Increasing coil dwell time through a factory 1989 RS ECU

[wildturkey]

I'm looking for help with a possible "workaround" to a little problem.

I'll be doing the Bosch HEC 716 coil mod but they like to run more dwell time than what the factory RS ECU provides........and from what I'm told....there is no dwell time adjustment in my Unichip software

The Bosch coils like to run 4-5ms (milliseconds) of dwell time.......whereas the factory RS ECU only pulses at around 1.7-2ms

The factory ECU WILL run the Bosch coils............but they run better with more dwell

I've been told of a possible ECU mod to increase the dwell time on the factory RS ECU to 4ms

Below is all the info that's been given to me so far and I've asked for a more detailed walkthru...

For those of you "electronically minded" (I'm not ;D).....how simple does this mod appear at face value?..........think you could do it?

"If you know somebody who is good with analogue/digital electronics, im sure a small circuit could be made to turn the 2ms pulse from the stock ECU into a 4ms pulse.

It would be a simple version of a duty cycle interceptor, but its pulse time would be fixed and would have a variable frequency"

[Optical]

i think what you want is called a 'monostable multivibrator', just trying to think if you can pick up a kit for it to make life easier

at any rate, i'd try the bosch coils on the dwell you've got first and see if you get ignition misfires. Plus it's having better than having too much

[wildturkey]

lol.....cheers..........I thort u was takin the piss until i googled it

[gotasuby]

i never had any issues with my hec716 coils even with below average plugs

[BC5RA]

Joe, deal with the problem when shows up; if there's a problem at all.

Install them and get a tune. If there is an ignition problem then sort it. I'd be very surprised if there was.

[wildturkey]

 gotasuby said:

i never had any issues with my hec716 coils even with below average plugs

cheers that's good to know...........I'll pm you

[wildturkey]

 BC5RA said:

Joe, deal with the problem when shows up; if there's a problem at all.

Install them and get a tune. If there is an ignition problem then sort it. I'd be very surprised if there was.

cheers bro........prefer to have them running at the optimum dwell time to minimise any coil/ignition related probs I mite get on dyno day.

Have had some good direction from RSliberty members on this one...... and some electronically minded peeps on dobc are looking at maybe knocking up a dwell time workaround

Will let you know how it goes......... ;D

[wildturkey]

just a bit of an update for any other BC5'ers interested in this..........

Jase found these Jaycar kits that have dwell time adjustment

http://www.jaycar.co.nz/productView.asp?ID=KC5442&CATID=25&form=CAT&SUBCATID=347

http://www.jaycar.co.nz/productView.asp?ID=KC5386&CATID=25&form=CAT&SUBCATID=347