Topic: Underdrive pulleys

[sirdeuce]

Anybody have any experience with underdrive pulleys? I'd like to take some burden off the engine for highway travel, which is about 98% of this trucks miles. Trying to save some gas here, not looking to make the truck faster.

[emsvitil]

Not going to matter much at normal driving rpm's...………...

[Gnarly4X]

Anybody have any experience with underdrive pulleys? I'd like to take some burden off the engine for highway travel, which is about 98% of this trucks miles. Trying to save some gas here, not looking to make the truck faster.

Hey deucie,

I’ve done this “Can I get better MPG?” a dozen times over the past umpteen years….

I’ll use my truck as example.  1986 Toyota XtraCab, 5-speed, 22RE, 4.56 ring&pinions.

I drive 75 miles a day 21 days per month average MPH 75
@ $3.00 per gallon
@MPG = 20 I burn 3.75 gallons  = $11.25 per day

underdrive pulley = $92.45 (made that number up)
smaller pulley reduces parasitic drag - produces gain of 3 MPG
@ $3.00/gal - @MPG=23- burn 3.26 gal/day = $9.78 – savings per month $30.82
I’m down $92.45 so it will take me 3 months to break even.
So month 4 I start saving $30.82 per month

BUT…
Same scenario … BUT I drive 65 MPH – 3 times LESS drag – 5 MPG gain
Instant 1st month savings per month on fuel = $47.25!

Trade off:  Using the formula Distance equals Rate times Time..

75 miles @ 75 MPH – 1 hour drive time
75 miles @ 65 MPH – 1 hour 9 minutes drive time
Or… about 4.5 minutes longer to get to work and from work to home.

Now… as you know, most MPG gains start with the engine tune.  If I were to just play with engine tune, I’d start with spark plugs, plug wires, and cap & rotor.  Adjusting the TPS on 22RE is critical.  I’d also play with ignition timing.  Jetting on 22R is very critical... ask H8PVMNT.

Then of course it's your driving style and right foot.

Gearing…
The RPMs at cruise speed is important.  For a factory stock engine, peak torque in a 22 is between 2800 and 3200 RPMs.  So to maximize fuel economy based on torque, in 5th gear at 65 MPH at 2800 RPM should provide optimum fuel mileage.  In my truck my RPMs is about 3100 in 5th gear at 75 MPH.

Keep in mind that the stock harmonic balancer/pulley has a specific mass and diameter for a reason…. The Japanese Toyota automotive engineers are arguably the smartest on the planet.

Elevation can have a dramatic affect on gas mileage.  On the Ducy Ershim Trail, the carb'd V-8s got about 1 MPG at 9,000 feet elevation.

That's just my opinion - it may be worth zero MPG.

Gnarls.

[sirdeuce [OP]]

This is an '89 2WD 22RE. Current tune is good, but the engine pings with 89 octane fuel(not my build, I think the squish is excessive), gotta run premium and keep the timing at stock spec to keep the ping away. Just looking to play with this. When I take the trip from Clovis/Fresno to Atascadero and back, keeping the speed within 5 MPH of the limit I get 26 MPG. Yeah, I cruise this little truck, the MR2 is for the fun stuff. Not too concerned with the cost really, just playing with things before I start adding mods and throw mileage out the door.

Last time I get this itch built and tuned a 4AGE to 47 MPG. When gas was 5 bucks a gallon and I was putting nearly 100 miles a day in the commute it made a difference. Hell, when everybody else was complaining about gas prices I didn't really care. That's what you get for driving big ass F250s for work.

[Snowtoy]

Disconnect the power steering pump belt on the next trip, and see if that increases your mpg's.  If it does, you will have something to work with, and then decide how long it will take to recoup the $100 dollar investment in an LCE underdrive pulley.

[Gnarly4X]

Duecie,

How much gain in gas mileage would be your target above your 26 MPG?

The very best I ever got on my 1986 Toyota longbed, 22RE, automatic trans was 28 MPG.  I was deliberately trying to get higher gas mileage.

I’m curious if it’s possible to get above 28 MPG (and how higher) on a 22RE without radical modifications or changes to driving.  Or can we get a 22RE to get above 28 MPG with some basic mods, like underdrive pulley or with a different cam profile (change overlap and dynamic compression)?

Is the injector system on the 22RE the limiting factor?  Do all 4 injectors on 22RE get pulsed/fired at the same time no matter what spark plug fires? Does the ECU control the pulse width individually on each injector?

I have been recording my gas mileage and odometer reading on every time I fill up my tank for many years.

Depending on how much time you want to spend working to get a gain in MPG, there are number of things I would try.  Accurately calculating gas mileage is tricky.  I’d start with a baseline number.  I’d run 3 tanks of fuel with carefully tracking my miles per gallon, MPH driven, and try to maintain the very same driving style. If possible, the same route. 

Then I’d start with only one change or modification, and record the mileage after the change or mod.

But…  you could simply buy and install an underdrive pulley and run a couple tanks of fuel and record the results.

I’m curious what your results will be.

Gnarls.

[redneckcustoms13]

Snow toy hit the nail on the head. I have 2 1st gen 22r trucks that are identical in every way except one has power steering, other does not. Same tires, same wheels, same gears. The power steering truck gets ~15 mpg the non power steering truck gets 18-20. That little pump robs alot from an already underpowered engine to keep up with modern speed limits.

[sirdeuce [OP]]

Years ago I had a '77 Celica that I tried improving mileage. I found a larger diameter alternator pulley and put an electric fan on the radiator. Those gained 3 1/2 MPG overall. That was a 20R ported oversize valve head on a 22R block with headers and a Weber 40DFEV, the exhaust was 2 1/2" with cat and glass pack exiting just ahead of the driver rear tire. The cam was one from a shop called 'The Toy Store", been gone for decades, their specs were something like 27X in 26X ex with nearly .430" lift(best of my recollection). Only got about 22MPG typically, but ran like a raped ape.

So, Tony at LC performance says their 4" crank pulley won't be good in stop and go traffic, but I think I'll give that pulley a shot since most of my travels in this truck are highway miles. Around town I use our cars.

[Snowtoy]

Wonder if running a same % smaller Alt. pulley to go with it would resolve the stop and go traffic issues for the alt.