FW: Crank sensor signal mod

[Atkinson, David]

Hi.  Electromotive sells smaller diameter wheels.  The high number of   
teeth leads to better ignition timing and injection event timing.  I'm   
pretty sure they use 60 teeth to make the math happy and nice.  Check out   
this link:

http://www.electromotive-inc.com/trigger.htm

Hope that helps!

 Dave

 ----------
From:  djp
Sent:  Tuesday, June 24, 1997 9:04 AM
To:  DIY_EFI
Subject:  Crank sensor signal mod

        I was wondering if anyone had ever modified the output signal of   
a
crank sensor to make it work with an ecm that was expecting a different
sensor/wheel combination?

        Here's a little more info if you're interested:
I have a Honda CBR600 F3 motor in an mini formula style car (FSAE car).   
 The
engine normally is carburated and has a distributor less ignition, right   
now
it has been converted to turbocharged and efi.  The problem is that I had   
to
replace the stock crank sensor and wheel( 12 -3 toothed) with the efi's
(electromotive) sensor and wheel ( 60 -2 toothed).  My current setup   
works but
is a pain to deal with.
        This engine has a few interesting features,
1) 4-stroke, 4 cylinder, dohc -> so I can use a efi system made for 4   
cyl. car
2) the crank shaft doesn't poke out of the block since the transmission   
is
also
   packaged in the block-> the crank sensor wheel is mounted to end of   
crank,
   but under a side cover that needs to be sealed.
3) The rotor of the alternator is mounted to other end of crank, under   
another
   side cover.
The biggest pain is that the efi's sensor wheel won't fit underneath the   
stock
engine side cover.  I have a custom fabbed one that is plain old ugly and
plagued with oil leak problems.  I also tried extending the crank shaft
through
the side cover with a seal around the shaft, but I could find anything   
that
could hold up at 13,000 rpm.

This all boils down to: I want to use the stock crank sensor but convert   
its
signal to work with my efi.  The efi's wheel has a lot more precision (60   
 -2)
than the stock (12 -3) wheel, but I was wondering how important that   
precision
was, or if they went to 60 teeth to make the math and degrees work out   
nice.
Also, I have the option of using the frequency of the three phase voltage   
from
the alternator as a speed indicator.  (wouldn't suffer from any kind of   
belt
lag or slipping since its mounted to the crank)

Am i crazy or can this be done?

Dick Protus
GT Motorsports
404-894-3222
djp at comlab.gtri.gatech.edu