Looking to get a few more MPG

[djcronos]

Hi all,

I've browsed these forums over the past week now, and read a lot of posts about people who are trying to get 30+ MPG on their Hoes with Hydrogen fuel and all that other crap, but I'm not trying to get unrealistic MPGs out of my new Hoe.

I have a few things in mind I would like to do to my vehicle, and wanted to know if any of you who have done the same have noticed a few extra MPGs. I was thinking of getting a cold air intake, the Flowmaster 50 Series muffler, and perhaps new exhaust to go with the muffler. A friend of mine mentioned something about a "chip" that could get me better gas mileage, but I haven't seen anyone here mention any of this.

Again, I'm not looking to get some crazy increase in MPGs, I'm just looking for 3, 4, or maybe 5 extra MPGs. Will I be able to achieve this if I do the above mentioned upgrades?

Also, I was looking into the K&N Cold Intake that was reviewed on this web site, and I noticed that it's not street legal in California. Are there ones that are, that will still give me the same increase or something similar to the K&N? The other option is for me to just swap it out with the stock filter when smog time comes.

All thoughts and comments on this topic is greatly welcomed! Thanks in advance!

 

[LVYUKYUK]

Check out the upper left hand side of the page. Black Bear does some PCM tuning that could give you a bump in HP and MPG. A cold air intake from K&N is available that is street legal, but from other posts, you will find that it does not really give you better MPG, and the HP gain they talk about is at full throttle. If you did the CIA with a cat-back system I'm sure you could see maybe 1-2 mpg, but only after you took your foot off the right pedal with all the newfound noise and giddyup. Now, I have heard also that all these mods are cancelled out by the computer after a couple tanks of gas as it adjusts to a new fuel mixture.

Bottom line, do a CIA and exhaust for the bump in HP and 'coolness' factor. Your MPG may not improve as you wish. I would assume though, if you combined all three mods, you would see a little better MPG, but how long does it take to realize money spent? I just drive a bit slower and use my cruise whenever I get the chance. I'm around 18 mpg right now, but I drive like an old lady these days.

 

[aaron72]

Exactly as LVYUKYUK says. You're not really going to see much of an increase with the CAI and exhaust. You just have to drive a little slower. I'm almost at 20,000 miles and I have an average of 19.4 mpg during that time.

 

[Black Dog]

Should be CA legal, guessing maybe as long as it has the crankcase vent hose fitting. I recently read of a guy claiming 6 mpg gain from a tune, but I find it reeaallly hard to believe. I think you can tune for maybe a 10% increase or about 2 mpg hwy. The CAI is not gonna really give more mpg after the computer adjusts the mixture, as stated above. It should contribute toward responsiveness and a bit of noise, and is a good ingredient for adding a tune and exhaust.

 

[djcronos]

Thanks for all the replies everyone. Now I have a few more questions.

First off, why does the computer adjust the fuel mixture in the first place? What exactly does that mean? Our trucks are configured to get a certain MPG, so the computers in our trucks recalculate accordingly?

I have the 4.8L V8, and I think I drive like a grandma myself. I try not to get the vehicle above 3k RPM if at all possible. I haven't gone over 75mph on the freeway either.

Most of my driving is to and from work, on the 101 (for all you Bay Area folk), and it's stop and go on the way home. I also putt this thing around my neighborhood to the 7-11 or local Safeway. I don't gun it off the line. Now with that said, I've read on other posts that the fuel pumps in our trucks is what might be causing the low mpg, I get about 14.8.

But then again, I haven't even gone through 2 tanks of gas yet - it has under 500 miles on it. Maybe I'm being too impatient and should wait until the truck breaks in more?

 

[Black Dog]

No, that's not how it works. It is not because the PCM is trying to maintain a certain economy. It's like the new CAI allows more air volume to pass metered into the engine, and so the fuel adding in is causing a lean mixture. Lean can create more power but can also cause cylinder component burning. So at the same throttle position as before (one of the measuring parameters, also air mass and plenum pressure, maybe) you can accelerate faster, so you back it off a little to get the same acceleration as before, now using less gas. There is the mpg savings. But now the computer catches up to the change through its own history analysis and determines the mix must be lean, so it begins adding a bit more fuel to the extra air passing through. Now the mix is back to normal, but the new mpg savings are gone, as well as any obvious low end power gain. But you still have better responsiveness maybe, and a few high rpm horsepower. And so this is our theory, anyway.

I'll try to explain the fuel pump thing after I get some sleep, basically with fuel metering and injector flow rate limitations higher pressure does not necessarily mean more consumption, though it could in some cases.

But yes you do need to let it break in, it is still learning to optimize performance.

 

[LVYUKYUK]

Just as Black Dog said DJ, let it break in some. I have an 08 Yukon with about 2,500 miles on it now and my better mpg only came after a long road trip to the Bay Area. (I loath the 101) After I got back home and ran through a couple tanks of gas, I was hitting about 17.8MPG and I'm hoping for a bit more. I'm in Las Vegas and the A/C has been on since I bought my Kon. I'm sure 1-2mpg goes to keeping me chill.

 

[Zed 71]

Yeah, that 101 is brutal and all that stop/go will drive the mileage down quite a bit. Not too much you can do about that, but it will get better once it is broken in.

 

[djcronos]

Thanks for all the reassurance. I'll report back later, in case anyone really cares

 

[JD Larue]

dj, 14.8 mpg isn't all THAT bad for around town and 101 stop & go actually. After it gets broken in and loosened up I don't know that you'll see that much of an improvement over what your getting now. But, on the freeway (not 101) on a long trip you should see considerably better mileage. I drive the 580 regularily (every bit as bad as 101 if not worse) and get around 14 around town. But when I get out on the open freeway it improves drastically. Coming back from Reno last month I got 23-24 mpg. I have a 5.3 with about 10 K on it so yours should get better with time.

 

[kingnut]

i would take 15 mpg average for daily driving with the 5.3 tahoe. i havent bought mine yet but its the car im looking at when i get back stateside.

 

[djcronos]

Thanks JD for the positive outlook. I'm getting 15.2mpg right now, and I'm okay with it. It's not as bad as I thought, actually.

And yes, the 580 is 1,000,000 times worse than the part of 101 I drive