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


The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.