View Full Version : Drop throttle response tuning?
Does the new 5.22 have drop throttle response tuning? I've been using 5.11 and have not seen it. I have hunting problems when letting off the gas. The car jerks a couple time and then stops.
01-22-2010, 07:04 AM
Yes it's still there. The parameters are the 5 MAF LIMIT settings.
They are for maf value limiting in SD to prevent drop throttle problems.
Don't know if it will help you any but here's are typical values like what I use in my 3.8 Buick.
MAF Limit TPS Threshold---- 0.50
MAF Limit------------------ 6.00
MAF Limit / KRPM----------- 2.50
MAF Limit RPM Min---------- 1248
MAF Limit Time------------- 2.0
Awesome. I have seen these settings before but completely overlooked it. My problem seems to be from a lean condition at throttle drop. To help a little, I used the User Tune Low to add 50% when the drop goes below 27 kpa (letting off the gas completely). Changed the default Low load to 27 from 35. During deceleration, I would think the ecu would cut off the injectors right? Maybe it needs a smooth transition from part throttle to deceleration and a sudden change in fuel would jerk the car.
I'll give these MAF Limit settings a try tonight.
01-22-2010, 03:28 PM
the tune settings are interpolated (blended) between the load points, its not a threshold.
if you want it to switch like that set the mid threshold to 30.
But it might make more sense to look into the overall tune.
What kind of car? Do you have any log files?
I have a nissan sr20det engine. 4 cylinder, direct ignition, turbocharged. I gave the MAF Limits a try. I used TurboDave settings as an example. Thanks TurboDave.
I guess I had never touched these settings, so they were zero as default. After changing out a few settings. Thar car doesn't jerk as much. Feels good.
MAF Limit TPS Threshold---- 0.32 (closed is at 0.28)
MAF Limit------------------ 4 (it is 3 g/s at idle)
MAF Limit / KRPM----------- 0 (I left this at zero, will try 2.5 later)
MAF Limit RPM Min---------- 1248
MAF Limit Time------------- 1.5
Does the MAF Limit / KRPM setting make a big difference?
Also, I am using speed density mode with a custom user loaded maf output table. The table emulates a 300zx 500hp maf instead of the factory unit.
I was reading this page:
Wonder why it says "This setting is not used in speed density applications." under the MAF Limit settings.
01-23-2010, 07:28 AM
Not sure why it says that. Here's what the XDF item description says in Tuner Pro RT for MAF Limit:
Limit of Speed Density airflow when TPS is below setting
01-23-2010, 08:05 PM
the MAF limiter was primarily used in translator mode in the early days. In translator mode you tune it a bit differently, to prevent engine stalls from rich surging when dropping the throttle from WOT.
The comment is left over from those days.
Since then the limiter has been refined to help with SD applications where the tune is too rich on close throttle decel and you don't want to fiddle with the VE table to tune it out or your MAP sensor won't go low enough.
Ah I see. Well the MAF Limits really helped me out. Thanks TurboDave and TurboBob.
Looks like my remedy was to make it richer unlike others who want to make it leaner. I trimmed my user maf table near the low airflow range which helped with idling. Idling is near perfect and now drop throttle is fixed as well.
01-25-2010, 10:07 PM
01-26-2010, 07:06 AM
Glad to hear your tune is coming together.
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