Subject: Trouble-free, state-of-the-art, high-tech EFI throttle body performance. And, the looks of classic Weber carburetors.
By Bob McClurg, SAE
The Italian-manufactured Weber 48IDA downdraft carburetors and a Chevrolet engine (be it smallblock, or big block,) just seem to go hand-in-hand with each other. When bolted in “2×4” configuration onto an individual runner (IR) intake manifold, the 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 Weber downdraft induction system performs much like a mechanical fuel injection system, yet gives you the drivability of a conventional 4v carburetor.
There is however a mechanical downside to the Weber 4BIDA, and that is that they are somewhat hard to tone. The carburetor’s fidgety nature has been known to produce a potentially-firey-phenomonon known as “Fuel standoff,” which can transform a race car into a smoldering pile of ash in short order. However, those racers who knew how to deal with the Weber 48IDA’s eccentricities were quite successful. In the mid 1960’s, 48IDA Weber carburetor systems powered up the infamous Corvette Gran Sport endurance racers, and early McLaren Can Am cars (just to name a few,) producing championship-winning results.
When it comes to the street machine set, the 48IDA’s looks are the primary reason why these carburetors enjoy such overwhelming popularity. Or, look at it this way, anybody can bolt on a Holley, but when you slap a set of these sexy little Italian downdrafts onto that smallblock-powered Camaro, ’32 highboy roadster, vintage race car, or perhaps a resto-rodded “Tri-5” Chevy, you make a high performance “statement” which 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. While it is true that NOS Webers can still be purchased through a VERY LIMITED dealer network, their relative scarcity dictates a lofty selling price. On the other hand, used sets, or rebuildable Weber “cores” also fetch a veritable king’s ransom at swap meets.
In November 1999, Bob Ream and partner Wes Henderson founded Imagine Fuel Injection. “The Weber 48IDA carburetor was quickly disappearing from the performance aftermarket, and there were enough 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 be1ng 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 competitive 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, (ie: Inglese Induction Systems, Moon, Blue Thunder, or Ultra, for Chevrolet smallblock, or Inglese or Moon intakes for big block Chevrolet applications,) the guys from Imagine Fuel Injection designed two different size billet-aluminum down draft throttle bodies which essentially utilize all the outer dimensions of the Weber 48IDA. “By doing it this way, we can use the Weber intake manifolds, their induction stacks, and even their air cleaners,” said Bob Ream.
Imagine’s low-profile, 4-inch throttle body is absolutely perfect for bow ties with low hood clearance problems. On the other hand, the 5-inch unit is perfect for everything else in between. Both throttle bodies are manufactured from CNC-machined T-6, 6061 heat-treated billet-aluminum, and feature a 2-inch (50.8mm) standard throttle bore size. On “turn-key” Imagine Fuel Injection systems, these intake manifold is blended to the IR intake runners to achieve maximum air/fuel flow, and performance. Imagine Fuel Injection’s billett-bodies can also be had in either a clear bright anodized finish, or an optional polished-aluminum show finish.
“When it came to the bell crank-type 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 (than a 48IDA Weber setup,) on the throttle body for clearance.” This modification was also necessary to maintain fuel injector-to-intake valve alignment which is critical with throttle body-type, multi-point fuel injection systems. ”
What type of fuel injectors does Imagine use with these systems? “A lot of 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 and horsepower, says Bob Ream. “Traditionally you would use either a Lucas, or Bosch type electronic fuel injector with these applications. For example, we would use let’s say a 43 lb./hr fuel injector for a 427/454 big block Chevy, while we would choose perhaps a 30 lb./hr. electronic fuel injector for a smallblock application like the Chevrolet 350/400- series engines.”
Imagine Fuel Injection also manufactures their own CNC machined, aluminum fuel rails from raw bar stock. At this juncture, it should be noted that on turn key Imagine IR Throttle Body Systems, the base of the injectors are threaded in order to fit more securely into the injector port opening in the Imagine throttle bodies.
Two types of fuel pumps are recommended with these systems. A standard 200 GPH. Bosch electronic fuel pump is recommended for engines producing 500hp. or less. However, when it comes to engines producing in excess of 500+ hp., Imagine recommends the Aer-O-Motive billett-aluminum high pressure fuel pump, (rated @ 500 GPH.,) along with the Aer- O-Motive fuel regulator and Aer-O-Motive fuel filter.
So much for the mechanical aspects. Now for the “star wars” technology. “We like using either the DOS-based, HalTech F9A, or Electro-Motive distributorless engine management systems, available in either DOS or Windows-based versions, ” 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 featuring a conventional electronic-type distributor. “It’s very trouble-free, and in any type of motorsports, that is the name of the game.
Ream went on to relate that since DOS-based laptop 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 ever fail, you can go back to the local swap shop and pick up another for around $150.00.”
When it comes to high-tech applications, Imagine recommends the Electro Motive distributorless engine management system with crank trigger feature. This setup utilizes either a DOS or Windows-based program.
How do you setup these programs? “ElectroMotive has a program called “Wintech Wizard. ” You fill out one page of information outlining the base parameters of your engine. What is the Brake Specific Fuel Consumption (BSFC) of the engine? What is the rating on the fuel injectors you’re using? What cam profile are you using? What estimated horsepower you have, etc.
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 most popular small, and big block Chevrolet 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 a “Brand-X” engine built by famed engine builder and Bonneville land speed record holder Mike LeFevers. “We pitted our system against a Holley 850-equipped 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 lb./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 cylinder temperatures. And, due to the very nature of the electronic engine management system itself, the engine ran extremely “clean.”
“This is really THE intake system to have for a Chevy street machine, street rod, or sportsman class race car,” says Imagine’s Wes Henderson. “It runs as smooth as a Mercedes, yet exhibits absolutely crisp throttle response while exhibiting a slight “lope” which gives you an indication of the performance potential which lies beneath the hood.”
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 ball of wax for about the same money (approx.$5,000-7,000} 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.