler when you can get something that flows better for $23 each.



Lemme know what you think of the future exhaust setup when you get it on.:cool:



Oh yeah, that's the benefits of the big tires, keeps the revs down. I can actually go 70 with this thing. It's up there in the rpms but not screaming and daily driving 55mph and under it's perfectly happy. However it lacks just about any soundproofing so the engine is quite talkative.

[C.K. Piquup]

When I had my exhaust done,I had it scheduled two Saturdays in advance(the only day they`ll mess with custom fabbing).I show up and they tell me they couldn`t find my MagnaFlows.I told them to just run the pipes and laeve me a straight shot to cut out and I`d put the mufflers on when I got them.IT WAS UNGODLY LOUD!!!!I mean,no amount of throttle would help.This was 3",now.But still,I drove it home and parked it until my mufflers came in from Summit.And I ride a hot rod Harley w/straight pipes.They are quiet by comparison.

[IUPAC]

I had a '98 w/ a 350 and straight duals (2.5") after the 2 cat. convs. That was crazy loud. My 87, 6.2 has straight 2.5 " duals, out the back it is not even close to my old gasser, it has a nice rumble.

[muddymess]

contemplating cutting off the muffs on my stock 82 6.2. hopefully not a mistake.

i enjoy a little sound though,,,,,,,,, straightpiping all my cummins pickups and the psd's i had.

this is my 1st n/a diesel so guess i'll find out :D .......

[john8662]

muddy,

Don't do it, it'll be too loud! If it's non-turbo, it's gonna be loud (way loud), the turbo on the cummins made it quieter. Kind of like my no muffler on my 82 with 6.5 and big turbocharger.

J

[muddymess]

thanks john.

i think i'll follow your advice and not straightpipe. however looking at the muffs from the outside i'm guessing them to be restrictive so i am thinking i may have a couple of 24v resonators laying around that may take their place. [if not a couple 18'' glasspacks] a bit better flow, a bit more sound, but not enough [guessing here] to cause deafness or cause local leo guys to whip out their ticket books.


thanks :thumbup:

[AJMBLAZER]

I've got twin 18" Cherry Bombs on my truck and you can't really tell a difference in the cab. However it's a CUCV so there's virtually no sound deadener.

[DieselCrawler]

Before I turbo'd my CUCV, I had 2.5" duals with cherry bombs, nice rumble to it, untill you got in it, man, then it got LOUD! Would hit a certin RPM range, and the cackle would deffen you. Sounded good, to me... I used the truck as a mud truck, people thought it was a gasser, untill they stood by it when idleing...

Now it has a turbo, and the total lenth of the 3.5" pipe from the turbo to where it exits infront of the right rear tire is about 7 feet, with no muffler... nice turbo wistle, and prettttty loud.... it's served it's time as a quiet work truck, now it's back to playin' in the mud...

[john8662]

My '91 Suburban has Glasspacks (aka cherry bombs), and it's kinda loud when you're getting on it.

It's close to the gasser rig sound with the 350 z-71 you're referring to.

It'll also have that "popping" sound that those thigns are so famous for at higher revs, which in a CUCV geared 4.56, you'll get an earfull of.

Performance?

I dunno.

I've got a new set of mufflers sitting in boxes ready to be installed when I get the exhaust shop to do the entire system. It's quite a bit more peppy that other n/a 6.2's I've had, so perhaps there is a gain. If it sucks afterwards I'll know.

J


Quoting myself here, had to go back and update this thread on the before and after of glass packs verses going back to a factory style muffler on the 1991 Suburban 6.2L.

Well, I got tired of the glass packs, because pulling they're noisy, and revving up the engine resulted in noise, and then popping when 3k RPM and up, so I had a new entire system installed.

Just installed 2 1/4 pipe and the mufflers.

The result?

Loss of performance and pulling MPG.

Before when pulling the drag truck I could get 15MPG pretty easily, was the average, now I'm getting 12 and my performance is down.

Considering a set of DynoMax Turbo mufflers, but I think I'm about done using this 1/2 ton for pulling, should have the 3/4 ton back and running soon enough so I may leave it alone because it's soo much quieter now.

Just thought I'd share...

J

[AJMBLAZER]

I just bought a '89 K5 diesel and I'll be playing this game shortly. With Big Ugly the Cherry Bombs don't matter as there's no sound proofing in the CUCV's and it's loud no matter what. With the K5...not so much.

I've been told the Borla XS series mufflers flow well and are pretty quiet compared to others out there. I'm going to check them out. If that doesn't work out I might go with Magnaflows. I have used them and gotten pretty good results while not being terribly loud...then again I knew a guy with one on his Ranger and he said it was unbearably loud. On my Ranger it sounded like a BMW exhaust.:confused:

[john8662]

Yeah, I'd like to give a try to some dynomax super turbo mufflers.

[AJMBLAZER]

Let us know how they do.

[thirdstreettito]

My 6.2 has stock dual 2 1/4" pipes. Now no mufflers, but it is loud. I am going with bigger pipes when I can afford it because it has that "popping" sound, like lots of air trying to get through small pipes.