Mpg?

[Out of my mind CJ5]

why not buy an old diesel and convert it to veggie oil, i had one and never paid a penny for fuel in the summer, just have to get the engine warm in the winter before you switch it or you are S.O.L my friend (been there done that, it sucked) i think i paid 1200 and it was an old mercedes, i used to run over small trees at 50 just to try and kill it and never could it was bullet and tree proof

 

[ThisGuyUKnow]

Where are pics of this scrambler?

I tell you what my 7 gets way more than 9 mPG why dont you jsut trade me your scrambler?

 

[kickitandholdit]

not sure how intense you are about MPG but people make 2 stroke 80cc motor kits that you can bolt on to a bicycle and it comes with everything you need but the bike. They will run about 35mph and they get between 100-AMC 150 mpg depending on how you drive them and how heavy you are. I know this is completely off the wall but i thought yal might thing it was interesting. Might be a fun build for your kids at least.

 

[Rescue Diver]

OK, don't kill me here just hear me out.

I have a new position with my company that has moved me from working from my home to working in a office that is a 50 mile round trip every day. I am driving my 1985 Scrambler with 78K original miles daily. I love my Jeep and want to keep it. My problem, the Jeep gets around 9 mpg and it burns almost as much oil as gas. I have factory auto and air and want to keep both though not necessarily factory but the factory look. With me so far? What I need is a new motor and if necessary Transmission that will significantly improve my gas milage. My goal is mid 20's and if necessary I am willing to even give up my 4wd capability to keep the Jeep. I hope that isn't necessary but again, I don't want to loose my Jeep but I want my house more. Thoughts, diesel, 4cyl, hy-bryd, electric? Go crazy, no idea is off the table...

Thanks for the help,

Tom

With still not having my speedometer calibrated and reading correctly, I have no idea what my actuall MPG is, but I do know I gained a whole lot when I did the 4.0 head swap on my AMC 258 i6 / 4.2l . I was going through a full tank of gas every three days to work with my 50 mile round trips. Now I can get to and from work four days on the same tank of gas. The swap will definitely pay for itself in gas savings, and I gained a lot of very noticable power to boot! I would probably gain even more if I switched to the factory 4.0 fuel injection, but I like the simplicity of my MC2100 carb and mechanical fuel pump.

 

[Rescue Diver]

not sure how intense you are about MPG but people make 2 stroke 80cc motor kits that you can bolt on to a bicycle and it comes with everything you need but the bike. They will run about 35mph and they get between 100-AMC 150 mpg depending on how you drive them and how heavy you are. I know this is completely off the wall but i thought yal might thing it was interesting. Might be a fun build for your kids at least.

That would be a fun toy, but I thought anything over 50cc had to be licensed? It might get interesting trying to get a bicycle inspected and tagged for street use.

 

[Busted Knuckles]

Not sure what happened to the poster of this thread ?

 

[kickitandholdit]

That would be a fun toy, but I thought anything over 50cc had to be licensed? It might get interesting trying to get a bicycle inspected and tagged for street use.

Yes not to mention it would pay for its self with the mpg. To bad a jeep cant get those kind of #s haha. It would be illegal to have over a 50cc if it was classified as a motorcycle but its classified as an assisted bicycle. Some towns prohibit assisted bikes though but most dont have a clue what they are. Even if a cop stared being a jerk about it.. just cut the motor off and start peddling and go on about your business on your bicycle. I posted another thread about a guy that made a military one. Not meaning to highjack the thread

The best thing i have seen people do is give up on trying to get mpg out of a jeep and buy an ole $1200 2wd mazda single cab pickup and get about 30 mpg stock

 

[Rescue Diver]

The best thing i have seen people do is give up on trying to get mpg out of a jeep and buy an ole $1200 2wd mazda single cab pickup and get about 30 mpg stock

One thought I've had is, there are a million 1990's Chevy S10 blazers around that are crapped out and can be had really cheap. They get what, about 20mpg with the 4.3 liter? Why not just buy one of them for parts and swap the entire engine, tranny and Transfer Case into a CJ? With the lighter weight of the Jeep, I'd think you would probably get around 24 or 25mpg?

Has anyone on here ever done that swap? I'd love to hear how it would turn out.

 

[CJ]

~~~ Has anyone on here ever done that swap? I'd love to hear how it would turn out.

Not a CJ, but here is a YJ 4.3l swap.

BowTie YJ - Jeep-CJ Gallery

 

[Rescue Diver]

Not a CJ, but here is a YJ 4.3l swap.

BowTie YJ - Jeep-CJ Gallery

Nice!

Any info on how it performed or what MPG it was getting?

 

[CJ]

I'm not sure if he still has it. I will try and get a hold of him this weekend.

He started this thread then went MIA. -->> http://www.jeep-cj.com/forums/f69/building-bowtie-yj-389/

 

[Rescue Diver]

I'm not sure if he still has it. I will try and get a hold of him this weekend.

He started this thread then went MIA. -->> http://www.jeep-cj.com/forums/f69/building-bowtie-yj-389/

I hope you can reach him. I've always been a Bowtie guy. I had a Grand Cherokee with a 318 V8 a few years back that I bought to haul my Baja, and it would barely maintain 60mph up highway hills with the boat in tow. I sold it and bought a 96 Tahoe with a 5.7 liter vortec. I was amazed that with all the extra weight of the Tahoe and a not much larger V8, it could still hold any speed up to 80mph with the boat behind it and it only got one less mpg at 17mpg on the highway without the boat compared to 18mpg for the Grand Cherokee. It would be really cool to build a light weight CJ with the Chevy 5.7 powertrain. I'd bet that combo would get around 20mpg or better on the highway and have more power than you could ever need in a CJ. I plan to build a stroker using a 30 over 4.0 block with my AMC 258 i6 / 4.2l crank eventually since I've never built one of those before, but a 4.3 or 5.7 Chevy swap is really tempting because of the smooth power and great mileage.

 

[ThisGuyUKnow]

That figures out to be 1500 rpm in top gear, thats a little low. 1900-2100 is better. Try a run with 4th gear.

Did a round trip to St Louis today and took your suggestion here. It was hard to get over the urge to use 5th but I averaged 20+mpg the whole way with the exception of one leg were I used 5th I got 17 that leg.

Hopefully when I get around to installing my 3.54 axles I can use that 5th gear. Thanks for the Suggestion!

 

[IOPort51]

@73cj where did the 1900 -2100 RPM figure come from??

 

[Kane]

I have a 350 in my Jeep that is well built but with my 4 barrel and a semi heavy foot I get 12mpg. This morning I disconnected the secondaries and zip tied them shut so i am only running on the smller primaries. I am going to run out an whole tank and see what happens. I want to use this motor for my Scrambler but I want to drive it allot and 12mpg is just too low for me. Even with just the two barrels the motor goes better than my older AMC 258 i6 / 4.2l ever did.

 

[Rescue Diver]

I have a 350 in my Jeep that is well built but with my 4 barrel and a semi heavy foot I get 12mpg. This morning I disconnected the secondaries and zip tied them shut so i am only running on the smller primaries. I am going to run out an whole tank and see what happens. I want to use this motor for my Scrambler but I want to drive it allot and 12mpg is just too low for me. Even with just the two barrels the motor goes better than my older AMC 258 i6 / 4.2l ever did.

What size/model 4 barrel do you have? If you're running a Holley vacuum secondary, I'd suggest instead of disconnecting the secondaries, you should just buy a secondary spring kit that will allow you to make them only start to open if you keep your foot on the floor for a really long time.
A 600CFM vacuum secondary holley is a great carb for a moderately built 350. A lot of 350 owners seem to think they will gain HP if they use a bigger carb like a 750cfm, but all that does is hurt throttle response and make them waste gas. One other thing to try if you haven't already, is to adjust your distributor mechanical advance so it's as far advanced as it can be without pinging. That will give you the best MPG by burning the fuel more completely while making it run better and faster at the same time.

 

[73jeep]

@73cj where did the 1900 -2100 RPM figure come from??

Just an educated guess from personal experience.

Its a fine line to get that sweet-spot. Below 1800 your lugging the engine too much and that requires more fuel due to higher internal friction. Above 2500 rpm and your pumping losses from revving the engine past the optimum power band increases fuel consumption.

Its a balance between the two while still making sure the engine can produce the amount of power required to drive the jeep down the road.

 

[Rescue Diver]

Just an educated guess from personal experience.

Its a fine line to get that sweet-spot. Below 1800 your lugging the engine too much and that requires more fuel due to higher internal friction. Above 2500 rpm and your pumping losses from revving the engine past the optimum power band increases fuel consumption.

Its a balance between the two while still making sure the engine can produce the amount of power required to drive the jeep down the road.

Those numbers sound about right to me from personal experience.

 

[IOPort51]

Do they have any relation to the power / torque curve??

this is a rhetorical question that I should be able to find for myself but if anybody has that in front of him, feel free to jump in.

 

[Kane]

What size/model 4 barrel do you have? If you're running a Holley vacuum secondary, I'd suggest instead of disconnecting the secondaries, you should just buy a secondary spring kit that will allow you to make them only start to open if you keep your foot on the floor for a really long time.
A 600CFM vacuum secondary holley is a great carb for a moderately built 350. A lot of 350 owners seem to think they will gain HP if they use a bigger carb like a 750cfm, but all that does is hurt throttle response and make them waste gas. One other thing to try if you haven't already, is to adjust your distributor mechanical advance so it's as far advanced as it can be without pinging. That will give you the best MPG by burning the fuel more completely while making it run better and faster at the same time.

I took my Holley 670 truck avenger off two weeks ago to go back to my Edelbrock 600 cfm 1405 carb. I have a full blown tune kit for that carb so I wanted to mess around with it. The holley allready had the heaviest spring on it for the secondaries but the best I could manage was 10-12MPG. The Edelbrock bumped me up to 13.9mpg for one tank and then 12.5 on my second tank but I drove it harder the second time. I want to see what I get with just the primaries since they are smaller more like a Qjet spreadbore. If I can get 14mpg and then switch to a 5 speed in my Scrambler to bump me up some more then I will be fine with that. When I hit the trails I can hook up the secondaries for the horsepower and more fun times. I understand what you say about the carb sizes. I am pretty decent at tuning them but it takes time and patience to get it right.