nevermind didn't search sorry....

 

The stock boost system, with stock restrictor pills, can't boost higher than ~21psi.

If you take out the pill at the solenoid side, you can spike to ~23psi, but it won't stay that high.

You'll have to put in a smaller, more restrictive pill on the turbo side in order to exceed 23 psi, and to hold 23 lbs.

Read up on the thread for "How to control boost using the stock solenoid"

Raising the "boost limit" table only adjusts for fuel cut, this won't make any changes to your boost profile.

Since the stock MWGDC table is already 100 throughout, you're maxed out on the stock pills, and no ECU changes will raise this.

 

If your a newb to tuning you shouldn't try to tune your car to run 24psi right away. You should figure out how the system works and then shoot for a conservative boost setting like 21psi. In addition the most important tables that need to be adjusted for higher boost are your FUEL and TIMING tables because you need to have the correct air to fuel ratio and proper timing in order to run any additional boost.

Also the stock BCS is mechanically limited by the boost orfices located in the hose between the compressor housing and the T and the other orfice that is located in the line to the boost solenoid.

The tables in the Turbo section pertain to the boost control system. The Evo ECU doesnt really know what "boost" is, it's values are all load values. Load and boost are relative to each other to a certain degree but they are not the exact same thing as load takes into account a lot more than just the level of boost you are running. As your reading threads that pertain to the stock Boost Control System you will see alot of abreviations.. They refer to these tables.

BOOST DELAY TIMER (this is in miliseconds, and refers to how long BOOST LIMIT can be exceeded before fuel cut is imposed OEM value is 1000, it's good)

BOOST CONTROL LOAD OFFSET - BCLO (This value combined with Boost Desired Engine Load which is RPM dependant determines the TARGET load value)

TURBO BOOST ERROR CORRECTION - TBEC (This table is the table the ECU accesses to determine how much wastegate duty to add or remove in order to achieve the target load. The negative table values tell the ECU how much duty to add and the positive values tell the ECU how much duty to remove)

BOOST DESIRED ENGINE LOAD 1-3 - BDEL (This value combined with the load offset determines TARGET load, max value is 159.4)

MAX WASTEGATE DUTY 1-3 - MWGDC (Wastegate % values, 100% is closed (more boost), 0% is fully open (no boost)

BOOST LIMIT - BL (If this value is exceeded for longer than Boost Delay Timer value then you will get fuel cut, this is a safety feature to protect your engine from overboost failure, load values of 240-250 (depending on mods) are around 21psi, 260-275 are common boost limits that people set).

 

so all things staying the same except for boost limit what happens if I make all 255 in the table. Will this eliminate bost taper and hold the 21.7 or whatever the stock IX lbs is?

 

Boost Limit = Fuel Cut

If your ECU exceeds the values in the boost limit table, it cuts fuel because it is afraid you are severely overboosting. If you raise these values, you are simply raising the threshold before fuel cut.

There is no way to increase boost in the system without physically changing the setup of restrictor pills that are in your lines.

Please read the above to posts and search for how the stock system works!

 

Also, Mr. Evo IX, wouldn't 100% WGDC be fully OPEN and not closed? I think of it as percentage bleed, because if it bleeds boost into the intake, then the WGA doesn't get hit with as much, thus = more boost.

So 100% = fully open = fully bleeding = less boost to WGA = more boost to engine

 

so by raising the boost limit table to all 255 it does nothing? I swear that I didn't feel the boost taper like I did before I made this change.If it doesn't eliminate taper then why does stock boost limit setting go lower as rpm goes up? Seems to relate to the taper..

 

Trust me. Read Mr. Evo IX's post and going forward, please don't make ECU changes unless you are sure of what they do.

We'll be glad to help you with your tune, but try to research some more before you experiment!

 

Read most of the 3+ page post on raising boost and it gave tired head just like most of the 3+ page posts. I'm not saying they are not important just tiring. From what Mr. Evo IX's said something like 240-250 is 21psi so what I was asking was how the ecu made the taper and the boost limit table points to this like he said if you don't excede that certain value fuel cut won't happen. So the stock boost limit table has 255 then goes down gradually and makes the boost taper. I know what fuel cut is from my dsm days and trust me I'm not making too radical changes that I don't feel confident about. Thanks for your help.

 

No, your confusing solenoid operation and wastegate operation. The more pressure your wastegate sees the more it will open and allow pressure to escape which means less boost. The more air your solenoid bleeds the more boost you will get before your wastegate opens. But yea, were saying the same thing.. more duty - more boost. Less duty - less boost.

Your asking how to increase your target load. Remember target load is the sum of Boost Desired Engine Load + Boost Offset. So.. for example, lets say you have BDEL set at 159.4 down the entire rpm range and your Boost Offset is 80, then your Target Load will be 239.4. Your ECU will try to achive that load using the Wastegate settings that you have in place (OEM 100%) and it will access the Boost Error Correction if it needs to add Duty or Remove Duty to maintain that target. Since BWGDC is already 100% it can't add to it but it can remove duty to protect against overboost. Hope this helps you put all the pieces together. Remember.. the pills are going to impose a physical limit right now which is a good thing and will keep you from blowing anything up. But you can remove some of the taper by changing the settings with the pills (orficies) in place.

When you use a different orfice or use a GM 3port you can set your Wastegate duty to a lower value and achive higher boost so then the correction table can work both ways.

 

The Boost Limit table is just overboost protection, it does not control how the solenoid or wastegate operates at all. If the Boost Limit value is exceeded for longer than the Boost Delay Timer allows then fuel is cut to protect your engine.

The taper is caused by 2 things. The first thing is that the OEM BDEL table decreases as rpm increases so the target load value is reduced and the ECU operates the wastegate solenoid according to the Turbo Boost Error Correction table to maintain the target load value (which is the sum of BDEL and OFFSET). Also the IX turbo will taper due to turbo design limitations.

 

So if wanted to maintain the 21.7psi to redline what settings on which tables would you suggest?

 

Look at Boost Desired Engine Load #2 table.

From 500rpm to 3500rpm the value is 159.4 and the stock Load Offset is 80. So when your Evo is spooling up it's load target is 239.4. The ECU reads realtime load - Let's imagine the real load is 225 and RPM is 3500, so it's 15 load units below target. Now the ECU subtracts real load from target load and comes up with a value (-15), it then looks at the error table to find out what to do about it, -15 says Add 8 to wastegate duty so that's what the ECU does except in this case WGDC is already 100% so it can't do anything except keep bleeding pressure to keep the WG from opening. Then it checks again. This time when it checks we are at 4000 rpms and the real load reading is 245, Whooops, it overshot the target, which has also reduced to 235 because BDEL is lower at 4000rpm, so now it finds out how far it overshot the target by subtracting target load from real load and cross references that again with the error table. This time it's 10 load units over target and the correction table tells the ECU to operate the wastegate at 6.5% less duty cycle so it operates the wastegate at 93.5% duty cycle and allows some pressure to be released from the wastegate which in turn will reduce boost presure which will reduce load. The ECU keeps doing this always trying it's best to be on target.

So how can we tell the ECU we want more boost? We can change the target load by increasing BDEL and by changing the load offset. Also, if we want to have steady boost we can adjust wastegate duty manually using the duty cycle map so that the ECU doesnt have to be as re-active.. for example.. we know that at 3500rpm we are going to have a boost spike so why not just reduce the wastegate duty in the table so that the ECU wont have to make corrections later. Also, we can control how much correction the ECU makes if it's over correcting by increasing or reducing the values in the correction map.

 

Increase Boost Desired Engine Load #2 table to 159.4 at all RPMs. Now your ECU will try to maintain a load value of 239.4 accross the entire RPM range but remember.. the system is physically limited by the pills or orfices. If you take the upper pill out the solenoid will not be as limited, and it can release more pressure with it's solenoid allowing you to run higher boost but it needs to be controlled since it will be capable of over shooting it's load targets even more at that point (my car is capable of over 25psi with just the solenoid pill removed, it can't hold this boost but it can spike that high). This is when you probably dont want 100% at 3500rpm as it's likely to achieve load of 260+ with the solenoid pill removed. So you can compensate for the boost spike by changing the duty cycle at 3500 rpm. And since the stock solenoid is not all that responsive you might start lowering it at 3000 rpm or even 2750rpm.

Also, please refer back to my original post, since were modifying the amount of air were forcing into the engine we now have to adjust fuel and timing accordingly for the load cells were operating in because we've changed the combustion enviroment by adding more boost.

my MWGDC table looks like this and my boost still tapers after 6500. Honestly I think some of it may be that the solenoid de-activates at a certain rpm and stops releasing pressure but I can't change Wastegate de-activation in my flash because there's no value to change.. just (...) like when you dont have a correct definition file for a value in ECU Flash but I dont know how to fix that.

500 100
1000 100
1500 100
2000 100
2250 100
2500 100
2750 99.0
3000 97.5
3500 97.5
4000 98.0
4500 98.0
5000 98.5
5500 99.0
6000 99.5
6500 99.5
7000 100