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- Feb 18, 2006
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- 10,084
Does the car have a big front mount?
This may be a good candidate for blow thru.
This may be a good candidate for blow thru.
Stalling Issue - Any Calibration Ideas?
- Thread starter mgmshar
- Start date
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As I mentioned above, I have a "big front mount" (CAS V2), so I'm sure all that volume is part of the issue. Basically, my combo is about as conducive to spooling (and subsequent flutter) as one could get. TA-49, loose exhaust, big front mount, loose converter, and check-valve boost control. The data I sent to Bob included 70 "idle, open throttle, close throttle" runs. Even if I just opened the throttle "a little bit" (say 1.0 volts TPS) for a short time (say one or two seconds), enough turbo speed would build that I would see long periods of backflow and flutter during the deceleration. That would cause the engine to stall in many cases.
A blow-through MAF or TPro (get rid of the MAF) might be a next step for me. For now, I am fairly sure that the existing "anti-stall" features in the chip can prevent the stalling. The threshold for "anti-stall" activation just needs to be lowered significantly for my car.
Once Bob and I get our email straightened out and I get some information from him, I will continue working on this. I am hoping that I can get this done this weekend, since I'll actually have time to work on it.
A blow-through MAF or TPro (get rid of the MAF) might be a next step for me. For now, I am fairly sure that the existing "anti-stall" features in the chip can prevent the stalling. The threshold for "anti-stall" activation just needs to be lowered significantly for my car.
Once Bob and I get our email straightened out and I get some information from him, I will continue working on this. I am hoping that I can get this done this weekend, since I'll actually have time to work on it.
- Joined
- Feb 18, 2006
- Messages
- 10,084
No doubt Bob will iron it out.
Sounds like you are in tune with things.
Good luck! :biggrin:
Sounds like you are in tune with things.
Good luck! :biggrin:
Just to close the loop on this...
No tough problem can be solved without data. So, I performed the following experiment:
1. I ran the car until it was fully warm and the BLM's settled out (i.e. the ECU had fully "learned" the car).
2. I would bring the car to a full stop, selector in "OD", and wait until the IAC and idle speed settled down to their target values. I would then activate the DirectScan record function.
3. I then quickly stepped on the accelerator, held it open for a certain amount of time, and then quickly released the accelerator. For each run, I varied the amount that I opened the throttle and the length of time I opened the throttle. The lengths of time I used varied from about 0.5 to 4 seconds.
4. After releasing the throttle, I would wait to see the car's response and stop the DS record. One of four things would happen:
a. The engine would stall during the coast-down due to the high backflow and flutter through the MAF sensor.
b. The engine would "nearly stall" during the coast-down, same as above except the flutter would stop and the ECU would recover before the engine stalled.
c. The engine would settle down to idle with no problems.
d. The engine would settle down to idle after activating the "anti-stall" feature in the chip.
I repeated steps 2 through 4 a total of 70 times (no kidding). By looking at the DS data from each run, I could get a clear picture of what was happening.
Bob was kind enough to let me know that LV8 and TPS thresholds are used to "arm" the anti-stall feature in the chip. So, I looked at how the car responded to the various LV8 and TPS values that were present at the instant before I released the throttle during my test runs. The attached graph summarizes what I saw.
To fix the problem, I just lowered the LV8 and TPS thresholds that "arm" the anti-stall software to values below the worst-case on the graph (the red point that is farthest down and to the left on the graph). By doing that, the anti-stall feature activates at much lower LV8 and TPS threshold values than before. Bob's anti-stall routine (which is quite clever) works very well - just needed to activate it at much lower thresholds on my car.
Hope this helps somebody. Thanks to Bob again for his help on this.
Regards,
No tough problem can be solved without data. So, I performed the following experiment:
1. I ran the car until it was fully warm and the BLM's settled out (i.e. the ECU had fully "learned" the car).
2. I would bring the car to a full stop, selector in "OD", and wait until the IAC and idle speed settled down to their target values. I would then activate the DirectScan record function.
3. I then quickly stepped on the accelerator, held it open for a certain amount of time, and then quickly released the accelerator. For each run, I varied the amount that I opened the throttle and the length of time I opened the throttle. The lengths of time I used varied from about 0.5 to 4 seconds.
4. After releasing the throttle, I would wait to see the car's response and stop the DS record. One of four things would happen:
a. The engine would stall during the coast-down due to the high backflow and flutter through the MAF sensor.
b. The engine would "nearly stall" during the coast-down, same as above except the flutter would stop and the ECU would recover before the engine stalled.
c. The engine would settle down to idle with no problems.
d. The engine would settle down to idle after activating the "anti-stall" feature in the chip.
I repeated steps 2 through 4 a total of 70 times (no kidding). By looking at the DS data from each run, I could get a clear picture of what was happening.
Bob was kind enough to let me know that LV8 and TPS thresholds are used to "arm" the anti-stall feature in the chip. So, I looked at how the car responded to the various LV8 and TPS values that were present at the instant before I released the throttle during my test runs. The attached graph summarizes what I saw.
To fix the problem, I just lowered the LV8 and TPS thresholds that "arm" the anti-stall software to values below the worst-case on the graph (the red point that is farthest down and to the left on the graph). By doing that, the anti-stall feature activates at much lower LV8 and TPS threshold values than before. Bob's anti-stall routine (which is quite clever) works very well - just needed to activate it at much lower thresholds on my car.
Hope this helps somebody. Thanks to Bob again for his help on this.
Regards,
Attachments
When my A/C is off, these changes are still working very well. I can stab the throttle for any amount/duration I want, and the car always settles back down without stalling. The combination of limits for anti-stall trigger and IAC follower values that I have in there now work very well with the A/C off.
However, a couple of weeks ago, I got my A/C running again. I noticed that if I give the throttle a short stab (say while backing out of my driveway) with the A/C on, the car will stall. What is strange is that the car will stall even though I believe it is going into "anti-stall mode". I'm not 100% sure, because I only had an old OTC scanner hooked up at the time - one data frame every 1.5 seconds doesn't show a lot. I haven't had time to really look at it with my DS yet. I'm guessing that I'm going to need to mess with the IAC follower values a little more to keep it from stalling when the A/C is engaged. Once I get some time to look at this, I will post back.
I did purchase a MafTPro from one of the other members of this board. I'm hoping to get it installed before the summer is over. It came with a chip set-up for 50-lbers (I think) - I might be contacting you to get a chip set-up for my 57-lbers. I'm guessing that once I go MafTPro, I will probably not have to worry about this kind of stuff any more.
Please let me know if you have any other questions. Always glad to help when I can.
not sure on the AC, if you get some data we can work on it. The antistall routine uses a default MAF flow which may be too low if the AC is on.
The Translator Pro makes all this stuff go away. Get that thing installed. Did you get the plug-and-play adapter?
Bob
The Translator Pro makes all this stuff go away. Get that thing installed. Did you get the plug-and-play adapter?
Bob
TurboBob said:
I got the MAFTPRO with the boost control solenoid and all of the plug and play harnesses. The only difficult thing I will have to do is relocate the MAT sensor. Just a matter of finding time - just got the car back from being painted a few weeks ago, many items on the to-do list.
If I get some time to play with the AC stalling problem, I'll pass on my results and data.
Mike
Sent from my HTC Droid Incredible using Turbo Buick
Hi Bob,
I finally got around to running some DirectScan files of the stalling event with the A/C on. In summary:
A/C off: I stab the throttle then release it, chip goes into anti-stall mode, O2 sensor shows rich (over 800 mV) as the engine speed comes down, goes back into closed loop after turbo stops fluttering. Everything is good.
A/C on: I stab the throttle then release it, chip goes into anti-stall mode, O2 sensor shows rich at first AND THEN GOES LEAN AS ENGINE RPM'S DROP BELOW 1000 (less than 100 mV), engine speed keeps going down and stalls.
Best guess is that your default MAF value at speeds below 10000 RPM during anti-stall mode are too low for the case when the A/C compressor is running.
I sent you a PM. If you want to look at the DS files, let me know your email address.
Thanks,
I finally got around to running some DirectScan files of the stalling event with the A/C on. In summary:
A/C off: I stab the throttle then release it, chip goes into anti-stall mode, O2 sensor shows rich (over 800 mV) as the engine speed comes down, goes back into closed loop after turbo stops fluttering. Everything is good.
A/C on: I stab the throttle then release it, chip goes into anti-stall mode, O2 sensor shows rich at first AND THEN GOES LEAN AS ENGINE RPM'S DROP BELOW 1000 (less than 100 mV), engine speed keeps going down and stalls.
Best guess is that your default MAF value at speeds below 10000 RPM during anti-stall mode are too low for the case when the A/C compressor is running.
I sent you a PM. If you want to look at the DS files, let me know your email address.
Thanks,
Do you have your Translator Pro setup yet? If so, what are your MAF Limit settings? there are 5 of them.
1. MAF Limit TPS threshold --- Below this TPS, the Airflow will be limited.
2. MAF Limit --- Limit of Speed Density airflow when TPS is below setting.
3. MAF Limit/ KRPM --- Airflow per 1000 RPM limit. If set to 10, the airflow will be limited to 10 at 1000 RPM, 20 at 2000 RPM, etc.
4. MAF Limit RPM Min --- If RPM falls below this, Limiting is turned off to prevent droops and stalls.
5. MAF Limit time --- Max number of seconds the limiter will stay active.
1. MAF Limit TPS threshold --- Below this TPS, the Airflow will be limited.
2. MAF Limit --- Limit of Speed Density airflow when TPS is below setting.
3. MAF Limit/ KRPM --- Airflow per 1000 RPM limit. If set to 10, the airflow will be limited to 10 at 1000 RPM, 20 at 2000 RPM, etc.
4. MAF Limit RPM Min --- If RPM falls below this, Limiting is turned off to prevent droops and stalls.
5. MAF Limit time --- Max number of seconds the limiter will stay active.
