can I hire somebody here?

[tcmtech]

I rather think this is being way too over thought.

But if the load to a motor is suddenly cut and the engine starts accelerating even once the energy supply to that engine is cut it will still have inertial mass that will keep it accelerating.

Thats like saying the main capacitors in a power supply will gain voltage and energy over what the input source was producing if there is a high current load on it while the power source itself was shut off! We all know better than to think that happens!
As soon as the power source stops supplying energy everything starts slowing down as it stored energy gets used up!
If any of you have over unity fly wheels (that actually work) sitting around I will pay you what ever you want for them!

And yes when you do stall a flywheel instantly or at least very quickly it is rather like shorting out a incredibly large capacitor that has near zero ESR! Massive destruction of what ever tries to discharge its stored energy!

Electronic rev limiters are standard issue on gen sets and about any modern gasoline engine other than whats in a factory vehicle. Trust me on this. Just ask around on one of the automotive or off road forums about rev limiting and what happens as it works.

As far as the moment of inertia of a flywheel that is what is keeping everything moving smoothly through one revolution of the engines crankshaft and connected parts but every revolution has several intake compression power and exhaust cycles happening in that one revolution. The instant you take away all of the power producing strokes by shutting off the ignition source or fuel source all you are left with is pure mechanical drag of one type or another. There is no possible way for RPM's to ever increase after that without adding more energy from some place.

As far as the aftermarket MSD units they are microprocessor controlled and will far out do any homemade unit you will ever build for the same price. They have soft rev limiting and many other optional functions as well.

Here is two MSD web sites. MSD Powersports - High Performance Ignitions and Accessories for Powersports and MSD Performance Group
Both should be able to answer your questions about spark based ignition far better than I can.

If you have $20 limit on the project than your not likely all that serious about this. If you feel the need to prevent engine over speed than you know what your engine and what ever it is in is worth and $20 does not likely buy any replacement engine for anything I know of thats of value to me!

 

[joe_rocket]

I appreciate your input but I am not looking for a rev limiter.....

 

[tcmtech]

So what exactly are you needing something like this for?
What specifically is the engine in and why do you specifically need to sense a rate of change and not a upper safe RPM limit?

What are you exactly doing basically?

 

[joe_rocket]

here is my car, which I have wanted for 15 years now before I could afford it.

can somebody please help me build this? it is beyond my knowledge, but it sounds like it is easy to do for somebody that knows electronics.

 

[tcmtech]

And why a rate of change for engine speed? What gains or purpose to use that form of control and to do what with it exactly?
Sorry but I am still rather lost on the actual purpose and possible usage at this point.

 

[joe_rocket]

if you want to build it I'll tell you so you know what you are doing, but if you don't want to build it, let somebody that can do it...
I am thinking you can't ....

 

[tcmtech]

In response to your PM.

I am trying to help but for people to design electronic circuits they also have to understand the exact purpose and function it is to serve as well. They are not magic little devices that just do something just because.

Without knowing what they are working with and what function they serve there is no way to actually build something to serve that purpose.

Sensor signal and control interface circuits are rather application specific. Just saying that it uses a HEI tack signal and works on a car doesn't tell anyone anything useful.
Knowing what exactly the output is intended for is a very critical part as is knowing what rate of change and what upper and lower limits it has to work on and why as a well.

If its just to turn a indicator light on or something simple and non critical its simple enough but if its going to turn on or turn off a important vehicle or engine function that could be very dangerous or incredibly damaging to it.

 

[joe_rocket]

it needs to click a small relay, something around the size of an axillary fuel pump relay.

edit, it would be very nice to have an LED to know that it is infact working.

 

[joe_rocket]

Knowing what exactly the output is intended for is a very critical part as is knowing what rate of change and what upper and lower limits it has to work on and why as a well.

sorry, I missed that part, I thought I posted this before, a couple times, but I will elaborate..

here is how i figure it, the engines low RPM is 600 rpm and high RPM is 6000 (but say it is 9000). being an 8 cylinder, 4 stroke
at 600 RPM it fires 300 times per minute divided by 60 = 5 pulses per second which is 5 Hz (?)
at 6000 rpm (if the above is correct) it is 50 Hz
and at 9000 rpm it is 75 Hz

it doesn't have to be super accurate, but it needs to be consistent (if that makes sense?)
and it needs to have some sort of knob to adjust the rate at which it trips.

I would guess a baseline would be around 2000 rpm per second (2000 / 2 / 60 = 16.6 hz)
so if the acceleration rate is greater than 16hz it should trip....

 

[mbarazeen]

but it may make trips when you give an accelleration at neutral? since normally the rate of change when we check the engine or do some practice to see its run at neutral is very higher than that of with load or on road???

since you need a complete working circuit like ready made one, i dont think any one would get interest to do it, if you need building blocks to assemble it your self you can see many helping hands.

let me see if i atleast can post a complete diagram shortly.

 

[joe_rocket]

ok, thanks..

 

[mneary]

I'm guessing that you want to restrict how a third party treats your vehicle, such as a parking valet (or a son/daughter). Or you want a way to detect when it's taken out of gear (intentionality of not) without putting switches on the transmission/clutch.

 

[Mikebits]

Looks like we have similar taste in cars. What year is yours? Mine is 96.

 

[joe_rocket]

Nice car, my friend has an 02 Camaro. Mine is an 84 vette that first had crossfire injection.

 

[Roff]

Post deleted.

 

[tcmtech]

here is how i figure it, the engines low RPM is 600 rpm and high RPM is 6000 (but say it is 9000). being an 8 cylinder, 4 stroke
at 600 RPM it fires 300 times per minute divided by 60 = 5 pulses per second which is 5 Hz (?)
at 6000 rpm (if the above is correct) it is 50 Hz
and at 9000 rpm it is 75 Hz

Hmm... My math says 4 power strokes per revolution times 9000 RPM then divided by 60 seconds equals 600 Hz.
Each cylinder fires at 75 Hz but there are 8 of them running off of 1 distributer.

And your stock engine will fly apart long before it gets to 9000 RPM anyway regardless of how slowly you get there.

 

[joe_rocket]

ok, well you understand what needs done then, can you build it and if so, how much?

 

[tcmtech]

I dont really know what needs to be done or why.
I work with industrial electronics and control systems as part of my personal business. I have also done a few fairly complex retrofit jobs of putting stock electronically controlled engine and drive line systems in older vehicles that did not have them.Some of what I have done is also modifying factory system components to work with different inputs or redesigning automotive components to work on different applications. Many of these applications of them being my own.

When it comes to vehicles I am more a mechanical modifier but with the electronics I am more of an analog signal conversion and power systems guy than anything else.

You still have not said what exactly your controlling based on rate of RPM change though. I watched my pickup today while in town and I saw many points where a simple downshift from drive or overdrive to second produced a 1500 - 2000+ RPM change in less than a second just under normal driving conditions.

If this circuit you want is to trigger an alarm it going to go off constantly. If its a fuel miser device that shuts the fuel pump or other critical engine system off if someone accelerates to fast your going to wreck stuff. Almost all vehicles that have computer engine controls will not take having constant fuel system shutdown cycling without problems or damage.

I am just guessing but I have enough experience to know when to be suspicious of people who wont explain exactly what they want to do as an end result with something.

Does this device have to be manually reset after it triggers or automatic? And if automatic what is the reseting point or conditions that it has to work on?

 

[joe_rocket]

at ANY time over 2000 rpm & has a trigger rate greater than X it should fire (tripping the relay), as soon as the rate is decreased below X threshold it should reset (releasing the relay).
It should work at a minimum of every 1/2 a second, the faster the better, (down to about 1/5 of a second maybe.)

I would also like to have it not only control a relay for a secondary fuel system but also use it to unlock my converter, but I assume both can be ran off one relay (I have an electronic transmission but carb on the car)

-edit-
this is just a custom deal for me and is probably why there is nothing on the market as they have made virtually every controller out there already... I also talked to a guy i know why programs aftermarket fuel injection systems and he also thinks it's a dumb/bad idea... but it's what I want. I don't see why it is such a problem, it's not like i have nitrous or something?

 

[tcmtech]

Ah! An electronic transmission controller interface, now your talking my language. I have a PCS PCS - Powertrain Control Solutions - Home unit on my old 1985 Ford pickup with a propane fueled and built for heavy towing 460 in it with a customized E4OD super duty transmission behind it.

The PCS units are not cheap but they out do anything homebuilt or OEM factory ever can do in terms of transmission control and functions. I had mine set up for torque converter lock up in all four gears so when I am pulling it felt like it had a 8 speed automatic in it! Plus I had a dash mounted shift firmness control so I could change the shifting firmness from so soft you couldn't feel the shift changes when unloaded to so hard that if it was not towing its own weight it would bark the tires between shifts or any level in between!

Sorry but your far better off with factory built control systems. Electronic transmission control is not beginners hack work by any means there is more to it than just on and off signals. If anyone told you otherwise they are dangerously wrong or greatly misinformed.

I did my research on it and loads of testing and home customization of factory stuff attempting DIY system and I still came down to the fact that spending the $800 for the full PCS system I have was worth it being my transmission would about $4000 to replace it if I messed it up on the DIY hack stuff.

The PCS controllers do have auxiliary input and outputs that can be set up to do specific functions as well based on engine and transmission or sensor parameters or personal input from potentiometers or switches.

Damage your transmission once and your out far more than what the PCS unit will cost.