Part Twelve: More Electrical Current
While some might think getting twelve separate articles out of one project might be a challenge, you’ve got to consider the starting point of that project and the final end goal. Take Project Obsessed for example here, when we took ownership of this 1996 Ford F350 last year, it was basically stock with nothing more than a 20-year old flash tuner, some outdated cosmetic upgrades and a terribly riding front leveling kit. The old 7.3L Power Stroke under the hood was still running strong with 224,000 miles on it, but like the rest of the truck needed quite a bit of attention if it had any aspirations of hanging with a new 400+ horsepower 6.7L Power Stroke.
Now over a year into the build and upgrades we find ourselves well past our 450-horsepower goal thanks to some bigger injectors, a modified turbocharger, electric fuel system and a host of other bolt-ons. We’ve been able to keep the classic look with some newer front fascia pieces and we improved the ride quality with a Reverse Shackle and Super-Duty leaf spring swap on the front axle. Really, with a whole lot of elbow grease, countless hours in the garage and more dollars than you’d dare tell your wife you’ve spent, this old Ford is about the nicest one on the block. With all that said, we still aren’t quite finished with the build and still have a few planned upgrades, including some brake and cooling system upgrades next month. This time, we’re focusing on the electrical system, installing an all new gear reduction starter and high output alternator along with a high voltage high current Injector Driver Module.
With all new injectors and an electric fuel system running dual factory Super Duty fuel pumps, we wanted to make sure the electrical system was up to snuff. Not knowing the history on the components on the truck (like the alternator that appeared to be the original from 1996) making some updates just seemed like an easy choice for this build. We weren’t willing to spare expenses anywhere else along the way, so why fall short on the electrical system? We are going to be traveling far from home, towing throughout the year, so it’s a nice piece of mind knowing an old starter or alternator won’t leave you stranded somewhere.
The high output starter from Xtreme Diesel offers a 200-amp output which is a substantial improvement over the factory unit and will ensure we have enough power to run any aftermarket components like those new fuel pumps and our mildly pumped out stereo system. As an added bonus, XDP uses stealthy black wrinkle coat on the alternator that looked incredible under the hood next to our textured black intercooler piping. XDP also tests their alternators during the assembly process to ensure they work as they should before shipping, offer a full 1-year warranty and because they are brand new units, there is no core required.
Like the alternator, XDP also did their homework when it came to their gear reduction starters for the 7.3L Power Stroke application. The smaller motor on the starter not only spins faster than a factory replacement would, but it’s more efficient and draws less amperage. With the gear reduction within the starter, it offers a much higher torque to spin over that big engine even though it’s about 1/3 the size. Matching the alternator, it also comes coated in a black wrinkle coat for good looks and better corrosion resistance and has that same one year warranty.
Going back a few months on this build, you’ll remember that we installed a new set of injectors from Full Force Diesel. We had opted for their 205cc hybrid injector with a 30% nozzle size, which they had recommended for our application. It would offer great towing performance, with low smoke output and easy EGT control, while having enough fuel to support upwards of 450 rear wheel horsepower. Looking to give those injectors the best chance at efficiency and complete the final piece of our ‘performance’ puzzle we turned to Diesel Technology of Chattanooga (DTC). Owner, Johnathon Ryan, has been in the 7.3L game just about as long as anyone, and has seen just about everything under the sun when it comes to this engine platform. His knowledge of the engine, how it works and what makes it work better will impress you after just a matter of minutes talking with him. We’ll use direct quotes from him to explain how the IDM works and what they do to improve it:
“The Injector Driver Module (IDM) is just an electrical box, computer, that fires the injectors in response to commands from the Powertrain Control Module (PCM). The IDM uses a Peak-and-Hold method to control the current to the injectors. During the ‘Peak’ period, it supplies full current to the injector solenoid so it experiences the maximum electromagnetic field to fully open the injector’s poppet valve to fire the injector. A factory IDM should start at 112-volts and peak for 525 microseconds, as that capacitor discharges the voltage will drop to around 93-volts at the end of its peak. The IDM then begins to rapidly switch the current to the injector on/off at 12-15kHz, this is the ‘Hold’ portion of the process as it holds the injector open. 400-microseconds after the peak has ended, there is a break gap in the holding pulses. That break gap is a non-intentional design parameter within the circuits design. If that ‘gap’ period is short enough, the IDM works as it should.
Average gap time ranges from 125-150 microseconds on a standard 120-volt IDM but can increase as the IDM gets older and starts to get tired. If that gap grows to over 300-microseconds, injector performance will start to suffer and even misfire. At 400-microseoncds, the gap is actually longer than the actual injector turn on time and the IDM won’t have the energy to turn the injector on.”
We opted to send in the IDM from Project Obsessed to be tested, rebuilt, and upgraded so we could compare data before and after. Ryan has been working on IDM’s since the early 2000’s, so you can be sure he knows what to look for and has the knowledge and experience needed in such a daunting looking computer piece. Our gap tested at 364-microseconds, which is on the weaker side, but common for the 1994-1997 model year trucks. At this point, DTC started the rebuild process where they replace 15-20 components within the IDM to make sure its back up to snuff and ready to go for thousands of trouble free miles. Once completed, the IDM is run through 13 different tests to ensure it’s working as good or better than when it was brand new.
Now, onto the upgrades for the IDM. DTC first makes some adjustments to increase the voltage to 140V, which has been a popular modification since 2004. While increasing the voltage output by itself can increase injector performance, DTC also performs some upgrades within the IDM to increase the current. By making both voltage and current changes, they can ensure the IDM is sending the strongest and most efficient signal to the injectors so the injector can maximize on-time and injector pulse width duration. The IDM is then tested on a running engine for 60 minutes at 3000-rpm and 3.0 milliseconds of injector pulse width. If you were to run your engine that hard in the truck, you’d melt pistons for sure. These tests ensure the IDM will hold up to the sustained heat and demand from towing applications.
While a modified IDM isn’t going to make a massive improvement in power or performance, with the level of modifications done to this truck and the age of the factory IDM, these are changes that will be noticed. After driving the truck, we did experience a better idle and significantly better throttle response. The engine feels and sounds healthier and has a peppiness that’s hard to describe without driving it. The high voltage high current IDM pretty much rounds out our performance upgrades on the old truck, and we’re super happy with drivability from the truck. Next month we’ll upgrade the cooling system and brakes to handle the abuse of heavy towing a little better.