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Just installed a Megasquirt on my car

This is a discussion on Just installed a Megasquirt on my car within the Computer & Tuning forums, part of the LSx Technical Help Section category; Hey guys just thought I would post that I successfully installed a Megasquirt onto my new SS. I have it ...

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    Just installed a Megasquirt on my car

    Hey guys just thought I would post that I successfully installed a Megasquirt onto my new SS. I have it piggybacked onto the stock PCM. It is set up for fuel control only at the moment but setting up spark control will take no time at all. I just wanted to get the fuel map dialed in before hooking up timing control as well. I have been driving it around today with my wideband and now the fuel map is completely sorted out and tuned in. It runs and drives just as good as a stock one. I wanted to go ahead and do this modification first thing so that when I start bolting on stuff like cam, ported heads, etc here soon I would already have a way to tune it.

    Here is a thread I found extremely helpful. I basically did mine exactly like his:

    http://forums.hybridz.org/showthread.php?t=122976

    The only difference is as follows:

    a) I did not find the .01 uF capacitors to be necessary in the crank/cam sensor inputs

    b) I connected the stock temp sensors to my MS, disconnected them from my MS, then put some dummy resistors on the stock PCM temp sensor inputs to fool the computer into thinking the coolant temp is 140* and the air temp is 80*. It would probably be better to just connect a second set of sensors for the MS, but I didn't feel like fooling with all that. I plan to eventually remove the stock PCM completely.
    Last edited by shiftless; 05-31-2008 at 07:58 PM.

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    TunedbyFrost.com Tuner Frost's Avatar
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    With all of the full tuning options and custom OS's including real time tuning for these PCMs, I can't fathom why you would do this to/for a stock car. The OEM PCM has been well proven past 1,000 rwhp. Cool that you pulled it off, but you still have to have a tuning suite to tune spark and more than that on the stock PCM... Could have just bought HPTuners and went from there on the OEM setup.

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    Quote Originally Posted by Frost View Post
    With all of the full tuning options and custom OS's including real time tuning for these PCMs, I can't fathom why you would do this to/for a stock car.
    Because the Megasquirt costs $140 and I had it laying around. This system also supports nitrous/water injection control, launch control (two step), and other features which the stock PCM does not support, AFAIK. At any rate, the price alone is worth it. Maybe this is a forum full of guys who have thousands of dollars just laying around to dump in their cars, but I do not. I'd rather spend my money on gas to destroy Mustangs.

    And as far as the car being stock, it does not appear that you actually read my message before jumping in with your reply. Yes it is stock at this moment, but within a month will have a number of mods included ported heads (home ported of course) and a cam. I will need a tune at that point and I am NOT spending $650+ for a tuning setup or paying somebody else to do it.

    Spark control is already thought of, handled, and solved. Having the Megasquirt control spark is as simple as splicing in a few more wires. The stock PCM will be left to control the transmission and other mundane chores, until I can replace those functions one way or the other.
    Last edited by shiftless; 05-31-2008 at 10:42 PM.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by shiftless View Post
    Because the Megasquirt costs $140 and I had it laying around. This system also supports nitrous/water injection control, launch control (two step), and other features which the stock PCM does not support, AFAIK. At any rate, the price alone is worth it. Maybe this is a forum full of guys who have thousands of dollars just laying around to dump in their cars, but I do not. I'd rather spend my money on gas to destroy Mustangs.

    And as far as the car being stock, it does not appear that you actually read my message before jumping in with your reply. Yes it is stock at this moment, but within a month will have a number of mods included ported heads (home ported of course) and a cam. I will need a tune at that point and I am NOT spending $650+ for a tuning setup or paying somebody else to do it.

    Spark control is already thought of, handled, and solved. Having the Megasquirt control spark is as simple as splicing in a few more wires. The stock PCM will be left to control the transmission and other mundane chores, until I can replace those functions one way or the other.


    It's cool, but I can make a HUGE list of Pro's for keeping the factory PCM against it. You will lose the cost of a tuning suite in fuel mileage alone soon if you do much driving, not to mention the 400-700 you spend if you go with a separate trans controller... and around the same price to go manual valve body. Your time *has* to be worth something as well. Even the budget meth kits comes with their own activation devices. There are plenty of guys cutting 1.3 60' times (and I'm sure better, because I know these guys) off the footbrake and 1.2s off a brake. I read all of what you posted. With a wideband and the incredible scanning tools that come bundled, full VE and MAF (or VE if you are ditching the MAF) can be done in hour. For what you get with a suite, $650 is just not out of the question. I guess from the sounds of it you are building a race car, so it's cool, but many people want to keep their ABS, traction control, working factory gauges and the full diagnostics provided by the OEM controller, which can quickly identify many issues.

    Don't get me wrong, I give you props for getting it up and going, there are few things that seem to vary from setup to setup that snag people, and it's cool that you DIY. I hope it gets you what you are looking for.

    -edit-
    I guess I am pointing this out also, because from where you are now, migration back to the OEM PCM is still easy. Sell the MS and be that much closer to HPT or EFIL. The stock PCM is very powerful and will provide the best driveability that I have seen on really any setup and there is a ton of support for it on the forums.
    Last edited by Frost; 05-31-2008 at 11:13 PM.

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    It's cool, but I can make a HUGE list of Pro's for keeping the factory PCM against it. You will lose the cost of a tuning suite in fuel mileage alone soon if you do much driving,
    Huh? Why is that? I have my cruise AFR dialed in at 15.5 at the moment and it cruises great. Mileage is no different from stock. You would not be able to tell that there is an aftermarket ECU in this car if you weren't told. Driveability and everything is just like stock.

    not to mention the 400-700 you spend if you go with a separate trans controller
    ..or $50 if I build my own. They're really not that complicated. In the mean time I can just keep using the stock ECU for that. I'll likely end up swapping to a TH400 anyway when the 4L60E breaks.

    Your time *has* to be worth something as well.
    I build fuel injection systems for a living, and the Megasquirt is about as simple as it gets. I had the thing wired up to the car and running the fuel injectors in about 4 hours before I quit on it yesterday evening. Then today I tuned it while cruising around town, showing off to my buddies, etc. As of this moment I am sitting out in the hospital parking lot using the net. The fuel map is completely dialed in and pretty much flawless. I've been driving around for hours racing and cruising.

    I guess from the sounds of it you are building a race car, so it's cool, but many people want to keep their ABS, traction control, working factory gauges and the full diagnostics provided by the OEM controller, which can quickly identify many issues.
    A race car? Uh, no. This is a full street car. My ABS and factory gauges work just fine. I have no use for traction control and I'm glad that my car did not come with that option. The diagnostics are just about as useless to me. I can identify any issue just as quickly by simply looking at the sensor readouts.

    For what you get with a suite, $650 is just not out of the question.
    Again, I am not spending that much money for a tuning 'suite'. Not only is the MS super cheap, but it's open source. It's simple and easy to understand. There are no licenses to buy. I can tune it with my Linux laptop. If there's a feature I want, I can write it myself. No, the Megasquirt does not do *everything*, but I don't need it to. I just need a way to tune the fuel and spark maps and provide a few extra features, like act as a window switch for a nitrous system.

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    Quote Originally Posted by Frost View Post
    I guess I am pointing this out also, because from where you are now, migration back to the OEM PCM is still easy. Sell the MS and be that much closer to HPT or EFIL.
    No thanks!

    The stock PCM is very powerful and will provide the best driveability that I have seen on really any setup and there is a ton of support for it on the forums.
    Perhaps you should look at the Megasquirt, then. The driveability is exactly the same as it was before. I guarantee you there is way more (and higher quality) support for the Megasquirt available than for ANY other EFI controller.

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    Quote Originally Posted by shiftless View Post

    I build fuel injection systems for a living, and the Megasquirt is about as simple as it gets. I had the thing wired up to the car and running the fuel injectors in about 4 hours before I quit on it yesterday evening. Then today I tuned it while cruising around town, showing off to my buddies, etc. As of this moment I am sitting out in the hospital parking lot using the net. The fuel map is completely dialed in and pretty much flawless. I've been driving around for hours racing and cruising.

    I mean the time that you will put into eliminating the OEM PCM, obviously not where you are now.




    Quote Originally Posted by shiftless View Post
    A race car? Uh, no. This is a full street car. My ABS and factory gauges work just fine. I have no use for traction control and I'm glad that my car did not come with that option. The diagnostics are just about as useless to me. I can identify any issue just as quickly by simply looking at the sensor readouts.

    Quote Originally Posted by shiftless View Post
    No thanks!
    Perhaps you should look at the Megasquirt, then. The driveability is exactly the same as it was before. I guarantee you there is way more (and higher quality) support for the Megasquirt available than for ANY other EFI controller.
    Quote Originally Posted by shiftless View Post
    The stock PCM will be left to control the transmission and other mundane chores, until I can replace those functions one way or the other.
    I didn't think there was any DFCO implementation in MS... On modded cars I usually find 2-7 mpg back with it (7 being the high side for injectors whose minimum pulse is still too large, but still 3-5mpg on stock setups). That's what I was talking about with mileage.

    I have troubleshot a non-working MS install and tuned it, and spent many hours reading, I'm not in the dark about it all.

    You didn't say how you would keep your guage cluster or ABS working either, and the guage cluster alone will be costly to build out with aftermarket guages and your factory cluster is useless without the PCM.

    At any rate, there are many people who are not aware of the flexibility of our PCMs, and I just want to shed light for anyone who doesn't know. Good luck with the car and have fun at the same time.

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    I didn't think there was any DFCO implementation in MS...
    Does that stand for decel fuel cutoff? If so, yes it does have that option. Not sure if it's in the "standard" MS code but it's in the "extra" code for sure.

    On modded cars I usually find 2-7 mpg back with it (7 being the high side for injectors whose minimum pulse is still too large, but still 3-5mpg on stock setups). That's what I was talking about with mileage.
    Ok, that makes sense. That option definitely helps with mileage.

    You didn't say how you would keep your guage cluster or ABS working either, and the guage cluster alone will be costly to build out with aftermarket guages and your factory cluster is useless without the PCM.
    If that's the case, then I'll just leave in the PCM to control all that. I don't necessarily have to delete the whole thing, I just want to be able to tune the fuel, spark, etc. on the cheap. The PCM can stay to handle all those mundane details. I did take pains to not hack up the harness much so that I can return it back to stock later on if I sell the car or decide to go a different route.

    At any rate, there are many people who are not aware of the flexibility of our PCMs, and I just want to shed light for anyone who doesn't know. .
    Alright, got ya. FWIW I have nothing against the stock PCM. I agree that it is very powerful and flexible. I just didn't want to spend a bunch of money to tune it. Thanks for the well wishes.

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    Just an update, I had to make one small change to the crank/cam sensor input circuits. On the stock vehicle these signals are +12V. The Megasquirt would really prefer for this to be +5V or less. With the input circuit set up as listed above, the MS will often not power on correctly due to too much voltage on the input pins. I solved this by connecting a 10k resistor from each of those circuits to ground.

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    TunedbyFrost.com Tuner Frost's Avatar
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    What is the internal resistance (impedance I guess) of the input?

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    You mean on the MS cpu? Not sure.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Yeah on the MS side. should be *really* high...


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