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'Ignition timing, 2nd iteration....'
2000\05\02@111442 by John Pearson

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Thanks everyone for all the responces and offers for help.

I think I will try to tone this down a little. Make it a bit easier.

How about taking the signal from the dist. with mechanical and/or vacume
advance working, and proccessing that signal by adding delays. Safer and
less complicated.

What I am trying to do is smooth out the power from my motor. The car is a
drag car with front engine, rear wheel drive. At well over 1hp and 1ft/lb
torque per 10lbs weight, and street radial tires, accelerating from a dead
stop is very difficult. I read that pro street stock racers use timing
computers to help with traction, and guard their curves with their life.
These computers are not cheap. I think they start at $700.00.

So, perhaps using the original curve from the dist, and tailoring that
before it goes to the ignition module would be a good compromise.

John

2000\05\02@122200 by Michael Rigby-Jones

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<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Tony's code is very clever, and just shows what can be achieved via software alone.&nbsp; However, as he himself has stated, it was only designed for relatively slow reving engines.&nbsp; The trouble with the software only approach is that you have to complete all calculations and keep a pretty accurate counter in between firing cycles.&nbsp; The Motorola uP such as the 68HC332 have a TPU (Time Processing Unit) which is extremely powerfull.&nbsp; It can actually run an engine in steady state with no CPU intervention, leaving the CPU bags of time to perfrom some very intensive maths.</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">I think a good compromise could be met using a PIC with the Capture/Compare units, which would at least offload a good deal of processor time.&nbsp; I have been thinking about a PIC based system on and off for ages, but never seem to quite have the time to sit down and work through it.&nbsp; Maybe this is a good time to put our heads together?</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Your application of traction control might actually be slightly more simple.&nbsp; I presume you need to reduce power once the wheelspin has started.&nbsp; You only need to retard the igniton from the mechanical configured settiing to reduce power.&nbsp; You might even get away with introducing fixed delays that are not proportional to engine speed, which accumulate the longer wheel spin progresses?</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Regards</FONT>
</P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Mike</FONT>
</P>
<BR>
<UL>
<P><FONT SIZE=1 FACE="Arial">{Original Message removed}

2000\05\02@124718 by Alan B Pearce

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You could always use a PIC per cylinder - they are cheap enough, you would not
do this for a commercial design, but then you would do that using a specially
designed chip anyway.

Imagine the puzzled look on a potential car thief's face trying to figure how to
jump start that!

2000\05\02@144756 by andy howard

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> From: "John Pearson" <spam_OUTxeroTakeThisOuTspamCMC.NET>
> Thanks everyone for all the responces and offers for help.

> I think I will try to tone this down a little. Make it a bit easier.
> How about taking the signal from the dist. with mechanical and/or
vacume
> advance working, and proccessing that signal by adding delays. Safer
and
> less complicated.
>
> What I am trying to do is smooth out the power from my motor. The car
is a
> drag car with front engine, rear wheel drive. At well over 1hp and
1ft/lb
> torque per 10lbs weight, and street radial tires, accelerating from a
dead
> stop is very difficult. I read that pro street stock racers use timing
> computers to help with traction, and guard their curves with their
life.
> These computers are not cheap. I think they start at $700.00.
>

Do you need to tweak the timing for that?

I'm just thinking out loud here. Since you have maximum traction when
there's no wheelspin, maybe you could devise a system that compared the
rotation of the front and rear wheels and slightly backed off the
throttle if it detected any slipping, checked again and backed off if...
etc.

If it detected no slipping and your foot still hard down on the pedal it
could nudge the throttle up again until wheelspin started again.

Maybe the lag of the throttle action would make this unrealistic but
until it was  banned (and after too, if the rumours are correct) Formula
One reacers used something similar (but no doubt much more complex) to
great effect at the start of races.










.

2000\05\02@190421 by Andrew Warren

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andy howard <.....musicKILLspamspam@spam@soon.com> wrote:

> > I read that pro street stock racers use timing computers to help
> > with traction, and guard their curves with their life.
>
> Do you need to tweak the timing for that?

   Andy:

   He doesn't have many other choices; traction-control is banned
   in his form of motorsport, but ignition timing curves, gearing,
   and rev limits are "free" (i.e., they can be set to whatever he
   likes) in most classes.

> I'm just thinking out loud here. Since you have maximum traction
> when there's no wheelspin, maybe you could devise a system that
> compared the rotation of the front and rear wheels and slightly
> backed off the throttle if it detected any slipping, checked again
> and backed off if... etc.
>
> If it detected no slipping and your foot still hard down on the
> pedal it could nudge the throttle up again until wheelspin started
> again.

   That's the way the traction-control system on my car (and most
   others) works, and it's fine for keeping the wheels from
   spinning on ice or other slippery surfaces.  It sucks, though,
   for drag racing... For many reasons, some of which are:

       1.  Wheelspin on launch is NECESSARY for the fastest times

       2.  The deformation of the rear tires under heavy
       acceleration changes their circumference (in the wrong
       direction), so the traction-control system will incorrectly
       see slippage when there is none

       3.  Maximum traction isn't developed with no wheelspin,
       anyway; the most acceleration is developed when the tires
       are slightly slipping

   -Andy


=== Andrew Warren - fastfwdspamKILLspamix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

2000\05\02@195004 by Tony Nixon

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> Michael Rigby-Jones wrote:

> The trouble with the
> software only approach is that you have to complete all calculations
> and keep a pretty accurate counter in between firing cycles.

Not neccessarily.

The last software I wrote precalculated a set of variables and these are
used at run time - virtually no math while running. The data is then
available exactly when needed. As I mentioned earlier, I can keep track
of RPM, pos or neg advance, vac adv, dwell and rev limit in about 50
instructions. That is about 25uS @ 8MHz, but it still becomes an issue
at high RPM.

To test the software, I had two signal generators running. One at 500RPM
and another about 6000RPM simulating the timing for a V8. I used a
switch to change signals and as far as I could see the PIC coped OK. I
didn't have a storage CRO to see the changeover glitch though. On the
test bench the PIC could run a single 4 stroke upto 35,000 RPM.

The system has been quite popular with old car enthusiasts because of
hard to find distributor parts, and with people running engines on gas
because 2 data sets can be stored and changed over even when the engine
is running.

I have had ideas on doing another one with more features, but the time
it takes for development to cover a reasonable spectrum of
engines.....oooh the pain. The last time I was 'playing' with this idea
I was using a 16C74 and I could change the timing parameters even while
the engine was running.

There are four basic things needed to make a system work.

 Good programmer
 Electronics wiz
 Someone who knows engines inside and out.
 Time, time and more time.

Even so, it was probably one of the most interesting projects I have
done. Not too bad when you consider the whole shebang used only 1021
words of ROM.

--
Best regards

Tony

http://www.picnpoke.com
.....salesKILLspamspam.....picnpoke.com

2000\05\02@202216 by Plunkett, Dennis

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{Quote hidden}

       Correct, it is around 6 to 10% slippage

       Dennis



> === Andrew Warren - KILLspamfastfwdKILLspamspamix.netcom.com
> === Fast Forward Engineering - San Diego, California
> === http://www.geocities.com/SiliconValley/2499

2000\05\02@210059 by John Pearson

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----------
> From: Plunkett, Dennis <RemoveMEdplunkettTakeThisOuTspamAIRINTER.COM.AU>
> To: spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU
> Subject: Re: Ignition timing, 2nd iteration....
> Date: Tuesday, May 02, 2000 5:18 PM
>
> > {Original Message removed}

2000\05\02@213302 by Brent Brown

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> >         3.  Maximum traction isn't developed with no wheelspin,
> >         anyway; the most acceleration is developed when the tires
> >         are slightly slipping
> >
> >     -Andy
> >
>         Correct, it is around 6 to 10% slippage
>
>         Dennis
>

Just wondering - is this a known formula / observed rule in drag
racing or can it be applied more generally? A little off topic now but
I have often pondered this and tried to figure out my own
explanations, thinking how a micro based traction control system
might tackle the problem of fast starts for ant kind of race car.

Though a slightly different situation, my experience is with two
stroke 250cc moto-x bikes that develop 45-50hp. The formula for a
fast start on soft dirt / grass surface is a high gear, say 3rd or 4th,
and full throttle. As land speed increases the revs drop back
slightly to that magical max engine torque / max traction magic
value and for a while acceleration greatly exceeds that possible
with zero slippage. (My brother and I have verified this by extensive
side by side standing start tests on a grass air strip!) My guess is
best acceleration occurs somewhere around 20%-50% slippage
shortly after the start for as long the engine torque can keep up this
condition.

Similar technique works when stuck in mud at the bottom of a
slippery gully. Put the bike in first gear and it wont budge no matter
what the revs, do the 3rd/4th gear full noise trick and it's amazing
how traction develops.

Probably quite different to the drag car situation but I'm still
interested in the laws at work here. Oh yeah, to get back on topic
you could super glue DIP packaged PIC16F84's, with legs pointing
up, to the drag track for more traction. You'll need around 35000 of
them for two rows 0.25 mile long, but the good part is you don't
need to program them.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile: 025 334 069
eMail:  TakeThisOuTbrent.brownEraseMEspamspam_OUTclear.net.nz

2000\05\02@214056 by John Mullan

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I really know nothing about this, but to me slipping means lack of traction.
I can comprehend the fact that the heat generated by the friction makes the
tires more pliable and tacky therefore improving traction.  Kinda sounds
like a paradox.

John Mullan


{Original Message removed}

2000\05\02@215402 by John Pearson

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Brent,

I know you have something here. I have heard road race drivers will stay a
"gear-up" in rain to help with traction.

I have always thought that if I put a taller first gear in I would gain
time and traction; However, this is not 'tunable'. I would suffer when
track conditions are real good.

John


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{Quote hidden}

2000\05\03@100016 by Allen Demers

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Andy,

To avoid too much lag I wonder if this would work.

How about just skipping the firing of a plug... like an interupt.  You
could detect rotation ratio front to back and if it is way out of sink
you could interrupt the firing of the next plug?  Dont know if this
mechanicaly would be detrimental.

<SNIP>
>I'm just thinking out loud here. Since you have maximum traction when
>there's no wheelspin, maybe you could devise a system that compared the
>rotation of the front and rear wheels and slightly backed off the
>throttle if it detected any slipping, checked again and backed off if...
>etc.

2000\05\03@102723 by Michael Rigby-Jones

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<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Skipping firing cycles will cause unburnt mixture to be pumped into the exhaust which could cause some nice loud back fires.&nbsp; This is never very good for exhaust valves, or indeed the the exhaust system itself.&nbsp; This method used to be used by add-on rev-limiters, but much better methods exist.&nbsp; One traction control system I have seen actually uses a secondary throttle which is normaly wide open, but can be closed by a servo to back off power.</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Mike</FONT>
</P>
<UL>
<P><FONT SIZE=1 FACE="Arial">{Original Message removed}

2000\05\03@105950 by John Pearson

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{Quote hidden}

This is how my current rev limiter works. It cuts the spark to different
cylinders. It is very effective, I know, cause when I get the wheels
spinning I go right into the limiter.

2000\05\03@111848 by Wagner Lipnharski

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If you don't have any way to control fuel injection (via electronic
injection, or primary/secondary throttle system), controlling the
ignition time gives you "some" relative slack on the torque (followed by
throttle delayed control). In any way you "should" burn the mix "inside"
the combustion chamber, if not, as Mike already said, you can say
"goodbye" to the exhaust valves in a short time; "Cam is up, exhaust
valve is closed (from inside the chamber), explosion at the exhaust pipe
generate pressure in both ways, it forces the exhaust valves springs
opening the valves down the cylinder and it can bump the piston head
surface, returning it bumps the pushrods against the cam, so double
problem, or worse, if intake valves are open the explosion pressure
would go back all the way inside the injection system... not a good
thought, not even talking about dirt entering the chamber".

To control the ignition time, or you use a multi-slotted timming (opto)
disk, with one tick per degree or so, or use a software algoritm to
create the required delay. In this case, remember that this delay is
defined in "milliseconds" while rotational delay is defines as
"angular", so in degrees, minutes, seconds.  You need to measure the
actual time between two ignitions, divide that time by 90 (4 cylinders
engine), so you will have milliseconds per degree, then you can generate
the expected delay in "degrees" by delaying the relative milliseconds to
the next ignition time.

To "advance" degrees, you actually "retard less" degrees in a system
that runs with a fixed delayed degrees. Easy.

Processing power? at 10,000 RPM, 4 cylinders engine, you have as much as
1.5 millisecond per ignition time, this is not plenty enough for all the
math and control for a PIC running at 16MHz? You could probably run an
average of 10,000 instructions in this period of time.

Wagner

{Quote hidden}

>      {Original Message removed}

2000\05\20@172611 by Sten Dahlgren

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John Pearson wrote:
{Quote hidden}

In circuit cellar there was an article about an HC11 controled
ignition/fuel-
injection system, cant remeber now but i think it was around 2 years
ago.
check http://www.circellar.com

regards
/Sten

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