sorry to start this if the answer is abvious but i have searched without finding anything.


my question is in regards to the dwell vs rpm. does anyone know what these are in reference too?? just to be clear I understand they're function but i don't understand they're incriments. I don't understand why the # would gain as rpm gains...it should be opposite .

also I want to confirm that the IGN vs TPS is in reference to timing and that it is not a dwell adj.

my biggest concearn here is that do to the rest of the base map parameters loaded by Apexi I can only assume that the dwell has not been optimized to the coils and I would like to play around with the charge times a bit before i go CDI but I have no idea what the amount of change is...

all you great datalogic people please help me.

 

Ok since everyone is jumping on this I'll add another question

does anyone know how many ms a new fd coil takes to reach saturation? and also what is they're rated saturation point or max output at say %50 duty cycle? I have looked all over and can't find any info.

thanks for any insight.

 

Get hold of a good dual gun "O" scope that is made for low HERTZ/cycle systems and monitor the voltage across the input and output sides of an ignition coil. Then change the values for diffferent RPMS, and you will have your answer.

At 8000rpm, the trailing coils fire at a rate of 133.33 hertz/sec and tha primary coil fires ata rate of 266.66 hertz/sec. 266.66Hz means that it fires every .00375 seconds.

We hope that the stock values have already been optimized by Mazda, but their record with the FD is less than 100%.

 

thanks for the response i was biggining to think no one would jump in, yeah i do need to get a scope...one of few things i still don't have (stupid)

But i would like to find out what the pfc settings are set at I.E. DwellL vs rpm @ 8000 -108 ? what is the 108=ms

 

I had a very old dual sweep analog Techtronics that was really designed for radio frequency stuff. I tried to read the injector pulses but couldn't get it to sync properly. Had the same problem when trying to read ignition pulses, so I got rid of it. Otherwise I could test thing like this.

If I had the money to blow, I would buy a new modern digital one, but I would not have much need for it.

 

I have been putting off getting one for a while due to the $1000 range they are in which is a little high for the amount of use it would get. although i have to admit there have been some pretty good units on ebay lately that have gone really cheap.

do you know of any literature on the dwell function? somewhere APEXI must have an explaination...the only mention of it that I can find is in the datalogit manual which consists of, (a.) Dwell? LOL!

 

I came across this before when I was working on a school project and thought it was a bargain for an O-scope. Not sure if the specs are appropriate for your application tho, but worth a shot. This is their Educational Kit but they also have a individual unit for $20 less.

CLICK HERE

 

WOW! thanks,

I'm more interested in a portable standalone unit but the downloadable docs on signal understanding at the bottom of the page looks like it should be a very good read since my understanding on this matter could use a little help

 

99 views c'mon has no one ever investigated this function?

 

On the Toyota Celica forum which has some PFC info, they do not know either and basically say "It aint broke, don't try to fix it!".

I would assume it is already maximized and would not need changing like other PFC functions need when modifying the engine.

 

found a page that has good information on what you asked for.... you might already know this stuff.... but this is new to me and I thought it would be good information for others... so here it goes....

Info on Dwell period

read the section on "dwell period" in this article.....

from what I understand after reading the article (correct me if I'm wrong).... your original assumption that dwell should decrease as rpm increase is correct only in the case of a distributor type contact ignition system, where dwell is associated with the angle between the point of contacts. The faster the engine speed is, the less time the points are in contact; hence, shorter time for the coils to charge resulting in lower voltage.

In the case of a distributorless ignition system, dwell is not limited by the duration of point contacts as in a distributor type system. Instead, it is controlled by the ignitor and it increases with engine speed to maintain a constant coil voltage. This is apparently what makes distributorless type system better than a conventional contact ignition system....

 

)EIB( very good info. that link should prove very usefull for alot of people. yes you are correct that the the dwell/charge time original conception with points style ignition leads to shorter charge time as rpm increase do to the mechanical laws of the system. and that with a digital set-up one could reverse this allowing maximum HT output to accure at higher rpms. and to an extent I agree with this, but the key to HP is to syncronize the HT output to the cylinder pressure which corresponds to maximum torque so the dwell # with a an inductive system should be directley linked to your torque curve. with a CDI setup this is not required because the coil can be run at maximum output all the time with out over heating it.

the reason I am intersted in this function is because I have witnessed some amazing power and drivabilty gains with cars that have back to backed CDI vs non optimized inductive systems and i have also seen dramatic improvements in inductive systems that have been optimized vs out of the box setups. the whole Idea that as long as it sparks it is fine is frustrating to me the spark is one of the most important parts of the combustion and the combustion is what=hp and reliability.

my confusion with the PFC is that the #s in the table do not seem represent a unit of time or dagree so I have no reference to its amount of change to make.

thanks for all the info it seems that I may end up with a scope before this is resolved in which case I will post my findings.....but please if anyone knows about this jump in.

 

sorry forgot too cover the reason the Dwell # should still decrease with rpm.... the idea is to run the coil as hot as possible at all times minus say cruise which is achievable with other ECU's which have a Dwell vs TPS table allowing one to "throttle the coils" . with max. output being the goal coil temp will increase related to duty cycle...as RPM increase so does the duty cycle so in order to keep the the coil from frying itself you have to decrease the dwell time as RPM increase. also in some aplications I have seen coils which require more time to saturate than is possible due to RPMs so this forces you to compromise the HT output for what is mechanically possible.