Is Running A ProCharger On A Top Fuel Nitromethane Engine Possible?

Is Running A ProCharger On A Top Fuel Nitromethane Engine Possible?

When it comes to the pinnacle of drag racing, there is one thing that separates the top two classes from the rest (Top Fuel Dragster and Funny Car), and it’s right in the name of those classes — the fuel. Nitromethane is the fuel of legends. Not only because it has powered some of the quickest and fastest humans on the planet (legends in and of themselves), but because of its dangerous and storied history, which is an article all its own. One thing that might surprise you, is that over the past sixty years, the engine combinations powering these insanely fast vehicles have remained largely unchanged. However, the team at ProCharger is exploring the opportunity to change.

Now, let’s start this off with the current reality up front: this article is largely a “what if” look at allowing a new power-adder in a pair of classes steeped in history. However, the team at ProCharger has put more than just a few hours of brainstorming and back-of-napkin calculations into the idea. A centrifugally supercharged Top Fuel entry is something they genuinely want to see happen. After reading this article, hopefully, you’ll agree that it certainly seems like a feasible idea.

The ProCharger F-4X-series of centrifugal superchargers are able to move enough air to match, if not exceed the airflow needs of a current nitro Hemi engine.

“This is as much of an engineering exercise as anything,” says Kyle Fickler, ProCharger’s Director of Business Development. “We have done a lot of work on the engineering and airflow side of it. We’ve had discussions with some NHRA parties and Nitro Chaos parties about their interest in the concept, and then there are the mad scientists, who are really interested in it.”

A ProCharger on a Top Fuel car isn’t as out-in-left-field of an idea as you might be thinking, as ProCharger has record-holding experience in Nitro classes already, explains Walt Sipp, Director of Service and Motorsports at ProCharger. “It’s not exactly the same, but we’ve done some work with mechanical injection on the Top Fuel Harley side,” Sipp says. “There are a couple of guys who run a ProCharger in the Nitro Harley world, and no one has been quicker than a ProCharger. So, we have had some success with Nitromethane, holding the record in NHRA Top Fuel Harley and the overall record in the Top Fuel Harley world.”

Can A ProCharger Keep Up In Top Fuel?

The first real question we had when discussing all of this with the ProCharger team was simple. Does a ProCharger flow enough air to make the power needed in Top Fuel classes? ProCharger’s Director of Engineering, Cliff Hall, replied with a confident, “Yes.”

“We have somewhere in the neighborhood of 5,200 cubic feet per minute of airflow from the larger F-4s — mainly the 145mm variant — based on our calculations,” explains Hall. “From my understanding, talking to some of the nitro teams, we’re right there, both in airflow and boost pressure. They are convinced that the difference is just on the fuel side. We shouldn’t have any issues with the airflow requirements whatsoever.”

This is what an F-4-powered Funny Car could look like. It will take a little fitting, but is definitely possible.

Now, you might be wondering, if the F-4s are making in the neighborhood of 4,000 horsepower in ProMod trim, how would they flow enough air to make the 11,000 horsepower or so it’s said that Top Fuel engines make? Well, that’s the beauty (and danger) of Nitromethane… it brings some of its own oxygen with it and is a power adder in and of itself. At the end of the day, the engine doesn’t care where the air is coming from, only that it’s getting enough of it, and in the correct proportion to the fuel. There are no inherent differences, as far as the engine or fuel are concerned, in how that 5,200 cfm of air is delivered into the cylinders.

A Centrifugal Powerband

The next question we had was, in our experience, the beauty of a centrifugal supercharger is the smooth, linear powerband. By contrast, a Top Fuel car ramps up quickly and the clutch does all the slipping. “If you think about the use case, on the street side, the 10-speed automatic transmission keeps everything in a very narrow window of operation as well,” says Sipp.

“As long as you keep the load there and engine RPM up [in a fuel car], you’ll keep the boost up, and you’ll have the efficiency of the centrifugal over the Roots. The centrifugal supercharger can match engine RPM even with today’s quickest converters, so it will be able to do everything the Roots does, boost-wise, in a Top Fuel application.”

“When we first started the Pro Mod experiment, there was some question as to whether or not it could perform because of the RPM situation. Well, we’ve proven it can,” explains Hall. “From the [blower] gearbox standpoint, the F-4 is going to take less drive power than the Roots blowers they are using now. That said, the amount of power the gearbox takes to produce that amount of airflow and boost is pretty significant. But overall, we should have a substantial efficiency advantage, especially given that the centrifugal efficiency advantage increases as the boost level increases. The technology is just more refined than Roots blowers.”

Will A ProCharger Live On Nitromethane?

The team certainly feels like the technology of their largest centrifugal superchargers is more than capable of powering a Top Fuel Dragster or Funny Car. So, that leads us to the next part of the equation — reliability.

“We have a routine that our F-4 racers go through, and obviously, reliability is a big part of it,” Hall explains. “Our Pro Mod customers change the oil after each pass – six ounces – and there’s a magnet in the gearbox to check for any debris, and that’s pretty much it for the maintenance. We do have them return the blower for a minor service every 40 to 45 passes on it.” [Ed Note: this service procedure applies only to ProCharger’s Pro Mod racers due to the demands of that class and power level; such service is not necessary for smaller ProCharger models in other classes.]

“That minor inspection and service are akin to a restrip or whatever they would call it in the Roots world. Our service is a bit different because there’s nothing mechanical to service on the impeller side, like a Roots needs. But we have a gearbox to look after that we like to service to ensure long-term durability. So our servicing isn’t to maintain performance, but just to keep the mechanical parts working in top shape,” clarifies Sipp.

ProCharger is serious about this idea. While this might currently be a thought experiment, the team is eager to actually see the combination in a Nitro Funny Car.

Hall continues, “So, we recommend that our Pro Mod customers send the blowers in for the minor service after every 40 to 45 passes. Unlike the Roots blowers, as long as you are servicing that ProCharger every 40 to 45 passes, there is no ‘better’ one in your lineup.” That brings up a point that we hadn’t considered, and that is the maintenance schedule of a ProCharger compared to that of Roots-blown Top Fuel engine program.

“Right now a Top Fuel team will have two or three blowers ready to go, and a blower guy on the team that’s all he does is prep the blowers,” Sipp relates. “With a ProCharger, that doesn’t exist; there’s nothing to prep. Basically, you would have a second blower in a box, and if something bad happens, or it’s time for service, you just swap them out and you’re good.”

“One of the benefits to a ProCharger compared to a Roots is, say a guy is on a budget, and can’t afford to restrip the blower every pass, or if he doesn’t have the best blower guy. He’s giving up some performance compared to someone with a fresh blower every few passes and a killer blower guy. The ProCharger doesn’t lose performance throughout the weekend or race-to-race. They are all designed to work the same, so you can swap one blower for another and expect the same performance, team to team, pass to pass,” explains Sipp.

Other Potential Benefits Of A Centrifugal Supercharger In Top Fuel

With the subject of affordability broached, we were curious as to what kind of cost would be associated with switching to a ProCharger in this kind of application. Obviously, Roots superchargers and the associated components don’t seem cheap, but neither do giant centrifugal superchargers. “I would find it very hard to believe that we are more expensive on the front-side costs,” says Fickler.

“But there are still some unknowns there, and almost certainly a Nitro Chaos system would be different from an NHRA system. There is also a difference in current maintenance between racing series. A Nitro Chaos car is servicing the blower once an event, versus what an NHRA Big Show car does, which is pulling the blower every pass, and if it measures more than whatever its spec is, it gets put into the service pile and a fresh blower goes on. Then, there are other costs for a Roots blower setup in the carbon fiber injector hat. Those guys are destroying those pretty often, too. That adds up.”

Fickler brings up the point of Nitro-class explosions, which got us wondering how a ProCharger would fare in such conditions. Conventional thinking says that since the supercharger doesn’t sit on top of the engine, an engine explosion should be a much more survivable event for a ProCharger.

People were hesitant in thinking the F-4s could be competitive in Pro Mod, but time has proven the big centrifugal supercharger to be a fierce competitor.

“Yes, the blower is physically out of the path of an engine explosion, and in a ProCharged application, the burst panel on the intake would take the brunt of everything,” Sipp explains. “But if [the explosion] is big enough, and the crank is moving around, there’s no getting out of the way of that. Sudden shock loads are bad for the supercharger no matter what. So, I can’t sit here and say ‘a ProCharger will be so much more survivable in an engine explosion,’ because the fact is, we just don’t know. What I can say, is that we are in a better position, because we can run better burst panels and bypass valves that could give us a bit of an edge in survivability, but we just don’t know for sure yet.” It is also worth noting that, unlike a positive displacement blower, there is clearance in a ProCharger/centrifugal for an explosion to ventilate through the airspace between the impeller and the volute, lessening the probability of severe damage.

Since Sipp seemed to be laying it all out on the table for us, we stayed on the topic and asked him how the blowers fared in other classes. “In the Nitro Harley world, those guys have blown them up to the moon, and not had any problems with the blower,” Sipp admits. “But, they aren’t driven the same way, and aren’t anywhere near the power level, so we just can’t say until we actually try it. On the alcohol side, we don’t blow up many, but when one of those engines does let go, the blower is usually ok. But with nitro, the explosions are far more violent and they do it a lot more frequently.”

Is This Change Just For Change’s Sake?

In a class that is so similar, fundamentally, to when it began, a saying rings in the back of our head, “If it ain’t broke, don’t fix it.” However, the question should be, why haven’t we seen more innovation in the pinnacle classes of drag racing? “If you look at a Top Fuel car today and compare it to what Big Daddy [Don Garlits] was running in the ‘60s, it’s still a roots blower, with magnetos, on the same Chrysler Hemi. Sure it’s all evolved with technology and bigger and better parts, but it’s the same combination,” says Fickler.

No, as it’s been presented, the ProCharger team isn’t trying to change the class just to change it. The whole team comes across as genuinely believing that they can improve upon something which is already great. “With a Roots blower, once you get to a certain overdrive percentage, that’s it. You can make small tweaks, but you can’t just spin the engine or blower harder; it’s done. With a centrifugal blower, it’ll keep going. You spin the engine harder, you spin the blower harder, and you make more boost,” says Sipp.

A big-power centrifugally supercharged Hemi combination is far from an unproven combination. The Nitromethane adds a bit of a twist, but ProCharger has enough knowledge and experience to sort it all out in short order.

“And, one thing we’ve found in Pro Mod that we think will carry over [to Top Fuel and Funny Car] is predictability,” expands Hall. “There is predictability there with a centrifugal supercharger. The racers like the linear power application and the ease of tuning is a big benefit. Knowing exactly what the combination is going to run, pass after pass after pass, is a benefit to everyone.”

While at the time of this writing, this is just a thought experiment, ProCharger is literally chomping at the bit to take it to the next level. As revealed earlier in the article, there have already been quite a few behind-the-scenes discussions with sanctioning body officials and racers alike. ProCharger has likewise committed legitimate engineering resources to the idea, to make sure that they are as far ahead of the curve as they can be, should they get any form of green light to take this from the drawing board to the prototyping phase.

For anyone who might be overly critical of ProCharger’s idea here, I’d like to leave you with something to consider. There were a lot of people who were highly critical of the idea of centrifugal superchargers being able to compete seriously in Pro Mod. Well, we see how that turned out. So I will leave you with an ancient Chinese proverb I have always been fond of:

“Those who say it can not be done, should not interrupt those who are doing it.”

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About the author

Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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