by Joe Popovits and Chuck Johnson
Photos by Joe Lu
When it comes to building cars, I’ve always tried to maintain a “keep it simple, stupid” approach. With this approach and an “if it ain’t broke, don’t fix it” philosophy, I managed to produce a stable of solidly performing, competitive cars. At the center of my dead reliable formula was my factory re-flashed ECU. At the cost of a few hundred bucks, I gained a super reliable system and more importantly, the knowledge and experience of one the industry’s best Nissan tuners. I clocked hundreds of thousands of miles on my re-flashed factory ECU with dead reliable performance, hot lapping at Willow Springs on the weekend and commuting to office during the weekdays. It was the perfect set up.
When I decided to get serious about land speed racing, I took this same set up with me and set two land speed records at Bonneville and El Mirage. With each mile per hour faster Project 240SX LSR traveled though, came an exponentially growing need for more capability. I reluctantly dug my heels in denial, touting my “keep it simple stupid” argument. Ironically, that very argument was what would convince me to finally make the change to a standalone ECU. It comes down to this one question. Is a race car running a re-flashed ECU in tandem with a plethora of standalone systems for boost control, wide band sensors, variable valve lift, and data logging really simple? No.
What Team Moto IQ needed was one sole system that provided the ability to define, measure, analyze, improve and control every element of the engine regardless of whether we were on the dyno or on a dry lake bed. Some of you might recognize the terms define, measure, analyze, improve and control as the six sigma problem solving methodology known as the DMAIC process. This article isn’t about DMAIC or six sigma though. Instead, it’s about a true motorsports grade ECU that utilizes a modern 32 bit floating point, 200MHz processor and a real time operating system capable of delivering an 400 million instructions per minute. Enter the AEM Infinity 8 EMS.
The capability of the AEM Infinity EMS’ processor and operating system goes far beyond just a bunch of sophisticated marketing jargon. The level of processing speed and OS strategy allow an ECU to not only respond more quickly to more inputs, but do so without any negative effect in processing speed. This is the value of such a system. Further, a real time operating system allows users to make changes to features that will not affect other features, which isn’t the case with fixed point math operating systems. This higher resolution can mean higher accuracy, which can mean more power in the right hands. More specifically, in our hands.
To help us get started we attended a two day course at AEM which covered the ins and outs of the Infinity EMS system as well as the InfinityTuner software.
Although committed to the switch, I still had some reservations and anxiety about whether or not the team could learn AEM’s InfinityTuner software, get Project 240SX LSR to fire up, and then make the gobs of power we needed in time for Speed Week. Fortunately, I’m not alone in my anxieties as AEM has built a robust customer support system ranging from phone and internet support to a two day onsite course. This was all put in place to help builders and tuners get successfully acclimated to the new Infinity system.
In addition to the technical support, what we found is that ease of use is integrated throughout the InfinityTuner software. One of the best demonstrations of InfinityTuner’s simplicity is its set up wizard which turns the usually menacing process of initial start up into a quick and straight forward process. In our case, we started by loading a Toyota Supra base map. Then, we used the setup wizard to help us begin defining the vital engine characteristics and tailor a bespoke map for our SR15VET 20V engine. Since our engine is a bit of a Frankenstein setup we did get stumped a few times during the start up process, but Beau Brown and Paul St. Clair of AEM’s tech support helped us overcome those hurdles and behold, we had a running engine!
After the initial engine start, the starting process can be refined within InfinityTuner by populating tables for cold start strategies. We used the cold start features which trimmed lambda and fuel at different coolant temperature ranges. Since, we have never had any trouble with cold start.
With the initial start up complete, we turned our attention to tuning. The basic foundation of the InfinityTuner is composed of two complimentary tables, one for volumetric efficiency and the other for target lambda. We started with the target lambda table. What is lambda?
Lambda is the measure of mass ratio of air to fuel found in the exhaust stream. A lambda reading of one is considered stoichiometric, meaning a chemically perfect air fuel (A/F) ratio for a complete burn. A lambda reading greater than one indicates a lean mixture and less than one, a rich mixture. By knowing a fuel’s stoichiometric value, an A/F ratio can be calculated out by multiplying the lambda value and the stoichiometric value. For example, .80 lambda multiplied by the stoichiometric value of pump gas of 14.7 results in an A/F ratio of 11.76:1. If we were to change to E85 which has a stoichiometric value of 9.8, the resulting A/F ratio given a .80 lambda would be 7.84:1. Working with lambda values instead of A/F ratios allows you to tune without knowing the fuels exact composition.
With the target lambda table complete, we turned our focus towards populating the volumetric efficiency table. The InfinityTuner uses a volumetric efficiency (VE) based tuning method. This means that it uses the VE of an engine combined with other variables like target lambda, injector data, and fuel pressure along with a bunch of fancy pants math formulas like the ideal gas law to calculate injector pulse widths.
What is VE though? VE is a measure of an engine’s ability to fill its own volume or how efficient of an air pump the engine is. In other words, if a two liter engine can only fill the cylinders with 1.6 liters of air, then its VE would be 80%. Don’t get confused though, you’re not tuning the VE of the engine. VE is a set of characteristic of your engine which is defined by the components and configuration you run. For example, the bore, stroke, and camshaft profile used in your engine all define an engine’s VE.
With VE based tuning, our job as the tuner was essentially to reverse engineer the VE of our SR15VET 20V at given loads and engine speeds. Initially, this might sound intimidating. However, we knew that the InfinityTuner’s feedback system would adjust our VE to hit the target lambdas we specified and then provide us with a suggested new VE. From there it was just a matter of adjusting the VE table to reflect it. Think of the InfinityTuners feedback system as a super smart kid who’s constantly checking and correcting all of your answers before you turn in a test.
The final step was to fine tune our ignition map. This table controls how the spark event retards and advances with engine speed. Since the ignition map from our previous engine management system had been refined and race proven, we translated it directly over into the InfinityTuner software.
With the basic tuning done, we were left at the tip of the iceberg staring down at a plethora of options and possibilities. Options like nitrous, launch, and traction control were all at our finger tips. In the few days before leaving to Bonneville, we managed to put together a rudimentary gear dependent boost control strategy using the infinity EMS. With the poor condition of Bonneville’s salt surface, we knew that a gear dependent boost control system would be essential in setting a new land speed record.
Any doubts on whether or not switching to AEM’s Infinity EMS was the right choice have long since been squelched. Talk is cheap and quantifiable data coupled with solid results is king.
Since the switch, we’ve significantly increased horsepower and torque across the board. To be specific, we made 625 horsepower and 400 lb-ft of torque with a mere 1.5 liters of displacement. If that’s not enough, we eclipsed our last land speed record by over 10 mph and ran a recorded top speed of 191 MPH. The numbers have spoken, enough said.
So what’s next for Project 240SX LSR? Well, we still haven’t scratched the surface of the Infinity EMS’ capabilities. And next, we have to figure out how to keep Project 240SX LSR from becoming airborne. See, the car is so fast now we literally can’t keep the car on the ground. No, seriously. Consistently at 193 MPH, the rear of the car is lifting causing the car to swap ends and shoot off track. At those speeds, we’re fortunate to not have rolled or flipped the car yet.
The Infinity EMS’ power to define, measure, analyze, improve, and control extends far beyond just that of the power train. That’s right. We’re going to utilize an engine management system to solve an aerodynamic problem. By collecting data sent from shock pots, we’ll be able to analyze and understand the phenomenon that’s occurring at 193 MPH. No guess work here, just scientifically validated changes and the implementation of proven effective solutions. The power of the AEM Infinity EMS is seemingly endless.