tires and lift require more boost?

junglejoe · Nov 23, 2016

I figure this would be a good question for people who are lifted and bigger tires... What is you boost at just maintaining cruise speed on the highway..70-75?

I just did 35s again but bigger lift.. My boost is between 12-15psi. now. I also did all 4 rotors and breaks so I might have a sticking caliper and I will check on that..

BK39 · Nov 23, 2016

larger lift, larger tires = more resistance. requires more power to maintain speed.

On a side note, you have a 9" lift and 35s?

junglejoe · Nov 23, 2016

Yeah.. I bought the 35's first when I had a 4.5 lift. I had no plans to lift it this high but I got the 8 inch lift kind of by accident so I had it installed instead of waiting for it to ship back and the other shipped in.. The 9 inch up front resulted front 8 inch springs and a 1 inch spacer and of course the 4 link.. I may switch to 37's.. But not any time soon! Sum beeches cost to much damn money.. LOL

6.0 Tech · Nov 23, 2016

What was it before? With the same size tires, but going up in lift, it should not go up too significantly. I would expect maybe 2-3 psi at most. Your rolling resistance will be the same with the same size tires, as long as the gears are the same, but the added air resistance will make it go up slightly.

PowerStrokePops · Nov 24, 2016

I'm running 37's with 8" lift and on flat ground I am only making (IIRC) 4-6 lbs boost at that speed.

junglejoe · Nov 25, 2016

Before the lift I was at probably 6-8 cruising flat ground at 70mph. Sometimes 10psi on a small incline.
NOW it's pretty much 13-15 pi. Not 15 all the time but pretty steady. I wish I would have thought about this before .I would have never lifted the truck. I am fixing to do studs and gaskets. And turbo and injectors so maybe that will help calm things back down. I went from 17-18mpg down to 11mpg with just the lift!

Rubenk · Nov 25, 2016

I cant see just a lift taking 6-7 mpg from you, given same size tires.

Is anything binding in the drivetrain maybe?

bigrpowr · Nov 25, 2016

something else going on here.

co04cobra · Nov 25, 2016

Yea, just lift shouldn't change your boost or fuel mpg that much with same size tires.

Double check the brakes and calipers, also need to check your driveline angles as that would have changed with the lift.

6.0 Tech · Nov 25, 2016

When checking the brakes make sure there isnt a hose twisted. Seen this happen quite a few times. It holds residual pressure on the caliper and really screws with stuff.

junglejoe · Dec 5, 2016

I checked the brakes.. Nothing seems to be holding binding up.. At the time before the lift I had 33's on the truck. The 35's wore out so I put the 33's on. When I done the lift.. I did 35's again..
I did notice I have boost leaks everywhere.. Cracked rubber boots and the plastic pipe that goes to the intake elbow is busted.. That might have something to do with it?