I tried to do something awesome... and failed (1 Viewer)

[BreckenridgeCruiser]

Mine's disconnected. GT2052 on a 2B. I don't get above 14-15 PSI unless I blow my butterfly valve lines

Agreed that reducing the boost a bit may give you high EGT's but if you don't overfuel on the full boost set, and also don't reduce the boost too much with the controller, you should be fine. All you'd want to do is reduce the max boost to around 10-11 right? You should not be putting that much more fuel in to make a severe difference, especially since you will most likely have the boost at full when you are loaded up with gear or on a big hill...

 

[gbentink]

Yes but with the amount of fuel your pumping, that is going to happen.

At a fixed rpm and boost pressure, more fuel = marginally higher mass flow but dramatically higher volumetric flow and this is what powers your turbo

I disconnected mine and by changing the fuel at say 2000rpm, I could change the boost from 15psi to 30psi.

be careful disconnecting your waste gate line, i did that and maxed out my 45psi gauge straight away lol.

 

[gbentink]

I might have read is post wrong, but anyway;

The boost controller that was being wokred on looks all the world like a ball/spring/bleed controller where the cable adjusts the spring pretension on the ball. The purpose is to RASIE the boost to levels higher than the preset wastegate actuator pressure.

It achieves this by using a bleed to create a pressure drop to the actuator.

For example, if the wastegate actuator is set for 7psi, and you want to run 14psi, you simply bleed off the pressure through what is effectively a small leak to the point that the wastegate actuator does not get 7psi until the manifold pressure reached 14psi.

The other thing is that the ball/spring/bleed setup operates in such a way as to allow not pressure at all to the watsegate actuator until sufficient manifold pressure overcomes the spring pressure and the ball uncovers the line to the wastegate actuator. There is a bleed between the ball valve and the actuator. The bleed means that even if the valve is slightly leaking boost, it will bleed out and prevent the effect that was mentioned where your wastegate may partially open.

this type of wastegate controller has another benefit. That is it helps maintain a consistent boost pressure through the whole rpm range when at max load.

the problem is that exhaust manifold pressure builds with rpm and this pressure is working to try and open the wastegate flap. On a typical setup you can see this where boost could be set for 14psi at 2000rpm but it is maybe 11 at 4000rpm. Providing the turbo is correctly sized, this is caused by the effect described. The ball/spring/bleed style of boost controller does a very good job at getting this variation under control.

You can control boost by using the fuel setting which is called "free floating" but unless you have a perfect turbo design and operate in the same climating and elevation conditions, it is costing you fuel economy. You will use more fuel and make less power when running too lean by having free floating boost. This decrease in efficiency is due to excessive pumping losses. There is a pouint where the increased efficiency of the compression ratio increase (by higher boost) is outweighed by the compressor drive energy cost to achieve it

Cheers, Graeme

Drew. It is actually more simple than you think.

A boost controller can only lessen the max boost as allowed by the wastegate. I get 15psi by disconnecting the wastegate actuator and having the outlet from the compressor housing go straight to my boost gauge. Therefore, I essentially have no wastegate.

So, to get higher boost, you need to adjust your wastegate to set the max boost you want (with the boost controller off - fully blocked), and then use the kick ass system you built to allow earlier waste gate action when you want to reduce the boost.

This is all under the assumption that you have an adjustable wastegate. If not, see if you can modify the actuator arm to have the WG open later to increase boost under the same fuel level before adjusting the fuel just for more boost.

Edit: I realize I just summarized what everyone is saying, but the gist is that no boost controller blocks all of the pressure to the wastegate. Wastegates also are not on-off only, so even with the controller all of the way on, you may be opening the wastegate a little, just enough to spill that extra 5psi. try running your wastegate hose to your boost gauge only and see what you get with no wastegate connection. if you are still at 10psi, turn up the fuel and get the rig to where you want it at max boost, then add in the controller and wastegate to be able to adjust on the fly...

 

[gbentink]

I might have read the quoted post wrong, but anyway;

The boost controller that was being worked on looks all the world like a ball/spring/bleed controller where the cable adjusts the spring pretension on the ball. The purpose is to RAISE the boost to levels higher than the preset wastegate actuator pressure.

It achieves this by using a bleed to create a pressure drop to the actuator.

For example, if the wastegate actuator is set for 7psi, and you want to run 14psi, you simply bleed off the pressure through what is effectively a small leak to the point that the wastegate actuator does not get 7psi until the manifold pressure reached 14psi.

The other thing is that the ball/spring/bleed setup operates in such a way as to allow no pressure at all to the watsegate actuator until sufficient manifold pressure overcomes the spring pressure and the ball uncovers the line to the wastegate actuator. There is a bleed between the ball valve and the actuator. The bleed means that even if the valve is slightly leaking boost, it will bleed out and prevent the effect that was mentioned where your wastegate may partially open even at pressures lower than the actuator setting.

this type of wastegate controller has another benefit. That is it helps maintain a consistent boost pressure through the whole rpm range when at max load.

the problem with these conventional internal wastegates is that exhaust manifold pressure builds with rpm and this pressure is working to try and open the wastegate flap. On a typical setup you can see this where boost could be set for 14psi at 2000rpm but it is maybe 11 at 4000rpm. Providing the turbo is correctly sized, this is caused by the effect described. The ball/spring/bleed style of boost controller does a very good job at getting this variation under control.

You can control boost by using the fuel setting which is called "free floating" but unless you have a perfect turbo design and operate in the same climating and elevation conditions, it is costing you fuel economy. You will use more fuel and make less power when running too lean by having free floating boost. This decrease in efficiency is due to excessive pumping losses. There is a pouint where the increased efficiency of the compression ratio increase (by higher boost) is outweighed by the compressor drive energy cost to achieve it

Cheers, Graeme

Drew. It is actually more simple than you think.

A boost controller can only lessen the max boost as allowed by the wastegate. I get 15psi by disconnecting the wastegate actuator and having the outlet from the compressor housing go straight to my boost gauge. Therefore, I essentially have no wastegate.

So, to get higher boost, you need to adjust your wastegate to set the max boost you want (with the boost controller off - fully blocked), and then use the kick ass system you built to allow earlier waste gate action when you want to reduce the boost.

This is all under the assumption that you have an adjustable wastegate. If not, see if you can modify the actuator arm to have the WG open later to increase boost under the same fuel level before adjusting the fuel just for more boost.

Edit: I realize I just summarized what everyone is saying, but the gist is that no boost controller blocks all of the pressure to the wastegate. Wastegates also are not on-off only, so even with the controller all of the way on, you may be opening the wastegate a little, just enough to spill that extra 5psi. try running your wastegate hose to your boost gauge only and see what you get with no wastegate connection. if you are still at 10psi, turn up the fuel and get the rig to where you want it at max boost, then add in the controller and wastegate to be able to adjust on the fly...