Mostly the efans help in city that I've noticed. They really "pep it up" too as the throttle feels a lot more responsive than before.

I have a bed cover (hard 'glass one), but I have not taken it off to test highway mileage with/without it. To lazy for that... MythBusters tested the tailgate down myth and said that in their tests they lost mileage with it down due to more turbulent air swirling after the cab. Maybe you could get them to test the bed cap idea...

 

15:1 isn't very lean at all. It will be happy to run at 17:1.

Volumetric efficiency has nothing to do with AFR. VE is simply the percentage of the cylinder that gets filled with air.
To make numbers easy, let's say that you have an 8 liter V8.
The density of air is ~1.3 grams per Liter, but to make numbers easy, lets say it's 1 gram/liter.

If you got 1 gram in a cylinder, it would be at 100% VE. Most NA street/OEM cars are at about 80% today. Most bolt on cars around around 90-95%. Serious race NA cars around 100 to 105. NASCAR runs around 130ish. F1 is around 190 IIRC. Boosted cars easily top 125%.

VE = Torque for a given engine size.

Air:Fuel is just that, the air to fuel ratio. This magical 14.68:1 you hear about is an emissions number. Leaner = more NOX, Richer = More HC's. 14.68:1 is just where they cross due to chemical properties of fuel and air.




Equiv ratio of 1.0 = 14.68:1

 

They're 275/70- 16's, originals were 245/75-16. I wanna go 265/70-16's. Also thinkin' about dropping the truck; yanking the blocks outta my rear and easing off the torsion bars some- still wondering how low I can get away with on the current sized shocks, don't mind spring for a couple toxics for the front, I'm already running Pro Comps as it is..........

 

i have a shell on my 02, i average 20 on the highway and 15-16 in the city

 

TreyZ28...you are a ******* idiot.

It seems to me that you make an attempt at logic.....

You can talk about AFR and VE all damn day.....but AFR and VE DO NOT have a damn thing to do with the amount of load ON the engine. If, on average, you can lessen the load on the engine then you can, on average, increase the fuel efficiency.

There have been SEVERAL people that can get the same results by going to electric fans.

You need to think from a more realistic standpoint. A dyno (a "lab" environment) is a crude attempt at simulating a real world activity. The results from the test he and others have done is repeatable. Dicking around and talking about VE, AFR, dynos, and "Combustion Efficency" does not change the results of this particular modification.

Lab results are great.......if you live in a lab.

 

So out of the blue your cussing a guy for a statement made 5 months ago?

 

Wow kinds harsh on the guy for posting comments. Not like we are sending someone to the moon here.

 

It irritates the hell out of me when people try and use the "I'm a ....insert-profession-here...and I've insert-irrelevant-experience-here" argument when they are clearly wrong.

Harsh?.....he's had 5 months to admit that he was wrong. If he cries over this...he has more problems than just admitting that he's wrong. If you come on here and post comments like he did....then you should expect this kind of response.




I can see where there is alot to gain in the tune. Does any know if there is a way to modify the tune so that you go into 4cyl mode sooner? Or maybe stay in 4cyl mode longer? I don't know, but I would think that GM has left some room for improvement here as well. I know that this will not apply to you Ferocity02, but it may apply to the others in this thread. Any thoughts?

 

I just read through this thread and I'm amazed at the mileage many of you are getting. I have a 2007 ("Classic") C3500 with a 6.0/4L80E and 4.10's. It's an extra cab/long bed and I've seen a best of 13.045 mpg and average about 11 in combined city/highway driving. I've seen an average of 8.2 while pulling a 24 foot enclosed trailer through the mountains of WV, PA and MD (from Ohio and back to Ohio). It was about 5,500 lbs going out and 9,000 coming back. I was towing on cruise control at 65 mph the whole way. I do not have a cap or a cover on the bed. If I could find a way to get 17 mpg, I'd be thrilled. If I could see 20+ like some of you (I know they are 1/2 tons mostly), I'd throw a party. Unfortunately, it doesn't seem likely with my truck. It's just over 6,000 lbs with me and a tank of gas.

 

gas or diesel ? Is it tuned ?