Open Loop Boost Control Table Fuel Load Instead of Throttle?

[ilovestuffforreal]

I am wondering is there anyway you can use a fuel load (kpa) X rpm table for open loop boost control?
I can't even think of a use for it to be throttle position instead of kpa...
I feel I could achieve a more reliable faster spooling setup easier in open loop if it was based on boost pressure and rpm, instead of throttle and rpm.
Is this possible?

[tutuur]

How are you going to do that? Basing kpa of kpa seems a bit odd to me, totally not reliable at all

[jsmcortina]

If you ignore TPS then you have a less safe system. When TPS is included you can make the wastegate open if you start closing the throttle e.g. if the wheels spin and you start losing control, the wastegate can be opened to help reduce boost and engine torque - at the same time as the throttle itself is closing the intake.

If you _really_ want to reference kPa only, then you can use a "generic PWM" table to achieve that.

James

[ilovestuffforreal]

I see a point now, I just never considered that lowering boost while lowering throttle would be predictable.

I'm looking at it like, I want the waste gates to stay fully closed, all the time, any throttle or rpm, until within 1 or 3 psi of my target, then open.

Instead, I'm chasing down my spool point in rpm, and keep the gates closed until about the rpm I spool up. Just seems ignorant.

But thank you on the tip about using the PWM tables, I may have to try that.

[ilovestuffforreal]

I believe my pressure reference concept is more closely related to external electronic boost controllers. With the set gain, and gain functions. Seems they run from a pressure based table. No tps input.

[jeffmarsh750]

Most electronic boost controllers (the good ones) work on targeting the KPA on the wastegate hat. Meaning you have a seperate sensor on the wastegate and you target a specific air pressure (or boost pressure) on the actual wastegate itself on a seperate map. This would be a cool feature to have, I would use it.

[jsmcortina]

Most electronic boost controllers (the good ones) work on targeting the KPA on the wastegate hat. Meaning you have a seperate sensor on the wastegate and you target a specific air pressure (or boost pressure) on the actual wastegate itself on a seperate map. This would be a cool feature to have, I would use it.

That's recently been added to the thinking pot.

James

[ilovestuffforreal]

Ya, I suppose I should say that I was talking about the greddy profec b in particular. Which boost controller are you talking about in particular? That sounds interesting.

[jsmcortina]

Ya, I suppose I should say that I was talking about the greddy profec b in particular. Which boost controller are you talking about in particular? That sounds interesting.

Many "high end" standalones, especially in drag racing. e.g. AMS1000.

James

[tpsretard2]

You have 3 options.

Learn the e ms boosy control system if you are not very experienced this woukd be your best bet as it works for most people.

Use a generic pwm output as you can set the load side to map.

If you know programing edit the code and change the axis your self.

[sheek]

...or it could be added as an option in the next round of code updates. i too have been requesting this feature in open loop table and i would use it instead of padding an rpm range with 100s

[muythaibxr]

We will not be adding this as an option as it is inferior to what we already have in closed loop . We will be adding dome control however.

[ilovestuffforreal]

I see benefits in both tps and fuel load based control now. I would like to see a boost by rpm table, then a throttle based correction to that table. Could be optionally enabled as some sort of throttle progressive boost control system.

[jsmcortina]

I see benefits in both tps and fuel load based control now.

If you decide to change your boost target, how does that work with your "fuel load based control" ?

James

[Barton]

a while ago I asked james for that (fuel load based boost controller) but I did not realise what it's been told here, and now I see that is not a good idea, but by the time I went to a closed loop control and I simply loved it, is impressive the control applied here.

The only thing I would like to have is a second lower limit DELTA value for the second target table of boost, I mean the first target is for 200kpa and that delta is set to 180kpa, but when you change the target table to 270kpa then the control is not that fast to obtain the 270kpa from a 180kpa delta (this example is a real car I tuned and this is an actual problem). I think the solution there is a second lower limite delta.

[tpsretard2]

I would love to see thisbas an option. However he is right. It is inferior. That said it dos worknthe best for me. It also lends best when running als. Younwant the most boost you program in even at closed throttle.

On a race engine or one driven like it. It might be inferior. Butnitnis preferred.

Going to be away from my computer for a bit butbi could post instructions how to change it for people that want to do it

[ilovestuffforreal]

I see benefits in both tps and fuel load based control now.

If you decide to change your boost target, how does that work with your "fuel load based control" ?
James

Ya, you got me there. I was planning on taking the boost duty percentage that provides the boost level I want from the throttle X rpm graph, and plopping it into the kpa X rpm, generic pwm cell for that same psi as the boost target, and run 0 boost duty until one or three psi before that.
But you are right, changing boost from there would be a tough process. You would have to go back to the throttle X rpm to figure out what the boost duty percentage is for a higher or lower target, then repeating the above process...

The problem is, I'm getting full boost duty cycle anytime I pass half throttle in the car. If I raise the throttle point, I'm scared I'll over boost. This causes me to lose a lot of spooling power, and is rather noisy with open wastegates.

One way of using this system for fast spool up is to 0 the duty cycle up to 80% throttle or so, then, once you hit full boost you must go to 100% throttle else you'll overboost. Also you have to stay below the 80% and less throttle, you'll over boost.
It can only be either a slow spool, traction control system, or good spool, real tricky to drive, no traction control system.

But I do also see how this is a great traction control system, I plan to use it as such for awhile. Maybe in conjunction with a throttle stopping solenoid.
It would be cool to have a throttle based boost target table on the closed loop setup as well.

[ilovestuffforreal]

The Greddy Profec B Spec 2 that I was referring to earlier uses a very popular control method for aftermarket boost controllers. Most of the external controllers, i.e. Turbosmart E boost, Aem Truboost, Apexi and Blitz units, mostly use 3 parameters to control boost. "Wastegate opening pressure," "baseline duty cycle," and "feedback."

There is a good thread that explains each function and has a chart for what each company re names these functions here..
http://www.rx7club.com/2nd-generation-s ... styleid=12

But the solution seems to be the current throttle x rpm open loop boost table, plus the wastegate opening pressure setting. A single psi/kpa number that the waste gate should be fully closed until. And possibly a point to keep the solenoid inactive until. Solenoid off/wastegate spring only until 4ish psi, then keep gates closed until say 1-3 psi before your target.

[jsmcortina]

But the solution seems to be the current throttle x rpm open loop boost table, plus the wastegate opening pressure setting. A single psi/kpa number that the waste gate should be fully closed until. And possibly a point to keep the solenoid inactive until. Solenoid off/wastegate spring only until 4ish psi, then keep gates closed until say 1-3 psi before your target.

We have most of that already.

The current behaviour (in closed loop mode) keeps the solenoid at the "min duty" (off) position until you start making boost.
Then until you are within the "delta" of your target kPa the solenoid is at "max duty" (full boost) position.
Then once you are really close, the closed-loop feedback (slider) is used to maintain the boost.

James

[ilovestuffforreal]

Ya, but none of these functions are present for open loop. I've wasted a lot of time with open loop, I'll be tuning closed loop now...
Thank you for helping me understand.