Well...I know this is somewhat OT here....but how much spark advance would tricking the computer on a Vette(or any other chevy for that matter) into thinking that it was always 55 degrees out be?

Any advantage/disadvantage to doing this? Horsepower gain/loss? Torque? Car in question is mine in the sig...wondering if anything is gained by doing this...I have had the resistor in place for a few months...seems to make it run a little rough at idle and below 900 rpms, but I don't really know how much it hurt/helped above that. :cheers:

 

Nobody? :eek: :lol:

 

Probably the reason why no one has responded is that we have no idea of your objective. What do you want to accomplish? Knowing the model year and engine would help.

Engine timing requirement is a function of speed, load, and detonation characteristics. Speed and load are usually represented by engine revs and manifold vacuum, and detonation sets an absolute limit on timing for any condition.

The two independent variables - speed and load - determine the basic timing requirement, and there are essentially and infinite number of conditions. Plotting a timing map on on the three othagonal axes with yield a "surface" with timing that typically ranges from near zero to 50+ degrees.

As a rule, modern engines with knock sensors have aggressive timing maps because running the engine on the ragged edge of detonation is the most efficient and will yield the most power and lowest fuel consumption. Modern high compression engines also have two basic timing maps, one for premium fuel and one for regular. The premium fuel map is more aggressive and will usually be apparent as better throttle response and more low end torque to a heavy footed driver, but average drivers usually can't detect any difference in performance between premium fuel and regular fuel, even is the manufacturers recommendation is premium fuel.

So what are you trying to achieve?

Duke

 

Gotcha. Engine is a 3.1 MPFI V6, the objective of advancing the timing at first was just to get a lumpy idle(which worked), but now I am just wondering how much advance is actually being used, and what it will affect.

For example, if the car thinks it is 55 degrees out while it is really 80-85, how much advance is it getting, and what will this yield?

Also: I highly doubt that my car had an aggressive timing curve to begin with since the engine is definately not high compression, and the computer hasn't given any knock errors with the timing tricker installed. I still use 87 octane, though 89 smooths out the idle when I do use it. Rest of the time there is no difference between the octanes.

Thanks for all the help! :cheers:


[Modified by TheWacoKid, 6:51 AM 9/26/2003]

 

ttt :cheers: