AFE+TT= worse mileage???

[ELind]

I finally decided to start modding the truck a little, primarily with a focus on mileage and towing. I found a painted Leer cap for the truck and installed that, and I also installed an AFE intake with the torque tube. Thing sounds amazing, maybe bordering on a little silly, but whatever. I feel like throttle response/spool up is quicker, BUT... . my mileage has gone to 15 and change from what used to be high 17's. This is for the same routes I normally drive, and I don't think I am driving harder. Does this make any sense?

 

[scootergmc]

It could be your camper shell is worsening your aerodynamics. Same principle as putting the tailgate down, you don't get better mileage anymore. Today's trucks are designed with aerodynamics as a major forethought.



I say pull the cap, drive for a tank and recheck the mileage.

 

[JVolpe]

If you still have the stock exhaust, it might help to swap to a high flow muffler. Seems to me that air intake and exhaust are tied together and should be matched to get the best results. A cap can definitely make a difference. I put one on my last chevy extended cab and lost 1 mpg easy. A hard tonneau cover will not drop the mileage much if any, but a full cap will.

 

[JCleary]

I had the same experience, although I am at a loss to explain it. I put on a Banks Monster Exhaust and the AFE with TT, and my mileage definitely dropped noticeably.



I think I must have changed my driving style. That turbo sound is great!!!



If you think the TT is too loud, you can buy a Cool Blue Hose which is a bit more reserved.

 

[ELind]

hmm

I would figure that the caps weight might detract some, but aerodynamically, I would think it should be better, not worse.



With the intake and exahaust you did, you wouldn't think that would hurt mileage either. Very odd... . The cap has to stay, so I guess I will live with it...

 

[Byershome]

Wind tunnel testing shows the cap hurts fuel milage by causing more drag... a hard Tonneau does best and if you have nothing keep the tailgate up. There is a link to the testing here somewhere. The only time I use my cap is when I am hauling the dogs or when I go on a long trip and need the dry/"secure" storage space. I use a tonneau the rest of the time.

 

[RRoton]

You have not said if you are still running stock muffeler or not.

If you are, I would replace it with a straght through type.

That just may bring the milage back close to where it was.

In my opinion, the stock muffler is MUCH more restrictive than the stock intake.

 

[ELind]

Yes, I am running the stock muffler, any suggestions on an aftermarket unit that won't be too loud?

 

[Mathew Clausen]

Take off the canopy

If your normal driving involves freeway speeds - the canopy is the part hurting your mileage. As mentioned above - there is a test report on this site somewhere showing drag with/without canopy, tailgate up/down, etc. A big square flat surface at the back end is a bad thing aerodynamically. This creates a low pressure area at the back, high pressure at the front ... => drag.



Mathew

 

[desertryder]

I put on the long 4' magnaflow to replace the stock muffler.



Nice sound not too loud.



No tellin about the milage becaused it sucked before the change out and I haven't driven her hard yet since then.



Going to Mojave over the Easter week so time will tell.

 

[jsimpson]

Been there. You're unconsciously hitting the pedal harder to enjoy the sound. After a while, you'll let up and the mileage wiill come back.