Cooler intake manifold
On the issue of how cold gasoline can be before it becomes frozen or even a slushy mix, I don’t know. Also, more food for thought, how dense can fuel get from chilling? A smart *** says, to the point where it starts to freeze, but is it any denser where a measurable gain is seen? AKA - Is it worth the effort?
If the
"it" refers not to density, but to the temperature, then it seems to me, that for the question of; "Is it worth the effort?",
the answer might be yes; but only if it solves a percolation issue.
But I think we all know that getting an amount of fuel into the engine, commensurate with the mass of air it is getting, is not a problem; and I know that is not what you meant.
To the OP:
But consider this, when the gasoline changes state from a liquid to a gas, in the intake tract, it takes huge amounts of heat to do that, so it is literally sucking the heat out of the adjacent materials........ including the air that is present there. The moving air itself can be cooled by it.
In other words; say you are idling around town at some low rpm, and your cooling system has stabilized at 180. The headers are running at 450* in the first 6 inches. The rad is running at or near 180, and so is the air coming thru it. All that air is mixing around and by the time that air gets to the airhorn, it could be at say 250*. As soon as it enters the carb, the temp starts dropping. The first drop occurs in the boosters and venturies. Then it gets into the 180* plenum, where the gas picks up heat to vaporize. This pulls down the temp of the whole AFR mixture. Then it scoots off towards the chambers still pulling heat out of the adjacent materials. At some point, the fuel is fully vaporized and air starts to pull heat out of the runners and begins warming up again. Then it gets into the ports where the cast iron says; not here you won't! and the adjacent water jackets put a lil heat back into the charge. Finally the intake valve opens and the headers "yank" the mixture into the chamber. So from ambient temp coming into the radiator to into the combustion chamber, the inlet air density has been riding a roller coaster of temperature and density changes.
>Does your engine, at this time, care about air density?
At this time, No it does not; you will just be driving with the throttles ever so slightly further open, and your mixture screws adjusted accordingly.
But say you step on the gas.
Well firstly, say you have an auto-trans and the typical 3.23 gears, and your speed is 32 mph. You are in "drive", and the rpm is 1300;
So you step harder and she kicks down into Second. The rpm rises to 2200.
>Does your engine, at this time, care about air density?
No it does not.
So you step harder and she kicks down into First. The rpm rises to 3600, but you are not yet floored.
>Does your engine, at this time, care about air density?
No it does not.
Your engine will not care about air density until the engine asks for more cfm, than the carb can supply, or the engine is pulling all it can.
So you finally floor it, from 32 mph , in First gear, doing 3600rpm. With the right cam, you are now at close to max efficiency, so pulling 420 cfm .
>Does your engine, at this time, care about air density?
Not much, and only if you have a 420 cfm carburator
So you wait. By 4500/41mph, the engine is losing efficiency. The air flow requirement might be 480 cfm. You have a 650 on it.
>Does your engine, at this time, care about air density?
Yes but only if there is a car in the next lane, that is gaining on you..
By this time, the engine is pulling say 480 cfm; that is all she can do in the present state of tune, so the more oxygen molecules in those cfms the better.
By 5400/49mph still in First gear, your airflow requirement might be 532 cfm.
You have a 650 on it.
>Does your engine, at this time, care about air density?
I think by this time, yes. The coolant temp is rising. The exhaust temp is skyrocketing. The IAT is climbing. The fan together with road speed, is jamming hot air under the hood , and so......
Time to shift and the Rs drop to 3200/3300; oh my.
Now if I remember rightly, from my snowmobile tuning days, a decrease in ambient temp of 20* was one jet change richer at WOT, to match the increased air density.
So if you feed your carb ambient air at say 85*, instead of 250*, that is a temp difference of 165*, which is 8 jetsizes ....... in theory, to a snowmobile.
In practice, my carb wanted only one jetsize all around, at WOT.
Back to the quote;
For me; sorta;
I now have a big hole in my one-time pristine 1968 Barracuda hood, and
I now have no hot-fuel issues running 87E10 on an Airgap intake, and
The 295s spin occasionally to 80 mph instead of 60 ............. so that's something ....... I guess,lol.
But she did go 93 in the Eighth with this set-up. Jus saying. No before and after..... lol.
