New 4 V head flow figures
03-23-2012, 11:23 PM
#91
When you are shoving the air in at 25psi, you can do with ports a quart of that size to
Get 800
Get 800
Just thought I would post a pic of how big the ports have to be to get to over 800 HP.
The above heads are the same size as the heads I had access to, they have bigger ports than that of the 928, the other ports as you can see are a fair bit bigger again and that is how they come from the factory. The size of the port does correlate to the flow numbers but more the velocity side of the equation.
The above heads are the same size as the heads I had access to, they have bigger ports than that of the 928, the other ports as you can see are a fair bit bigger again and that is how they come from the factory. The size of the port does correlate to the flow numbers but more the velocity side of the equation.
04-03-2012, 06:56 AM
#92
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I mentioned earlier that I would post some pics on piston guided rods, I thought I would also post some details on the technical details of good rod design.
You can see below just how close they have to get the bolt to the bearing housing to stop the distortion. You can also see that the saw tooth profile cap rod has an improved bolt location of the other rod even though this has been known for a long time and the rods come from the same manufacturer. It is also interesting to note that when both bolts are done up both bolts will be distorted, they do not even themselves out. This is the reason this design had to be implemented. It is also interesting that to get the bolts as close as possible you need to pin the rods as above.
You can see here how robust the caps and shaft is on these rods, that is designed to combat what is happening in the above diagram. For reference the rods use a crank pin that is 1.888" or 48 mm in diameter and a 20.3 mm wide bearing. You can purchase Honda 48mm diameter bearings that are around 23 mm wide which would be very good for street cars however these rods won't accept them, nor are they rods for street cars.
This pic shows the various methods that can be employed to guide the pistons at the small ends, note there is a decent amount of width to the surface which runs against the piston, a bit more than 3 mm and on the black rod this is DLC coated to reduce friction further, although the friction is already reduced with the piston guided setup as it is only pendulum friction versus rotational friction. The rod without EDM drilling requires a recess for pin lubrication as it has no forced oiling. This system doesn't work as well as the forced oiling in terms of cooling.
This pic below shows the relative widths of the piston pins, I was wondering if somebody would be so good to post the width of the standard pin. I am aware the diameter is 24 mm, out of interest, the details of these pins are 99 grams each, the larger pin is 2.25" wide 22 mm diameter, the shorter 2" and 21 mm diameter. Both made from C-350 Steel. Which is an amazing material itself. They needs to be a copper beryllium bush inserted into the small end for street longevity. All though I am informed some motorcycles don't have copper bushes and run steel on steel.
Given these PGRs run very small radial clearances, you can see why they require such robust big ends, despite the eccentricity of the bearings there is always a chance of pinching the crank pin as described in one of the above pics. Notice the heavy/deep ribbing around the rod cap. Despite this these rods are not heavy, they are around 10% heavier than a Ti equivalent with better fatigue and handling properties.
You can see below just how close they have to get the bolt to the bearing housing to stop the distortion. You can also see that the saw tooth profile cap rod has an improved bolt location of the other rod even though this has been known for a long time and the rods come from the same manufacturer. It is also interesting to note that when both bolts are done up both bolts will be distorted, they do not even themselves out. This is the reason this design had to be implemented. It is also interesting that to get the bolts as close as possible you need to pin the rods as above.
You can see here how robust the caps and shaft is on these rods, that is designed to combat what is happening in the above diagram. For reference the rods use a crank pin that is 1.888" or 48 mm in diameter and a 20.3 mm wide bearing. You can purchase Honda 48mm diameter bearings that are around 23 mm wide which would be very good for street cars however these rods won't accept them, nor are they rods for street cars.
This pic shows the various methods that can be employed to guide the pistons at the small ends, note there is a decent amount of width to the surface which runs against the piston, a bit more than 3 mm and on the black rod this is DLC coated to reduce friction further, although the friction is already reduced with the piston guided setup as it is only pendulum friction versus rotational friction. The rod without EDM drilling requires a recess for pin lubrication as it has no forced oiling. This system doesn't work as well as the forced oiling in terms of cooling.
This pic below shows the relative widths of the piston pins, I was wondering if somebody would be so good to post the width of the standard pin. I am aware the diameter is 24 mm, out of interest, the details of these pins are 99 grams each, the larger pin is 2.25" wide 22 mm diameter, the shorter 2" and 21 mm diameter. Both made from C-350 Steel. Which is an amazing material itself. They needs to be a copper beryllium bush inserted into the small end for street longevity. All though I am informed some motorcycles don't have copper bushes and run steel on steel.
Given these PGRs run very small radial clearances, you can see why they require such robust big ends, despite the eccentricity of the bearings there is always a chance of pinching the crank pin as described in one of the above pics. Notice the heavy/deep ribbing around the rod cap. Despite this these rods are not heavy, they are around 10% heavier than a Ti equivalent with better fatigue and handling properties.
Last edited by slate blue; 04-03-2012 at 09:13 AM. Reason: More detail
04-03-2012, 08:57 AM
#93
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A standard 928 S4 wrist pin is 65mm (2.559") long, outer diameter 24mm (.945"), inner diameter 14mm (.551"), wall thickness 5mm (.1969") and weight 153 grams.
Ake
Ake
