Electromotive Group :: View topic - IAC control setting min and max duty cycle?

ETM wrote:

I set the idle targets real low (like 100 RPM) so the IAC value on the engine monitor drops to zero. Then you can change the Min Duty Cycle on the fly. Start high and lower it. RPMs should drop as MinDC goes down. If your limp mode is like a Bosch ICV you will eventually go too low and the RPMs will begin to rise.

To determine MaxDC do the reverse. Set idle target high (2500) and get the IAC value to read 100. Then adjust MaxDC on the fly until you get an idle a couple hundred RPM above the highest you think you will ever need. Be sure to add loads like A/C or Automatic Trans in Drive if appropriate.

Reset values in the Idle Speed screen as necessary.

This is also a job that can be done with a crank signal simulator with the engine off. This way you an look inside the ICV and see where the opening is and set the duty cycles as needed.

Author:	slowMX5 [ Wed Jul 01, 2009 8:50 am ]
Post subject:	IAC control setting min and max duty cycle?
I've just been trying to lower my idle rpm target. I've adjusted the target down and also reduced the values of the error sensitivity. IAC duty cycle on the display indeed responded, reducing from about 25 to 3, however my idle speed did not reduce. Now I know that the IAC works as it is fine on cold starts etc, so I am guessing that my min and max duty cycle settings are out. How do I determine what they should be? This is a 2-wire IAC and it may have a limp home setting (i.e. if the duty cycle falls below a certain point then the IAC door may swing too far letting in additional air as if it lost power).

Author:	ETM [ Wed Jul 01, 2009 10:47 pm ]
Post subject:
I set the idle targets real low (like 100 RPM) so the IAC value on the engine monitor drops to zero. Then you can change the Min Duty Cycle on the fly. Start high and lower it. RPMs should drop as MinDC goes down. If your limp mode is like a Bosch ICV you will eventually go too low and the RPMs will begin to rise. To determine MaxDC do the reverse. Set idle target high (2500) and get the IAC value to read 100. Then adjust MaxDC on the fly until you get an idle a couple hundred RPM above the highest you think you will ever need. Be sure to add loads like A/C or Automatic Trans in Drive if appropriate. Reset values in the Idle Speed screen as necessary. This is also a job that can be done with a crank signal simulator with the engine off. This way you an look inside the ICV and see where the opening is and set the duty cycles as needed.

Author:	slowMX5 [ Fri Jul 03, 2009 6:07 am ]
Post subject:
ETM wrote: I set the idle targets real low (like 100 RPM) so the IAC value on the engine monitor drops to zero. Then you can change the Min Duty Cycle on the fly. Start high and lower it. RPMs should drop as MinDC goes down. If your limp mode is like a Bosch ICV you will eventually go too low and the RPMs will begin to rise. To determine MaxDC do the reverse. Set idle target high (2500) and get the IAC value to read 100. Then adjust MaxDC on the fly until you get an idle a couple hundred RPM above the highest you think you will ever need. Be sure to add loads like A/C or Automatic Trans in Drive if appropriate. Reset values in the Idle Speed screen as necessary. This is also a job that can be done with a crank signal simulator with the engine off. This way you an look inside the ICV and see where the opening is and set the duty cycles as needed. Thanks I'll give it a go. When I got it wrong last time the idle oscillated like mad, probably because when the TEC tried closing the valve further to lower rpms the opposite resulted in the valve opening further raising rpms beyond the reset point I guess etc.

Author:	slowMX5 [ Sun Jul 19, 2009 12:16 pm ]
Post subject:
Well I'm not getting the sort of response that I was expecting. I have played with the minimum duty cycle setting. There is a not a lot of difference between minimum idle speed with a setting of between 10 and 35, dropping it to zero caused a sudden rev rise to 2000+rpm. I have it set to 30. Now the unexpected bit. When the IAC percentage = 0 on winTEC4 virtual dash my idle speed, with a target of 500rpm (lowest allowed), is about 850 to 900rpm, idle advance about 3.5 deg, but when I change the target idle speed to 800rpm, the rpms rise to about 1050rpm. The IAC = 0 still on the virtual dash, the advance is about 7 deg. So what gives? Why the 200rpm rise in revs when the IAC = 0 on the virtual dash in both cases and there is only minimal change in idle advance? What I am looking to achieve is an idle speed of about 850rpm using the idle by pass screw as a base setting of say 800rpm, but the inconsistent response of the IAC valve makes this difficult to achieve. Turning the screw changes the rpm but I can not be certain how much of the air for the idle rpms is actually be delivered by the by-pass and how much by the IAC valve. Turning the valve off is not an option as it defaults to the limp home mode. The need to do this results from a very rare stalling when coming to a stop (literally every 3 or 4 months), each time I get this I have slowedin gear and I suspect that the TECgt lowers the IAC duty cycle to zero trying to hit the rpm target which it can't as I'm in gear - the engine then does not have enough air to idle when I drop the clutch and come to a stop. Current settings are: 70 RPM<Target 70 RPM>Target 1 RPM Rising 200 RPM Falling 35% 55% 1700rpm 1350rpm

Electromotive Group http://electromotivetec.freeforums.org/

IAC control setting min and max duty cycle? http://electromotivetec.freeforums.org/iac-control-setting-min-and-max-duty-cycle-t519.html	Page 1 of 1

Page 1 of 1	All times are UTC - 5 hours
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/