s10/sonoma - the quest for mpg

project: 1991 sonoma 4.3/auto/3.42 rear. short bed regular cab, 3,000# soaking wet with a heavy rubber bed mat.

this is to be my $2013 vehicle unless something else comes along. i also plan to park the suburban for the summer and drive this truck including for work and pulling a small trailer so i can not lose cargo capacity.

i am open to:

underbody pans cap anything else you can think of to increase mpg.

i am opposed to:

smaller mirrors(reduced view backing a trailer sucks) tonneau cover or lid, need to carry stuff. things that would make it overheat interesting cheap engine swaps that do not lose any hp or torque over my 4.3

right now the truck has 182k miles and the fuel pump is bad, so first order is a new pump. the trans is also weak when it is cold outside. i have a rebuilt one to go in if i so choose.

the 4.3 still runs great and has plenty of balls, so i do not plan to change it just yet. however i am willing to hear engine swaps that keep the truck as fast/faster but net a jump in mpg. turbo 4? turbo 5? i am also not opposed to a rear end gear swap.

the plan thus far:

2" front drop and 3" rear drop. i am doing the big zq8 sway bars not for any mpg gain but for handling.

i have 14x6 and 15x6 wheels so i can run narrower 205mm tires when i do not want to run wide 17's for play. maybe some disc wheel covers on the 14" wheels?

i'm open to any and all suggestions but i am CHEAP and right now a bit on the poor side. there is about $1600 left in the budget before i hit $2013 because the truck was just that cheap. figuring $300 more off the budget for new sheet metal for a new door, fenders, hood. they're crap and need replaced.

Biggest bang for the buck would be a streamlined bed cover but that's on your no list.

Maybe a chin spoiler then.

http://ecomodder.com/ has some good ideas. You could do stuff like: sloped bed topper (on your no list but helps a bunch), 5 or 6 speed manual trans or good rebuild on A/T, taller rear gears to reduce rpm, only if sticking with 4.3, front air dam, lose as much weight as possible (off truck), low resistance tires or run higher tire pressure.

forgot to mention i have a bravada front bumper cover with built in air dam.

there is no commute route, i go somewhere different every day. i usually baby the loud pedal in the truck, as it gets loud and attracts unwanted attention with it pushed to the floor. a 4.3 with flowmasters is not exactly the best sound, but the mufflers were free and allowed me to scrap the cat to recoup $130 in budget right after i passed emissions.

mythbusters did a mpg challenge with a pickup, found one of those nets in place of the tailgate produced the best MPG results without going the "custom ecomodder" route

Also, try making something like a Lund Cold Front grill cover for your truck. I ran one year round on a Chevy G20 van and there were never any cooling issues. I really dont know if it helped MPG though.

its kind of hard to see but its basically plastic panels that clip into the grill, they have a bunch of small holes in them so the truck can still breathe.

maybe toss the body, find a leaky old boat and turn upside down and mount on chassis. Cut a little plexiglass bubble for the driver.

flat wheel covers.

Do the simple stuff first to make sure you're getting the most MPG out of the stock parts. I'm talking plugs, wires, rotor/cap (if it has those), oil & filter change, air filter, fuel filter, and fluid changes in the trans and diff.

Personally, I would run a good synthetic in the rear diff, swap in your rebuilt trans ASAP (a slipping trans will kill your mileage), and do all of the above.

Then the drop with the 205/15's as well. I'd really look into the tailgate net and the front chin spoiler. Seal up all of the un-needed gaps in the nose (the Bravada nose is great idea, especially since it sounds like you need bodywork anyway).

Then make sure all frictional losses are minimized. Wheel bearings, brake pads/shoes, and parking brakes can all cause an issue here. Don't forget about the motor, so electric fans, better exhaust, etc.

Only then would I look into stuff like home-making a front underbody tray and some side skirts (wood is fine).

Instead of a net tailgate, why not drive with the tailgate down when there's no cargo in there? Cheaper, less stupid looking, and probably even less resistance than the net.

that was also part of the mythbusters test. the stupid net beat tailgate down, and no tailgate at all in MPG, as far as I remember. might need to check youtubes on that one. Also beat tonneau cover.

Look to the S10 electric for aero ideas. They had some simple stuff that made sizeable efficiency gains and it was still just like a regular truck. Aero front nose, tonneau cover, a seal to bridge the gap between the cab and bed, and lower rolling resistance tires with high pressure. Go for the simple stuff first, which also includes making sure the drivetrain is all in good working order.

Bryce

failboat wrote: that was also part of the mythbusters test. the stupid net beat tailgate down, and no tailgate at all in MPG, as far as I remember. might need to check youtubes on that one. Also beat tonneau cover.

how much we talkin'? this is intriguing to me.

and btw, my vote is for a manual transmission swap.

Aside from the basic mechanical stuff, aero will likely buy you the biggest gains for the least money; these obviously increase the more highway driving you do.

Big airdam - go as low as you practically can. If it's not a full wrap-around, put aero tabs in front of the wheels as well. Seal up every unnecessary gap in the nose with closed-cell foam; even the tiny gaps around grills, headlights, license plates, etc. can add up. Flat undertray running the full length of the body; you may need a small gap at the back of the engine compartment to allow hot air to escape, but otherwise cover everything you can.

All this is time-consuming, but if you're creative with materials it can be pretty cheap.

Warm air intake instead of cold air.

iceracer wrote: Warm air intake instead of cold air.

Yeah, I should have mentioned that as well. Also partial radiator block to achieve faster warm-up (this requires some experimentation, obviously).

What sort of mileage are you getting now? I know it's not vert comparable to your year but I have a 2000 chevy s-10 4.3 V6 with a stepside bed and I've gotten up to 28mpg just by adjusting the nut behind the wheel. I used a scangauge II for tuning the nut. The lowering kit will help, as will a chin on the front. You may want to look at adding vent holes in the rear bumper or a full undercarriage aero plate. I know my bumper acts as a giant scoop for any air flowing under my truck. I also had a fabric tonneau cover that could be rolled up and the bars stored behind my seat in 5 minutes, I am certain that even a fabric cover helped my mileage. I don't trust the mythbusters anymore, or as a modified mythbusters quote: I reject your mythbusters and substitute my own engineering intuition. Inflating the tires up to the sidewall max will help as will wheel covers over the back wheels and add a grillblock. If you want it to be a challenge vehicle I would suggest swapping in a v8 with a manual transmission and tall gearing so that you would have the power when you need it and the torque to cruise down the highway at 1600rpm, A well tuned v8 in the same vehicle with proper gearing will be only marginally worse than the V6. Good luck on your hypermiling adventures!

Screw Paragraphs.

I have some extra drop spindles and front lowering springs, rear lowering blocks, that were extras from what came with our Lemons S10. I'd sell them to a GRMer for a very challenge friendly price

Nashco wrote: Look to the S10 electric for aero ideas. They had some simple stuff that made sizeable efficiency gains and it was still just like a regular truck. Aero front nose, tonneau cover, a seal to bridge the gap between the cab and bed, and lower rolling resistance tires with high pressure. Go for the simple stuff first, which also includes making sure the drivetrain is all in good working order. Bryce

seconded. GM did a chunk of the work for you, in a wind tunnel no less. The seal btwn the bed and cab was surprisingly beneficial in the S10E/DoE (IIRC) reports.

The S10E didn't have a full bed cover either, it only cover the rear half or so of the bed. Going to an electric engine fan could help too, but spending $$$ to save $$$ can be tricky.

For engine swaps for power and econ, you could swap in the aluminum 5.3 and auto from a 2wd GMT360 Trailblazer with cylinder deactivation. There was a build thread of a guy installing this pair in his E30 BMW. I bet with the small frontal area of the S10, it would be in 4 cyls most time when moving.

Sonic wrote: I have some extra drop spindles and front lowering springs, rear lowering blocks, that were extras from what came with our Lemons S10. I'd sell them to a GRMer for a very challenge friendly price

awesome. i'm still digging for that boost gauge BTW - sorry i'm taking so long but i don't remember where i put it.

right now get 22mpg all highway, cruise set at 70. this was a basically flat trip that i measured it on. i get 17 around town.

so i've been thinking the last day or two.

my 91 caprice wagon had a 305 TBI v8 and 700r4, 2.73 gear, 215/75/15 tires, and would knock down 26mpg highway in the mountains and 27-28 on flat highway trips.

so - what if i put in a 350 TBI/700r4(both rebuilt), 2.73 gear, same height tires, in something much smaller and weighing 1500# less. would i be too far off in expecting similar highway mpg from the little sonoma? there is no mpg difference between a 305 and 350 90% of the time.

belteshazzar wrote:

failboat wrote: that was also part of the mythbusters test. the stupid net beat tailgate down, and no tailgate at all in MPG, as far as I remember. might need to check youtubes on that one. Also beat tonneau cover.

how much we talkin'? this is intriguing to me.

well here's the video

www.youtube.com/watch?v=r3aqHbD-O9E

slopecarver wrote: You may want to look at adding vent holes in the rear bumper or a full undercarriage aero plate. I know my bumper acts as a giant scoop for any air flowing under my truck.

Or get one of those glassfibre fillers and remove the rear bumper altogether.

As everyone else said.. you need to fill in all the holes.. and trucks have a lot of holes

i'm pulling the bed to install the fuel pump and rear sway bar mounting brackets, i should move it forward and close the gap to the cab.

patgizz wrote: i'm pulling the bed to install the fuel pump and rear sway bar mounting brackets, i should move it forward and close the gap to the cab.

Careful doing that - it will squeak and squack like mad