Stock Boost Control - Closed loop PWM or just Boost On / Off

[RobBeck]

Bringing back an old thread.

Clint, or anyone... curious to hear your thoughts on this below (see quote too).

After much time tinkering/replacing/changing things on my car (gear swap, DSM intercoolers, AFPR, Supra pump, hotwire, ported headers/turbos/heads/etc)... when I get it running again I will be cleaning/flowing the stock 360cc injectors and running a clipped TD04 based 19T turbo setup.... and I would like to retain the ~8.7psi actuator springs I have installed with the stock boost control setup. Question is whether the increased boost (I am assuming ~3psi across the board due to the springs?) will cause any troubles if I sustain running the car like that? I guess I will know really quick if I get fuel cut eh? Also, do you think the strong actuator spring will yield exactly 3psi across the board? Or does the ECU just adjust it accordingly based on Knock, etc? I sold my logger, so I cant log anymore either to be certain. Also, I am assumimg this something that could be semi-cured by simply upping the fuel pressure... but with Zero corrections I cant take it too far as I have no air fuel tool. I would like to beat on it/durability test, and confirm all is well and stable... before I take the AEM EMS plunge.

Thanks,
Rob

Originally Posted by RobBeck

What is your thoughts on the results of changing the actuator springs... do you think that would cause a boost increase proportional to the new spring minus 6psi?

Rob

[cbatters]

Originally Posted by RobBeck

Bringing back an old thread.

Clint, or anyone... curious to hear your thoughts on this below (see quote too).

After much time tinkering/replacing/changing things on my car (gear swap, DSM intercoolers, AFPR, Supra pump, hotwire, ported headers/turbos/heads/etc)... when I get it running again I will be cleaning/flowing the stock 360cc injectors and running a clipped TD04 based 19T turbo setup.... and I would like to retain the ~8.7psi actuator springs I have installed with the stock boost control setup. Question is whether the increased boost (I am assuming ~3psi across the board due to the springs?) will cause any troubles if I sustain running the car like that? I guess I will know really quick if I get fuel cut eh? Also, do you think the strong actuator spring will yield exactly 3psi across the board? Or does the ECU just adjust it accordingly based on Knock, etc? I sold my logger, so I cant log anymore either to be certain. Also, I am assumimg this something that could be semi-cured by simply upping the fuel pressure... but with Zero corrections I cant take it too far as I have no air fuel tool. I would like to beat on it/durability test, and confirm all is well and stable... before I take the AEM EMS plunge.

Thanks,
Rob

Reasonable chance it will work but I would not take it out of the driveway without a boost gage or loger with a MAP sensor.

Stock boost control is an exotic MBC in a bleeder configuration with the capability of reducing boost to wastegate if it sees excessive air-flow / knock.

Also, there is nothing you can do with FPR that will delay/prevent fuel cut. ECU runs in open loop at WOT and if the air flow goes above limits in the tables the the ECU will initiate fuel cut. (ECU is aso capable of initating fuel/boost cut based on excessive air flow at low RPM indicating a boost problem.)


Clint

[RobBeck]

Oh it definitely will have a boost gauge... haha... shoulda mentioned that I guess.

I realize it wouldnt help with fuel cut... so if I end up with it my only option is to get more injector and make the negative correction to keep the airflow into the ECU beyond that point. I am kinda hoping it pushes the stock setup as far as possible... putting me right below the Fuel cut threshold.

As for upping the fuel pressure, that is just a bit of "safety" margin for the added 30-50hp I could get for the extra ~3psi of boost that I "think" I will see.

Basically I am thinking using the upgraded actuator springs MAYBE a cheap YET safe way to up boost yet retain all OE functionality (tune, injectors, air meter, boost dropoff, etc).

Rob

Originally Posted by cbatters

Reasonable chance it will work but I would not take it out of the driveway without a boost gage or loger with a MAP sensor.

Stock boost control is an exotic MBC in a bleeder configuration with the capability of reducing boost to wastegate if it sees excessive air-flow / knock.

Also, there is nothing you can do with FPR that will delay/prevent fuel cut. ECU runs in open loop at WOT and if the air flow goes above limits in the tables the the ECU will initiate fuel cut. (ECU is aso capable of initating fuel/boost cut based on excessive air flow at low RPM indicating a boost problem.)


Clint

[cbatters]

Originally Posted by RobBeck

Oh it definitely will have a boost gauge... haha... shoulda mentioned that I guess.

I realize it wouldnt help with fuel cut... so if I end up with it my only option is to get more injector and make the negative correction to keep the airflow into the ECU beyond that point. I am kinda hoping it pushes the stock setup as far as possible... putting me right below the Fuel cut threshold.

As for upping the fuel pressure, that is just a bit of "safety" margin for the added 30-50hp I could get for the extra ~3psi of boost that I "think" I will see.

Basically I am thinking using the upgraded actuator springs MAYBE a cheap YET safe way to up boost yet retain all OE functionality (tune, injectors, air meter, boost dropoff, etc).

Rob

AFR will give you some control over AF at WOT but you may end up playing a funnny game of catchup with the ECU. ( ECU lower trims based on higher fuel pressure and thus lowers INJD at WOT effectviely short circuiting any "tuning" you do with FPR.)

Not much difference between MBC and upgraded springs - in both cases you end up flirting with fuel cut and limits of stock injectors.

No point in upgrading injectors unless you stick in an air/fuel controller. (or a calibrated air bypass line on the stock MAS - check out Mellons MAS Limits thread)


Clint

[cbatters]

Thread on air bypass on stock MAS. Allowing Mellon to run 720 injectors with almost no AF correction. (he made the mod to reduce the airflow restrictiopn of the stock MAS but also found that it was much more linear that he expected.)

what is the limitation of the stock MAS?

With a little more investigation, it should be possible to use 550 injectors and the right size bypass and eliminate the need for an air controller.

I'll ping Mellon and see if we can get him to post some pics.



Clint

[RobBeck]

So you are thinking the formulas of HP vs. pressure rise would not apply here without the tuning to support the increased pressure? I was thinking an extra 15 or so psi base would be enough fuel to support about 50 more crank HP... if the ECU would make use of it that is.

The only difference I can think of the stock boost control vs. mbc is that the ECU still has control, and can adjust boost downward if needed. The actuator spring upgrade was something I had already done, and now that my car is going AEM EMS I really dont want to install the stock 6psi actuators to only have to remove them later. I really only want to get it running with stock electronics to make sure everything checks out before progressing with the AEM EMS.

Rob

Originally Posted by cbatters

AFR will give you some control over AF at WOT but you may end up playing a funnny game of catchup with the ECU. ( ECU lower trims based on higher fuel pressure and thus lowers INJD at WOT effectviely short circuiting any "tuning" you do with FPR.)

Not much difference between MBC and upgraded springs - in both cases you end up flirting with fuel cut and limits of stock injectors.

No point in upgrading injectors unless you stick in an air/fuel controller. (or a calibrated air bypass line on the stock MAS - check out Mellons MAS Limits thread)


Clint

[RobBeck]

Oh and I was not wanting to take the injector swap on till I am ready to go EMS. I am not really interested in jumping into another project... just want to get it running nice and clean with the OE fueling... to make sure all is well for the AEM. But what complicates it is the 9psi actuator springs and the other "free flowing" mods I will have. Just wanted to check on thoughts of upping fuel pressure to make up for the extra boost, or inquire on how well the stock fueled/boost controlled car could support the setup with the higher boost via actuator springs. From what I recall, my STOCK setup would spike to about 15-16psi, then quickly taper to about 11-12psi, and then gradually drop to about 7psi at redline UNDER stock boost control. That was with 9bs so some of that drop could be due to them being outflowed complicating what should have really happened if the mechanical limits of the turbo hadnt been basically exceeded. I am assuming that I MAY see up to 18-19psi SPIKE with the upgraded springs (which MAY likely cause me instant FUEL CUT), and then a quick taper back to about 14-15psi, then a gradual drop to about 12-13psi by redline since I will be running upgraded turbos.

Rob

[cbatters]

Originally Posted by RobBeck

So you are thinking the formulas of HP vs. pressure rise would not apply here without the tuning to support the increased pressure? I was thinking an extra 15 or so psi base would be enough fuel to support about 50 more crank HP... if the ECU would make use of it that is.

The only difference I can think of the stock boost control vs. mbc is that the ECU still has control, and can adjust boost downward if needed. The actuator spring upgrade was something I had already done, and now that my car is going AEM EMS I really dont want to install the stock 6psi actuators to only have to remove them later. I really only want to get it running with stock electronics to make sure everything checks out before progressing with the AEM EMS.

Rob

What I said was that there was no point in installing bigger injectors without modifying the air signal going to the ECU. (either passively or with an air-fuel controller)

Increasing base pressure whas absolutelky nothing to do with staving off fuel cut.

Stock ECU will calculate reasonable injection with stock injectors for higher than stock boost pressure right up to the point where it initiates fuel cut.



Clint

[phobos]

Clint, any updates on this?