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Old 02-23-2010, 12:19 AM   #1
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Default Megasquirt on this? (1950 ******)

One of the reasons that my miata isn't 100% complete after almost 3 years of ownership is cause of my many projects aside from my car. To stick with the title, I have a 1950 ****** CJ-3A. It sports a whopping 134 cubic inch flat head 4 cylinder with a 3 speed tranny. It has 5.38 gears and won't dare go over 50 miles per hour. My newest crazy idea is to convert it to fuel injection. Usually the way this is done is by using a TBI setup from a chevy, but I want to weld bosses to the intake an run 4 injectors.
My question is this:
Can I use an MS on this application for just control fuel? The spark comes from the distributor, so I have nothing like a CAS or anything cause then again, what did in 1950. Anyone have any experience with a similar application as this? / Can this even be done?
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Old 02-23-2010, 01:03 AM   #2
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What you are describing is exactly what the megasquirt was originally designed to do .

The megasquirt & spark extra code was something that came later on as a result of people wanting to run things other than SBCs and SBFs with EDIS systems. There are a few ways you could go about doing it (but keep in mind, I have 0 experience with either of these). IIRC, there is a way to use the pulses from the distributor to time the injection, not sure about stuff from the 50's, but I'm fairly certain that there is some sort of output to drive a tach? If so, thats what I think you would use.

The other way to do it would be a custom trigger wheel setup. You can get wheels from diyautotune, which you would mount to the crank pully in conjunction with a VR sensor to feed the engine speed and crank angle to the MS, which could then be used for fuel only.

Check and for more info. If you decide to do it, keep us posted. Sounds like a cool project .
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Old 02-23-2010, 02:05 AM   #3
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Short answer: yes.

The primary reason why the primary trigger input circuit on the 3.0 board is so annoying to work with is that it was originally designed specifically for triggering off the points in a distributor, not a hall-effect sensor.

If you want to do semi-sequential (two channel) injection, you'll need a 36-1 crankwheel, magnets mounted on the crank pulley, or some similar device that gives an absolute #1 TDC reference. But as Jeff said, you can, if you choose, simply attach the MS directly to the distributor and use it to run fuel only in a single-channel configuration. You could even use it to control spark (retaining the stock ignition coil and distributor) by locking down the distributor's internal advance mechanism (or, as said earlier, using a crank trigger.)
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Old 02-23-2010, 09:33 AM   #4
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Awesome. I'll have to communicate with DIYautotune and see exactly what I need. Thanks for the input guys!
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Old 02-23-2010, 10:32 AM   #5
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Yup, and we help people with these types of projects all the time.

Here is a pretty relevant article form where Jerry converted his Nova to TBI:
MegaSquirt Carb to EFI Part 1: TBI Fuel Only

And another article explaining all about measuring for and then installing a crank trigger wheel:
How to use DIYAutotune.Com's crank triggers

Send me an email ( and we can get you squared away.
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Old 04-05-2010, 04:40 PM   #6
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Thanks for the links. I'll be checking those for sure....
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Old 04-06-2010, 11:29 AM   #7
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So like I mentioned previously, I don't want to run TBI, I want to run EFI similar to a miata's injector system. In fact, if my miata engine is 112 ci. and my stock 240cc injectors can handle about 7psi of boost, then I'm sure I could use that same miata fuel setup and injectors to supply enough fuel to a 134ci flathead NA 4 cylinder. The '99 miata 1.8 makes about 140hp flywheel, my '50 ****** 134ci makes somewhere near 70?
Also shoulda mentioned this in the first post...My 1950 ****** is 6v, not 12. It can easily be converted to 12v, but can a MS and a miata injector setup even run on 6v?
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Old 04-12-2010, 09:48 AM   #8
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The MS will require a 12v system. 9v is minimum to turn on. 12v is also needed to drive the injectors properly.

Sweet thing about the MS is it is esigned to run in just about every mode possible. low/high imp injectors. 1 Inj or 12. etc... Having run on TBIs many years ago, (Olds v8, Dodge V8) I believe the route you are taking is the best. The way MS times squirts does not provide even fuel delivery with a TBI. Port injection resolves the issue.
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