Professional drag racing is a world measured in hundredths of a second on the track and ounces on the scales. Technology is taking over every aspect of drag racing, from parts that are stronger and lighter, to engines that make more horsepower than ever thought possible. An ever changing rule set that levels the playing field and the willingness of teams to explore all avenues of performance advantage has led to a war between power adders that will be remembered for ages. Nitrous, turbocharged, and supercharged racers are fighting tooth and nail to stand atop the podium and prevail in some of the tightest racing the sport has ever seen.
“Leave no stone unturned” is a necessary approach within the professional drag racing ranks. Anything that’s proven to add horsepower has been fully adopted and figured out. Or has it? As a collective, turbocharger and supercharger boosted engines have not utilized the benefits of vacuum systems and the negative crankcase pressure they produce.
To gain a better understanding of vacuum pump technology and their inner workings, we spoke wit a number of the top names in the industry, including GZ Motorsports‘ Greg Zucco, Moroso‘s Scott Hall, Judson Massingill of the School of Automotive Machinists, Mike Morton of Peterson Fluid Systems, Jason Pettis of Pettis Performance, and Total Seal’s Keith Jones.
Why Negative Crankcase Pressure?
Creating negative pressure in the crankcase has many benefits that help increase horsepower. Moroso’s Hall has a deep understanding of boosted engines, as he races a blown alcohol Top Dragster in the NHRA. Hall believes there’s always power to be made with crankcase vacuum control.
Says Hall, “The vacuum pump has a place on these engines — we have the ability now with better ring packages, hone packages and better blocks, so we can make more vacuum. We now see a 2-4% horsepower gain with vacuum pump systems, and we’ve seen it on everything from a small four cylinders to a 903 cubic inch nitrous Pro Mod motors. It seems like it’s the same number no matter what you do, and no matter which combination, as long as the system is designed properly and maintained.”
So how does crankcase vacuum create horsepower? It’s a combination of many small changes, starting with the rings. A vacuum pump will create negative pressure in the crankcase, and that negative pressure will remove air mass and create less atmosphere on the bottom side of the rings, creating a more stable environment. This environment change has allowed engine builders to reduce the size and tension of the ring stack; creating less friction, less heat, and less power being robbed from the combustion process. Better ring seal is a nice advantage too.
“There’s power in pulling vacuum on the engine, in two ways; it relieves pressure underneath the piston, and it lets you reduce the oil ring tension, and that frees up friction,” says Judson Massingill. “The oil ring itself is one of the major points of friction in an engine.”
We now see a 2-4% horsepower gain with vacuum pump systems, we have seen it on everything from a small 4 cylinder to a 903” Nitrous Promod engine. – Scott Hall
“Anything you can do to keep the oil where you want it, near the pump pickup and getting back to the oil tank, is going to help you. De-aerated oil lubricates better than oil that has a ton air whipped into it. A crankcase is theorized to contain hurricane force winds at high engine RPM, so anything that can be done to take the air out of there is going to aid in oil control,” explains Morten.
The Hold Up
With major advantages to running crankcase vacuum in a boosted engine, there’s not been wide-scale adoption within the ranks. Boosted engine racers have made so much more horsepower than their competitors, that finding a little more horsepower hasn’t been on the top of the list. Focusing energy and financial resources on finding a bigger supercharger or turbocharger to make big horsepower gains, or working on the chassis or the drivetrain has been more common in the past and present.
In today’s climate, the chassis are working phenomenally well, supercharger and turbocharger size is being restricted, and nitrous racers have been making big advances in power (and getting to take weight off the cars). Boosted racers are noticing the smaller things are starting to count.
So what’s the hold up?
Total Seal’s Jones lays it on the supercharged culture of ‘more boost can fix it all’. “The blower world today has a tendency to do things as they have for 30 years. There’s no stone unturned in Pro Stock, Competition Eliminator, and Nitrous Pro Mod engine programs. But you have to run a blower program like you’re running a top-tier Comp Eliminator engine.”
It takes a lot of determination and manpower to operate a Pro Stock-like engine program, where vacuum system technology has been advancing for forty plus years. Nitrous engines have benefited a great deal from the Pro Stock technological revolution, taking the R&D of the naturally aspirated teams and applying it to their nitrous gulping mountain motors. Is there a path forward for the boosted racers similar to what the nitrous and naturally aspirated teams have gained from Pro Stock? Or is there even a reason to add the complexity of a vacuum system to a boosted engine?
Using a data acquisition system with crankcase vacuum measuring capabilities, in conjunction with a crankcase vacuum control system, allows the racer or engine tuner to keep an eye on overall engine health. Monitoring vacuum levels throughout a run can shows areas where the tuneup is not correct, looking for jagged areas in the run log can show points where the engine is detonating and fluttering the rings.
“The major gain with vacuum pumps comes from sealing the top ring better on the intake stroke, pulling more air and fuel in with better ring seal, which allows for a bigger charge to be burned and making more power. Because a boosted engine doesn’t rely as heavily on vacuum to fill the cylinders, the horsepower gains will be smaller.”
Pettis followed up, clarifying the gains: “When every horsepower counts, especially in limited power adder applications, crankcase vacuum will make more horsepower. Even if it’s only a little more, it is more.”
Making crankcase vacuum on a boosted engine is harder than making crankcase vacuum with a nitrous or naturally aspirated engine. The average cylinder pressure on a boosted engine is much higher, causing more combustion gasses to escape past the rings and into the crankcase (blow-by). When this volume of air is higher, the vacuum system has to work harder to remove all of the combustion gasses from the crankcase. There are two types of pumps used to remove these unwanted combustion gasses: vane-type vacuum pumps and dry sump oil pumps. They each have their pros and cons, and should be used together for best results.
Vane-type vacuum pumps, like the ones offered by GZ Motorsports or Moroso, use reciprocating flaps (vanes) to paddle the air through a cylindrical body to create a vacuum. Connecting the body to the engine results in combustion gasses being sucked out of the crankcase and forced in to a puke tank. Usually, vacuum pumps are a single stage with three or four vanes. These pumps are efficient at pulling air out of the engine, but have a difficult time pumping oil. Vacuum pumps are more suited to creating negative crankcase vacuum that dry sump pumps.
It’s not just the rings, it’s the whole package; pistons, rings, quality machine work to get the right cylinder finish, and a proper tuneup. – Keith Jones
An engine that’s sealed well to outside atmosphere and doesn’t produce excessive blow-by can get away with only a dry sump pump to pull negative crankcase pressure. Morten shared the importance of sealing the engine.
“The biggest thing is getting people to understand how important sealing their motor is; using double lips seals, good valvecover gaskets, and overall just trying to keep crankcase vacuum from pulling in outside air,” says Morten.
Zucco followed Morten’s sentiment, “We make a high flow, high suction vacuum pump; we want the pump working to remove unwanted exhaust gaskets from the crankcase. Pulling air past the valve cover gaskets and the china wall at the back of the manifold just makes the whole system inefficient. We recommend quality gaskets and extra attention to installation at all sealing points in the engine. Keeping the engine sealed to outside atmosphere is critical to the vacuum pump working properly.”
Our in-house race car, Project BlownZ, has a Dailey Engineering six-stage dry sump pump and no vacuum pump. BlownZ is making north of 2,000 horsepower and is able to maintain negative crankcase pressure for an entire seven-second ¼ mile pass.
Much thought went into BlownZ’s combination, and at the behest of Total Seal, a high tech low tension ring stack went into the engine, making it critical to evaluate and engineer everything to be better. Jones explains “It’s not just the rings, it’s the whole package; pistons, rings, quality machine work to get the right cylinder finish, and a proper tuneup. Rings: I make them flat, I make them round, I make them from the right material, but I can’t make the tuneup or the combination right.”
The last step is plumbing and packaging, as special care needs to be taken to build the combination with a crankcase vacuum control system in mind. Zucco reminds us of the pitfalls many fall into. “Pushing air through a line is much different than trying to draw it through. It’s much harder to suck the air through the same diameter line. A -10 braided hose is barely a half-inch wide on the inside — do you want to try and expel all those trapped exhaust gasses from the crankcase though a half-inch hose? I recommend a minimum hose and fitting size of -12 with higher flowing vacuum pumps.”
Supercharged racers have to figure out how to drive their supercharger off the crankshaft, as well as the vacuum pump and or dry sump. Turbocharged racer need to find a place to put everything, as it can get really crowded when the turbos are in front of the engine. NHRA-legal blown alcohol racers have an extra hurdle that adds to the complexity, as Hall explains: “to properly plumb up one of these systems, make it functional, and be NHRA-legal for blown alcohol, there’s a lot of plumbing going on. The blown engines have to have burn down tubes on the valve covers with minimum one-inch inside diameter, which have to be separate from the vacuum pump system. When you’re required to run a burn down tube system, you have to have a reliable and high-flowing check valve in the burn down tubes to act as a required safety relief. The vacuum pump can not and will not accept enough air to expel all the gasses from the crank case in the event of a total engine failure.”
Altogether, it’s nothing smart racers can’t handle. When something is worth doing, because it makes extra horsepower and improves the oiling system, it will eventually become mainstream. Do you really want to leave any power on the table?
If you want to win in 2014, keep doing what you’re doing; if you want to prepare for the evolution of supercharged and turbocharged engine performance, you need to get in front of the pack and start working with a vacuum control system that will help you make more horsepower and keep the oiling system happier.
“Good enough is not good enough; it has to be done right, what was good enough in 1965 is not now. We are in a time where 20 to 40 horsepower is the difference between winning and losing.” Jones could not have said it any better.