Nobody... Where's the daring... I'll have to try to find more info and answer myself

 

OK, here goes. In a perfect world, where complete combustion occurred instantaneously at TDC, there would be no need to advance your timing. In the real world, however, this doesn't happen, i.e., it takes a certain amount of time for all that inducted air and fuel to burn completely and produce the optimum pressure to drive the piston down on the next power-stroke. Hence, the fire needs to be started a little in advance of TDC, more so as the rpms increase because there's less time for the combustion event to occur. In actual practice, timing advances in the range of 5 to 35 degrees will be encountered, depending upon the engine, the load, the RPM, and the fuel being used (some fuels burn more readily than others). Hope this helps.........

Cheers

 

Advance = Hotter Combustion Burn

Retard = Colder Combustion Burn

You can also install hotter or colder spark plugs to adjust the burn...

 

Im no authority on this but Sparky has coached me and helped me with alot of stuff one thing being the timing curve. Search the thread I started regarding the dynatek box and you will see the curve I run with boost. Its aggressive and my buggy goes like stink.

 

Cool. Thanks Bar. I can clearly see that the basis is from TDC, which makes obvious sense now. The term "degree" of advancement is based on the rotation of a distributor cap on a 360 degrees? If this is true how can one reference a degree to electronic ignition?

E85 is like 105 octane, thus the need for advancement... So if you don't advance correctly you'll lose out on a lot of potential energy as it's blown out the exhaust, correct?

 

Cool.. The term "degree" of advancement is based on the rotation of a distributor cap on a 360 degrees?

No it is degrees of Crank rotation. Electronic ignition it must be done through the means of an external controller such as the pcv.

 

U got the means to copy my curve.

 

No, not there yet Jamie. Just thinking about options right now. I fully intend to take a similar route, but I'm in the middle of a shock situation at the moment. Thing is that I'm not sure what to do about going PCV or just get a Dynatech. I don't want to have to deal with a bunch of O2 bungs cut into my manifold. Autotune sounds great. Maybe I'll call you sometime to discuss options.

 

Man PCV and a map sensor, with timing control is pretty much the ultimate, this a allows all control with one box and very comprehensive maps!

 

Thats the route that I went. I need to play with the timing though. Stock map in for ignition right now, thats why I was asking questions in your other thread.

 

Can the PCV show you the stock map? Im not aware of how it works no experience, other than I know its the king for tuning.

 

I believe it just shows how it is currently set, in degrees at any given RPM. Unless you save the base map. I think. I will go plug in and see how its noted, either in a number at a given rpm, or a +4, +5, etc...

 

This is my current setup the way I received it. So, it does display it in just a + or - number, not actual. so theoretically, if I zeroed it out, I should be at stock.

 

amazing how it's +2 at the lower rpms

 

Jim the simple and dirty explanation has to do with flame travel. Flame travels across a combustion chamber at the same rate no matter what you do to the combustion chamber. Different chamber designs allow you to run higher compression and more advance as well as higher octane levels. Basically you are trying to achieve the most bang you can get as close to top dead center as possible. Keeping combustion temps down is key. Higher octane levels allow cooler combustion temperatures since they tend to burn cooler. Higher compression levels raise combustion temps and boosted engines see even higher compression so the need to keep temps down is even more critical. Engines live on fuel. The more you can cram into one, the more power you make. All the other things we do to make power are geared toward one thing and that's getting more fuel into the engine. Boosting gets you enough additional air to get that extra fuel into the engine. Nitrous does one thing, it breaks down under heat and pressure to make enough oxygen to burn all the additional fuel you cram into the engine when you hit the loud button.
In early days everyone in the automotive arena started building high performance engines with closed chamber or quench" heads. The design actually blows the flame out as it gets squeezed into that part of the combustion chamber that sits flat against the top of the piston. less flame equals less combustion temps and you could run higher compression pistons with them and still maintain more static advance.
Too much advance and you start the explosion too soon raising the combustion temps since most of the power is hitting a piston that is still on its way to top dead center. Boosting doesn't need additional gas to keep everything happy, we look at it backwards a lot. the gas needs all that extra air to burn.
One thing to remember with lower compression pistons is it allows you to get more fuel/air into the engine mostly because there's more room in the combustion chamber. More room means more fuel, more high octane fuel means lower combustion temps and more power.

One other thing about cylinder head design, aluminum heads are extremely popular in the automotive high performance world for a couple of reasons but the one immediate thing is that aluminum absorbs and dissipates heat way faster than steel or iron and this allows for higher compression and timing in most engines.

 

Jim the simple and dirty explanation ....

Thanks Tom. Good explanation. Seems kind of obvious now, but wasn't tying the degrees of crank rotation to the the fire start to the fuel type (octane).

Somebody else will read this and wonder no longer. Appreciate all those who input.