Eaton M45 supercharger : This was acquired off Ebay, and is the same model fitted to the Mini Cooper S. For the M series superchargers from Eaton, the number denotes the volume of air, in cubic inches, that’s shifted per revolution, so the M45 moves 45 cui/rev. These are ‘roots’ type superchargers and have 3 lobe rotors with 60 degrees of end-to-end twist. Some kits, DIY or otherwise, have used the MP45 unit. The MP45 unit is, as far as I can tell, identical to the M45, but that the MP denotes that it was supplied by Magnuson Products. As I understand it Magnuson Products handles service and the aftermarket for Eaton and provides superchargers to a number of companies that design and manufacture the installation system for specific applications. Magnuson provides more superchargers for aftermarket applications than any other supercharger manufacturer in the world [source]. As this modification for the MX5 has gained popularity, the prices of these superchargers have gone up accordingly, so at the time of writing you can expect to pay between £250 and £300 for one in good condition. You may notice that the pulley on the supercharger has 6 grooves, whereas the pulleys on the end of the crank, and on the PAS pump are all 4-groove. Don’t fret, the 4-groove belt simply runs on the 6-groove supercharger pulley. With this project, some custom 6-rib pulleys are being made up to fit the blower, crank and power steering pump, with slightly modified ratios to spin the blower faster than with the standard pulley. The same effect can be had with a smaller supercharger pulley with some running pulleys as small as 58mm diameter. I prefer to keep the larger stock pulley and increase the size of the crank and power steering pump pulleys as that, along with the 6 rib belt, will ensure far more efficient power transmission to the blower with minimal slip.
Tim Lane supercharger parts : Visit Tim Lane for the most important parts. Tim can also provide a wealth of advice and is generally a friendly and helpful chap. The parts I obtained from him as are follows:
- Hose kit : To allow the air-flow from the filter to the supercharger, and from the supercharger to the inlet manifold.
- High flow filter : you can probably find other filters that might fit, but I thought it easier to just get this one as you know it’lll work with the kit.
- Supercharger bypass valve : At partial/low and closed throttle positions, you don’t wasnt to be pumping huge volumes of air into the engine. If nothing else, it’s unneccesarily noisy. The bypass valve allows the engine to effectivley become naturally aspirated when not under load
- Cast outlet : Bolts to the supercharger and provides the high-pressure outlet to the engine’s inlet manifold.
- Fabricated inlet : As it sounds, is what bolts to the supercharger feeding air into it from the filter.
- belt tensioner plate : Allows the drive belt to be correctly tensioned.
- 1800 supercharger mount : The 1.6 and 1.8 engines are different enough that a specific mount is required. Where the 1.6 has two handy holes that the bracket can be attached to, the 1.8 needs to use an exhaust stud as there’s only one useful mounting point on the engine itself. The bracket mounts fine to the engine, but the support bar which comes up from below didn’t line up properly with the mount point on the underside of the supercharger for me. I ended up machining my own one out of aluminium alloy so it had the correct ‘kink’ in it to fit around the belt tensioner and up to the mount point on the supercharger. (photos to follow)
Emerald K6 ECU : There are various options for engine management. Many have gone down the route of a piggy-back power-card which sits on top of the engine’s existing ECU and sends the required additional signals to handle fuelling and ignition timing that need to be modified for the use of a supercharger. In looking at the various options, I felt that the piggy-back powercard didn’t offer the optimal solution, meaning that fuelling would be incorrect at certain times. While not ciritical, indeed many have used this setup without any problems, I wanted to have more control over the fuelling and ignition. Another option is to get a fully featured ECU and piggy-back that off the standard ECU so both are working together to control different aspects of the engine management. This allows you to keep things liike the ODB output from the stock ECU, and gain some of the advantages of a fully featured ECU. I considered this route, and looked at the Megasquirt ECU which can be installed in thsis manner. In the end, I decided to go for an Emeral K6 ECU as a complete, standalone ECU, replacing the stock ECU completely. This means I have to start from scratch with creating a map for the ECU, but also means I have far more control over all the parameters. The Emerald ECU comes with a serial cable as standard, but can supply a USB adapter. The supplied software runs on MS Windows only, but I’m using a windows XP virtual machine under VMWare on my Macbook. The ECU installation is being completed by John Halstead of Brundall Motorsport, who is an expert in Emerald ECUs and generally a top bloke when it comes to performance cars.
MAP (Manifold Air Pressure) sensor : Since we’re changing the pressure inside the manifod using the supercharger and control valves, the ECU needs to know what the pressure is inside the manifold to allow it to control the correct amounts of fuel to inject, and the correct ignition timing. The MX5 doesn’t have a MAP sensor as standard, so I obtained one from the guys at Emerald. As with the air-filter, I’m sure there are others that can fit and are compatible, but getting it from the ECU suppliers just saves on that research. I went for the more expensive Marelli MAP sensor which is good for 250kpa (about 25psi of boost which is plenty) and made sure to include the plug & pins.
Sacrifical stock ECU : As you can’t simply unplug the stock ECU and plug in the Emerald, there are two ways of making it fit. One is to wire it into the car’s wiring harness with the supplied plug. This means, however, that you are cutting into the wiring, possibly removing the existing plug, and if you hit upon any issues (bearing in mind the wiring could be a few years old and not that easy to work with) you could end up with a non-functioning car. The other option is to make up a harness, similar to that you might buy for a car stereo, which will allow you to plug the existing ECU plug into the harness, and that harness into your new ECU. Of course, to do this, you need to obtain a socket. I know of one other who went down this route, and used the stock ECU, dismantling it for it’s socket. I was fortunate enough to find someone selling the same stock, but duff, ECU on ebay for £notalot. I snapped that up, as it would mean I could strip it for it’s socket retain the original ECU unharmed.
Two cam idler pulleys : The Tim Lane kit requires two of these, which are used to tension and route the drive belt.
Throttle body : I’m going to relocate the standard throttle body to the ambient side of the supercharger intake. The relocation is for two reasons. 1 : As this supercharger (roots type) is a positive displacement blower, it means the supercharger will be providing some boost at idle. Keeping the throttle in it’s stock position which is on the high pressure side of the blower. If you were to close the throttle from high revs, the supercharger would then pressurise the piping and intercooler against a closed valve and risk damaging the intercooler and the throttle valve itself.The throttle body on the 1.8S I have has an idle control built in. 2: The throttle has an idle control built in which will allow some air to flow into the system even when the valve is shut, making idle control far easier. The only downside is a slight reduction in throttle response as the air has to flow slightly more and get pressurised before it reaches the intake, but I’d rather go for reliability and, to be honest, the difference in throttle response for road use would be negligible.
Drive belt : I’ll know what size I’ll need when I’ve finished the install. Watch this space.
Spark plugs : Some cooler plugs are often recommended.If the tip of the spark plug is too hot it can cause pre-ignition or sometimes detonation/knocking and damage may occur. If it is too cold, electrically conductive deposits may form on the insulator causing a loss of spark energy or the actual shorting-out of the spark current. The various laws of thermodynamics (Charles’ law and Boyle’s Law) show us that as a gas is compressed, it’s temperature increases. As the supercharger is compressing the air, the temperature of the mass of air and fuel being pushed into the cylinder will be slightly higher than with a normally aspirated engine. As a result, when the piston compresses the fuel/air mixture further, the temperature of the combustion chamber at the point of ignition can be higher than normal. By using a slightly cooler spark-plug, you are ensuring the tip of the plug is remaining at the correct temperature and so helping to prevent pre-ignition.
Bypass pipe : The silicone hose supplied with the Tim Lane kit is too short/small to reach both the valve and the inlet. It’s also too soft, meaning it’ll collapse under a vacuum. My solution is to get an alloy pipe of the same shape and size, and cut the silicone one up to make connectors so it can reach the valve and inlet.
Wideband O2 sensor : The O2 sensor is supplied as standard can’t give an aftermarket ECU all the info it needs to make totally accurate Mapping decisions. Without a wideband O2 sensor, the exact fuel/air ratio can’t be calculated and so your engine could be running rich or lean. You can get an idea of this by removing the plugs and examining them, but that’s far from practical. Getting it onto a dyno or rolling road, an external O2 sensor can be used, but that only works for the time you’re on the rolling road. With a wideband O2 sensor, your ECU has much more information allowing it to inject the correct amount of fuel at all times. As I understand it, the narrowband, which is fitted as standard, has a very narrow range of acceptable measurement. Outside that range, it just says ‘bad’, without any informatoin about just how bad. The wideband quantifies that more accurately. The Emerald ECU can ‘learn’ and adapt it’s map based on the input from all the sensors, so in this case, a wideband sensor just helps keep everything accurate.
Miscellaneous plate/sheet : After removing some of the bits you don’t need from the throttle bodies you’ll need to make up a blanking plate to cover the holes left. It’s also not a bad idea to make up a plate to cover the end of the supercharger, where there’s an exposed, rotating power take off. In addition, as the Emerald doesn’t support the EGR (Exhaust Gas Recirculation valve), I’ll replace the gaskets where the exhaust feed enters the intake with solid plates. This will prevent the gas entering when the valve is removed, but also allow the system to be easily returned to stock if needs be. I’ll also be using plate to make up small cable brackets to hold the ends of the throttle cable which will link the two throttle bodies together. I’m fortunate that I’ve got bits of aluminium and stainless steel kicking about, but you should be able to source this stuff from any good metal suppliers. I’d expect, if you asked for off-cuts, that most would throw the small amounts you need into a bad for the price of a beer or a pack of biscuits.
MK I Alternator : The MK 2 and 2.5 alternator doesn’t have a regulator built into it as that feature is integral to the ECU. As the stock ECU is being removed completely, the alternator has been replaced with an item from a MK I which is identical physically, except that it includes a regulator built in.
Custom drive pulleys : Rather than buying a smaller supercharger drive pulley, the crank pulley is going to be made larger, giving the same ratio change. This means the supercharger will be spinning faster and so producing more boost. In the process, the pulleys are also being upgraded from 4 groove to 6 groove hekping prevent belt slip. As a result, it will also need an….
Intercooler : From Universal Intercoolers, they do MX5 intercooler kits, and the one I went for is the short pipe, over-the-rad kit. As you compress a gas, it’s temperature increases. The intercooler is basically a heat exchanger which cools the compressed gas in a manner similar to how a radiator is used to keep the coolant liquid temperature down. A cooler gas is more dense so it means it’s shoving even more air into the cylinders for even more bang, and thus more power.
Uprated radiator : With increased performance, bigger bangs and increased temperatures from compressing the intake air, it’s good practice to uprate the radiator to improve engine cooling. I’ve also sorted out a better cooling fan which shifts more air as well as being a bit more compact.
Oil cooler : As with the cooling system, being able to cool the oil more efficiently will help the engine.
Stage 1 clutch : The stock clutch is said to be good for 200bhp or a little more. At a drift day I was doing before I started this project, I started to feel some clutch slip so thought I should replace it. I think it’s sensible to use an uprated clutch so the hoped-for 220bhp is well within it’s limits, rather than towards it’s upper limit.
Findanza light-weight flywheel : This isn’t really a requirement, but since I’m doing the clutch, it would be rude not to throw in a lightened flywheel (7lbs as opposed to the standard 15lbs). This means the engine will be far more responsive as it’s not having to spin up the additional weight of the stock flywheel. The downside is that the engine will also slow down quicker and the idle might not be as smooth, but for the improved performance, I think it’s a small sacrifice.
Uprated fuel Injectors : Even although the Emerald can over-fuel the stock injectors by holding them open for 120% of the time they are normally injecting for, with the higher boost from the supercharger and the intercooler helping cool the charge, I’ve opted for a set of injectors from the RX8 (yellow ones) which will provide plenty of scope for further development.
Trigger wheel : The stock crank pulley only has 4 teeth for the sensor to pick up, and nothing to indicate top-dead-center. Using an aftermarket 36 tooth trigger wheel with a TCD indicator (usually a missing tooth) it means the ECU can be far more accurate and also enable the mapping to use sequential fuel injection rather than batched. Sequential injection is where individual injectors are triggered as the intake valve opens. Batched is where multiple injectors are fired at once. Sequential injection is better for fuel economy and emissions but at full throttle, high RPM situations, there’s little difference between the two systems in terms of performance.
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