timing, set for mark or for pep?

[donna]

Did the timing per instructions under the hood, set it on the "T" mark, test drove car and all ok,,,but,,,then i rotated the dist cap clockwise 1/4 inch and test drove, the car has considerably more pep at new setting,,,so which do you go with, pep or "T" mark....and why.

[25Horseplay]

Advancing the timing might require you use premium gas. As long as it doesn't detonate you would be OK.

[floydiancomplex]

you have advanced your timing a few degrees, maybe 3-5. This will give you a bit of extra low end torque
whilst sacrificing high end power. since our cars are not all that rev-happy and don't make alot of power
anyway I feel a little advance is definitely the way to go. I run my autoX car at 5 degrees advance with
93 octane to prevent detonation. if you spend any considerable amount of time at higher (4000+) rpm
you may want to consider running atleast 89 or 91 octane. Personally I feel any car with more than 100K
should run mid-grade gas anyway due to carbon build up in the compression chambers. - Chris

[donna]

i run 89 octane already, i havent hit 4000+ rpms thou :shock: ,,,,i use the xpress way and have no pinging even in 5th gear and punch it, no pinging,,,,so i guess im ok with the new setting,,,will check mpgs on next fill up, you think they will be more, or less.....

[TominMO]

...will check mpgs on next fill up, you think they will be more, or less.....

That mainly depends on how you drive...but theoretically, advancing the timing should give you better mileage around town if you go easy on the fun pedal, because of more torque produced due to greater advance. In my lifted Subaru wagon, which weighs about 500 lbs more than a Festy, I shut off my car at red lights, coast as much as possible, etc., and regularly get 32 mpg. I have slightly advanced timing, use 89 octane, use a 40,000-volt coil and 10% larger plug gap (bigger spark), and overinflate the tires. All this gives about 5 MPG more than before I did these things. But the most important is your right foot.

See my posting under Custom Engine and Drivetrain/MSD Coil for advice on coils.

[GenevaDirt]

^^what about long distance? If you are nice to it will you still get the milage increase?

[TominMO]

^^what about long distance? If you are nice to it will you still get the mileage increase?

For highway travel the best technique is to over-air your tires, maybe a few lbs below what the tire says is the max pressure, use a light foot on acceleration, brake as little as possible, and keep the speed down to lower the effect of wind resistance. As I understand it, advancing your ignition timing only help torque, which is pulling power to overcome standing still or getting up a hill. But it won't significant;y improve HP.

[GenevaDirt]

^^but what would it do to the milage on the long haul?

[FestYboy]

as torque is increased, BSFC goes down, SO MPG goes up for a given load or speed

[roycehof]

I'm running mine a little advanced (about 4 degrees more than the timing mark). I had to adjust the Idle air control valve to get it to idle a little slower. Overall, the car runs much better with no notable detonation (only below 2K rpm in 5th, putting on a hard load). I typically get in the mid 40's driving failrly conservatively with about one third city and 2 thirds highway. All highway, running 65 mph, I almost get 50 mpg's. Last time I went from Philly ot Ithaca, NY and back it was 49.8 mpg's (and a lot of that was at 70+ mph on the Northeast extension). I have had the timing set like that for about 2 years with no problems. I think you will be fine, just don't over advance it and "ping" it to death (and don't "bog" it down in the higher gears). The factory may be a liitle conservative with the timing to allow it to burn cleaner for the emission requirements.

[roycehof]

OOPS - I run the cheap gas (87 octane) in case you are wondering. If you are willing to spend a little more for the premium gas you may be able to get a little more timing advance out of it. I'm just telling you what has been working for me. I'm not sure the payback is there to go much further with it, but if anybody else knows differently, I'm intereested.

[TominMO]

OOPS - I run the cheap gas (87 octane) in case you are wondering. If you are willing to spend a little more for the premium gas you may be able to get a little more timing advance out of it. I'm just telling you what has been working for me. I'm not sure the payback is there to go much further with it, but if anybody else knows differently, I'm intereested.

The cost difference between 87 and 89 octane is only around 10 cents--3 or 4 percent at current prices. These cars get such good mileage anyway, why not pay a tiny bit more for gas and advance the timing for more torque?

[WmWatt]

theoretically what you did should not make any difference. once the O2 sensor warms up and starts sending a signal to the computer, the computer takes over advancing the timing to minimize the unburnt fuel in the exhaust. when you manually set the timing you are setting the "base" timing". when the engine is cold the distributor in my older '89 model has both vacuum and centrifugal timing advance but when the O2 sensor gets going the computer overrides that and advances the timing itself. the override is done in the ICM (ignition control module) circuits.

[roycehof]

Yep - WmWatt is correct that alot of the running characteristics when the car is in "closed loop" mode is determine by the 02 sensor. I'm just sharing what I know about mine running a little more advanced timing than suggested. I would NOT run any more advance if I had A/C or an automatic. I pushed my advance up a little and try to make sure I don't "bog" it down and it seemd to run much better and the mileage did improve slightly. Just telling you about my "real life" findings regarding the matter.

[TominMO]

Come to think of it, three of the four vehicles I advanced the timing on were carbed vehicles. 86 Subaru, 77 VW bus (originally FI), 84 Subaru. I stuck Weber carbs on 'em, thus getting rid of any computer input to fuel delivery. The last car I did this to was my 91 Subaru Loyale which has FI. So yeah, on this vehicle maybe there is no difference? Would disconnecting the O2 sensor be beneficial as far as power output, or would it just throw a code and put the computer in a default limp-it-home mode?