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Megasquirt Schematic, 1974 REPU Carb to TBI conversion

Old 03-18-15, 04:01 PM
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WA Schematic, 1974 REPU Carb to TBI conversion



I’m doing a 1974 Mazda REPU Carburetor to TBI Conversion and would like to have opinions/suggestions on my wiring. I used Aaroncakes schematic to make thing easier to see what I’ve changed.
  1. Using 4 coils
  2. Two EGT Probes
  3. TPS is stock GM TBI
  4. Idle is stock GM TBI 4 wire using IAC 1A, 1B, 2A, & 2B (not shown)


Changed the battery connection because my fuse panel only has one B+ connection for all of the fuses.





Last edited by spokanerxdude; 03-18-15 at 04:04 PM.
Old 03-19-15, 08:38 PM
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I guess what I'm really asking is, will anything as it is shown burn my REPU down to it's axles. LOL
Old 03-25-15, 03:05 PM
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the shield of the cam sensor needs to go to the shield of the crank and the - of the cam sensor need to go to the- of the crank, also i would eliminated the sound system 12v from the ecu wiring.
Old 03-26-15, 08:00 AM
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Originally Posted by elturbonitroso
the shield of the cam sensor needs to go to the shield of the crank and the - of the cam sensor need to go to the- of the crank, also i would eliminated the sound system 12v from the ecu wiring.
Thank you. I'll do that tonight.
Old 03-28-15, 09:53 AM
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Your TBI injectors are probably low impedance, correct? If so, then use the main board injector drivers which can handle low impedance through PWM instead of resistors.

And I also agree with removing the audio system from the fuse panel. The EFI panel should be for engine related items only. Set up another panel for the body, and another for audio/accessories.
Old 03-30-15, 07:03 AM
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Thanks for your help guys. The fuse box I'm using has 12 spot so the sound system was more a space filler than anything else, with that said I'didn't know not to do that so it was good info.

The fuel injectors are low imp. I all ready have them setup on injA and B with resistors for now so if that doesn't work out I will change them to PWM.
Thanks again guy glad to know I'm not going to go up in smoke.

Last edited by spokanerxdude; 03-30-15 at 08:07 AM.
Old 03-30-15, 03:54 PM
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get the new style ev14 injectors, idle quality its way better.
Old 03-30-15, 07:31 PM
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stock GM TBI throttle bodies use there own type of injectors. Standard injectors don't fit
Old 04-01-15, 07:33 AM
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I did go from 50ish#(350ci) injectors to 80#(454ci)
Old 04-03-15, 12:36 PM
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WA Here is where I'm at so fare.

Here is a link to the thread I started on this conversion.

https://www.rx7club.com/old-school-o...rsion-1081256/
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