exhaust size, inlets, fit?

[tbomb]

ok, so a week ago i called summit and wanted to buy a flowmaster 50 series w/delta flow. the guy looked up which one i would need in the computer, and told me to get the single inlet, single outlet, and i wanted 2.5" pipes from teh cat back (im going to have the pipes custom run like a lot of people on this site do.) so i get the muffler a few days ago, and i took it to my local muffler shop today (which is really just a gas station/service station that does exhaust work -- its the best thing i have up here at school.) the guy just looked under my truck for like 30 seconds and said that theres no way i could fit 2.5" piping in there; he said that i couldnt go any larger than stock, which he said was 2". he also told me that the stock muffler is a dual inlet.

i know nothing about exhaust, but my friends do and they said this guy was probably full of sh*t. i have a couple of questions...

1) is the stock muffler a dual inlet?...and if so, do i need to return mine for a dual inlet muffler, or is there something else i can do?

2) can i fit 2.5" piping in there from the cat back?...if not, then whats the largest piping i can fit? (is stock 2" or 2.25"?)

3) does anyone have a 98 sport 4WD SOHC (or similar model) that has gone with larger exhaust?...id like to know if what i want can definately be done or if someone already has done exactly what i want. (i thought ive seen people with the same truck as me who had larger exhaust on the site, but i dont remember where.)

ive already skimmed through hundreds of threads on the topic of 'exhaust', and i was making no progress.

PLEASE HELP!!!

thanks a ton in advance to anyone who has advice/comments/suggestions/answers/etc.

 

[Alec]

1) You have the SOHC motor and as far as I know, all X's with the SOHC have a factory dual inlet, single out muffler.

2) Your stock tailpipe I believe is non-mandrel bent 2". I have non-mandrel 2.25" on mine using the stock hangers. 2.5" should be able to fit no problem using the stock hangers. Although with the SOHC I probably wouldn't go larger than 2.25". You need that extra backpressure to help with torque at lower RPMs.

 

[tbomb]

thanks alec. i just called summit and they have a 2.25" dual inlet with a 3" single outlet (thats the only size outlet they have.) and i called my exhaust shop at home (not the idiots that are up here at school), and the guy said he could definately do what i want. hes going to put an adapter on the outlet of the muffler to go from 3" to 2.25" ( <-- thanks for the advice on pipe size.)

to everyone else: if anyone still has comments/suggestions, please post them.

thanks in advance

 

[Alec]

cool, glad I could help.

 

[tbomb]

actually, i just remembered that the tip i bought is for 2.5" pipes, so i have to go from 3" on the outlet to 2.5" not to 2.25". but i have another question:

is this gonna mess the dynamics of anything? like, going from a 3" outlet to a 2.5" pipe with an adapter, is this going to affect my performance at all? and since the muffler is designed to have a 3" opening, and im converting it to 2.5", since im forcing the same amount of air through a smaller opening, am i going to get a popping noise, or too much backpressure or something?

now that i think about this, im starting to feel very uneasy about it.

i hope someone with the same truck as me replies. i just want something easy and direct that sounds good. i dont want to mess around with adapters and guessing what the outcome is going to be. i dont have the money to keep switching around exhaust systems.

thanks

 

[wpurple]

backpressure VS torque

Can someone explain the technical reason why you do need backpressure to maintain torque?

Thanks,
Kurt

97 Sport 4X4 OHV

 

[Alec]

Tbomb, you should be fine with a reduction to 2.5" as long as the install is very good. If all the joints are welded or butt-flanged together (with gaskets), they will hold up well. Compression sleeve style joints to not work well with exhaust, you will have leaks. This is when one pipe is slid into the other and a ring is placed around the outside pipe to hold the two together >>no, no.

As for backpressure and torque, my understanding is this: backpressure causes the engine to work a little harder to push the exhaust gases out of the cylinders. This pressure on the exiting gas exerts more force on the piston that translates into more force going into turning the crankshaft. Force into turning = torque.

 

[tbomb]

well, ive thought it over, and ive decided to not go with the flowmaster setup. just too many guesses, things that shouldnt be, etc. i looked into dynomax and they make the perfect muffler for me. its a dual inlet, single outlet with the outlet size = 2.5". (if anyone else is interested in this muffler the part # is 17671.)

thanks everyone for the input.