XT Plus with its laptop interface...
XT Plus with its laptop interface is all the electronic engine control most of us will ever need. This screen shot of an XT Plus spark table illustrates its intuitive combination of charts and graphs.
Roberts recalls the XT head flowing about 270 cfm at .600-inch lift, with a peak exhaust flow of maybe 220 cfm. Perhaps more importantly, "It's not just peak numbers, the valve job is better than before. We put four or five angles on the intake, two and a radius on the exhaust; it's a more modern valve job," says Roberts. In other words, the mid-lift flow are substantially better than the Performer RPM cylinder head. Or, as Roberts added, "It takes a flat-tappet cam and makes it look like a roller, and makes a roller just that much better."
Maybe more than most parts makers because Edelbrock has such large manufacturing capacity, "This is a little new for us, this level of head prep. We can put the port in CAD, and then send it to the shop as opposed to making a detailed hand-made port and then trying to make a tool path from that. It worked, in this case, really well," said Roberts.
The better valves and conical springs did add a little more cost to the XT head. "We thought of [using] 11/32-in. stem valves and knocking $100 off of it, but people are recognizing the value of this stuff, so we went with the real parts," noted Roberts. And it seems to work. "We wanted to see 10 hp over the RPM heads, and got more like 15 horsepower in a straight head swap. And that's still with a 60cc chamber, so we didn't make power with the compression."
Electronic overdrive transmissions...
Electronic overdrive transmissions proved an issue with XT electronics at first. Edelbrock techs got tired of having to cut into the XT wiring, so they made this Customer Interface Connector a standard part of the XT harness. It breaks out TPS info, wideband grounds and other useful info to a handy plug in the main harness. It saves having to cut into the various harnesses around the car.
Like the heads, there are a lot of trick details to the fuel injection as well. We don't have the space to get too deeply into the Edelbrock XT electronics packages, but let's start by saying there are various levels available. Scott Armish, Edelbrock's Electronics Engineer explained some are simple enough for us Average Joes, others offer the full gamut of tuning, data acquisition, high- and low-impedance injector support and other niceties expected in a top-flight electronics suite such as those in pro racing. And that's no surprise when you hear Edelbrock has teamed with EFI Technology--a name more commonly associated with Indy car electronics--to produce the XT electronics package.
Because the XT intake manifold we're examining here is a carburetor replacement piece, it is packaged with a relatively basic XT electronics kit that includes a small ECU with an accessible calibration selection guide. The ECU, "comes loaded with a calibration, of course, along with a manual with a tune-up list. These show the hardware combination that tune was made up with," says Scott. "There is also a primer on what affects what, then you can use the little tuning section to help you learn how to tune."
"Once you've mastered playing with those, then you are ready for the Calibration Module," says Scott. This compact module plugs into the XT system and lets the owner, "enter the system at either the Fuel or Spark modes. There are six rpm, four vacuum, and four spark setting Break Points," he explained. "You can bump the idle up and down, change the rev limiter, turn closed-loop on or off for the fuel control... It's just enough adjustability for the average guy." The system is more adjustable than the old standard of sending chips back and forth in the mail, which is what Edelbrock's older Pro-Flow required.
Ford's front-mounted distributors...
Ford's front-mounted distributors are an impediment to a front air entry on an intake manifold. Edelbrock's XT bends to the passenger side for this reason, leaving just enough room for a shorter, small-cap distributor. Mallory builds the shorter, billet, electronic pick-up distributor at right for Edelbrock. It's part of each XT intake-electronics-throttle body carburetor-conversion kit. Mallory's standard Ford large-cap distributor at left shows the size difference.
When Edelbrock eventually releases its own Ford crate engines, this is the XT electronics level they'll be supplied with. It seems to offer a useful level of tuning without being overly complex, plus, the Calibration Module is also a display module, so it allows viewing rpm, vacuum and so on. That could be handy for a guy updating an older carbureted Fox Mustang, let's say, as the XT electronics would deliver electronic engine management plus some "instrumentation" to keep an eye on things without having to rewire the car.
For more advanced hot rodders there is the standalone XT Plus. It forgoes the Calibration Module, going straight to a laptop interface. "It's the next to highest [XT] application, comparable to a FAST XFI," says Scott. XT Plus is in the $2,500 to $3,000 retail range. This is just the electronics, with no manifold. Above the XT Plus is the upcoming XTR. "This is a racing system, again from EFI Technologies," Scott added. "It's a full-blown mil-spec, low-impedence injectors, all-out unit." This is a notable step up from Edelbrock's more typical bolt-on and affordable racing orbit and we take that as an indicator of the increased reach this large company will need to prevail in the changing performance aftermarket.
Not for sale but fun to examine was a trick little engine emulator Armish was working on. It was an unboxed circuit board well populated with electronics and some blinking LEDs during our visit; it simulates an engine for the XT electronics to "run." It will be used for training and troubleshooting by Edelbrock-schooled technicians.
The brand-new hardware on the crate motor dyno mule we're checking out here is the Pro Flow XT intake manifold. Designed by Brent McCarthy, Edelbrock's Chief Engineer of Research and Development, the XT is a short-runner, tunnel-ram like intake designed as a carburetor replacement part. Early Mustangs, all they way up to 1985 Foxes ran carburetors and are prime candidates for this intake-based conversion. Of course, it could be fitted to later EFI Mustangs, but it makes no economic sense as the XT intake is sold with its own XT electronics package, so you'd be paying to replace your existing Ford electronics.
The compact Mallory makes...
The compact Mallory makes a tidy installation nestled under the XT's curving intake horn. The distributor can be removed/installed without disturbing the intake manifold by first removing the cap. It takes long fingers or maybe some help from pliers to change plug wires with the distributor in place. Details of the throttle cable installation show well here, too. It uses a cable bracket, so the old carburetor rod is of no use. Lokar, the street rod supply house, makes all sorts of cables and brackets for throttle and transmission conversions should the Edelbrock kit not have what you need.
The XT intake was designed...
The XT intake was designed entirely via computer and prototyped in plastic. Besides saving weeks in the foundry making casting changes, the computer allows checking and adjusting things such as casting thickness that were rarely done on the first production run before because they were either too difficult or came too late in the development process.
Just installed, the bare XT...
Just installed, the bare XT intake shows its lithe lines to the camera. Aside from the semi-buried distributor, access to the fuel rails, injectors, valve covers and other top of engine accessories is excellent. The straight intake runner into cylinder number five just shows here; each runner is identical for best air distribution.