Topic: Rev Limiter Update

[GRUBDIGGER]

OK, GOT THE ANSWER I WANTED. NOT A PRBLEM. I ALLWAYS USE CAPS. DONT LET THAT OFFEND YOU. JUST LOOKING FOR AN ANSWER AND NOT bull.

[slideways]

Also the main thing i see as a difference between a rev limiter and traction control was when Goeytex was talking in another thread about how long of a "pause" in ignition this device would be built for. 1/10 second, 1/3 second etc... traction control kills spark for a very very minute period and is almost transparent. This rev-limiter is going to be much more noticeable when it kicks in and will get you run over if you are going to try to use it as traction control. For example when you slide into a corner and your motor shuts off leaving you broadsided in traffic for a second. Don't try to use it for this purpose.

Most of us (myself included) will be using it as insurance for a chain breakage/sudden no-load situation where the valve springs may not keep up for that split second. My purpose will also be for inexperienced drivers in my car that may blow an engine if a drive chain breaks trying to "go" while the motor tears itself apart.

[Rooster]

Or when your son has it in the wrong gear, on a three speed, on a big track....just saying...

[THawley08]

Sounds like another been there done that.......

Sent from my Droid using Tapatalk

[Old Goat]

I have a couple of questions... maybe they've all ready been talked about, but I just got hooked back up to the internet (after six months without it), so I gotta ask.

How does it work? Is it basically just a tach that grounds out the coil kill wire at a certain rpm?
Is it programable?
Does it contain a battery or run off of the mowers battery? If so, how much does it draw?
Will it handle a lot of vibration?
If anything goes bad, internally, will it kill the engine in the middle of a race?

[Jim Knutson]

These things are for saving our engines upon an unforseen misfortune in which without the rev limiter would allow some of these aluminum rod,flywheel, and other potent goodies built motors to rpm through the roof and the side of the block! Traction control is in chassis set-up,tire pressure, type combos, throttle finesse, and extra fried chicken if need be. You won't find me takin a chance-oh no thanks! Thank you again Bill for your hard work and superior knowledge in such a specialty field, Jim.

[Goeytex]

Thanks for the input fellas.

In simple terms this is to save motors and is not for traction control or speed control . But that
has been stated several times already.    

On an 8 cyl car or even a 4 cylinder motorcycle  a rev limiter can alternately or sequentially
control the ignition across all 8 or 4  cylinders and offer relatively smooth control. Especially
for launch RPMs  in drag racing.  This is so you can give it full throttle without blowing the engine
before dumping the clutch,  and I can assure you the tires will spin. So even then it offers no
traction control.

 But on a single or twin the effect of killing a cylinder is much more pronounced, therefore it won't
make a good "governor" , and would be  a pathetic attempt and  even laughable as a traction control device.  

The minimum amount of time the spark is killed is based upon research done by Briggs and others.  This is from
2 to 10 engine revolutions and not a fixed time.  Therefore the unit is user programmable from between 2 and 10 revolutions of kill time so that the best setting for that particular engine  can be used.  The purpose is to minimize backfiring ( since gas is still being pulled into the engine and un-burned gas can build up in the exhaust system )  while still effectively limiting RPM's in case of an over rev condition.   5 seems to work well in my stock engines. But with a lighter flywheel (ARC) less may be needed as the effect may be even more pronounced with less rotating mass to keep the engine spinning.  I believe that George tested 2 different engines with a setting of 5 and the feedback to me was positive. So that is the default setting.

The optional waring light comes on at 200 rpm before hitting the rev limit.  This is to let you know you are getting close
to the limit that you set for your engine.  It ABSOLUTELY DOES NOT AND CANNOT INDICATE WHEEL SLIPPAGE

If  you try to control real wheel slippage with this rev limiter or any other you will be likely be lapped by everyone in the field.  


 

[Goeytex]

I have a couple of questions... maybe they've all ready been talked about, but I just got hooked back up to the internet (after six months without it), so I gotta ask.

How does it work? Is it basically just a tach that grounds out the coil kill wire at a certain rpm?
Is it programable?
Does it contain a battery or run off of the mowers battery? If so, how much does it draw?
Will it handle a lot of vibration?

Ok, I'll answer each question in order.

Q: How does it work ?

A.  A Hall sensor detects the time it takes the flywheel to make a revolution. This time is compared
with a programmed time which is the rev limit set by the user. If the sensed time is shorter than  the
stored time,   the microprocessor turns on a switch that kills the ignition for  X number of revolutions.  
After that the signal is checked again and if the speed is below the rev limit the ignition is turned back
on if it is still over the limit it is killed x more revolutions and so on until the over rev condition is cleared.

Q. Is it basically just a tach that grounds out the coil kill wire at a certain rpm?

A. No. It is more than a Tach. Along with rev limiting it also provides a tachometer output that is
compatible with inexpensive Automotive Tachs like a SunPro  as well as Equus Tachs. There is also
an optional remote LED that can be panel mounted to warn when the engine is 200 RPM from reachihng
the programmed limit.


Q. Is it programable?

A. Yes.  It is user programmable from 3200 to 11,000 Rpms with no chips to buy.  You need an Automotive
Tach or an Equus tach to program it.  The Tach may be left on the mower for Racing or only used for
programming. Your choice  The engine is not running when the unit is being programmed as there is a built
in oscillator that  simulates the engine running at any given speed.  Accuracy is within 50 RPMs

Q. Does it contain a battery or run off of the mowers battery? If so, how much does it draw?

A. It runs off the mower battery and draws about 30 milliamps. That means it will run for about  1000
   hours on a fully charged 30 amp hour lawn mower battery.    It won't drain the battery if that is the question.

Q. Will it handle a lot of vibration?
A.  Every step was taken to make it as vibration resistant as possible.  There are no internal connectors to
come loose and all components are through hole vs  surface mount.  It was designed to withstand a shock
of 100 m/s2.  The sensor plugs into the unit via a sealed 5mm stereo plug.  I recommend putting daub of silicon
on the connector.  To date,  after over 100 hours of testing  I have not seen a failure.


Q.  If anything goes bad, internally, will it kill the engine in the middle of a race?

A.  The kill output is normally  open.  Therefore in the most likely failure mode such as lost power or a blown chip the switch cannot close. So it would simply do nothing.  In the event of a sensor failure  no pulses are sent so a value of zero is seen by the  microprocessor .. in which case rev limiting is completely disabled. The engine runs normally.  If the power switch is accidentally turned off  the engine runs as if no rev limiter is installed.   No system is completely failure proof, but I've tried very hard to  make it so that if there is a failure the worst that will happen is that the tachometer will stop reading out.

Bill

[George Herrin]

Something else to think about. When you hit the limit its obvious, and when doing so I backed off the throttle just a bit. It isn't like a stutter box. It worked flawlessly but then again you get someone that even if hitting the limit never backs off the throttle and is using it like a stutter box, then it may backfire when it refires. I tried that and it iddn't back fire on me. I ran it just as he sent it to me and trust me when I say Bill did his homework well.

[Old Goat]

Thank you very much for answering my questions. It sounds like it should work well.

I just don't know if an automotive style tach would work for me. I use a Digitron with recall and have never even looked at it while I'm racing. I'd probably crash! I just check it after I'm done.

[Goeytex]

For those of you that don't know,  a few days ago,    my good friend and sometimes business
partner Darrell McWilliams was killed in a head on crash.  Darrell did all of my machine work and
helped with the mechanical design of some of the systems that I designed for the military.  He
was one of my few true friends.

Darrell was killed instantly and did not suffer.  He was not wearing a seat belt. No one was
seriously hurt in the other vehicle where 4 air bags deployed. 

Anyway this has set me back a few days but I am back on task now.

Bill

[George Herrin]

Our prayers are with his family and friends.

[racingjohndeere55]

OK, GOT THE ANSWER I WANTED. NOT A PRBLEM. I ALLWAYS USE CAPS. DONT LET THAT OFFEND YOU. JUST LOOKING FOR AN ANSWER AND NOT bull.

 He types like he talks. And he is just like a big ol Texas long horn. Has a point over here, and another point over there, and alot of bull in the middle.

[Jardisvz]

Hi are the rev limiters still available?

[BIG AL 202]

The last time he was on here was 2011. I am not sure if he is still around or not.