Yes, if you have a "1" adjacent to the -1.4 psi cell, then the ECU will increase the WGDC by 1% change each time the ECU detects that the actual boost is -1.4 psi less than the target boost. The number of times that the ECU checks depends on the value you use for the WGDC Update Interval. If the stock interval of "10" is used, then the ECU checks about once every 0.8 sec. If a value of "1" is used, then the ECU checks about once every 0.08 sec.

If you're still getting less than the desired boost, then add more to the BWGDC table.

 

Are people having good results setting the update interval to 1 ?

I know back in your other thread with load based boost control, it was over-correcting when you went lower than 3.

 

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.

 

This is my experience as well. No reason for people not to try it. I'm sure a concensus on the best settings will develop after a while.

 

Added instructions for 2003 Evo VIII 94170008 ROM.

 

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.

 

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!

 

I'm sorta torn on what to do here. Its easier to understand gauge pressure, but for tuning booost, its better to be thinking in absolute pressure. Its better to think in absolute pressure because absolute pressure is what determines performance. The majority of the people out there will likely be running no more than 24.6 psi of boost. In that case, the easiest way to deal with the boost setting will be to set the Boost Adder to the local atmospheric pressure. The numbers in the baseline boost table then become gauge pressure in your local tuning environment.

 

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.

 

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.

 

Can anyone explain why this is going on?

https://www.evolutionm.net/forums/sh...d.php?t=295764

 

Added instructions for Evo VIII 96420007 and 96420008 ROMs.

 

There are already several suggestions and tips in that thread. Have you tried Mr fred's suggestions?

 

Any hope for 94170015?

 

Atmospheric Pressure Calculator

Might be useful.