One of the things we discovered when attempting to start Mark's engine
is incorrect installation of the crank angle sensor. Don't assume it is correct
when you get it from an engine builder. It is easy to mis-install it with
one tooth off.

Tracy instructions
helped but they were not the whole story. There are two marks on the pulley true
enough but the paint can be worn off. The pulley's are also notched. It is
the first mark or notch that is 5 degrees AFTER top dead center when rotating the
engine in the correct direction and it is the one you use to install the crank
angle sensor.

Take out the crank angle sensor. Look at the bottom of the shaft
where the gear is. Set it and install it according to the shop manual.
Everybody needs a shop manual so download it from:
http://www.wankel.net/~krwright/cars/rx7/manuals.html
Print out the pertinent instructions and take them to the
hangar with you. Don't leave home without them.

If the stud that holds the crank angle sensor in position is not
near the middle of the adjusting slot the crank angle sensor is not installed
correctly.

Mazda engines don't come with degree wheels so Tracy's instructions don't help
much if the crank angle sensor is installed incorrectly. This was the
case with Mark's engine. Set the engine to the first notch on the pulley.
Use a pointer to indicate the position of 5 degrees AFTER top dead
center. You then need to count the teeth on the starter ring
gear and  rotate the engine to the proper settings. We counted 120 teeth
on the ring gear so each tooth is about 3 degrees. It is actually much easier
to use the starter ring gear teeth to set the timing.


Paul Lamar ...No rotor no motor.


Good post.

I've been meaning to write a blurb on my website about this concerning the
86-91 engine blocks that use the crank angle sensor.  One thing of note here
that should be added has to do with the potential incompatibility of the front
hub and main crank pulley (closest pulley to the front cover that has the
yellow and red timing marks).  I discovered many years ago that, while there's
a consistency in the asymmetric bolt-pattern on each front hub for the pulley
set, the relative position of that bolt-pattern differs (seemingly from model to
model) with respect to the absolute position of the front keyway on the e-shaft.

Zero-base timing is absolutely relative to the e-shaft as all e-shafts are made
identically, with respect to the position of the front rotor rotated to TDC, with
the front keyway located at exactly 9 o'clock (270* degrees).  However, even
though as I've mentioned the bolt pattern on the front hub only allows a crank
pulley to be bolted on one way, the relative location of that bolt-pattern with
respect to the e-shaft's TDC location of 9 o'clock can differ.  It's therefore
possible (and somewhat likely) to have a mismatched front hub and crank pulley
pair, therefore throwing the timing marks as far off as 16* either direction, be
it advanced or retarded.  Whenever I take my tuning trips out of town to
work on some of these Rx7's, I take a known-good front hub and pulley pair
with solid, known-good 5* and 20*ATDC degrees marks (yellow and red,
respectively) if I encounter a problem with knock or very high EGT's with
poor engine power and low response.  This is that common of a problem with
the older blocks.  It happens easily when assembling a motor in a shop that
might have many other sets of torn down engines laying around with multiple
spare hubs or crank pulleys.

For you guys that are assembling a 2nd gen style motor that might be unsure
as to the authenticity of your front hub/pulley pair, I recommend purchasing
a Racing Beat underdrive pulley/hub (one machined unit) or borrow a buddy's.
The timing marks on them, even though they're 10* 0* 10* 20*BTDC, will
be known-good.

B
___________________________________________________________________________
Brian D. Cain -/- Dallas/Ft. Worth, TX -/- bdc@bdcmotorsports.com
BDC Motorsports | Performance Rotary Engines, Specialized Porting, EFI System Installation & Tuning
MSN bdc196@hotmail.com, Yahoo! bdc196, AOL Symajhi, ICQ# 1733105
http://www.bdcmotorsports.com -/- http://bdc.cyberosity.com





I've been through this with my 20B that came from Atkins Rotary with a 12A
front cover.  We learned as we started the dyno runs that the pointer on the
cover had no relation to the timing marks on the pulley.  We found the TDC
on rotor 1 by centering a tip seal between the leading and trailing plug
holes; then rotating the rotor 60 degrees (180 degrees on the e-shaft).  We
used both a circular angle gauge and counting of starter ring gear teeth on
the flywheel to mark the TDC, and the point 35 degrees BTDC for setting the
CAS according to Tracy's instruction for the EC2.

Once you have the 35 BTDC position, it is a  simple matter to set the CAS.
The only thing that matters is that the two toothed trigger is lined up
exactly with the reluctor sensor when the engine is at 35 deg BTDC on rotor
1.

BTW; maybe all the starter ring gears don't have the same number of teeth.
Mine ('86 auto trans version that Tracy recommends) has 124 teeth, 2.9
degrees/tooth.  Not a big difference from using 3.0 for smaller variations,
but 62 vs 60 for 180 degree rotation could throw things off a bit.

Al



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