CF intake pics- and our new friend's car- More pics added 11-29-09
11-27-2009, 09:32 PM
#32
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On a basically stock 5 liter 32 valve the carbon intake should be less efficient in the low midrange and lacks the tuning of the resonance flap of the stock S-4 intake. The Threshie intake made a difference on highly modified stroker engines which failed to make much more power with better headers, bigger valves , porting etc and the last step was removing the restriction of the STOCK intake..... Lacking such a large and efficient air pump (6.5 liters) the stock intake probably was designed by Porsche to work pretty well....if they could have easily found another 20-25 hp while they were improving upon the 85-86 32 valve intake one might think they would have done it. The stock intake costs thousands of dollars as it is ! So yes I think big camshafts will be the next item on your wish list.....followed by a set of rod bearings.
11-27-2009, 10:57 PM
#33
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I removed the intake resonance flap , as it wasnt needed for power. (Usable power for racing). we dont know how it will work, but even on the 3.2 liter BMWs with vanos removed as well (similar to some of the effectiveness of the flappy, in our cars) they gained HUGE hp and they have similar sized 4 valve heads and ports. If you look at Andersons curves, you can see how the flow is optimized even at the midrange and upward . You can even do the air flow guestimation, to see how that will effect even a 20% smaller engine displacement.
I cant say for sure, but I bet the gains are still substantial, even on a 5 liter. we have never seen one tested, so this might be a good test to see one way or another.
Mk
.
I cant say for sure, but I bet the gains are still substantial, even on a 5 liter. we have never seen one tested, so this might be a good test to see one way or another.
Mk
.
On a basically stock 5 liter 32 valve the carbon intake should be less efficient in the low midrange and lacks the tuning of the resonance flap of the stock S-4 intake. The Threshie intake made a difference on highly modified stroker engines which failed to make much more power with better headers, bigger valves , porting etc and the last step was removing the restriction of the STOCK intake..... Lacking such a large and efficient air pump (6.5 liters) the stock intake probably was designed by Porsche to work pretty well....if they could have easily found another 20-25 hp while they were improving upon the 85-86 32 valve intake one might think they would have done it. The stock intake costs thousands of dollars as it is ! So yes I think big camshafts will be the next item on your wish list.....followed by a set of rod bearings.
11-27-2009, 11:47 PM
#34
Can you tell me what is the diameter of the intake trumpet? That is where the bell mouth ends and the runner starts. I am trying to do some calcs for my engine and I am getting around 54 to 60 mm internal diameter.
Thanks
Greg
Thanks
Greg
11-27-2009, 11:50 PM
#35
Drifting
Last time I spoke with carl at 928motorsports who bought much of threshies goodies, didn't buy the cf intake molds. I email phil thresshie and he could still make(had the molds) the intake if someone needed.
andy
andy
11-28-2009, 03:16 PM
#37
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Porting is enlarging the diameter of the passages in the head that lead to the valves. The result is lower velocity less efficient at lower RPM but the capacity to flow MORE at high RPM.
11-29-2009, 11:29 PM
#43
Nordschleife Master
On a basically stock 5 liter 32 valve the carbon intake should be less efficient in the low midrange and lacks the tuning of the resonance flap of the stock S-4 intake. The Threshie intake made a difference on highly modified stroker engines which failed to make much more power with better headers, bigger valves , porting etc and the last step was removing the restriction of the STOCK intake..... Lacking such a large and efficient air pump (6.5 liters) the stock intake probably was designed by Porsche to work pretty well....if they could have easily found another 20-25 hp while they were improving upon the 85-86 32 valve intake one might think they would have done it. The stock intake costs thousands of dollars as it is ! So yes I think big camshafts will be the next item on your wish list.....followed by a set of rod bearings.
The S4 intake manifold is a design error. One can see what they were thinking, but it's just not the right way to do it.
One of the goals of the original designers was to group the pulses such that both banks have equally spaced pulses. That's nice, but the cost of the contortionist pipes far outweighs the benefit. When costs are compared to benefits, this design falls firmly into the error category. Here's a better way to do it, ignore the minor pulse overlap and run a dual plenum system with a balance pipe and straightest possible pipes:
The second error was how they did the variable geometry system. They switch between a Helmholtz resonator and a single plenum open pipe system. Ok, that's one way to do it, just not even close to the best way. A better way to do this is simply to use flaps to change the intake manifold runner length. Again, a design error that has rarely been repeated in other cars since then. Here's an example of the better:
There's dyno result database with 4v modular Ford intake manifold tests out there. The engine is similar enough to the 928 S4 that the results are highly relevant. Browsing thru that database makes it clear that the Porsche designers took a couple of wrong turns with that manifold. The simplest dual plenum manifold in the first picture basically gives the best torque curve for any application, as long as the runner length and diameter is selected correctly for the application.
11-30-2009, 12:30 AM
#44
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So the fact that Porsche asks for a lot $$$ for a stock S4 intake manifold is a good indication of it's inherent value? Really? If so, does it change your assessment in any way that I just picked a used one on ebay in a very good condition for about $90?
The S4 intake manifold is a design error. One can see what they were thinking, but it's just not the right way to do it.
One of the goals of the original designers was to group the pulses such that both banks have equally spaced pulses. That's nice, but the cost of the contortionist pipes far outweighs the benefit. When costs are compared to benefits, this design falls firmly into the error category. Here's a better way to do it, ignore the minor pulse overlap and run a dual plenum system with a balance pipe and straightest possible pipes:
The second error was how they did the variable geometry system. They switch between a Helmholtz resonator and a single plenum open pipe system. Ok, that's one way to do it, just not even close to the best way. A better way to do this is simply to use flaps to change the intake manifold runner length. Again, a design error that has rarely been repeated in other cars since then. Here's an example of the better:
There's dyno result database with 4v modular Ford intake manifold tests out there. The engine is similar enough to the 928 S4 that the results are highly relevant. Browsing thru that database makes it clear that the Porsche designers took a couple of wrong turns with that manifold. The simplest dual plenum manifold in the first picture basically gives the best torque curve for any application, as long as the runner length and diameter is selected correctly for the application.
The S4 intake manifold is a design error. One can see what they were thinking, but it's just not the right way to do it.
One of the goals of the original designers was to group the pulses such that both banks have equally spaced pulses. That's nice, but the cost of the contortionist pipes far outweighs the benefit. When costs are compared to benefits, this design falls firmly into the error category. Here's a better way to do it, ignore the minor pulse overlap and run a dual plenum system with a balance pipe and straightest possible pipes:
The second error was how they did the variable geometry system. They switch between a Helmholtz resonator and a single plenum open pipe system. Ok, that's one way to do it, just not even close to the best way. A better way to do this is simply to use flaps to change the intake manifold runner length. Again, a design error that has rarely been repeated in other cars since then. Here's an example of the better:
There's dyno result database with 4v modular Ford intake manifold tests out there. The engine is similar enough to the 928 S4 that the results are highly relevant. Browsing thru that database makes it clear that the Porsche designers took a couple of wrong turns with that manifold. The simplest dual plenum manifold in the first picture basically gives the best torque curve for any application, as long as the runner length and diameter is selected correctly for the application.
11-30-2009, 04:00 PM
#45
Chronic Tool Dropper
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The throttle plates at the top of the runner inthe lower picture is interesting. Pretty much makes the shape of the bell non-critical. It would be very interesting to see what sits on top of that throttle assembly. IIRC it's a plastic cover with internal runners. If done correctly, the pulse relationship between the middle cylinders could be adjusted with the runner routing in the cover. Cool stuff!