how-to: ECU-based direct boost control
#91
I want to ask what it means to add 1's in the cells adjacent to -1.4, -2.0 and -3.1 psi. The right column is referring to WGDC change. What is the 1 changing? Is it a percentage? Is it adding 1% to the WGDC?
I ask because I am still getting less than desired boost even though I add to my WGDC.
I ask because I am still getting less than desired boost even though I add to my WGDC.
If you're still getting less than the desired boost, then add more to the BWGDC table.
#93
Evolved Member
iTrader: (2)
MY thoughts on the faster update interval ...
It is completely possible to get a nice, flat curve with an interval of "1" or "2." Doing so will give you very quick boost response.
The trade off is that the correction values must be very small ... I've had corrections of ".5" throw my boost in to a wobble. This is because the boost has not caught up to the correction so the correction stacks on the next interval ... that ".5" becomes "1.5" or so before the boost can catch up and overcorrection occurs.
A longer update interval has alleviated this issue for me. The difference between Mrfred's and my findings is that he bleeds off from the boost source and I use a custom pill.
It is completely possible to get a nice, flat curve with an interval of "1" or "2." Doing so will give you very quick boost response.
The trade off is that the correction values must be very small ... I've had corrections of ".5" throw my boost in to a wobble. This is because the boost has not caught up to the correction so the correction stacks on the next interval ... that ".5" becomes "1.5" or so before the boost can catch up and overcorrection occurs.
A longer update interval has alleviated this issue for me. The difference between Mrfred's and my findings is that he bleeds off from the boost source and I use a custom pill.
#96
Evolving Member
iTrader: (1)
Join Date: Aug 2005
Location: Chandler, AZ
Posts: 318
Likes: 0
Received 0 Likes
on
0 Posts
Great work mrfred. I think somebody (smarter than me ) should write a "how to tune ecu-based boost control" and put it in the lead threads. Basically letting people know what functions are dependent on what and what changes to make to alleviate certain conditions. I think this would take the fear out of some people's eyes and make this mod more prevalent. In a way similar to the fuel trim analysis and tuning using latency and scaling in one of the other threads.
#97
Newbie
iTrader: (5)
Join Date: Jul 2007
Location: Charlotte
Posts: 58
Likes: 0
Received 0 Likes
on
0 Posts
Is it possible to change the "psia" units to "psig" in your baseline boost tables or would you need to change scaling to accompany this change due to the boost adder table (I am assuming is local atmospheric press) being in absolute pressure? Is it as simple as a text change from "psia8" to "psig8" in the scaling because the boost adder "psia16" is independent of "psia8"?
Hope that made any sense whatsoever. I only say this because that is how my mind works. When I look at your baseline boost table and see 23.8psia, I think 23.8psia-14.5psia(atmospheric)=9.3psig which is lower than what you really mean.
Excellent work on this! Its great to have a system like this rather than load based because this setup takes into account differences in pre-compressed air density due to ambient air temp differences and results in the same desired boost regardless of ambient temp. Seems much more safe. Thanks Mr. Fed!
Hope that made any sense whatsoever. I only say this because that is how my mind works. When I look at your baseline boost table and see 23.8psia, I think 23.8psia-14.5psia(atmospheric)=9.3psig which is lower than what you really mean.
Excellent work on this! Its great to have a system like this rather than load based because this setup takes into account differences in pre-compressed air density due to ambient air temp differences and results in the same desired boost regardless of ambient temp. Seems much more safe. Thanks Mr. Fed!
#98
Is it possible to change the "psia" units to "psig" in your baseline boost tables or would you need to change scaling to accompany this change due to the boost adder table (I am assuming is local atmospheric press) being in absolute pressure? Is it as simple as a text change from "psia8" to "psig8" in the scaling because the boost adder "psia16" is independent of "psia8"?
Hope that made any sense whatsoever. I only say this because that is how my mind works. When I look at your baseline boost table and see 23.8psia, I think 23.8psia-14.5psia(atmospheric)=9.3psig which is lower than what you really mean.
Excellent work on this! Its great to have a system like this rather than load based because this setup takes into account differences in pre-compressed air density due to ambient air temp differences and results in the same desired boost regardless of ambient temp. Seems much more safe. Thanks Mr. Fed!
Hope that made any sense whatsoever. I only say this because that is how my mind works. When I look at your baseline boost table and see 23.8psia, I think 23.8psia-14.5psia(atmospheric)=9.3psig which is lower than what you really mean.
Excellent work on this! Its great to have a system like this rather than load based because this setup takes into account differences in pre-compressed air density due to ambient air temp differences and results in the same desired boost regardless of ambient temp. Seems much more safe. Thanks Mr. Fed!
#99
Newbie
iTrader: (5)
Join Date: Jul 2007
Location: Charlotte
Posts: 58
Likes: 0
Received 0 Likes
on
0 Posts
Would it be better to reference the baro sensor for a dynamic "boost adder" instead of a static input of atmospheric pressure to account for weather changes in pressure and elevation?
I noticed in one of my logs that the baro reading was about 100-101 kPa at idle and dropped a tiny bit at cruise and dropped more so during hard accel down to about 96-97kPa. Is the baro sensor within the MAF body in the air flow path? I was wondering about this to account for the drop in baro press during accel, when velocity increases within the MAF, the pressure will decrease.
I noticed in one of my logs that the baro reading was about 100-101 kPa at idle and dropped a tiny bit at cruise and dropped more so during hard accel down to about 96-97kPa. Is the baro sensor within the MAF body in the air flow path? I was wondering about this to account for the drop in baro press during accel, when velocity increases within the MAF, the pressure will decrease.
#100
Yep, the baro sensor is in the MAF and is definitely affected by airflow through the MAF.
Even if there were a baro sensor separate from the MAF, it wouldn't make sense to use it because engine performance is determined by absolute manifold pressure instead of gauge pressure.
If the boost control keys off of gauge pressure, then nasty things can happen. Take the example of someone living at 5000 ft who sets up a gauge pressure EBC to peak at 23 psi. The absolute pressure is 23 psig + 12.2 psi = 35.2 psia. If the guy now drives the car at sealevel, the gauge pressure will still be the same, but the absolute pressure will now be 23 psi + 14.7 psi = 37.7 psia. The car will not be boosting 2.5 psi higher than it should be. Hope that makes sense.
Even if there were a baro sensor separate from the MAF, it wouldn't make sense to use it because engine performance is determined by absolute manifold pressure instead of gauge pressure.
If the boost control keys off of gauge pressure, then nasty things can happen. Take the example of someone living at 5000 ft who sets up a gauge pressure EBC to peak at 23 psi. The absolute pressure is 23 psig + 12.2 psi = 35.2 psia. If the guy now drives the car at sealevel, the gauge pressure will still be the same, but the absolute pressure will now be 23 psi + 14.7 psi = 37.7 psia. The car will not be boosting 2.5 psi higher than it should be. Hope that makes sense.