By Bob McClurg
The Italian-manufactured Weber 48IDA downdraft carburetor and a Ford V-8 racing engine seem to go together as natural as ice cream and apple pie. When bolted in 2x4 configuration onto an individual runner (IR) intake manifold, (whether it be 427 FE, 351 Cleveland, or Hi Po 289,) the quick-revving, 48IDA Weber downdraft carburetor provides peak torque and "instant" horsepower, as opposed to a conventional plenum-type 4v carburetor and intake manifold which progressively "builds" torque and horsepower, while maintaining those performance characteristics over a much broader power band. Simply put, a 48IDA downdraft Weber carburetor induction system performs much like mechanical fuel injection, yet gives you the street drivability of conventional 4v carburetors.
While lightning quick throttle response and performance are the Weber 48IDA's strong suits, looks are another reason for this carburetors overwhelming popularity with high performance buffs. Anybody can bolt on a Holley, but when you slap a set of these sexy little Italian downdrafts onto that small block-powered Deuce highboy, vintage race car, that long-awaited Cobra replica project, a genuine, 289, or 427 Shelby Cobra restoration, or its pony car siblings the Shelby GT350, and GT500 Mustangs, you make a high performance "statement" that cannot be ignored.
But here's the dilemma. These carburetors went out of production sometime in the 1980's, and are in extremely short supply. Of course, their relative scarcity dictates a lofty selling price whether they be new/old stock 48IDA's, (good luck finding a set of those!) or used sets, being sold used, as rebuildable "cores."
Enter Bob Ream and partner Wes Henderson from Phoenix, Arizona's Imagine Fuel Injection. Last summer, the guys from Imagine Fuel Injection debuted their new Weber-inspired, individual runner, electronic throttle body fuel injection system to an enthusiastic audience (which included Carroll Shelby himself,) at SAAC-25, held at Lakeville, CT's Lime Rock Park Raceway.
"We started this project in November, 1999," said Bob Ream. "The Weber 48IDA carburetor was quickly disappearing from the performance aftermarket, and there were people out there who still wanted the performance, economy, and the looks offered by the Weber 48IDA without having to scour the country, and pay the lofty prices being commanded for these carburetors."
Ream and Henderson reasoned that if they could offer an IR-based, electronically-managed "Weber-type" throttle body fuel injection setup at an attractive price, they could effectively re-capture, as well as revive a waning market segment of the performance induction systems industry.
"Today everybody drives an electronically-managed, fuel injected car, or truck. They drive them to work. They drive them to the race track. One thing which the EFI cars of the 90's have taught motorists is that a car can perform at its best at all operational levels with this type of system. So, why not install a setup similar to this on the car you drive for pleasure?"
Using readily-available cast aluminum Weber IR intake manifolds as the foundation, the guys from Imagine Fuel
Injection designed a billet aluminum down draft throttle body which essentially utilizes all the outer dimensions of the Weber 48IDA. "By doing it this way, we can use the Weber intake manifolds, their gaskets, their induction stacks, and even their air cleaners," said Bob Ream.
The throttle body itself is manufactured from CNC-machined T-6, 6061 heat-treated billet-aluminum, and features a 2-inch (50.8mm) standard throttle bore size with stamped-aluminum throttle plates. On "turn-key" induction systems, these throttle bodies are port-matched to the IR intake to achieve maximum air/fuel flow, and performance. Imagine Fuel Injection's bi1lett-bodies are finished in either a clear bright anodizing, or an optional polished aluminum show finish.
"When it came to the throttle linkage, we found that (due to the proximity of the electronic fuel injectors,) we had to re-locate the system's throttle linkage, l-inch higher on the throttle body for clearance." This modification was also necessary to maintain fuel injector-to-intake valve alignment which is so critical with throttle body-type, multi-point fuel injection systems."
What type of fuel injectors does Imagine use with these systems? "A lot it has to do with the compression ratio of the engine, the rpm power band which you intend to operate the engine at, and the cam profile which you're using," says Bob Ream. "Traditionally you would use either a Lucas, or Bosch electronic fuel injector with these applications. For example, we would use let's say a 43 lb./hr fuel injector for a 427 FE engine application, while we would choose perhaps a 30 lb./hr electronic fuel injector for a smallblock application like a Hi Po 289."
Imagine Fuel Injection also manufactures their own CNC-machined, billett-aluminum fuel rails from raw bar stock. These fuel rails work in conjunction with a standard Bosch 200 lb. electronic fuel pump along with an Aer-O-Motive billett-aluminum high pressure fuel regulator and filter.
So much for the mechanical aspects. Now for the "star wars" technology. "We like using either the HalTech F9A, or Electro-Motive distributorless engine management systems," said Ream. "The F9A is a well known unit with a 15-year track record for precision, and reliability. This system is primarily used on applications which for technical authenticity, like a Shelby or Mustang application, require the use of a conventional distributor. It's very trouble-free, and in any type of motorsports, that is the name of the game."
On the other hand, Imagine recommends the Electro Motive distributorless engine management system for more high tech applications like the Vortech supercharged, 351-W late-model Mustang which they are currently working on in conjunction with Phoenix, Arizona's B&R Automotive.
Another integral component in the Imagine IR throttle body system is the use of an RS-232 cable which can be setup to interface with either Ford or GM-type electronic engine management sensors.
Ream went on to relate that rather than employing the more commonly used Microsoft; windows engine management systems computer software program, * the company has elected to use the older DOS version.
"The reason we did this is because the DOS computers are in-expensive, and plentiful. As such, they become practical to take to the race track where adjusting fuel distribution and airflow is critical. You can beat them around. You can get dirt on them, and should one of them ever fail, you can go back to the local swap shop and pick up another one for around $150.00."
Imagine Fuel Injection also builds a number of "use specific" wiring looms which interface with their electronic throttle body fuel injection systems. "We offer wire looms for both small, and big block Cobra's. We manufacture a wiring loom for the DeTomaso Pantera. We manufacture wiring looms for both small block, and big block Shelby GT350's, and GT500's. These looms will also work just fine on early-model Mustangs. We even manufacture wiring looms for Chevrolet and Volkswagen throttle body applications!"
Of course, you can talk all day about how great a product is, but how well does it hold up in "real world" situations? "Our dyno man, (Terry Kell, Las Vegas, NV.) says this system is the best thing he's ever layed hands on," said Wes Henderson.
Testing at Kell's Las Vegas dyno shop was done using one of the Shelby aluminum alloy 427 FE's, built by Shelby American's resident engine man Mike LeFevers. "We pitted our intake manifold against a Holley 850 Edlebrock victor dual plane intake. We recorded torque, horsepower, and exhaust gas temperatures. At 4500 rpm, the Holley/Edelbrock setup produced its most significant amount of torque, 406.24 lb./ft., while the Imagine Fuel Injection throttle body setup produced 427.19 Ib./ft. Optimum horsepower figures for the Holley setup came in at 5,500 rpm, registering 399.98 hp. On the other hand, the Imagine IR system recorded its best horsepower figures at 5,000 rpm, registering a solid 418.96 hp.
Naturally with any IR type intake setup, the exhaust gas temperatures (EGT's) also straightened out between cylinders. The Imagine Injection IR system showed as much as a 400-degree temperature drop between engine cylinders temperatures. That's a lot!
"This is really THE intake system to have for a street Cobra," says Finish Line Motorsports (Las Vegas, NV.) president Roy Hunt. "It runs as smooth as a Mercedes, yet exhibits absolutely crisp throttle response while exhibiting a slight "lope" which give you an indication of the performance potential which lies beneath the hood."
Getting back to Carroll Shelby, Ream and company installed one of their big block IR setups on Californian Mike McAllister's Finish Line Motorsports-prepared CSX4124, and handed Carroll Shelby the keys SAAC-25. "Mr. Shelby was extremely impressed with the power, throttle response, and clean operation of the IR throttle body system. In fact, he ordered one of these systems for his own personal Cobra (427SC "Completion Series," #CSX3056.)"
How do you lay your hands on one of these killer IR setups? Should you already own a Weber setup, or already have the intake manifold, any, or all of these components can be purchased separately. Or, you can purchase "the whole nine yards" for about the same money as you would spend a fully decked-out 48IDA setup. For dealer information, just contact Imagine Fuel Injection at the telephone number listed below. The sky is the limit! MI.
* For those wishing to use a windows engine management software program, Imagine offers an optional program in Beta form.
1. Shown is Imagine Fuel Injection's complete IR/EFI system for the Ford big block FE. You can purchase these units all, or in part through participating Imagine Fuel Injection dealers for about the same price as you would pay for a set of Webers!
2-3. Imagine Fuel Injection's "Weber-type" throttle bodies feature 2-inch (50.8mm) throttle bores, and are CNC-machined from 6061, T-6 bollett-aluminum. These bodies can be had either clear anodized, or with a "show polish" finish.
4. Shown is the smallblock (289) Ford unit which Imagine exhibited at last summer's SAAC-25 national convention. These throttle bodies utilize all existing Weber hardware which are readily-available throughout the performance aftermarket, intake manifolds, gaskets, velocity stacks, and air cleaners.
5. In order to maintain correct fuel-injector-to-intake valve alignment, it became necessary to re-locate the throttle body linkage up 1-inch on the throttle body from the traditional Weber mounting position. This overhead view also shows the proximity of the 30 lb/hr. Lucas fuel injectors and fuel injector bosses in relation to the throttle linkage.
6. This "down the throat" angle shows the systems 2-inch bore (50.8mm) stamped-aluminum throttle plates. These units were designed to utilize Weber factory velocity stacks, (either tall or short,) and mount to the Imagine Fuel Injection throttle bodies in the same manner as a Weber 48IDA, using a Weber gasket, and a pair of 3/16-inch machine screws.
7-8. Imagine Fuel Injection also manufactures its own fuel rails from CNC-machined-aluminum bar stock. These rails utilize a standard Aer-O-Motive billett-aluminum high pressure fuel regulator and fuel filter.
9. This shot shows the Ford Parts and services fuel sensor and harness used on the 289 system.
10. These sensors "plug in" to either a Hal Tech F9A computer (shown) which is used for traditional applications, or the high tech Electro-Motive engine management system used in more sophisticated applications. Also shown is Imagine Fuel Injection's wiring harness for a 427 Cobra.
11. And speaking of Big Block Cobra's, this overhead view of Californian Mike McAllister's 427 Cobra (CSX4124,) clearly shows the quality and appearance of the Imagine Fuel Injection electronic throttle body IR setup. Note the slick mounting of the fuel rails, fuel regulator and gauge. Those oval air cleaners are Imagine items.