Does the firmware that is in a Tec3 converted to WT4 have a different IAC throttle follower function that was not in the WT3.5.6?

Seems like the IAC opens on some throttle opening (See it in the datalogs too) that wasn't there before causing noticable surging on light throttle. If it is now there how can it be toned down.

Maybe it has to have the full open steps reduced to where the starting "choke" setting is at and the "choke" setting changed to 100% so it will start with some air and not have a surge effect when the IAC runns out to 100% on the throttle follower non-adjustable characterstic. I haven't tried that but I am soliciting some info on how it now works.

The idle control routines have not changed really. If anything is different, it might be updated a little faster than before. The routines are otherwise identical to the 3.5.6 routines and to the TECgt.

THe 100% position on a four wire IAC is always fully open. The changing the min and max dutycycle settings with a four wire only affects the range of the pintle's motion. If you're getting surging you'll either need to adjust your TPS fully closed voltage (there is a fudge factor .08v built in that you may need to compensate for) and/or you may need to adjust the reset RPM's on the Idle control screen. I usually recommend the reset RPM be a 50-100 RPM below cruise RPM and the reset hysteresis RPM be just above or at idle. If you still have surge issues, drop the hysteresis value down below idle a little. You could also set the reset rpm very high so that the only time you really see it is when you're in it anyway and the extra air is unnoticable.

Thanks for the information. I will add some to the TPS closed voltage for the fudge factor.

Its a bit annoying when the IAC position needle wags like a dogs tail about 4 full swings on decel.

For the set rpm above which to reset, I was using the max because in a 4 cyl BMW, the shift points even in modest driving are at or above 3000. Today I tried one approach to 0 and 0 for the two setpoints (rpms to exceed for reset and rpm below before a reset) and it locked out the cyclng. I previously had the rpm below which to reset at 1100 rpm (about 150 rpm over desired idle). I reverted to 1100 and 1500 and it did not cycle (when on the move it rarely runs below 1500rpm). I guess staying away from the trigger rpm setpoints for reset is the best.

What is the need for more than one reset per start? Seems like the logic of where the pintle is at should have to be only one time per start. I don't see resets on early GM units I am familiar with only see the throttle following action.

1. So the surging is back. Let's be clear here, it is not surging at idle speed conditions with closed throttle. The IAC is repeatedly opening fully and closing on a closed throttle while decelerating in gear and closing on traffic ahead at engine speeds between 2500 and 1500 rpm. This cycling is clearly recorded in data logs.

The reset value is at 3900 rpm (can not set higher, the sofware is limited). The rpm value below to allow reset is 1100 rpm. So the IAC cycling is out of the setpoint areas. The TPS closed throttle voltage setting is generously above the actual closed throttle voltage.

Seems like my only alternative is to remove the converted Tec3 and put in my other unit that has the exact same settings and does not cycle the IAC. If this is the fix, then the converted unit goes on the selling block and I run the old WinTEC 3.5.6.

2. Manual text in the Tec3r Manual Verison 1.9.C page 38 last paragraph first sentence reads: "If when revving the engine, the engine rpm oscillates a little bit around the decel rpm ..." What is "decel rpm" The term is undefined. Is the text trying to say the "idle rpm setpoint" or something to do with deceleration?

I think I will be of considerably more help here if you could email me a copy of your program and a datalog showing the problem. I've not seen any system reseet multiple times like that and so I think I need to see some more detail.

The reset during run has to do with the fact that we have to deal with stepper motors from GM, Chrystler, Toyota and many others. GM deals with GM motors and that's it. If that reset was not there, some (not all) IACs start to lose track of position and the RPMs start to creep up. That compromise was taken becasue most of our customers are not Calibration Engineers and don't always get fine tuning, detail settings like IAC step rate. It would be a support nightmare. The system we have now has proven to be mostly trouble free so we haven't felt the need to change things up again. You should have heard the screaming when I made the changes that resulted in the idle controls we have now.

Decel RPM is the RPM at which fuel is turned back on when coasting down. This is set under "Decel Fuel Cut Off." At one time these values determined when the IAC was reset. We have since moved on to having the RPM values that you see on the IAC page.

I will help as much as I can, but I'm going to need to see some more information.

Email sent with attachments from WinTec 3.5.6 tune and data log and WT4T3 tune and data log. Running the unconverted Tec3 now and the log shows no IAC cycling. Further it can be seen on the WT4T3 log, the IAC cycles most of the time with the same IAC and TPS settings. VE maps differ due to changes in WT4 from WT3 as discussed earlier.

Has a remedy come out of this? This sure sounds like what my IAC is doing also.
v3.5.6 converted to v4 using a GM square 4 pin connector. Although, my IAC acted like this with the v3.5.6 also. I finally got fed up with it and turned off the IAC control. I was hoping the upgrade would give me the chance to get the IAC up and working for me. Alas...

What's really funny, there was one point where the IAC was finally working nicely. Turned off the car, went to lunch, came back and it was up to it's old tricks again. Didn't waste anymore time, I just hit the good ol' off button.

Jon provided some feedback instructions. which I will include below:

IT's not really the acutal values of the min and max dutycycles that
matter. What matters is the difference between the two. There is a
glitch that I have never been able to track down that when the mindudty is
below a very low number (usually 2 or 3, depends on the error sensitivity
values), it would actually overflow (wrap back to the max value) and cause
the IAC to do what your seeing. I've attempted to fix the problem several
times and though I had done it several times. It such a minor thing that
i haven't given it too much priority. But, back to the explaination of
what min and max duty do.

The difference between determines the number of steps the IAC has to work
with. In 3.5.6, you have 3 and 106 as the two values. You could just as
easily use 200 and 97 and have the same result. It also gets the minduty
away from that grey area where the overflow might occur. The reason for
this is that when the IAC is reset, it moves a whole lot of steps in the
open direction. With the exception of one case, it WILL move more than
there is space inside the IAC housing. Once the IAC is fully open this is
called maxduty (100%). Then you have down to minduty to work. Moving
both of those values away from the edges then gives you more adjustability
when you need to close the IAC more or less to get the idle you want.

--
Jon Rawlings
Electromotive, Inc.
Firmware Engineer
jon@emi.cc" onclick="window.open(this.href);return false

So, I increased the min duty to 10 and there was less IAC action on decel, but stopped at a rpm above 2000 on decel. I had a road trip to make so I put my unit with 3.5.6 back in which has the 3-106 settings (and does not exhibit this problem). I haven't had time to put the unit with WinTEC4 in and work more with it. My intention is to increase the min duty and keep the spread. If I recall when I first set it up with 3.5.6, I had my remote valve body out to where I could blow thru it and found that if I increased the min/max settings, the valve did not seat (or close) fully. My air flow at closed throttle is such that the IAC need to be on 0 steps or the idle is too fast even with the throttle fully closed (small engine, and probably an TB with leaks around the plate).

Easy to see on a data log on decel, the IAC really rips wide open to full closed repeatedly. On approaching stopped traffic, it gives you thrill when the engine decides to push against the brakes instead of assisting slowdown.

Will post on my rusults.

Interesting. My min dutycycle is 1.

Follow up progress. I set the min duty cycle to 40 and the max to 140 and the cycling on decel stopped. I am the curious sort, so will incrementally decrease the min duty cycle and keep the same separation to the max duty cycle to see where cycling reoccurs at the higher rpm on decel.