Exhaust Question

[Jason_25]

My dad and I were having a discussion about modified exhuasts a few days ago. Basically, what it came down to was that he doesn't think a more free flowing exhuast will increase performance or gas mileage on my truck.

His reasoning?
He says Ford gets fined alot of money each year for making vehicles that don't hold up to gas mileage requirements and such. If an exhuast/intake modification really increased gas mileage, why wouldn't Ford offer it from the factory?

I also found more info to back up my dad's claim. I went to the exhuast shop to inquire about getting a custom exhuast done, and the guy at the exhuast shop went to inspect my current exhaust and he said "what's wrong with what you've got?". I said "nothing, I just want more HP and gas mileage". He then proceeded to tell me about how a more free flowing exhuast would not benefit me at all (HP, MPG, or otherwise), and about in his glory days when he had a race car that would do 150 MPH and so on and so forth with only a 2 inch pipe, and how great it ran with a fairly small exhuast.

What the heck? This seems to contradict what everyone says on this board. I'm not saying I disagree with you guys but can someone please clear this up for me?

Thanks,
Jason

 

[aldive]

Sorry to burst your bubble, BUT, hot rodders have been replacing stock wxhaust and intakes for 60 years to get gains in HP as well as mileage.

The Explorer responds well to a cat back system as well as a KKM type intake.

 

[yob_yeknom]

Well, your dad probably just doesn't want you having a louder exhaust and the muffler guy probably just doesn't want to take the time to do it. They are both wrong.

My ACTUAL EXPERIENCE proves them wrong. After installing my Borla cat-back, I was able to spin tires very easily and got a 4 mpg increase! Find another shop to do it or just buy a cat-back system and install it yourself.

 

[expo5.0]

imo that is partly if not mostly true. if you have the ohv your engine isn't flowing that much air. the stock 2" diameter pipe (i'm assuming thats what it is) is capable of flowing easily as much as your engine at wot. a new muffler will probably help, but very little unless other mods are done. this is for the same reason- your engine doesn't flow that much air and your muffler probably does an adequate job of keeping up. if you do mods on the intake side your engine will flow a little more and maybe benefit from exhaust. its hard to guess or know just after what mods you would need a higher flowing muffler or a larger pipe.

as for why ford doesn' t put higher flowing exhaust on- that is because of sound concerns. not so much on a ohv, but on their higher performance engines they attempt to make them run as quietly as possible most of the time. but fairly loud under heavy throttle. most of their v6s and all of the v8s will see noticeable gains with a new muffler ( and sometimes larger diameter pipe) but they will be much louder. hope that clears it up a little.

 

[addkev]

True, you are only going to suck in as much air as you can blow out, and vice versa. So, if you upgrade to a KKM, then I would definitely get a upgraded exhaust. I can only speak for my experience. I put in the KKM thinking it would blow my mind. It was louder, but i didn't really notice any difference. I added the exhaust and my truck came to LIFE. It was so much more fun to drive. Then I added 31" tires and it is back to what it was before the exhaust w/ the 235/75's.
Just to prove it to yourself, try this. Crawl under your truck, Look at before your muffler. You have two 2-1/4" pipes going into the muffler, that is 4-1/2" of exhaust that is huge! Then you have the muffler, most likely your muffler will be either rusted or changing colors at different spots, that is from the heat building up in that spot (restriction). After your muffler, you go down to 2" pipe, 4-1/2" of pipe before muffler to 2" of pipe after and somewhere around the axle, you have a resonator, tuning the exhaust note to the Ford engineer's liking, again restriction. Take all that out from the cat's back, add a high flow muffler, and continue the 2-1/4" pipe straight back and it is obvious that it is advantagous. And besides...
For $200 your truck will sound like a real truck.

 

[TarHeel085]

he doesnt have two 2 1/4 pipe going intot sure on his. only one not sure what size though cause he has the OHV.

 

[addkev]

Are they running one cat on OHV's?

 

[Jason_25]

Nah I have 2 cats. Both pipes that come from the exhuast manifold combine before the 1st cat.

 

[RTStork]

Originally posted by yob_yeknom
After installing my Borla cat-back, I was able to spin tires very easily and got a 4 mpg increase!

I also noticed a big horsepower and torque increase with my new exhaust. Although I only gained 2 mpg, I'm still pleased.

 

[Jason_25]

Thanks for the responses guys, I wanted to bump this up again to see if I could get some more responses to show my dad.

 

[jsdean]

You definately get a HP boost, that's for sure. MPG maybe, I didn't but I'm sure the more constant flooring to hear the fun tones of the exhaust contributed to that.

 

[Spectre]

I'm with jsdean on the gas mileage thing. You may see some improvement if you're able to drive it the exact same way you did before the exhaust, but let's face it, the sound if half of what everyone looks for. Once you get that sound, it's kinda hard to stay out of the loud pedal.

Power-wise, I totally felt a difference. On my SOHC, it pulls a little harder once you get over 3000. Under that, I can tell I lost some torque, but being an OHV, you shouldn't have a problem with that.

 

[Jason_25]

He's still not convinced........

My dad still thinks that there is no way anyone would get a noticeable gas mileage increase from the exhuast change unless they were running WOT all the time.

He also says that the HP increase is negligible because it would also be at WOT. He thinks that horsepower during everyday driving would not change at all.

Keep this is mind: my dad isn't a stupid guy, he has his master's degree in Aerospace Engineering and works for the DOD.

But by the way he explains it, I just can't justify getting a catback exhuast done for my truck when all it will do is make it louder.

 

[espnfreak]

I got my Borla, and had similar results like john.
Borla is good for several reasons:
1.) Stainless steel (wont rust)
2.) MillionMile Warrantee
3.) Increases hp
4.) Increases Gas MPG
5.) Gives truck a better sound

Check borlas website, but when i got my borla there were just tons of advantages they used as selling points. i tend to think a borla or a flowie (good exhausts) would definately do something beneficial

 

[yob_yeknom]

Originally posted by Jason_25
His reasoning?
He says Ford gets fined alot of money each year for making vehicles that don't hold up to gas mileage requirements and such. If an exhuast/intake modification really increased gas mileage, why wouldn't Ford offer it from the factory?

Well, as smart as your dad may be, his reasoning is completely wrong. Ford doesn't get fined for not meeting mileage requirements, they can't produce the vehicle if it doesn't meet requirements. They do as little as possible to meet those requirements and nothing more.
Why?
PROFIT and not every customer wants the extra power if it requires more noise. If it costs X amount to make a 2" exhaust with normal bends, then it will cost that much more to use larger diameter pipe and do mandrel bends. So if you earn A amount of money off the vehicle and you use the larger pipe you now have A-(X+cost of better exhaust) so you now only earn B amount on each vehicle. You take A-B x millions of vehicles sold, and you lost a butt load of money to go with the better exhaust that you are not required to have.

Complicated explanation, but did it make sense?

 

[Jason_25]

Thanks for the explanation John. Personally, I beleive you guys in here. There is just too much evidence in favor of modified exhuasts.
1 more question though:
Is the explorer's stock exhuast tuned?

 

[addkev]

I don't know if you would call it tuned, but it does have a resonator, mine was over the back axle.

 

[aldive]

Re: He's still not convinced........

Originally posted by Jason_25
Keep this is mind: my dad isn't a stupid guy, he has his master's degree in Aerospace Engineering and works for the DOD.

Arn't these the people who brought us Viet Nam?

Seriously, your Dad is mistaken in his logic, cat backs do work.

 

[yob_yeknom]

Originally posted by Jason_25
Is the explorer's stock exhuast tuned?

I would assume so. It should be tuned so that there is no resonant frequency. Some use a resonator which will restrict airflow, some don't. (mine didn't have one)

Any cat-back system you purchase will also be tuned without the use of a resonator.

 

[Coke734]

Dual, right?

Okay, I'm definitely in favor of new exhaust, and correct me if I'm wrong, but you're all talking about dual exhaust right? Thats what I want to get, but when I took my X in a couple months ago the guy @ Mr.Muffler said that with the spare where it is, I wouldn't get ANY performance gains, just the sound. Did you all take out the spare, and if not, how did you rig it up for best performance? Do you have any under-car pictures of what goes where? Thanks