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Performance Engine Mods
By Brendan Baker
It’s been called the brain, and essentially that’s what it is. It can be confusing what to call engine management systems these days because they are called so many things: engine control units (ECU), powertrain control units (PCM) or onboard data systems (OBD). Until recently, the ‘brain’ was a locked box, only to be touched by OEM’s hands.
For the most part, these brains have been pretty good at achieving their objectives under normal operating conditions. The conditions the brain typically controls are timing, fuel, boost (if applicable) and a whole host of other things from the emissions system, ABS and electronic transmission control to the new "fly-by-wire" throttle control available in some new models.
It may be a stretch to say that engine builders are going to flock to tuning ECUs, but for those performance engine building shops looking to add more services, performance "chip" tuning may be an option. Several tuners have pointed to the fact that carburetors are going "the way of the dinosaur" and that engine builders should start now to build their understanding of these systems.
Compared to the carburetor, the simplest engine management system coupled with electronic fuel injection (EFI) can have far greater control over an engine’s functions. In fact, most engine management systems can make 10,000 or more individual adjustments for each second the engine is in operation. "Think of an old carbureted motor on a racecar" says Jack Friedman, general manager and director of UniChip. "Every time the weather changed you had to change the jets. The same thing holds true with a fuel injected motor, it’s just that it is happening electronically."
UniChip is a division of The Porsche Group, which, by the way, won this year’s Rolex 24 Hours of Daytona and last year’s 24 Hours of LeMans.
One argument for engine builders to learn about chip tuning is that it may be necessary to remap the ECU in order to achieve the full benefit of your monster horsepower engine build. "Many people are starting to realize that the ECU is power," says Friedman. "For example, the BMW F1 engine wouldn’t be able to make, or use, 900 hp in a normally aspirated motor without an excellent ECU. That’s the key," he says.
There are basically three types of performance ECUs:
The standalone, which is a complete replacement of the factory ECU and is a fully controllable system.
The "piggyback" system, which coexists with the OE computer but intercepts signals going to the factory system in order to trick it into thinking that everything is normal. This enables the system to change some settings but leave others alone. It also uses the OE sensors for input.
The EPROM (Erasable Programmable Read-Only Memory unit), commonly referred to as a "chip." These chips are programmed assuming certain conditions exist, such as the use of high-octane fuel. These chips contain very few changes except for removing rev-limiters and governors that may have been present. These EPROMs replace the factory EPROM inside of an ECU. Replacement chips are typically one time use only; if you want to make a change you buy a new chip or send back your old one to be "re-flashed" by the chip manufacturer.
Before we get into talking about the three different categories of chip tuning, there are a few things to understand about how the engine management computer functions.
With a stock ECU, the manufacturer develops a map which is a compromised setting between all of the factors a manufacturer has to contend with. Typically, only two maps affect the performance of an engine – an ignition map and a fuel map – unless it is turbocharged, then there is a boost map as well.
"By and large, ‘chipping’ is limited to OBD1 vehicles. It doesn’t mean you can’t chip OBDII vehicles, but it mostly covers OBD1s," says Frank Smith, owner of South Florida Performance (SFP), Miami, FL. "The reason it is called chipping is because these ECUs came with an Amtel chip. It is a generic chip and you burn information onto it. It’s not a flash system either: you use a chip burner and burn the information directly onto the chip."
Once you get into OBDII vehicles, you’ll find you have to reflash the chips because these systems store information on a microprocessor. "The chips serialize themselves so that they cannot be copied and put into multiple cars (providing copyright protection for the chip tuner)," Smith points out about OBDII-type EPROMs.
The OEMs have OBDII access codes that allow the chip to be reflashed, but the OEMs are controlling the codes because they want to sell the updates to the aftermarket. Some engine tuners have essentially hacked their way into the chip to reflash it, but are also keeping their secrets to themselves, too.
Factory ECUs, according to several tuners, are surprisingly very good. However, they were not designed to do what tuners often want them to do. "When the stock computer was originally programmed, it was told it would see ‘X’ amount of maximum boost and when it sees more than that it doesn’t know what to do, so it turns a light on," says Smith.
ECUs make a 3-dimensional "map" to monitor engine performance. Each map consists of a spreadsheet-like table which designates how much fuel, timing and boost (if applicable), as well as other computer functions such as VTEC switchover points, should be used at a specific rpm and load. Factory maps are designed to trip a light anytime the inputs go outside of the values listed in the tables.
There are many companies making replacement chips that are modified but are not tuned to an individual car. The lower end of the chip spectrum tends to not show much performance gain, and may, in fact, cause the engine to lose power and throw the fuel economy off as well.
A slightly modified chip may have rev limiters raised or removed. Some chip manufacturers will remove speed governors, if there are any. And according to a couple of tuners we spoke with, these types of chips are programmed to dump fuel and add timing onto the stock maps.
However, some chips are designed for specific modifications such as cold air intakes and free flow exhaust systems and can show significant improvements over stock. But they will probably never be able to get the maximum performance out of a vehicle’s setup because these generic chips aren’t tuned with all of the variables unique to a specific car.
An engine builder can install this type of chip without having to use a dyno or learning to program a map. Some chip companies can even work with your specific modifications to help design a map for you.
There is only a handful of companies offering piggyback computers in the U.S. right now, but they’re becoming a popular choice among people who do both street and track driving. Essentially, a piggyback intercepts all of the signals going between the ECU and the engine control sensors. The signals are then manipulated in the piggybacks computer to send one set of signals to the engine and another (stock map) to the ECU. By doing this, the piggyback can remap the ECU without triggering a "check engine" light.
One of the benefits of a piggyback over a standalone system is that it uses the stock maps and simply modifies them. Therefore, you can keep the stock idle control and other settings you may want. According to UniChip’s Friedman, these systems usually employ fairly detailed mapping features. The UniChip has two ignition maps so that one can be set for a racing fuel when you are at the track. It can be switched between the two with a simple toggle switch.
ECU maps are tuned for two different settings: open loop and closed loop, which can be vastly different from each other.
"Open loop" is for full-throttle applications. In this mode, the O2 sensors are basically ignored and the fuel map is considerably richer for more power at wide-open throttle (WOT). For racing applications, this area is tuned the most. Open loop is also for cold engine operation as well as WOT. The ECU will remain in open loop until the coolant sensor tells it the engine has reached a certain temp and the O2 sensor is hot enough to generate a good signal.
"Closed loop" is controlled by the feedback from the O2 sensors sending signals to the ECU, autotuning itself. On stock systems these are generally good because manufacturers work hard to get the maximum fuel economy with the lowest emissions. Closed loop covers basically everything but full throttle.
"When programming a fuel map, think of an Excel spreadsheet. Across the top is your throttle load and down the side is your rpm," explains Friedman. "If you go all the way to the right hand column, that’s your WOT column. Your O2 sensor is ignored once the rpm reaches that column," he says, referring to the switch between closed loop and open loop. The fuel map will be much richer in this column than in the others, too.
"In closed loop, a good tuner is aiming for 14.7:1 stoichiometric pressure," explains Friedman. "At WOT (open loop) in a normally aspirated car you’re looking to tune around 12.1:1. In a forced induction car you will probably come down to 11.5:1 – much, much richer."
One of the differences between the piggybacks and the standalones is that standalones have been, until recently, primarily for racing applications. And in a racing environment correction factors are not programmed into the system. Typically the maps are only programmed for open loop and factors like humidity and altitude at the track are programmed for that particular day.
Piggybacks, however, work in conjunction with the factory maps. "It will remember, until it is reprogrammed, that it needs two degrees more than what the stock ECU says it needs," Friedman explains. "So, let’s say the stock ECU is programmed for 28 degrees and you add two more for a total of 30 degrees. The UniChip only knows that it is adding two degrees to the stock map."
Friedman explains further.
"Now, let’s say you drive to Denver to go to an autocross. Because of the altitude and temperature changes, the stock ECU now determines that it needs 25 degrees of advance. I’m still going to add two degrees to the 25 degrees for a total of 27 degrees because I’m tuning for the differential that the car needs from the stock map."
One of the difficulties with getting a standalone to run well for the street and the track is keeping within a certain temperature range. "If you’re within 10 degrees C (50 degrees F) or so, you’ll be alright, you’ll make decent power, says Friedman. "But if you design a map for 0 degrees C (32 degrees F) and you’re running it at 40 degrees C (104 degrees F), it’s not going to run very well. And what that really translates to is a car that is not a daily-driver/autocross-friendly type of vehicle. It’ll run great at wide open throttle. But it isn’t going to want to run when it goes to the street."
The standalones may also be a bit too expensive for the dual-use type of customer who may not need it. These systems can run $3,500 just for the hardware, according to Friedman. "Add the tune and installation cost and one these systems will probably end up costing $5,000 overall. They tend to work well within the limits of what you want them to do, especially if what you want them to do is race oriented."
The programmable standalone ECU has gotten to the point where it’s almost ridiculous. There’s almost as many companies making these units as there are companies making chips," says SFP’s Smith.
"The standalones are more complicated because I’d say around 95 percent of them don’t have a base map to start with," says Smith. "Which means YOU have to kind of know what your trigger angle is, and YOU have to know when certain events are happening.
"For instance, when is the TDC Hall effect signal happening so you can get the engine to fire right? Once you figure that out, you have to look at how many milliseconds do you want to hold the injector open at 1,000 rpm? And that may be just to get it to idle! What’s it going to take at full throttle? So there are countless calculations you have to make in order to get it to even run," Smith notes. "It’s like someone gives you a new computer with nothing on it. You have to load everything. It is complicated, but also more flexible in what it can do."
Some standalones, like that from AEM, have now started to include a basic set of maps as a starting point. The AEM system is also plug-n-play, which means it uses all the OE sensors and plugs into the factory wiring harness. Smith says he sells about 15 of these units a month.
"What AEM had to do to market them was install them in some of the more popular cars and come up with a base map. So when a consumer got one and installed it, the car would be able to run," Smith says.
Our experts say that being computer savvy doesn’t really mean a whole lot when it comes to tuning an engine well. "One thing has nothing to do with the other," Smith explains. "The first hurdle for some of the more computer oriented people is to get over that." For many engine builders, however, this scenario is reversed. Engine builders tend to be less computer oriented and often times shy away from computer technology.
But, as our experts attest, it is more important to know engines than to be a computer geek because once you get over understanding the technology, tuning is tuning. And an engine is still breathing in air, mixing it with fuel and burning it.
In the past, the standalones have been primarily used by the hardcore racers, but Smith says, more and more of these systems are being used for street applications every day. He says 95 percent of the engines he builds or tunes have either a piggyback or a standalone system installed.
Hondata in Torrance, CA, makes a standalone engine management system out of stock OBD1 Honda ECUs. Matt Wilimzig, operations manager at Hondata, says his company takes older generation computers and modifies them to be fully programmable. "One of the reasons Hondas have been so hot in the sport compact tuner market is because not only are its engines interchangeable, but the OBD1 EPROM is designed to accept external ROM (read only memory). Therefore, with a chip burner, tuners can burn a redesigned ROM image onto the EPROM, taking advantage of any engine modifications," he says.
According to Wilimzig, chip modifications on a stock engine will see some gains, but the big gains are made when engines have been modified. And Hondata can back this claim since it has programmed maps for some of the quickest Hondas in the world. One of Hondata’s customers set a landspeed record for a Honda Civic at 204 mph! Another benefit of the Hondata system according to Wilimzig is that it is one of the least expensive standalones on the market, and it is a scalable system. Base systems start at around $295 and go up to $725 for the stage 3 system with a tunable boost map.
Another important element to the ECU tuner is the dyno. Chassis dynos are critical in allowing the tuner to setup the ECU properly. There are two types of chassis dynos: a load dyno and an inertia dyno. For engine builders who want to think about ECU tuning there is a critical difference between these two types of dynos.
An inertial dyno is basically just a couple of drums that the car sits on. When you push the throttle, it accelerates. A loading dyno is equipped with some kind of mechanism that will apply a load to the rollers and will allow you to stabilize the car at a given point.
Many engine builders have dynos today but many of them are using engine dynos, which are great for most engine builders’ purposes. You can tune the ECU to a certain degree on an engine dyno, says UniChip’s Friedman and others.
But there are differences between dyno capabilities; engine dynos can’t simulate as closely how the total package is performing. Typically, an engine dyno is set up in a climate-controlled room, and you can’t simulate the same drive train losses as a chassis dyno can.
"One of the nice things from a tuning standpoint is: tuning is tuning is tuning," says Friedman. "Once I put a car on the dyno and I bring it up to 4,200 rpm and set the air/fuel ratio, I find that the car wants two degrees more timing than the stock ECU. I don’t know what the stock ECU is set at and I don’t care. What I am concerned with is what I have to add to it to make it perform better?"
When the vehicle goes on the dyno the tuner runs the car up to the 4,200 rpm load point. On some piggybacks and standalones, there are at least 16 individual tuning points with 16 tuning points in between for a total of 256 tuning points. The tuner then increases the load on the inertial dyno so it reads 4,200 rpm at full throttle and adjusts the ECU at that point. The air fuel ratio will be set and the ignition map will be set to the optimum timing for that point. Then, the tuner will go to the next load point, which we’ll say is 4,800 rpm, and do the same thing. This is what is called "real-time" tuning.
According to Friedman, tuning in "real-time" on an inertial dyno is critical in being able get every ounce of performance from the engine and ECU combination. "The people who can’t access a detailed map don’t do [real-time] tuning. They will sit at idle on the dyno, go from idle to redline to see how much power they have, come back to idle, then make an adjustment everywhere and then go idle to redline again. Our system and systems similar to ours don’t do that. We are tuning the engine perfectly at each load and rpm point."
Many engine builders are already working closely with chip tuners to get the most from their performance engines. Some engine builders, like South Florida Performance, are doing engine building and tuning as well as selling the ECU as complete packages. In the sport compact market, it is becoming a necessity to tune as well as build.
"Engine builders are going to have to look at this technology sooner or later," says SFP’s Smith. "Now, even the domestic market is shifting. It has gone to EFI, so you have to know your way around the electronics to be successful."
For performance engine builders there is no denying that the carburetor’s days are numbered. The ECU can do thousands of "tune-ups" for every second the engine is running. And with a computer, tuners can more accurately tune to the conditions and make drastic changes without much more than a few keystrokes.
More street rods, and especially the sport compact crowd, are tuning electronically than ever before. Several racing series now allow some form of EFI, which means there is an ECU that will, no doubt, need tuned by someone. And that someone could be you!