Anyone with a Dodge truck experience?

[CAP1]

interesting. not doubting you, but could CAP verify this?

 i'm honestly not sure on that. i've never checked it, or measured combustion temps....it might be something interesting to check though.

[MaSonZ]

i'm honestly not sure on that. i've never checked it, or measured combustion temps....it might be something interesting to check though.

I'm sure your more adequetly tooled to do this then I....hint hint.

[CAP1]

interesting. not doubting you, but could CAP verify this?

 i was just thinking more about this as i was cleaning up.

 higher octane has a higher resistance to detonation, and pre-ignition.
 detonation is generally when there is excessive heat inside the combustion chamber, which causes pressures to be too high,  which ignites the fuel mixture somewhere other than at the spark plug, and often times before the plug fires.
 when this happens, you now have 2 flame fronts traveling at each other. when they meet, that's when you get detonation....and it can be pretty dam damaging to an engine.

 pre-ignition is generally when a spot in the chamber gets too hot, and ignites the a/f mixture before the plug does. this can/will actually cause detonation(when the flame fronts meet)
 

 with todays computer controls, this isn't very common any more. the worst thing to watch for, is pre-ignition, as using crappy gas, can and will leave carbon deposits in the chamber, and that is where you get hot spots from.

 racing engines are totally different.

 i need to think more to remember octane ratings meanings......part of it is the resistance to combustion, and detonation.......
 
 

 EDIT.....

detonation is VERY VERY bad. i've seen drag race engines turn into hand grenades from detonation.

[MaSonZ]

i was just thinking more about this as i was cleaning up.

 higher octane has a higher resistance to detonation, and pre-ignition.
 detonation is generally when there is excessive heat inside the combustion chamber, which causes pressures to be too high,  which ignites the fuel mixture somewhere other than at the spark plug, and often times before the plug fires.
 when this happens, you now have 2 flame fronts traveling at each other. when they meet, that's when you get detonation....and it can be pretty dam damaging to an engine.

 pre-ignition is generally when a spot in the chamber gets too hot, and ignites the a/f mixture before the plug does. this can/will actually cause detonation(when the flame fronts meet)
 

 with todays computer controls, this isn't very common any more. the worst thing to watch for, is pre-ignition, as using crappy gas, can and will leave carbon deposits in the chamber, and that is where you get hot spots from.

 racing engines are totally different.

 i need to think more to remember octane ratings meanings......part of it is the resistance to combustion, and detonation.......
 
 

 EDIT.....

detonation is VERY VERY bad. i've seen drag race engines turn into hand grenades from detonation.

scary.

[CAP1]

scary.

 with them, in particular, the top fuelers are making 8,000hp out of just over 500ci. those engines are running right on the edge to begin with. let her go a little lean, and KABLOOEY!!.
 
 cvh could more than likely comment on this too. he's probably one of the smartest racers i've seen post here. well.....'cept he likes chevys, but none of us are perfect. 

[MaSonZ]

with them, in particular, the top fuelers are making 8,000hp out of just over 500ci. those engines are running right on the edge to begin with. let her go a little lean, and KABLOOEY!!.
 
 cvh could more than likely comment on this too. he's probably one of the smartest racers i've seen post here. well.....'cept he likes chevys, but none of us are perfect. 

in top fuel drag cvars, is it better to have them burn too rich then just right, or could that be just as bad as just a little lean?

[Babalonian]

when i have my part time helper here....he's a smoker....i don't let him smoke in the shop. it's got nothing to do with anything, except that that is one of my rules. i don't like the smell of it, and i'm not gonna have a customer complain about it. 

The fact you (or should I say your insurance) let your customers get close enough to the bays to smell them nevermind get a good look at what you're doing to their car inside them would draw some very long stares from the mechanics out here.

[CAP1]

in top fuel drag cvars, is it better to have them burn too rich then just right, or could that be just as bad as just a little lean?

 i'm not as "up" on them as i probably should be....but if i had to take a guess, i'd say too rich is better than too lean.

 when you lean out, your combustion temp shoots through the roof. this helps to cause pre-ignition, and/or detonation.

[CAP1]

The fact you (or should I say your insurance) let your customers get close enough to the bays to smell them nevermind get a good look at what you're doing to their car inside them would draw some very long stares from the mechanics out here.

 my shop's set up where they can stand by a window at the first bay. they can see most of what goes on out there.

 that, and the smell permeates pretty much everything.

[Babalonian]

 

my shop's set up where they can stand by a window at the first bay. they can see most of what goes on out there.

 that, and the smell permeates pretty much everything.

True.


About the octane discussion, some pondering here on my part, wouldn't a higher resistance to detonating and pre-ignition imply that the ignition point/temperature of the high-octane fuel is higher, thus requiring a hotter ignition source than standard or low octanes would require (now obviously and thanfuly, car designers haven't gotten stupid enough yet to design an ignition system that only generates the bare minimum amount of heat/energy required to ignite nothing higher than say 87 octane)?  This hotter ignition source that is required, over say what would be required for the lesser octane fuel grades, wouldn't that qualify as higher-octane engines running hotter as the ignition source is hotter than the colder ignition sources for the lower-octane fuel engines?

[Rash]

Wonder why you need lots of spark to ignite a high compression engine?  A diesel will auto ignite with 15 octane?  ...edit...with no spark? 

[CAP1]

Wonder why you need lots of spark to ignite a high compression engine?  A diesel will auto ignite with 15 octane?  ...edit...with no spark? 

 a diesel ignites due to the pressure and temperature. as you compress the a/f mixture, you also heat it up. whereas a gas engine may run 11-1 compression ratio, the diesels may well be in the ballpark of 20-1.
 this is also a help for the gasoline engine. as you compress the a/f in a gas engine, it also heats up as it is compressed, but not enough to self ignite.
 you need the so much amperage in the spark plugs, because you need to make that spark plug ignite, and have the spark jump a gap that is anywhere from .035 to .080 of an inch. that is a LOT considering the pressures in the combustion chamber,

[CAP1]

True.


About the octane discussion, some pondering here on my part, wouldn't a higher resistance to detonating and pre-ignition imply that the ignition point/temperature of the high-octane fuel is higher, thus requiring a hotter ignition source than standard or low octanes would require (now obviously and thanfuly, car designers haven't gotten stupid enough yet to design an ignition system that only generates the bare minimum amount of heat/energy required to ignite nothing higher than say 87 octane)?  This hotter ignition source that is required, over say what would be required for the lesser octane fuel grades, wouldn't that qualify as higher-octane engines running hotter as the ignition source is hotter than the colder ignition sources for the lower-octane fuel engines?

 i would think the same as you're saying. it'll take more spark, and more pressure to burn, generally you'll get a more complete burn, and in theory, these all should increase the combustion temperature.

 but here's a couple of other things to consider.
1)compression ratio and compression pressure are different.
2)most modern engines use the egr system to limit the combustion temperature to 2500F or below, in order to control NOX.

[Rash]

Why would you need a .080 of an inch of gap on the plugs?

[CAP1]

Why would you need a .080 of an inch of gap on the plugs?

gm used to use that gap on their HEI ignition systems. most run from .045 to .054, including ford on their eec5 ignition system. some aisian imports still only use .030 to .040.

  the theory was the bigger the gap, the more spark exposed to the a/f mixture, creating better combustion.

 once again, with todays COP systems being able to individually control each cylinder, it's much easier, and much more effecient. i had talked to a ford factory tech, who explained that when the eec5(i forget what they referred to the ignition system itself as) was installed, it increased power nearly 35%, and mileage nearly 25%. that qualifies as a win/win.