damian

iTrader: (2)

I just want clarity on this, correct me if I'm wrong:

increasing the duty on the PRI will increase boost (or at least the pri spike)...so what this means is that the PC actuator is seeing less pressure (solenoid is bleeding more with the higher duty cycle) adn thus diverting less exhast to the secondary, also thus incresing the primary boost...

conversly, by turning the PRI duty down you will get less boost (or less spike) by the PC actuator to seeing more pressure, thus venting more exhaust to the secondary...

In effect you can indirectly control how much the the secondary gets pre-spooled by the primary duty cycle setting, correct?


the duty on the SEC setting just control the boost/spike level when the secondary comes online, correct?


ok, example time: if you see 11 psi on primary and 10 psi on secondary, yet the boost settings in teh PFC are 10 psi for both (both also set to 64% duty cycle), then you could decrease the pri duty so it goes down to 10, however in doing so you will also add prespool to the secondary, correct? thus wanting to decrease the duty just a bit on the SEC to stop any spiking at transition


(dont take the numbers as literal, i am using some real and some example numbers, I just need to know if my understanding is sound)

damian

iTrader: (2)

wow, not one reply :-(

GoodfellaFD3S

iTrader: (213)

Well, I'm running parallel now, but when I was running seq I always understood the actually boost numbers (ie 0.85) to be a target value and the duty cycle of the solenoid to be the means to reach that target. I don't think they have much to do with spiking at transition, although I could be mistaken. I use my profec B to control boost, and the little sucker has a balance **** with mild/sharp settings. I just incrementally moved the **** towards mild until I was seeing a minimal spike.

TwinTriangles

I get what your saying but I dont have an answer, Im curious about this too now!
Thanks allot man...!

damian

iTrader: (2)

:-)

yeah, its an interesting relationship, the pc and wg, boost level vs boost spike, et, et...

reza

anyone has answer now?

spyfish007

Ok, I think I've explained this 100 times ... but maybe never on the forum. The initial duty cycle number does matter in relation to speed at which the target boost is aquired. A bigger number will exactly as described above, but it will tend to spike; ie overshoot. A lower number is more stable but boost reponse is slower.

Control systems have fundamental characteristics regardless of mechanical or electrical. The dampening factor is one of those performance characteristics. Fast=overshoot and slow=underdamped. Remember Days of Thunder? "Now Cole, lose is fast and on the edge of out of control." Well boost control is no different. The question now is how much overshoot can you live with? If you hit the nail on the head your boost will be critically damped meaning the fastest response without overshoot. Happy trails.

reza

Yes, I have seen in my searches that you explain that.
Now I will try to explain what is happening on mine. I also post this in an old thread in the 3rd gen forum.

Somehow PFC prespool less than stock ECU.
My setting now are:
Pri .80 90%
Sec .80 70%
With boost pattern: 13.5 - 5 - 10

I played with the setting a bit, then I got: 14 - 5 - 10
Pri .80 40%
Sec .80 70%

With PFC stock setting of pri .80 56% and sec .70 64%, I got: 14 - 5 - 8

Boost always goes above the target. And setting of the primary duty cycle seem to have little effect. The primary boost always goes to about 13-14psi.
And with higher duty cycle, it seems to give lower boost. This is reverse of what the manual said.

spyfish007

I would be curious if your precontrol is even setup correctly. I've seen many of stock twins where the primary will only make 14 psi boost period. My point being if you have no control you might get 14 psi. Have you tried lowering the boost pressure target value and seeing if stable boost is possible. Go to 10 psi and see what you get.

It does seem like your wastegate control is working. Although 10 psi does not equal .8 kg/cm2 of boost.

reza

How do I check if the precontrol setup correct?
I revert back from Home Depot valves to the stock vaccum line with restrictor in it.
Ah...one more thing. On my stock ECU with the HD valves on precontrol and wastegate, I am able to get 10-8-10 properly. I had ported wastegate, thus I had to close the wastegate valve more to make the secondary boost to 10, otherwise it stays about 8psi with stock ECU. That is the reason I have HD valves with stock ECU.
Now with PFC, I don't want to have so many variables, HD valves, boost target, and duty cycles. So eliminate the HD valves.

spyfish007

It is one of the last things I said in my last post. "Go to 10 psi and see what you get." So lower your target boost to .7 and your duty cycle to like 56% and see what you get. Just keep going lower till you find a point that PFC is controlling boost. If that doesn't work, then you'll need to check the mechanical side of everything-plumbing of vacuum lines, restrictors, and precontrol door position.

reza

Okay, my concern is the primary and the transition(prespool of secondary).

Primary went too high, thus not much prespool, thus dip in transition.
What is controlling the primary? Prespool right? Is the primary duty cycle in PFC the duty cycle of prespool?
Why is it when I set 40% duty and 90% duty, it does not make much difference, and actually lower boost with 90% duty.

However, I will try lowering it to .70 and 56% on primary, and see what happen. My concern is the .70 + .25 fuel cut limit = .95 And I am reaching more than .95 at this point.

spyfish007

If you have the target boost and the duty too far this could cause a problem .... very low % probability here, but none the less.

I gave you numbers that should be approximately related for your setup. If the boost keeps going up then get out of it. I've hit fuel cut before. It is not the end of the world.

All of your questions and answers are correct about primary/precontrol boost. I almost wonder if there is a leak somewhere in your system keeping the door shut unless the precontrol door is WAY out of adjustment.
I have a thought in my head to test the precontrol door, but try the lower boost test first.

jpandes

Try lowering the duty cycle to 38%

My car is Non-Seq

The reason why I say this is that I used to get a boost spike to 14 psi and then the boost would settle down to 12 PSI(where I wanted it) when I had the duty cycle set to 60-70%. But after reading a post suggesting to lower the WG duty cycles to 38%, my boost no longer spikes. It just hits the set boost level which is now 14psi and stays there.

reza

which WG duty cycles? I am running sequential. So WG is the secondary duty cycle.

jpandes

reza

well its not gonna help me with the primary boost goes up to 14psi...

spyfish007

Just do the test as we talked about eariler.

reza

You are right on the money!!!
Since you said this, I have been wondering if the precontrol not working right. I suspect a loosely fit hose on the precontrol pill.
While working to get there, I checked the precontrol solenoid, and right in my face the vacuum line apparently has pop off the hard line that goes to precontrol actuator.
Hopefully that fix my 14psi problem.
I put the PFC setting to normal 56%, and see how it goes later.

Now I know the primary goes to 14psi uncontrolled.

Thank you spyfish!!!

jpandes

Another satisfied rx7forum customer...

spyfish007

Glad to hear it worked out for you. Be sure to let me know what you think of the 56% setting too. One thing I've noticed more and more during the spring/fall periods of the year. Boost control will vary based on the temps outside. The car just makes so much more boost when it is cold that it is more difficult to keep it down on the settings I use for warm weather. Just keep that in mind when tuning. Happy trails!

reza

Okay, I did some runs to get the boost right. All test done on 2nd gear, not 3rd gear.
I went by watching the boost gauge and the peak hold value of Commander.

I started with following value
.80 56%
.80 64%
Boost goes to about 10psi primary, 5psi dip, then 9psi secondary.
Boost peak hold is .81

In the end I have
.80 70%
.80 76%
Boost goes to about 12psi primary, 5psi dip, then 12psi secondary.
Boost peak hold is .86

And for the final run, I did a datalogit chart. And I don't quite like the boost pattern there. You can see that I am not getting the 12psi right away. I thought I hit 12psi around 2700rpm based on watching the boost gauge. Not according to datalogit.

The goal is for autocross, so I want boost right now, not when I am about to reach the next corner.
When my precontrol line not working(see previous post), I feel like I got instant boost up to 14psi. Now I kinda miss it. Any thoughts?

spyfish007

Where did you get your base tuning from?

I checked your web page and it looks like you have some/new exhaust pieces, so that rules out clogged cat. Also you've got good boost numbers, so I don't suspect leaky pipes/clamps/etc. You must realized that you will never have the boost response of a controlled system like you have with the boost line off. However you can get it better and my initial thought of the moment is fuel/spark tuning. The PowerFC is usually tuned very conservative at the transistion and if depending on what maps you have will also influnce this factor. The basic idea is pull timing and add fuel to reduce the power and hence possibility of a boost spike that will kill your motor. You might have some tuning with the boost as well. However if you are not seeing much change here you might look elsewhere. A slow turbo control actuator will make this problem bad. However usually the TCA isn't bad it is the TCA pressure solenoid that is mounted on the air control valve that gets old. If you have an extra around it might be worth testing it out.

reza

Not tuning at all...I am using base 5-08 PFC maps. I figure since I still have stock intake and intercooler, not much flows thru the system.
I still have to use wideband to make sure of that though.
That is why I just want to run 12psi at max, but I want it across the board. You can see that the boost is not maximized. Ideally its flat 12psi from 2500rpm to 7000rpm right? I guess I am asking too much.
Why is that transition so high at around 5000rpm?

Looking at the data, I am guessing the base duty as the first value PFC hits before varying it.
On the PC%, I set at 70%, the data is 187. My guess 187/255 is 73%.
On the WG&, I set at 76%, the data is 191, and 191/255 is 75%.
So is that what the base duty cycle % in PFC Commander set for?

spyfish007

The base duty is where it starts to correct for boost. The final value is where it hits the target boost ... so you can see the PowerFC is doing something. Reread some of the post in this thread and another from about the same time frame and see if you get it.

Also think about changing the TCA solenoid. The base tuning will have some dampening at the switchover point-definately 1 or 2 psi. With better tuning you can take that out and get it where there is really no drop.