DIY Intercooled Supercharger
Do you sell a complete kit?
NO. We provide a handful of core components for the conversion that cannot be fabricated by DIYers, as they are CNC-machined from aircraft-grade aluminum to exacting tolerances.
We offer free downloadable PDF diagrams to fabricate the supercharger mounts here and on our purchase page, and will soon provide diagrams for three simple components you can make on your own—including this aluminum mounting block for the serpentine belt conversion:
We have begun to post online instructions with detailed photographs and fabrication tips.
The first step in the conversion is to install a serpentine belt drive to replace the OEM ‘V-belt’ drive. You can then drive your naturally-aspirated Spridget while completing the remaining stages of the conversion to suit your budget and available tinkering time.
what is the benefit of a blow-through supercharger conversion?
A ‘blow-through’ conversion allows use of an intercooler. Every modern production vehicle running a turbocharger or supercharger incorporates an intercooler to increase power, combat detonation, and increase the engine’s durability and street manners.
The ‘draw-through’ design of the other supercharger kits for the A-series, offered by Moss Motors and High Performance Products of Australia, mounts the blower directly to the intake ports via a short manifold, prohibiting use of an intercooler.
how difficult is the conversion?
Moderate to advanced. Most of the tasks involve bolting on various parts, but you or someone you hire will have to weld up the mounts for the supercharger. This involves an hour of welding or less after the components (five of them) are fashioned from mild steel bar and angle iron in 3/16” and 1/8” thickness. Many welders will consider this a ‘minimum charge’ job.
We have now posted free downloadable drawings of the components here and on our purchasing page, so you can fashion them yourself to either weld together or carry to a welder to do that for you.
You must also make a handful of small, simple parts from aluminum bar available via the internet (the online instructions will show you how), install a high-pressure fuel-delivery system (fuel pressure in the float bowl must exceed maximum boost), and convert an SU HIF44 carburetor to run under boost conditions as explained here.
The system is compatible with throttle body fuel injection—using the same intake manifold employed in this conversion—but we have yet to finalize the details. That’s our next project in the cue!
You will need:
(i) a set of mechanic’s hand tools, including flat and round files, scribe or scratch awl, measuring tape and 24” carpenter’s square or straight-edge to align the pulleys;
(ii) bimetal hole saw and hack saw or (preferable) handheld band saw or plasma cutter;
(iii) 4” to 6” bench vise (bigger is better—you will use this countless times on your Spridget or Minor);
(iv) compressed air and an inexpensive rotary grinder (ours cost $13.00 on Amazon) to run a carbide rotary bit, although you can use a drill motor to do that;
(v) a drill motor or Dremel to slot the adjustment holes in the supercharger mounts;
(vi) a handheld tubing bender for the fuel lines; and
(vii) a drill or ideally a drill press. A smaller, inexpensive bench-mounted press works fine, and is what we used to produce consistent results.
what do i have to buy?
You will need the below-listed core components, together with a host of widely-available parts including silicone snorkel elbows, a K&N-style performance air cleaner, ‘T-bar’ style hose clamps and aluminum connecting tubes or to save money, compression-bent steel exhaust pipe (we are working on downloadable templates you can take to a muffler shop), steel fuel delivery line (the OEM fuel line becomes the return line), a high-pressure fuel pump and aluminum swirl tank, and various fasteners.
A combination vacuum/boost gauge helps in tuning and is fun to monitor while operating the system once installed, but is not vital.
We are working on a complete parts list, which we will post online and make available as a free PDF download, but the below-listed components represent the bulk of the cost of conversion, which ranges between $2,000 and $3,000, largely hinging on whether the supercharger and carburetor you source are new or used.
Eaton M45 supercharger model no. 207018, from 1999-2003 Mercedes SLK 230 Kompressor (w/o electronic clutch) and some 1999-2000 Mercedes Benz C230 models (w/o electronic clutch);
Creative Spridgets Eaton M45 supercharger manifold;
Creative Spridgets serpentine crankshaft pulley;
Smoothflow Pulleys serpentine water pump pulley for the A-series engine and their modular M45 supercharger pulley kit (on the same web page);
Creative Spridgets SU HIF44 snorkel adapter;
If running an early down-flow radiator or VW Rabbit crossflow radiator (the latter conversion will soon be covered on this website), Creative Spridgets thermostat housing adapter;
Minispares C-AHT770 cast aluminum manifold;
Intercooler from a 1997-2002 Audi A4 with a turbocharged 1.8L engine (i.e., Amazon for $72.50 w/free shipping);
Supercharger bypass valve from a 2002 Mini Cooper S (i.e., www.europortparts.com, $94.60).
*Note: when comparing the cost of this DIY conversion, consider that, unlike other ‘complete kit’ options which lack an intercooler, this conversion does not require dismantling the engine and replacing the stock 8.8:1 compression pistons to make optimum use of the available boost.
We are working on step-by-step instructions and a photo series for rebuilding your own supercharger. Overhauling the ‘snout’ bearings and seals is well within the skills of an average DIYer in possession of an arbor press. If you can adjust your valves, you can do this job.
Finally, we are considering offering partial rebuilding services of the more difficult portions—such as R&Ring the rear ‘pocket’ needle bearings and timing the rotors, which is necessary to replace the inner seals between the rotor chamber and gear box. Please contact us if this is something you would appreciate.
how much weight does the conversion add?
The supercharger, CNC-machined aluminum M45 manifold adapter, and mild steel mounts add approximately 24.25 lbs. or 11 kg. The aluminum serpentine crankshaft and water pump pulleys yield a net savings in weight over their steel counterparts, as do the single HIF44 carburetor and manifold over the dual HS2s. Including the aluminum intercooler, intake plumbing, fresh-air intake rerouting, and high-pressure fuel delivery system, plan on a net increase of less than 30 lbs. or 13.6 kg.
This modest weight gain is, of course, far outweighed by the performance gain of at least 35 h.p.
will this conversion work with a belt camshaft drive?
Yes. However, the Mini Spares belt camshaft drive setup (for instance) puts the timing cover roughly 5.5mm or .22” forward. This requires shimming the serpentine belt crankshaft and water pump pulleys forward a corresponding amount.
The mounts for the supercharger as currently designed may yield sufficient fore-aft adjustment to accommodate the shimming, but if not it is an easy matter to shim the blower pulley as well. You will just need longer, countersunk Allen screws to attach SmoothFlow Pulleys’ modular blower pulley to the stainless steel flange.
Although we did not engineer our 5-rib serpentine belt crank pulley with the belt camshaft drive in mind, as it reduces the amount of contact area between the crankshaft and pulley, at least one user has done this. He recommends using a heavy duty, extra-long Allen head screw to secure the crank pulley, available from Spridget Mania.
does this conversion retain the heater?
Yes. However, the intake duct must be re-routed underneath the right-hand fender as explained here, and the OEM fan replaced with an inline model, such as this aluminum racing fan from Revotec:
is this conversion reversible?
Yes. Adding the intercooler requires you to cut two holes in the front valance behind the grill. Reversing that step requires welding back in the circular pieces of metal you cut out—roughly 30 minutes of prep and welding. All other steps merely involving installing or removing components.
Rear Disc Brakes
DO YOU SELL A COMPLETE KIT?
NO. We sell aluminum adapter plates and provide step-by-step instructions that allow you to perform an inexpensive DIY conversion. The first do-it-yourself task is browsing a few websites or going to the store or auto recycling facility to obtain the remaining components in the parts list. This eliminates our ability to make a profit on the remaining parts, but it also reduces our overhead dramatically. We pass the savings on to you.
can i have someone do the conversion for me?
YES. Any competent mechanic can perform the installation. CC Motorsports is an excellent choice. Derek Chima's meticulously finished race cars have been featured on British V-8 magazine:
does the conversion add unsprung weight?
YES - it adds 2.4 lbs. or 1.1 kg. per corner. However, we feel that the increased braking force, zero adjustments, and greatly simplified lining replacement is well worth it.
Will the rear disc brake adapters fit other cars?
This conversion will work on all 1/2 and 1/4 elliptical spring Spridgets. You will have to perform one additional step on Bugeye Sprites, which is described in the installation instructions, but otherwise the process is identical.
ALSO, one resourceful owner has discovered the adapters will fit a Morris Minor, simply by rotating them a few degrees and redrilling the mounting holes. See the customer cars page.
what wheels are compatible with the conversion?
See the photos of compatible wheels and measurements for those with custom or racing wheels on the disc brakes page.
Is a proportioning or 'bias' valve necessary?
YES. With original Spridget Lockheed discs on the front, this conversion produces a definite rear-wheel bias, and a proportioning valve is needed. See the proportioning valve section on the disc brakes page.
WILL THIS CONVERSION WORK WITH HEAVY DUTY RACING AXLE HALF-SHAFTS?
Yes, but the self-centering method for OEM half-shafts outlined on the installation page may not work. Vintage racer Simon Page overcame that obstacle by simply redrilling the rotors to match the correct PCD.
will these disc brake adapters work with double-bearing hubs?
Unfortunately, we have been informed that the Peter May double bearing hub will not clear the adapters. We do not have data on other hubs.
will these adapters work with a rear traction link or panhard rod?
The short answer is, it depends on the configuration.
Frontline's RTL appears to connect on the R/H side close to where the Nissan caliper ends up--aft of the axle and just above the leaf spring. That could be incompatible with this conversion.
Panhard rods vary so much in configuration and attachment method that it is impossible to answer this question without seeing yours. However, you may be able to get an idea from these photos. The remainder of the axle is unchanged from the stock setup on your Spridget: