What Engines Do Funny Cars Use
| How-To - Engine and Drivetrain
8000 hp Funny Car 426 Hemi Extreme Engine
They Make Somewhere Around 8,000 hp and Push a Car Over 300 Mph In Less Than Five Seconds. We Dig Deep to Find Out How?
Of all the extreme and crazy acts perpetrated via internal combustion, the Top Fuel/Funny Car motor must be the most outrageous. From eight cylinders and 500 ci of displacement, it can make somewhere between 7,500 and 8,500 hp. And that's just the current educated estimate. You can't run one of these things on a conventional automotive dyno; you'll just break it. The dyno, that is. And getting real, useful numbers would be problematic anyway, since these monsters are designed to run at full power for no more than five seconds at a time.
To get the real story on what these ground-pounding, ear-shattering freakasaurs are about, HOT ROD paid a visit to Kalitta Motorsports in Ypsilanti, Michigan (www.kalittaracing.com). One of drag racing's true pioneers, Connie Kalitta-the Bounty Hunter, number 21 on NHRA's all-time Top 50 list-has been successfully running fuel motors as long as anyone in the sport. Four cars currently race out of his state-of-the-art shop: the Top Fuel dragsters of David Grubnic, Hillary Will (run in combination with Ken Black Racing), Connie's nephew Doug Kalitta, and the Funny Car campaigned by Connie's son, Scott Kalitta, two-time NHRA Top Fuel champion. Kalitta Motorsports has a well-earned reputation for coming to every race loaded for bear, with engines that can throw down as much power as anyone's. Doug Kalitta's dragster currently owns the quickest run in NHRA history, with a 4.420 lap at Joliet in 2004.
But whether they are Top Fuelers or Funny Cars, all four beasts in the Kalitta stable run essentially the same engine combination. The chief difference between T/F and F/C engines is that for safety reasons, NHRA requires the Funnies to run dry-sump oil systems. And because the short-wheelbase fuel coupes are more traction-challenged, their race-day tune-ups tend to be a tad less aggressive. But beyond that, the engines are nearly identical. So Jim Oberhofer (known to everyone as Jim O), who serves as crewchief on the Top Fueler of Hillary Will, was able to give us the complete lowdown on the engine in Scott's Funny Car.
As everyone knows, the engines currently used in pro fuel drag racing are very loosely based on the 426 Chrysler Hemi. While it has its roots in that design, in truth, a modern T/F engine shares noparts and almost nothing in principle or practice with the original '64-'71 Mopar production engine. While some bolt holes can be found in the same locations as in the original 426 Hemi block, that's about it. Over the years, the package has taken a steady climb up the evolutionary ladder to make it stronger, safer, and capable of containing even more power. One key consideration is ease of maintenance since, as we have seen on television, Fuel motors must be torn down and completely overhauled after every round. "These engines are designed to be quick to work on," says Jim O. "They're made like a big zipper. You unzip them, change everything out and then zip them back up again. The crew can break down and rebuild the entire engine in 40 minutes. It takes seven guys. I call it organized chaos."
While the original 426ci Hemi used a 4.250-inch bore and 3.750-inch stroke, Kalitta Motorsports runs a 4.1875-inch bore and 4.500-inch stroke for 496 ci, nuzzling right up against NHRA's 500ci displacement limit for Funny Car and Top Fuel. (Among Fuel racers, this combination is traditionally known as a "three-quarter stroker. ") A Bryant billet crankshaft, massive Brooks or Childs and Albert aluminum rods, and forged-aluminum pistons from Venolia or Diamond make up the rest of the short-block. The hardware inside a Fuel motor is big, strong, and fairly straightforward as racing engines go. Of course, the real key to the ridiculous power made by these engines is the fuel: nitromethane.
Nitromethane contains only one-fourth the heat energy of gasoline. However, it requires only one-eighth as much air for complete combustion. So if you run it through an engine and get everything just right, with nitromethane you can make four times the power. To put it more precisely: The stoichiometric (chemically ideal) combustion ratio for gasoline is 14.7:1 in air to fuel by mass; for methanol it's around 6.7:1. But for nitromethane it's 1.7:1. So if you are going to make power with nitro, you are going to have to burn huge quantities of it. Kalitta's engines run a camshaft-driven Waterman fuel pump that can deliver up to 93 gallons per minute. The car carries 18 gallons of fuel on board, and over an entire two-minute run (including starting, staging, and burnout), the engine will consume around 13.5 gallons. "The actual run takes around 41/2 to 5 gallons," says Jim O. Whoa. Since a typical Funny Car run lasts around 4.8 seconds, that means fuel is being consumed at approximately 1 gallon per second. Consider that for a moment: a Top Fuel or Funny Car engine burns fuel at roughly the same rate as a 450-ton Boeing 747 jumbo jet.
To deliver all that fuel, a total of 42 fuel-injector nozzles are deployed throughout the engine's intake system. There are 10 in the blower hat, 16 in the intake manifold (8 of which are tunable helper nozzles), and 16 more in the cylinder heads, spraying directly into the humongous intake ports. The lower, or "down" nozzles provide the majority of the fuel delivery. Naturally, lots of air is required to combust such enormous quantities of fuel. NHRA rules limit TF/FC engines to a single Roots blower (no Lysholm or twin-screw superchargers allowed) of so-called 14-71 size, meaning an effective case and impeller length of 19 inches. Lighting the mixture are two 44-amp MSD magnetos firing two spark plugs per cylinder.
The heart of the monster is a Waterman four-section, two-stage fuel pump, capable of delivering 93 gallons of fuel a minute-it can fill a standard-size bathtub in about 26 seconds. Around 13 gallons of $30 per gallon nitro are consumed over an entire two-minute lap, including starting, burnout, and staging. "Fuel volume is the most important factor in making power in these engines," Jim says. "At the 'step' (when the driver fully steps on the throttle -Ed.) about three-tenths of a second into the run, the motor will see around 55 gallons a minute at 8,250 rpm. About two seconds into the run when the slide valve closes and the engine is up on the fuel regulator, around 73 to 75 gallons per minute is going through the fuel meter. Which means there's around 18 gallons per minute or so in return flow. So you're not using everything the pump can deliver, but you always want some in reserve."
In recent years, the NHRA has taken numerous steps to manage performance, including limiting the fuel mixture to 90 percent nitro (with 10 percent methanol) and mandating an electronic rev limiter that caps engine speed at 8,250 rpm. Even so, says Jim O, "We've done testing with torque sensors and so forth on the car, and I would say we have a legitimate 7,500 to 8,500 hp. The rpm ranges from 8,250 at the step down to the lowest point at 2.5 to 3.0 seconds out at 6,500 to 7,000 rpm, right when the clutch is going to 1:1. At maximum torque in the middle of the run you will see numbers like 6,000 lb-ft."
When in mid-2004 NHRA lowered the allowable nitro percentage to 85 percent, it caused racers plenty of headaches and parts failures-it seemed to thoroughly scramble their tuning combinations. "We were just wearing out everything twice as fast as we used to," says Jim. With the nitro limit restored to 90 percent for 2008, Fuel racers are looking forward to refining their setups. We tried our best to get Jim O to reveal the killer tuning secret to these unbelievable machines, but he wasn't having it. He gave the standard answer all crewchiefs give in every form of racing, so boring and yet so absolutely true: "The first things you have to have are good people and good parts. Until you have those, you can't build a good combination."
If a blown nitro engine's fuel pump is its heart, then the magneto system is its brain. Kalitta uses two crank-triggered MSD magnetos that generate 44 amperes each, firing two plugs per cylinder. All 16 spark plugs are replaced every run. While nitromethane has a fairly decent flame speed, there is so much of it to be burned here, and the combustion chambers are so large, that extreme spark advance ("lead," as fuel racers call it) is required: typically from 55 to 60 degrees. "Sometimes you might take out 15 to 25 degrees at 0.7 seconds to stop tire spin or shake," Jim says.
Kalitta currently runs a specially coated magnesium-case PSI blower at 37.9 percent overdrive, replacing the rotor-to-rotor seals every two runs and the rotor-to-case seals every four runs, at 0.002 inch to 0.0025 inch clearance. "At the step you'll probably see around 42 psi of boost, and at the finish line 52 to 53 psi," says Jim. Two or three blower assemblies are typically required to make it through a race weekend. Note the extreme rearward blower offset, designed to equalize fuel/air distribution among all eight cylinders. When one or more cylinders go lean, a big boom usually follows. HRM
Source: https://www.motortrend.com/how-to/hrdp-0805-funny-car-426-hemi-engine/
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