The "Little Old Lady Sunday Driver" Syndrome: what damage is done by "easy" driving ?
12-01-2015, 01:31 PM
#31
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from the 1980 owners manual.... for smooth shifting observe the following shift points ...... minimum upshifting points. 1st to 2nd 1900 RPM; 2nd to 3rd 2300 RPM ; 3rd to 4th 2700 RPM ; 4th to 5th 2400 RPM ......
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
12-01-2015, 01:36 PM
#32
from the 1980 owners manual.... for smooth shifting observe the following shift points ...... minimum upshifting points. 1st to 2nd 1900 RPM; 2nd to 3rd 2300 RPM ; 3rd to 4th 2700 RPM ; 4th to 5th 2400 RPM ......
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
12-01-2015, 02:07 PM
#33
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The available torque from the engine, graphed in a handy chart in your Owner's Manual, shows that at much lower RPM's the torque falls off. But by 1900 RPM, you are well into the relatively flat section of the torque 'curve'. Regardless, so long as there is no detonation, the engine self-regulates the pressure put on the pistons and rods, and on the rotating bits.
By around 1200 RPM on my car, I have full indicated oil pressure even on the hottest days, so no worry about squeezing the oil film in rod bearings at lower engine RPM's. Ever wonder why your car has relatively fabulous oil pressure at relatively low engine speeds? Could it be by design?
12-01-2015, 02:38 PM
#34
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from the 1980 owners manual.... for smooth shifting observe the following shift points ...... minimum upshifting points. 1st to 2nd 1900 RPM; 2nd to 3rd 2300 RPM ; 3rd to 4th 2700 RPM ; 4th to 5th 2400 RPM ......
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
These will differ somewhat with the slightly varied gearing of different years but point is anytime you hit 2,700 RPM in any gear it is O K to shift to a higher gear and 1st to second could be as low as 1,900 RPM.
The urban myth about the need to keep the RPMs up in a Porsche comes from the 356 years where some racing engines were fitted with roller bearings on the cranks low RPM operation for extended periods of time were very hard on roller bearings and those engines had problems but were very efficient due to the very low friction. That started the belief that Porsche engines must be kept at high RPM....The 911 owners embraced that thinking without question even though it has NOTHING to do with their engine design but they loved the sound
Porsche when they were deciding what engine to use in the 928 considered a V-6 for a while but opted to design a V-8 with a displacement between 4 to 5 liters so it made power at LOWER RPMs to not have to spun up as high, make as much noise to move the car around. Be able to cruise at 65 MPH at around 2,500 RPM . Prototype 5.0 engines were tried with carbs (the CIS not being ready) and probably were making good power but the original "energy crisis" lead Porsche to downsize to the 4.5 liter 220-230hp.
That was a huge mistake in my opinion. Had the built it with a 5 liter with 320 -340 HP it would NEVER have been considered a heavy gran touring cruiser but truly would have been a SUPERCAR in 1977. It was not that it weighed too much but that it was underpowered from what it so easily could have been. The 4.7 300hp S in the European 1980 was too little too late to really change the motoring communities image of the 928.
12-01-2015, 02:43 PM
#35
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12-01-2015, 04:38 PM
#36
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jim... is "lugging around" meaning starting out from a stoplight? you really need to think a little more on these responses. whats up with you lately.. wake up on the wrong side of your 928 in the morning?
lower power at the low RPM range, and if you are going to drag race, you will be dumping the clutch at 4500 or higher more than likely. if you pull away from the stop light with low RPM, thats fine . its how its done . you know i was talking about cruise power settings and RPM.
we drag race and you run your truck anyway you want. I'll dump the clutch at 4500rpm and you will be gone!
ever watch a world challenge race? ever been in one Jim?? oh, you haven't.. let me tell you .... nothing more exhilarating than 30 cars running at the rev limiter at idle waiting for the lights to go out!
12-01-2015, 04:53 PM
#37
I watched my kids play a racing game on xbox.
12-01-2015, 06:40 PM
#38
Isn't carbon buildup caused more by running at partial throttle all the time? Need to activate the WOT switch once in a while, to make it run more rich and wash away the deposits. I don't see why the revs would matter.
12-01-2015, 06:54 PM
#39
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revs matter for the reason of combustion completeness. generally, the higher the Revs, the hotter and more complete the burn due to higher velocities of the mass flow which creates better atomization of the fuel in the air as it enters the cylinders. more rich doesnt creat a "washing "of the carbon away.. thats a temp and pressure/flow thing. very rich and very low RPM , even full throttle will tend to make carbon build up everywhere.
12-01-2015, 07:10 PM
#41
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---
I borescoped the cylinders and pistons when Rob & I did the intake refresh on my car. Separately, he was looking down through an intake port while fishing for a balistic injector connector clip, and pronounced the internals as good. I drive the car gently, and it doesn't seem to mind it too much. I only recently pulled in some on the TV cable to tighten the shifting a little. Previously it was just bumping gear to gear in traffic with the pedal barely off idle.
'Traffic' at the new digs is waiting for a few cars when the local school gets out. Nothing close to what the car previously enjoyed in the L.A. basin. So it's OK to let the car run up a little more before shifting up.
12-01-2015, 07:42 PM
#42
Mark:
Now, THAT'S funny ! ! ! !
Now, THAT'S funny ! ! ! !
12-02-2015, 12:06 PM
#45
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when you hit 2,400 in 4th quite alright to shift up to 5th and drop the RPM down to about 1,800 ! Porsche designed it as a high torque(for them) low RPM engine.
The anecdotal comments about carbon in engines typically goes something like this...Pulled the heads saw carbon so engine MUST have been putted around bad science at best.
Obviously when you wish to accelerate quickly, downshift !!! That is why God created manual transmissions. And why Roger boxes are the work of the Devil.....but at least they automatically downshift