How does a tune up result in better gas mileage, specifically?

[Southbound]

Everyone seems to believe that a good tune is critical for good gas mileage but as I'm thinking about all the things that happen during a tune up I can't imagine any one of them making that much of a difference. Maybe each step just makes a little difference and together the effect is larger. Anyway, I'm interested in how all the steps in a tune up lead to better fuel efficiency.

Thanks

 

[prairie wolf]

remove one plug wire.
pull 3 vacuum lines.
turn distributor about a 1/2 in.

take 200 mile drive.

that will answer your question.


life is good.

 

[High Desert]

Things wear out or just get old, plugs, ignition wires loose conductivity or crack, vacume hoses become brittle and don't seal. Carbs clog, and get out of adjustment. Valves trains wear and need adjusted to keep in spec...even belts getting loose.

Some or all of this gets out of wack and you start to loose performance (what little you have anyway) and engine efficiencey...MPG..

Just a quick primer..get the OEM shop manuals..That information and maintanence scheduels will help prolong your Cruiser experience with any given Cruiser...

 

[bigbrown]

i'm fortunate to have one of those rigs that gets good mileage. i found that either got 13-14mph on the low side or 16mpg if i advanced it slightly.

i took others advice and advanced it until it pinged slighty under load. then set it back slightly. i didn't follow the 7 tdc guideline or whatever it is. no ping, easy startup, good power, and good mileage for a 2f. i can get over 300 miles before looking for a gas station.

i also keep fresh plugs, filters, and oil in it

i guess timing is important

 

[Southbound]

i'm fortunate to have one of those rigs that gets good mileage. i found that either got 13-14mph on the low side or 16mpg if i advanced it slightly.

i took others advice and advanced it until it pinged slighty under load. then set it back slightly. i didn't follow the 7 tdc guideline or whatever it is. no ping, easy startup, good power, and good mileage for a 2f. i can get over 300 miles before looking for a gas station.

i also keep fresh plugs, filters, and oil in it

i guess timing is important

Wow, that's huge! Those are some very encouraging numbers. What's the drawback if you advance the timing too much - you start to get pinging and loose power?

 

[bigbrown]

i could definately tell when it was advanced too much since i climb a steep hill on the way to work. (pinging)

i think with these engines having little vacuum leaks here and there, setting the timing visually with the timing window might not be the most efficient way.

i would like to know if others agree though. i would hate to do long term damage for a few mpg increase.

 

[RredFJ40]

Pinging is detonation. It can blow headgaskets and holes in your pistons. To that end follow big brown's advice and advance it until it pings under load and then back off a little bit. exact degrees of timing doesn't work because elevation plays a role, it will be different for each location and each engine. You need to find your cruiser's sweet spot. FWIW, I get 17mpg corrected on road trips in my 82 (see specs in sig).

 

[rockyklg]

sorry for the highjack but how much do you advance it each time? 1*, less?

 

[lonelydriver]

Pinging is detonation. It can blow headgaskets and holes in your pistons. To that end follow big brown's advice and advance it until it pings under load and then back off a little bit. exact degrees of timing doesn't work because elevation plays a role, it will be different for each location and each engine. You need to find your cruiser's sweet spot. FWIW, I get 17mpg corrected on road trips in my 82 (see specs in sig).

wow 17??

what does your 62 get?

 

[Mike S]

I was getting 16 - 17 pulling a trailer with my stock 60 with 31" tires and ah... a 5 speed. Does that count?

M

 

[philos1]

remove one plug wire.
pull 3 vacuum lines.
turn distributor about a 1/2 in.

take 200 mile drive.

that will answer your question.


life is good.

p-wolf- the point here is to help out, not be an a$$. southbound has some interest in learning how and why tuning affects his rig. be nice or go away please.



back to the thread- good spark= better burn of fuel (plugs, wires, cap, etc.)
cleaner jets on carb= more efficient burn of fuel (clean carb, fuel filters)
less air restriction= better mix of fuel/air (air filter, free-flowing exhaust, etc)
cracked vac lines= vacuum leaks= bad air/fuel mixture, also can affect timing control devices (change vac lines)



that's all i can think of for now, HTH....

 

[Southbound]

p-wolf- the point here is to help out, not be an a$$. southbound has some interest in learning how and why tuning affects his rig. be nice or go away please.



back to the thread- good spark= better burn of fuel (plugs, wires, cap, etc.)
cleaner jets on carb= more efficient burn of fuel (clean carb, fuel filters)
less air restriction= better mix of fuel/air (air filter, free-flowing exhaust, etc)
cracked vac lines= vacuum leaks= bad air/fuel mixture, also can affect timing control devices (change vac lines)





that's all i can think of for now, HTH....

It's all good, I don't bruise that easy.

That's exactly the kind of info I was looking for, thank you. The more details the better.
Can anyone explain how dialing in the timing can effect performance/efficiency? What is it exactly that we are adjusting, the timing of the spark in the combustion cycle? Does that need periodic readjusting or is it a one time deal?

 

[rockyklg]

an old mechanic friend of mine used to say that an engine is basically an air pump. the more easily the air goes through the "pump" the better the effeciency( read mileage). the other big part is complete combustion. a tune up generaly replaces and adjusts all those parts that wear to reduce the effeciency and those that could create problems for complete combustion (including the mixture, and the ignition). the mixture is the amount of gas and air. too much gas, it wont burn all the fuel, too little and it gets too hot... think of a cutting torch. the timing is the point relative to top dead center (when a given piston is at its highest point of travel) advanced and the plugs spark a bit before TDC and retarded a bit after. timing theory is bit complex for me... adjusting the valves makes up for the wear of the mechanical parts limiting the significant amount of restriction they create in this "air pump". so i have no idea if that helps or not but i hope so. GL

 

[lowtideride]

less resistance...better mileage.



Less web wheeling more wrenchingg....have at it hoss.

 

[RredFJ40]

wow 17??

what does your 62 get?

ehhh, like 12. the smogged, injected, computerized, and auto-trannied rigs have me stumped. Seriously I just haven't taken the time to get it right (adjusting the valves is a PITA!)