Real Street Superchargers Test
Can 5.0&SF bring parity to the Real Street blower wars on the engine dyno?
We have to admit it. We watched with great interest as our little Real Street class grew up last year in the NMRA Ford Drag Racing series. At several races this season, the Real Street class was only outnumbered by such venerable classes as Super Street Outlaw and Drag Radial. Our baby has certainly grown up in two years, closing out the season with a 25-car field at the finals, and low, low-10-second passes courtesy of Brian Meyer and Bruce Hemminger.
Not only did Brian and Bruce have two of the quicker cars this season, but they also represented a somewhat alarming trend of the class becoming a Paxton-versus-nitrous class. Now, we love the power-adder wars as much as the next guy. But let's face it--it's more interesting to fans and magazine types, and it's more accessible to racers, if someone running any of the legal power adders feels as though they have a shot at being competitive in the class. We helped come up with the basic concept of the class, and the NMRA fleshed it out with real rules and made it work. As such, we don't have much say in the making of rules, but we can at least give our opinions like anyone else.
We kept hearing the Paxton supercharger had an advantage over the Vortech and ATI/ProCharger offerings legal in the class. It's really not difficult to understand. The Paxton unit is physically larger than the other two, and it's run successfully in Renegade where it's nearly backed up the eight-second potential George Greco showed in Pro 5.0 all those years ago. We understand it was the only Paxton kit available for the Mustangs at the time the rules were developed, so what was to be done?
Well, we'd been curious to find out how much of an advantage the Paxton had, and we'd been in the early discussion stages with racer Robin Lawrence--set to make the jump from Factory Stock to Real Street--to test the legal units coming from Vortech and Paxton. Vortech was set to sponsor Robin's R/S efforts, and the two products are produced by the same company, so that seemed easy enough. Then we happened to be talking to ATI/ ProCharger's Dan Jones and he brought up the concept of equalizing the boost of the various blowers. We agreed it was a great idea and asked if he'd like to participate in a three-way blower test with the goal of equalizing the peak boost of the Real Street blowers.
He quickly agreed, as did Vortech's Ricky Best, so the test was on. We wanted to hurry in order to have our results complete before the NMRA finalized its rules. The organization made no promises to do anything one way or the other based on our test, but we thought any extra information might be helpful to the NMRA tech staff. We proceeded knowing we'd at least learn something along the way and be able to share it with you.
Getting two fierce competitors to agree on a head-to-head dyno test was no easy task, but the concept of leveling the playing field by equalizing boost seemed to appeal to both parties, as did allowing representatives from both sides to be present to ensure everything was on the up and up. We set our test parameters to begin by testing the blower kits in '02 NMRA-legal trim--with a safe tune-up to avoid breakage--simply to verify the out-of-the-box boost levels achieved. Since we realize boost equals power, we'd then change the pulleys to equalize the boost at an agreed-upon rpm. Finally, we'd tune the program up for power to see what these blowers produce making the same approximate boost.
Sounds simple, right? Well, try doing it in a two-day window a little more than a week after the NMRA World Finals in Bowling Green. That meant Robin didn't have time to get his motor program together for our test, so his old pal Craig Baldwin bravely offered his Real Street motor to the altar of dyno abuse. Craig had qualified ninth with a 10.45 at 130.82 at Bowling Green, so it was definitely a competitive combination. And the nice thing about the limits on the Real Street engines is, there's little to argue about when it comes to headers, throttle bodies, cams, and mass air meters. You can only go so big, so our results would likely be similar to those of most R/S competitors.
If you've ever run a fuel-injected engine of any kind on an engine dyno, you know it can be a challenge to set up and run. The sea of wires and connections required to simulate the engine's placement in a car are many, and the resulting scene looks as if it's straight out of Frankenstein, with a concrete dyno cell consumed by an engine and a nest of electrical wiring. Fortunately, Robin and Craig had already gotten Craig's engine up and running on the dyno at Don West Racing Heads (where Robin does a great deal of testing for his racing programs), because our test required more than just an EFI wiring harness.
In addition to the factory Ford wiring, we added an Anderson Ford Motorsport-spec Programmable Management System piggybacked onto the stock EEC IV, an MSD Digital 7 ignition box piggybacked onto the factory ignition system, and an Auto Meter data-logger plumbed into various parts of the engine to record key data such as boost, fuel pressure, air-charge temperature, exhaust-gas temperature, and more. Throw in three laptops to control and keep track of all this hardware, and you'd think we were benchmarking computer equipment rather than conducting a supercharger dyno test.
With all those electronics in the room, it's amazing the engine ran as well as it did, let alone that it survived the nearly 50 dyno pulls we put on it to come up with our final numbers. Thanks again, Craig!
Finding the Tune
Though the engine ran well, it didn't start out as happy as it finished. We began the test by bolting on the Paxton Novi 2000 kit in '02 NMRA-legal trim. We wanted to start with the presumed big dog and see how much boost it made and where, before we decided on a peak boost number and rpm. It seemed to be a sound plan, until we started to run the combination.
Of course, just before we left for the test, we learned Robin and Craig went a little too close to the edge while testing Craig's original Vortech V-1 S-Trim combo on the dyno. They wanted to make sure the engine was running well and to come up with some kind of tuning baseline from which to start, which was fine. However, when the tuning bug bit too hard, they squeezed out a head gasket--and changed only that gasket. (You can see where this is headed, right?) With the Paxton strapped on, we couldn't get it to run cleanly. As we played with fuel and timing curves just to get it to pull smoothly, we squeezed out the other head gasket--you know it's bad when water is spraying out the oil-filler neck. Our guess is this gasket was already weak from Craig and Robin's experiment and only fell off its last leg.
By this time, Robin was becoming a little testy, the crowd of supercharger reps was growing restless, and we were beginning to wonder why we'd try to pull off this test in the first place. It really wasn't a big deal--it was only head gaskets, after all. Robin, Craig, and Ricky tore down the motor and put it back together in short order, but then it wouldn't run. It turned out Craig's distributor had a bad TFI module, but despite all the spare parts strewn about Don West's shop, we didn't have a replacement. That meant Craig had to take a trip to his house, about 20 minutes away. By this time it was getting late, so we resolved ourselves to getting the motor running and starting fresh early the next day.
Surprisingly, we did just that. The distributor solved our problem, the motor rumbled to life, and we made pulls with it in the morning. Despite new gaskets, the motor still seemed to be fighting us. It seemed the big Paxton might be surging on the little R/S engine, and after moving to colder NGK spark plugs and tweaking the fuel and timing, we eventually tuned it to a point with which we felt comfortable. The Paxton made good power at 583.2 peak horsepower, but the curve was still jagged. We were curious why the combination seemed a bit grumpy, but as time was of the essence, we decided to press on.
Our travails weren't quite over when we moved to the ATI/ProCharger P-1SC-II. Though ATI sent both A/C and non-A/C bracketry, we lacked an idler to make the accessory belt function correctly. Apparently, most ProCharged Real Street racers move to a standard-rotation water pump and don't use the idler, but we were still using a reverse-rotation pump, so we used one of Robin's dyno idlers and went on with the test. ATI's Dan Jones said future versions of the kit would include an idler so customers with either setup are covered.
With the kit installed, we decided to take out a bit of timing just for safety, and run. We eventually ended up with the same tune-up as the Paxton, just a bit leaner up top. Then, as if we'd scripted it, the Vortech was happiest with that tune-up as well. Since the slight leaning at high rpm worked with the other two, we decided to strap the Paxton back on and see if a little less fuel up high would clean up its power curve. After one pull with the same tune-up, it was still a little jagged, but with a second pull under the same tune-up, the curve magically cleaned up, and we ended up with the numbers you see in this story.
By now you've probably noticed we haven't said much about our tuning. That's because Robin was using our test as a learning experience, and since he did a lot of the legwork, we agreed to let a racer's secrets stay his secrets. What we can tell you is Robin likes to pull the spout and run fixed base timing, then tweak it slightly with his MSD Digital 7 software. After examining the EGT's readings on the datalogger early on in the first round of Paxton testing, he decided to take a bit of timing out of the two hottest cylinders, as the Digital 7 allows for individual-cylinder timing control. Robin then does his fuel tuning with the PMS. And, since you'll see we ran out of injector, we did have to fiddle with the base fuel pressure as well.
But, as we said, the power numbers you see in this story were all generated with the same tune-up, which was great for consistency. In fact, after our test, Robin and Craig put the Vortech back on and started tweaking the tune we used. By building a complete timing curve--rather than fixed timing throughout--and leaning the fuel a bit, they were only able to find another 15 or so horsepower, so our safe test tune-up was fairly close.
In the End
So, what--you read all this and you don't even know what we found out? Sure you do. We know you skipped right ahead to the captions and dyno sheets and you think you have it all figured out. Maybe you do, but keep in mind there's a lot of data to sort through, so take your time, and make sure you read our Inside the Numbers sidebar before you begin analyzing the numbers. What we came away with is, in '02 NMRA-legal/out-of-the-box trim, there is a great disparity in boost output between the three blowers. At about 7,000 rpm the Paxton peaked at 19 pounds of boost, while the Vortech produced 18.4 and the ATI/ProCharger 16.1. After we changed pulleys and began to target 6,800 rpm as our equali-zation point, the Paxton made 15.4 psi with a 3.7-inch blower pulley, the Vor-tech made 15.7 psi with a 3.5-inch pulley, and ProCharger with the '02-legal 4.5-inch pulley made 15.6 psi. With these pulleys, all the blowers made strikingly similar power and boost, while the respective curves, as expected, were slightly different for each supercharger. But we'd expect them all to be more equally competitive in Real Street given these pulley changes, and that's what we were after. 5.0