This will not be another attempt to convince those committed to carburetion that modern electronic fuel injection is really the way to go. As a CHP reader and a well-informed gearhead, you already know the pros and cons of each approach. Sure, we'll state the advantages of EFI as part of our discussion. But instead of making a case for fuel injection, we want to look at the issues in one particular case. The snags we encountered while installing and dialing-in an Edelbrock Pro-Flo multipoint electronic fuel injection system are common trip-ups. We hope to help you avoid a few of them and demonstrate what a sorted-out install can do on the dyno.
Doin' It Anyway
OK, we can't help but do a little sermonizing. A correctly installed and set-up electronic fuel injection system has a host of benefits over a tried and true carburetor. Chief among them is improved economy. "Even compared to a perfectly tuned carb," says Edelbrock's Terry Abercrombie, "you're still gonna gain 10-12 percent." That's the bottom line, but an EFI system also improves drivability and cold and hot starting, and it won't be fazed by elevation changes. "And after installation is done," Abercrombie added, "Most EFI systems give you less problems. They're self-cleaning and won't easily degrade your tune-up."
So why do so many enthusiasts stick with carburetors? Sure, traditional mixers have been around for more than a century, and the average wrench is comfortable while dealing with them. And there is the cost factor-a carb is still much less expensive than an EFI setup. But Abercrombie expressed his reasoning plainly: "They're afraid of electronics." And before you bristle at the mention of a fear factor, he added, "As we all are. When Edelbrock first told me I was gonna have to deal with this stuff, I said 'Give me a carb any day.'" Now Abercrombie's most likely the guy you'll end up talking to when you call Edelbrock's EFI tech line.
Let's cut to the chase-if a vehicle's electrical system isn't working well enough to support a new Pro-Flo system, the high-tech squirter isn't going to work properly. It's a simple truth that many who install any new EFI system into an old Chevy overlook. "The big thing is the charging system," Abercrombie started off. "It was common for pre-'82 to come with 40- to 60-amp alternators. The output of newer vehicles (almost all of which are fuel injected) is 140 amps. The big thing to do with all older vehicles before installing this system is verify that you have a minimum of 60 amps."
Then again, the other aspects of an automotive electrical system-battery power and grounds-are also crucial. Abercrombie warned us about dragging starters and poor grounds. "All the power and ground leads on an older vehicle need to be pulled apart, cleaned, checked, and replaced if necessary. It's a big problem with all fuel injection." And lest you think your Chevy doesn't fall into the "old" category, he related a short tale: "We had probs with a '94 MPFI car; well, those are 15 years old now, and the ground strap was split.
"The system needs between 13.8 and 14.2 volts to run properly," he continued. "When going down the road, every little bit below 12.5 volts gives incorrect info to the sensors, creating a bad return path." In other words, you don't reap the benefits of running in closed-loop mode, which is part of the reason for installing an EFI system, since this is where the computer runs the motor at peak efficiency. "Below 11 volts," Aber-crombie concluded, "it's gonna run stinko."
Although we won't be showing you this ordeal, we can testify that Abercrombie's advice is right on, since we had all three of these problems with our subject Biscayne. We replaced a sorely inadequate positive battery cable just to get the starter cranking as it should, made a trip to the local parts house for a new alternator, and went on an extensive ground strap R&R hunt. Save yourself some aggravation and address these issues before you start installing an EFI system. And one last tip from Abercrombie: "Any engine that's in a bad state of repair...it's not the way to go."
Dialing It In
Each Pro-Flo comes with an individualized chip in its ECM loaded with dedicated fuel and spark curves for a specific application. In this case, our 502 crate motor had been fitted with a smaller-than-stock cam: .510 lift, 212/218 duration, 114 lobe separation. Edelbrock sent along a PN 3552 chip, usually intended for 454ci ig-blocks. If you use one of Edelbrock's recommended cams, getting the chip is easy. Getting the proper chip is the first critical step in punching up a slick-running EFI motor.
The advantage of the Pro-Flo system is the handheld calibration module, which allows the owner to customize the fuel and spark maps as needed-if the chip is close, the calibration module is the road to spot on. We won't go through the exten-sive Edelbrock instruction manual for you; instead, we'll summarize Abercrombie's quick course in tuning the Pro-Flo in the accompanying sidebar. With that, we'll let the Biscuit's owner have the last word: "It takes a little to get [the Pro-Flo] dialed in, but the car is now very responsive. It idles comfortably, doesn't surge, and has great midrange. The throttle response is great." Check out the details of how we got there-and got 390 hp and 530 lb-ft at the wheels, even with the tiny bump-stick.
Top 5 EFI Mistakes
4.Poor vacuum (will have trouble with closed loop under 10 inches)
5.Trying to tune without a partner
Top 5 EFI Tuning Tips
1.Have a partner drive the vehicle or do tuning.
2.Ask questions, and don't be afraid to call the tech line.
3.Some shops are good, some I'd never go to.
4.Be aware of where problems are, and tune for those problems.
5.Surround and conquer.
Surround And Conquer
We like to keep things simple, and so does Edelbrock's Terry Abercrombie. After years of answering calls from Pro-Flo users, he boiled the tuning section of the full manual down to one page. Simply titled "Pro-Flo Tuning Guide," this valuable page starts by explaining that there are 24 fuel cells a user can tune to get "a clean and powerful engine." There are six rpm levels; each can be tuned at four vacuum levels, thus 24 cells. This in itself should take much of the mystery out of tuning the Pro-Flo system. But Abercrombie goes on to outline a method for getting the tuning done, starting with completing the idle tune-up, then driving the vehicle to find problem areas, identified by the simple indicator light on the calibration unit. Red is lean, green is rich, and yellow means you nailed it. Fuel can be added or subtracted where needed. Envisioning the fuel table as a graph does more than simplify the process-it also provides a framework for dialing the system in. Here's Abercrombie's example: Say you have a lean condition at 2,500 rpm at 15 inches of vacuum. The key to fixing this problem is to tune the four boxes around the problem spot. For example, 2,000 rpm, 12 inches; 2,000 rpm, 18 inches; 3,000 rpm, 12 inches; 3,000 rpm, 18 inches. Surround and conquer, and you'll get it dialed in. If all else fails, call. "That's what we're here for," Abercrombie says. In fact, he'll even hook you up with other Pro-Flo users in your area, most of whom are happy to help. "We do it on a weekly basis," he told us.