kickingtyres

MX5 Supercharger project

Posted by Andrew on 11 December 2011 | 2 Comments

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This post will not be updated, it's more completely documented in my Supercharger Project pages.

I'm documenting the process of installing an Eaton M45 supercharger in my 2002 Mazda MX5. I've read several build diaries on various forums and websites, but still find myself asking seemingly obvious questions about things that have been omitted from these diaries. I hope this this will provide a comprehensive, step-by-step account of what is needed and done to do this modification.

This page is a work-in-progress and will be updated as the project goes.

First..

The car

It's a 2002 MX5 1.8 Sport. That means it is a face-lift mk2, or mk2.5 and has VVT (Variable valve timing) and a LSD (Limited slip diff). It does have power steering and ABS, but doesn't have air-con. The lack of air-con is relevant as it is driven off the same belt as the PAS pump and so will dictate what size of belt is required.

The components:

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. It could be argued that a 6-groove belt would be a better option, but this means sourcing and modifying the pulleys on the end of the crank and the PAS pump, which is way outside the scope of this project. I might look at this some other time.

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:

 

1. Hose kit : To allow the air-flow from the filter to the supercharger, and from the supercharger to the inlet manifold.
2. 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.
3. 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
4. Cast outlet : Bolts to the supercharger and provides the high-pressure outlet to the engine's inlet manifold.
5. Fabricated inlet : As it sounds, is what bolts to the supercharger feeding air into it from the filter.
6. belt tensioner plate : Allows the drive belt to be correctly tensioned.
7. 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. I suspect I may require a longer stud/bolt to allow it to mount on the exhaust.  Watch this space.

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 Ubuntu Linux and will test it on my MacBook Air as well using Parallels.  The Macbook Air is nicely compact and I could take it with me for on-the-fly mapping tweaks more easily than my monstrous 17" Dell laptop.

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.

Two mk1 1.6 throttle bodies : I'm using two throttle bodies, one sitting each side of the supercharger (one high pressure side, one low pressure side). It can be done with just one, but it will be noisier. Despite my car being the 1.8, the kit does need the throttle bodies from the 1.6.

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.

Alternator : The ECU on the MK2 and 2.5 handles the function of alternator regulator.  As I'm doing away with the original ECU I need to address this as the Emerald ECU doesn't have that feature.  The solution is to get an alternator from a Mk1 1.8, as those alternators are self-regulating.

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.  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 throtle 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.

The Mechanical Install

Cut a mounting bracket off the supercharger to allow the outlet to bolt on : I stuffed the outlet with blue-roll, and then taped a piece of cardboard over it to prevent aluminium filings from getting inside while I cut it off.  I also then attacked the whole thing with the compressed air line to blow off, and out, any swarf.

Bolted the outlet to the supercharger to verify it fits : The face of the cast outlet isn't very smooth, and the powdercoating isn't helping.  Over Christmas I'm going to put this in the milling machine and skim it to give it a good face.

Fitted the bypass valve to the outlet.  Fits fine.

Tried to fit the inlet to the supercharger : no chance: While it's the right shape, it's just too tight to go on. I'll probably attack this with the milling machine as well to get a good fit.

Offered up the silicone bypass hose which links the inlet to the bypass valve.  It's simply far too short.  Also, in talking to those who have done this install before, the silicone pipe is too soft and collapses under a vacuum.  To resolve this, I've ordered an alloy water pipe from GTS Tuning which will do the job. I can cut the useless silicone tube up to make up connectors to fit it to the valve and inlet.

I started to take some of the unused bits off one of the throttle bodies, but as the screws seem to be made of DairyLeasium, I've left them soaking in some WD40 and I'll attack them later.  I also need to source some plate to make up blanking panels for both the throttle body and the back of the supercharger.

Pictures to follow.

Wiring the ECU

... to come

Costs

Item	Unit cost	qty	total
Supercharger	250.00	1	250.00
ECU	595.00	1	595.00
MAP sensor	72.00	1	72.00
Idler pulley	19.95	2	39.90
Throttle cable	4.17	1	4.17
Throttle body	33.33	2	66.66
TRLane Kit	635.00	1	635.00
Drive belt		1
Spark plugs		4
Sacrificial ECU	50.00	1	50.00
USB-Serial adpater	12.50	2	12.50
Alloy bypass pipe	12.20	1	12.20
Techedge J2J Wideband Sensor kit	160.00	1	160.00
Alternator	30.00	1	30.00

Setting up a Base Map

...To come

Useful links:

• Emerald ECU : http://www.emeraldm3d.com/
• Tim Lane Fabrications : http://www.trlanefabs.co.uk/
• MX5 Heaven : http://www.mx5heaven.co.uk/
• Megasquirt : http://www.megasquirt.info/ and http://www.extraefi.co.uk/
• Skuzzle Motorsport : http://www.skuzzle.com/motorsport/ Nick at Skuzzle can do the full install for you, using the Tim Lane parts.
• Eaton Supercharger FAQ : http://www.eaton.com/Eaton/ProductsServices/ProductsbyCategory/Automotive/AutomotiveAftermarket/Superchargers/FAQ/index.htm
• Wikipedia article on Roots Type Superchargers http://en.wikipedia.org/wiki/Roots-type_supercharger