Thinking about air and fuel stuff...

[danwjmu]

Ok, thinking about air and fuel a little bit lately.  On the mower board I'm involved with they're talking about using a cool can for a car to cool the fuel (gasoline) down to make it denser and therefore cram more fuel into the mower.  Now my problem with the whole idea of cooling fuel (in cars as well, where cool cans are marketed) is that you'll get droplets instead of mist forming.  Thinking about how fog is formed.. cold air is moving across warm air or moist ground.  Even at low relative temps the water evaporates and moves into the air.  Reverse this.. have cold water and warm air and what do you get?  Nothing.  Well, actually you'll get water being pulled out of the air, like a cold glass in hot summer air forming condensation on the outside.  So heat the intake as well (automakers already do this).  It just seems to me that you would actually want to warm the fuel rather than cooling it so you get a better evaporation and mixing with the air and also using a heated intake would help.  Yet cool cans have been used for year and these mower guys are talking about them like they do something positive.  They're also talking about chilling the intake manis too.  What's going on here?

[brine04]

Not sure what's going on but I have seen a few magazine tests over the years comparing warm and cold fuel. The one that sticks in my mind was a motocross mag. They put the jerry cans in the freezer and all the bikes tested made about an extra hp.

[Joseph Davis]

Turbo cars, which are generally indifferent to atomisation and some in fact like injectors that shoot narrow streams, typically make best power when the gasoline is at ~80 degrees F.

As with everything, your mileage WILL vary.

[speedjunky01]

didnt honda design a gas "vaporizer" back in the 70 when the gov put in the clean air act as an alternative to a cat?

they were able to run the car very very lean on the order of 30:1 or something like that. . .

dont recall the details . .  . googling now

edit:

its old but turo d and crx front its WIN in all ways

http://videos.streetfire.net/video/4df10546-e7e7-4b43-84fe-993600d36841.htm

[Joseph Davis]

didnt honda design a gas "vaporizer" back in the 70 when the gov put in the clean air act as an alternative to a cat?

they were able to run the car very very lean on the order of 30:1 or something like that. . .

dont recall the details . .  . googling now

It wasn't that lean.

Search for CVCC, it was a stratified charge method.

[sewell94]

Chilling the fuel works, i've seen it done alot on on v8 stuff.

[Adam Hopkins]

But isnt dropping the temp of the fuel have more of an effect on air temperature than density of fuel? Am I correct in thinking this?

I mean if you need more fuel then put in a bigger jet or give it some more injector duty.

I wouldnt rely on the temp of the fuel to control how much is fuel is entering the cylinder.

[Joseph Davis]

Chilling the fuel works, i've seen it done alot on on v8 stuff.

Hendren found that 80-85 degrees is where VP blue (118?) makes best power on the turbo SB2s he builds.  Crazy, wise old man, posts on speedtalk.

[Teg2boo]

I thought that you want the fuel to be cooler because warmer fuel is easier to vaporise and you don't want gas vapor in the combustion chamber since it is easier to ignite aka detonation. I thought want the gas drop to be as small as possible without reaching the vapor state.

I don't know how I got this idea tho lol

[Conceptz-X]

Fuel does not burn as a liquid.  There is far more to the equasion. 

They also sell intake gaskets with a screen in them to break up fuel droplets for carbureted motors.   In my opinion they will affect the ram charging effect in the V engine style manifolds. 

[patsmx5]

I wish I could wrap my head around the mechanics of what is happening to the air and fuel as it goes from carb/injectors through the IM into the chamber and then right before ignition.

Read up on it. The info is online. If I find a good link I'll post it.

[Conceptz-X]

My recipe:   Try to atomize what you can at a low temp, have a swirl or tumble inducing intake design, more quench the better, rod ratio around 1.6 for up to 6500 rpm 1.8 to 9k to  give a lower piston dwell time at TDC for the piston and properly use the quench.

[Conceptz-X]

yea, thats why I suggested a different ratio for a different max rpm   

It also affects the acceleration/decelleration of the piston from TDC and BDC  if the rate is too high the wrist pin comes under additional stress

Longer rod dwells more at TDC and BDC  it reduces pin stress and piston rock therefore increasing ring seal

[Conceptz-X]

most current cup motors are running in the 1.9-2.0 rod ratio

bore is around 4.125 with a short stroke  lots of quench  piston has a dish to match the head quench area

[Conceptz-X]

also offset wrist pins may be an option with a low rod ratio engine to reduce piston rock