|
|
Megasquirt EFI | |
|
|
Current Configuration Individual Projects Ignition Projects General Electrical Intake / Throttles Tuning Miscellaneous |
The information on this page assumes that the reader has some basic knowledge of the Megasquirt electronic fuel injection system. If this is not the case then I recommend you check out the information in the Required Reading page. This page provides a high level summary of what I have done with Megasquirt. The details of the projects are available via the links to the left. These links are arranged in chronological order within each project category. Independent vs. Single Throttle Body Several people new to EFI have looked at my projects and assumed that ITBs are the way to go without thinking through the tradeoffs between using ITBs vs. using a single throttle body like most production cars. There is a reason why most production cars don't use ITBs, they are expensive and relatively difficult to tune. A single throttle body going into a shared plenum is normally a cheaper, easier to tune solution. The main advantages to ITBs are incredibly fast throttle response, increased high end power, and of course that really cool intake sound you only get with ITBs. They also look really great. Depending on the length of the intake runners used with ITBs, you can lose a noticeable amount of low to mid range torque due to intake runners that are too short. If you look at a production intake manifold for an engine, the intake runners are normally relatively long compared to the runner length achieved with most ITBs. I have experienced this effect first hand and you can be throwing away more than 10% of your mid range horsepower by running intake runners that are too short. See my Tuned Intake page for more details on this. If you are looking for the safest, cheapest solution to adding EFI to your M10 engine then the way I did it is not the way to go. I would recommend using the intake manifold and fuel rail from an E30 318i which had EFI. There is a web site with parts to adapt this manifold to Megasquirt. It's www.02again.com. This place has the hard to fabricate parts you will need such as throttle body adapter, throttle position sensor bracket, EDIS brackets, etc. There are multiple examples of this type of EFI conversion on the web and in the Megasquirt forums. One such example is here at another website created by an E21 enthusiast. These common plenum solutions are very easy to tune with speed-density (MAP based) tuning and can yield almost the same performance as ITBs if done correctly. The reason I chose ITBs for my engine was mainly because I had already gone to dual sidedraft Webers and wanted to keep the look and performance I had seen from the carbs but wanted the car to drive like any other modern fuel injected daily driver. This is a very difficult goal to achieve and after more than 3 years of experimentation I have just about done it. My Megasquirt Conversion History Here is a brief history of my Megasquirt projects. I have fallen into a pattern of driving with a given configuration during the Spring / Summer / Fall and then performing major upgrades during the Winter months. This chronological history provides the sequence of my changes. The links on the left go to separate pages that describe each project in detail. My current Megasquirt configuration is provided in the top left section of this page. 2007 Projects I converted my engine over from dual Weber DCOE 40 carbs to EFI in 2007. The first step was to build the Megasquirt (MS) controller and add Electronic Distributorless Ignition (EDIS) to my carb setup. This way I could debug the EDIS portion of the MS install independent of the fuel. As part of this first project I fabricated a completely new engine harness to replace the stock Kjet harness and provide the additional circuits needed for EFI. After I had EDIS up and running I then replaced my Webers with 45mm Independent Throttle Bodies (ITBs) made by TWM Induction. These ITBs along with 24lb injectors made up the first generation of my fuel system. As part of the ITB install, I needed to create a vacuum manifold, or vacuum log to collect the individual vacuum pulses from the ITBs and provide a stable Manifold Absolute Pressure (MAP) signal for the MS controller. I also created a custom cold air intake. 2008 Projects I originally started my MS EFI project with the baseline Megasquirt 2 controller and firmware. Based on peoples experiences with ITBs on the Megsasquirt forums I decided to attempt to use speed density (SD) tuning which uses the MAP signal to determine the amount of fuel required. This worked better than the carbs ever did but I was not 100% happy. Ok, I'm a perfectionist and want my moderately modified M10 with ITBs to have all the benefits of ITBs but still drive like a "normal" car under all conditions. This is a pretty tough thing to do. About a year ago, the first versions of the MS-2 "extra" code were developed and one of the code's authors has an engine with ITBs and had similar issues with tuning as I did. The MS2-extra code has a tuning mode where you can blend speed-density and alpha-n (SD and AN) tuning. This gives "the best of both worlds" for ITBs and is working extremely well. At about this point I also removed the Ford EDIS controller and started directly controlling the wasted spark coil pack. Again, I was not 100% happy with the TWM throttle bodies (did I mention I'm a perfectionist?). My set of TWM TBs had a nasty habit of sticking close to closed throttle when the butterflies would get heat soaked. My best guess is that the butterflies expanded with the heat and would stick in the throttle bores when almost fully closed. This would cause the engine to not return to idle when you took your foot off the gas. I tried extra return springs and double checked the throttle shaft alignments but I could not get rid of the binding problem. A 2002 guy in my local BMWCCA chapter had been running Jenvey ITBs on his car with MS1-extra code. Based on his experience, I ordered a set of 40mm Jenvey ITBs and replaced the TWM setup in 2008. I also added idle air control at this time. 2009 Projects In September 2009 I worked with Tom from www.02again.com to develop a mounting bracket for individual coil packs to allow a coil on plug ignition system. My first project for the winter of 2009 is to re-design the intake system to get a better tuned intake runner length for the Jenvey ITBs. This project is being documented on my tuned intake page. This brings my EFI setup up to its current configuration:
Future projects include going from wasted spark to a true four coil setup. See the cam position sensor page for a glimpse into this. I'm also planning on adding knock detection. |
This site was last updated 02/11/12