The Dark Corners of Fuel-Injected Pro Stock Motor Mysticism
Prepare yourself for a deep, dark dive into a racing rabbit hole. Head first. Pro Stock racing is part of the professional triumvirate of NHRA drag racing, and in 2016, fuel injection was mandated for the first time. The goal was to try and inject the class with more relevance to what’s in showrooms today, to generally invigorate the class, and to interest new teams and engine builders in taking a shot at participating in the most complex—even scientific—class of automobile racing this side of Formula 1. It’s extremely secretive, and rightly so for racing that gushes money to chase 1/100th of a second in the quarter-mile. This is serious, arcane, yet entertaining racing.
With carburetors as the only means for introducing fuel into a 1,500hp Pro Stock engine for close to 50 years, many of the teams knew nothing about fuel injection. With only months to go between NHRA announcing the change and the first race of the 2016 season at Pomona in February 2016, having a race-ready car was a painful mountain to climb. 2012 Pro Stock champion Allen Johnson summed it up when he told us, “I felt like the biggest idiot that ever walked—we couldn’t even get the danged car to crank for a day.”
We spoke with four of the top 10 teams from 2016 to first drill down into their engine programs to find what worked and didn’t, discover what some of their strategies were to try and take advantage of this new world they found themselves in, and finally give their thoughts on where Pro Stock is headed.
Our experts include Jason Line, 2016 Pro Stock champion; John Nobile, a veteran Pro Stock driver who now oversees his son Vincent’s Camaro, which was third in points in 2016 and is part of Elite Motorsports’ team of three Pro Stock cars; Chris McGaha, a privateer who came in seventh with his Harlow Sammons Racing Camaro, but also builds Mopar engines for 14th Place Deric Kramer; and Allen Johnson, the Dodge privateer who, for 20 years, could count on Dodge sponsorship until 2016 when he lost that sponsorship but gained Marathon Oil backing.
The Johnson story was an interesting side note to see where the 2012 world champion would land without his forever sponsor. For 2016, Dodge shifted its sponsorship weight to Elite Motorsports and its drivers: two-time Pro Stock champion Erica Enders and five-time Pro Stock champion Jeg Coughlin. At the end of the season, a disappointed Elite—trailing behind Johnson, who snagged eighth in points—announced it was going with Camaros for 2017. Soon after, Dodge dropped out of Pro Stock entirely. Johnson will run a Dodge Dart with Marathon sponsorship through the 2017 season with a certain amount of satisfaction.
Not everything we discussed gets covered here—we just didn’t have the space. Some questions about engine programs we couldn’t get answered, but all of the intense racers we spoke with were mostly forthcoming, with Line suggesting, “Anything I say, [other teams will] learn something one way or the other, and so the only way I have felt I can win is by not speaking, but it’s not good for our category, fans, or our sponsors.” Some builders deflect specific questions about combos, saying that anyone can make any component work, and this latitude is what they like about Pro Stock. Oblique-speak is a crucial component of Pro Stock. Just getting these builders to tell us anything about their programs is a rare event.
Engine Blocks
Currently, there are three engine blocks used for GM teams and two for the Mopars. The current most popular GM-developed DRCE2 (Drag Race Competition Engine) followed the DRCE1 block and is the most common basis for Pro Stock power. The DRCE3 block was to be an improvement on the 2, including a new head design. This new block features a raised cam location to increase the distance to the crank, adding more and larger cam bearings, going from five to nine for better support as well as providing more landscape for radical ramp profiles and high lobe lifts. Depending on a team’s actual layout, they may not use all nine bearing opportunities. The longer cam-to-crank dimension also makes for shorter pushrods, resulting in less deflection and more stability, all combined to make more power on the dyno. But on the track some teams felt those gains did not translate, so the 3 has become somewhat of an orphan, as all of the GM teams with the exception of Line’s ran 2s exclusively. Some adopted the 3 heads for their 2s, while Line used both the 3 head and block.
The DRCE4 architecture was developed as a response to the 3’s unpopularity. It split the difference between the longer cam/crank dimension of the 2, and that shorter dimension found on the 3. An advantage of the 4 is that teams can use DRCE2 or 3 heads, whereas in most cases, DRCE3 engines only allowed for DRCE3 heads. There are no DRCE4-specific heads. Cam bore increased yet again, allowing for either 70- or 80mm bearings.
For Dodge, there are two Hemi blocks: the 2.0 and 2.1. The 2.0 has a mirrored intake and exhaust configuration, while the 2.1 has an intake/exhaust, intake/exhaust, and so on configuration.
When asked about each teams’ engine of choice, you get different reasons. Says McGaha, “I’m using a 2 and you’ll find that most guys are, except for KB [Line]. If you’re running a 2, then as parts don’t become available, you’ll be able to run a 4 and use some of your 3 stuff to convert to 4, and vice versa for the 2 guys. The 3 never seemed to kick off, and nobody could make it go, so a lot stuck with the 2. In 2009, Line got the 3 to work and they’ve been the only ones to be successful with it.”
Nobile confirms, “Whatever it says on the dyno, you can’t always believe it. And if it has more power on the dyno but not on the track, that doesn’t mean it’s no good. We might have to change our whole thinking process about that change. It’s a science. If there’s time, we will go back to it and take another look.” Line contests the dyno numbers not translating to the track: “If it makes power on the dyno but doesn’t on the racetrack, then something is skewed about one of the two tests. The scorecard doesn’t lie, it has no feelings, so whatever you run you run—so that doesn’t make a lot of sense to me.”
A number of teams were beginning to start 4 engine programs when the fuel-injection change was announced. Says McGaha, “We’ve been doing so much fuel-injection development that it got pushed to the side. My goal for 2017 was to do a 3 head on our 2 block, and if Pro Stock continues on its current path, we’d like to do a 3 head on a 4 block.”
Adds Line, “It’s not like we weren’t winning with the 3, so there was no reason to stop and go work on the 4, and so we put it off and only worked on it sporadically. We hope to have it where we would like it to run for 2017.”
“I’ve always liked the 3 head,” McGaha says. “On carburetors, obviously the 2 had the advantage because other teams and we were outrunning KB. Most of us with 2 programs were a lot alike and doing better than the KB 3s until this year. They were always 0.0100th to 0.0200th back or sometimes just even. But on injection they overcame, and is it because it’s the 3 platform? I don’t know.”
Is the Hemi Better or Worse Than the DRCEs?
For Johnson, his fortunes improved midseason after switching to the Wilson and CFE heads with the intake/exhaust, intake/exhaust, and so on configuration. Says Johnson, “That motor design has been around for a few years, but proved not beneficial to carbureted motors.” He decided to dust it off and try it with fuel injection and was surprised. “With the fuel injection and the lower rpm limit, it proved to be better.” Why? “It just has more torque at lower rpm. The Hemi we’ve been running for the last few years is real good at high rpm, and that’s why it runs so good in bad air—Denver and places like that.” With gear changes at lower rpm, Johnson was at a disadvantage until finding magic with the un-mirrored Hemi heads. Are Hemis inherently slower? Johnson says, “The rpm range we ran before, the Mopars were good or better at high rpm. When they moved the rpm range back, then we’re pulling back in the gear change at 8,400 to 8,500 rpm when we used to shift at 9,100 to 9,300 rpm, and that’s what really hurt the Mopar engines. The Chevys probably had 30 lb-ft of torque more than we have now—that’s the big difference.”
McGaha builds both GM and Dodge engines, and says he knows specifically why the Hemis are down on power: “It’s where the intake valve is positioned in the cylinder head. Even though the port is short, you used to make it up on the manifold because Dodge intakes were always 3/8- to 1/2-inch longer than Chevrolet. When I was doing the engine for Kramer [Pro Stock Dodge] last year, I was trying to make [runner length] as much like a Chevrolet as possible. To judge on the dyno, you measure how much fuel is going through them, and that’s how you tell if you’re improving anything on them. I was able to get the Dodge engine to make the same fuel flow as the Chevrolet, but the Chevy on my dyno will make 1,500 peak hp. The Dodge could make about 1,470 hp, but at 9,000 rpm, it was a night-and-day difference. The Dodge could not make the power at those fuel points. Others may want to differ, but I have tested them and have the facts to back up what I’m saying.”
Fuel-Injection Development
The mandate for fuel injection came down in the middle of the 2015 season, so teams were still in the hunt with their 2015 combos, all but restricting time to begin development of their 2016 FI programs. Spec Holley throttle-body, ECU, injectors, crank and cam sensors, and smart coils were mandated, while wiring harnesses, fuel rails, connectors, and optional sensors were available but not required. The ECU allowed for a myriad of calibration changes from injector end angle phasing, duty cycles, and fuel pressure, though you’re limited to 90-psi injectors. All of this meant one of the main areas of development centered on the intake manifold, where complete latitude could hold gains based on trial and error, and months of dyno time. But the catch was with the elimination of the massive scoops as a mandate to make for more stock-looking door-slammers, you were limited to how long intake runners could be before the plenum banged the hood. So besides length, the shape of the runners, injector location, and size and shape of the plenum were all variables that within certain physical parameters were limitless.
Rumors of some teams testing 200 or more intake variations were laughed at by all of the teams we broached the subject with. Anywhere from about 10 to maybe 35 variations were tested by teams between the end of the 2015 season and the February 2016 Pro Stock kickoff. Says Johnson, “At the beginning, we probably did three different designs and then we were very fortunate to hook up with Wilson Manifolds, and his first design was what we considered perfect. Then we went through two to four revisions of that and are still coming with more revisions.”
Jason Line says they experimented with 10 intake manifolds before they were happy. “We went at it like we knew nothing, because we didn’t. We put together a test matrix for how we should do things. When we did tests, we optimized each combination the best we could. We didn’t have a lot of latitude with injector location, so we did more with other things. The hardest part was optimizing each combination to make sure we weren’t leaving something out there.” Nobile wasn’t satisfied with the intake he started the season with, but experimenting during the season was not good for the Elite Camaro. “We were right on everybody’s tail by the middle of the season, then we started testing a new manifold, and that put us back—I’m kicking myself for doing that,” he says.
Of Johnson’s intake experiments, he says both plenum design and runner length were his main focus: “We just had to keep pecking around to maximize torque without hurting high end, so it was all of the above.” And injector location? “We’ve had them all over the board. We’ve turned them upside down and sprayed them up into the roof—we’ve had them everywhere. There are so many things you can play with that we probably have not hit on half of them yet.”
So is there a lot to be gained in intakes? Johnson says, “I think we’re splitting hairs right now, but now we’re redesigning the whole top end of our engine. We’ve made a big change in the design over the winter, and hopefully that will step us up the little bit we lack.”
Limiters
One of the confounding new rules has been the 10,500-rpm limit. By 2015 some teams were hitting around 12,000 rpm, as the higher they spun the engine the more power they found. Teams are allowed a soft limit, but most don’t use that. “We run right to the limiter,” Nobile says. “Sometimes Vincent will hit it just before the lights to push us through, but you’re always going to lose momentum when you hit the limiter.”
Positioned at the traps and listening to the cars zing through the lights, you notice some hit the limiter before the finish, begging the question, is there an advantage to hitting the limiter before the finish line? Says McGaha, “The reason you do it is because of the way you do the gearing. You don’t make power at 11,300 rpm or 11,400 rpm. You try to control rpm at each gear change to hit as high as you can. The Dodges had to do that. They set the pace because they didn’t make the torque [like Chevy], yet 400 to 500 rpm above a Chevy, they start to make the same power.” From there he says you might start experimenting with rear-end gear ratios, then maybe change transmissions, then from the start to the eighth-mile, this changes gear splits. Says McGaha, “By half track, we get enough to pick the car up, but then at the lights you’ll hear us on the chip. When we didn’t have the limiter, we knew we had enough room in there, so we didn’t care if it crossed 100 rpm higher—we were pressing the envelope, but nobody knew that because we would move the chip up.”
Another discovery by all of the teams was that the rpm limit varied from computer to computer, but even from one run to the next with the same computer. Some teams tickled the max rpm to see if they had another 50 to 100 or more rpm gifted by the arbitrary variances found in all ECUs. Says Line, “Yes, it’s always slightly above 10,500. It’s not as consistent as you might think. It might be 10,530, and sometimes it might be 10,570, so there’s definitely a variance; 40 rpm is nearing 1 mph, so that’s a pretty big variance. Does it affect the e.t. much? No, you might be off a thousandth or two.”
At the 2016 Finals, a frustrated John Nobile said, “We’re running against the damn limiters, that’s one of our problems.”
Cooling the Fuel Charge: Cheating or Not?
A big disadvantage with the new rules is the inherent inability to cool the fuel charge as with a carburetor. Says Nobile, “Pounds per hour to burn on the dyno indicates power—it’s a direct correlation. So you can’t burn as much fuel with fuel injection because the charge is dry and not cold, so it’s going to be down on power from a carburetor motor.” With fuel injection, the charge is dry, and confounding that is air is now taken in from an opening at the lower portion of the front end, where the hot track air rises. Not only do you lose the cooling from fuel but you’re ramming hot air into it from the air inlet that allows a maximum of 80 square inches of opening, which is much more than needed. But for a 500ci Pro Stock engine, for every 10 degrees of higher inlet temperature, you lose 40.3 hp.
“Where you lose from carbs to fuel injection is the cooling effect is lost from what you used to have. You’re trying to rebalance that to make the fuel-injected engine feel like it has the carbs on it, trying to do what Mother Nature used to do for you,” McGaha says.
Some teams found a gray area for overcoming this disadvantage, while others found any attempt to cool the charge as cheating. Interestingly, at the 2016 Finals at Pomona, a rules adjustment for 2017 was announced to close this fuzzy area once and for all. Here’s what McGaha says created this amendment: “You lose the fuel spraying in the intake cooling the air, and I told my guys the way you fix that is you have a spray bar inside of your intake, then you come out from that to a fuel line that goes to your regulator. The problem is that it’s so big it can’t idle with the spray bar spraying, so you need a way to activate it, and the way you do that is with those regulators made for guys who use turbos. If you shoot manifold pressure into them, it starts to raise the fuel pressure, so adding a check valve and using an outside source like CO2, which we all have in our cars, and shooting it to that regulator when you go to WOT, it starts shooting pressure and opens the check valve and a spray bar will turn on.” Were teams actually doing this? “I don’t know, but that’s one way it can be done,” Mcgaha says. “Did I do it personally? No, because I thought it was too gray of an area to be crossing. Did I pay the price for it? I think I did. I think that’s why I ended up in seventh. Who in front of me has it, I don’t really know. I know of some guys that didn’t have it, but nobody in front of me is admitting to having it.”
About this revelation, Johnsons says, “We never tried that, but we heard toward the end of the year that somebody was doing that. It was on our radar to dyno and to rig something up, but we just were not at that point. I didn’t see it as cheating, but it was a gray area for sure. I frowned upon it when I heard, but if they’re smart enough to take advantage of a gray area, my hat’s off to them.”
But the way Line sees it, it’s not a gray area at all: “The way you look at the rulebook is that if it doesn’t say you can do it, you can’t do it, so to me that’s cheating. How could you perceive it any other way?”
Line was really thrown when we asked about auxiliary intake cooling. He added, “Well, the cool thing is whoever it is, when they go to the Winternationals in February, they’re not going to run very good.”
Johnson commented similarly, “We hope everybody was doing that except us. If that’s the case, it will bring them right to the back of the field, and that will be a huge help for us.”
Says Line, “The correct answer for if we were running spray bars is, yes, we were, even though we weren’t, because now when they read this they’ll know we weren’t. And so what this does is tell them there is some place to work toward.” We told you this was secretive!
The Tune
According to all teams, the tune is extremely important, and finessing timing, fuel flow, exhaust pulses, gear splits, and the ever-changing weather all make for optimizing the weeks and months of testing, combined with the quick reflexes and experience of the drivers.
“We were the second fastest car—it’s all about tuning,” Nobile says. “Summit kicked our ass because of tuning. We now have AJ tuning our car, so I believe we’ll be awesome in 2017.” No one will give any specifics, and in some ways there can’t be specifics when factoring in different track altitudes and weather variables, but all teams spoke in general about the importance of the ever-finite tune.
Covering the Engines: Defying NHRA Rules?
Another NHRA mandate was to keep the engines exposed in the pits, something teams don’t like because it could reveal secrets. As Line says, “We struggle for every bit of horsepower we can find and don’t want to give up what we’ve worked so hard to get.” While this change seems simple, with the least amount of pushback, surprisingly, it became a huge sticking point for teams.
Says Line, “We told NHRA that if we had to uncover and show everything we are doing, we would have driven out the front gate. It’s not a crate-motor class; it’s a class that if you do something innovative, you should get rewarded—not penalized. I don’t know what we’d be doing [after quitting], but we’d be doing something else.” Line went on to say that NHRA never told them not to cover the intake manifold, and as you know, this is where the most room for innovation lies. In Line’s case, a cover that looks like an LS cover sits atop the DRCE3 engine, which NHRA says is legal.
Valvesprings
Rumors have suggested that valvesprings are the most limiting aspect to increased performance because of their physical limitations, but every team we ran this by dismissed this, saying there is still more room for gains in valvespring applications.
Is There a Future For Pro Stock?
With Ford out of Pro Stock a couple of years ago and now Dodge/Mopar, with the exception of some privateers, it’s an all-Chevy show. Without the traditional rivalry between manufacturers—the foundation of Pro Stock racing—it has become a much less compelling class.
“You can’t have only one manufacturer,” Line says. “I just don’t think that will be good going forward. We don’t have a fan problem; we have a lot of fans, and there are a lot of folks showing up for the races. I don’t know ticket counts, but I hear from track owners that their fan count was up this year, so that’s all good. What we have is a participation problem, and it’s not just Pro Stock—it’s a problem with a lot of classes. This is a costly sport, and I’m not sure how you justify spending that much money.” There are really only three basics for fans of Pro Stock competition: you’re either rooting for the team, driver, or manufacturer.
As for how Pro Stock will change, no one had any real answers, and we didn’t discuss the future of Pro Stock with NHRA because we know it’s something they won’t discuss. Says McGaha, “I’m a younger guy and I race Pro Stock because it’s naturally aspirated [NA], and when you get down to it, this is all that’s left that is NA. What bothers me the most is when some say they want to change it from NA. GM had the Grand National in the 1980s that had turbos on it, but Chevy never had a forced-induction car until the ZR1 Corvettes in 2009. Now everybody has this notion everything needs to be forced induction in Pro Stock because factories are doing it, but in reality, only 5 percent of cars are forced induction and the rest are NA. I don’t know what NHRA is thinking, but that’s the nail in the coffin for me.”
Nobile would still race if Pro Stock went away. “If there’s only one manufacturer involved, there’s no reason for Chevy to stay, so I would really like to see Ford and Dodge back into Pro Stock. Look, there’s nothing like Pro Stock. Vincent was approached to drive a Fuel car and he turned it down, and we’re not interested in Pro Mod. This was the safest class in professional drag racing, and if they were to go to superchargers or turbos, they would blow that. If Pro Stock were to go away, Vincent and I would still drag race, but we would probably go bracket racing.”
Allen Johnson, in conjunction with Dodge, approached NHRA in 2015 about providing a future concept-spec Pro Stock Challenger. The idea was to have a 1,500hp supercharged crate engine based on the third-gen production Hemi in a chassis similar to current Pro Stock cars, but with stock-type sheetmetal. It was estimated that the 1,500hp engine in a Challenger would generate similar times to current numbers, but do it with something powered by a production-based engine that looked like a production-based car. Johnson said he was under the impression GM was behind their concept. They did not get much NHRA feedback, and obviously the fuel-injection mandate took the class in a different direction, with the end result that costs escalated and Mopar joining Ford in abandoning the class. Now it looks like NHRA might have erred in not giving the Challenger concept more consideration.
Johnson is not happy with the current state of Pro Stock: “If they continue down this road, you’ll have part-timers running four to five races and a couple racers running 10, we’ll struggle having a full field every week, people will lose more interest in it because you only have one brand of cars, and the class will really struggle.” Would he consider switching to GM? “No, I’ve raced Mopars all my life, and I would retire before that happens.” Is that because of brand loyalty or that it’s his whole program? “A little of both, brand loyalty being most of it. Reinventing the wheel and spending millions of dollars retooling with different parts, it’s too late in my career to do that.”
He says his future intentions are to continue in Pro Stock, but he won’t spend his own money doing it. So would it bother him to have to switch to a production-block-type of Pro Stock racing in the future? “Well, it might bother me, but for $100,000, I could race half of the year and this other stuff could just sit—it’s not eating any oats if it’s just sitting.”
Jason Line adds, “We knew that somebody, somewhere, was going to figure this out sooner and better than the rest, and that within a year we would all be running the same, and that’s what happened. To me that’s boring and not what racing is about—it’s about being faster than somebody else. But if you’re working within a small box that is so restricted there’s no room to be better, then how are you going to be better?”
How, indeed. The future will tell.
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