C16 or Q16? VP Racing Fuels Explains the Tuning Differences
Racers often fail to take into account how critical is the choice of racing fuel and how the right blend will benefit specific applications. With all other factors equal, an oxygenated fuel like VP Racing Fuels‘ Q16 variant can and will make more power in a racing application; however, there are important differences to note, especially if you’ve been working with a traditional fuel like the company’s C16 dino-juice.
Since an oxygenated fuel has more oxygen formulated into the mixture, there are suggested tuning parameters when it comes to setting up the engine and drivetrain to make use of those extra O2 molecules.
Performance gains will vary depending on combination, as power-adder applications will make much greater use of the extra oxygen – but only if the combination has been optimized.
“In a perfect world, what you want from a race fuel is for it to stay a liquid all the way through the engine until it gets to the back of the intake valve. And then as soon as that intake valve opens, lets the fuel into the combustion chamber and closes, it needs to immediately turn into a vapor. You can’t burn liquid – the fuel needs to be a vapor to burn,” explains VP’s Jason Rueckert. “A lot of fuels have issues with that – there’s still wasted fuel that doesn’t turn into vapor.”
Racers who have been working with VP’s C16 or another race fuel might read that and think, “My fuel is working just fine – last week I set a new personal best with it at my home track!” That’s certainly possible, but if there’s a chance to pick up more performance, why wouldn’t you look into it?
Rueckert continues, “Q16 is about the most perfect vaporizing fuel ever – you’re burning everything. There aren’t a lot of leftovers once you start the combustion process. It also has the added effect of equalizing out the cylinders. On many cars, your front and rear cylinders won’t have the same burn rate as the middle cylinders, and Q16 will help that also.”
That’s not to discount any of the other fuels VP has created over the years.
“C16 is still a killer fuel. For example, on a typical non-intercooled blow-through carburetor supercharged combination, you’ll see inlet temps around 200 degrees or more. Since C16 doesn’t turn to a vapor very easily, it could take that high heat and not have an issue. But once guys started intercooling them and getting the temperatures down to where the carburetor was cold, they would struggle to get C16 to light off. Q16, on the other hand, works much better with cold inlet temperatures. The colder it is, the better it works,” says Reuckert. “You can run inlet temperatures at 65 degrees all the way down the track without a problem, and that helps to make a lot of power.”
“It’s really not as complicated to switch over to Q16 as it might seem,” says noted tuner Jason Lee of PTP Racing. “Every car and combination is different, but I see typically a 5-to-7 percent fuel increase needed in the map. The Q16 seems to burn more quickly, which will also help to pick up some power. Now, I have seen some cars pick up a bunch from switching, and I have had other cars not pick up much at all; just a couple of hundredths here and there in the eighth-mile.
“I think there’s power to be gained from running it, but it’s also not going to pick you up 100 horsepower,” Lee continues. “When I first put Q16 onto my car, it did absolutely nothing back-to-back, but I’ve got way more passes on it now. Over time, I was able to see differences in what the tuneup wanted and make appropriate changes. A blower car on C16 will black-smoke all the way down the track and appears to be very fat to the eye, and when you put Q16 into it and modify the tune appropriately, all of that smoke is gone.”
In regards to the rumors of necessary equipment changes necessary to run one fuel versus the other, Lee says that he didn’t change a thing other than the tuneup. On the flip side, he still spends plenty of time working with C16 with a number of his customers.
“I do like C16 a whole lot – if someone calls me with a brand new combination, I like to use C16 because it’s very forgiving and has a large tuning window,” says Lee.
Another factor to note is injector duty cycles with the use of Q16.
“A car on C16 might be using 160-pound injectors, and when you switch to Q16 you have to add more fuel to it, which might cause the injector to go static, and then the customer slows down. You have to be prepared and understand what it does to the tuneup because it can do things that effectively work against you,” Lee explains.
Injector duty cycle and overall fuel maps with your EFI program also need to be taken into account thanks to the increased fuel volume Q16 requires to work properly.
“There’s a transition period for a lot of combinations out there that have 160 pound injectors and a pair of electric fuel pumps that are doing things they shouldn’t necessarily be doing – those are right on the edge in quarter-mile racing,” says Lee. “When you switch to Q16, that can magnify the problem because you have to raise the injector duty cycle; you’ll need to switch to a larger injector and make other appropriate tuning changes because the fuel demand is much greater. You need to make sure that you actually have the appropriate equipment to be able to take advantage of the fuel.”
“You have to have enough fuel system capacity,” concurs another well-known tuner, Chris Tuten. “When I first changed over on my own car, I was running 160-pound injectors and was at the limit of what my parts could handle. I pushed the limits a little bit far by running the injector duty cycle too high and hurt the engine because of it. The fuel system could barely keep up with the amount of boost we were making, and I ended up having to switch to a 212-pound injector as a result. If you’re already at 85 percent duty cycle, you might not want to try Q16 because you’ll run out of time to open and close the injector once you get up around 90 percent duty cycle.”
In my opinion, the tuning window shrinks up a little bit with Q16, just because the fuel burns so much more quickly.–Jason Lee
In his day-to-day gig, Tuten runs the dyno at The Muffler Shop of Columbia, South Carolina. There are a number of performance gains that Tuten has discovered using Q16.
“Naturally aspirated, I’ve seen 14 horsepower on my chassis dyno back-to-back from one fuel to the other. And on a turbocharged combination, it does a lot of things, especially helping with spool time. One second quicker spool time in a turbo car on the starting line is a big deal – the transmission and converter don’t get so hot and it helps to make the car more consistent,” he explains.
“Because you are using more fuel, it’s going through the engine more quickly, and that helps to suppress detonation,” he adds. “We used to only get a couple of passes before we’d have to change the head gaskets on my car, making 30 pounds of boost, and since we switched to Q16, I can run an easy 25 or 30 passes and never even touch the gaskets. Summertime performance is also greatly enhanced. The car doesn’t slow down nearly as much as when I was using C16 because of the oxygen in Q16. The car does slow down in the heat, but you definitely don’t lose as much performance. Because you can burn more of it, that’s more exhaust energy. And that helps to spool a turbo. My opinion is, if Q16 is allowed in the rules of your class, you need to be running it.”
Rueckert suggests that if running a carburetor, cover the fuel bowl vents so air can’t get into the bowls.
“As Q16 is hygroscopic, like brake fluid, it will tend to suck the moisture from the air and into the fuel and can really gum things up. We usually suggest that people connect the vent tubes with a piece of fuel line to prevent this from happening. It’s also a good idea to drain the carburetor down just to prevent any issues,” says Rueckert.
“The Q16 has provided us with a more consistent combination that is very stable in different temperatures,” says car owner James Lawrence, noting that the fuel’s consistence is helpful racing in California, Las Vegas and other tracks where temperature can be a concern in the summer. “From a bottom line standpoint, we have seen a substantial increase in horsepower. Although we didn’t A-B exactly because we made a few other minor changes, there is absolutely no doubt that the engine has made more horsepower than previously, as witnessed through the duty cycle and injector pulse width. We ran faster down the track and that’s the ultimate indicator.”
Summing up, adding oxygen to the Q16 fuel effectively tricks the engine into thinking it has more displacement.
“Adding oxygen to the fuel, it’s just going to make more power, that’s basic chemistry,” says Rueckert. “In fact, I think if more people were willing to run a magneto ignition in gasoline applications, you’d see guys go even faster than some of these alcohol fuels. That’s why cars make so much power on alcohol these days, because you can shove an absolute ton of fuel into the engine and still make it light off with the mag. If you look, Mark Micke runs a mag on Jason Carter’s Outlaw 10.5 Malibu, and that’s one of the quickest cars out there. If you can light it off with the mag, you can put more compression in it, more boost in it, and go even quicker. You’ve basically got a welding spark lighting off the fuel. Fuel is just one part of the equation, and everything needs to work together.”