IDI Power?

[Dave Sponaugle]

I don't even want to guess how many times I made that trip back in the 70's and early 80's. Denver, NYC, Denver, NYC, Denver, Boston, Denver, NYC for 13 years. If you recalibrate the speedo to indicate the actual mileage driven, 33's are not really hard on MPG. If you drive faster than 55 MPH they can actually increase the MPG unless they are wide with an aggressive mud tread. Something about 9" wide and 33 or 35 tall helps the gearing a good bit. But they will kill the power if you are heavy.

[460/5]

thanks a lot for the help guys! hopefully ill be visiting this page more often! i was actually thinkin a more aggressive all terrain tread in the 33 to 35 range and adding a turbo. distances traveled and speeds are relayed to me via a garmin nuvi so my fuel and speeds are accurate. its also a great way to avoid tickets. when a copper tells me i was going so fast, i can say, yes i was, or i can show him he clocked someone else. radar detector helps too. lol. goin OVER the rockies, what kinda mileage can i expect, with and without a turbo? unloaded. my dad lives on the west slope, so i make the trip a handful of times a year.

[Dave Sponaugle]

What comes into play here is the turbo makes more power from the engine.

But when you make more power, you also burn more fuel to do it.

That said, when you add more air to the engine, it turns any black smoke into power since there is enough air for complete combustion.
So you are actually making more power with the same amount of fuel.
That will increase the MPG, as long as you drive at the same speeds you can run with a NA motor.

Like right now you can pull a hill with your foot on the floor, black smoke rolling at 45 MPH.
So you add the turbo, drive up the hill at 45 MPH with no smoke, the MPG increases.

While you are driving up the hill, you realize you still have power left in reserve, so the throttle goes down a little harder and you are cruising right up the hill at 55 MPH, still with no smoke.
When you fill up, suddenly you find out the MPG is right back where it was before the turbo.

But....you want more power, so you turn the fuel up a bit more till the black smoke starts to come back again.
So now you are blasting up the hill at 65 or 70 MPH.

When you fill up, the MPG increase is gone and has actually dropped 2 MPG.

Back when my truck was bone stock, 6.9 NA motor I could see 17 or 18 MPG rather often.
Even when I was going home through the mountains on a two lane road with steep grades and lots of turns.

Today, 2" body lift, 33" tires, west coast mirrors, wide dump bed, stacks and a motor with lowered compression, high boost turbo, hot injectors and IP.

The trip home time dropped from 3.5 hours to 2 hours since the mountains are like driving flat ground in the old days.
But the MPG average I see now, 11 or 12 most of the time unless I am towing or hauling a lot.

I am going to say that 1.5 to 2 MPG of that drop is from the new ULSD since I was burning the old high sulphur fuel way back then.
But that still leaves 4 MPG or so because I am making a lot more power and can drive much faster even though I have increased the frontal area and weight of my truck considerably.

Moral of this long rambling post.
Yes a turbo can increase the MPG average of your truck.
But most people wind up seeing a MPG drop when they add a turbo, because they drive faster or haul more.

[460/5]

i drive pretty much the same all the time. 70 mph. been pulled over too many times to be hotroddin everywhere i go... lol. basically, what im hearing, is that when i add a turbo, i can expect to see mileage go up from around 15 to somewhere between 17 and 20. right?

[Dave Sponaugle]

Unless you start leaving the stop signs faster.

When someone asks about fuel mileage my standard answer is, your driving style has more of an effect on MPG than equipment does.

Wind the engine out to the redline in every gear with your foot on the floor, low MPG.
Slow even start, shifting gears at 2000 RPM, lots better MPG.

Keep hammering on it till you have to come down hard on the brakes for a stop light, low MPG.
See the light is red, let off the throttle 1/2 mile before the light and coast to it, lots better MPG.
See the light is red, let off and start coasting 3/4 miles before the light, even better MPG because the light will probably be green before you get there, so you will already be moving instead of having to start 3.5 tons from a dead stop.

Saying a turbo will increase the MPG from 15 to 17, I am not going to say that.
It could, then again it may drop it to 13.

[460/5]

i picking up what youre layin down. i think youd be pretty surprised at how this 18 year-old drives. lol. not sayin i dont get on it every now and again, but im not balls to the wall 24/7 either. guy im lookin at gettin the truck from said that the truck will cruise all day long at 70 or 75 happy as a clam. im guessing it has 3.55s.

[Sycostang67]

I have 4:10's with 33" tires and I usually avoid the freeway. I get 16-17 city driving, but it drops to 14 if I spend too much time over 60mph.

[ghunt]

I seem to get 12-13 mpg no matter what I do. Drive back in forth in town on a tank, get 12 mpg. Take a 2-hour trip on the highway, staying at 65 or under, get 13 mpg. I dunno.

The fact that I'm running mud tires probably isn't helping things, although the mileage hasn't changed much from the old block-tread AT's I used to have, and I have 4.10's.

[Sycostang67]

My truck had the stock skinnies when I got, and my mileage was unaffected after I put on the 17x9's with the 33's. Thats been one of the perks of this truck. After all the weight and parts I have added, my MPG hasn't changed from when it was stock. Even running the A/C doesn't change it. I did the same mods to my 85 460 and went from 15mpg to 10.