[supracg]

^Agreed, the solenoid duty cycle might oscillate to hold the wastegate at the desired position, I don't think the wastegates oscillate like that with either tune or stock.

[Ilma]

So if I understand correctly........the duty cycle actually measures the activity of the wastegate solenoids - those two little rectangular switches on the passenger side right above the exhaust manifold, to which the vacuum lines from the two black vacuum cannisters attach to.

Do they regulate the amount of vacuum being stored in the cannisters? or do they deliver the vacuum according to desired boost targets?

[OpenFlash]

Originally Posted by Ilma

So if I understand correctly........the duty cycle actually measures the activity of the wastegate solenoids - those two little rectangular switches on the passenger side right above the exhaust manifold, to which the vacuum lines from the two black vacuum cannisters attach to.

Correct.

Do they regulate the amount of vacuum being stored in the cannisters? or do they deliver the vacuum according to desired boost targets?

The vacuum being stored in the twin vacuum tanks is controlled by the engine. Last I checked, there is usually about 20" of vacuum in those tanks. In other words, there is a consistent ~20" of vacuum upstream of the solenoids. The job of the solenoids is to regulate the level of vacuum downstream. The more vacuum, the more the wastegate actuators are pulled shut.

The basics of boost control are really quite simple once you know the role and functionality of each of the few components in the system. Whether the wastegates are normally closed and actuated by positive pressure (boost) or normally open and actuated by negative pressure (vac), the concepts are essentially the same.

Shiv

[Ilma]

Thank you for clarifying.......I keep learning

[supracg]

Sooo where the logs at?

[adrian@vishnu]

Originally Posted by Ilma

Thank you for clarifying.......I keep learning

I just wanted to add that as far as I know, pretty much all early turbo vehicles (5+ years old) used boost actuated wastegate actuators. Basically a plunger operating against a spring with the plunger directly actuating a rod that moves the wastegate flap. The benefit of this system is that in its simplest form, you can put a turbo onto any car with no electronics and just connect the barb on the turbo compressor outlet directly to the wastegate actuator to get minimum boost (which is set by the spring tension and diaphram size). If you then want more boost, you fit a solenoid or pneaumatic bleed arrangement which effectively just adjusts the proportion of the boost seen by the plunger in order to lift boost.

On a few recent European turbo cars, they have gone to a vacuum canister with vacuum actuated wastegate actuator. One thing I have noticed is that all cars with this arrangement have proportionally small turbos capable of producing boost at relatively light load and low RPM. Where old style turbo could not produce usable boost until high load and high RPM, these small turbos car could. So for the older turbo cars there was no need to control boost except to limit it from going too high. On these newer smaller turbo cars, the turbos are so active at lighter loads, they need to control them under these conditions also to get predictable drivability. This is why I think they moved to this arrangement which has vacuum available at all times so wastegate position can be adjusted at all times. I wonder how long it is before they simply put an electronic servo on to directly control boost? But if it fails it may overboost. Atleast the current setup as pretty much fail safe to produce low boost under common failure modes.

[OpenFlash]

Originally Posted by supracg

Sooo where the logs at?

I had a bunch of logs to post yesterday but Mike suggested that I should go back to the standard resistors for better partial throttle boost control. So I wont post them. I'll probably be installing the resistors tomorrow or day after and re-testing shortly thereafter. I still have to find a way to log jb3 duty cycles with the Procede without inducing a wastegate code. I might have to tap into the signal and feed it into a nonloaded input (perhaps the one used for roadspeed).

Shiv

[OpenFlash]

Originally Posted by adrian@vishnu

I just wanted to add that as far as I know, pretty much all early turbo vehicles (5+ years old) used boost actuated wastegate actuators. Basically a plunger operating against a spring with the plunger directly actuating a rod that moves the wastegate flap. The benefit of this system is that in its simplest form, you can put a turbo onto any car with no electronics and just connect the barb on the turbo compressor outlet directly to the wastegate actuator to get minimum boost (which is set by the spring tension and diaphram size). If you then want more boost, you fit a solenoid or pneaumatic bleed arrangement which effectively just adjusts the proportion of the boost seen by the plunger in order to lift boost.

On a few recent European turbo cars, they have gone to a vacuum canister with vacuum actuated wastegate actuator. One thing I have noticed is that all cars with this arrangement have proportionally small turbos capable of producing boost at relatively light load and low RPM. Where old style turbo could not produce usable boost until high load and high RPM, these small turbos car could. So for the older turbo cars there was no need to control boost except to limit it from going too high. On these newer smaller turbo cars, the turbos are so active at lighter loads, they need to control them under these conditions also to get predictable drivability. This is why I think they moved to this arrangement which has vacuum available at all times so wastegate position can be adjusted at all times. I wonder how long it is before they simply put an electronic servo on to directly control boost? But if it fails it may overboost. Atleast the current setup as pretty much fail safe to produce low boost under common failure modes.

+1
Another reason for the recent changes to vacuum operated, normally open wastegate turbo systems has to do with emissions compliance. Keeping the wastegates open during cold start and cruise keep catalyst temps higher which means better functioning and lower emissions. Big turbos with closed wastegates rob too much exhaust heat since all the exhaust has to travel around the big heavy turbine wheel/housing.

Shiv

[RevC]

subscribed.

[huyner328]

TY for the great explanation on DCs. Rubber band analogy was clutch! The management of these DCs seem to be a essential component in the tunes available. With the WG levers and whatnot, it seems like a component that is prone to wear n' tear much more than any other vital control piece of our turbo system?

[OpenFlash]

Originally Posted by JoeyFiasco

don't all tunes increase the waste gaste DC? if they didn't they would produce the same boost and responsiveness as stock.

Yes on both points.

Originally Posted by huyner328

TY for the great explanation on DCs. Rubber band analogy was clutch! The management of these DCs seem to be a essential component in the tunes available. With the WG levers and whatnot, it seems like a component that is prone to wear n' tear much more than any other vital control piece of our turbo system?

Any mechanical device will wear over time. Wastegates, however, are very simple devices. And for the most part, they are bulletproof. Your much more likely to see failure of a high speed device like the turbo itself since there are more sources of stress (inertial, thrust loads, heat, lubrication, foreign particle damage, etc,.). And even those cases are extremely rare. The wastegate actuators itself are reasonably simple and don't generally see the same increases in operational stress when going stock to tuned as other components. In the case of the n54, there is only a max of 20" of vacuum pulling on them at any given time. And that is usually only for a fraction of a second (during spool up). Once the boost target is reached, pressure is regulated to 10-15" of vacuum.

Shiv

[Jeff@TopGearSolutions]

Good read here for once with minimal drama. Thanks!

[Mike@N54Tuning.com]

Originally Posted by scalbert

More to come but tied up right now.

However, I find it funny now what BMS allows for. Prior to JB3, BMS's stated exhaustive testing of turbo speed suggested a maximum of 14 PSI is what the turbos can tolerate. Once they were able to extend the pulse width, that idea has quietly disappeared. I certainly understand the need to market something and give ones angle. But this isn't the first u-turn.

And am I reading this right. Are you suggesting the solenoid duty cycle causes the wastegates to cycle similarly? If so, the discussions should stop until an understanding occurs. You should know the duty cycle is to get an appropriate amount of vacuum to get the wastgates at the needed angle to generate the desired boost. I apoligize if I read this incorrectly but that is my take on the statement.

I remember reading that the lower boost levels and increased taper of the JB2 was a safer tune than the higher boost levels with less taper that the PROcede V2 offered at the time. And it was. I don't see why you think I'm suggesting otherwise now? Lower duty cycles are safer. As far as this "exhaustive testing" that sounds like an embellishment either from you or BMS' if what you say is true so please post a link.

Duty cycle directly correlates to wastegate position. Higher duty cycle, more vacuum, more closed wastegate. There is some elasticity there but now it sounds like you're suggesting no direct relationship?

Mike

[Mike@N54Tuning.com]

Originally Posted by JoeyFiasco

I fail to see Mike's point then.

If it was my point about duty cycle and under targeting the JB3 has an extra layer of safety that Shiv is bumping up against in his JB3 logs limiting the duty cycle. Which is exactly what a good tune should be doing. So in the logs presented the JB3 duty cycle is likely lower than the V4 duty cycle.

Mike

[Mike@N54Tuning.com]

Originally Posted by shiv@vishnu

Wastegates, however, are very simple devices. And for the most part, they are bulletproof.

Bulletproof? So how do you explain the huge failure and rattle rate? I have had my turbos replaced due to wastegate issues so I don't think I will be calling them bulletproof. You can correct me if I am wrong but I think most turbo replacements are due to wastegate failure/rattle?

Mike

[scalbert]

Originally Posted by Mike@N54Tuning.com

I remember reading that the lower boost levels and increased taper of the JB2 was a safer tune than the higher boost levels with less taper that the PROcede V2 offered at the time. And it was. I don't see why you think I'm suggesting otherwise now? Lower duty cycles are safer. As far as this "exhaustive testing" that sounds like an embellishment either from you or BMS' if what you say is true so please post a link.

Duty cycle directly correlates to wastegate position. Higher duty cycle, more vacuum, more closed wastegate. There is some elasticity there but now it sounds like you're suggesting no direct relationship?

Yes, lower duty cycles and lower boost are better for longevity. That was not the point. BMS did state in the past that anything over about 14 PSI should not be run. This was based on tests they claimed to have done in relation to turbo speed. That said, I always felt this was simply marketing due to the JB2 not being able to run more boost up top. But it is not the topic here.

Yes, duty cycle does correlate to wastegate position. However, it sounded like, from your post, that the duty cycle output causes the wastegates to cycle similarly. In other words, it seemed like you were suggesting that at say, 50% DC, the wastegates are banging back and forth at 50% DC. When, in fact, they are essentially stable in about the middle of their travel range. Again, perhaps I misread...

[scalbert]

Originally Posted by Mike@N54Tuning.com

Bulletproof? So how do you explain the huge failure and rattle rate?

I could be wrong but beleive he was referring to wastegates in general. That it is a simple device of an actuator and flap and it is subjected to less stress that the turbo bearing.

[supracg]

Originally Posted by Mike@N54Tuning.com

If it was my point about duty cycle and under targeting the JB3 has an extra layer of safety that Shiv is bumping up against in his JB3 logs limiting the duty cycle. Which is exactly what a good tune should be doing. So in the logs presented the JB3 duty cycle is likely lower than the V4 duty cycle.

Mike

How can you tell he is bumping up against this layer of safety, because of the undershooting of the target? And is this extra layer the resistor, if so wouldn't that make things worse with a 24 ohm resistor, or are you saying its better to undershoot like that?

[Mike@N54Tuning.com]

Originally Posted by scalbert

Yes, lower duty cycles and lower boost are better for longevity. That was not the point. BMS did state in the past that anything over about 14 PSI should not be run. This was based on tests they claimed to have done in relation to turbo speed. That said, I always felt this was simply marketing due to the JB2 not being able to run more boost up top. But it is not the topic here.

Yes, duty cycle does correlate to wastegate position. However, it sounded like, from your post, that the duty cycle output causes the wastegates to cycle similarly. In other words, it seemed like you were suggesting that at say, 50% DC, the wastegates are banging back and forth at 50% DC. When, in fact, they are essentially stable in about the middle of their travel range. Again, perhaps I misread...

If DC and exhaust flow are stable the wastegate position should be stable too. My point was that changing DC to from 0% to 100% to 30% to 50% would be moving the wastegates more aggressively than changing DC from 0% to 70% to 50%.

Mike

[Mike@N54Tuning.com]

Originally Posted by supracg

How can you tell he is bumping up against this layer of safety, because of the undershooting of the target? And is this extra layer the resistor, if so wouldn't that make things worse with a 24 ohm resistor, or are you saying its better to undershoot like that?

Because the JB3 shows PWM sticking around 100%, meaning the JB3 will not allow duty cycle to be manually increased any higher. This defers the question of additional duty cycle over to the factory ECU which makes the call on ignoring it, increasing it, or giving a 30FF limp code based on many factors.

Hitting the duty cycle limit on map 7 in such a heavily modified car using an 18 ohm board may indicate Shiv's turbos or wastegates are not working as efficiently as they could be. Requiring extra duty cycle to get up to target. I would ask for a JB3 log on map 3 to get a comparison with other map 3 customers running within range.

Mike

[huyner328]

Maybe at those particular RPMs, the JB algorithms don't require that much boost to hit whatever target thus it slowly decreases?

[ianthegreat]

Waiting for the data.