Co2 Boost control

stevieturbo
Posts: 982
Joined: Sun Dec 07, 2008 2:04 pm

Re: Co2 Boost control

Post by stevieturbo »

you can change the operations of the valves in the software anyway, so the 0-100% is a bit of a moot point for phase/antiphase as they could be reversed in software if you choose.

Or you could reverse plumbing, and reverse software and go round in circles lol.

Not 100% sure on how they operate the fill/empty valves but surely there will be scenarios when you will exclusively want to fill, and exclusively want to vent, and some when you might want a little of both.
So don't think it's as clear cut as having them linked the way Syvecs phase/antiphase is ?

So in operation there could be very fast and large swings from "0%" to 100% and maybe back again as such, and some time in the middle..but for only small changes in actual boost

And even at maximum boost you may not always want 100% fill, simply because that might allow too much pressure build up in the "dome", when you might only want say 20, 30, 40, 50psi or whatever in there. So max boost might actually be 0% duty needed everywhere as the dome would remain pressurised. No sense moving co2 through it and wasting it if it isnt needed

Hence each valve should really have fully independent control

At least that's how I perceive it.
crice
Posts: 11
Joined: Sun Jan 11, 2015 10:38 pm

Re: Co2 Boost control

Post by crice »

Yeah, totally get what you're saying but it's a hard one to get your head around as with both NO ports blocked, the only way it can vent is through the empty solenoid and obviously a solenoid cannot regulate pressure without flow.
MReilly
Posts: 28
Joined: Fri Jan 19, 2018 7:05 pm

Re: Co2 Boost control

Post by MReilly »

Ryan; If you added WGPhaseDuty1 to the available axis options for the customizable maps should you be able to drop the requirement for using the "closed loop PWM 01" function, using the original boost control logic to drive the valves? More like the Cosworth version that Crice has mentioned?

Also, if you set one of the "Basic PWM" outputs to run as a full bridge, with the fill solenoid wired to the + output and the Vent to the -, could you save a further function there I wonder?


I think like Peter / Rice Racing says you are effectively creating a variable air spring with this. I also agree with the runaway boost on the top side observation with "normal" boost control (using compressor outlet pressure). I've always found smaller (high EMAP) turbos much easier to control on the top side, whereas once you free the turbine up, and have a proper MAP/EMAP ratio, the top side of the gate seems to become quite sensitive to small changes in duty. I guess this is for the reason you state of it roughly tracking the EMAP (or being exceeded by the EMAP) more on the weeny turbo setup?

I asked Ryan for a datalog out of interest to see if the pressure in the dome rises and has to be vented rapidly during the spool up phase. Could you perhaps share a screenshot of a datalog from the vehicle you have used this tactic on Peter?

I imagine if you have it setup / plumbed where the main controlled volume is the wastegate itself then you would have to have a very active control to keep the pressure constant during transient events? As soon as the gate begins moving the volume changes, and so with it, the pressure. Surely if you were to add volume to the top side, by way of a tank of some sort, you would make things more controllable, and likely use less gas as a result?

The old school Porsche 956 (I think, may have been the 962?) used basically an air pressure regulator in the cab that let you adjust the set pressure on the top of the gate. I guess all we are ever doing is some variant of this, which is why I find having the pressure of the dome as feedback quite interesting here, I shall have to try it!
crice
Posts: 11
Joined: Sun Jan 11, 2015 10:38 pm

Re: Co2 Boost control

Post by crice »

MReilly, I think I had wrongly assumed that the closed loop element of this strategy only targeted capsule pressure but I'm not experienced enough with Syvecs to easily interrogate how the normal closed loop turbo speed or MAP & PRP strategies tie in to capsule pressure in the provided example. Re-reading the first post though it seems they do somehow.
...as well as link into the Wastegate control strategy
It would be great if Ryan could elaborate a bit on the strategy and how the two solenoids are driven in respect to each other.
Ryan.g
Syvecs Staff - Caretaker
Posts: 296
Joined: Fri May 30, 2008 3:05 pm

Re: Co2 Boost control

Post by Ryan.g »

Evening Gents, Quick reply as have alot of code to get done for the morning but the strategy is in 2 parts

First i am controlling the wg capsule pressure in a closed loop manner using the CLL Pwm1 tables and Basic PWM1 and 2 which are driven from the Output of the CLL PWM. The reason for this is once the target pressure has been achieved the duty will go back to a centre point at 50% and neither of the Fill or Bleed solenoids will be active. This is important to stop it wasting C02 from the Tank

Then i have the Target parts of this strategy linked into the WG control strategy

I don't have the logs as another staff member calibrated it after i got it working but will ask him to send me one

Ryan
stevieturbo
Posts: 982
Joined: Sun Dec 07, 2008 2:04 pm

Re: Co2 Boost control

Post by stevieturbo »

That makes more sense, didn't think of there being a middle "OFF" at 50% duty

but makes sense there would only ever be one solenoid triggered at a time
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