Megasquirt VS Gotech and others - Alfa Romeo Bulletin Board & Forums
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post #1 of 6 (permalink) Old 10-27-2012, 09:14 AM Thread Starter
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Megasquirt VS Gotech and others

I have a GTV6 with a '91 12V 164 3.0L engine and have decided to stop trying to get the original motronic system working as the PO damaged the harness and it has other problems as well. Anyway, I have heard about aftermarket fuel injection systems such as Megasquirt, Gotech, Spitronics, & Dicktator. Now I am sure that each has its advantages and disadvantages, but I would like to know if anyone has compaired these and which would work for me. I was planning to keep the injector sub manifolds but using multi throttle bodies so have no way of using a AFM. I have seen others use multi throttle bodies with MAP, TPS and O2 sensors. How do you get a consistant vacuum for the MAP sensor? How do you set up an idle circuit with these systems? is there a idle control valve or do you crack the throttle bodies? I like the concept of building my own box with Megasquirt as I am in the electronics field, but see that someone has installed Gotech on a 3.0L Milano, RSAE :: The Cars and this speaks volumes as well as offering experience on what to do and not do. It seems that some of you are pretty committed to one or the other and I would like to hear why. Thanks - Cort
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post #2 of 6 (permalink) Old 10-27-2012, 11:14 AM
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OK, I have to start off by saying I am an SDS dealer, but that's the system I think is the best for the Alfa V6, and it's what I use. I DON"T use it because I am a dealer, I am a dealer because it's the system I use. You can find them at Simple Digital System EM-5. That's the official site, it's not my site.

What makes SDS different? First of all, it's the only aftermarket system I know of commonly used in aircraft. That's because it's super reliable. It also comes with a complete new wiring harness, which really simplifies the whole operation. It comes with its own programmer, and doesn't require a laptop, or a certain version of windows or whatever. It's also very easy to tune.

All the answers to your questions can be found on the sds site. There are a number of ways to handle the various issues you are asking about.

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post #3 of 6 (permalink) Old 11-02-2012, 11:51 PM Thread Starter
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Thanks Greg

Thanks for your input Greg- I will add this to the list to consider. Are you familiar with any multiple throttle bodies? I would like to use 6 butterflies to mimic three two choke carbs for the sound and appearance. I would also like to put a hood scoop on to take advantage of the cool air going directly to the intakes. Really I just want to hear it better.
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post #4 of 6 (permalink) Old 11-03-2012, 12:40 AM
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From what I've seen you have 2 options for running 6 throttle body inlet manifold.

Toyota used MAP sensing on the last of their 20 valve 4AGE engine and they used a vacuum point from the cylinder head side of each throttle body, feeding into a small reservoir to try and help dampen the pulsations coming from each cylinder. My personal guess is that the engine management system looked more at the throttle position sensor value than the MAP sensor value.
Typically speaking, you will have quite low resolution with this set up. It won't take much throttle movement at low engine speeds for the MAP sensor to show atmospheric pressure. The MAP sensor may also show quite a high voltage value at idle. So the difference between idle voltage and atmospheric pressure voltage may be quite narrow. Some computers can be configured to look at a very narrow voltage/sensor value range, but plenty do like to have as much of their 0 to 5 volt range to give acceptable mapping resolution.

The other approach that is much better in my mind (I also know that Moto Guzzi applied this method) is to base the load sensing on a linear throttle position sensor and use the MAP sensor to provide an atmospheric pressure input to the computer. That is, the MAP sensor doesn't try and measure manifold vacuum, just atmospheric pressure and any variation it may have with changing weather conditions and altitude.

To set up an idle speed control valve will require a small reservoir that is then plumbed to each of the post throttle body runners. The idle speed control valve would be attached to the reservoir. Use a proper, car manufacturer type of ISC valve rather than any old solenoid valve.
Basically the it's the same set up as the common feed MAP sensor set up.
2 things to note about this. Make the plumbing as short and as even as possible. And you will probably struggle with a very low MAP sensor signal if you use this idle speed control method and primary load sensing via MAP sensor.

My personal preference is for the Australian made Adaptronic computers because that's what I have some experience with. They are also awesome value for money, have multitudes of configurable auxiliary outputs and digital inputs to help the computer run the engine/car (little things like A/C, power steering via a pressure switch and electrical load (head lights) inputs) to help maintain perfect idle speed control, can be configured for nearly any weird a$$ factory crank angle sensor you can name, with out having to change sensor type or trigger wheel. And they also provide excellent support and firmware upgrades (for free). They also have a 164 engine base map for you to get started with (though that is based on the factory inlet manifold. The CAS settings alone will safe time and money)
Haltech also make some very well priced and very capable range of computers.

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Last edited by Duk; 11-03-2012 at 01:00 AM.
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post #5 of 6 (permalink) Old 11-03-2012, 05:24 AM
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Al Mitchell in Virginia has installed Megasquirt on a number of 2.5 and 3.0 V6's including his own race cars and customer cars. He has his own dyno and he has lots of good data on optimal fuel and ignition mapping. I can put you in touch with him if you are interested in having him do one for you.

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post #6 of 6 (permalink) Old 11-03-2012, 03:16 PM
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Originally Posted by Cort Musgrave View Post
Thanks for your input Greg- I will add this to the list to consider. Are you familiar with any multiple throttle bodies?
Yes! I know of lots of them with ITBs, That's just not a problem. Here is one example which rates very high in the coolness category. SDS EM-3: Project Page

You can find more examples of SDS with ITBs on the SDS site.

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fuel injection, gotech, megasquirt, throttle body

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