What's the right fuel for forced-induction cars?

Turbocharged and supercharged cars, just like those running natural aspiration, require gasoline. But those forced-induction engines need to be fed the right kind of gasoline.

“Whenever you talk about any kind of turbocharging, supercharging,” explains, Zachary J. Santner, senior quality specialist at Sunoco, “octane is key.”

High-octane fuels fight preignition in high-compression cars, and the same holds true in forced-induction cars. How much octane for your particular application? As usual, the owner’s manual should contain the answer–assuming a stock setup.

Running more boost than stock? Then look at more octane. Sunoco has brought back its Ultra 94 to select markets, while the company’s entire line of high-octane race fuels is available by delivery via mail order and at select brick-and-mortar outlets.

But how do today’s ethanol-enriched fuels play into all this, especially since they weren’t offered when many of our favorite cars hit the showroom floor?

“It really helps a lot,” Santner says of the ethanol. “As ethanol evaporates, it takes a lot of heat. That’s why a lot of people love E85.”

Ethanol cools thanks to a property called the heat of vaporization–also known as enthalpy of vaporization. “When things evaporate,” Santner explains, “they actually absorb heat from the surroundings. All liquids have an enthalpy of vaporization. For gasoline, it’s about 150 btu per pound. For ethanol, that figure climbs to 360 btu.”

To experience this effect of ethanol firsthand, simply apply some to your skin. As it evaporates, you’ll feel a cooling sensation. Think of that cooling as a chemical intercooler of sorts.

Another benefit: That ethanol also provides more oxygen–about 34% oxygen by weight–which can, in turn, make more power.

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Comments

rdstr New Reader
11/21/22 11:24 a.m.

For forced induction cars that sit E85 can cause more problems over time

wspohn SuperDork
11/21/22 1:11 p.m.

I run 94 octane in an engine with 25 psi of boost. Gasohol not recommended.

frenchyd MegaDork
11/30/22 3:54 p.m.

In reply to The Staff of Motorsport Marketing :

Indy cars ran up to 85PSI ( generating 1200 hp) way back in the 1970's on 100% alcohol. Without intercoolers.
Don't store the alcohol in the motor. Drain the system like sprint cars, Indy car, Drag racers, etc do.
Plus alcohol is a whole lot cheaper than gasoline. Engines running alcohol also run cooler and cleaner Than those running Gasoline.

frenchyd MegaDork
11/30/22 4:06 p.m.

wspohn said:
I run 94 octane in an engine with 25 psi of boost. Gasohol not recommended.

While that may be true, E85 can make more horsepower than 94 octane gasoline does. Doesn't leave deposits on the back of intake valves like gasoline does, Doesn't need the rings opened up like gasoline does, Runs cooler than gasoline does, Is cheaper than 94 octane

wspohn SuperDork
12/1/22 10:15 a.m.

frenchyd said:
wspohn said:
I run 94 octane in an engine with 25 psi of boost. Gasohol not recommended.

While that may be true, E85 can make more horsepower than 94 octane gasoline does. Doesn't leave deposits on the back of intake valves like gasoline does, Doesn't need the rings opened up like gasoline does, Runs cooler than gasoline does, Is cheaper than 94 octane

Only one problem with that - the US has thousands of E85 stations - all of Canada has only four. Plus I would need a switchable tune to be able to run it.

frenchyd MegaDork
12/2/22 12:15 p.m.

In reply to wspohn :

Here in America a lot of cars come with a $99 option called flex fuel. Pull up to any gasoline pump and put any fuel in. It quickly senses the alcohol % and adjusts for it.
Since E85 is as much as $1 a gallon cheaper it's easy to save money. Yes you can get a little worse fuel mileage. ( my truck it typically works out to be 2 mpg less) but when you calculate the dollars saved versus the lower fuel mileage I still save over $20 per tank full while the lower mpg costs me $10. I wind up with $10 still in my pocket.
It's not free though. The added power has to be felt to believe. Your tires wear out faster if you don't feather foot it.
Since I put so many miles on the truck I need fuel every couple of weeks. But if I parked it for more than a month I'd either add stabil or top it off with E10.