Hello Erik,
As you know from driving my truck, I consider the offroad idle performance to be one of the major wins of our design. This is way more than just map tuning, it's several things being actively managed. I'll share some basics, but ultimately it will boil down to whether your controller has some of the capabilities combined with how well you tune it. For what it's worth, I probably have more time tuning/refining the offroad idle performance than the overall tuning on the 2.5l engine.
This is detail that if you are not interested, just skip to the next article. I know some are interested, so I'll make the long post.
Some definitions:
Idle Air Control (IAC) - typically implies full management of idle via stepper motor or some other variable device.
Fast Idle Control (FAC)- usually a solenoid that just bumps the idle up a bit by allowing a certain amount of air to bypass the throttle plate. Can be thermo-mechanical or solenoid based under ECU control
Some basics:
There are about 5 or so states that we manage IAC:
- Cranking- we set the initial idle during cranking to various positions depending on combined engine/air temperature. We also set other cranking parameters (fuel, spark, etc) based on engine warmup state
- Warmup fast idle- Engine idle is set higher depending on where the engine is at in it's warmup cycle. Very cold could be as high as 1350. Fully warm it's standard idle. Again, multiple fuel/spark tunings taking place at the same time.
- Normal driving- Not idle based on RPM & TPS. Idle Air is off.
- Idle- below setpoint- Variable rate increase of idle air depending on how far & how fast it needs to recover. This is far more than the "low/high" settings upper end hal-tech's & the EMS stinger have. We have three different states with separate behaviours (opening rate, etc). Our controller also controls fuel & ignition in this case as well.
- Idle- above setpoint- Again, variable rate decrease of idle air depending on gap. This one is two state with different closure rates.
- Deceleration to idle- How the IAC behaves in a decel event, when you have taken your foot off the throttle, but are not down to idle control range. EMS & Haltech let you set when idle control resumes, but not how. And no control of rate, bump up of idle, etc.
So how do you apply this to your vehicle? Don't know... depends on the controller. To my knowledge the SDS systems only use solenoid (on/off) type fast idle. To Jake's point, limited usefulness except for very cold.
EMS stingers have a basic IAC approach. Set the target idle, percentages on when it engages, TPS setpoints, etc.
Upper end Haltech's ($1000-1500) have a bit more control over how you manage the idle, but are oriented toward GM type stepper motor controls.
Both of these are better than solenoid, but does not have the granularity or modes of what we've developed for the pinz. And again, we are not just managing air in idle control, but also spark/fuel in different engine conditions. IE: Not just normal map tuning.
So how big of a deal is it? I found significant fine tuning in the rates the IAC was managed was required to avoid oscillation/surging. Not talking about steady state idle, but more idle control under varying loads. I don't see how the other controllers will be able to achieve what we have based on how much time I had to spend with rates & "states".
So you don't want to drive at idle? Remember, if your engine is already stalling/bogging and you try to roll on throttle you first have to catch it up before you can accellerate. I can bog the engine down to almost a stall, then roll on throttle without a blip, burp, or anything. Erik & others saw it in Florida repeatedly.
So Erik, I wish you luck. I can't remember which controller you are using, so you'll have to apply sort out which may apply. The sad reality is that most aftermarket controllers are focused on high HP go-fast applications and do not have some of the features that OEM controller have to have in this situation. Think about it, does your car idle up your driveway?
The good news is that Herbert just put our first commercial install into service. This will provide significant feedback to us on non-hobbiest "get in & drive" performance, which is our target market.
Have fun,
Alan