How to Get a GREAT Idle.........

[TurboGeezer]

Hey guys,

Whats the best way to acheive a great idle with these turbo cars (and I do not simply mean setting IAC, etc.?? This question is meant to be both general:

more timing, less throttle??

less timing, more throttle??

higher TPS??

lower TPS??

leaner mix??

richer mix??

and the question is meant to be very specific:

What tables would I change and in what direction (+ or - )
.....spark? AFR? MAF count? injector constant?..............

I am sure there are different strategies depending upon whether you are in O/L or C/L and whether the engine is fully warmed or not............................whats your experience / thoughts??

Thanks for the help, TG.

 

[Eric Stage I]

IMO, the fuel mixture has the greatest effect. Making it idle richer will smooth it out tremendously and it will help eliminate off idle stumbles. However, in the factory program, its not so easy to richen up the idle when in closed loop by just changing table values, because it will always want to correct back to 14.7 a/f. You pretty much have to go to open loop idle.

Eric

 

[TurboDave]

You'll probably get the best results with an open loop idle chip.
Something that yields about 710-720mv O2 when warmed up seems to work best (on mine anyway). I'm not exactly sure where the mixture is for that, but probably pretty close to 12.5-13.0:1

 

[TurboJim]

You can change the target AF, then raise the high and low O2 window points. I have done the opposite in a few cases to get CO down for emissions.

 

[TurboGeezer]

Hmmmmm...........Idle lock maybe??

I have not tried to do anything with Target AF ratios. I'll have to look at that "manually", as I don't believe T6 has any provisions for that. However, I did have another idea that may essentially create an "Open-Loop" idle without being in O/L.

Could we not use the same logic behind the cell 15 BLM lock:

check the MAF value
If MAF is above 245, replace BLM with 128
If MAF is below 8, replace BLM with 128
Otherwise go to the end of the patch

I haven't worked out the code yet for both checks.........seems like it will not be difficult. However, am I missing something or doesn't this seem like it would work?? If I lock cell 0 and cell 15, then it seems that I could use the PE vs RPM's to adjust my WOT fuel and adjust my idle with either MAF table 1 or injector constant adjustments without the ECM "re-adjusting" my tweaks. What am I missing here or am I oversimplifying a much more complex scenario (I love to just ponder the wierd and offbeat at times)???

TG

 

[TurboJim]

Or you can do like my pal Bruce

Put a WB on it, set closed loop enable temp to FF and adjust yer MAF tables to the desired AF ratio's/performance.

 

[Eric Stage I]

Your right, T6 Tuner does not have Closed Loop A/F. Its ironic, because it does have Highway Mode A/F, which is not used in the factory chip.
Yes, you can lock blm at idle to 128, but how are you going to richen the idle? If you change closed loop a/f to richen it, all the rest of your blm cells will change to try and correct it back to 14.7.
If you go to open loop idle, there is an adjustment for open loop idle a/f already in the program.
Another option I guess (I've never tried it) is to lock the blm at idle to a higher # like 140 instead of 128 to force it to richen the mixture. Just a thought...

Eric

 

[bruce]

Originally posted by TurboJim
Or you can do like my pal Bruce

Put a WB on it, set closed loop enable temp to FF and adjust yer MAF tables to the desired AF ratio's/performance.

Then go on to get the rest of the MAF corrections right, and have lots of fun.


The more cam you run the more self EGR'ing the cam becomes, meaning with the increased overlap, more exhaustget sucked back into the engine thru the longer opening period of the intake valve. Long story told shortly.
So with the additional EGR you might need to add some extra timing, and fuel. But you have to watch for exhaust dilution screwing up the O2 sensor's reporting.
You'll find, each engine likes responds slightly different to what works best at idle. Even differences in Torque converters can effect idle.

 

[ijames]

Instead of the blm lock for idle where I doubt 128 will be ideal for both wot and idle, just use the open loop idle that GM already put in the code. There is a delay before open loop idle that if you set to anything other than some magic value (either zero or 255, whatever the stock chip has) will be the number of seconds before dropping into open loop idle. There is a separate open loop blm (okay, two of them based on coolant temp) so just use that to get as rich as you want.

 

[GNX Guy]

Easy answer, get a Joe Lubrant Chip

Joe

 

[bruce]

Originally posted by GNX Guy
Easy answer, get a Joe Lubrant Chip
Joe

That doesn't answer his original question.

 

[TurboGeezer]

Open Loop Idle??

Originally posted by ijames
Instead of the blm lock for idle where I doubt 128 will be ideal for both wot and idle, just use the open loop idle that GM already put in the code. There is a delay before open loop idle that if you set to anything other than some magic value (either zero or 255, whatever the stock chip has) will be the number of seconds before dropping into open loop idle. There is a separate open loop blm (okay, two of them based on coolant temp) so just use that to get as rich as you want.

Carl,

Are you talking about the time and temp values at locations $400 - $403 ?? Are you talking about the number of seconds before dropping into C/L ??

The prospect of keeping the vehicle in open loop idle and just using the O/L idle that already exists is great, but I am not sure that I am completely following you on this one.

TG

 

[fast eddie]

buy a thrasher chip 25$ cant go wrong exelent idle!!!!!!!

 

[bruce]

Originally posted by fast eddie
buy a thrasher chip 25$ cant go wrong exelent idle!!!!!!!

If there was one perfect chip, we could all pack up and go home.
Combinations vary, and reguire differences.

 

[mweber]

Re: Open Loop Idle??

Originally posted by TurboGeezer
Carl,

Are you talking about the time and temp values at locations $400 - $403 ?? Are you talking about the number of seconds before dropping into C/L ??

The prospect of keeping the vehicle in open loop idle and just using the O/L idle that already exists is great, but I am not sure that I am completely following you on this one.

TG

I think he is refering to location $432, but I could be wrong. I haven't tested it myself yet.

Mike

 

[ijames]

Sorry to post and run before, but it took a while to round up the tuits to look everything up. Okay, this is from reading the ecm listings and the data tables but I have not tested anything. Look in the code at $3C02 and you will see where if in open loop idle mode the FAR is set to either $342C or $342D based on the temperature threshold at $342F. Check Dave Huinker's spreadsheet at gnttype.org for stock values and conversion formulas. At $3432 there is a timer to set how long the ecm idles in closed loop before going open loop. This is seconds * 5, so 51 seconds = 255 or $FF and tells the ecm not to go open loop. I think you would want a brief closed loop idle period so the blm's can learn, so if you wanted 5 seconds set this location to 25 or $19. This value is checked in the ecm code at $EFFD. I was wrong before in that you specify the FAR's, not the blms. There is one potential gotcha that I haven't tested. At $EFF8 the INT is compared to $3430 and if it the INT is too low the test to enable OL idle is skipped. You may need to tweak this threshold but I think it is there to make sure that the BLMs can learn so I'd leave it alone to start. There is a data byte labeled high threshold at $3431 to go along with the low threshold at $3430 but it isn't referenced in the code, so I guess GM was just worried about being too lean, not too rich.

Happy tweaking. Oh, you will probably have to do all this manually with a hex editor if these parameters aren't in T6Tuner .

 

[BM Computer Src]

Originally posted by ijames
Happy tweaking. Oh, you will probably have to do all this manually with a hex editor if these parameters aren't in T6Tuner .

I wanted to mention one thing, if any of our customers would like to have any parameters added to the Turbo Six Tuner, please send us the table address (start and end) and description, so we may add it to the program. Eric Stage 1 was right, the highway A/F was added by request, we did not have it in the older versions of the software.

Thanks to everyone for helping.

Bob

 

[TurboJim]

Originally posted by BM Computer Src
I wanted to mention one thing, if any of our customers would like to have any parameters added to the Turbo Six Tuner, please send us the table address (start and end) and description, so we may add it to the program. Eric Stage 1 was right, the highway A/F was added by request, we did not have it in the older versions of the software.

Thanks to everyone for helping.

Bob

Unless you patch it, highway AF isnt used.

UNless one of you guys found a spot of code that I missed....

 

[TurboGeezer]

Thanks...........

Thanks Carl for your insight. You are right. I'll have to play with this one manually, as you mentioned. T6 does not have these parameters in its quiver. However, Bob brings up a good point. It seems like a great time to add some new features to T6 (sorry Bob, I know that means more work for you). Here are some of the items that I have seen openly discussed on this forum, that would be nice additions:


Single button selection for WOT BLM lock with the choice of whether to use %TPS or MAF as the trigger and then the ability to enter values for each (within a reasonable range).

Single button selection for Open Loop Idle with a single slider to allow you to richen or lean the idle out.

A revised help section with each table listed, an explanation of each table and its parameters, and an explanation of the general affect of adjusting each parameter (ie greater values = more fuel, lower values mean less fuel at a given rpm, etc.).


Others of you, I'm certain, have much more that you could add to the list. Like I said, these would be "nice to haves". Do you think its asking too much....................Bob???

TG

 

[bruce]

Re: Thanks...........

Originally posted by TurboGeezer
Single button selection for Open Loop Idle with a single slider to allow you to richen or lean the idle out.

If you really get into things, I'd suggest you forget Closed Loop all together. A WB makes it fairly easy, to get the MAF Tables and Scalers correct.

By the time you straighten out the timing tables for a none EGR'd car, you'll want to really dial the fuel in.