Gillis valve installation

[WaltM]

Update...

Well, checked the vacume lines (and instructions) and found out that the boost line should be run from the firewall and NOT from the turbo housing.

The car came with a needle valve and it was getting pressure directly from the turbo. So like the ham-head that I am, I just swapped the needle for the Gillis.

Anyway, I ran a line from the firewall and capped the lines on the housing and guess what? It runs much better.

Just one last question...

Why would you run it all the way from the firewall and how does it "know" when the boost reaches a set level?

[TurboPete]

Walt, this may? explain your question.

For some reason it woun't let me post the whole link. it cuts it off.

Go here:

http://www.turbotbird.com/FAQPage/FAQpage2.html

And look for the article "How Factory and Aftermarket Boost Controls Work"

[WaltM]

Thanks for the link!

That was a nice explanation and gives me a good idea on how it works. But I'm still curious how the vacume port on the firewall can suppy the air at the right time to the Gillis valve and open the wastegate.

The way the needle valve was attached to the turbo housing seemed logical; air pressure from another source doesn't make sense, but it works really well.

Go figure.

[TurboPete]

"That was a nice explanation and gives me a good idea on how it works. But I'm still curious how the vacume port on the firewall can suppy the air at the right time to the Gillis valve and open the wastegate. "

The "vacuum tree" on the fire wall sees The same condition as the intake manifolds/intake runners in the cylinder head, be it vacuum or boost. This is because the vacuum tree is fed directly by the intake manifolds. Pressure equalizes everywhere in the system (theory) When boost builds in the intakes, it also builds in the vacuum tree and any hose tied to the tree that doesn't contain a one way check valve to keep boost out of that subsystem (EGR for example.) Same happens in the hose going to the Gilliis. When that boost reaches the psi level that the Gillis is set to open at. the ball inside the Gillis comes off the seat and the boost signal is passed on to the WGA, which opens the WG to moderate the boost level.

There is no reason why the signal hose to the Gilllis cannot be sourced off the compressor outlet as opposed to the vacuum tree. There may be some difference in the level of the boost signal (psi) between the two depending on the pressure drop across the intercooler and any related piping.

[Tooltime]

Originally posted by MikeFleming
If manifold pressure were static, then this would be accurate.

Since it's not static - rather it has a tendency to fluctuate rapidly - there can be considerable latency with long sections of tube and tubes of various sizes. Remember that the entire volume of the tube(s), and whatever restrictions it may have from being different sizes, to/from the boost control valve must change pressure before it will sense a change.

Shorter, smaller diameter hoses - that aren't so small as to cause a time-delay restriction - is the best for signal response. Think of the time it takes for water to come out the end of a 50 foot gargen hose from when the faucet is actually opened. Then how long for the flow to stop after the faucet is closed again. That's latency - amplified by hose length.

The *best* place to connect any boost control device [to sense pressure changes] is off the compressor outlet using a short piece of 1/4 inch hose - say about 6 inches.

Remember that post-charge cooler pressures are often much lower than the compressor outlet pressures and the response can easily be over a half second after the charge cooler path - such as from the firewall-mounted vacuum tree.

Note that he FPR is connected directly to the upper intake manifold - and it uses a very short piece of small diameter hose. Learn from this.

So your saying to take the plug out of the turbo that the kit supplied and use that port to supply vacuum to the adjustable boost guage? Like it was in the original setup.

[WaltM]

Originally posted by TurboPete
"The "vacuum tree" on the fire wall sees The same condition as the intake manifolds/intake runners in the cylinder head, be it vacuum or boost. This is because the vacuum tree is fed directly by the intake manifolds. Pressure equalizes everywhere in the system (theory) When boost builds in the intakes, it also builds in the vacuum tree and any hose tied to the tree that doesn't contain a one way check valve to keep boost out of that subsystem (EGR for example.) Same happens in the hose going to the Gilliis. When that boost reaches the psi level that the Gillis is set to open at. the ball inside the Gillis comes off the seat and the boost signal is passed on to the WGA, which opens the WG to moderate the boost level.

That's what was driving me nuts!

[jayG]

Well Im gonna put my 2 cents in here. The way I see it the gillis valve works best off the pressure supplied from the factory vacuum tree when under acceleration and that pressure is then transfered to the accuator that opens the wastegate. Since the gillis vavle can keep the wastegate closed longer than the factory system, hence more boost, I fail to see what difference it makes how long the pressure hose to the bcv is since the bcv bleeds off pressure anyway. In other words the more you keep pressure from getting pass the bcv the more boost you build right? So why would you want quick pressure to open activate the wastegate thus beeding off boost? Doesnt make since to me. So time delay to the bcv, the way I see it, is irrelevant. Besides Ive ran my pressure hose from the compressor outlet and the boost would not hold steady...dunno why, dont care. I just know the gillis valve works best on my car by running the pressure hose from the vacuum tree.

[TurboPete]

Too much time delay could allow a boost spike as in new head gasket time, or worse. Personally I have never had a problem with sourcing at the tree but I do keep hose dameter small. I agree with Mike that the quickest signal will come from the compressor outlet. The time delay factor is one reason I don't run an adjustable from inside the cabin. Too much plumbing length

[jayG]

Yeah I can see where running from inside the car would not be good, Im just saying My gillis valve worked best by using the tree as per the instructions. Could be the design of that particular boost control valve?

[WaltM]

Originally posted by jayG
Well Im gonna put my 2 cents in here. The way I see it the gillis valve works best off the pressure supplied from the factory vacuum tree when under acceleration and that pressure is then transfered to the accuator that opens the wastegate.

Since I've used both the vacuume tree and the turbo housing as boost sources, I can vouch that the vacuume tree provides a more "stable" source of pressure. It appears to be much more cosistant than what was coming from the housing; even the stock gauge seems to be a bit more accurate.

Originally posted by jayG
I fail to see what difference it makes how long the pressure hose to the bcv is since the bcv bleeds off pressure anyway. I just know the gillis valve works best on my car by running the pressure hose from the vacuum tree.

A friend of mine had explained to me that air pressure travels through an engine "instantaniously" and told me not to be too concerned about line length. After viewing this thread, I only half agree with his statement. I'm sure that a 6' length will take 2x longer than a 3' length and delay the WG opening.

[mutant]

Did anybody mention ByPass Valves or blow-off valves in relation to this topic? The way I see it, if you control the gillis valve from the vacuum tree or any place past the throttle body it is foolish to not install a BPV. If you control the gillis valve from anyplace on the compressor side of the throttle body, a BPV is nowhere near as important.
To my mind the best place to get an air signal to control the gillis valve would be just before the entrance to the throttle body. This way the wastegate control loop would adjust for different pressure drops across the intercoolerand piping( especially a front-mount) due to changing weather conditions. Yearly temperature swings around here are 90+ degrees.
I'm the kind of person who likes to find a setting that works for all conditions and then leave the adjustment alone. On the other hand, if you are the kind of person that will be fiddleing with the boost pressure control all the time anyway, then I would tend to agree with MikeF and take it from the compressor housing.
-Dana

[TurboPete]

The way I see it, if you control the gillis valve from the vacuum tree or any place past the throttle body it is foolish to not install a BPV. If you control the gillis valve from anyplace on the compressor side of the throttle body, a BPV is nowhere near as important.

The point of a BPV or BOV is to protect the turbo from the shock of sudden stopping or even reversal due to the compressed wave bouncing off the closed throttle plates and being directed back at the compressor wheel. The other benefit is faster spool up once you are back into the throttle. From that standpoint I'm not sure it makes much difference where the BCS is sourced from.

I don't do a lot of fiddling with my valve. I may adjust it twice a year for temperature changes, just to be safe, but it's temperature that I'm responding to (ie potential for detonation), not a pressure drop across the IC