I've heard for years that advancing the timing will increase fuel mileage, but have never tried it, because I fugured it would just be a hastle trying to find just how much to advance it. Has anyone ever advanced the timing on their car and seen an increase in fuel mileage? If so how much did you advance the timing? I was thinking about trying it on my '88 Escort, it's factory set timing is 8* BTDC. How much would some of you gear heads suggest advancing it?
Yes and no. The only vehicles I did that on were my 74 Chevy and Rusty. Rusty used to get better mileage on premium with the timing advanced, but dad wanted me to retard the timing so he could run 87 octane in it. With the timing retarded the truck struggles to get 10 MPG.
In my 74 Chevy I used to get high 20's on the highway, I never really drove it with the timing set to specs, so I don't have a comparison on that vehicle.
I advance it till it pings a little in hot weather under heavy load/low rpms (conditions that I rarely put the engine under) and I leave it there. Not heavy regular pinging- just a small bit of irregular pinging.
I believe that I have gained a little bit by doing this. My "proof" is that the idle speed increases slightly when I advance the timings slightly more than the factory recommended setting- thus more of the energy from combustion must be going into spinning the crankshaft because it turns faster. Since my car has a carb and no computer controls- I know it just isn't the computer dumping in more fuel (the carb throttle valve remains at the same angle).
it's factory set timing is 8* BTDC. How much would some of you gear heads suggest advancing it?
Hi Ford man. Don't forget this 8? is only the idle setting. The real timing depends on rpm (the higher revs, the more advancing) and load (the more load, the less advancing).
I suppose you only want to change the basic setting? Generally spoken you can win much more by advancing it more under certain working conditions (low load, mid rev range). And leave it standard for exceptional conditions (high load low revs) so no knocking will appear. You can achieve this with changing the springs (rev related) if your Ford still has the very very old advancing system (no electronic ignition).
But you're lucky: your car is an old one and advancing it some ? will hurt nothing as there is a certain safety margin. Watch out: FE will drop again at a certain timing as you will see the mixture will start burning to early and slow down the piston while it still goes up.
I can't change anything on the vehicles I drive. But my Honda Civic is supposed to search for the 'borderline' in timing all the time. The ECU advances till the slightest sign of knock is captured. This way it also adapts automatically to the fuel octane rate (95 or 98 RON).
For almost a month, I tried to maximize the timing in my new '98 Riv. (I am lucky to have access to one of those fancy computer links where I can do stuff like that)
I advanced timing a bunch in many areas of the tables. My average was probably 5 degrees, but in some cells I was up 10 degrees.
If anything, my MPG probably went up 1/4 to 1/2 of an MPG. Obviously I was hoping for more.
I also have found that factory timing tables have dramatically different strategies. My wife's old Taurus had too much timing from the get-go, and I could always tell when she used 87 Octane. Due to my dislike for replacing head gaskets, I insisted that she used 89 octane.
On the other hand, the Buick that I'm driving now had too little timing. I was able to advance just about the entire timing table by a minimum of 3 degrees, sometimes up to 10, before I'd get into the knock zone. But like I said above, it didn't gain a lot of MPG.
Now of course my experimentation was much simpler than the factory setup. They have access to 5-gas analyzers (I only have a narrowband O2), exhaust gas sensors, and much more sophisticated in-cylinder monitoring equipment. They are also required to meet very specific emissions requirements, and I only have to keep my SES light off. But I had to kinda re-evaluate the factory settings anyhow, since my engine has a bunch of internal mods (bigger cam, ported heads, higher ratio roller rockers, headers, smaller supercharger pulley, etc.).
I think my best bet is just to draft behind big trucks.
how much it helps depends on the engine. advancing the timing by itself doesn't provide better economy but it does allow better economy. It allows you to get more power out of the same amount of fuel/air, which if you keep a light foot, will result in some economy. as the other guys pointed out here, make sure you run high enough octane but don't expect a huge improvement.
My Cressida gained less than 1 mpg advancing from 10* to 15* and in 85f+ in traffic where there wasn't much airflow to keep the charge air cooler it would ping slightly even on premium. that was with my old engine....pretty tired and loose. the new one's set to stock but there's only 25 miles and not much chance of more any time soon.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
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