Improving MPG's

[Lockman]

Hello everybody,
As some may know, I came to this forum with a unique vehicle. I have an '84 Hot Air with a 700R4 tranny in my '75 Jeep CJ5. I have learned a lot thru you guy's & have done a lot of maintenance improvements to this 17K mile, 36 Year old engine. New chip from Eric, exhaust headers dye checked & welded, new vacuum lines, wires . ect ect.
It runs very well coll & warm. I can spin the rears from a standstill with 3:73 gears. That's good enough for me, it's not for racing. I very please at the work I've done.
My question is : the air intake is a the stock air horn & it points toward the DS exhaust manifold, about 10" away. If I install a cold kit toward the front , could that help with improveing my gas mileage ? I know it's a Jeep , running 31 X 10.5 tires & the gears are what they are, but I am only getting 10-12 MPG running 93 pump gas , as a DD to & from work. If I go on the Hi-Way , it does better at around 60 MPH...... I'll get it up to 18 MPG . my other questions would be, what could I do to improve the DD, around town, MPG ?
Thanks in advance.... for all & any replies . I need some guidance & advice.

 

[deezdad]

Look into a 180° t-stat if your running a 160° currently. Also synthetic oil at recommended thickness 10/30 ? Synthetic trans and differential fluid could help out as well.. extended drain intervels could offset the costs while improving mileage just a couple thoughts..

 

[Turbo6inKY]

Hello everybody,
As some may know, I came to this forum with a unique vehicle. I have an '84 Hot Air with a 700R4 tranny in my '75 Jeep CJ5. I have learned a lot thru you guy's & have done a lot of maintenance improvements to this 17K mile, 36 Year old engine. New chip from Eric, exhaust headers dye checked & welded, new vacuum lines, wires . ect ect.
It runs very well coll & warm. I can spin the rears from a standstill with 3:73 gears. That's good enough for me, it's not for racing. I very please at the work I've done.
My question is : the air intake is a the stock air horn & it points toward the DS exhaust manifold, about 10" away. If I install a cold kit toward the front , could that help with improveing my gas mileage ? I know it's a Jeep , running 31 X 10.5 tires & the gears are what they are, but I am only getting 10-12 MPG running 93 pump gas , as a DD to & from work. If I go on the Hi-Way , it does better at around 60 MPH...... I'll get it up to 18 MPG . my other questions would be, what could I do to improve the DD, around town, MPG ?
Thanks in advance.... for all & any replies . I need some guidance & advice.

Short answer, no and not a lot.

Longer answer - cold air helps with power because the charge is denser and it reduces knock, which allows you to get away with a tad more timing advance. The denser charge requires more fuel at the same throttle input. Now, you'll just end up using less throttle to move the vehicle, so that'll come out in the wash. You also don't have a sophisticated enough ECM to take advantage of lower intake temps to modify the timing, so it's going to basically be safety margin.

That said, Is a cold air intake a good idea? Yes. Will it increase fuel economy? No.

Really, it comes down the brick you've installed the engine in. It takes x amount of power to push it through the air any particular speed. Your engine requires n gallons of fuel per hour to produce that output and move the vehicle.

You have to either reduce the amount of power required to move the vehicle, or reduce the Brake Specific Fuel Consumption (BSFC) of the engine.

Things you can do to the Jeep? Tires. Get rid of the 31x10s and go to a normal 6 or 7 inch wide light truck road tire. You'll reduce the mass at the axles and dramatically reduce rolling friction. That'll probably buy you two or three miles per gallon across the board. If you're running a soft top, get a hard top. The flapping fabric causes a lot of drag. Running with no top is going to be the worst situation.

Reducing BSFC? That's going to be expensive. Better heads, different cam, more efficient turbocharger, and a better engine management system. That gets expensive quickly.

 

[Lockman]

Thanks, Gents. But I do love my ' Brick ". Tires make sense, though.

 

[Lockman]

Look into a 180° t-stat if your running a 160° currently. Also synthetic oil at recommended thickness 10/30 ? Synthetic trans and differential fluid could help out as well.. extended drain intervels could offset the costs while improving mileage just a couple thoughts..

What exactly does a hotter T stat do ?

 

[Turbo6inKY]

It increases the temp in the combustion chamber which leads to a more complete burn. Not ideal for max power, but it'll be slightly more efficient at cruise.

 

[deezdad]

What exactly does a hotter T stat do ?

In a nutshell it make the motor more efficient. Turbo6inky has wise advice as usual, also try searching 180 t-stat some interesting posts will come up by "Bruce" and others