It would need to be plumbed the same as if setting up for the Internal wastegate above but then set the phase linearization according to how it is set of the external above on the antiphase table
Some detailled questions to the plumbing info for external dual port wastegates:
As decribed above, the metal nipple shall be feeded to the pressure source, and the side nipple to the wastegate top port. By this way the solenoid is routed to the top port with its "normally open" path. To provide spring pressure operation, there must not be applied any external pressure to the top port. In order to translate a rising opening pressure of the wastegate according to a rising dury cycle from 0 to 100% to the ecu, the phase linearisation has to be inverted. That means, 0% over spring pressure is 100% duty cycle to the solenoid coil, so the NO path will fully be closed, no external pressure is applied to the top port.
So far, so good, i did it that way, and all worked fine.
But is there a certain reason to operate this way ?
I'm asking, because i had the following issue:
I modified my turbo from 66 to a higly efficient 71mm billet compressor, that provides the same low end spool up, but much more top end. This turbo kicks in amazingly strong a soon as it has reached 1 bar. Intending a smooth response to the throttle i set the threshold for boost control operation to 50% TPS.
What happened ? Although there now is installed a bigger compressor wheel and a larger exhaust housing, the turbo needs significantly less gas flow than before to achieve the same boost pressure. When i gently opened the throttle to 45%, the boost shot up to 2,7bar, although no boost control should be active below 50% TPS !!!
Checking all my logs i got the problem sorted:
The solenoid has not been activated at all below 50% TPS. But a 100% duty cycle would have been needed to keep the boost down to spring pressure, what would have been intended below 50% TPS. I now solved the problem by a threshold of 15% TPS for starting the wastegate control and applying a properly rising TPS based map target multiplier.
But i wonder wether it is a good idea to route the pneumatic path of the solenoid this way. If the solenoid fails or there is a broken wire in the loom supplying the solenoid, the boost always will shoot up out of control until the engine or the turbo gets blown up, anticipated that no map limiter value is properly set there.
Why istn't the setup choosen the other way using the NC path in combination with a non inverted phase linearisation ? Is there a certain reason for ?
j.oe wrote:Some detailled questions to the plumbing info for external dual port wastegates:
As decribed above, the metal nipple shall be feeded to the pressure source, and the side nipple to the wastegate top port. By this way the solenoid is routed to the top port with its "normally open" path. To provide spring pressure operation, there must not be applied any external pressure to the top port. In order to translate a rising opening pressure of the wastegate according to a rising dury cycle from 0 to 100% to the ecu, the phase linearisation has to be inverted. That means, 0% over spring pressure is 100% duty cycle to the solenoid coil, so the NO path will fully be closed, no external pressure is applied to the top port.
So far, so good, i did it that way, and all worked fine.
But is there a certain reason to operate this way ?
I'm asking, because i had the following issue:
I modified my turbo from 66 to a higly efficient 71mm billet compressor, that provides the same low end spool up, but much more top end. This turbo kicks in amazingly strong a soon as it has reached 1 bar. Intending a smooth response to the throttle i set the threshold for boost control operation to 50% TPS.
What happened ? Although there now is installed a bigger compressor wheel and a larger exhaust housing, the turbo needs significantly less gas flow than before to achieve the same boost pressure. When i gently opened the throttle to 45%, the boost shot up to 2,7bar, although no boost control should be active below 50% TPS !!!
Checking all my logs i got the problem sorted:
The solenoid has not been activated at all below 50% TPS. But a 100% duty cycle would have been needed to keep the boost down to spring pressure, what would have been intended below 50% TPS. I now solved the problem by a threshold of 15% TPS for starting the wastegate control and applying a properly rising TPS based map target multiplier.
But i wonder wether it is a good idea to route the pneumatic path of the solenoid this way. If the solenoid fails or there is a broken wire in the loom supplying the solenoid, the boost always will shoot up out of control until the engine or the turbo gets blown up, anticipated that no map limiter value is properly set there.
Why istn't the setup choosen the other way using the NC path in combination with a non inverted phase linearisation ? Is there a certain reason for ?
Jürgen
Jurgen
Its because most boost solenoids on the market blow open the normally closed seat in the solenoid body at higher boost levels so we plumb it in so that the energized coil jams the valve seat and stops this happening.
You can set boost cut limits based on cal postion so in the unlikely event one of our solenoids fails it will just hit the cut and protect the engine package.
As Ryan has already mentioned, the springs in a lot of solenoids are too weak to hold back high boost pressure, and by definition the magnetic force must exceed the spring force otherwise it wouldn't move! Most solenoids use a magnetic gap, the force rising as the gap closes, this means when the valve is blocking the NO port it will require MUCH more pressure from the compressor to overcome it than it would if the valve was run NC style.
Another issue arises with the solenoid linearity. When run in the NC style, the force from the compressor assists the opening of the valve, so even with equal duty, the transfer function is nonlinear, allowing more air through than it should, as the boost rises. It is also harder for the valve to seat again. Compare this to the NO operation : the pressure holding the valve shut will be less than the compressor pressure (it will be the pressure on the gate), it is therefore less affected by the increase in compressor pressure. The magnetic force is much greater, and seating the valve again is assisted rather than resisted.
There is of course the "danger" with regard to the solenoid failing and thus trying to make maximum boost. As Ryan has already said, you can set per-cal-position boost limits. It is also worth remembering that the Syvecs boost limit is very quick - where other ECUs need between 0.1 and 0.4 seconds of overboost before trying to do something about it, a Syvecs can react within one cylinder event of an overboost condition (no fixed delay since it is engine synchronous). There are of course still "gotchas" - a cylinder that is already being fuelled has to fire, but beyond that it is normally possible to catch an overboost condition very very quickly. I certainly would NOT recommend running gate control this way on other slower ECUs, as Jurgen says, that could be a recipe for disaster!
Thanks for sharing this info Pat and Ryan, it is very interesting, I had never considered what is going on inside the actual solenoid before now.
I see a lot of these Pierburg style boost solenoids used, and use them almost exclusively now myself, albeit on relatively low boost applications. At what sort of a boost pressure do you generally start to see this sort of an issue occurring with these valves? I assume the problem tends to manifest itself as a gradually increasing lack of effect on boost as the duty goes up?
