Load target changed?
Feb 6, 2008 | 09:51 AM
#16
No, i don't really have any hard proof that it will hold more boost up top with the spring ... it is just based on the basic mechanics of the WG and the assumption that the taper is caused by the exhaust gases overcoming the WG spring tension at high RPM.
I can tell you this though ... I was previously running about 19 to 19.5 psi and a max of ~1850 hz airflow above 7000 RPM before the spring mod ... this was at 100% WGDC. With the spring I'm holding 19.5 to 20 psi and breaking 1900 hz airflow at the ~88% WGDC you see in the graph posted. This is even with the odd load target issue I'm having currently and warmer weather.
Also, when tuning a customer's car with an MPFab WG dump, you can hear the WG dump loudly all the way to redline ... this is another indication that exhaust is passing by the flapper.
Last edited by TouringBubble; Feb 6, 2008 at 09:56 AM.
Feb 6, 2008 | 09:59 AM
#17
Your run with the error correction timing at 1 seemed to produce your desired behavior though, didn't it? I don't know why 1 millisecond is making such a big difference. You don't want to run it at 1 and adjust your error correction values to work with 1?
Feb 6, 2008 | 10:09 AM
#18
In order for the flat BWGDC idea to work correctly, the -20 to -15 area of the TBEC table must have a positive correction value in place. This is to prevent a no correction occurence if actual load falls below desired (which could be more common with a flat BWGDC and seasonal change).
I switched from a correction delay of 1 to 2 to lower the spike created by this correction in the -20 to -15 area. Battling those spikes are the biggest challenge to running a flat BWGDC profile.
I believe I tried a map last night that had correction delay at 1 and it didn't help the issue. I can double check.
I switched from a correction delay of 1 to 2 to lower the spike created by this correction in the -20 to -15 area. Battling those spikes are the biggest challenge to running a flat BWGDC profile.
I believe I tried a map last night that had correction delay at 1 and it didn't help the issue. I can double check.
Feb 6, 2008 | 10:26 AM
#19
Take the spring off since that is the only thing (if I am reading correctly) that you changed from last time.
See if that helps. Also flash a normal rom without tephra mods if taking the spring off didn't help.
The spring might be making the arm bind.
See if that helps. Also flash a normal rom without tephra mods if taking the spring off didn't help.
The spring might be making the arm bind.
Feb 6, 2008 | 10:31 AM
#20
Here is what has been done since the car was last logged and WGDC functioned as expected ...
Sunday, Jan 27:
Airbox removed
DV removed
battery removed
Clutch line replaced
Brake lines replaced
oil changed
transmission fluid changed
TC fluid changed
diff fluid changed
brake fluid changed
Brakes bled
clutch partially bled
Ran out of brake fluid so ...
Saturday, Feb 2:
Clutch bled
brakes bled
Sunday, Feb 3:
Battery reinstalled
DV reinstalled
airbox reinstalled
coolant added
new wheels/tires installed (245/45/17)
Tuesday, Feb 5:
valet limit engaged
valet limit disengaged
tires balanced
WG spring installed
flashed
The issue was found in the first log after this point ...
Last edited by TouringBubble; Feb 6, 2008 at 10:38 AM.
Feb 6, 2008 | 10:32 AM
#21
The reason I think culprit is something with the TBEC settings is because your other graph with the TBEC values changed and timing changed produced your desired behavior. Also when you change something that controls boost then changes in WGDC produce different results, like changing to a 3-port requires different WGDC numbers. With the 3-port incremental changes in WGDC produce different boost levels with respect to stock solenoid.
You changed something that affects boost control and that probably requires different TBEC settings in a nutshell.
You changed something that affects boost control and that probably requires different TBEC settings in a nutshell.
Feb 6, 2008 | 10:36 AM
#22
Yeah, I'm going to try that if nothing with the ECU seems to help. It just doesn't make sense though ... if the spring was the issue, the boost solenoid and WGDC would still be doing more to try to correct for the low load level. It seems clear to me that the ECU isn't even attempting to hit the desired load.
Feb 6, 2008 | 10:46 AM
#23
Before removing the spring I'm going to log some more tonight ... I'll run a tuned BWGDC curve with no correction and see how it goes. It should work as expected since target load doesn't matter if there is no TBEC.
When I've got that close to my target, I'll enable a basic TBEC map and see if it pulls down the load. I believe it will.
The only thing is that I still feel that the ECU is applying something similar to the min temp for boost control value and is simply reducing the target load on its own.
When I've got that close to my target, I'll enable a basic TBEC map and see if it pulls down the load. I believe it will.
The only thing is that I still feel that the ECU is applying something similar to the min temp for boost control value and is simply reducing the target load on its own.
Feb 6, 2008 | 11:02 AM
#25
I topped off the coolant. it was not a full change. I basically filled up the reservoir since it was nearly dry for some reason. My min temp for full boost control value is 76 I believe. The car was completely warm when i logged.
I'm not sure what you are asking about the boost control reading differently ... ?
I'm not sure what you are asking about the boost control reading differently ... ?
Feb 6, 2008 | 11:05 AM
#26
Evolved Member
Joined: Jan 2006
Posts: 953
Likes: 2
From: Oxfordshire
In the most basic sense, if the WG flapper could hold closed (if it were welded for instance), the turbo would spin and spin and hold boost until it basically ripped itself apart or melted. There might be a little taper up top, but the turbo is technically capable of holding much more than 19 or 20 psi at redline. Whether it can do it efficiently is not being considered in this example of course.
At high RPM, can the turbo flow enough air to maintain your desired pressure, given others experience, then 20 psi maybe getting close to the limit, but a couple more PSI is not out side the realms of possibility, dependent on your cars mods. I've not seen an evaluation of the compressor map on a IX so it would be trikky to say exactly
The second factor is, can your boost control system bleed enough air to stop the actuator operating, are you using the stock BCS or a 3 port?
Thirdly do you suspect exhaust pressure against the wastegate flapper is causing it to open? Unlikely as the boost hold at a higher level at lower revs.
Interesting problem though.
MB
Feb 6, 2008 | 11:23 AM
#28
Since you are using WGDC's below that I don't think that is an issue.
It also has a max WGDC it will allow depending on coolant temp.
50c = 0% WGDC
60c = 50% WGDC
70c to 82c = 100% WGDC
Feb 6, 2008 | 11:50 AM
#29
I see the angle you are coming from. My question had a number of thoughts.
At high RPM, can the turbo flow enough air to maintain your desired pressure, given others experience, then 20 psi maybe getting close to the limit, but a couple more PSI is not out side the realms of possibility, dependent on your cars mods. I've not seen an evaluation of the compressor map on a IX so it would be trikky to say exactly
The second factor is, can your boost control system bleed enough air to stop the actuator operating, are you using the stock BCS or a 3 port?
Thirdly do you suspect exhaust pressure against the wastegate flapper is causing it to open? Unlikely as the boost hold at a higher level at lower revs.
Interesting problem though.
MB
At high RPM, can the turbo flow enough air to maintain your desired pressure, given others experience, then 20 psi maybe getting close to the limit, but a couple more PSI is not out side the realms of possibility, dependent on your cars mods. I've not seen an evaluation of the compressor map on a IX so it would be trikky to say exactly
The second factor is, can your boost control system bleed enough air to stop the actuator operating, are you using the stock BCS or a 3 port?
Thirdly do you suspect exhaust pressure against the wastegate flapper is causing it to open? Unlikely as the boost hold at a higher level at lower revs.
Interesting problem though.
MB
Yes, I suspect exhaust pressure is pushing the WG flapper open at high RPM. you are correct, bost will hold higher at low RPM, but the turbo is also flowing a lot less at low RPM. think along the lines of flow rather than boost. Less flow can build more boost at low RPM because there is more time to pressurize the intake system.
Look at your logged airflow curve ... it constantly rises even though your boost is fairly constant (or even dropping). It then peaks and levels off or even falls bit. That occurs because the engine RPM rises but the turbo isn't flowing any more than it did the previous rotation.
It's honestly hard for me to explain because i don't know the correct terms that have to do with engine VE. Basically, the faster the engine turns, the faster the turbo has to turn to keep boost up ... that means more overall airflow as engine RPM increases even if boost stays the same. The absolute limit of the turbine RPM/flow can be determined by a couple of things ... mainly drag or friction from intake air/exhaust backpressure/shaft bearing, or more commonly exhaust being bypassed through the wastegate.
I only want to hold about 21 psi after 7000 as logged by my JDM MAP. My max boost >7000 withouth the spring was around 19.5 psi.
EDIT :: to elaborate ... here is something I posted in the O2 dump thread a while back ...
I think you are both saying the same thing in different ways ...
In the most basic sense, a wastegate works like this:
- The WG opens to lower or hold a given boost level when the VE of the engine is high/increasing
- The WG closes to increase or hold a given boost level when the VE of the engine is low/decreasing
- The WG flap reacts to pressure changes via a manifold pressure source and a spring with a given resistance. So, when the engine VE drops and pressure begins to decrease the WG also begins to close, which in turn increases the pressure.
The dump is louder at higher engine VE since the WG flows more to regulate boost at those times. This is technically independent from the actual pressure at the manifold. Regulating 20psi @ 4000 RPM is much different than regulating 20 psi at 7000 RPM due to the compressor efficiency.
On the stock Evo turbo, the WG does operate at 100% duty (fully closed) at high (and very low) RPM.
However, from the sound produced by the atmospheric "dumpatron" and logs I've recorded, it seems that even at 100% duty at high RPM the WG flap is not entirely closed. The sound indicates that the WG is still dumping exhaust and the logs indicate a slight increase in airflow in high RPM/WGDC areas resulting from decreased backpressure.
It's may assumption that the pressure created by the exhaust flow at high RPM is enough to overcome the wastegate spring at high RPM. This is exactly why you can decrease boost taper at high RPM with an upgraded WG actuator and the stock WG. The increased spring tension does a better job holding the WG closed at higher RPM.
The external dump on the wastegate reduces the back pressure resulting from the turbulence created when this bypass flow through the WG mixes with the turbine flow in the stock/standard design O2 housing. This results in increased turbine flow capability across the entire RPM range and therefore less boost taper up top.
In the most basic sense, a wastegate works like this:
- The WG opens to lower or hold a given boost level when the VE of the engine is high/increasing
- The WG closes to increase or hold a given boost level when the VE of the engine is low/decreasing
- The WG flap reacts to pressure changes via a manifold pressure source and a spring with a given resistance. So, when the engine VE drops and pressure begins to decrease the WG also begins to close, which in turn increases the pressure.
The dump is louder at higher engine VE since the WG flows more to regulate boost at those times. This is technically independent from the actual pressure at the manifold. Regulating 20psi @ 4000 RPM is much different than regulating 20 psi at 7000 RPM due to the compressor efficiency.
On the stock Evo turbo, the WG does operate at 100% duty (fully closed) at high (and very low) RPM.
However, from the sound produced by the atmospheric "dumpatron" and logs I've recorded, it seems that even at 100% duty at high RPM the WG flap is not entirely closed. The sound indicates that the WG is still dumping exhaust and the logs indicate a slight increase in airflow in high RPM/WGDC areas resulting from decreased backpressure.
It's may assumption that the pressure created by the exhaust flow at high RPM is enough to overcome the wastegate spring at high RPM. This is exactly why you can decrease boost taper at high RPM with an upgraded WG actuator and the stock WG. The increased spring tension does a better job holding the WG closed at higher RPM.
The external dump on the wastegate reduces the back pressure resulting from the turbulence created when this bypass flow through the WG mixes with the turbine flow in the stock/standard design O2 housing. This results in increased turbine flow capability across the entire RPM range and therefore less boost taper up top.
Last edited by TouringBubble; Feb 6, 2008 at 12:12 PM.
Feb 6, 2008 | 11:53 AM
#30
The factory value for "min temp" before boost control or CEL, is 63% WGDC (remember factory uses 100% WGDC)
Since you are using WGDC's below that I don't think that is an issue.
It also has a max WGDC it will allow depending on coolant temp.
50c = 0% WGDC
60c = 50% WGDC
70c to 82c = 100% WGDC
Since you are using WGDC's below that I don't think that is an issue.
It also has a max WGDC it will allow depending on coolant temp.
50c = 0% WGDC
60c = 50% WGDC
70c to 82c = 100% WGDC
Yes, I have changed my load reference for boost to match the 2-byte value.