What are the advantages of a 4" exhaust ?

[CrewCabDiesel]

I have got a 1st generation 1991 Cummins(see signature for mods) in a Crew Cab with a 8 foot box (22 feet in total length and a 170" wheel base) I am now running a 3" mandrel bent exhaust with a straight thru walker muffler from Stan’s Headers(entire exhaust system length is around 215" . The exhaust comes out like a jet at 1000 rpms or higher. I get around 26 to 28lbs of boost WOT, and can hit 1200degrees EGT (preturbo)empty real fast. I currently get 18 to 25mpg, depending on load and amount of highway driving. With that out of the way, would a 4" exhaust help me get better performance/milage/lower EGTs ?

Thanks

Kyle

 

[Briar Hopper]

Lower EGT's, yes, but better mileage and performance? Not really... The experts have hacked that issue to death on the TDR forums in the past.

Most agree the only two benefits are awesome sound, and lower EGT. It's a totally cool mod to do, but not one of the best "bang for the buck" things to do...

 

[azcummins]

I've got a 98 24V with an EZ and DDIIs and when I'm pulling a decent sized load ~10000# my EGT won't even hit 1100 degrees even when I have it hammered and going up a big hill. In my opinion they aren't worth the $$ unless you are a big bobber and have a super lead foot.



Also- lots of people have turbo spool up issues with the bigger exhaust. Most of those guys would love to go back to the smaller exhaust if they could.

 

[claymike]

What type of spool up problems?

 

[azcummins]

They say that the spool time is a lot greater with a 4" exhaust due to no back pressure.

 

[Rammin On]

I've run a 4" straight pipe for sometime now ..... I don't have any spool up issues ... I'm running a non-wastegated 16cm3 housing at present and it spools up quite nicely ... even while towing ... the less back pressure the better on the turbo . .

 

[Bob Wagner]

Kevin Arts had a spool up problem at high altitude

 

[JohnMcIntyre]

Good things come in threes!!!



1. Lower EGTs

2. Wall of sound

3. Perfect platform for the 5 inch exhaust tip from

Geno's

 

[SlyBones]

I have been wondering a similar thing. Current exhaust is 4" from the DC Test pipe on back. But still the stock 3" down pipe, and back past the transmission to the test pipe is stock 3". Given all the talk around here about what HP a 4" is required, etc. etc. I have left it in this configuration. Recently installed an aFe Mega Cannon. Many have offered up some nice numbers for EGT drops. I did not see much of a drop. ( also have a larryb turbo shield as well as the mega cannon shield that comes with it ).



So the question is, is the 3" setup at the downpipe back, preventing me from seeing the FULL benefit of Air Intake Systems, Turbos, Exhaust Housings, etc. because the exhaust is holding it all up. -- IE Do you think I would see a significant improvement by adding a 4" downpipe, not just because of the 4" pipe, but all the incremental improvements from the other systems now getting to work at FULL strength?

 

[Strick-9]

Sly,



No!



I've had a few different exhausts on my truck and I have yet to see an honest repeatable EGT drop. Same goes for all the magical air filters. But I haven't tried the AFE yet, so who knows.



I wish I could have my 3" straight exhaust back along with all the money I've wasted on believing advertisements.



-Chris

 

[CrewCabDiesel]

Ok, what about a guy with a truck as long as mine ? AT WOT I can fill the inside of a car I am passing with a dark cloud of diesel smoke if they have their drivers side window open.

:--)

 

[Cooker]

I have been toying with the idea of reinstalling my OEM 3" downpipe to see how spool up is compared to the 4" I have now. This thread convinced me that I am going to give it a try. It should be a nice experiment that shouldn't take me too long. So if things are unaffected I am not out too much $$$ or time.



-Ryan

 

[CFowler]

well now im thinking that a guy like me (stock)might get by with just replacing the stock muffler & tail pipe ... what do you think?a good 4"free flowing muffler & tail pipe should make it sound good also.

 

[claymike]

Mine is a stock HO, I do not notice any difference in EGT with the 4”. I do notice it does spool up quicker and the snap at 2100 rpms is gone but there is no power loss. Pulls the 5er the same as with the OEM exhaust.



Mike

 

[ToolManTimTaylor]

Easy answer!

Curl your tounge as you make theese sounds.



Bllllleeeewwwwwaaaaaaaahhhhhhhhhhhhhhhhh duuuuuuulllllllllllhhhhhhwwwwhhhaaaaaaaaaaaaaaaaaaaaDgggwwwahhhhhhhhhhhhhhhhhhhhhdualahhhhhhhhhhhhhhhhhhhhhhhhhhh ... ... . Bark... ..... Bark ,bark ,bark tswewsswwssswssswssswsssswssswsss





<hr>

Truck Bio:

Y2K+1 3500 4X4 Quad Cab 4:10:1 LSD



Somewhat Powerpacked By Bank's (4 inch exhaust,High ram intake,~Minus~wastgate mod to 38 psi,~Minus~ottomind TLC +guages,K&N) ,Blue Chip Premium FMC DTT~93%TC~&~VB~TC Smart controller, Mag-Hytec's Double Deep Trans pan,DD injectors+Van Aken+Autometer Guages. ,Piers Modified PDR HX turbo,Enterprise Engine PerformancePusher pump setup Front End Leveling Kit from Jakit with 255/85R16 BFG http://www.bfgoodrichtires.com/ M/T's Custom Rhino Liner (see Tool Man's truck feature)DeeZee Black Diamond Plate Bed Rails And Tool Box , WAAG Side tubes with kick~outs Mopar Performance accessories-Sill plates-hitch cover-cargo aux lamp'n'Power, Hadley air systems 150 psi comp and air storage. DynaMat Sound deadening applied to entire cab and doors, Check out Tool's Stuff~>Here!<~

N. E. T. D. P

Three worded story ... ..... "over 1350 posts - a new record!"

 

[JIM S.]

Crewcab

Until you have 500 HP or somthing like that you in no way NEED to have 4" and then some will say no... so its debaitable. BUT no one will argue about it not sounding real cool and it is also the one of the coolest things to look under your rig and see that big a** pipe! and on yours it would be even more so with the length invovled. If you can manage to spare the money go for it!!! ... ... ..... here is an idea... ... ..... go from turbo to 3/4 of the way back with 4" and then split it and go to 4' duals out eather side!! that would be one mellow but deep sounding truck! .

just my pennys worth.

Jim

 

[Straight6Jeff]

Um Tim, are you allright? Have you been driving the Subaru too much? Ok, I admit, I've been maiking turbo noises while sitting on the crapper. But that is perfectly acceptable. Anyway, waht were we talking about?

 

[ToolManTimTaylor]

Sory Jeff ..... It Happens. It's just that Sick~Mack~On~Crack sound that I wake up to when the key is released into the run position.



And those noises are the dodge.



SUBE:

Tang chu chuchu chooooooooo Dub dub dub dub dub *Thogtsweeeeeesssswwwwww dud dud dub dub tsweeeewwwwwwuugghhhhaaaaaaaa PSSSSEEEWWW Duhwugahhhhhhhhhhaaaaaaaaaaaaa PSSSEEEWWWW

Dwaguhhhhhhhhhuuaaaaaaaaaaaaaaaaaaaaaaaaaaaa~Da Pssseeewwwwwww

Guahhhhaaaaaaaaaaauuuuungggggggggggggggtsssssseeeewwwwwwwsssssssss ung dub dub dub dub.



Man diesels are sick but ya gota hand it to a FLAT FOUR Turbo ... . 240 Hp (Thats 120 Hp per litre folks )



Anyways off to the can!

 

[backroad]

Just where in the world do you kids come up with this this stuff?



I guess the only possible answer is drugs? Take some and calm down.





Backroad.....

 

[Okie-Go]

I noticed the egt's came down after the 4'' exhaust install.