output for cruise control

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BlackwoodLabs
Posts: 4
Joined: Tue May 31, 2022 10:48 pm

output for cruise control

Post by BlackwoodLabs »

I'm using a Ford cruise control which uses a 5v input for speed information with a pulse rate around 100hz for cruising speed. So tach data would need to be divided by about 20 to work. I don't see a problem with using a 12v signal instead of 5v.

Is there a way to set up this output from the Megajolt/E? There is no VSS.

Jim

BlackwoodLabs
Posts: 4
Joined: Tue May 31, 2022 10:48 pm

Re: output for cruise control

Post by BlackwoodLabs »

I've been trying to work through the math on this with limited success and I think it looks like I need about a 4:1 multiplier so maybe a driveshaft mounted Vss could work with 4 magnets but it'd be cleaner if I could use an output from the MJ.

Specs I have say the input is 25hz @ 10mph + 20hz for each additional 10mph. So at 25mph it would be 65hz and at 75mph it would be 155hz. At 75mph the engine is turning lass than 2000rpm. 155 X 60 + 9300 pulses per min divided by 2000rpm gives 4.65 pulses needed per engine revolution but 4 should do it.

A tachometer output that is based on spark (tachometer output) is essentially double the ideal rate. It might work, I don't know what the upper limit is for these things.

2000 rpm x 8 = 16000 pulses where 9300 is ideal. In this case the number of pulses needs to be divided by 2.

So is there a way to do this?

THX,
Jim

BlackwoodLabs
Posts: 4
Joined: Tue May 31, 2022 10:48 pm

Re: output for cruise control

Post by BlackwoodLabs »

AHA! One revolution is four ignition events, so it DOES run at tach speed. All I need is an additional tach output. Surely that is possible. The question is, how?

I just checked and the tach output from MJ is already connected to the VSS input on the cruise control. I may just have to make sure the configuration is correct. Has anybody done this?

BlackwoodLabs
Posts: 4
Joined: Tue May 31, 2022 10:48 pm

Re: output for cruise control

Post by BlackwoodLabs »

Funny how it won't work unless the cable is hooked to the carb :shock:

Thanks for your help guys! :mrgreen:

Jim

brentp
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Joined: Wed Jan 24, 2007 6:36 am

Re: output for cruise control

Post by brentp »

Glad you figured it out!
Brent Picasso
CEO and Founder, Autosport Labs
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