I'm not sure if anyone's done anything with this, but recently I saw something that compared the output of the crank angle sensor of the older 13B's to the crank trigger wheel output off of the 13BREW and it was disturbing. From what I read, there can be as much as a 5 degree error variance in the output trigger signal from the crank angle sensor vs. the crank trigger wheel's almost completely steady signal. Anyone ever seen this before? It makes me wonder if there



Anybody familiar with any other trigger options other than using the factory crank angle sensor?



B

 

I have heard there is a pretty good fluctuation on the CAS for the T II's I heard closer to 2°-3° at the higher rpms, There are a few crank trigger options in the aftermarket, one is a Electromotive HPX or HPV series igntion and of course the TEC systems, the other is SDS, but the SDS has a problem on rotaries for some reason. I am sure there are more, but I definately know of these two systems with the crank trigger fire.



Electromotive claims less than a 1/4 degree of fluctuation up to 12,000 rpm

 

5 degrees scatter, or 5 degrees variance from one CAS to another?

Remember that the reluctors are not keyed to the shaft (at least that's how

it looks) - there could be some serious manufacturing tolerance there.

Also if the shaft has too much play it can jump around.

Finally, the reluctor that provides the "home" signal is shaped in a way

that can cause problems with adaptive sensor amps.

 

well i have a fd and just changed over to a c.a.s. system in my car and found a cleaner signal for my haltech.

 

the 12a's with the distributor get spark scatter too when they get old and the shaft bushing wears out.



if you thinking about it though the fc style will have a little tolerance, beacause you've got the backlash on the gears, the flex and wobble of the shaft and stuff.



the fd seems to have a different handicap though, its that the harness gets fried and it looses accuracy that way. we've seen a few fd's that just stop running once the car gets hot because the cas wires go open

 

what about the fd one skipping a frame or two and calcualtign wrong timing?

 

Let's not forget about faulty pickups in FB distributors. In building my 20B dizzy, I noticed that some pickups had a scatter while others did not. I wouldn't want to use those pickups on a high HP engine.

 

Wires getting fried is a pretty solvable problem - replace them with

teflon insulated wires, reroute them, etc.

Another thing to consider is than the S4 ECU is underpowered and

overworked. It can get confused at high RPM (not sure how high, probably

not very). I have been able to induce the problem in my fiddling.

Using a timing light, the spark timing will suddenly fall back and

become very erratic. It's not the CAS - it's the ECU.



JSR DEGREES_FCAB *convert degrees to microseconds

LDD TIME_09 *DC 09

STD OUTCOMP_0B *DD 0B

LDAA STAT_08 *96 08

ORAA #$01 *8A 01

STAA STAT_08 *97 08

DEC LEAD6F *7A 00 6F

LDD TEMPFB *DC FB

ADDD CAPT_4136 * Add to last sync pulse time

STD OUTCOMP_0B *DD 0B

SUBD TIME_09 *Did I miss it?

BPL LFBB7 *2A 03

JMP LEAD_FC65 *Damn - just fire now...

LFBB7

RTS *39

 

we asked andrew about that and he says the s4 ecu only has enough power to run like 7500-8000rpms. www.16paws.com

 

nice. Chalk another one up for mazda.