RomRaider

hey guys i have my gm bcs and im going nuts. i cant figure out the proper values. my boost will hit target which is 17 than pulsate to about 12 than back to 17 than taper off. i really want to get this to work but i can fiugre it out, i need some help

heres the map im running


i am probably looking over something very minute but i jsut dont see it

thanks for the help everyone

jason

Your integral is too aggressive. Lessen the values. Flatten the map out. That's most of your problem.

Say, look at the stock WGDC, probably around 70-90% to hit target. Now you only are using about 55%. So take about 55/80, close enough to 2/3. Multiply the stock integral map by 2/3 and use that as a starting point. You can probably do the same for proportional, but the integral is more important. Start there. Run that, see how it does for you.

If you still have problems, multiply all but the two outside values in proportional by 2/3. Also, you may want to make proportional mirrored on the plus and minus side. Don't mirror integral though, since it can be unsafe.

If you still have problems, take the stock integral and multiply by 1/2 and use that.

I don't think it is related, but your desired boost map is really ugly. You shouldn't ask for max boost at only 62% throttle You should be back to vacuum by 24% TPS. It needs to ramp from 0 to 100 TPS. It's too flat. But that's not the problem you're seeing in the log with the throttle held right at 100. You may get spiking if you hold part throttle for a second or two (or more) then go WOT with a desired boost map like that, and no messing with the WG stuff is going to help it.

I agree with everything you said, especially focus on the values for overboost (the negative values).

But Freon, why should you be back to vacuum by 24% TPS? I'm not questioning, just curious. Should my current boost map be changed?

with the taret boost map that is the same one from ev8siv3 stage 2 map, why should it be changed around. also do you want me to flatten it out so it only hits 17 psi at 100% throttle thanks a lot man you are helping me out big time

They certainly aren't the same values as in Stage2 04 WRX map by ev8siv (osecuroms.org) that I just downloaded. Yours is very odd. Freon's advice is right on...

your right i made a mistake on the maps on osecuroms theres some guy that made amap for the gmbcs

Cool just swap the right ones in, they don't look like a bad place to start as long as you are comfortable running that much boost.

i think im going to tone it down fromt hat 21 to about 18 i will feel more comfortable there ill keep everyone updated

because it's pointless to close the wastegate in order to produce higher manifold pressure when you're creating such a restriction by holding the throttle plate only 25% open.

I see that, but let's say you're going around a turn and have the throttle 1/4 down. You'd be building boost already, in time for when you're pointed straight. Another example might be passing a car in traffic. 25% throttle until it's all clear, then the boost is already up a bit for when you need to go.

I don't know, that was my thinking. Any thoughts? Should I change this map? ev8siv from OSECUROMS.org seems to have his boost target map set up this way, though certainly his logic isn't bible.

1) you can't control boost AT ALL under wastegate pressure anyway--either to increase it OR decrease it. how much boost do you expect to have "up for a bit?"

2) by closing the wastegate you INCREASE exhaust gas backpressure. yes, the turbo spools up, but where does it attempt to force its output? through a mostly closed throttle butterfly. you are sending mixed messages to the car--do you want more torque, or less? if more, press the gas down. if you want less, open the wastegate and get those exhaust gasses out of the chambers.

the ONLY time i hit full boost is at WOT. i keep the boost at wastegate levels as long as i can, then ramp up quickly to full boost at 100tps.

for best efficiency, you ALWAYS want to have the throttle and the wastegate open as much as possible to net the torque you desire. let the engine breathe--don't choke it off.



don't get me started...

Agreed with ride and freon. I typically run my target boost maps so that wastegate pressure is around the 50% tps mark and then from there ramp up to max target boost at wot.

And yes, the OP is certainly going to need to reduce his turbo dynamics tables and probably the wgdc temp compensation table.

As others said, if you ask for 14 psi when your throttle plate is barely 1/2 or 1/3 open or whatever, you can't hit it. It's just not possible. I'll explain why asking for boost that isn't possible is a bad idea. This goes for any given situation. If, at a steady throttle and RPM you cannot hit the desired boost, it can cause problems.

The stock ECU uses a PID closed loop controller for boost (and other things, but let's look at boost), and one of the potential drawbacks of the system when tuned poorly is called integral windup. This is basically what happens when you ask for too much output given your input states. The controller tries hard to hit the target, because it cannot know that it is unreasonable.

That is, you can't hit 14 psi if the throttle is only 25% open. It just can't physically happen. But, in attempt to hit it, the boost controller will "wind up" the integral to the maximum integral value. Remember, integral is a value that is added up every time the boost controller is run (like 10-20 times per second). So it builds up over time, and gets stuck at the max integral (another set of 1D maps, merch just added this to the 32bit ECU defs) or your total WGDC gets stuck on the Max duty map.

So if you hold the throttle at 25% for a few seconds, the boost controller tries (and fails) to hit your 12-14 psi or whatever. Integral maxes out at +15% or whatever its max it. Then if you punch the throttle, your WG duty is going to ride right along the max value, probably causing overboost briefly.

This might lead you to incorrectly lower your max WG duty at the 80-100% TPS to fix it. This is incorrect, and then just kills your response when at 100% throttle.

Really, you don't want to have to rely on the max duty map to contain overboosts except in some circumstances. Once you are riding the max, the boost controller doesn't have room to make your response the best it can be.

If that's what the XPT map looks like, it is tuned poorly.

I've also found about 50% TPS should be setup to whatever WG spring pressure is. That's about right, give or take. You kinda have to work around WG spring pressure. With a stock 8psi spring, you can have a nice linear desired boost map and make the gas pedal input control linear power. Stiffer springs (like 1 bar) you kinda have to make boost "hump" at 50% throttle, so 0-50% throttle is linear, then from 50-100% it is pretty flat. I.e. 0psiA to 30psiA from 0-50% throttle, then 30psiA to 36-37psiA from 50-100% throttle. This is why I also do not like springs that are too stiff. Very non linear throttle response. I replaced the 1bar spring on my EWG kit with a 0.8bar spring and the car drives way better throughout part throttle.

+1, this is my tuning philosophy as well. People will say that this tuning style leads to an engine that doesn't feel as responsive, I tell those people to either tweak their TPS maps (if electronic throttle) or tweak their right foot.

Ideally, we would not need a wastegate spring at all and could rely on the wastegate solenoid to hold the wastegate shut as required.

I wonder how much lighter of a spring you can get away with when upgrading to the GMBCS?

BTW, ride5000, do you have a screenshot of your boost target/wgdc maps?

I think Merchgod wrote in another thread that the 16bit ECUs don't have the "Integtral" function, where the boost error is accumulated over time.