Exhaust-ing Question: 4"x1 or 3"x2?

[BigMo]

Hi folks, another newbie here. Before I get to my question, I'd just like to thank the regulars that post on this site... if it hadn't been for you folks, I wouldn't have been sure how to "build" BigMo; without a doubt the coolest ride I've had in some time!

Now to the question: Does anyone have knowledge about the benefits of a single 4" exhaust over say, a dual 3" exhaust (splitting after the downpipe), using only the resonators (but not the mufflers)? How about back-pressure? Sound quality/noise? Cost?

Thanks for any feedback.

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BigMo: 2001. 5 SWB 2500 ETH/DEE, 4x2, Flame Red/Agate SLT, LSD, 5th wheel slider hitch, Linex bedliner.

 

[Jeff Clark]

I have dual 3"s. Sounds good. Loud on the outside and not as bad as some think on the inside. If you go the dual 3 route, you should open it up to dual as soon as possible and make the Y flow as smooth as possible.

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98. 5 3500 QC 4x4, Driftwood/Mist Grey, 5 spd, 3. 54, 19. 5 Alcoa's, Ranchhand bumpers, DeeZee toolbox, "Physcotty Air", TST PowerMax2, VA, 275's, Autometer Gauges, Centerforce clutch, Upgraded fuel lines (JRE and Aeroquip), MagHytec Diff Cover, PacBrake, Cowl Induction Hood

 

[groundpounder]

any kits out there for this configuration?? I've seen it and it looks awesome!!!!!!!!!

 

[Jeff Clark]

groundpounder, have you seen my truck or just one like it?

A good friend of mine runs a muffler shop and made all the bends himself. Unfortunately it is not mandrel bent.

[This message has been edited by Jeff Clark (edited 02-18-2001). ]

 

[BigMo]

Thanks Jeff. I looked at the space from the turbo down to (and past) the transmission... looks a litte tight for dual in there... where did you make the split? Did you use a 3" or 4" downpipe? And what did you do for mufflers or resonators, anything? How about cost as compared to the typical aftermarket offerings? Thanks for your help.

 

[Cooker]

A 4" pipe has an inside surface area of approx. 12. 2 square inches. A 3" pipe has an internal surface area of 6. 7 square inches. As far as performance, I don't think the dual threes would yeild any benefit vs. the single 4". If it is looks you are after, the dual threes may be the way to go.

The benefit with the 4" may be in the downpipe, if you were considering 4" turbo to tail. The 4" downpipe, from the turbo at 3" and quickly expanding to 4", actually create 1/2lb of vaccume vs. 2lbs of backpressure with the stock downpipe. This vaccume will scavenge the heat, and hence lower your EGT's more effectively.

IMO if you like the look of dual threes use a 4" downpipe and split to dual threes somewhere under the truck as soon as you can make room for them. Otherwise use 4" from turbo to tail. Just my $. 02. Ryan

 

[BigMo]

Thanks Cooker. I appreciate the technical info.

Looks like the 4" downpipe is worth the money. Having said that, the duals may turn out to be less expensive than a single 4" pipe, if (1) I can find a local shop to bend up some pipe and (2) I can source another resonator cheap!



[This message has been edited by BigMo (edited 02-19-2001). ]

 

[Evan A. Beck]

Dual exhaust is just plain cool. Nothing beats the look of getting on it, and seeing a black puff from both sides of the truck.

I had dual 3" on my 98, with a 4 downpipe and no muffler. Loved it. Here's a pic:

#ad

 

[Jeff Clark]

BigMO, the 4" systems that are on the market have a 3" opening and flare to 4" imediately. If you buy the whole system to get the downpipe, you might as well use it. I built my own 4" using a piece of 4" and a 3"-4" expander/reducer. It looked just like what others are offering, although I was told by one that mine would not function like the other systems. I have since put my 3" downpipe back on and it splits back by where the bed and cab meet. I'm planning on a HX40 soon and will install a true 4" downpipe and split to dual threes right where it turns back toward the back of the truck.

BTW, price on mine was $300 with almost half being the chrome 5" tips.

[This message has been edited by Jeff Clark (edited 02-19-2001). ]

 

[BigMo]

Evan, you're right. It does look cool! Looks like it belongs there. Thanks for the pic.

 

[BigMo]

Jeff, what you're saying seems to go along with what "Cooker" was saying above. Evidently, there is a scavenging effect with the 4" pipe IF it is shaped correctly as it expands from the turbo housing.

Another issue is the 'Y' that has to be custom built. I talked to two muffler shops today... neither could handle this (seemingly) simple task.

Still, it seems like it may be worth buying a 4" downpipe, sourcing another resonator, and custom fabricating a 4" to 3" 'Y'. Other than the 'Y' and the 4" downpipe, the rest of the project seems to be fairly low budget. I had a quote of $250 to put it all together, including the muffler shop supplying and bending the 3" pipes.

(Sorry for the length).

 

[Diesel Freak]

Flowmaster makes a "Y". P. N is Y300400, it is 17. 5 inches long and has a single 4 inch inlet with a dual 3 inch outlet(if run in the reverse direstion0

[This message has been edited by cdaledh (edited 02-19-2001). ]

 

[CumminsAholic]

I have a 4" downpipe, then a 4"straight thru "muffler", then a Y into two 3" with 5" tips straight out the back. It looks really cool. I ran for about a month with only the downpipe, after putting the rest on I didn't notice any real difference besides a HUGE reduction in cab noise. BTW, if you wanna reduce noise even more in the cab, get some dynamat or what I used, ice and water dam for roofs and remove the rear seat (Quad cab) and stick it to the bare metal behind it, it helped quite a bit.
Corey

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1998. 5 2500, 4x4, SB, Red Sport, Agate Interior, Quad Cab, O. H. Console, Auto, 4. 10 LSD, Trailer Tow and Camper Special Packages, Mopar Aluminum Nerf Bars, Spray In Bedliner, Pioneer/Jensen System, 255/85's, Bd Adjustable Preformance Box w/boost module, Boost Elbow, 4" Exhaust Split Into Two 3" w/5" cans, K+N Scotty Style, Exhaust Blanket, Bill K's Valve Body, Mopar Tow Hooks, Front Bumper Step, 55 watt Back-up Lights, Etc, Etc... .

 

[Powder Extreme]

I bought just the 4" downpipe from Banks without having to buy the whole expensive **** exhaust, I believe it was $150. The best/ cheapest place I've found for good mandrel bent 4" and 5" is at a Kenworth, Peterbilt, Freightliner, etc. dealer. You can find premade y pipes, all sorts of angles and BIG chrome tips pretty reasonable.

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2001 Quad Cab Dually, ETH, SLT Plus, 275 injectors, Banks Power Pack half way in.

 

[pcorssmit]

I used one of the Flowmaster Y's on the Blazer and was happy with it. Its easily shortenable if need be, mine goes straight into the muffler (dual 2 1/2s off headers, y'd behind t-case, into Flowmaster Big Block muffler).

Pete

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'97 2500 CC 4X4 5spd Sport
'83 K5 Blazer 350 TBI (ex 6. 2), 39. 5 TSLs, 3" lift, Dana 60/GM 14 blt, Detroits

 

[Todd T]

BIGMO stans headers sells just the 4" downtube

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Todd,
2001 Q-cab SB 4x4 5spd 3. 55's, A pillar Boost/EGT,Jardines 4" turboback kit, and more to come...

 

[BigMo]

Thanks for all the great feedback! This is my first post on TDR and all I can say is - what a FANTASTIC bunch of folks. I think I may enjoy TDR almost as much as I do my truck. . . ALMOST!

Thanks again for all the information and helpful ideas.

BigMo

Oh, yeah... I know this is a subjective question but, how much louder is the exhaust WITH the resonator but WITHOUT the muffler? Also, what's the sound quality like, i. e. , deeper sound, raspy, rattly, etc. ?



[This message has been edited by BigMo (edited 02-20-2001). ]

 

[Cooker]

Steve StL. has no muffler with a res on his truck. I haven't heard it personally, but from what he says it not much louder, but a little deeper tone.

 

[Evan A. Beck]

BigMo, I tried that very thing on my 2001, just for fun. The resonator really cut the "bark" off the straightpipe sound, but keeps all the turbo sound. Chirps pretty good at idle... Try it out. #ad


I decided to yard out the resonator, for the sole benefit of having a louded truck. The louder, the better! #ad