Getting Better Fuel Mileage (Trucks)

Tech questions that don't fit above forums

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Re: Getting Better Fuel Mileage (Trucks)

Post by Matt Gruber » Fri Oct 19, 2012 7:23 am

Warpspeed wrote:This really applies to any vehicle, not just trucks.
I just reduced tire weight by 44#(11 each) on my 72 vette.
Could be ~1/4 sec quicker accelerating, and should get better mpg. max 44 psi vs 35 old. Ive got 40 in them.
Car does feel lighter! Smooth ride, amazing for 40 psi.
A little taller too. speedo off by 10% 40 is 44(radar sign)
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tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
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Re: Getting Better Fuel Mileage (Trucks)

Post by jim_ss409 » Sun Oct 21, 2012 2:01 am

You may have noticed that many large trucks are running wide single tires to replace dual wheels. When you factor in the lighter weight of the rims they reduce the weight per axle by about 190 lbs.

Image

Of course everybody on this forum knows that lighter wheels and tires has to translate to better acceleration, braking and fuel economy but the main advantage for these wide tires is reduced rolling resistance. They say it's because you have half as many sidewalls to flex.
The fuel savings are well documented at about 6 to 9 percent depending upon the load and type of haul.
I've been running them on my long haul highway trucks for about five years and I'm very happy with them.

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Re: Getting Better Fuel Mileage (Trucks)

Post by Dodge Freak » Tue Dec 25, 2012 8:20 pm

Keith Morganstein wrote:
#6 IDLE TIME : THE BIGGEST WASTE OF FUEL OF ALL. Any time that engine is running and the truck isn't moving hurts tank mileage and your wallet.)

For ages we were told not to shut off the engine at stoplights but now what do the latests cars do, they automatically shut off the engine and it re starts by stepping on the gsas :lol:

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Re: Getting Better Fuel Mileage (Trucks)

Post by PackardV8 » Tue Dec 25, 2012 9:06 pm

For ages we were told not to shut off the engine at stoplights but now what do the latests cars do, they automatically shut off the engine and it re starts by stepping on the gsas
That was then. This is now. Back in the bad old days of distributors and carburetors we couldn't run more than 9.5:1 without pinging and less if it were supercharged. Today's better designs are running 11-12:1 and up, some of them boosted.

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Re: Getting Better Fuel Mileage (Trucks)

Post by roadrunner » Thu Dec 27, 2012 4:31 pm

Is it really worth shutting the engine off at the traffic lights in the long run? Not only does this practice wear out the starter motor faster, if one is running a turbocharged engine then there is the chance of oil coking in the turbo's bearings, although these days more turbo's are water cooled so maybe it's not such an issue!
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Re: Getting Better Fuel Mileage (Trucks)

Post by MrWOT » Thu Dec 27, 2012 6:17 pm

roadrunner wrote:Is it really worth shutting the engine off at the traffic lights in the long run? Not only does this practice wear out the starter motor faster, if one is running a turbocharged engine then there is the chance of oil coking in the turbo's bearings, although these days more turbo's are water cooled so maybe it's not such an issue!
Unless you beat the tar out of the engine then immediately shut if off it probably won't coke, oil is better than that nowadays. How hard do you drive light to light? (well... sometimes.... ;) )

That being said, I don't recall which, but one of the turbo OEMs I deal with recommended a 2 minute+ cooldown after testing.

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Re: Getting Better Fuel Mileage (Trucks)

Post by user-3597028 » Fri Dec 28, 2012 4:06 am

Regarding tire pressure;
my race car hauler, A 1988 GMC crew cab Duallie, 2wd, 454 auto with 3.73 gears and no OD. 28 foot united express line trailer, 9000# GVW.total weight of truck/camper and trailer loaded, 19,000#.

Truck has a TBI motor, Edelbrock intake, no water heated base, has a vortex atomizer, Edelbrock stainless headers, 3" single exhaust, no cat, no air pump. 110,000 miles. Truck has had a pampered life. Never seen a snow flake. Turbo 400. Took me 5 years to find it. I race a nostalgia car, needed (wanted) an old body style truck. Same body style as a 1973-up.


Back to the nuts and bolts of what I found setting this thing up.
___________________________________________________________

1)Tires call for 65 on both truck and trailer. Gets less than 5 mpg this way, more like mid 4s. Worse at 55mph than 66 mph with any pressure. Tires run over 125 degrees. Engine runs a 220. It's gutless too. no timing, tons of fuel with that eng. temp. We read the prom, can't seem to change it though.

2) Remove all antifreeze and run 2 bottles of Redline Water Wetter, it goes up to 6.5mpg, 190 degrees, lots of power. Still has a lot of rolling resistance.

3) I put the trailer tires at 75#and the truck at 90# rear and 80# front...gets 7.5- 8+ mpg. Tires run less that 115 degrees on the hottest day. lots of power and it rolls down the road with little effort. Still gets better mileage at 66 than 55. Those speed restricted highways in Illinois kill my mileage. It hates 55, it lugs the motor too much and sucks gas.

I have two tanks and I check mileage and tire temp at every stop, every time. This info is solid and has been verified over a 40,000 mile span of hauling my race car with this set up. May finally need front tires this year, have some feathering. Rears are 70%. Been on there for 14 years. Tires Always covered outside when sitting, stored in climate controlled building.



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Re: Getting Better Fuel Mileage (Trucks)

Post by Matt Gruber » Fri Dec 28, 2012 5:57 am

several times i shut the engine OFF 1/2 mile from home at 45mph and coasted all the way into my garage. if they shut a new car off at a light, i can do it a lot sooner than that.
61 vette MB MS
maybe some day i'll do a mpg test like that, accelerate to 45, shut off, coast down to 20? turn on, let clutch out in 4th, (over and over). what will it get?
.
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tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

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Re: Getting Better Fuel Mileage (Trucks)

Post by PackardV8 » Fri Dec 28, 2012 12:26 pm

Way back in the bad old days of early Bosch EFI, I did a similar test. Shut the engine off on every long downgrade, at traffic lights and coasting into parking spots. Huge PITA, but increased fuel mileage by about 5%.

The best improvement is to string together all the errands on one day. On newer trucks with the computer MPG readout, I've watched closely and cold starts are the killer for MPG. Once the engine is warm, MPG will stay at the overall average. Several short trips with cold starts will drag down the average 20% below one same length run with multiple stops.

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Re: Getting Better Fuel Mileage (Trucks)

Post by Matt Gruber » Fri Dec 28, 2012 5:43 pm

Jack
5% would be a disappointment. :(
i've devised a proof of concept crude experiment since i'm curious.
my holley bowl holds about 3 ounces.
20-45 mph twice a mile, if using 3 ounces each time is ~21mpg.
So my test next ride is to turn off the elec fuel pump at 20 in 4th and see if it can climb up to 45 and how long 'til it dies. I don't drive my 61 much so it won't be warmed up, but i'll go 1 mile first so it won't be real cold either.
my mpg tests are just a hobby like some people play scrabble.
thanks for your reply.
Happy New Year!
.
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tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

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Re: Getting Better Fuel Mileage (Trucks)

Post by PackardV8 » Fri Dec 28, 2012 8:13 pm

What you are describing is the classic "hyper-mileage" technique. Full open throttle at low RPM, shut off, coast, repeat. It will drive you and anyone else on the road crazy in short order.

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Re: Getting Better Fuel Mileage (Trucks)

Post by Matt Gruber » Sat Dec 29, 2012 2:01 pm

1st try, after 1 mile, coolant temp 105F,
20- up to 48 started to miss, FP back on. looks very good as cold really sucks gas as you say.
Not that hyper technique, just normal light throttle as when warming it up. Maybe 15" vacuum.
Will try again someday warmed up.
Knowledge: Better to have a gun and not need it, than need a gun and not have it.
If i ever find 1 too many closed gas stations, i want to know how far i can go in an emergency. I would just wave cars around me in that case, mostly 4 lane roads so no excuse for others not changing lanes. Way better than calling for road service! Never happened before, BUT 3 of 5 beachside gas stations have closed.
.
.
tame a lumpy cam for the street, more street torque! see my article, archived in the waybackmachine.
https://web.archive.org/web/20130707064 ... TGRU/carb/
Great manners equals more fun.

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Re: Getting Better Fuel Mileage (Trucks)

Post by af2 » Sat Dec 29, 2012 9:08 pm

PackardV8 wrote:What you are describing is the classic "hyper-mileage" technique. Full open throttle at low RPM, shut off, coast, repeat. It will drive you and anyone else on the road crazy in short order.

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Jack, Happy New Year!!! :lol: :lol: :lol:
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Re: Getting Better Fuel Mileage (Trucks)

Post by MadBill » Wed Jan 02, 2013 9:46 pm

Matt Gruber wrote:1st try, after 1 mile, coolant temp 105F,
20- up to 48 started to miss, FP back on. looks very good as cold really sucks gas as you say.
Not that hyper technique, just normal light throttle as when warming it up. Maybe 15" vacuum.
Will try again someday warmed up.
Knowledge: Better to have a gun and not need it, than need a gun and not have it.
If i ever find 1 too many closed gas stations, i want to know how far i can go in an emergency. I would just wave cars around me in that case, mostly 4 lane roads so no excuse for others not changing lanes. Way better than calling for road service! Never happened before, BUT 3 of 5 beachside gas stations have closed.
An engine has far better efficiency at WOT than at light throttle, which is why the full 'hyper' technique works so well. You can practically triple the economy. (if someone doesn't pull you out from behind the wheel first and beat the whee out of you for getting in his way.. #-o )

BTW, not surprisingly, it has the same effect on heat rejection. You can drive a car with no coolant with this tecnique in an emergency.
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Re: Getting Better Fuel Mileage (Trucks)

Post by PackardV8 » Wed Jan 02, 2013 10:21 pm

An engine has far better efficiency at WOT than at light throttle,
How about, "An engine has far better efficiency accelerating at WOT at low RPMs than at light throttle."
This requires a manual transmission so the driver can full throttle, then short shift. When he reaches 40-50 MPH, he shifts to neutral, cuts ignition and coasts down to 20 MPH.

Can't agree with, "You can practically triple the economy." That would be quite optimistic.

Agree completely with, "if someone doesn't pull you out from behind the wheel first and beat the whee out of you." There are already reports of road rage incidents against drivers of Prius and other electric hybrids who are slowing on rush hour upgrades, dawdling along in the high occupancy lane, waiting until it's completely clear to slowly make left turns, all in the name of hypermiling.
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