FP 25psi WGA Question
Please do, I'm about to swap up to a red with an 18 actuator, I like to have lots of preload too
Side note, will Robert cut a 9.8 for the red turbine wheel? I'm afraid I'm going to miss my bbk spool till I can build a 2.2.
Side note, will Robert cut a 9.8 for the red turbine wheel? I'm afraid I'm going to miss my bbk spool till I can build a 2.2.
The last time that I called FP they didn't have anymore MHI 9.8cm housings in stock. There is not much call for running the tighter housings anymore.
The JB Red/10.5 doesn't spool worth squat on a stock block. I have pretty much modded my 18# actuator to the max, crushed my DV to the max, and even set my cams as advanced as I will(+2/0) and it is still lazy.
The last time that I called FP they didn't have anymore MHI 9.8cm housings in stock. There is not much call for running the tighter housings anymore.
The last time that I called FP they didn't have anymore MHI 9.8cm housings in stock. There is not much call for running the tighter housings anymore.
Couple things come to mind:
1) Are they referring to "cracking pressure", which is when the flapper valve first moves up off its seat on the turbine housing, or are they instead referring to full open pressure?
2) The 18# rating for example, is a static measurement. They attach a compressed air source to the nipple on the actuator canister and measure how many PSI of compressed air it takes to lift the flapper valve.
However, when the turbo/actuator assembly is attached to your exhaust manifold with the engine running and exhaust gases flowing through the turbine housing there also is turbine inlet pressure which should be taken into account.
This turbine inlet pressure flows though the turbine housing's bypass port and exerts an additional force on the face of the flapper valve. So, not only is there the 18 PSI of boost acting on the diaphragm forcing the flapper valve to open. You must also factor in, or add turbine inlet pressure.
This is not definitive obviously. These are just a couple possible answers to your question concerning the disparity between an actuators advertised opening pressure and the realworld dynamic opening behavior of the little beasts.
1) Are they referring to "cracking pressure", which is when the flapper valve first moves up off its seat on the turbine housing, or are they instead referring to full open pressure?
2) The 18# rating for example, is a static measurement. They attach a compressed air source to the nipple on the actuator canister and measure how many PSI of compressed air it takes to lift the flapper valve.
However, when the turbo/actuator assembly is attached to your exhaust manifold with the engine running and exhaust gases flowing through the turbine housing there also is turbine inlet pressure which should be taken into account.
This turbine inlet pressure flows though the turbine housing's bypass port and exerts an additional force on the face of the flapper valve. So, not only is there the 18 PSI of boost acting on the diaphragm forcing the flapper valve to open. You must also factor in, or add turbine inlet pressure.
This is not definitive obviously. These are just a couple possible answers to your question concerning the disparity between an actuators advertised opening pressure and the realworld dynamic opening behavior of the little beasts.
Last edited by sparky; Oct 16, 2012 at 09:45 PM.
I have been playing with the idea of acquiring a Banks Engineering "Big Head" actuator to see if I can somehow adapt one to work on a 16G. I at least want to take a look at one. Maybe it is doable....I don't know.
So, Ratty, in further response to your question. A WGA's advertised opening pressure is merely a measurement of how many PSI of intake manifold(boost pressure) acting against WG spring pressure it takes to reach equilibrium at which point the flapper will lift. This can be tested with a bicycle pump.
The reason that you notice the flapper valve opening way earlier than the WGA's advertised opening pressure is that the static test described above does not take turbine inlet pressure into account.
To give you an idea of the impact of turbine inlet pressure on the equation, consider that as a rule of thumb the ratio between turbine inlet pressure and boost pressure is at least 2:1 at factory boost levels. That is for each PSI of boost it takes two PSI of exhaust pressure to produce it.
Let's assume that the face of the flapper valve is 1" in diameter. So, when your turbo's compressor is producing 20 PSI of boost your turbine's inlet area, and thus the face of the flapper valve is seeing approximately 40 PSI of exhaust pressure.
Is it clearer now? Or more confusing?
The reason that you notice the flapper valve opening way earlier than the WGA's advertised opening pressure is that the static test described above does not take turbine inlet pressure into account.
To give you an idea of the impact of turbine inlet pressure on the equation, consider that as a rule of thumb the ratio between turbine inlet pressure and boost pressure is at least 2:1 at factory boost levels. That is for each PSI of boost it takes two PSI of exhaust pressure to produce it.
Let's assume that the face of the flapper valve is 1" in diameter. So, when your turbo's compressor is producing 20 PSI of boost your turbine's inlet area, and thus the face of the flapper valve is seeing approximately 40 PSI of exhaust pressure.
Is it clearer now? Or more confusing?
Last edited by sparky; Oct 16, 2012 at 10:22 PM.
There are other dynamic pressure forces and factors that have to be considered as well. Some of these are specific to the particular configuration or combination of wheels and housings chosen by FP to arrive at the final result that is the 71HTA turbo.
The stock TD05H turbine wheel is a relatively high backpressure design with smallish major and minor diameters. This means that inherently there are going to be higher turbine inlet pressures than there would be if they had chosen the slightly higher mass, lowe back pressure turbine wheel used in the 73 HTA Green, or the even larger wheel used in the Red. A turbine wheel with larger x-section and larger exducer would produce lower levels of turbine inlet pressure.
It is easy to understand how the restrictive hotside configuration is going to produce relatively quick spool but at the same time relatively high levels of exhaust back pressure in general localized within the turbine housing as high turbine inlet pressure which helps lift the flapper off its seat early.
This high turbine inlet pressure should not only be viewed as a factor at or near peak boost. It is an exponential factor during turbo spoolup. Thus, in contrast you don't read about the relatively slower spooling Red turbos having wastegate seating issues.
Why? The Red has the same high inertia/low back pressure turbine used in the FP Black. The rate of spool is slower and the turbine inlet pressures are significantly lower than they would be with the stock TDO5H turbine.
The stock TD05H turbine wheel is a relatively high backpressure design with smallish major and minor diameters. This means that inherently there are going to be higher turbine inlet pressures than there would be if they had chosen the slightly higher mass, lowe back pressure turbine wheel used in the 73 HTA Green, or the even larger wheel used in the Red. A turbine wheel with larger x-section and larger exducer would produce lower levels of turbine inlet pressure.
It is easy to understand how the restrictive hotside configuration is going to produce relatively quick spool but at the same time relatively high levels of exhaust back pressure in general localized within the turbine housing as high turbine inlet pressure which helps lift the flapper off its seat early.
This high turbine inlet pressure should not only be viewed as a factor at or near peak boost. It is an exponential factor during turbo spoolup. Thus, in contrast you don't read about the relatively slower spooling Red turbos having wastegate seating issues.
Why? The Red has the same high inertia/low back pressure turbine used in the FP Black. The rate of spool is slower and the turbine inlet pressures are significantly lower than they would be with the stock TDO5H turbine.
Last edited by sparky; Oct 17, 2012 at 07:01 AM.
73 hta turbine would be interesting on the 71 then probably Better spool ?
Edit I could clip my 71 for pretty cheap + 2 weeks down time
Mind you I have s2 cams
Edit I could clip my 71 for pretty cheap + 2 weeks down time
Mind you I have s2 cams
Last edited by 211Ratsbud; Oct 17, 2012 at 06:57 AM.
Yeah, i like the idea of a clipped TD05H wheel inside a ported 9.8 housing. That eould definitely require a 25# actuator. I like even more your idea of clipping a 73 turbine and and stuffing that in a cut and ported 9.8. This option would result in a further reduction in back pressure due to the larger exducer diameter in addition to the larger major wheel diameter.
Well, I have gone and driven this thread way OT. Sorry, OP!
Ratty and I enjoy the academic exercise and Lego-like hypothetical variables and configurations possible from recombining MHI 16g components along with FP's upgraded cutting edge advancements such as HTA, Flow Advancement, ceramic BB, etc.
This is all fine and dandy. Robert himself is the ultimate experimenter. He used to run an OS Green/9.0.....WILD! The 71 HTA compressor wheel is after all his brain child.
Robert arrived at the final production iteration of the 71 HTA after a thurough design, development, and testing process. The 71 compressor flows 51 lbs and it is a relatively inexpensive compressor wheel swap.
Originally, as I recall, he had tried to combine the 71 HTA wheel with the OS green's slightly larger turbine wheel but that particular wheel combo didnt test well. So, he opted for the stock TD05H turbine wheel.
Ratty and I enjoy the academic exercise and Lego-like hypothetical variables and configurations possible from recombining MHI 16g components along with FP's upgraded cutting edge advancements such as HTA, Flow Advancement, ceramic BB, etc.
This is all fine and dandy. Robert himself is the ultimate experimenter. He used to run an OS Green/9.0.....WILD! The 71 HTA compressor wheel is after all his brain child.
Robert arrived at the final production iteration of the 71 HTA after a thurough design, development, and testing process. The 71 compressor flows 51 lbs and it is a relatively inexpensive compressor wheel swap.
Originally, as I recall, he had tried to combine the 71 HTA wheel with the OS green's slightly larger turbine wheel but that particular wheel combo didnt test well. So, he opted for the stock TD05H turbine wheel.
Last edited by sparky; Oct 18, 2012 at 05:21 AM.