Fast idle programming in the ECU: Questions/Requests for chip tuners

VeeDubTDI

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So it's winter time, and once again we have lots of back-and-forth about extended idling and what it does to your diesel engine.

A couple of guys in chat, including TDI mechanics, have asked me to post this thread to elaborate on ideas that I had earlier today in this thread... http://forums.tdiclub.com/showthread.php?p=2023286#post2023286

We would like to see the chip tuners write some code for the TDI that would elevate the idle to 1,200 rpms and cycle the VNT periodically during periods of extended idling, similar to what most large diesels have.

If you don't know already, extended periods (20 minutes or more) of normal idle speed cause several problems in a diesel engine, including leaky turbo seals (self explanatory), wetstacking (excessive carbon buildup), and washdown (diesel condensation on the cylinder walls and contaminating lube oil).

Explanations of these phenomena and why they happen are in the following links:
http://www.thedieselstop.com/archives/ubbthreads/GeneralDiesel1/showflat.php-Cat=&Number=1620200&page=17&view=collapsed&sb=5&o=&fpart=1.htm
http://en.wikipedia.org/wiki/Wet_stacking

So, my question to the chip tuners is this... how difficult would it be to implement such a feature into the computer's coding?

Some potential initiating factors that we dreamt up in chat are as follows:
  • Automatic initiation after 10 minutes of idle
  • Initiate fast idle by pressing Cruise Accel button/switch while stopped
Or, fast idle could be initiated by either of these two inputs (on demand, or automatically). Cancel fast idle with brake pedal or accelerator pedal inputs.

We'd like to hear what you guys think. Thanks in advance.
 
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jsrmonster

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Hi,

It's already done. This was a long project of mine. I've already posted slow and fast idle tunings.

http://forums.tdiclub.com/showthread.php?p=1994130&highlight=idle#post1994130

If you like to cycle vnt, use a simple timer relay cirucit to toggle pneumatic solenoid at desired frequency. It would also be easy to program the n18 circuit to casually burp the vnt actuator (egr disabled of course, with external ccv breather).

I have alot of customers who run their cars all day long, both idling and driving. As long as the egr is blocked, it's no problem, other than it's open loop. A remote starter is also easy to install, been there done it!

Over 2 million miles on RC and counting!

You ask for it, I'll develop it for off-road, marine, racing, military, and everyday use!

Jeff
 
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VeeDubTDI

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Jeff, I'm sorry, but I think you missed my point. The idea is not to have the engine run at 1200 rpms all the time The idea is that the engine runs at normal idle speed except for extended idling periods.

The goal here is to duplicate what Ford does on the 6.0 PowerStroke. The ECU has a built-in fast idle function for the PTO transmission that increases idle to 1,200 rpms when you apply +12V to a wire under the dash. Many powerstroke drivers use this built-in function to reduce the problems associated with extended idling times (hours of idling, overnight idling, etc.).

Simplified: Have a "switch" that will turn fast idle on or off.
 
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bhtooefr

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Or, in pseudocode:

Code:
if idleTime >= 10:
     highIdle()

def cruiseControlAccel():
     if idling == True:
          highIdle()

def highIdle():
     idleSpeed = 1200
     requestBoostPSI(2)
     while True:
          cycleVNT()
          if acceleratorPedal > 0:
               break
          if brakePedal == True:
              break
(sorry about the total lack of formatting, the [code] tag is broken. :mad:)
 
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joevat

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VeeDubTDI said:
Jeff, I'm sorry, but I think you missed my point. The idea is not to have the engine run at 1200 rpms all the time.
me's running at 1200 rpm all da time!!:cool:
 

VeeDubTDI

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Excellent! Then I suppose you don't need my proposed tune. :)

Unless, of course, you wanted a tune that would reduce it back to stock idle on demand. ;)
 
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jsrmonster

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Hi Lawson,

Like I said, no problem. Install daughter board, flip switch or control it with time constants. The ecu works in cold warm and hot open loop and closed loop. It's easy to hook up a fixed resistor to cts and flip switch for high idle, in open loop, re-write sw, done. Control systems are my speciality. I worked in the military for 16 years and built many unmanned robots that required exactly what you are suggesting. Unmanned VW TDI army robots are still running around in the middle east performing reconnaisance, surveillance, and target acquisition.

Jeff

VeeDubTDI said:
Jeff, I'm sorry, but I think you missed my point. The idea is not to have the engine run at 1200 rpms all the time The idea is that the engine runs at normal idle speed except for extended idling periods.

The goal here is to duplicate what Ford does on the 6.0 PowerStroke. The ECU has a built-in fast idle function for the PTO transmission that increases idle to 1,200 rpms when you apply +12V to a wire under the dash. Many powerstroke drivers use this built-in function to reduce the problems associated with extended idling times (hours of idling, overnight idling, etc.).

Simplified: Have a "switch" that will turn fast idle on or off.
 

oilhammer

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There are just too many to list....
OK, Jeff, so how do we sign up? You are saying this is not just software, but some [minor] hardware additions as well? We were hoping it could all be done on the software side. Simply for convenience and 'idiot proofness' it would be nice to not have to flip a switch or anything.

In a similar manner that the EGR automatically shuts off after idling for a few minutes, then the idle speed would ramp up. Some VNT actuation periodically would seem to be a good thing as well.

Although I think 1200 RPMs might be fine for a V8, the TDI might need 1500 RPMs to get the intended job done.

The issue here is not to start the car and let it warm up, but to KEEP the car warm and in particular the fuel flowing. Apperently (I am told, I do not know for fact) that no amount of fuel treatment will keep fuel from gelling at -35 F. If you do not have easy access to any sort of electrical outlet, but would like to get to work the next morning (or home, as the case may be) this extended high idling may be the only way to survive the brutal northern winters in a TDI.

While I have never had an issue with any of my diesels starting in the cold, even my old IDIs, it rarely gets below 0 F here...usually 'cold' for us is +10 F. So folks from 'up Narth' would have to weigh in on this topic.
 
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cheeba

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oilhammer said:
OK, Jeff, so how do we sign up? You are saying this is not just software, but some [minor] hardware additions as well? We were hoping it could all be done on the software side. Simply for convenience and 'idiot proofness' it would be nice to not have to flip a switch or anything.

In a similar manner that the EGR automatically shuts off after idling for a few minutes, then the idle speed would ramp up. Some VNT actuation periodically would seem to be a good thing as well.

Although I think 1200 RPMs might be fine for a V8, the TDI might need 1500 RPMs to get the intended job done.

The issue here is not to start the car and let it warm up, but to KEEP the car warm and in particular the fuel flowing. Apperently (I am told, I do not know for fact) that no amount of fuel treatment will keep fuel from gelling at -35 F. If you do not have easy access to any sort of electrical outlet, but would like to get to work the next morning (or home, as the case may be) this extended high idling may be the only way to survive the brutal northern winters in a TDI.

While I have never had an issue with any of my diesels starting in the cold, even my old IDIs, it rarely gets below 0 F here...usually 'cold' for us is +10 F. So folks from 'up Narth' would have to weigh in on this topic.
We (Southern SK, and other places as well) just had a week where the lows were getting down to -35[SIZE=-1]°F (~-37[/SIZE][SIZE=-1]°C); I've been running with no treatment and had no problems. That said, my car is usually plugged in (1500w coolant heater), but not always. Cars do not like to run in that temperature - all sorts of crazy noises. You can tell that those sort of temperatures are really starting to push the tolerances in the car.[/SIZE]
 

VeeDubTDI

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oilhammer said:
Although I think 1200 RPMs might be fine for a V8, the TDI might need 1500 RPMs to get the intended job done.
I think you're probably right about this. Oil analyses of 1200 and 1500 would probably paint a good picture for you to determine what is really necessary to mitigate the effects of extended idling.

-Lawson
 
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burpod

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i would be interested in this as well. count me in! northern mn winters suck!!!
 
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ive been running the high idle on my last two cars that jeff has tuned. its very nice!! especially when you stuck on the highway in traffic when a normal tdi would cool down fast!!
 

frank p

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1200 hundred sounds about right to me, i do not like the idea of revving any higher with no load on the engine and anything less would be pointless. (i drive truck for a living)
 

dlai

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Makes sense, but I should have said I was looking for a technical reason for 1200 rpms. EGR related? Something else? A number picked from a hat?
 

Honeydew

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Though its not automatic like the PSD and takes ~5min with the engine off to switch, a q-loader type device could do this, it holds three tunes, an example:

1. regular tune
2. winter fast idle tune
3. super cold idle tune w/ vnt actuation

one drawback would be the risk of accidentally driving it with tune 3 loaded since it wouldn't automatically disengage
 
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bhtooefr

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Honeydew said:
one drawback would be the risk of accidentally driving it with tune 3 loaded since it wouldn't automatically disengage
Why not? The high idle+vnt actuation code could probably be snuck into the code for disabling EGR after one minute of idling...
 

Honeydew

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Good point, I guess it would depend on the coding parameters. I was thinking of a tune that turns on the 10 second vnt actuation test cycle like vag-com can.
 

oilhammer

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There are just too many to list....
Software could also be used to make the ECU completely IGNORE any input from the pedal position sensor during this high idle mode. Perhaps something as simple as pressing on the brake would revert it back to normal operation, and then you could drive off regularly.

The point is to be able to use only the inputs and outputs available to the ECU so no extra hardware need be installed...all on the software side would make sense to me. And if it was made to auto-initiate if conditions were met (such as an extended idling of 10 minutes or so) it would be completely seemless and would not need to be reprogrammed for warm weather use since you would not normally need the engine to idle for 10 minutes without any input during the summer. And 10 minutes would be long enough that most instances of drive through, stop lights, etc. would not allow the car to go into this mode.

The other thing we forgot about is security...it would be even better to tie in something with the anti-theft to allow the car's doors to be locked and the alarm set while the engine sat at high idle in the cold. Again, I would think this could all be accomplished by software, but I am by no means the expert in that arena... :eek:
 

compu_85

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Brian, you can already lock the car when the engine is running, you just need a 2nd key to use in the driver's door.

-J
 

oilhammer

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There are just too many to list....
compu_85 said:
Brian, you can already lock the car when the engine is running, you just need a 2nd key to use in the driver's door.

-J
Yes, but if someone busted the window and got in they could drive away with your car... I am talking about actually arming the anti-theft system while the engine is running.
 

VeeDubTDI

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dlai, most fast idle functions on vehicles are 1,200 rpms, which is why I chose this number.

The fast idle function would also benefit people in the summer to keep the air conditioning colder, as it would spin the compressor faster. So, say you wanted to run into the grocery store on a 100 degree day and leave your puppy dog in the car... you could leave the engine running and keep the vehicle nice and cool.
 
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n1das

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oilhammer said:
The point is to be able to use only the inputs and outputs available to the ECU so no extra hardware need be installed...all on the software side would make sense to me.
I've thought about doing this by tricking the ECU into thinking the brake and go-pedal are being pressed to activate the built-in governed high idle mode. No special custom tuning needed...only some simple hardware mods.

Basically, you need a toggle switch wired with the brake pedal circuit going to the ECU to sense the brake pedal being pressed. You would also need to modify the potentiometer circuit in the go-pedal assembly to simulate the go-pedal being pressed slightly and a toggle switch to activate that circuit. The go-pedal circuit has a potentiometer attached to the pedal and it shouldn't be hard to connect a resistor in series with one side of the pot to simulate the pedal being pressed slightly. The switch would be wired across the resistor so that the resistor is shorted out for normal operation and open for raised RPMs.

To activate the mod, flip the toggle switch for the brake pedal circuit so the ECU sees the brake pedal being pressed and then flip the toggle switch for the go-pedal circuit to raise engine RPMs above idle. You can do either one or the other first, just not at the same time. To de-activate the mod, flip both switches to the other position.

I've left out a lot of details here as I don't have any schematics/wiring diagrams in front of me. I think it's possible to automate the governed high idle mode that the ECU normally goes into when the brake and go-pedal are both pressed. It would give us an easily switchable high idle mode that is available whenever we want it. One thing about this high-idle mode is that the engine RPMs are governed at ~1200 RPM (1199 RPM reported by VAG-COM). So if you load the engine while in this mode, the ECU will automatically increase fueling to maintain a governed ~ 1200 RPM.

IMHO, an easy way would be take advantage of the built-in high idle mode that the ECU goes into when the brake and go-pedal are pressed and it shouldn't be hard to do it electrically instead of having to step on the brake and go-pedal.
 
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