Rev limiter for vehicle ignition

[RPM]

Is there anyone who can help me in my design for a electronic rev limiter? I need to design the bit that gets the actual revs from the motor, ignition coils etc. to get that frquency signal converted to an analog sig, so it can be compared in an op amp. any ideas will be appreciated

 

[stevez]

"Frequency to voltage" comes to mind and the second item on a google search is the datasheet for a National LM2907. Take a look at that - it may give you a place to start and may be exactly what you are looking for.

 

[ahonda55]

Hi RPM , i was thinking of this device few days ago !!
i have an idea to make the LM2907 drive a relay , that relay closes the ignition coil when X RPM reachs.
if you did it or have any information now plz share it with us here .
I appreciate that.
Thank you very much

 

[Russlk]

A frequency discriminator in the digital domain would be easier to do. I did that once with discrete logic but a PIC would be the way to go nowdays.

 

[audioguru]

Shouldn't you also cutoff the fuel injectors when the spark is cutoff for rev limiting? The excessive raw fuel might wash the important oil off the cylinder walls and explode the catalytic converter. :lol:

 

[Klaus]

Shouldn't you also cutoff the fuel injectors when the spark is cutoff for rev limiting? The excessive raw fuel might wash the important oil off the cylinder walls and explode the catalytic converter. :lol:

Quite! I think the whole idea of rev limiting has to be thought thru as to what will happen when the engine power suddely drops to zero and then comes back on full once the engine revs drop down a bit. This could be outright dangerous

I think a throttle limiter that is linked to max engine revs is more appropriate, albeit more complicated to build.

 

[gbyzf1000]

any news for the project??
also in case you design..any kind of this circuit is anyway posible to attach a "shift Light warning"?

 

[audioguru]

My cars have had a speed limiter. Supposedly it is set at the max speed of the tires. It is darn dangerous!

I am passing a slow car on a two-lane road and a huge truck is coming at me. Then the speed limiter activates! It becomes extremely difficult to complete the pass or even get back into my lane without the engine running. :cry:

 

[Nigel Goodwin]

My cars have had a speed limiter. Supposedly it is set at the max speed of the tires. It is darn dangerous!

I am passing a slow car on a two-lane road and a huge truck is coming at me. Then the speed limiter activates! It becomes extremely difficult to complete the pass or even get back into my lane without the engine running. :cry:

What's the speed limit in Canada?, and what's the speed rating of your tyres?, in the UK the highest speed limit is 70MPH (on motorways), but tyres fitted to cars normally have speed ratings exceeding the maximum speed of the car.

 

[Joel Rainville]

My cars have had a speed limiter. Supposedly it is set at the max speed of the tires. It is darn dangerous!

I am passing a slow car on a two-lane road and a huge truck is coming at me. Then the speed limiter activates! It becomes extremely difficult to complete the pass or even get back into my lane without the engine running. :cry:

What's the speed limit in Canada?, and what's the speed rating of your tyres?, in the UK the highest speed limit is 70MPH (on motorways), but tyres fitted to cars normally have speed ratings exceeding the maximum speed of the car.

The highest theoretical speed limit here in Quebec (and presumably in the rest of Canada?) is 100 km/h, or 63 mph, but 120 km/h is usually tolerated. You instantly get a speed ticket at a 121 km/h reading on the cops' radar though :lol:

My mother-in-law had a speed limiter at 175 km/h on her Pontiac Sunfire. When you reached 175, you lost control of the throttle until the speedo got back to 170. It is a pretty scary feeling when the speed limiter engages, I can tell you that...

I never succeeded in engaging the speed limiter on my previous car, a 2000 VW Golf. Somewhere around 200 km/h, I would chicken out. :lol: Around here, when the asphalt goes through 1 winter, it gets so bumpy that anything over 120 km/h is pretty dangerous, let alone 200...

I did get well over 200 km/h in France and Germany with a New Beetle, although I don't know exactly the speed reached, since I tend to *not* look at the speedo past 200 km/h :lol:

 

[Oznog]

It can retard the spark or cut off part of the fuel injectors to throttle back without cutting off the engine suddenly. Cutting short the pulse width for the injectors should be effective.

Ideally the throttle needs to be closed again, but the nature of the direct mechanical linkage makes that difficult. I could picture a spot where the cable housing is cut open and a couple of inches taken out. The 2 ends of the housing are fixed to a pulling solenoid. There is enough slack in the way the throttle cable is routed that when the solenoid closes it shortens up the housing making the center cable too long, so the throttle will close. I didn't work out how the solenoid's going to resist the force pulling the housing together when the throttle is closed.

A light on the dash and/or an alarm speaker makes a lot more sense, frankly.

 

[audioguru]

what's the speed rating of your tyres

The tires in Canada are stamped with a letter for their max recommended speed. The letter instead of stamping the actual speed rating is planned to confuse the general public. Tires have at least 4 speed ratings and a car from the factory has the lowest but most cars are capable of much higher speeds. Few people know what speed their tires are rated.

When I pass another car or a few on a two lane road I go flat-out to make it quicker than a surprise. I don't look at the speedo' but probably reach 175km. My tires are also probably rated for 175km max, but probably with a full load. My car can't reach that speed when fully loaded.