Truck Exhaust Theory

[MagicMtnDan]

The other is the tailpipes. They hang down pretty low as well. Some folks (Dan included) have just cut them off under the bed after the rear axle.

It was a LOT more scientific than that Will. The pipes weren't just "cut off under the bed" - it was analyzed and scrutinized and then they were hacked off with a sawzall :mrgreen:

 

[Deinonychus]

Rick@Livernois posted a dyno graph when he did a Corsa exhaust install ....

http://www.svtoffroad.com/f91/looking-6-2l-raptor-owner-interested-corsa-exhaust-install-discounted-price-4034/#post33484

Cat-back plus CAI yielding 7.5% torque increase and 9.4% hp increase is a very nice upgrade. The improved torque curve was above the stock torque curve throughout the full tested rpm range. About 20 lb-ft improvement where the two torque curves are the closest - nice!!

I hate to complain about the effort, but I'd like to see a couple more samples (Plagued by heavy statistics use at work. It follows me outside the office).

 

[MarkT]

My personal opinion is that you don't see more dyno graphs because the gains per dollar spent are not that good in some cases.

Especially without a professional tune to maximize the benefits. (I believe the 7.5%/9.4% gains were after cat back, CAI, and a tune... some vehicles can benefit that much from just a tune.)

 

[chartguy]

"there may be some difference in the exhaust theory between the 5.4L and 6.2L motors"

The 6.2L V8 is oversquare, so it revs freely, and will need significantly more flow. I'm ordering a 2012, but I do not intend to make modifications like that. I'll add some fog and driving lights, air horn, emergency lights, siren and fire radio (I'm a volunteer fireman), but owning two F250s and a Bronco (my fifth), I've learned that mods like that are a trade off. I had very fancy headers on a 350V8 1980 K5 Blazer, and I've modded several exhausts. You'll get more noise, probably with a drone (that always seems to occur at highway cruising speed) along with the minor performance boost. For me, the beauty of the Raptor is that you do NOT need to mess with it to get a great performing truck. Best of all, you will not void your warranty. In other words, there's a spectrum of choices, and most of them will make one thing better at the expense of something else. The SVT engineers have done a superb job of making those choices, and finding great balances between noise and performance, with the emphasis on performance, especially high-speed off road performance. I do not know more than they do, and I do not have the budget to try a dozen different replacement systems. Even if you did, I'm not sure that any of them would be a better compromise, and they're certainly not worth voiding the warranty.

 

[MagicMtnDan]

"there may be some difference in the exhaust theory between the 5.4L and 6.2L motors"

The 6.2L V8 is oversquare, so it revs freely, and will need significantly more flow. I'm ordering a 2012, but I do not intend to make modifications like that. I'll add some fog and driving lights, air horn, emergency lights, siren and fire radio (I'm a volunteer fireman), but owning two F250s and a Bronco (my fifth), I've learned that mods like that are a trade off. I had very fancy headers on a 350V8 1980 K5 Blazer, and I've modded several exhausts. You'll get more noise, probably with a drone (that always seems to occur at highway cruising speed) along with the minor performance boost. For me, the beauty of the Raptor is that you do NOT need to mess with it to get a great performing truck. Best of all, you will not void your warranty. In other words, there's a spectrum of choices, and most of them will make one thing better at the expense of something else. The SVT engineers have done a superb job of making those choices, and finding great balances between noise and performance, with the emphasis on performance, especially high-speed off road performance. I do not know more than they do, and I do not have the budget to try a dozen different replacement systems. Even if you did, I'm not sure that any of them would be a better compromise, and they're certainly not worth voiding the warranty.

Looks like we agree :thumbsup:

I don't want to be a wet blanket on this discussion but my theory is that the factory's exhaust is, for the most part, the best exhaust for the vehicle. Could it be more efficient? Sure. Could it be lighter? Sure. Could it make a more pleasant sound? Sure.

But to my thinking the real issues are can an aftermarket company make a better performing, more efficient, lighter, better sounding exhaust? Sure. But how do you (the buyer) know that for sure? And how does the buyer know the aftermarket exhaust maker did anything more than bolt/weld some pipe and a can (muffler) together?

What about headers? Sure, I'll buy a set. Oops. I can't. They're not street legal here in Kalifornia

 

[Deinonychus]

Results thus far:
1. One for Corsa with positive dyno result that included CAI and tune
2. One for SSW with s-tube muffler
3. Some that like the stock exhaust system

A question to the SSW and Corsa choices: Did you replace the stock cats with a high flow cats?

Let it be clear, I understand that many won't risk their warranty, but I'm asking about exhaust theory, not whether you would risk losing your warranty.

What exhaust will optimize for off-road performance? [e.g., if a cat-back would happen to increase hp only after 5000 rpm, but would slightly reduce torque below 3000 rpm, it may not be an off-road performance improvement.]

As I see it, there are not enough Raptor owners yet to tempt more vendors into investing their capital into optimizing Raptor motors.

How many Ford models use the 5.4L and/or 6.2L motors? Maybe there are many already in use. I test drove a high-end F-150 (don't know the model) with a 6.2L motor the day I ordered my Raptor.

 

[Kenny C.]

Just some additional thoughts... It was mentioned above that the engineers are designing these trucks for the best possible performance and I think that it true BUT... They are doing so within certain guidelines and restrictions placed on them by Uncle Sam... Don't kid your self into thinking that given no restrictions the engineers would not be putting out a different Raptor... If you think that the stock set up is the best then by all means stay with it... No warranty issues to worry about, you'll be able to save the mod dough for gas, beer, smokes or what ever and you know that you will have a really cool and fun ride and can sleep easy at nights not worrying...

But I do believe that the mods discussed in this thread will improve the performance of the truck to some degree but I personally don't have the resources to verify whether I see a diminishing return on my investment or not. A lot can be said for the X/cool factor of the sight and sounds of the mods that you make and the warm and fuzzes that a guy can get knowing that he did something that makes the truck more personal to him... I.E. does a custom paint job make the truck perform better??? No but it makes the owner smile every time he gets a "Hey man kick ass paint job" comment from other folks...

I say if you want to make the mod, have the dough to do it and it makes you feel good, then more power to you... If you like the truck stock dido... I'm going to make these mods and all the numbers/charts/dyno readouts a side, more than likely it's going to come down to what I personally think will work the best for me based on taste and cost.


JMO...

 

[Kenny C.]

Double post... please delete...

 

[KaiserM715]

Let it be clear, I understand that many won't risk their warranty, but I'm asking about exhaust theory, not whether you would risk losing your warranty.

If you are talking a cat-back, the only warranty affected would be that for your exhaust system.

If you are talking headers and high flow cats, you would also need a tune for the CEL. Whether that affects your engine warranty or not will depend on the issue and more importantly the service department you are dealing with.

 

[Deinonychus]

If you are talking headers and high flow cats, you would also need a tune for the CEL. Whether that affects your engine warranty or not will depend on the issue and more importantly the service department you are dealing with.

Is most everyone who has long tube headers and high flow cats getting CELs?
Is the belief that this is caused by the faster flowing exhaust or possibly do to a slight amount of air in-leakage that might be aspirated at a joint before the O2 sensors?