HOW TO - Control boost using ECUFLash and the stock boost solenoid - Page 3

ShiftySVT · Oct 7, 2006, 07:47 PM

Great write up. This confirms what I was planning on doing eventually.

Could you also set boost by leaving the max duty cycle at 100% and turning down the desired boost? This would seem to be more in-line with the way the designers originally intended to adjust boost since it's based on load instead of simply limiting the duty cycle. I would think that controlling the boost by load would be more consistant when the weather changes.

Evo_Kid · Oct 7, 2006, 08:16 PM

Quote:

Originally Posted by ShiftySVT

Great write up. This confirms what I was planning on doing eventually.

Could you also set boost by leaving the max duty cycle at 100% and turning down the desired boost? This would seem to be more in-line with the way the designers originally intended to adjust boost since it's based on load instead of simply limiting the duty cycle. I would think that controlling the boost by load would be more consistant when the weather changes.

Actully, I tried turning the desired boost load up and down and didnt get any effect. Your right though, the boost system is somewhat based on load and more importantly, the boost error correction is based off load. I'm waiting to get the new EVOScan that logs load, so I can start loggin load and learn alot more about the boost system. I mostly want to figure the error correction out, which is load based.

Evo_Kid · Oct 7, 2006, 08:27 PM

Here is a post I made in another thread somewhat explaining boost control as I see it working.

This is a theory, based on messing with the boost control settings alot.

so....

Load (car is experiancing) - 240 @ 3500rpm

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

WG duty - 90

So with that equation the boost solenoid would run a WG duty of 90, right?

now if this happened..

Load (car is experiancing) - 260 @ 3500rpm

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

Now the load is +8% off

Turbo error correction @ +8% is -5.3 WG duty

So a WG duty of 90, would actully be 84.7, right??

I now know why puttin all 159s in the desired load table make taper go away..

Say you hittin 240 load @ 3500 and 200 load @ 7000.
If all you tables say 159 + the offset, 80, that mean from 3500-7000, you target load is 240.
Now at 3500 you hit that, so the WG duty doesnt change but at 7000 your @ 200, which is 17% under target
Turbo error corr. @ -17% is +8 WG duty.

mchuang · Oct 7, 2006, 09:54 PM

Quote:

Originally Posted by Evo_Kid

Here is a post I made in another thread somewhat explaining boost control as I see it working.

This is a theory, based on messing with the boost control settings alot.

so....

Load (car is experiancing) - 240 @ 3500rpm

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

WG duty - 90

So with that equation the boost solenoid would run a WG duty of 90, right?

now if this happened..

Load (car is experiancing) - 260 @ 3500rpm

Wow Genius. Never really messed with all that math in the boost tables, but that seems like it hits it right on the head.

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

Now the load is +8% off

Turbo error correction @ +8% is -5.3 WG duty

So a WG duty of 90, would actully be 84.7, right??

I now know why puttin all 159s in the desired load table make taper go away..

Say you hittin 240 load @ 3500 and 200 load @ 7000.
If all you tables say 159 + the offset, 80, that mean from 3500-7000, you target load is 240.
Now at 3500 you hit that, so the WG duty doesnt change but at 7000 your @ 200, which is 17% under target
Turbo error corr. @ -17% is +8 WG duty.

dam genius

Dus10 · Oct 7, 2006, 11:31 PM

I pulled the restrictor pill out of the line going from the turbo manifold to the "T" and that bloody thing is smaller than 1.04 mm, so how is it that your homemade restrictor works better than the stock restrictor. This is on a '05 MR ; are the MR's different?

To get smaller than the stock restrictor would be like a pin hole sized hole.

I tired to find some aluminum rod and couldn't find that, so my next mission was to find those ultra small drill bits and I couldn't find those. so I am experimenting with something unusual... my wife makes jewelry and she has some metal beads, well the holes that are drilled thru the beads are pretty damn small and they vary in diameter so I'm going to use one for a restrictor. I'll keep posted on whether they work or not.

Evo_Kid · Oct 8, 2006, 12:01 AM

Quote:

Originally Posted by Dus10

I pulled the restrictor pill out of the line going from the turbo manifold to the "T" and that bloody thing is smaller than 1.04 mm, so how is it that your homemade restrictor works better than the stock restrictor. This is on a '05 MR ; are the MR's different?

To get smaller than the stock restrictor would be like a pin hole sized hole.

I tired to find some aluminum rod and couldn't find that, so my next mission was to find those ultra small drill bits and I couldn't find those. so I am experimenting with something unusual... my wife makes jewelry and she has some metal beads, well the holes that are drilled thru the beads are pretty damn small and they vary in diameter so I'm going to use one for a restrictor. I'll keep posted on whether they work or not.

See how the stock one is tapered and such. Well the rod drilled out is not tapered and therefore its more restrictive.

You can find the aluminum rod and drill bits at ACE hardwear or True Value. I know Home depot sells the rod (its near the hardwear and chain), but they dont sell the small drive bits. Also a "tool" store would have the drill bits.

mchuang · Oct 8, 2006, 12:13 AM

Quote:

Originally Posted by Evo_Kid

See how the stock one is tapered and such. Well the rod drilled out is not tapered and therefore its more restrictive.

You can find the aluminum rod and drill bits at ACE hardwear or True Value. I know Home depot sells the rod (its near the hardwear and chain), but they dont sell the small drive bits. Also a "tool" store would have the drill bits.

Normally a dremel has very small drill bits available and you could use those

ShiftySVT · Oct 8, 2006, 07:58 AM

Quote:

Originally Posted by Evo_Kid

Here is a post I made in another thread somewhat explaining boost control as I see it working.

This is a theory, based on messing with the boost control settings alot.

so....

Load (car is experiancing) - 240 @ 3500rpm

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

WG duty - 90

So with that equation the boost solenoid would run a WG duty of 90, right?

now if this happened..

Load (car is experiancing) - 260 @ 3500rpm

# in desired load table - 159.4 @ 3500rpm
# in load offset - 80 @ 3500rpm
......................... = 239.4 @ 3500rpm

Now the load is +8% off

Turbo error correction @ +8% is -5.3 WG duty

So a WG duty of 90, would actully be 84.7, right??

I now know why puttin all 159s in the desired load table make taper go away..

Say you hittin 240 load @ 3500 and 200 load @ 7000.
If all you tables say 159 + the offset, 80, that mean from 3500-7000, you target load is 240.
Now at 3500 you hit that, so the WG duty doesnt change but at 7000 your @ 200, which is 17% under target
Turbo error corr. @ -17% is +8 WG duty.

I don't follow your calculation. How did you calculate that the duty cycle is 90%? If your target is 159.4 + 80 = 239.4. Then you your boost error correction table would result in 0 correction since 239.4 is so close to 240. Ho did you determine that your duty cycle will be 90% from this? Something is missing.

You're targeting such a high load all the time that you're simply maxing out your wastegate to whatever your max duty cycle is at any paticular RPM. You're basically running open loop boost control. You're not using feedback from the load calculation to control boost. If you dramatically turned down the desired load table and/or the load offset, you would eventually see a reduction in boost. Turning down your max waste-gate below 100% simply clips the amount of control you have.

voidhawk · Oct 8, 2006, 10:26 AM

nice write up - here's a question for you ECU geniuses: is the ECU boost control open-loop or closed-loop? If I understand the function of the "boost error correction" table right, it is actually open-loop? That really suprised me; I would have thought the ECU would somehow get a sensor signal what the actual boost pressure is, and then control the WGA solenoid duty cyle to achieve the desired boost pressure. But from reading you write-up it sounds more like the ECU assumes a steady boost response and then uses to error-correction table to tweak the WGA history which then accounts for the fact that the boost response is not actually smooth after all.

How does the ECU adjust for weather/elevation changes (cold air vs. hot air) this way? The reason I'm asking is that I control boost through the ECU as well, and continue to struggle with large boost spikes on cold weather days.

chrisw · Oct 8, 2006, 10:44 AM

So far I have not been able to reproduce these results, I never got more than 0.8 bar (11.7psi) which leads me to believe I have a leak somewhere in the stock boost lines.

I fixed the problem using an MBC until I can get a complete set of factory hoses with all the stock restrictors in the correct locations. This has been the source my biggest problem so far trying to reproduce these results.

Anyhow, to answer your question voidhawk, the boost control is aways running in closed and open loop. The ECU most likely takes the barometric presure and air temps when calculating the desired boost. I don't know if the parts of the ECU rom that controls the wastegate have been examined in any great detail yet.

In theory, you could adjust the boost load tables to tune out the boost spike, or lower the wastegate duty in those areas where you get the boost spike.

ShiftySVT · Oct 8, 2006, 11:42 AM

Quote:

Originally Posted by voidhawk

nice write up - here's a question for you ECU geniuses: is the ECU boost control open-loop or closed-loop? If I understand the function of the "boost error correction" table right, it is actually open-loop? That really suprised me; I would have thought the ECU would somehow get a sensor signal what the actual boost pressure is, and then control the WGA solenoid duty cyle to achieve the desired boost pressure. But from reading you write-up it sounds more like the ECU assumes a steady boost response and then uses to error-correction table to tweak the WGA history which then accounts for the fact that the boost response is not actually smooth after all.

How does the ECU adjust for weather/elevation changes (cold air vs. hot air) this way? The reason I'm asking is that I control boost through the ECU as well, and continue to struggle with large boost spikes on cold weather days.

Boost pressure is directly related to load. The load is calculated from multiple signals. So it is a closed loop system. Though if you max out desired boost and load offset, you're not running closed loop anymore since you're maxing out the boost control solenoid.

jcsbanks · Oct 8, 2006, 12:38 PM

The error is the difference between present and target load. As I pointed out before, there is no division that occurs, it is a subtraction in the code. So the example of 260 load where 239.4 is the target gives an error of +20.6 and this is the lookup on the error table.

The lookup this error gives appears to be an adjustment to the previous wastegate duty cycle, with limitations to 100% and the maximum duty at that RPM for the WG table in operation at the time. It is therefore a closed loop process which uses an integral correction (because it ramps up or down until the error is zero). The integral gain (the rate at which it ramps up or down) varies depending on the error.

Evo_Kid · Oct 8, 2006, 02:16 PM

First, of all. To everyone questioning my theory. I did say that it was just a THEORY.

What JCS said is probably correct, maybe it subtracts, not divides.

Anyways, I'm still waiting for the new EVOScan with load, so I can figure more of this boost control system out.

Shifty, the 90 WG duty is what the number in the WG duty table @ 3500 would be in that example.

Chris, the same thing happen to me once. I think that I installed something wrong and/or had a leak. I just checked everything, reconnected everything and made sure it was all tight and it fixed the problem.

heyzeus11 · Oct 8, 2006, 06:54 PM

Quote:

Originally Posted by voidhawk

is the ECU boost control open-loop or closed-loop? If I understand the function of the "boost error correction" table right, it is actually open-loop? That really suprised me; I would have thought the ECU would somehow get a sensor signal what the actual boost pressure is, and then control the WGA solenoid duty cyle to achieve the desired boost pressure. But from reading you write-up it sounds more like the ECU assumes a steady boost response and then uses to error-correction table to tweak the WGA history which then accounts for the fact that the boost response is not actually smooth after all.

I would assume that you could say just as long as there are values in the 'error correction' tables the ecu is closed-loop since it adjusts the WG duty based on the engine's load value(s) compared to the 'boost desired lood' values. If the 'error correction' is zeroed out you could say that the ecu is in open-loop since the ecu will not make any adjustments to the WG duty.

Rob W. · Oct 8, 2006, 08:14 PM

Why wait for the new EvoScan when you can just plug the formula into Excel and calculate it now?

I mean, my impression is that the new EvoScan load will still just be a calculated value.. he hasn't figured out how to pull the true value out of the ECU yet. Someone correct me if I'm wrong here.