“With great power comes great wheelspin.” No, it’s not yet another terrible reboot of the Spiderman movie franchise — it’s just a fact of life when it comes to extracting the essence of horsepower and distilling it into useful acceleration. Most modern cars that are even mildly interesting to a performance enthusiast are more than capable of vaporizing their tires at will from a standing start. Top one off with a power adder and the challenge isn’t making the power; it’s actually using it.
Nitrous oxide is particularly challenging in this respect. In its most basic form, when you throw the switch the system delivers nitrous and fuel in amounts determined by the jetting, and it does it instantaneously. If there’s enough traction to handle the additional jolt in horsepower and torque, great. If not, you might as well not even have the bottle turned on.
Getting A Handle On It
To get the biggest possible benefit from a nitrous system — to ‘maximize’ it, if you will — requires a method of controlling it to progressively bring in the additional power in order to keep it at a level the tires can handle. Progressive nitrous controllers, at least in a basic form, have been around for decades, and the principle is pretty simple. By pulsing the electrical signal to the solenoids at a high frequency, and varying the width of the pulses, it’s possible to make a system deliver a variable percentage of its jetted horsepower.
The most basic systems let you set a starting percentage, and how long from the moment the progressive control is activated until it reaches 100 percent duty cycle on the solenoids. It’s definitely better than nothing in terms of controlling wheelspin, but simple progressive controllers like this are fairly blunt tools compared to what’s possible with more sophisticated electronics.
When we installed Nitrous Express’ plate system for 3-bolt throttle bodies on the LS1 under the hood of Project Y2k, our C5 Corvette, and jetted it with the recommended ‘pills’ for a 100-shot, we were rewarded with 97 additional horsepower to the tires as measured on our Dynojet chassis dyno.
That’s all great, but strapped to the dyno in fourth gear (1:1), you’re not going to have any traction issues with a 100-shot. On pavement, it was another story. Y2k isn’t a particularly crazy build, but even so those extra 100 ponies might as well have been unusable in first gear when applied all at once.
What sets the Max4 apart from other progressive controllers on the market? Per NX’s Ryan Lewis, “Throttle-based progression, speed-based progression and AFR targeting, and the ability to handle 120 amps of solenoid control without failure.” The Max4 actually offers four additional control strategies in addition to time-based progression:
- Time-based: Starting from the moment the system is activated, and following the user-defined ramp as time progresses. A good choice for drag racing, where the vehicle is always starting from a dead stop.
- RPM-based: Follows the user-defined progression between a starting and ending RPM. This is useful for vehicles that have enough traction to handle full nitrous at the top of first gear. It’s also a good choice for cars with a ‘tight’ torque converter because you can start the flow at a low percentage down low, to help the car ‘get out of the hole.’
- Speed-based: Nitrous is ramped based on vehicle speed. For racers who do both dig and roll racing, this is a useful control strategy. NX also recommends this mode for bracket racers as a way to manage nitrous cutoff at a selected speed to help keep elapsed times consistent.
- Throttle-based: The percentage of nitrous system activation is tied to the throttle position. Here’s where things get really interesting, because it effectively makes your engine deliver power like one with a larger displacement. You can “pedal” the car more effectively to drive through wheelspin if needed. It’s a useful option for road racing or drift vehicles where smooth application of power is key.
- Boost-based: Varies the nitrous application based on manifold pressure. This is the hot set-up for turbocharged engines, where you can apply a ‘reverse ramp’ to supply a large hit of nitrous when boost is low, ramping down as the turbocharger spools up for an anti-lag effect.
Never Too Rich, Never Too Lean
Another very useful feature is the Max4’s ability to use a wideband oxygen sensor to dynamically control the flow of fuel and nitrous through the system. “AFR correction works by controlling the nitrous and fuel solenoids independently to regulate the flow of nitrous and fuel to richen up or lean out the AFR until the desired AFR is achieved,” Lewis explains. “Setup is fairly easy; every wideband should have all the data needed to input in the Maximizer 4 in order to let the Maximizer 4 monitor AFR from the wideband controller. Once this initial set-up is complete, you just tell it what range of air/fuel ratio is acceptable for nitrous use, and then you can set a desired AFR and also set how quick you would like the controller to correct.”
On a system without AFR correction, as bottle pressure drops during a run, the mixture will gradually go rich, robbing power. By constantly monitoring the mixture, the Max4 can adjust to compensate and keep power consistent and safe. NX suggests jetting the system a bit rich — while the AFR correction can pull either fuel or nitrous to maintain the mixture at the set point, you’ll feel the loss of power if the nitrous gets pulled to compensate for a lean AFR.
Adding to its flexibility, there are a couple different ways you can wire and program the Max4. It basically offers two channels of solenoid control, capable of handling loads up to 60 amps each. The Max4 operates the solenoids by connecting them to ground, and varying the pulse width of that connection to ground.
If you’re using the AFR correction feature, one channel controls the ground on the nitrous solenoid(s), and one channel controls the ground for the fuel solenoid(s), giving fully independent control of each for a single stage. Set up for two-stage operation, each ground connection controls the operation of both the fuel and nitrous solenoid(s), up to a total of 60 amps per stage. “This option is usually used in dual stage plate systems, or controlling one stage on a nitrous plate or single nozzle and one stage on a low amp direct port system,” Lewis explains.
Finally, the Max4 can be configured as a single stage, 120 amp system. Per Lewis, “This is designed for controlling a single stage with high amp, high-flowing solenoids, usually a direct port system capable of flowing more than 600 horsepower of nitrous.”
With that in mind, we set up our plate system using Stage 1 of the Max4’s output circuits to control both the nitrous and fuel solenoids, and wired in the RPM and throttle input circuits to one of the injector leads and the TPS circuit, respectively. Because you can choose the RPM multiplier in the software, the Max4 will work with a wide variety of low-voltage (down to three volts) signals from an aftermarket ECU tach output, a fuel injector lead, or a coil pack trigger.
The instructions give some simple math to come up with the right value for the RPM counter multiplier, but it’s always best to check that it’s reading correctly both at idle and with the engine held at 2,500 to 3,000 RPM. It’s also very easy to see, and set, the throttle position sensor voltage readings from the Max4 software. With these two inputs connected and properly programmed, you have two very important safety features that every nitrous system needs: A wide-open throttle (WOT) switch that ensures the system only runs when the gas pedal is flat to the floor, and a ‘window’ switch that prevents system operation when the revs are too low or too high.
Nitrous Express Lightning series solenoids were designed to work with progressive controllers. – Ryan Lewis, Nitrous Express
Obviously, the way a progressive system works by rapidly pulsing the solenoids has the potential to increase wear or even cause solenoid failure if they aren’t designed for it. “Nitrous Express Lightning series solenoids were designed to work with progressive controllers,” Lewis reassured us. “They have a Teflon seal which does not cut like some other materials, and they also feature a dual spring design on the piston which reduces the harshness of the continuous opening and closing of the solenoid and drastically reduces the wear on the seal. Most people can run NX Lightning series solenoids for multiple race seasons without the need to rebuild.”
Toyo Plus Corvette Central Equals Success
To do our testing at the dragstrip, we needed to outfit Project Y2k with some appropriate rubber, so we turned to two names we trust, Toyo Tires for a pair of Proxes TQ DOT drag radials, and Corvette Central for a pair of C6 Z06 style wheels to mount them on. The TQ drag radial is a relatively recent addition to the highly-regarded Proxes line of race tires, with a specific carcass construction and rubber compound engineered specifically for drag racing. Toyo offers the TQ in two 16-inch, three 17-inch, and one 18-inch size, with widths ranging from a 255 profile up to a 345, covering a surprisingly wide range of modern performance cars.
In our case, we selected the P275/40R17 (part number 172010). C5-savvy readers will immediately wonder how that works, because all Corvettes of that generation came with a “staggered” wheel fitment – 17-inch rims in front, 18-inch in the back. We knew we wanted a tire with as tall a sidewall as we could get, to help the tire hook up, and we also knew that our Corvette’s front wheels fit just fine in back, clearing the brake rotors and suspension with no issues.
With that in mind, we called up our friends at Corvette Central and ordered a pair of 17 x 9.5 inch C6 Z06 wheels – actually a front fitment, but perfect for what we were trying to do, and precisely matching Toyo’s recommended wheel width for the P275/40R17. The end result was exactly what we hoped for, giving us outstanding grip at the dragstrip and providing a comfortable, stable, and safe ride on the street.
Based on our experience, we can highly recommend the Proxes TQ to anyone looking for a DOT drag radial for their late-model RWD vehicle that is as at-home on the street as it is at the track. In particular, if you’re looking for a drag radial and tire combo for your C5 or C6 Corvette, the one we picked is going to be hard to beat.
Ready To Run
With our Max4 installed, programmed, and tested with a 12-volt bulb temporarily in place of the solenoids, we were ready to start using the system for real. At the dragstrip, using the Max4 with the WOT and window switch functions engaged but no ramping, we discovered an interesting turn of events: Launching our stick-shift car at 2,200 RPM and the nitrous set to hit at full power at 2,500 on Toyo TR drag radials (see sidebar), with a fast clutch release the Corvette would dead-hook and drag the engine down, climb slowly out of the hole, then break the tires loose as soon as the system hit. Not ideal.
Lewis had some advice for building our ramp; “The initial goal of a progressive controller was to get off the line without spinning the tires, and still get the nitrous to make as much power as possible. This is still the case in 90 percent of customer’s applications that have a single power adder. The thing to keep in mind, if this is your goal is, to get the ramp to 100 percent nitrous flow as soon as traction allows,” he explained.
“Every application is different, but I usually start the ramp at 30 percent and end at 100 percent over 3-5 seconds and then start shortening the ramp until you start having traction issues, then back up one step so you can have 100 percent flow as soon as traction allows,” Lewis continued. We were interested in basing our ramp on RPM, rather than time; per Lewis, “RPM-based ramps allow the same method of tuning, but instead of tuning by time you tune by RPM, so if your vehicle makes a ton of torque you may not want to bring the nitrous in until after your N/A torque curve falls off and you can actually have the traction for the extra nitrous horsepower.”
Based on Lewis’ general advice, we set our ramp starting with 30 percent at 2,500 RPM, and a 6,000 RPM cutoff. We then redrew the flat line into a curve that brought full power in at 4,500, and used the “smooth points” button to get our curve perfected. With that starting point set, we returned to the dragstrip to test, first with the system turned off, then with it activated. On the motor, leaving at 2,200 RPM and slipping the clutch to keep from bogging the motor, we ran a best 60-foot of 1.922, with an eighth-mile time of 8.31 at 81.2 miles per hour (the equivalent of about a 12.55 quarter-mile pass.)
With our motor-only data in the books, we activated the Max4 and tried again using the exact same technique. Since we were using RPM-based progression and we were managing the clutch to keep from bogging, the system remained inactive off the line and past the 60-foot beams, and we recorded a very similar 2.00 60-foot time, but as the nitrous began to flow, the car stayed hooked as it ramped in, and by the 330′ mark we were actually running more than a tenth and a half quicker than on motor alone. Through the traps, we clocked a 7.98 at 87.94 mph, the equivalent of about a 12.06 in the quarter mile – tantalizingly close to the elevens. More importantly – we picked up over 6 mph in the 1/8 mile, which is about 8.5 mph in the 1/4 mile.
Please keep in mind, our objective here was principally to test the Max4, and we were giving up some E.T. with our 60-foot and configuration settings. Obviously, there’s more 60-foot time to be squeezed out of our Corvette, and we’ll have to dedicate some effort to finding the right combination of launch RPM, clutch slip, and wheel speed to bring it down as far as traction will allow. We’ll also experiment with using the time-based progression instead of RPM to help get the car out of the hole more effectively, but now we have the perfect tool to manage traction and keep all our hard work from going up in (tire) smoke at the track.