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Old 12-20-2011, 09:35 AM
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Enlighted me on piston speed?

http://www.mustangsandmore.com/ubb/S...stonspeed.html

If found that link in read some reading, obviously piston speed (ps) is not the only factor. How much bs is this? What are some real figures to consider as when it comes to piston speed? Something more accurate?

Example my 327 at 6000rpm is at 3250 FPM (feet per min)
My b16a pr3 quench head honda (1.6) at the daily (almost every shift) 8500rpm i hit my piston speed would be at 4316.929 FPM with a 77.4mm bore (about 3 inches). My bottom end is stock with a fully counterweighted high alloy steel forged crankshaft and forged high alloy steel rods with large bolts. (all b16a blocks had this factory)

Would this be the reason then that the honda was capable of having such a high factory piston speed with little issues? The 8500rpm redline is factory btw. The motor is currently in my 2000 civic si.

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Old 12-20-2011, 10:07 AM
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Very briefly: The stroke influences piston speed, not the bore. The bore will contribute to frictional losses.

The Honda will be capable of high piston speeds due to the rings (design/material, thinner, lighter weight), along w/the diameters of the rod and crank journals (smaller journal diameters will have less bearing speed than larger diameters for a given RPM).
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Old 12-20-2011, 12:18 PM
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Quote:
Originally Posted by blight
http://www.mustangsandmore.com/ubb/S...stonspeed.html

If found that link in read some reading, obviously piston speed (ps) is not the only factor. How much bs is this? What are some real figures to consider as when it comes to piston speed? Something more accurate?

Example my 327 at 6000rpm is at 3250 FPM (feet per min)
My b16a pr3 quench head honda (1.6) at the daily (almost every shift) 8500rpm i hit my piston speed would be at 4316.929 FPM with a 77.4mm bore (about 3 inches). My bottom end is stock with a fully counterweighted high alloy steel forged crankshaft and forged high alloy steel rods with large bolts. (all b16a blocks had this factory)

Would this be the reason then that the honda was capable of having such a high factory piston speed with little issues? The 8500rpm redline is factory btw. The motor is currently in my 2000 civic si.
The link quotes a pretty old text, technology has moved a lot in the past several years being driven by government regulations for emissions and mileage on one hand the the fact that the factory's know that performance sells cars. Modern electronic engine management systems let us have both conformance to regulation and performance. The best off the showroom performance cars of the 1960's would be smoked by the run of the mill production car of today not to mention what would happen against a performance engine of today.

Piston speed that is survivable is highly dependent upon the material of the piston, its clearance to the bore, the accuracy of the machining and finish of both the bore and the piston, and the ring package in the material type, coatings, finish, size/weight, and tension.

For your 327 a factory replacement cast piston with wide and heavy rings would be restricted to about 3700 Feet Per Minute before failure. This would be something like a 2618 low alloy material. It would be moderately strong and show reasonable ductility but the lack of strength pushes the rings to be larger to spread the loads over more area in the ring groove to get adequate service wear from the piston. The down side of this design combination is that the when the piston reverses direction the ring also moves in the opposite direction either in total or in twist. This constant snapping back and forth in the groove results in wear on the groove to where eventually the ring can neither seal the groove nor the wall, it needs to do both at the same time. An advantage of these low silicon alloys is that when you do get failure it tends to be more graceful, admittedly the lower strength alloy will fail earlier but because of the greater ductility will fail more gracefully in that it will tend to stay on the pin and rod.

If you move up to a forged 4032 alloy strength is increased but ductility is reduced. Pistons of this type will take a lot more abuse but when they fail it is by busting up leaving the pin and rod unsupported and usually smashed through the cylinder wall. These pistons can be run with less clearance which offers greater ring stabilization against the cylinder wall and to the ring groove. Being a stronger more wear resistant material, the rings can be smaller as the groove will tolerate greater loading from the ring without undue wear. With the advantages of this type material, the piston speed can be picked up a lot into the range of 6 to 7 thousand feet per minute, which is where the typical Cup V8 is running. Certainly running at these speeds takes a whole new approach to the engine, This isn't something you're going to do with a built up junk yard block, cast crank, and powder forged rods.

There of course are other materials and process that can be employed but this is the stuff books are about as this information gets voluminous very fast.

The Civic b16a gets to these high piston speeds by the use of better piston material and process, along with the better bottom end and to some extent smaller and few cylinders. The large V8 is a very difficult engine to balance and the crankshaft is trying to do odd things because of the way the factories go at balancing the center two throws without counterweights. Doing this balances the weights of the 180 degree separated piston, rod assembly but results in an offset moment through the center bearing that wants to bend the shaft between the second and forth mains. This is why 4 bolt blocks are on the 3 center mains and not the ends, though you will find Cup engines with 4 bolts on everything. to some extent this is also why there are larger counterweights on the outer ends of the shaft as a means of pulling the shaft out straight along its length. The old Ford Y block couterweighted the inboard crank throws to neutralize this bending moment on the crank. But this adds a lot of weight. In-spite of this weight penalty many current extreme circle and road track competition V8's use custom shafts with the counterweighting at the center throws. This is usually not done on drag engines where the need for a few seconds of maximum acceleration drives minimizing the weight of and on the crankshaft as opposed to many minutes to hours of high RPM, high power extraction where absolute acceleration is of less importance and surviving a long time between maintenance cycles is. So when you engineer performance engines, you often find the end use puts you on very different technical solution courses for an engine that outwardly looks very much the same between a drag or circle/road track engine.

Bogie
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Old 12-21-2011, 05:39 AM
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Well that is a ton of awesome info bogie! Its much appreciated. The 327 I am working with currently has 40 over flat tops. I need to check the bottom if they are forged or not. I imagine they are its an Owen's boat motor for a yacht. Its also a small journal factory forged crank. I should never see past 6500rpm. At 6000rpm (aerodynamics forgiving) in fourth gear I should be doing about 184 mph so no need to really. The car is built for B.I.R. in MN. The car is 2800 pounds, and has a Quaif 3.545 rear.

The cam
http://www.compcams.com/Company/CC/c...?csid=230&sb=0

The intake
http://www.jegs.com/i/Weiand/925/7547-1/10002/-1

The carb
800 holly double pumper (might be overkill but not by much for my power goal)

I am having a difficult time choosing a head. I am not a brand name guy in the slightest. I am using a desktop dynometer to give me a rough estimate on what things will be like at were they will be at. I am back and forth with iron and aluminum for one. I have been told that anything higher than 9.5:1 for iron will be asking for detonation on the 93 octane. Seeing that I would like to be at about 10:1 or 10.5:1ish area that would lean me toward the aluminum. Albeit I just find the jump in price to be pretty ridiculous. The amount of time and money it requires for them to design a head is so minimal now'a days (the computer aided design and the plastic print out machines to flow test it before production) its difficult enough to justify buying aftermarket heads rather than doing a set of factory heads. I also don't want to loose too much velocity but want to get my HORSE POWER goal (tq is not a concern of mine) so the largest intake side I can "get away with" with the most reasonable flow rates for the buck would be what I am looking for. I figure nothing less than 180 but nothing higher than 200cc. My GOAL is about 490 crank to try to get to 400 WHP if possible figuring about 18 percent loss in the auto trans and differential to wheels.

Much appreciated bogie, for the great info by the way. There was somethings in there I have yet to read about.
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Old 12-21-2011, 11:25 AM
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Quote:
Originally Posted by blight
Well that is a ton of awesome info bogie! Its much appreciated. The 327 I am working with currently has 40 over flat tops. I need to check the bottom if they are forged or not. I imagine they are its an Owen's boat motor for a yacht. Its also a small journal factory forged crank. I should never see past 6500rpm. At 6000rpm (aerodynamics forgiving) in fourth gear I should be doing about 184 mph so no need to really. The car is built for B.I.R. in MN. The car is 2800 pounds, and has a Quaif 3.545 rear.

The cam
http://www.compcams.com/Company/CC/c...?csid=230&sb=0

The intake
http://www.jegs.com/i/Weiand/925/7547-1/10002/-1

The carb
800 holly double pumper (might be overkill but not by much for my power goal)

I am having a difficult time choosing a head. I am not a brand name guy in the slightest. I am using a desktop dynometer to give me a rough estimate on what things will be like at were they will be at. I am back and forth with iron and aluminum for one. I have been told that anything higher than 9.5:1 for iron will be asking for detonation on the 93 octane. Seeing that I would like to be at about 10:1 or 10.5:1ish area that would lean me toward the aluminum. Albeit I just find the jump in price to be pretty ridiculous. The amount of time and money it requires for them to design a head is so minimal now'a days (the computer aided design and the plastic print out machines to flow test it before production) its difficult enough to justify buying aftermarket heads rather than doing a set of factory heads. I also don't want to loose too much velocity but want to get my HORSE POWER goal (tq is not a concern of mine) so the largest intake side I can "get away with" with the most reasonable flow rates for the buck would be what I am looking for. I figure nothing less than 180 but nothing higher than 200cc. My GOAL is about 490 crank to try to get to 400 WHP if possible figuring about 18 percent loss in the auto trans and differential to wheels.

Much appreciated bogie, for the great info by the way. There was somethings in there I have yet to read about.
I'm just kind of whipping through stuff at the moment and havent followed your cam link.

The continuing argument between iron and aluminum is that aluminum conducts heat faster than iron which on one hand theoretically reduces power potential but on the other allows more compression, which can, does, and perhaps exceeds the thermal efficiency gain of cast iron.

My approach to this question is largely driven by the Dynamic Compression Ratio Calculation for which you need the cam, stroke and rod length specs. Where the DCR starts needing Static Compression Ratios (SCR) getting over 10 to 1 I look to aluminum because you can play more games with it. That's to say you can safely operate at higher coolant temps than cast iron without risking cracking the material so that can be used to drive the thermal efficiency up. Or you can cool it down a bit and jack the static compression up to recover a lower DCR. There are obviously more games that can be played for both iron and aluminum but this is a teaser as to how I think about these things.

To pull nearly 500 HP from a 327 is going to take a lot of cam and compression; plus quite a few revs which is going to drive the bottom end build. For heads on a 327 I'd be looking at AFRs 180 or 190 cc port. They flow almost equally, the 190 small bit more but the 180 should kick the velocity up a little which will put a little more bottom end kick into a big cammed engine without hardly any top end compromise to ultimate power.

Bogie
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