Went to Uberdata from Hack. My experience/thoughts.
05-11-2004, 08:56 PM
#11
1.0 BAR
Thread Starter
Join Date: Jun 2003
Posts: 313
Re:Went to Uberdata from Hack. My experience/thoughts.
ohh alright sounds good. So that extra fuel would actually smother the flame if Im detonating. Correct? So the slightly rich situation would be the extra safegaurd.
Thanks again for the advice!!
Thanks again for the advice!!
05-12-2004, 11:28 AM
#13
1.0 BAR
Join Date: Apr 2003
Posts: 288
Re:Went to Uberdata from Hack. My experience/thoughts.
Leed hit the nail on the head.
COOLING.
The reason lower AFRs are safer is that fuel acts as a coolant in the combustion chamber. The heat of vaporization (liquid gas droplets turning into vapor) cools the combustion mixtures.
This is also part of the reason why water injection works well. Boiling the liquid water takes heat out of the combustion mixture. Water has a VERY high heat of vaporization compared to gasloine, which helps explain why it is so effective. Beyond the cooling effect from vaporization, water vapor acts as a buffer to slow down the rate of reaction. I went into this a little bit in the first TE training class's advanced topics...
On a molecular level, detonation occurs when a gasoline (hexane, heptane, benzene, etc. etc. etc.) molecule bumps into an oxygen molecule with enough kinetic energy (heat) to overcome the activation energy of combustion (amount of energy required to overcome molecular repulsion forces and have a forward moving reaction).
Cooling the intake charge serves to curb detonation by decreasing the amount of kinetic energy in the combustion mixture, leading to fewer molecules having the required energy to detonate.
Liquid water in the combustion chamber being heated to its boiling point (from 70C to 100C lets say) serves to curb detonation by cooling the combustion mixture by an amount equal to the mass of water present times its specific heat times the temperature difference between the temperature of water entering the chamber and its boiling point. Because the temperature difference plays a role, this explains why colder water works better for water injection.
Liquid water heated to 100C in the combustion chamber boiling into water vapor at 100C serves to control detonation by cooling the combustion mixture by an amount equal to the mass of water present times the heat of vaporization for water.
Water vapor present in the combustion chamber also acts as a buffer on a molecular level, helping prevent detonation. If you have a measurable portion of water present in the chamber, a fuel molecule with high kinetic energy has a chance of hitting a water molecule (and bouncing away) rather than hitting an oxygen molecule with sufficient force to start a combustion (detonation) reaction.
COOLING.
The reason lower AFRs are safer is that fuel acts as a coolant in the combustion chamber. The heat of vaporization (liquid gas droplets turning into vapor) cools the combustion mixtures.
This is also part of the reason why water injection works well. Boiling the liquid water takes heat out of the combustion mixture. Water has a VERY high heat of vaporization compared to gasloine, which helps explain why it is so effective. Beyond the cooling effect from vaporization, water vapor acts as a buffer to slow down the rate of reaction. I went into this a little bit in the first TE training class's advanced topics...
On a molecular level, detonation occurs when a gasoline (hexane, heptane, benzene, etc. etc. etc.) molecule bumps into an oxygen molecule with enough kinetic energy (heat) to overcome the activation energy of combustion (amount of energy required to overcome molecular repulsion forces and have a forward moving reaction).
Cooling the intake charge serves to curb detonation by decreasing the amount of kinetic energy in the combustion mixture, leading to fewer molecules having the required energy to detonate.
Liquid water in the combustion chamber being heated to its boiling point (from 70C to 100C lets say) serves to curb detonation by cooling the combustion mixture by an amount equal to the mass of water present times its specific heat times the temperature difference between the temperature of water entering the chamber and its boiling point. Because the temperature difference plays a role, this explains why colder water works better for water injection.
Liquid water heated to 100C in the combustion chamber boiling into water vapor at 100C serves to control detonation by cooling the combustion mixture by an amount equal to the mass of water present times the heat of vaporization for water.
Water vapor present in the combustion chamber also acts as a buffer on a molecular level, helping prevent detonation. If you have a measurable portion of water present in the chamber, a fuel molecule with high kinetic energy has a chance of hitting a water molecule (and bouncing away) rather than hitting an oxygen molecule with sufficient force to start a combustion (detonation) reaction.
05-12-2004, 12:23 PM
#14
3.0 BAR
Join Date: Jul 2003
Posts: 6,449
Re:Went to Uberdata from Hack. My experience/thoughts.
From Timing on the AFC Hack to water injection 101 and its affect on cooling the combustion chambers...only you buddy!
My $.02...tuning is a process, like Blundy stated. Nail down your AFRs on a semi conservative timing map, then play with your timing. Go back and recheck fuel.
Timing is most effectively 'tuned' on a dyno. Basically its much easier to hold at static load points and change timing on the fly...measuring the amount of change in Torque at the same time. You will either hit a point where power no longer increases as you increase timing or EGTs will get hot enough to melt pistons or you will hear knock. Generally advance until you hit peak TQ and then back off a degree or two for safety (or leave it there if you hear no knock and the risks are acceptable to you). Do this to every area of your timing maps and you are golden. The truly best way to tune timing for optimal performance.
My $.02...tuning is a process, like Blundy stated. Nail down your AFRs on a semi conservative timing map, then play with your timing. Go back and recheck fuel.
Timing is most effectively 'tuned' on a dyno. Basically its much easier to hold at static load points and change timing on the fly...measuring the amount of change in Torque at the same time. You will either hit a point where power no longer increases as you increase timing or EGTs will get hot enough to melt pistons or you will hear knock. Generally advance until you hit peak TQ and then back off a degree or two for safety (or leave it there if you hear no knock and the risks are acceptable to you). Do this to every area of your timing maps and you are golden. The truly best way to tune timing for optimal performance.
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