Dry Ice in Methanol

Here in Texas it gets very hot in the summer months. Ive often wondered if one were to drop a few cubes of dry ice in your fuel jug if it would drop your fuel temp enough to make a HP difference. Would there be a chemical reaction that would destabilize the methanol? Anybody ever tried this?

 

Why do you want to cool methanol?

 

To make it more dense so that he can get some more power of course. Ever wonder why NHRA has a limit on the temp your fuel can be?

 

Chilling the Methanol

My travels this year working with top-tier NHRA Top Alcohol teams showed how critical fuel temperature was for proper jetting of the blown methanol engine. I saw fuel jugs in freezers, recirculating systems in ice chests to cool the fuel already in the tank, insulating blankets wrapped around the body, and fuel temperature sensors hooked into the data recorder and recorded in the logbook.

Chilling the fuel has 2 effects. The first effect is the change in specific gravity (SG). As the fuel is cooled it gets more dense . . . it weighs more per gallon. Here are some examples for methanol.

methanol @ 50 degF: SG = 0.801, 6.68 lbs/gallon
methanol @ 70 degF: SG = 0.790, 6.59 lbs/gallon
methanol @ 90 degF: SG = 0.780, 6.51 lbs/gallon

As you can see the methanol SG/degF effect is small, 20 degF = about 1% SG. The corresponding value for air is only 5 degF. That is, if you cool the air by 5 degF, the air density increases about 1%. And the colder the fuel injected upstream of the blower, the cooler and more dense the air will be as it enters the rotors. So, the effect of cooling the air is much stronger than the simple chilling effect on the fuel SG.

But wait . . . we all have weather stations mounted on our trailers that measure the density of the ambient air. The barometric pressure, temperature and water grains are all recorded in the logbooks. I wrote a 70+ page book about ambient weather correction that describes all the ways to measure the air and also includes the math used for all these calculations, see www.DragRacingPro.com/Books.html. Isn’t that what matters?

No – not for supercharged engines! You need to calculate the weather conditions at the inlet to the blower rotors, downstream of the injector, to determine the air density. The evaporation of methanol can lower the air temperature at the inlet to the rotors by 40 degF below the ambient temperature. If you chill the fuel you can get a 50+ degF drop . . . down to below freezing (32 degF) in some cases. These blower inlet weather conditions are the only ones to use for determining the fuel-air ratio for supercharged engines, not the “Corrected Altitude” or “Relative Density” of the ambient weather. Why?

All superchargers used in Top Alcohol racing (Roots and Lysholm Screw) are positive displacement pumps. For each revolution they “gulp” a certain volume of air. For example, a 14-71 Roots displaces about 551 cubic inches per revolution, and a PSI “D” rotor right at 422 cubic inches per revolution. In order to determine the lbs of air in each “gulp” we need to know the density (lbs/cubic inch) of the volume of air trapped between the rotors and the case. And the density of this blower inlet air is definitely not the same as the ambient air density we measure back in the pits. Remember, for every 5 degF that the air is cooled, the air density goes up 1%. The evaporation of the chilled methanol is central to this process and makes a huge difference!

Patrick Hale
PHale@DragRacingPro.com

 

Good Info

Attaboy Pat !
Good info, I can just see all the propellers on their "Beanie Hats" going supersonic with that post!


Bob Meyer
Meyer Race Cars / San Diego
2010 Our 45th Anniversary

 

Is there a formula to figure this out?

Dan

 

so..... do you need less fuel in the tune up because the the fuel is more dense ?

 

It's hard to give a simple answer to these questions. Like everthing else in racing it kind of depends . . .

The current NHRA limit for methanol is 50 degF. So as Will Hanna said, if it's 50 degF outside and your fuel is at 50 degF anyway . . . what's the difference? But if it's 95 degF out, the difference between 95 degF and 50 degF methanol is huge! Depending on how your tuneup software works, you might lean it a little for the 50 degF day example (because the methanol is more dense) and richen it some for the 95 degF day with 50 degF fuel case (because the blower inlet air temp will be lowered a lot by the cold fuel).

Before the NHRA 50 degF fuel temp limit I saw methanol as cold as 15 degF being used. So if you would like a little more HP, take Will's advice about the freezer.

Patrick Hale
http://www.DragRacingPro.com/Software.html

 

Cold Fuel

Thanks Will and Patrick. Yall have answered my question about colder fuel. However,Im still curious to the effect dry ice in methanol would have.

Randy

 

As long as it's vented properly (the tank) you shouldn't have any issues. Dry ice doesn't "melt" it instead turns into gas (Co2)....if your rules permit...toss it in there.

Brandon Booher
NHRA TAD #34

 

Instead of dropping it in the fuel and not knowing what will happen (but if you do make sure your friends post it on Utube for us) how about making a small tank welded to the fuel tank to hold the dry ice and transfer the temp between the tank wall??

What effect will this have to any water in the fuel? would it freeze it?

 

Mike has it, I know a nitro (outlaw car) that has a recessed pocket inside the tank that a 6x6x2 chunk of dry ice (in sealed bag) fits snugly into.

 

I was envisioning a hurry up scenario where the dry ice wasn't consumed and blocked the tank outlet. Pretty sure the pumps weren't designed to crunch ice.
Dave Koehler
http://www.koehlerinjection.com

 

I'd give some long pondering thought to using "dry ice" in a fuel tank.

The expansion ratio on phase change from a solid frozen carbon dioxide (dry ice) to gas is 1 to 554 by volume.

Just a safety precaution.

Blessings.........Ron Clevenger

 

"airrated fuel"
or just
BOOM + Utube

 

Utube

Ill be trying this out this weekend. Gonna video it and post on UTUBE. Will measure before and after fuel temps. "HOLD MY BEER WHILE I TRY THIS"

 

I'd think the likelyhood of a chunk blocking the vent and blowing up the tank would be pretty slim but there still is that chance, seems that I've had wierder shit happen.

I wouldnt like it going through my pump though...

 

What if you put the dry ice chunks into something resembling a big stainless steel mesh tea leaf holder (cage), and dropped that into the tank? No errant chunks to block pump inlets or tank outlets, and the dry ice could then do its thing to cool the bulk meth. I don't see any down side, as long as you could get the mixed bulk fuel temp to a "predictable" temperature in a predictable period of time. Might take some trial & terror at first. C02 won't dissolve into the meth and shouldn't screw-up fuel check. I'd think that a bulk fluid temp sensor in the tank would be a good data point to log. Actually kind of a neat idea as opposed to having dedicated fuel cooling hardware. Come to think of it, a person could also use liquid nitrogen or some other cryogen. Hey wait a minute, maybe ue the expanding cryo gas gas to pressurize the fuel tank, to aid fuel delivery.......Oh sorry, I forgot, that's against the rules in most cases

 

Our brains went to the same place.

Might be a little suspicious when in the stage lanes a crewman approaches the fuel tank. He's wearing a protective suit with gas mask and caring something with ice tongs giving off clouds of some mysterious smoke and then..................................

Hmmmm........a boost referenced power valve on the vent might be..............naaaaa!

Blessings...........Ron