MPG improvement
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
MPG improvement
A few weeks ago I swapped the Carb and dist on my 81 for non computer models, I unhooked the computer as well. I also removed the EGR, I had previously removed all of the smog junk, and added 2.5 inch true duals. I filled up the tank with gas right after I did the swap. 2 weeks ago I finally finished the exhaust work with my header install. Yesterday I gassed up thinking my gage was not working correctly. I got 16MPG in town, not babying it!! I was getting maybe 10 before the work. AND I have been putting my foot in it a bunch because of the new found power and sound after. So if I stay out of it , I will get even better, I never expected this kind of increase, but am pleased to say the least. I have always said if you properly tune an engine you can gain HP and Mileage, some beleive you have to sacrifice MPG for performance, and that may be true to some extent, but on a mildly built performance motor both can be acheived. 
Team Owner
Joined: Jul 2008
Posts: 23,419
Likes: 22
From: In limbo
St. Jude Donor '13-'15, '17 thru '22
A properly running engine is pretty much always more efficient than one that is running like crap. When I got my car ('70 BB), the engine seemed to run fine, and even passed emissions, and I was getting about 7 mpg average (very little highway driving). Soon, the carburetor problems surfaced. Eventually, I just swapped out the carb for a new one of the same model, and re-tuned the engine. Now, I feel like I get as much or more power, and I get 10 mpg, a 43% improvement. The idea that improving performance and improving mileage are always mutually exclusive is not well-founded. Improving performance by generating a proper and more complete burn in the engine should always improve mpg.
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
A properly running engine is pretty much always more efficient than one that is running like crap. When I got my car ('70 BB), the engine seemed to run fine, and even passed emissions, and I was getting about 7 mpg average (very little highway driving). Soon, the carburetor problems surfaced. Eventually, I just swapped out the carb for a new one of the same model, and re-tuned the engine. Now, I feel like I get as much or more power, and I get 10 mpg, a 43% improvement. The idea that improving performance and improving mileage are always mutually exclusive is not well-founded. Improving performance by generating a proper and more complete burn in the engine should always improve mpg.
It was running(what seemed) very good before, but now it runs great. I think also setting the dizz to a better curve and advance helped a bunch, and I am not too sure the computer was working at all, it may have been in default which gives the old E4ME full rich condition. The idle is smoother now, it has zero flatspots. I have been a bike tuner for eons and I have always told guys I can tune thier bike and get way more HP and pickup substantial mileage, they always argue till done and then thank me! 
I just wanted to post this so other guys with that same misconception can be enlightened and you did just that.
Team Owner
Joined: Jul 2008
Posts: 23,419
Likes: 22
From: In limbo
St. Jude Donor '13-'15, '17 thru '22
Agreed on all points. An appropriate advance curve should also give that "better burn" and improve performance and mileage at the same time. Idle is often where numerous engine bug-a-boos show up. Last year, I had mine idling at about 600 rpm smooth as silk and with such a great sound. Since then, I have developed a minor vacuum leak, and I don't get a good idle until about 850, and even then, it is a little bumpy sometimes. I have lots more wrench-turning in my future!
