[Editor’s Note: This article originally appeared in the February 2018 issue of Grassroots Motorsports.]
Lots of people discuss putting in a junkyard supercharger. Fairly just a few even begin to do it. However then actuality kicks in, inflicting many of those tasks to stall out and stay unfinished.
We’ve put collectively junkyard turbo setups earlier than–witness our Miata endurance racer–however wished to leap in with a DIY supercharger construct of our personal. We wished to search out out what’s concerned, the place the hindrances are, and what it takes to complete and succeed. We used a Miata for our construct, however each step of our venture can apply to only about every other automotive.
Earlier than we began, we spent fairly a little bit of time combing the web taking a look at boards, construct threads and business supercharger web sites. We wished to glean as a lot data as we might to house in on a particular plan for our venture. Not surprisingly, among the data was deceptive or simply plain incorrect. However we averaged what we learn, seeing sufficient widespread themes to place collectively a recipe for our setup.
Right here’s the place we landed: We’d use an Eaton M45 supercharger mounted on the motive force’s facet of the engine, intention for 6-7 psi of enhance, and hope for about 140 horsepower to the wheels. That’s a reasonably docile setup on this age of giant enhance and big energy, however it’s nonetheless far more potent than the roughly 100 horsepower that our inventory Miata made on the wheels.
Our quest for the blower took a couple of month of informal junkyard and web searches, however we lastly ended up with an M45 from a Mercedes-Benz for $100. The images inform the story about how we went from a supercharger on a desk to a a lot faster Miata.
We’re presenting a considerably condensed model of our construct right here within the journal. To see much more element, hop on our web site and head to the Builds and Venture Automobiles discussion board and search for a thread titled “Is the Reply a $100 supercharger?”
Right here’s the place we began: an Eaton M45 supercharger unit bought domestically on Craigslist for $100. We consider it’s from a 1998-2004 Mercedes-Benz C230 Kompressor. We have been fortunate to search out one which regarded excellent–possibly even freshly rebuilt.
We positioned the blower within the engine bay of our 1992 Miata to get a tough thought of the fitment and packaging points we’d be going through. Blocks of wooden held the supercharger in place whereas some 2.5-inch tubing gave us a sign of the hood clearance between the inlet and outlet. We jockeyed round issues till they regarded about proper, then took some measurements.
We have been lucky to have a spare engine that we might reference for mock-up. Utilizing measurements taken from our in-car mock-up, we began engaged on the brackets. We selected to drive the blower from the Miata’s air-conditioning pulley. Right here we’re checking the alignment of the pulleys–we don’t need a belt to slide or get tossed. Some preliminary math stated that our pulley setup would possibly yield as a lot as 8-10 psi of enhance–a bit greater than we desired. Slightly than fear about our pulley ratios at this step, we determined to attend till our take a look at drives and dyno assessments.
Along with retaining our belt in keeping with the pulleys, we needed to maintain it tight. We picked up a belt tensioner from a GM V8 (Napa half No. 38159; retail value $35.12), then mounted it to a Mazda casting designed for the power-steering pump. (Our automotive has guide steering.) We additionally purchased 4 belts from Napa that roughly the appropriate size. We saved the one which match greatest and returned the opposite three. Belt price: $15.90.
Earlier than finish-welding any of our brackets, we made a number of take a look at matches within the engine bay. We needed to reduce a few of our tack welds and barely reposition items alongside the best way. This image additionally exhibits the inlet/outlet adapter that we made for the blower. Though we might have hand-fabricated a mounting plate utilizing gap saws and die grinders, we took a high-tech method this time and drew up a plate in CAD utilizing SolidWorks. We had entry to a two-axis CNC plasma desk that we used to chop the plate.
Our objectives saved us centered on delivering a ok setup somewhat than an ideal one, so our brackets ended up a bit ugly. We will make them higher later.
We struggled for some time to find out a chic solution to fabricate the supercharger outlet. We wanted one thing that may match, can be attainable to manufacture, and would stream air effectively. Our analysis advised us that the outlet didn’t must stream in addition to the inlet, so we compromised magnificence for a somewhat crude outlet that may match and be attainable to manufacture. We have been ready to remake this half if it proved to stream too poorly. We selected a curved form resulting in a squared-off finish with a 2.5-inch tube. We shaped it out of 14-gauge metal, tacked it collectively, and test-fitted it to ensure it could clear the hood.
We struggled much more on the consumption facet, figuring out that stream mattered extra right here. After attempting a number of potential options, together with utilizing items of cast-off exhaust tubing from different vehicles, we realized we might most likely make one thing work with a U-bend. We ordered a 2.5-inch U-bend from Summit Racing (half No. SUM-623031; retail value $18.97) and set to work. Our first step was to chop the U-bend flush to suit onto our mounting plate.
We needed to work the U-bend in order that it matched up with the inlet of our mounting plate. For this job, we used a hammer and T dolly. Somewhat chopping and welding alongside the best way helped create the form we wanted.
With the preliminary piece able to go, we began chopping sections of U-bend to make the remainder of the inlet. We progressed one part at a time, test-fitting every iteration to the automotive and adjusting as crucial.
We test-fitted and tack-welded the sections into place till all the pieces regarded good. Then we fabricated a mounting flange from 1/8-inch metal, drilling its opening with a 2.5-inch gap noticed.
The ultimate take a look at match proved we have been prepared to maneuver on. We’d determined to mount a inventory Miata throttle physique to the inlet facet of the blower. All we needed to do subsequent was finish-weld the inlet/outlet adapter and mount a tab for the throttle cable.
Due to a earlier Craigslist buy, we had a pile of two.5-inch turbo tubing and a Okay&N-style air filter. We used the silicone ends, together with some extra 2.5-inch metal tubing, to manufacture the connections from the blower to the inlet manifold. A inventory throttle physique on the consumption manifold turned our tubing adapter; we figured that was simpler than fabricating a brand new adapter. As for its throttle plate, we simply eliminated it.
We had beforehand put in a MegaSquirt Plug-N-Play ECU within the Miata, and its base tune already had some enhance compensations. Time to test-drive the automotive. Actually, the primary outing was fairly disappointing; the Miata didn’t appear a lot quicker. Nonetheless, the bottom tune was very conservative, particularly the timing retard below enhance. Following every take a look at drive, we regarded on the knowledge logs and made the tune a bit extra aggressive. Then we headed again out, pushing the automotive a bit of tougher than earlier than. After 5 – 6 drives and changes, our disappointment had turned to deep satisfaction. The automotive felt fast.
We spent an hour on the dyno to get some strong knowledge and finalize our tune. Our first pull confirmed 6 psi of enhance and yielded 147 horsepower on the wheels and 130 ft.-lbs. of torque. We have been ecstatic as we’d gotten fortunate that our pulleys gave us simply the correct quantity of enhance and we’d gone past our 140-horsepower objective. With a bit of extra tuning, we landed at 153 horsepower and almost 135 ft.-lbs. of torque.
The graph exhibits all of it. Our Miata gained about 55 horsepower and 45 lb.-ft. of torque. We’re positive there’s extra energy to be extracted if we wished to chase it, however truthfully, we’re so pleased with the outcomes that we could name it ok.
Did We Actually Supercharge a Miata for $200?
The brief reply is we did it for rather less: We paid $100 for the blower, $35.12 for the loafer, $15.90 for the belt, $18.97 for the U-bend, and $3 for some {hardware}. That’s $172.99, mixed with about 40 hours of labor within the planning, fabrication and set up. We’ll admit we’ve obtained numerous expertise, a reasonably good stash of used components, and a well-equipped store to work in.
With out all of our benefits, we predict this might nonetheless be finished for about $400: $100 for the blower, $35.12 for the loafer, $15.90 for the belt, $18.97 for the U-bend, $75 for a laser-cut manifold base plate, $36.99 for a Okay&N air filter, $100 for an eBay turbo hookup package, and $15 for {hardware}. Add in a tunable ECU like a MegaSquirt ($300-$1200-plus) and the entire venture strikes to the $700-$1500 vary. Fifty horsepower for $200 is feasible, however even at $1500 it’s nonetheless a reasonably whole lot.
Learn extra:
How you can add cheap energy with a salvage yard supercharger
How you can add a used intercooler to a pre-owned turbo or supercharger
