20 mpg hijack thread

[bojak]

i did not want to hijak a thread so i am starting this one. I have 89 v3500 with 5.7 tbi and 4:11 gears,d60 up front. It is running 285/75/r16. i plan on lifting it 2.5". This is a runaround truck not a heavy hauler.

What i was wanting is some recomendations on building / modifying my drive train for optimal fuel economy. I am not shooting for 20mpg, just a better mpg for moderate changes. From what i understand a LS motor is the ticket but i was looking more for improveing what i got. Stay TBI, convert to carb? Cahnge gearing? what size? What exhaust intake setup? Any ideas are appreciated.

[Ziegelsteinfaust]

What are you getting now?

I am not a 4x4 person, but my guess would be a well built 454 Vortec would be the best swap candidate here. Your truck is big, heavy running gear, tall tires, and that just needs torque. To the swap I would add electric fans, headers, cat back exhaust 3" if you have to smog it, if not 2.5" duals, and a good tune. The 411 pcm from the express van is more tunable, and should fit the 454 vortec.

Your gears should be fine you'll be at 2000 rpm at 70mph. So I would leave those alone, and see how you like the swap first. Plus it would give you broader performance from your truck, and that maybe just as important to you.

If you want a LS get a 6.0 with the 6 speed out of a 2500, and that would be its best bet. Do the above bolt ons, but the downfall with this is the price.

A Vortec 454 can be had in my area for $1500 complete with a 4L80, and a 6.0 with a 6 speed complete about 6-7K. The prices are from wreckers who sell running motors with decent stated mileage.

Either way you could end up right about 15mpg hwy maybe a bit more if your lucky, and drive correctly. Just the 6.0 would be faster through the gears because of the 6 speed auto, but it would likely add another 1500 to the price for a gear swap.

So for me I would go 454 Vortec the price is right, and it can still offer you a good all around truck.

[bojak]

Thanks, and that was supriseing.i would have never have thought the cure for mpg would be a big block. My mechanical knowledge is limitted so i have no working knowledge to refrence. That is why i am soliciting opinions, so thanks for your thoughts.

[68Timber]

Someone pass the popcorn?

[bammax]

Plenty of low end torque to move the weight from a stop (hence big block)

High (numerically low) gear ratio like 3.42 or even higher if the engine is strong enough to pull on its own merit. Fullsize cars got 2.78 or 2.93 gears along with a 2004r or 700r4 trans mated to a smallblock and would pull 20 mpg at around 3,500 pounds. Bigger vehicles needs more power or more gearing so pick one and run with it.

Overdrive trans. Either a 2004r or 700r4 mated to a small block, or a 4l80 mated to a bigblock. Or you could run a gear vendors unit behind a th350 or th400. A gear vendors mounted to a 4l80 would give you the ultimate in gearing to maximize your mileage.

Narrow tires with high pressure also reduce rolling resistance which can help a bunch with mpg. You sacrifice traction though so it's not a trade that many people make.

For a 4x4 that sees highway use you want plenty of torque and to keep the gearing at 3.42 or 3.73. Swap in an overdrive trans or a gear vendors unit. Run regular street tires and avoid the big mud or rock crawling tires no matter how cool they look. Make sure the truck isn't carrying any excess weight and that everything is working properly (no dragging brakes or misadjusted carb)

For a 4x4 that sees lots of off road or trailering duty get the gearing more extreme such as 4.11 and find a way to reduce weight where you don't need it. Also think about having a second set of tires for when you venture off road or are heavily loaded. That lets you run more mpg friendly tires when you're putting around town, but doesn't limit your fun when you actually do want to go out in the country.

[Jabes1]

TBI isnt a bad idea, far better than a carb with more driveability and is certainly more tuneable and efficient. It might be possible, but those 4.11's are going to kill your mileagle. One way to find idea's to help improve your mileage with what you already have is to google hypermiling. It will give you ideas as far as how to improve your driving technique and principles to apply to your vehicle... it works. Also try to find a copy of the 12/20 article I mention later for ideas.

HOT ROD did an article about 12/20 back in March of 2001. 12/20 is twelve seconds down the strip and 20mpg. It intrigued me then. I was running a Wiend 144 at the time with a Carter 625cfm carb, and I think on a good day I was getting 8mpg. Fast forward... and today this is my goal for the truck. Attainable? Not sure, but Im going to sure as heck try.

This go around with my truck, Im running a multi point Tuned Port Injection setup managed by a Holley Commander (fully programable) TH400, backed by a gear vendors and a 3.42 geared 12bolt. I dont remember the tire diameter off hand, however the wheels are 20x8 and 20x10 torque thrusts with a 275 45 20 in the rear. My tune isnt finished, still setting things up, so I have no real data to put forth yet.

TPI can be had cheap and so can Vortec stuff. TPI I simply have always liked the way it looked and it gives excellent bottom end torque which is perfect for trying to cruise at a lower RPM, but kinda of bad for performance top end wise. There are some things you can do to help the top end of course, but now days Im not looking to ring out every ounce of power, just enjoy driving my truck. Driveability is important to me, bottom line. Im currently running a CROWER blower cam, which isnt as efficent as one could possibly find for an NA motor but....As far as 12 seconds down the strip that comes later in the form of a front mount intercooler and a large single turbocharger.

This could be a GREAT thread as gas prices arent going down anytime soon.

[Jabes1]

Anyone have kettle corn? Subscribed.

[bojak]

This is the nuts and bolts stuff i was hoping for. I was thinking in lines of regearing, and really letting it breath. It is an antique so no smog certification is required ( how loud are straight pipes? ). I put an open element breather on it already but was wondering about tuneing the tbi. Do throttle body risors really work? Do the aftermarket upgraded TBI units Make a big difference for the exspense. I am running 285/75/r16 rugged trail BFG on it so the taller narrower thing is what i am doing and they are a street tire in offroad sidewalls IMOP. I keep them pumped up pretty hard. It may tow a light trailer at times, offroading will probably be driveing across a feild to a dead deer. So it is a cruiser really. Not kidding myself with a 1 ton brick hopeing to get 20mpg but would love a legit 15-17 mpg for as cost effective as possible. Thanks for the recommendations so far. Keep them coming.

[Firebirdjones]

Lifting it won't help mileage, and the larger 285 series tires you are running take more power to turn, so that's not helping either. Although the 33" tires you have do help kill some of that 4.11 gear so it's a trade off.

Lots of little things you can do to maximize what you already have before resorting to extreme things.

The lighter you can make the wheel and tire package the better, that's unsprung weight as well as rotational mass. For every pound of rotational mass you remove, it's like removing 6 lbs. of dead weight out of the truck and the engine doesn't have to work as hard.

You can accomplish the same thing with aluminum driveshafts.

Look at installing electric fan setup, this again is unsprung weight, and will free up 10-15 hp over a clutch driven mechanical fan, and is generally worth up to 1 mpg as a result.

Free up the exhaust and intake side of the engine.

I find most MPG gains in the tuning to optimize the engine package since factory tunes are lame at best. However with TBI you are limited since tuning software is primitive and most shops don't have the knowhow or the software anymore. So you are sort of stuck there.

Alot of nit picky things you can do that people don't consider, and then wonder why their 4x4 trucks get 8 mpg.

With just simple tuning, better exhaust and intake setup, I'm getting 14 mpg out of my 502/400 turbo 1 ton pickup with 3.73 gears and stock size 9.5x16.5 tires (which are about 30" tall). I could pickup another 1-3 mpg with some of the other tricks I mentioned above but don't want to mess with the truck any further.

I made a max effort MPG attempt on my 4x4 72 blazer, with a 6.0 LS swap, 4L60E, 33" tires, 3.73's. etc....and knock down 22 mpg highway and 17 city.

It can be done but the further you try to go the more expensive it gets. For some it's not worth the trade off. Others will say to just go duramax, (which I'm doing)

[Jabes1]

The TBI throttle body spacers work by increasing plenum volume, yes they work. I wouldnt spend the money on the upgraded holley throttle bodies, too much investment and too little return, unless you can find it used and working. As far as handheld tuners go, I wouldnt invest in a brand new one. You can find them used on craigslist and eBay along with the TBI spacers. You might be able to google tuning/flash software for your TBI equipped truck and the appropriate cable needed to make adjustments. Lots of forums and reading... so be warned.

Straight pipes are loud... Ive had Flowmasters, Magnaflows and inexpensive Summit racing glasspacks. By far, I love the Summit glasspacks with an x pipe and turndowns which are suprisingly quiet while cruising. You can turn the glass packs away from the directional flow for a little more sound deadening. The longer the glass pack the more quiet it is and you can run more than one per pipe to tune sound. The bigger the case on a muffler generally the quieter it is.

FirebirdJones is correct, solid advice there. Electric fans are an easy install along with solid thermostatic controller. Im not sure the length of your driveline, but a nice lightweight driveline definately helps. You can measure eye to eye on your current driveshaft and see if a retired NASCAR driveshaft is availiable on eBay. I picked one up for super cheap, its a lot lighter than my stock shaft and has 1350 joints balanced to perfection. You can use conversion joints if you dont have 1350s, but generally they can be a weak link.

[KQQL IT]

Not to mention 14 bolt 3:42's are $$$
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[andrewmp6]

Some little stuff will add up like keeping the tires fully inflated and a tune up when needed.Don't carry extra weight you don't really need to have in it.

[bammax]

If you decide to switch out wheels/tires at some point don't fall for the marketing on lightweight. Many aluminum wheels weigh a lot more than steel wheels do in an effort to increase their strength. Just as an example for a 2wd junkyard hunter, a steel wheel from a mid 90's caprice weighs less than half what the aluminum wheel from the Impala SS weighs. Generally a well built steel wheel will be strong and lighter, but not as pretty as the aluminum wheel, which is counter intuitive since aluminum is used everywhere else to save weight.

For max fuel economy and no offroading I'd be looking at running a 235/85/r16 on the factory style steel rims

[Firebirdjones]

You have to check the weights of the wheels AND the tires when you shop around because they vary all over the place. Most companies will list it for you.

I weigh all my stuff just because I'm a bit finatical that way.

The factory 16.5 steel wheels on my 1 ton, along with a stock size 9.5x16.5 Firestone 10 ply tire that I run, weigh 70 lbs. a piece!!! That's an extremely heavy wheel/tire combo. These factory steel wheels are so thick that your standard wheel weights won't simply tap onto the lip of the wheel. These are stout wheels for a steel rim.

I could put just about any aluminum wheel on this truck and probably save 10 lbs per wheel,,,,that's a huge savings in unsprung weight Not just for gas mileage and accelerations purposes, but lighter wheels also help braking as well. Just something to think about....

I had even contemplated going with the factory GM forged aluminum wheels found on the 3/4 tons circa 2001-2005's to save some weight and at the same time I'd have a 16" wheel with more tire choices (gets rid of 2 problems at once). But I just can't get over the look of the modern wheels on an older truck.

[bojak]

Originally Posted by bammax

If you decide to switch out wheels/tires at some point don't fall for the marketing on lightweight. Many aluminum wheels weigh a lot more than steel wheels do in an effort to increase their strength. Just as an example for a 2wd junkyard hunter, a steel wheel from a mid 90's caprice weighs less than half what the aluminum wheel from the Impala SS weighs. Generally a well built steel wheel will be strong and lighter, but not as pretty as the aluminum wheel, which is counter intuitive since aluminum is used everywhere else to save weight.

For max fuel economy and no offroading I'd be looking at running a 235/85/r16 on the factory style steel rims

That's good news. I have a set of newer steel take offs i was planning on running. When i got them and was moving them around i was suprised at how much they didn't weigh. I am running solid steel wheels now but the new ones are more of the standad that you see now with crescents cut out of them. I am probably going to go with a throttlle body spacer, electric fan / thermostat, headers, and st 2.5 exhaust to some mufflers. Get all that done, and if some money falls into my lap get alight weight drive shaft and or an aftermarket TBI. Oh yeah, fill the tires with helium too.

What are yalls opinions on deleting the catalytic converters? I am not required in my state to do emisions on that size or that old of a vehicle.

[school boy]

cut them out and scrape them. every vehicle I have but one has had them removed by me or the person before me. Its not that I intentionally remove them on purchasing a car/truck, just when im doing exhaust work I tend to remove them in place of new piping. Ky also has no emission testing.
I also agree with the tpi manifold mentioned earlier. Great low rpm torque for any sbc

[bammax]

I assume you're joking about the helium in the tires. Some folks run nitrogen in the tires but it's never been proven that it has any advantage over regular air. The idea is the molecules are a different density so it helps to maintain a more constant pressure and in turn a more consistent heat pattern. Helium would just escape right through the rubber even if you could find someone to put it in the tire. Rubber is porous so anything made up of super small molecules will pass through it. I may be oversimplifying this thing though, so ask someone who spent the night at a holiday in

[INSIDIOUS '86]

My old mans 94 dually passed emmisions with no catalytic converter but the engine is in tip top shape though as well
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[bojak]

Originally Posted by bammax

I assume you're joking about the helium in the tires. Some folks run nitrogen in the tires but it's never been proven that it has any advantage over regular air. The idea is the molecules are a different density so it helps to maintain a more constant pressure and in turn a more consistent heat pattern. Helium would just escape right through the rubber even if you could find someone to put it in the tire. Rubber is porous so anything made up of super small molecules will pass through it. I may be oversimplifying this thing though, so ask someone who spent the night at a holiday in

Yes joking about helium. I have heard of the nitrogen but had also heard it was BS too.

[andrewmp6]

In a fleet used car or truck Nitrogen does work but in a normal car and truck it will never see the miles to make it worth using.Nitrogen does not expand and contract as much as compressed air does is why its used.

[Zoomad75]

I'm not sure you got the right truck to "run around" in if you want 20mpg's. Even 3/4 tons built in the last 10 years with 6.0 Gas LS engines struggle to get 15-16 mpg with a 4l80e trans. A shove downhill with a heavy tailwind might get you close, but not practical. Save the money on a futile effort to get 20 mpg out of a tank, buy a manual trans s10 to run around in. I'm getting 24-25 mpg with my 97 s10 4.3 5sp 2wd. My tank stays in the driveway except to go play.

[Firebirdjones]

Originally Posted by Zoomad75

I'm not sure you got the right truck to "run around" in if you want 20mpg's. Even 3/4 tons built in the last 10 years with 6.0 Gas LS engines struggle to get 15-16 mpg with a 4l80e trans. A shove downhill with a heavy tailwind might get you close, but not practical. Save the money on a futile effort to get 20 mpg out of a tank, buy a manual trans s10 to run around in. I'm getting 24-25 mpg with my 97 s10 4.3 5sp 2wd. My tank stays in the driveway except to go play.

It can be done with the right combination of parts and a sharp tune.

I get 22 mpg with my 6.0 in a 4x4.

[jitteryguy]

folk's should really think about read'n a post before reply'n .

[Jabes1]

Bojak.... any progress?

[bojak]

Put on lighter steel wheels. Open air element filter. That's it so far. The thread has giving me a plan for how I am going to appropriate my money though. Next up is header exhaust. Then tackling the TBI. Electric fans after that. Upgrade the ignition and a really good tune up from there. I will probably re-gear the truck after that and I am reconsidering weather or not to do the 2.5 inch lift. It sits ok now and wouldn't want to make it less drive around friendly. The lift and the gearing are a connected decision so those will be the last things on the plan. Only had it for 4 months so some funds are going to getting it cleaned up from 25 yrs of use. Interior had gotten pretty rough. I will document the changes with fuel reports to see what each change equals.