By Staff Writer
Nov 11, 2008 | Posted in Electronics & Electrical Systems | From the Oct. 2005 issue | Never miss an article

Story By Per Schroeder

Let’s talk about The Man. Whether he’s the government or those large, fat-cat corporations that make the world go around, The Man is a pretty easy guy to hate. Who doesn’t like the idea of sticking it to him?

If the little guy can do it faster, cheaper and better than the big shots, who’s to blame us for cheering for the underdog? This indelible bit of human psyche has spawned the hardcore followings of everything from indie rock to Unix operating systems. It’s part of our country’s very fiber, as we started out as the underdogs some 229 years ago.

The Man’s long reach seems to extend into every nook and cranny of modern life—even the automotive enthusiast market. We’ve all see the ads from the large, impersonal parts supply houses, or the occasional high-end vendors charging astronomical prices for parts that simply don’t work. The Man is everywhere.

Fortunately the underdog ethos is alive and well today in the world of GRM, aided by the Internet and the culture (or counterculture) of online message board communities. In the technical and automotive Web-based communities, the “open” nature of the Internet allows the posting and sharing of information and lessons learned.

Technical support and essentially free help for the enthusiast are just a click or two away as fellow gearheads chip in their knowledge and skills to keep repair bills low. Racers can also learn a lot online about how to make their cars faster without breaking the bank.

One shining example of the online community’s value to the car geek is the MegaSquirt do-it-yourself fuel injection system. This standalone, easily modifiable EFI system is completely user-serviceable thanks to its open architecture and low-cost design.

In this case, the term “open” refers to the fact that the entire set of schematics, wiring diagrams and building instructions are available online, completely free of charge. These plans allow users to build a working EFI computer for less than $150, which is an order of magnitude less than the price of the common aftermarket, ready-built systems.

MegaSquirt also boasts a technical support network that is unrivaled in the aftermarket, with thousands of private individuals posting online to help with setup and troubleshooting. There are also dozens of add-on computer programs that have been developed to help the MegaSquirt user tune their car to its potential.

The appeal of the MegaSquirt system goes well beyond the simple desire to stick it to The Man. Your car’s intake system, whether carbureted or fuel injected, is an integral piece of the performance puzzle, and this is one area where the aftermarket has a wide variety of solutions for more power. Adding fuel injection will often improve both horsepower numbers and fuel efficiency, but prices for these aftermarket stand-alone systems can top $2000 or even $3000.

These prebuilt systems are also often designed to use proprietary tuning software, adding further expense to the average enthusiast’s bill. What if we told you that MegaSquirt can do the same things for less money?

MegaSquirt: A History

The lion’s share of the development of MegaSquirt is credited to two men, Bruce Bowling and Al Grippo. As Grippo explains, the development of the fuel injection system began about 12 years ago thanks to a do-it-yourself fuel injection Internet list started by a graduate student at Ohio State University.

The group, which was quite small by present standards, was discussing how to make a fuel injection board using a 32-bit Motorola MC68332 processor. “This was quite an advanced system at the time, well beyond what the OEMs were using,” Grippo explains.

There was a lot of talk on the list, but nobody was doing anything. Bowling and Grippo decided to take the lead and produce a working system. Their software was written for their own cars, however, and they hadn’t given any thought to making it user-friendly or providing tech support.

“The only reason we even sold a batch of PCBs [printed circuit boards] was to recover the $300 we had to invest to get a run of four-layer boards,” Grippo recalls. “We recovered that and more, but almost all of the people who bought them soon realized that getting it to work for their setup was more work than they were willing or able to [do].”

Several years later, processors became cheaper and integrated with more memory, with both timers and sensor ports being built right into them.

“So one day, out of the blue, Bruce tells me that he developed a really low-end, bare-bones, fuel-control-only EFI system that we could sell at a really low price,” Grippo continues. “I scoffed, but Bruce went on to document the system and develop a user-friendly PC interface. It was ready to go, so I went along, still somewhat skeptical. That was the start of MegaSquirt.”

Through their Web site’s message board and its list members, Bowling and Grippo have developed the MegaSquirt system to the point where it is simple to build, tune and run. They also offer low-priced kits so that anyone can assemble their own fuel injection system.

Okay, Sign Us Up

The first step in the conversion was to remove the carburetors and bolt on the intake manifold. We labeled the ports on the manifold with a marker to make things a little easier to remember.

Here at GRM, we’re down with the cause of the underdog, and we hope it shows in what we build and write about. Our message boards are chock-full of MegaSquirt references, and quite a few of the cars that we’ve profiled in the magazine have been injected by Bowling and Grippo’s baby. We even named the MegaSquirt system as one of our Editor’s Choice recipients for 2004.

So it’s about time we put the system on one of our own cars.

But first, we had an important question to answer: build or buy? While part of the beauty of the MegaSquirt fuel injection is that it is truly a do-it-yourself endeavor, we figured that hooking up with someone who already possessed Jedi-like skills with the system would help get us on the road quicker.

Steve Berry would be our Jedi Master, even though he hails from Charlotte, not the Jedi’s home base of Coruscant. Steve has built several MegaSquirt systems for vintage Volvos and has documented them on his Web site. In addition, he has started selling preassembled kits for the vintage Swedes at an attractive price.

Steve has the MegaSquirt ECUs and their power relay boards assembled from parts that can be sourced from Bowling and Grippo. We couldn’t argue with the idea of professional and well-executed circuit boards—complete with screen-printed markings for easy hookup, by the way—that come in a custom-machined housing. While we can wield a soldering iron for normal wiring tasks, building a fairly intricate circuit board that could be trusted for extended daily driving and long trips was something we felt more comfortable letting a professional engineer handle.

This didn’t add a lot to the cost of this installation. In fact, the professionally assembled MegaSquirt ECU only cost us $250; the power relay board ran another $90. Considering how long it would have taken us to make these parts and how painless the installation process is thanks to the prebuilt components, we think we made the right decision.

If you want to save some dough and need to do everything yourself, assembling these two components can save you about $100 for the pair. “Building your own ECU is half the fun—makes it that much cooler when the motor fires up,” Steve says. “Like the difference between assembling your own short block or buying a crate motor. If you screw up, you are out $150, instead of $2000.”

Our Test Mule

In order to provide some real-world data, we needed a test mule for our MegaSquirt injection system. Our Classic Motorsports 1969 Volvo 142S would be the perfect car for the task.

Our car originally came equipped with Zenith Stromberg carburetors. Like the ever-popular SU, the Strombergs use the variable venturi design to vary fuel delivery depending on load and rpm. Unfortunately, the Strombergs are saddled with archaic emissions control devices like thermostatic mixture regulators and the like.

Ours were well past shady when we bought the car, and we replaced them early on in the project with a pair of SU HS6 carburetors from an earlier Volvo that had been rebuilt by Carl Heideman at Eclectic Motorworks. We drove the car for several months in this configuration, with some success in tuning the SUs for decent power and mileage.

When our original carbureted B20B engine started going south after a long highway trip, we purchased a complete, but worn-out B20E from a 1971 142 as the basis of a performance rebuild. For $200, we got the engine and a truckload of parts, including many of the items that we needed to convert our car to fuel injection, like the intake manifold, injectors and even the fuel tank with return line fitting. (The B20E came from the factory sporting injection.)

Volvo had already done a fair amount of the hard work for us on this conversion, as they offered several of their pushrod B20-powered cars with Bosch’s D-Jetronic fuel injection. This MAP-based system allowed for strong performance and decent gas mileage—when it was working correctly. Primitive fuel maps and fragile sensors have given the D-Jet a bad rap in the vintage Volvo community, but they are still being used by some very fast racers in the SCCA’s Improved Touring B class.

Our B20E rebuild was a straightforward balance and blueprint job. Only offered for 1970 and 1971, the B20E features a higher 10.5:1 compression ratio, larger intake valves and ports for fuel injectors. It was Volvo’s hottest pushrod engine.

Once we had the engine rebuilt and back in our 142, we bolted on the rebuilt SUs as an interim step. The injector ports were sealed with 7/8-inch freeze plugs that we pressed into the head. A little RTV sealed the ports without damaging them.

Before we started on the fuel injection installation, we rolled the carbureted Volvo 142S onto the Dynojet chassis dynamometer at BNO Performance in Edgewater, Fla. The fresh B20E with SUs struggled to churn out 93 horsepower at the rear wheels. According to our Innovate Motorsports wide-band oxygen sensor, the mixture was a little lean at the top end and the power rapidly dropped off after 5500 rpm.

While some tuning of the SUs could be accomplished with different needles, we weren’t sure if we could get the right set without scores of needles (at $20 a pair) and lots of dyno time (at $70 an hour). We played around with the base mixture setting and found that without some drastic changes, the horsepower wasn’t going to miraculously improve. Messing around with the base mixture also severely compromised the idle quality, with best idle being way too lean for performance use.

One of the major reasons for our fuel injection conversion is that carburetors can, simply put, just stink. At times there was a miasmic cloud of gasoline vapor in the engine compartment. The SUs atomize the fuel just a few centimeters from the open-element air cleaner, and this haze can be smelled, even from the cockpit of the car.

In fact, many times we’d get out of the car after even after a short drive, smelling like gas fumes. Despite a correctly set float level and a lean mixture, the carbs were simply too “vintage” for us.

We decided to install a MegaSquirt system on the Volvo as a way to make our daily driven car even more capable in its multipurpose nature. We wanted better performance, increased fuel mileage, less hassle and no more fuel stench.

The Basics of MegaSquirt

The power relay board supplies the ECU with its power and signals from the various sensors like the Volvo 850 TPS we mated to the factory throttle body.

Like an original-equipment-type fuel injection system, the MegaSquirt ECU uses data from various sensors to determine how and when the injectors should be opened. Before making any decisions, the MegaSquirt receives information regarding manifold absolute pressure, throttle position, coolant temperature and intake air temperature. Additionally, an rpm signal is taken from the ignition system.

These signals are received by the power relay board and then passed along to the ECU. We mounted the power relay board under the hood, while the ECU was placed inside the passenger compartment. A thick relay cable links the two components.

The ECU then takes this data and figures out when and how long to fire the banks of injectors. (Our design paired together cylinders 1 and 4, and 2 and 3.) The relay board also powers the fuel pump when the ignition switch is turned on.

Each sensor provides a different piece of the puzzle that is required to produce a functioning fuel injection system. While you may be on your own when designing a MegaSquirt system, understanding what each component does and how it is incorporated into the system is usually more than half of the battle.

The manifold air absolute pressure sensor (MAP) tells the computer how much vacuum is in the intake manifold at any given point. Originally, our D-Jet setup used a fragile MAP sensor that was about the size and shape of a hand grenade—and about as touchy.

Now we’re using a nearly bulletproof MAP sensor that is soldered directly to the motherboard of the ECU. A small vacuum line runs from the intake manifold into the cockpit where the ECU is mounted.

The throttle position sensor (TPS) tells the ECU when the driver is getting on the gas. The ECU uses the variable resistance signal that the TPS provides to give the engine additional enrichment. Our throttle position sensor is from a 1995 Volvo 850. We modified the base plate of the original D-Jet TPS to fit the 850 switch. The throttle position sensor set us back $55.

We used a $25 GM intake air temperature (IAT) sensor. The IAT sensor screws into a hole that we drilled in our intake tract, just before the throttle body.

Our B20E head came with a Bosch coolant sensor that we used to get engine temperature data for the ECU. Like the IAT sensor, the coolant temperature function is simply a modifier for the data that the ECU is getting from the tach signal and the MAP sensor. When it’s reading cold, the mixture is enriched accordingly.

The MegaSquirt ECU is actually configured to use a GM sensor that would give a different temperature/resistance curve than the Bosch piece that we used. This means that we needed to have a conversion formula in the tuning program. We used a program called EasyTherm. Like all of the computer programs mentioned in this article, EasyTherm can be downloaded for free from a number of MegaSquirt sites.

Instead of hacking up the intact, but nasty, D-Jet harness that came with our engine, the wiring for the fuel injection was built from scratch. The sensors were hooked up to the power relay board with new connectors and automotive-grade wiring and protective boots. This step added about $85 to the conversion, while a serial cable that connects the relay board to the ECU added another $45 to the total bill.

During this conversion, we switched out the original points-based ignition for a PerTronix optical ignitor and an MSD 6a capacitive discharge ignition. Because the MegaSquirt ECU relies on a tach signal to do its calculations, we wanted to provide the cleanest signal possible. The combination of the Hall effect trigger provided by the PerTronix ignitor and the MSD 6A ignition box with tach output makes a nice, clean 12-volt square-wave signal that allows our ECU to properly do its dirty work.

We mounted the Pertronix ignitor into a spare Volvo 1800 cast-iron distributor, a 003-type unit with about 22 degrees of advance in the “can.” This swap was necessary because our 142 came with one of the few Bosch distributors that isn’t compatible with any of the PerTronix triggers.

The red wire is fed by 12-volt switched ignition, and the black wire is the trigger signal for our MSD box. A tach signal connection on the side of the MSD 6A box was then connected to the tach connection on our MegaSquirt power relay board.

The PerTronix ignitor and MSD 6A box are not absolutely necessary for the MegaSquirt installation, but they do make life easier in the long run as the ECU relies on the tach signal for all of its high-speed calculations. Since our core engine came with the intake manifold, throttle body and injectors needed for our MegaSquirt transformation, these parts were simply cleaned up and bolted onto the fresh engine. Lucky for us, the B20E cylinder head has the cast-in injector ports and mounting bosses, so all we needed to do was remove the previously installed 7/8-inch freeze plugs and bolt in the injectors. The stock 36 lbs./hr. Bosch injectors can handle up to 200 horsepower, which is more than we are ever expecting to get out of our Swedish tractor. (For more on fuel injector sizing, check out the May 2004 issue of GRM.)

There was one final step before our car could be injected: Our fuel system still needed to be updated. We drained and removed the factory gas tank and bolted in the one that came with our core engine. The new tank has a second fitting for the return; this was plumbed with 5/16-inch fuel line, which was routed and clamped underneath the car, running parallel to the original supply line.

We then installed a new high-pressure electric fuel pump that we sourced from an eBay vendor for $100. This was bolted to the side of the fuel tank in the stock 142E location.

MegaSquirt Tuning

Steve Berry wields his Jedi skills on the laptop. He’s using MegaTune, a Windows-based application that helps tune the MegaSquirt ECU. Fuel maps are simply look-up tables that are uploaded to the ECU.

MegaTune is the open source (and, once again, free) Windows-based application used for tuning MegaSquirt. The design is easy, intuitive and very well documented. It’s solid as a rock, yet purposely designed to run on some of the slowest laptops you can dig up on eBay.

Like other examples of well-built, open-source software, it works well; it’s also as powerful as any proprietary tuning software on the market. Eric Fahlgren, the designer of MegaTune, is constantly improving the software in response to the requirements of the hardware designers and requests from users.

We programmed our Innovate Motorsports wide-band oxygen sensor to produce an analog signal between zero and 5 volts depending on the air/fuel ratio. This signal was then fed through our MegaSquirt ECU and into the laptop for data logging in MegaTune. This made tuning painless and guess-free.

There is a Unix equivalent of MegaTune; written from scratch, it’s called MegaTunix and is designed for use with Apple and Linux operating systems. This excellent program has helped fill in the gaps for people who don’t have or want Windows-based laptops.

Others have made important software contributions to the MegaSquirt project. MegaTweak is a program that takes MegaSquirt data logs and does some serious statistical analysis of what an engine is doing, essentially tuning your car for you. MSLV (MegaSquirt Log Viewer) is another application that uses data logs to play back driving sessions like a movie, helping the right-brainers visualize what MegaSquirt actually does.

Steve Berry, our Volvo and MegaSquirt expert, likes the sharing nature demonstrated by those involved in the project. “These are some great examples of how an open community adapts and fulfills the needs of its users with no profit motive in sight,” he says. “This kind of hippy ‘gift culture’ may seem strange to anyone not familiar with the open-source movement, but the end results speak for themselves.”

Once we had MegaTune loaded on an old laptop, we plugged into the MegaSquirt ECU and started programming the basic settings. One concept that is used in MegaSquirt tuning is the VE table. VE stands for Volumetric Efficiency, a representation of cylinder filling in relation to manifold pressure.

This table is used to measure how much fuel the engine needs to optimally run. In this case, we use a table that has rpm on one axis and manifold absolute pressure on the other axis. These are the chart coordinates, or bins, that the ECU looks to when the rpm signal reaches X and the MAP sensor reaches Y. The chart coordinate tells the ECU how much fuel is needed.

Our idle VE bins are around 29 percent (MAP of 30kpa, rpm of 1000), and wide-open throttle near redline is 86 percent (90kpa, 6300 rpm). To go a touch richer at a MAP point, we would increase the VE percentage for this bin; conversely, we would drop it a percentage to go leaner.

The online community has literally thousands of sample VE tables stored for builders to use and tweak on their own cars, so there’s probably one for a car similar to yours out there somewhere. We punched in VE table No. 1, which was developed by Steve Berry for his Volvo 1800:

Original VE No. 1

First Round of Data Logging and MegaTweak

With our Innovate Motorsports wide-band oxygen sensor plugged in and feeding into MegaTune on the laptop, we turned on the data logging function and went for a drive in the country and around town. This data was then plugged into the MegaTweak algorithm, which generated a new VE table for us to try. You’ll notice that it changed the high-rpm bins so that we’re getting more precise amounts of fuel in these ranges.

VE No. 2

Baseline Dyno Results

Here’s a good look at why we converted to MegaSquirt. The dynamometer curves were extremely choppy and the Volvo struggled to make power over 4500 rpm with SU carburetors.

Our first shot at the dynamometer with the MegaSquirt installed yielded a decent, but not impressive, 102.8 horsepower at the rear wheels along with a smoother and less pungent idle. Even though this was already 10 horsepower higher than our best numbers generated with the SU carburetors, we knew we could produce more power.

We then sat in the passenger seat and watched the air/fuel curve as indicated by the wide-band oxygen sensor as the car was accelerating at full throttle. It started going lean after about 3000 rpm at full throttle. Once the car was back at idle and running, we quickly bumped up the fuel levels in the full-throttle portions of the VE table. We then used several acceleration bursts on the dyno rollers to confirm that we had gotten the air/fuel curve correct. VE No. 3 is the curve after our dyno tuning.

The final dynamometer pull for the day indicated a peak of 117 horsepower and a much stronger mid-range curve. The results were very encouraging, as Improved Touring-spec 142s are typically in the low-120 horsepower range—and that’s with race gas, tweaked D-Jet injection, headers and a short race exhaust.

Once the car was off the dyno rollers, we drove it around for several weeks, getting used to its newfound power. We decided to run some more data logging to further flesh out the part- and mid-throttle portions of the VE table in order to get the car running even more seamlessly.

Truth be told, the car was now light years better, in terms of both drivability and power, than any carbureted Volvo that we’ve driven, but we wanted to see how good the 142 really could be.

With the data logging turned back on, we went for another long drive, varying load, rpm and throttle position for nearly 45 minutes. This data was then plugged back into MegaTune for another go-round. This time, only incremental changes were spit out (see VE No. 4), but the difference in around-town and relaxed cruising is amazing. This car feels like it was tuned by a team of engineers with thick accents and funny names.

The Future of MegaSquirt

Although MegaSquirt was obviously well designed, as shown by all the new features people have added since its inception, the processor is a minimal 8-bit one that is nearing the end of its expansion capability.

To answer the need for more power and capability, Bowling and Grippo have developed MegaSquirt-II, which uses a 16-bit processor with three times the speed of the original MegaSquirt and a lot more memory. This processor is easily capable of accurately handling spark control as well as fuel and idle speed control.

It is also large enough to increase the number and size of tuning tables for fuel (including tables for two sets of injectors), spark and wide-band oxygen air/fuel targets, all as a function of rpm and air pressure. According to Bowling, “the nicest thing about MegaSquirt-II is that the processor and some additional hardware were laid out using surface-mount technology so they fit on a small daughterboard, which can be plugged into the existing processor sockets on the old MegaSquirt boards.”

Upgrading from old to new won’t be too hard, says Bowling: “All that is required is to wire in spark and idle motor, if you want these, and you have upgraded your system to MegaSquirt-II, no other wiring changes required.”

The future of MegaSquirt is just around the corner, Grippo adds. “We have finished beta testing of the MegaSquirt-II board and we are expecting the first production run to arrive any day now. When they do, we will start selling them and users are chomping at the bit to start adding a new round of improvements.”

Like the original MegaSquirt, Grippo sees the basic MegaSquirt-II architecture as only a starting block for the DIY tuner. “We will see how far the users take these,” he says. “We know there are people out there making transmission controllers, traction control boards, and who knows what else that can easily interface with MegaSquirt-II. We, ourselves, have a pretty sophisticated wide-band O2 controller that we can throw into the mix.”

Bowling adds that the new system will maintain the MegaSquirt traditions: “Our philosophy will continue to be open source development, fair prices, and continuous incremental improvement.”

The Man should consider himself stuck.

Digital Hippies: The MegaSquirt Online Community

As we’ve mentioned, there are two things that make MegaSquirt different from other systems on the market: It’s really cheap, and the architecture was made open, including the board design and all of the software code needed to make everything run.

Bruce Bowling credits the online user group for MegaSquirt’s success. “It went way beyond the tech support that any ‘real’ business could provide,” he explains. “People who learned the hard way were able to pass on their knowledge to newcomers, and the breadth of the group, including a very large global contingent, probably 30 percent of users, allowed us to extend the system to all manner of cars, some of which we never even heard of when we started.”

Much to Bowling and Grippo’s pleasure, the MegaSquirt idea quickly took off. “Almost as soon as the group began, the open-source nature of MegaSquirt inspired people to make improvements on their own,” Grippo proudly admits. “The documentation and user interface were vastly improved by volunteers, and then people began developing their own code to do things like control turbo wastegates and cooling fans, and this process eventually led to a version that also controlled spark, something which was never intended in the original design.”

Improvements were often initiated by a message board query asking if something could be done. Within a few days or weeks, they were given new code to test. “It was truly amazing,” he adds.

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View comments on the GRM forums
gearheadE30 New Reader
11/12/14 7:20 a.m.

Megasquirt FTW. The E30 has been running it for close to 80k miles now, and the Caprice is about to get MS as well. Seems to be a lot of people out there who are convinced that it is 'project cars only' and can't be reliable for everyday stuff, but that's not true at all.

spin_out Reader
11/12/14 7:23 a.m.

Well thanks Per. The post is too long for me to read now, but i printed it to read later.

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