Target boost, I can't get to you!!

Car has the following mods:

catless uppipe

hiflow invidia downpipe

bullet proof kit on intercooler

stage 2 tuned

My usual peak target boost is around 17.8 psi under high load. The ECU usually reports 1.8-2 psi boost error (actual boost of 15.8 psi or so). If I push the car in 5th, I may reduce the boost error by 1 psi. But who wants to go in high boost in 5th .

Temps outside are cold. So I should easily reach or pass the target boost. My 06 has a very similar setup (+ ebcs and avo wastegate actuator) and she reaches EXACTLY target boost almost always. Amazing.

-- I have checked pre turbo exhaust leaks. Found some and took care of them.

-- My long term fuel trims look good (within +/- 5% across)

-- last time I pulled the downpipe (1 month ago), did not find any cracks at the wastegate. Wastegate looked fine too.

So I don't know what else to check . Thoughts??

Wastegate not closing? Or something rattling that seems to be detected as knock?

How about the blow-off valve on the intercooler?

Do you use the MAP value when looking at the boost or do you have a separate gauge?

Otherwise I'd start to worry about either the valves not sealing or an issue with AVCS or valve lift. When was last time you checked valve clearance?

And no turbo hoses that are bad so you get a silent boost leak?

Time for a pro tune and EBCS.

Are you running the same boost target on the '06?

Do you use the MAP value when looking at the boost or do you have a separate gauge?

 

Otherwise I'd start to worry about either the valves not sealing or an issue with AVCS or valve lift. When was last time you checked valve clearance?

 

And no turbo hoses that are bad so you get a silent boost leak?

I use the MAP value reported by the ECU. I also view the AVCS angles live when I drive. They are always in sync.

I also monitor misfire and stuff. I have none.

Finally, I've personally readjusted my valve clearances 15k miles ago. All good there.

Time for a pro tune and EBCS.

 

Are you running the same boost target on the '06?

I've been thinking of using an EBCS on this car too. But the stock one should be fine for these boost levels no?

The 06 has slightly higher peak boost target (~19.2 psi). This car consistently reaches its target boost values.

Is this something new, or has it always done this (and maybe you just haven't noticed it)? Could be tune-related (e.g. wastegate duty compensations).

It is not something new unfortunately. Been suffering since I went stage 2 and retuned the car. Can't exactly say if it happened right after the tune though as I was not paying attention at the target boost around that time.

But you may be right. It might be tune related.. so I guess is it possible to tell the ecu that the target boost is X, and yet the tune is able to avoid reaching X by adjusting the wategate duty cycle or something?

It really just sounds like the wastegate values aren't high enough or there is too much compensation values (less likely).

Stock turbo?

It really just sounds like the wastegate values aren't high enough or there is too much compensation values (less likely).

 

 

Stock turbo?

Yes. still stock turbo. Should I upgrade

I use the MAP value reported by the ECU. I also view the AVCS angles live when I drive. They are always in sync.

I also monitor misfire and stuff. I have none.

Finally, I've personally readjusted my valve clearances 15k miles ago. All good there.

Good, I'm just paranoid.

And no flow issues with the air filter either then? Just because a filter is new doesn't mean it's good, sometimes there are manufacturing issues.

^I've been viewing the wastegate duty cycle for a while now. I just recall it peaks around 69% I think and it easily becomes non-zero with/without boost. But I have not logged it while boosting. I will try that today.

FWIW, I recall the wastegate DC on my 06 (which has an ebcs) peaks at 20% or so.

^I've been viewing the wastegate duty cycle for a while now. I just recall it peaks around 69% I think and it easily becomes non-zero with/without boost. But I have not logged it while boosting. I will try that today.

FWIW, I recall the wastegate DC on my 06 (which has an ebcs) peaks at 20% or so.

Yeah, the aftermarket EBCS will require significantly less wastegate DC than the stock BCS to hit the same targets.

Yeah, the aftermarket EBCS will require significantly less wastegate DC than the stock BCS to hit the same targets.

Is the tuning for an EBCS vs stock basically a linear or straight multiplication of factory tune table?

^Do you have an aftermarket ebcs and which turbo do you have?

I have a GrimmSpeed EBCS and I'm running a JmP VF46 custom with a catted Cobb DP, SPT catback, stock airbox, Perrin turbo inlet, and a GrimmSpeed TMIC. My tune originally targeted around 19psi (typically would peak around 20ish), but I've since lowered it a little to around 18-19psi peak.

Is the tuning for an EBCS vs stock basically a linear or straight multiplication of factory tune table?

Haven't played with boost control on my own (I'm running a Stg2 tune from Mike @ Tuning Alliance with some small tweaks of my own), so I'm not sure. I wouldn't expect it to be linear or simple scaling necessarily, but I can't imagine it's far off. That said, the safe and thorough way to tune it is to start at low duties (zeroed out if you've made so many changes you're not sure what'll happen ), then monitor boost error under various conditions and tweak until it's all about right. With that in mind, I personally wouldn't start with just scaling the factory table, just to be safe. But I'm not an experienced tuner like some of the vendors here

I just received a map from Mike as well, haven't been able to install it yet.

Did you receive and open source and that's how you were able to edit yours?

So, regarding the WG DC it sounds like this variable essentially reports how hard the boost controller works, and not necessarily how much the wastegate is open right?

My tune is also from Mike. It's at least two years old now. But I recall I asked him to provide a mild tune. I may have to get in touch with him to revise this tune.

Also, let me ask this again:

so I guess is it possible to tell the ecu that the target boost is X, and yet the tune is able to avoid reaching X by adjusting the wategate duty cycle or something?

 

Also, let me ask this again:

 

so I guess is it possible to tell the ecu that the target boost is X, and yet the tune is able to avoid reaching X by adjusting the wategate duty cycle or something?

 

Yes. The lower the wastegate duty cycle, the lower the boost (unless there is something mechanical causing excessive boost spikes). If the table is zeroed out, you'll always be at wastegate pressure only.

mmmh. I see.

Last night, I kept a close eye on the DC values and it was climbing as I was pushing the car and then stayed somewhat steady at around 64%, and still did not reach target boost.

So I guess next question is: for those of you who owns a stock turbo with stock boost controller and are stage 2 like me, what DC values do you see under load (e.g. third gear close to WOT) and while trying to reach target boost?

I just received a map from Mike as well, haven't been able to install it yet.

Did you receive and open source and that's how you were able to edit yours?

He actually tuned me with an AP, but I eventually sold it and ported the tune over to OS. I asked him for it to be unlocked with the understanding I wouldn't share it (for obvious reasons).

So, regarding the WG DC it sounds like this variable essentially reports how hard the boost controller works, and not necessarily how much the wastegate is open right?

 

My tune is also from Mike. It's at least two years old now. But I recall I asked him to provide a mild tune. I may have to get in touch with him to revise this tune.

 

Also, let me ask this again:

Yeah, the WGDC sets how much the EBCS closes the wastegate. So a 0% duty cycle means the wastegate will operate at spring pressure (stock is around 7psi). 100% duty cycle means the EBCS will keep the wastegate closed indefinitely.

As for the boost, there are compensations on boost target. Those are what change (along with the min/max wastegate duties). If you are getting boost error, then the car isn't hitting its target. However, say your primary boost table says 17psi but the car's only hitting 15psi, but reports zero boost error, then the reason is that the compensations have modified the boost target and the car is operating correctly. In other words, if you have boost error, likely your problem lies in wastegate or, more rarely, turbo dynamics (assuming it's a tune problem). If the boost error is zero but your actual MRP values don't match your primary boost table, compensations are taking effect.

Also, it's worth mentioning, it's definitely beneficial to tune the target boost table to minimize error (even outside of boost) as it can have effects on fueling and timing which can cause strange behavior in closed-loop operation.

mmmh. I see.

 

Last night, I kept a close eye on the DC values and it was climbing as I was pushing the car and then stayed somewhat steady at around 64%, and still did not reach target boost.

 

So I guess next question is: for those of you who owns a stock turbo with stock boost controller and are stage 2 like me, what DC values do you see under load (e.g. third gear close to WOT) and while trying to reach target boost?

If it's hitting a steady WGDC and the boost isn't at target, sounds like you'll need to increase your max WGDC tables accordingly. For reference, on my stg2 tune (roughly 19psi peak target), my max WGDCs are in the 50-60% range with an EBCS and the JmP VF46. For the stock EBCS, I'd expect needing more WGDC to reach the same sorts of numbers.

One more thing I thought of is the "restrictor pill".

Some more reading here: https://www.cobbtuning.com/support/how-subarus-factory-boost-control-system-works-v1-09/

 

As for the boost, there are compensations on boost target. Those are what change (along with the min/max wastegate duties). If you are getting boost error, then the car isn't hitting its target. However, say your primary boost table says 17psi but the car's only hitting 15psi, but reports zero boost error, then the reason is that the compensations have modified the boost target and the car is operating correctly. In other words, if you have boost error, likely your problem lies in wastegate or, more rarely, turbo dynamics (assuming it's a tune problem). If the boost error is zero but your actual MRP values don't match your primary boost table, compensations are taking effect.

Interesting. Thanks for the explanation. I should then mention that I've been viewing/logging the 'boost target' and the actual boost variables pulled from btssm, and figured out in my head the 'boost error'. But I never actually viewed the 'boost error' variable pulled by btssm. So I think I will do that next and see if the boost error is actually zero even if I am not reaching the boost target value.

One more thing I thought of is the "restrictor pill".

 

Some more reading here: https://www.cobbtuning.com/support/how-subarus-factory-boost-control-system-works-v1-09/

I thought about that too but I think this should be 'played' with much down the road.

Interesting. Thanks for the explanation. I should then mention that I've been viewing/logging the 'boost target' and the actual boost variables pulled from btssm, and figured out in my head the 'boost error'. But I never actually viewed the 'boost error' variable pulled by btssm. So I think I will do that next and see if the boost error is actually zero even if I am not reaching the boost target value.

 

 

 

I thought about that too but I think this should be 'played' with much down the road.

I think that should be the same then. I believe the boost target parameter is the final boost target (after all compensations are applied).

huh. So when you say 'primary boost table', that is not the same as the boost target parameter then correct?

note: I have on my old pc the latest rom and the openecuflash (whatever name it is called) to view the current tables and stuff. I've never really spent the time to look at it. I think I will do this now as I have a bit of time..