--- On Tue, 3/19/13, rotary engine <rotaryeng@earthlink.net> wrote:

From: rotary engine <rotaryeng@earthlink.net>
Subject: ignition for rotaries idea
To: "AAA-rotaryeng" <rotaryeng@earthlink.net>
Date: Tuesday, March 19, 2013, 8:23 PM


I  was reading the SDS EFI web site and notice they  don't offer  rotary
ignition support.

This  is just an idea at this  stage.

A simple ignition system  using RX8 coils with a 2.5  ms
dwell time has a  problem.

7000 RPM is   116.7 rev  per  second or 42,000 degrees per

second  or one  e-shaft  degree in .02 ms.

1 ms is 1/1000 of a  second.

So the  ignition will be retarded 42,000 / 2.500  or
16.8 degrees. What is  needed is advance at high  RPM.

In the old days that was done by a  distributor with  mechanical and
vac advance.

That is for  a  real simple system that fires when the
CAS sends a trigger to   the coil. A computer can fix this
but there may be a simpler   way.


Hall Effect sensors are cheap and several can be   used.
Lets say we have 4. The first one is used for 0 to 2000   RPM.
A small magnet would be mounted on the e-shaft  pulley.

#1  0 to 2000 RPM 0 advance for good  starting.
#2 2000 to 4000  14  degrees
#3  4000 to 6000  22 degrees
#4 6000 to 8000. 33   degrees

There is a device called called a data  selector.
It is  just a black box that can select one of  these
HE sensors depending on  RPM. Or the pilot can select  one.

The black box can be controlled  by a computer or  an
analog to digital converter  chip.

These  charts are for cars but we have used a fixed  advance
22  degrees BTC with good results.
If you set it at a  greater  number to compensate for the
coil 2.5 ms dwell that means  you  would have 16.8 +_22 which
might cause starting   problems.

Just thinking out loud here.

Paul  Lamar

Paul,  This  would be a backup for a Hall  effect  sensor failure where the
pilot could select one of the other  timing  points. Might need a toggle
switch to bypass the variable  timing  system and read only one at 22
degrees.
george grimes

Yes built  in back up.

Paul Lamar

Paul,
I have mentioned before that  Kawasaki used a hall  effect sensor to
advance
the timing on their 2  cycles by running a  permanent magnet stator with a
projection and  gapping the hall effect  sensor as wide as you could get it
to  trigger. They got a thyristor that  triggered at at about 50% of  max
voltage and the increase in the sine wave  amplitude with rpm  would
trigger
the ignition sooner. Very effective and no  moving  parts.
Bill Jepson


Yes I remember that. Only a few   degrees.
We are talking 10 and 20 degree difference  here.


Paul  Lamar

On the other hand, 20 degrees of  advance at the pulley is 60 degrees at
the
rotor. It is not some  sort of magic that 20 degrees is plenty for up to
9,000 RPM. Smokey would  have loved the dwell time of the rotary. There  is
plenty of time to  get the burn done and you can use some crap 87 octane
pump
fuel.  No starting problems up to 27 degrees of advance fixed.

Lynn E.  Hanover

"On the other hand, 20 degrees of advance at the pulley is 60  degrees at
the  rotor."  True but that is rather  academic.
The ignition timing is always referenced to the e-shaft  angle and not
the rotor angle.

The word "dwell" is reserved for the  time the coil is on and the current
flow is charging the coil.

I  think you mean the length of time any given "stroke" is consuming
rather  than dwell time. http://www.rotaryeng.net/how-**wank-works.html<http://www.rotaryeng.net/how-wank-works.html


Interesting about the  27 degrees. I guess in the back of my mind I was
thinking of hand  propping.

Paul Lamar

When a large number of non-motor heads are being urged to learn
about this rotary thing, I think the relationship of the piston
engines piston to TDC and the rotary engines rotor to TDC should
be thought of in exactly the same terms.  So, try to remember
that when you put the timing light on a rotary and see 22
degrees that the real timing is 66 degrees BTDC.  That is why 20
degrees at the crank pulley is plenty.

Dwell is good. Think of dwell as the number of crankshaft
degrees where no perceptible movement of the rotor or piston
occurs.  (Engineering / Mechanical Engineering) a flat or
constant-radius portion on
 a linear or rotary cam enabling the cam follower to remain
static for a brief time.  Also used to describe the action of
breaker points in a Kettering style ignition system.  And in
literature as a pause to ponder or consider.

Smokey used longer rods. When stock pistons were required he ran
them backwards because the pin holes were offset to keep noise
down.  He also re-bored the crank centerline and moved the
loaded side throws closer to the bore centers.  Notice that most
racing pistons now have the wrist pin hole well into the ring
lands.  Allows for the longest possible rods.  Thank you Smokey.

Lynn E. Hanover
Incinerating rotary
engines since 1980.

I got you beat :) Started in 1973.


Paul Lamar


I'AM CONFUSED,  again. If the rotor turns one face while the E-shaft turns
one revolution wouldn't 20 degrees on the rotor be 60 degrees on the
E-shaft
not the other way around???/?
                  george



Yes :) 3 turns of the e-shaft one turn of the rotor.
Faces on the rotor. Each face goes through 4 cycles in one rev of the rotor. Intake, compression, expansion and exhaust.

Paul Lamar

Interestingly the position for peak combustion pressure in a rotary is three times that of a piston engine at the "shaft".
From about 15 degrees crank angle ATDC (piston) to 45 degrees ATDC  for the eccentric shaft (but 15 degrees for the rotary [rotor] itself).
Barry Bordes

Did you find a complete electronic copy of the 1981 book Rotary Engine by Ken Yamamoto?

Paul Lamar