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DIY Rev Limiter


Benno
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I'm keen on rigging up some sort of rev limiter for the escort and reckon it would be pretty cool to get some launch control/2-step. What would be ideal would be a normal rev limiter set to say 7000 rpm with a micro switch under the clutch pedal which reduces the rev limit to say 4000 rpm when the clutch is depressed for some hilarious launches/annoying the neighbours. The escort has standard dizzy and coil setup, nothing fancy. I am keen to rig up some sort of device that triggers a relay which pulls the coil negative to ground when the revs exceed the set limit to cut spark.

Has anyone done anything like this before? I am reasonable at electronics but not feeling super motivated to design and test a frequency counter type circuit from scratch. My first google search didn't come up with much, thought I'd ask here before I pushed on too much further.

I see you can get something like this from AliExpress but not convinced that would be any more reliable then something I rigged up myself. I have also contemplated getting a cheap adjustable shift light, gutting it and hooking it up to the relay contact but maybe not super cheap by the time I bought two.

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5 minutes ago, sidewaysickness said:

I have a Bee-R Rev limiter that I can sell you? Does everything you are asking and has adjustable gain so you can adjust how hard or soft it limits. Surely it could be modded to work?

I can confirm it creates savage backfires/flames/lolz 

How much you want for it?

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3 minutes ago, cletus said:

If you still have an escort diff, you will probably also need a good supply of spider gears/axles if you use it as intended

Yeah? I was more worried about the gearbox tbh, I've seen escort diffs behind V8s with no worries but have seen a gearbox shatter with the massive power of a 1300 haha

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The only problem with the revlimiters on carbs is they use the points as a rpm input. They then switch the coil to make the awesome bangs and get into a feedback loop and are a bit shit.

Jaycar do a shift light kit and they include a ignition cut ciricuit. I tried it on a carb vehicle and it was a bit shit, did it on a injected one and it worked mint

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Vaguely related personal sharn.

We fitted 4 gearboxes to the same Escort on four consecutive Sundays.

On the fifth Sunday we fitted a Capri gearbox.

The next Saturday night the car got barrel rolled.

 

Rotor arms with a spring and weight used to be available that would earth the HT side at a pre set RPM.

I was working in a NZ new petrol Patrol today, it had one factory.

You could modify one to fit your Escort distributor?

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Switch on clutch pedal would probably be a bad idea. What happens when you are trying to shift gears at high RPM? You'd end up key banging and lurching all over the place.

 

Rev limiter with a carb is just a kind of crap idea, unless you can modify the distributor to just really retard the advance to limit the RPM using a small solenoid or something.

 

Or be a true barry and put a flyball governor on your throttle linkage.

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4 hours ago, ajg193 said:

Switch on clutch pedal would probably be a bad idea. What happens when you are trying to shift gears at high RPM? You'd end up key banging and lurching all over the place.

I'm not convinced that is a terrible idea, if I'm driving round nanaing it I won't be reving it much higher then 4K anyway. 

 

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Did some work on this, pretty happy with progress so far.

I've smashed together a basic circuit with some diodes and resistors and am able to fairly accurately and reliably read the engine RPM (+/- 100 rpm) using an Arduino. The circuit is connected to the points output/coil negative terminal. I've got an arduino nano ordered off Aliexpress which should do the trick nicely.

I've ordered a couple of these https://www.aliexpress.com/item/5V-Low-Level-Trigger-One-1-Channel-Relay-Module-DC-AC-220V-Interface-Relay-Board-Shield/32801667044.html and am planning on putting the relay between the points output and the coil.

The relay common will connect to the coil -ve. The normally closed contact will connect to the points, the other contact to GND. So with the arduino I'll be able to pull the coil -ve to GND, essentially cutting spark. When the arduino is not energised everything is wired as normal, so if there are any issues I can just pull the power to it. I will cut spark for a time somehow proportional to the RPM. Will have to do some testing to find out exactly how long this needs to be, unless anyone has any suggestions? Any idea what normal rev limiters use?

2017-09-02 16.31.38.jpg

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