ST215 throttle bypass

[snwtoy]

I'm having a real cnut of a time getting the throttle bypass hose to stay connected into the airbox->turbo hose.

This is due to the intercooler being slightly off the factory alignment, and the airbox->turbo hose having been contorted to suite the aftermarket turbo.

Is there any issue with just blocking one end off, and putting one of those little breather filters on the throttle bypass hose instead?

Cheers

[fivebob]

Shouldn't be any problem prvided you block off the pipe from the airbox. The vacuum diagram shows the Turbo VSV as connected to the same line, but in your case it won't matter.

[snwtoy]

Thanks

Made a mistake in the dark yesterday arvo thinking it was the throttle bypass, it's just the rocker cover breather (not shown on your diagram?).

So I've blocked the intake end, and put a little filter on the other end, awesome.

Also had to repair my intake temp sensor after the wires snapped at the back of the plug. Bit of a fiddly job taking that plug apart, but got there in the end.

Can I use the BOV feed to also activate the wastegate? There doesn't appear to be any other useable lines, unless I T off the Turbo VSV line (but I'm not sure that's actually pressure)?

[fivebob]

What sort of plumbing does the wastegate require?

[snwtoy]

What sort of plumbing does the wastegate require?

Just a turbo pressure feed

[fivebob]

Sholud be Ok, but it might slow down the BOV response a little bit

[snwtoy]

Hmmm... that's not cool. The factory bov seems to struggle a bit with the new turbo, I hear a fair amount of turbo stall/chatter.

Back to the original plan of getting a proper feed off the turbo methinks.

[fivebob]

Are you sure it's turbo stall(very unlikely) or simply just BOV flutter which happens even with the stock turbo.

[snwtoy]

I am definitely hearing a similar chattering noise to the one I had on my GTti before fitting a bov. Which I guess is not to say that it was there even after the bov fitment, but the vented to atmo bov disguised it.

You don't think the .7 A/R compressor turbo could be more than it could handle? I'll take your word for it because I don't fully understand

[MasCam]

Sorry to hijack the thread but I was looking at the diagrams for the vacuum piping on my ST246 and trying to reconcile them against the above diagram (and I do realise that it will be different, thats part of the point I'm getting to)

On the epc for the ST246 there is a "valve, duty vacuum switching" which seems to be connected between the wastegate actuator and the airbox.

This is defiantly not shown on the ST215 diagram (Which seems much simpler) so the question is, does the st246 have some form of electronic boost control or is this valve for something else? Is it just the vsv valve that limits boost until the appropriate conditions are met?

Here's a couple of links.

ST246

ST215

Thanks
Chris

[cedwards]

another hijack,
looking at fivebob's diagram the blow off valve actuator plumbing is how I would expect it to be, in reality unless i'm mistaken it is totally different with both pipes teeing into the same point on the manifold with a non return valve plumbed into the one.. Would this possibly be the cause of the normal flutter fivebob mentions?
I can't help but feel the diagram's plumbing is better than the actual plumbing for the blow off actuator?

[fivebob]

looking at fivebob's diagram the blow off valve actuator plumbing is how I would expect it to be, in reality unless i'm mistaken it is totally different with both pipes teeing into the same point on the manifold with a non return valve plumbed into the one..

The diagrams plumbing is technically correct in that it is an engine vacuum diagram, however this means it doesn't show the workings of the BOV.

I guess they figured that it wasn't really necessary as the valve in question would just appear as a straight through connection because it's not a Non-Return Valve, it's actually called a Vacuum Transmitting Valve(VTV). The function of which is to delay the signal going to one side of the diaphram to make the valve open and shut faster.

Would this possibly be the cause of the normal flutter fivebob mentions?

Indeed it is, one of then by products of a VTV is the that valve has a tendency to open and shut rapidly (flutter) on partial throttle openings. This is by design and is why it's actually known as an Air Bypass Valve(ABV) not a BOV.

I can't help but feel the diagram's plumbing is better than the actual plumbing for the blow off actuator?

Assuming you mean the removal of the VTV, in which case you would be incorrect. The VTV mechanism is what makes the stock BOV so good and allows it to function as an air bypass valve when the engine is off boost.

[cedwards]

Once again fivebob your knowledge is excellent!
But....
Wouldn't the blow off valve work that much better if both chambers were plumbed to their respective sides of the throttle body as in the diagram while still leaving the VTV in place?

The spring containing "A" chamber plumbed into the post throttle position, and the bottom "B" (VTV affected chamber) plumbed pre throttle.

By my reckoning this will still allow it to still open in the pre boost state and possibly enhance it's opening in the throttle just closed turbo producing boost blow off valve state?

[cedwards]

My reasons for asking is that while working 100% sometimes on idle my BOV with produce a tapping noise almost like hydraulic lifters.
Removing the BOV you can feel the vibration on the valve. In this state the valve is fully open and "bouncing" on it's "stopper".
I was wondering by plumbing each chamber to it's respective side of the throttle would this not smooth the vacum out and possibly minimise this noise?

[fivebob]

Wouldn't the blow off valve work that much better if both chambers were plumbed to their respective sides of the throttle body as in the diagram while still leaving the VTV in place?

Nope, it might open a fraction quicker, but it would take much longer to close therefore lag would increase and it wouldn't be able to properly function as an air bypass valve. I also think it would flutter a lot worse because of the greater fluctuations in pressure difference across the diaphragm.

The VTV essentially acts the same way as the plumbing you suggest, with the lower part of the valve still seeing boost when the upper part sees vacuum so I doubt you could measure the difference in valve opening speed.

[cedwards]

Excellent!
I won't "fix" what isn't broken then.
Thanks for the info