Manual boost:why not after cycling valve!

[bebbetufs]

What will happen if I tap the manual boost controller after the cycling valve?
Will I get some benefit from it at all?

[dewolf]

That is exactly how I have mine. Runs from the wastegate line out the valve to the controller and back to wastegate. This leaves all of the detonation stuff in place, so I'm led to believe. Works fine.

[Paulyy]

i doubt you would get any benefits from it. it just cleans some of the birds nest of vac lines under the intake when you take it out. put the boost controller where the banjo bolt is on the IC pipe so its easy to get to for adjusting.

[dewolf]

Originally Posted by Paulyy

i doubt you would get any benefits from it. it just cleans some of the birds nest of vac lines under the intake when you take it out. put the boost controller where the banjo bolt is on the IC pipe so its easy to get to for adjusting.

He does'nt mean removing the valve. Just adding the controller after the valve.

[bebbetufs]

He does'nt mean removing the valve. Just adding the controller after the valve.

Exactly

[Paulyy]

IMO the valve is pointless if you have a MBC or an EBC

[dewolf]

"By eliminating the cycling valve you are removing the KLR's control of pulling boost when knock is encountered. With aftermarket chips, the KLR will continue to retard timing in increments when knock is detected."

[nize]

putting the boost controller after the cycle valve is essentially the same thing as removing the cycle valve.

in either case the factory second-stage knock protection via boost cut will be removed.

not recommended.

[bebbetufs]

But: If I keep the boost controller all the way closed for normal driving I would get stock boost with stock protection right. And then I would loose some knock protection the more I open the MB the less protection I wil get right? This way I could at least limit the unprotected running to track days.

[Paulyy]

Originally Posted by bebbetufs

But: If I keep the boost controller all the way closed for normal driving I would get stock boost with stock protection right. And then I would loose some knock protection the more I open the MB the less protection I wil get right? This way I could at least limit the unprotected running to track days.

yeah pretty much right, but you mean open for stock boost and closed for more boost?

[bebbetufs]

I thought open boost controller would allow boost beneath the diaphragm and make it harder for the pressure from the main line to open the valve. A closed boost controller leaves only the resistance in the spring to keep the valve closed?

If this is the case then an open MBC would equal higher boost.

[Paulyy]

yes, sorry. i was thinking of a dual port WG. you're right, open = more boost, closed = less boost

[wild man]

An MBC renders the cycling valve useless, due to it's spring-and-ball design of regulating pressure. The only way to maintain any measure of fail-safe operation via the cycling valve, would be to place a constriction (that controls the boost), in the line between the charge pipe and the cycling valve.

[wild man]

On second thought, placing the MBC in the line between the cycling valve and the waste gate, would not render the cycling valve useless. But it would not allow boost to be set to anything higher than stock level.

[bebbetufs]

I'm sorry but I don't follow your reasoning.
Bear in mind that this is only valid with a dual port WG.
If some of the pressure is diverted below the diaphragm in the WG, surely it must increase the pressure needed on top of the diaphragm to open the valve. As this pressure comes from the same source (turbo) it is irrelevant to the WG where this pressure is tapped from. Hence it must be possible to get more than stock boost also by tapping the MBC after the cycling valve...as long as the CV routes all pressure to WG when open.

[wild man]

I think my reasoning may have been incorrect on that, even with a stock WG. Oops.

[nize]

there already is an extensive thread discussing this. putting any type of boost controller anywhere renders the stock cycle valve second stage (boost-cut) failsafe useless.

the only way around this, and to do it correctly, is to use an aftermarket engine management system that also has the second-stage boost-cut failsafe built in.

there is a link regarding boost control in the very first post sticky in this forum. check it out.

[wild man]

To say that there is only one way around the issue, sounds closed-minded, to a free-thinker like me. I'm going to call the makers of the aftermarket engine management system makers on that one. I do, in fact, have a cost-free fix in mind, but it has yet to be implemented/tested, so at this point, I'm not going to say a whole lot. But I will say that theoretically speaking, the factory boost-cut mechanism SHOULD still work. It is why it does not work in practice, is where the problem lies. There are 2 possible phenomenon going on, which need to somehow be corrected. There may be some air leakage in the cycling valve or the WG diaphragm. Combine that with the large area of volume in the tubing between the charge pipe and cycling valve, and between the cycling valve and the waste gate, and there isn't enough flow available through the tiny 20psi banjo bolt constrictor, to properly do the job. The fix that I will be testing is this: Remove 20psi constriction from banjo bolt; Install 20psi constriction directly onto center port of cycling valve (where the stock 11psi one is); Replace the piece of hose going from the cycling valve to the waste gate with small I.D. plastic tubing. There you have it. I can not say at this point that it works, because it hasn't yet been tested. All I can say right now is: Stay tuned!

[nize]

Originally Posted by wild man

Install 20psi constriction directly onto center port of cycling valve (where the stock 11psi one is)

the stock cycling valve 'constriction' is actually .2bar which is 2.9psi. this is why the car can go into 1.2bar (or 2.9psi boost on the factory gauge) 'cripple mode' when the stage2 boost-cut failsafe kicks in.

and in reality the constriction is not at the CV, it is the wastegate spring itself that is holding the 2.9psi of boost, the CV is wide open during failsafe.

if you replace this with a 20psi constriction, you will effectively prevent the CV from going into cripple mode, bypassing the boost-cut failsafe.

trust me when i say that you are not the first person (or even the 1000th person) to think about this over the last 20+years. it really is not as simple as you seem to think.

[bebbetufs]

I was not aware that there is a constriction in the banjo bolt.
From what Nize is saying it sounds like there are no constrictions at all apart from the WG spring. Is this a correct interpretation?