Why are all race chips high timing?

[Fred 86 GN]

At least all the ones I have seen or read about are 26° or higher. Would be nice for me to have a race chip (100% fuel) with 22° or 23°.

Is the extra timing needed to light the fire better? Seems more boost is safer than more timing when trying to not blow headgaskets.

 

[Turbojorge]

As I understand, Timing makes Torque, Torque rules the drag strip.

For stock motors, you need timing to make power because it doesn't "breath" very well at high boost (24psi +). I'm not quite sure if 1* of timing REALLY substatutes a pound of boost, but I've been told that it does by people who have ran these cars with over 30* of timing (Jeff Foxx).

Don't take any tuning advices from me though.

 

[Mike Licht]

Plain and simple timing makes power. We are trying to balance three things here, Boost, timing and octane. When octane is low (pump gas) lower timing has lees of a negitive effect at high rpm than low boost. When octane is high add the timing back and you will make far more power, up to the octane limit.
Mike

 

[Scott231]

To summarize what Jorge said...More timing makes more power.

Then again, it is also true that more boost makes more power. You can also run lower timing and more boost (there is a long standing argument over this approach vs. high timing-less boost), but the way to make the most power is to pick a boost level you want to run at and throw as much timing at it as you can with the level of fuel you are feeding to the engine.

 

[KEVINS]

I'm guessing this has to do with the dwell of the burn (higher oct=more burn dwell?) b/c more timing also means the pistion is working against the burning of the fuel which is trying to push the piston back down while it's going up... ??? (ignoring the heat of the air for simplicity)


ks

 

[ijames]

Originally posted by KEVINS
I'm guessing this has to do with the dwell of the burn (higher oct=more burn dwell?) b/c more timing also means the pistion is working against the burning of the fuel which is trying to push the piston back down while it's going up... ??? (ignoring the heat of the air for simplicity)
ks

No, not really. Flame speed is pretty constant between pump gas and race gas, unless you make a drastic change like going to methanol or nitromethane or ... Higher octane doesn't really mean slower burning, it means that if you heat it up without any flame or spark you have to heat higher octane fuel to a higher temperature before it self-ignites. To get maximum torque you need to maximize the cylinder pressure as the piston is moving down between somewhere shortly after tdc and somewhere near 90 degrees atdc, and balance that against the losses you mention compressing the already burning fuel. Starting from low timing and advancing towards the optimum means the chamber temperature and pressure is steadily rising, especially near tdc, and the more prone to detonation the engine will be (the faster unburnt fuel ahead of the flame front will be decomposing and tending to self-ignite). If you have the octane and/or the boost is low enough you can go too far and start to lose power with too much advance, but I've read that for our engines that needs more than 32-35 degrees. As Mike said, making power is a balancing act between timing and boost for a given octane, and the more timing you run the less margin for error. In other words at 20 degrees you could maybe go from no knock to 2 degrees of retard by adding 1 psi boost, while at 28 degrees you might go from no knock to 5-6 degrees of retard with just 1 psi boost. Over the 20-30 psi and 20-30 degrees advance range the difference in power between low timing/high boost and high timing/low boost isn't very large and most people would rather run less advance than the optimum and be a little safer, which is why all chips aren't just set to 30 degrees advance no matter what octane.

 

[Fred 86 GN]

Thanks for the input! Great information!

I have noticed much more low end (torque) with higher timing chips. Does the higher timing improve the top end mph also?

 

[TurboJim]

From an older post, basically giving the lowdown on WHY timing plays a role in power:

The REASON timing gets advanced at a certain RPM isnt so much for power, although thats a byproduct, its because at higher RPM's there is less TIME to be at XYZ* and it takes TIME for the spark to jump the gap, SO, we start the ignition event ahead of shedule so that everything will happen at the point of peak power.

Lets figure it this way, dont look at the numbers, but look at the theory...

Lets say at 800 rpm, the point of power is 4* ATDC (point of power being the point where the explosion in the chamber will generate the most amount of force on the piston which will force the crankshaft around). Lets say at 800rpm the engine will be at that point for 1mS, and it might take 1mS for the spark to jump the gap. So if the timing event is shot at 4* ATDC, the spark might actually occur at 7* ATDC. So, we advance the timing say 7* from that 4* now were firing the mixture when it will generate the most force on the piston.

Now, Fast fwd to 1500-1800rpm (where most centrifugal advance would come in on a dist car). Lets say now theres .5mS worth of TIME at the point of power, and the spark still takes 1mS. Now by the time the plug fires and the charge lights, we may be at 12* ATDC. So, to get back to that point of power we need to start the timing event even earlier. Lets say we advance the timing 12* so that the spark event will coincide with that original 4* ATDC power point.

All else equal, if you set the timing at 0*, the spark/ignition event might not come off until 30* ATDC maybe... LONG after the point of power, and much of the power stroke is WASTED. Now, you may gain it back by using NOS, more boost, whatever because you're making the engine effectivly LARGER by using a power adder, but making that larger engine VERY inefficient!

So you see, there is a balance of how much timing is optimal for an engine to make power. Pretty much as Carl said.