DIY Supercharger Conversion with Intercooler for MGB and MGB GT - Overview
In late 1964, The MGB's powerplant received five main bearings, making the more sturdy 18GB engine and later iterations ideal for hot-rodding. However, achieving a meaningful increase in torque and horsepower meant removing and dismantling the engine--an expensive proposition that also impacts the car's street manners and fuel economy.
A viable alternative is forced induction with a turbocharger or supercharger.
supercharging is superior
According to Eaton’s website, “[u]nlike turbocharging, Eaton superchargers provide instant throttle response and torque across the engine's entire powerband.” Turbocharging requires a dedicated oil pressure line, the custom exhaust work can raise temperatures under the bonnet, and turbos exhibit a slight lag in achieving boost. A supercharger has none of these drawbacks.
However, commercially available kits, such as Moss Motor's $5,900 conversion, may approach the cost of a race-prepped engine--without installation. But notably, these setups lack an intercooler and draw atomized fuel through the rotor chamber, which Eaton, the blower's manufacturer, specifically discourages.
As a result, these non-intercooled 'draw-through' systems require one or more measures to avoid harmful detonation and backfiring: retarding the timing, installing a 'decompression plate' or low-compression pistons, or adding water injection. Put simply, no modern production car with forced induction lacks an intercooler because it undercuts the very benefit it attempts to introduce.
(However, our convertible ram pipe and snorkel adapter can be used to increase air flow into the Moss Motors’ draw-through supercharger, as shown in the images below and on the purchase page.)
But now, there's another option: the Creative Spridgets DIY intercooled and dynamically bypassed supercharger conversion for the MGB and MGB GT.
Here is a video clip of the engine bay at idle:
Here is a video showing acceleration from 0-75 mph without dumping the clutch or speed shifting. The car has an internally stock 1800cc five-main-bearing engine, which generated ___ psi boost at 6,000 ft. / 1,829 m. elevation. The temperature was __ F. / __ C.
the supercharger
Our intercooled supercharger conversion utilizes Eaton's M45 (45 C.I.D.) blower as configured for at least two Mercedes Benz cars, which a European colleague has informed us may bear different designations. The only apparent difference is that the drain plug for the gear box may be closer to the inlet/outlet flange—meaningless for this conversion.
Look for model no. 207018 or no. 206127, which is OEM equipment on 1999 to 2003 Mercedes Benz SLK230 Kompressor coupes and 1999-2003 Mercedes Benz C230 Kompressor coupes, and on 2002-2004 C200 Kompressor wagons (or estates), and possibly on 2002-2004 C180 Kompressor models—but in any case without an electronic clutch. It is at least possible that certain 1998 and 2004 models may feature this blower as well.
If you locate other models fitted with this blower, please let us know so that we may update this page.
This supercharger has the same, 45 cubic inch displacement as the unit fitted to the 2002 Mini Cooper S. However, it has a simpler design, is more compact at 11" long, 6.5" wide and 5" high, and weighs only 16 lbs. (7.26 kg). Here are some photos comparing the above-listed designations:
Eaton Model No. 207018 (above)
Eaton Model No. 206127 (above)
This supercharger features inlet and outlet ports on the same side of the housing. This configuration allowed us to engineer a one-piece inlet/outlet manifold that uses the stock Mercedes gasket:
A single inlet/outlet manifold not only reduces production cost, a savings we pass on to you; it also enables a supercharger conversion that fits neatly beneath the Spridget's sloping bonnet, with the intercooler hidden behind the grille:
Here is a diagram showing the flow of air through the system and identifying related components under the bonnet:
This compact supercharger also affords ready access to ignition components and maintenance items. You can remove the distributor without disconnecting the high tension wires from the cap, replace the spark plugs with a standard ratchet and spark plug socket, access the oil dipstick and valve train as usual, and remove the serpentine belt in seconds to service the water pump or alternator:
Fitting an intercooler is an integral part of this conversion’s superiority to other alternatives, as it provides a cooler, denser mixture and eliminates the need to remove the engine to install low-compression pistons or retard the ignition timing.
Also eliminated are detonation from a heated intake charge—common where the supercharger bolts to the head via a shallow plenum manifold—and back-firing from gasoline condensing in the blower’s rotor chamber when the engine is cold.
This [vehicle model and part number] intercooler hidden behind the grille virtually eliminated any rise in intake charge temperature generated by the supercharger:
The same pulley ratio may produce different boost at different elevations, and of course exhaust system or internal engine modifications and the condition of your engine will yield varying results. Note that a camshaft with sufficient duration to relieve cylinder pressure may be necessary to exploit increased boost beyond that generated with the stock Mercedes pulley.
Please use our contact form and we will post the figures you achieve in a table available in the online instructions webpage.
To get started, review the FAQs and step-by-step online instructions. Then visit our purchasing page to download free plans to fabricate the supercharger mounts, and to order the core components in the parts list, including the 5-rib crankshaft and water pump pulleys required for the serpentine belt conversion.
You can then run your car naturally aspirated while completing the balance of the conversion in stages to suit your budget and time constraints.
turbocharging - and draw-through superchargers
Turbochargers have been fitted to many powerplants including the A-Series engine, but no kits, fabrication templates, or instructions are available for the A-Series. Also, turbochargers require custom exhaust work, a dedicated oil feed line, and exhibit a lag in generating boost.
However, if you prefer a turbo, you no longer need to find a costly MG Metro intake manifold and clumsy cast snorkel adapter, which requires hacking a hole in your Spridget's bonnet for clearance.
Creative Spridgets now offers a ‘tunable’ CNC-machined ram pipe & snorkel or performance air cleaner adapter for use when pressurizing the SU HIF44 carburetor on any vehicle, available here and pictured below. the same ram pipe & adapter will also work on draw-through forced-induction applications and on naturally aspirated cars, due to its patented ‘convertible’ design.
Also, our ram pipe and snorkel adapter can also be used to increase air flow to Moss Motors’ supercharger kit, as shown below in Jared Kleusner’s MGB GT.
*Note: the fifth and sixth images are of a Mazda RX7, demonstrating the broad array of potential applications of these adapters to enable your projects.
The ram pipe is optimized to accelerate the intake charge on any HIF44-powered engine.
Also, by simply adding our ’tunable’ HIF44 kit with three interchangeable restrictor rings, you can achieve the correct pressure differential between the Venturi (jet) and the float chamber as discussed by David Vizzard in “Tuning the A-Series Engine” at p. 346.
The SU HIF44 mounts directly to a Minispares C-AHT770 cast aluminum manifold shown above, which costs just $67 including shipping from the UK.
You can convert a standard HIF44 for pressurized operation as described here.
You can fit an Audi A4 intercooler behind the grille in the nose of your Spridget for denser mixture and more power as described here.