Just took a break from browsing the most recent Summit Racing catalog for some ideas, and I stumbled across something that I had forgotten about - the benefit of keeping fuel temps down.

We obviously have put a fair amount of focus on cooler air like at the intake or IC areas - the colder the better, for the most part. Given that the fuel is the other portion of the combution equation, cooling it, at least in some applications, is beneficial.

Something tells me that if there was anything to be had here, it would have been done already, so I mostly ask out of curiousity. What is the ideal temperature for fuel? At what point should cooling be considered? Or does the air temp dictate that figure? Anyone know what fuel temps we experience? Where is that measured at, typically? Are there any adverse impacts of cooling the air for combustion substantially, while not doing so to the fuel?

Ok, back to page 52

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2003 IB MCS

 

Cooling fuel used to be popular in the days of carburetors. It kept the fuel from boiling and vapor locking in the relatively low pressure fuel lines, and in the ambient pressure of the float bowls. "Cool cans" were used which were basically a coil of copper or aluminum fuel line inside an insulated container, much like a picnic cooler. This was filled with ice and water to cool the fuel. These days, with the fuel under high pressure throughout the fuel path there is little worry of the fuel vaporizing in the lines. The fuel may be a bit denser at colder temps, but this difference would be impossible to see in horsepower output.

The vaporization of the fuel as it leaves the injectors does lower the air charge temp because of the phase change. You want the fuel to vaporize as much as possible and homogenize the fuel/air charge for the greatest combustion efficiency.

Much more benefit can be gained by cooling the air charge as much as possible to create the most dense, oxygen bearing charge as possible. Liquid does not change it's density as much as gases do with rising temps, unless the fluids begin to boil.

 

Greatbear, much appreciated. That makes a lot of scense. Your knowledge transfer allows me to hit the sack a wiser man. Thank you.

 

Another thing to consider is that the MINI, unlike most fuel-injected engines, uses a returnless fuel system. In a VW 1.8T, for example, fuel is constantly being circulated from the tank through the pump, through the filter, through the fuel rail, out past the fuel pressure regulator, and back into the tank. In the MINI, once the fuel enters the fuel rail, it has nowhere to go but through the injectors and into the engine. Because of this, fuel temps are lower than in a return system.

 

I was not aware of that difference. Good stuff. From what Greatbear shared above, the benefits of going cooler, given our application, is not that significant. And with the MINI using a returnless fuel delivery system, even less of a need... A 40 buck fuel radiator with claimed 80 degree temp drops is just not so appealing to us then.