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How to replace points with Solid State 277cc Rotax?

G

Gerryo

Jan 1, 1970
0
2 August 2006 7:04 AM
Comox BC

I have a 277cc 2 cycle Rotax engine with point ignition and a built in
charging sytem on the flywheel. We are using this engine on a homebuilt
air cushion vehicle (hovercraft) primarily on salt water. The salt
spray is everywhere. The points become encrusted within a short time
and the engine will not take high rpm's or simply quit. Fresh water
spray around the points produces the same results. Is there a
replacement module that will eliminate the points altogether or as a
last resort a circuit that uses the points as a low current trigger for
a transistor or the like to initiate ignition? I am assuming if the
points are used in a low current configuration the degraded current
carrying capacity would not be as big an issue. Covering the points and
venting them would be my last choice as it makes it very difficult (
impossible) to adjust through an already small inspection hole. Any
ideas will be most welcomed.
Cheers...Gerry

PS. I have thought of replacement Solid State ignition modules for
lawnmowers etc. but apparently the built in charging coil on the
flywheel will not allow this setup.
 
R

Rich Grise

Jan 1, 1970
0
2 August 2006 7:04 AM
Comox BC

I have a 277cc 2 cycle Rotax engine with point ignition and a built in
charging sytem on the flywheel. We are using this engine on a homebuilt
air cushion vehicle (hovercraft) primarily on salt water. The salt spray
is everywhere. The points become encrusted within a short time and the
engine will not take high rpm's or simply quit. Fresh water spray around
the points produces the same results. Is there a replacement module that
will eliminate the points altogether or as a last resort a circuit that
uses the points as a low current trigger for a transistor or the like to
initiate ignition? I am assuming if the points are used in a low current
configuration the degraded current carrying capacity would not be as big
an issue. Covering the points and venting them would be my last choice as
it makes it very difficult ( impossible) to adjust through an already
small inspection hole. Any ideas will be most welcomed.
Cheers...Gerry

PS. I have thought of replacement Solid State ignition modules for
lawnmowers etc. but apparently the built in charging coil on the flywheel
will not allow this setup.

Saran Wrap?

Good Luck!
Rich
 
E

Eric R Snow

Jan 1, 1970
0
2 August 2006 7:04 AM
Comox BC

I have a 277cc 2 cycle Rotax engine with point ignition and a built in
charging sytem on the flywheel. We are using this engine on a homebuilt
air cushion vehicle (hovercraft) primarily on salt water. The salt
spray is everywhere. The points become encrusted within a short time
and the engine will not take high rpm's or simply quit. Fresh water
spray around the points produces the same results. Is there a
replacement module that will eliminate the points altogether or as a
last resort a circuit that uses the points as a low current trigger for
a transistor or the like to initiate ignition? I am assuming if the
points are used in a low current configuration the degraded current
carrying capacity would not be as big an issue. Covering the points and
venting them would be my last choice as it makes it very difficult (
impossible) to adjust through an already small inspection hole. Any
ideas will be most welcomed.
Cheers...Gerry

PS. I have thought of replacement Solid State ignition modules for
lawnmowers etc. but apparently the built in charging coil on the
flywheel will not allow this setup.
OOH! I love it when someone asks a question that I can answer
intelligently. Sort of. Anyway, you can google for breakerless
ignition kit or solid state ignition kit and find many products. There
are also plans on the web for building one from scratch. Here is a
link to a company who makes conversion kits to eliminate points:
http://www.pertronix.com/ .
Here are some links for building from scratch:
http://www3.telus.net/chemelec/ ---->This web site belongs to a fellow
named Gary. He is nice and answers any questions related to his site
quickly.
http://www.jonathanselectronics.com/phpBB_Forum/index.php ----> This
link is from the above web site ( Chemelec) that belongs to Gary.
Good Luck!
Eric
 
K

kell

Jan 1, 1970
0
The points become encrusted within a short time
and the engine will not take high rpm's or simply quit. Fresh water
spray around the points produces the same results. Is there a
replacement module that will eliminate the points altogether or as a
last resort a circuit that uses the points as a low current trigger for
a transistor or the like to initiate ignition?

Yes, view this in a fixed font:


switched +12 v
|
| to coil
,---------+ ^
| | |
| | |
| 2k2 |
| | |
| | _|C
10K | | automotive
| +--------|| coil driver
| | |_ IGBT
| | |E
| /c |
+--1k---| gnd
| \e
| |
| gnd
V
to
points
The transistor connected to the IGBT gate can be any small general
purpose NPN transistor, for example PN2222. I've used a couple of
different coil driver IGBT's. Here's a link to a digikey search page
showing some IGBT's that you can look at. Check the data sheets to see
which ones are actual automotive coil drivers, then go to mouser to
order because it looks like digikey doesn't sell onesies.
http://www.digikey.com/scripts/dksearch/dksus.dll?Filter
 
K

kell

Jan 1, 1970
0
kell said:
Yes, view this in a fixed font:


switched +12 v
|
| to coil
,---------+ ^
| | |
| | |
| 2k2 |
| | |
| | _|C
10K | | automotive
| +--------|| coil driver
| | |_ IGBT
| | |E
| /c |
+--1k---| gnd
| \e
| |
| gnd
V
to
points
The transistor connected to the IGBT gate can be any small general
purpose NPN transistor, for example PN2222. I've used a couple of
different coil driver IGBT's. Here's a link to a digikey search page
showing some IGBT's that you can look at. Check the data sheets to see
which ones are actual automotive coil drivers, then go to mouser to
order because it looks like digikey doesn't sell onesies.
http://www.digikey.com/scripts/dksearch/dksus.dll?Filter

It just occurred to me, it sounds like you have a magneto, in which
case this will not work.
 
G

Gerryo

Jan 1, 1970
0
4 August 2006 7:23 AM

Thanks to every one for their replies! Kell, I have a magneto for
ignition but there is a battery charger circuit on board that I use
for auxiliary lighting . Could your circuit be used if this is the
case? I can't follow the ascii diagram, if you have time could you
point me to a schematic?

Cheers..Gerry
 
R

Rich Grise

Jan 1, 1970
0
4 August 2006 7:23 AM

Thanks to every one for their replies! Kell, I have a magneto for ignition
but there is a battery charger circuit on board that I use for auxiliary
lighting . Could your circuit be used if this is the case? I can't
follow the ascii diagram, if you have time could you point me to a
schematic?

Change your google setting to "fixed font" - there shouls be a link
somewhere near the upper-right-hand corner.

And please bottom-post.

Good Luck!
Rich
 
K

kell

Jan 1, 1970
0
Gerryo said:
4 August 2006 7:23 AM

Thanks to every one for their replies! Kell, I have a magneto for
ignition but there is a battery charger circuit on board that I use
for auxiliary lighting . Could your circuit be used if this is the
case? I can't follow the ascii diagram, if you have time could you
point me to a schematic?

Cheers..Gerry

Like Rich said, all you have to do is click the fixed font option and
you will be able to view the schematic.
All I really know is that the circuit will work on a conventional
(battery driven, dwell based) ignition. Although I said it wouldn't
work on a magneto, I actually don't know; I've never installed this
circuit on a magneto. Might actually work. From what I know about
magnetos, the points break the coil current to create a spark, which is
what this circuit does: when the points open, the IGBT breaks the coil
circuit.
As for the charging circuit, that is certainly separate from your
magneto and will not have any effect. On vehicles with magnetos, the
magneto is not even connected to the rest of the electrical system
(lights, charging etc.).
I have built a few ignition modules with the circuit in the diagram,
used them on my own vehicles, and even sold a few to friends. As long
as you use a good device such as a coil driver IGBT or a high voltage
avalanche-rated mosfet, it won't fail. I've put thousands of miles on
my old vehicles using this circuit, and other circuits that are related
but have a heavier current going through the points. You don't want
heavy points current though, so I didn't post those other circuits.
If you go with a mosfet, pay attention to Rds and coil current. You
could take a look at the IRFP460.
 
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