Duratec V6 Supercharged
Discussion
What do you tec guys think of this. Recently I have had a run in with the Yanks They have seen the build of this and say in cannot work which annoyed me a little because it does work and very well too, the reason they have is because of the position of the throttle butterfly is way to far from the valves and will make the engine undrivable, that's why most V configurations have the Supercharger in the middle of the V with the butterfly on the end there is no other way that it will work well according to them, so therefore if so why does this just work, also I would say that it's probably the most driveable car i've ever driven just stick it into 5th and leave it there it will pull from 900rpm to 7000rmp (if you dare) but yet they won't have it, I also explained it has a by pass valve fitted controlled from the plenum chamber from vacuum to pressure same system that is used on a Mini Cooper but still didn't understand why you would need one, getting nowhere on this I then invited them to fly across the pond to Edinburgh where I would meet them in said car to test drive it to put this to bed once and for all, they declined, so what do you think? 
Like all density increasing systems, it of course really depends on the exact arrangement of the thing doing the density increasing!
For positive displacement devices, where their is no internal compression, it matters not where you put the throttle from an efficiency / loss perspective, because all the "compressor" is doing is moving air from inlet to exhaust (it's not actually compressing anything at all!) The resulting manifold air density is simply the balance of flows in (from the "compressor") and out (through the engine). When there is more air coming in than going out, inlet manifold pressure, and hence charge air density, increases.
And throttle is a throttle, it acts to limit the mass flow across it, by providing a pressure drop to oppose that mass flow. As your system is starting and ending at 1 atmosphere, where that throttle is, really doesn't matter! (from an efficiency perspective, other things like supercharger oil sealing can of course be affected)
If you have a "compressor" that is actually a compressor, then things get a bit more complex, because the efficiency of that internal compression will be dependant upon the mass flow though the compressor, but most super chargers have a low amount of internal compression (a lot have none of course as mentioned above)
So if you have a pre-charger throttle, then when it is closed, the down stream system air density falls, and so less air is moved by the supercharger, so the power consumed by that charger drops off. No air bypass is needed, but some s/c don't like having a large negative pressure in their galleries, due to issues with oil sealing (ie they tend to pull in ambient air through those seals and that tends to dry things like their bearings out etc)
If you have a post-charger throttle, then it's better to have a re-circulation bypass around the s/c to avoid an un-necessary energy loss from the s/c doing work that is then dropped across the throttle, but because in all cases the mass flow is limited by the throttle, the overall losses are still reasonable small even without one.
For positive displacement devices, where their is no internal compression, it matters not where you put the throttle from an efficiency / loss perspective, because all the "compressor" is doing is moving air from inlet to exhaust (it's not actually compressing anything at all!) The resulting manifold air density is simply the balance of flows in (from the "compressor") and out (through the engine). When there is more air coming in than going out, inlet manifold pressure, and hence charge air density, increases.
And throttle is a throttle, it acts to limit the mass flow across it, by providing a pressure drop to oppose that mass flow. As your system is starting and ending at 1 atmosphere, where that throttle is, really doesn't matter! (from an efficiency perspective, other things like supercharger oil sealing can of course be affected)
If you have a "compressor" that is actually a compressor, then things get a bit more complex, because the efficiency of that internal compression will be dependant upon the mass flow though the compressor, but most super chargers have a low amount of internal compression (a lot have none of course as mentioned above)
So if you have a pre-charger throttle, then when it is closed, the down stream system air density falls, and so less air is moved by the supercharger, so the power consumed by that charger drops off. No air bypass is needed, but some s/c don't like having a large negative pressure in their galleries, due to issues with oil sealing (ie they tend to pull in ambient air through those seals and that tends to dry things like their bearings out etc)
If you have a post-charger throttle, then it's better to have a re-circulation bypass around the s/c to avoid an un-necessary energy loss from the s/c doing work that is then dropped across the throttle, but because in all cases the mass flow is limited by the throttle, the overall losses are still reasonable small even without one.
This system is pre charger throttle but has a by-pass system however when the throttle is closed the valve is open but the position of the by-pass in the pipework means it's not pulling all the air through the s/c almost recirculation of air in the gallery also even on idle the throttle blade is open quite a bit, I don't see it stressing out the charger on idle, it's also done 10,000 miles now with no issues or do I have somthing wrong here?
blake999 said:
This system is pre charger throttle but has a by-pass system however when the throttle is closed the valve is open but the position of the by-pass in the pipework means it's not pulling all the air through the s/c almost recirculation of air in the gallery also even on idle the throttle blade is open quite a bit, I don't see it stressing out the charger on idle, it's also done 10,000 miles now with no issues or do I have somthing wrong here?
The bypass is irrelevant when the throttle is not very open because there is no air to bypass...........Max_Torque said:
what is left "downstream" of a closed throttle........
Charge air is left downstream of the throttle. Which will then be compressed by the supercharger, causing wasted heat and wear and inefficiency and requiring the throttle to be closed even further to reduce the pressure and density upstream of the supercharger to maintain the same mass air flow.Open the recirc valve and the excess air volume can return to the supercharger intake, hence no pressure rise across the supercharger and no wasted heat, wear and inefficiency in the blower.
GreenV8S said:
Charge air is left downstream of the throttle. Which will then be compressed by the supercharger, causing wasted heat and wear and inefficiency and requiring the throttle to be closed even further to reduce the pressure and density upstream of the supercharger to maintain the same mass air flow.
Open the recirc valve and the excess air volume can return to the supercharger intake, hence no pressure rise across the supercharger and no wasted heat, wear and inefficiency in the blower.
er, nope.Open the recirc valve and the excess air volume can return to the supercharger intake, hence no pressure rise across the supercharger and no wasted heat, wear and inefficiency in the blower.
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