Ignition and Jetting

[horsepowerfreek]

Hello Just found this site a few days ago and I think it is really good site for information.
Was wondering if we could start a discussion on how timing and jetting works?
Randy

[stevieturbo]

It's very basic, but it will give you somwhere to start

http://www.amazon.co.uk/Engine-Management-Optimisi...

[Pumaracing]

horsepowerfreek said:

Hello Just found this site a few days ago and I think it is really good site for information.
Was wondering if we could start a discussion on how timing and jetting works?
Randy

Oh christ please no. I think my head might explode. Just read this.

http://www.pumaracing.co.uk/chip.htm

and then the rest of my website.

[varnish5000]

If 14.7:1 is chemically correct, why does running richer make more power?

[Pumaracing]

varnish5000 said:

If 14.7:1 is chemically correct, why does running richer make more power?

You tell us.

[horsepowerfreek]

Wouldn't the correct ratio be closer to 12.5?
I think it's because u need a few more molecules of oxygen to make sure the fuel is all burned or as near as possible. Any u need a little richer to compensate what condenses on the port runners.
Hope im close, still learning here.
Randy

[Pumaracing]

horsepowerfreek said:

Wouldn't the correct ratio be closer to 12.5?
I think it's because u need a few more molecules of oxygen to make sure the fuel is all burned or as near as possible. Any u need a little richer to compensate what condenses on the port runners.
Hope im close, still learning here.
Randy

You're obviously a very busy man if it's too much time or trouble to type "you" rather than "u". Maybe the miniscule time saving allows you to masturbate more often or buy more stocks and shares. Don't expect any more help if communicating properly is such a burden.

[anonymous-user]

I personally quite like the "girls at a party" theory to explain why engines like to run rich.......... ;-)


(google it)

[AtticusFinch]

Max_Torque said:

"girls at a party" theory to explain why engines like to run rich.......... ;-)


(google it)

No thanks

[stevieturbo]

Max_Torque said:

I personally quite like the "girls at a party" theory to explain why engines like to run rich.......... ;-)


(google it)

Certainly the google result I found was entertaining....but also disappointing.

[varnish5000]

Pumaracing said:

varnish5000 said:

If 14.7:1 is chemically correct, why does running richer make more power?

You tell us.

I always thought that the mixture was made rich to cool the engine and prevent detonation. Running cooler would allow more spark advance which would increase power.

Power is made by burning fuel, the more fuel you can burn the more power you can produce. But just adding more fuel won't make more power because you need to add more oxygen as well.
At 14.7:1 there is just enough oxygen for each fuel molecule to react with. So adding more fuel shouldn't make more power because there is no more oxygen for it to react with.
However adding more fuel (going from 14.7 to 12.6) does make more power, so there must be more oxygen available for the fuel to react with.

What happens is, at high temperature (around 1900*C) carbon dioxide dissociates into carbon monoxide and an oxgyen atom. There's plenty of CO2 and heat available during combustion, so the CO2 breaks down and enough oxygen is liberated to react with the extra fuel in the cylinder, allowing more fuel to be burned than theoretically possible and producing more power.

[Pumaracing]

varnish5000 said:

I always thought that the mixture was made rich to cool the engine and prevent detonation. Running cooler would allow more spark advance which would increase power.

Power is made by burning fuel, the more fuel you can burn the more power you can produce. But just adding more fuel won't make more power because you need to add more oxygen as well.
At 14.7:1 there is just enough oxygen for each fuel molecule to react with. So adding more fuel shouldn't make more power because there is no more oxygen for it to react with.
However adding more fuel (going from 14.7 to 12.6) does make more power, so there must be more oxygen available for the fuel to react with.

What happens is, at high temperature (around 1900*C) carbon dioxide dissociates into carbon monoxide and an oxgyen atom. There's plenty of CO2 and heat available during combustion, so the CO2 breaks down and enough oxygen is liberated to react with the extra fuel in the cylinder, allowing more fuel to be burned than theoretically possible and producing more power.

Jesus (who doesn't exist btw) wept. What utter gibberish. I thought you were doing an engineering degree? What the hell are your lecturers teaching you? There is no oxygen in fuel molecules. There are only carbon / hydrogen molecules. The oxygen only comes from the air. You can't create extra oxygen molecules by turning CO2 back into CO + O. Alternatively if you are suggesting that some oxygen molecules burn twice then the energy of dissociation to turn CO2 back into CO + O would exceed the energy released in the original combination.

Richer mixtures than stoichiometric give more power for one very simple reason - because combustion is always incomplete. At stoichiometric not every air molecule finds a fuel molecule to combust with in the limited time available.

That's why at stoichiometric there's always free oxygen in the exhaust gases which the lambda sensors react to.

The better the mixture distribution and the smaller and more homogenous the fuel droplets are the more likely they are to burn cleanly. That's why wet flow testing during cylinder head development which leads to better fuel droplet distribution gives more power because more of the fuel burns. That means you can run leaner mixtures than 12.6 for best power and in highly optimised wet flow regimes you can get as low as 13.7 if I understand current theory correctly.

If you could make every fuel molecule burn completely then maximum power would come at 14.7 A/F ratio but that's never going to happen in a real engine.

[Pumaracing]

varnish5000 said:

I always thought that the mixture was made rich to cool the engine and prevent detonation. Running cooler would allow more spark advance which would increase power.

BTW - more ignition advance then the engine ideally wants NEVER helps power. In fact an ideal engine would want zero ignition advance so all the fuel burns instantaneously at TDC which would of course blow it to hell but that's by the by. The best measure of how well a chamber burns is how little ignition advance it requires and the less the better. Most 2v engines require more than 30 degrees advance at peak torque rpm whereas most 4v engines require less than 30 degrees which is part of why they produce more power. Much of the aim of cylinder head modification is to produce chamber shapes that require less ignition advance, burn quicker and produce more power from the same air and fuel.