Eary Bay - Top Speed?

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Hippie
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Re: Eary Bay - Top Speed?

Post by Hippie » Sun Apr 03, 2011 6:20 pm

chitwnvw wrote:Never hit more than 77 or 78 in any of my buses, pedal to the floor...unless it was down hill or had a good tailwind.
It's tough to get those extra mph above 70-75. All the air and mechanical drag increases as a square of increased velocity.
I doubt any bay can ever get to a true 102 with a stock engine. No offense Colin. My truck "chips out" at 100 (102 indicated) with better aerodynamics and 159 net HP, and barely climbs to that before the engine control module cancels further acceleration.
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Re: Eary Bay - Top Speed?

Post by hambone » Mon Apr 04, 2011 3:34 pm

Installed a brand new Sunpro Mini tachometer from Autozone, $30 not too bad. Snap-On is the parent company.
SO, I see that I like to cruise around 2,400 RPM around town, shifting at 3,000. Seems much lower RPMs than highway speeds, is that desirable? These are far lower RPM values than I expected. Perhaps some soundproofing is in order.
It seems like a useful gage, perhaps more useful than the speedometer.
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Re: Eary Bay - Top Speed?

Post by chitwnvw » Mon Apr 04, 2011 5:45 pm

Seems like a bit low, but I don't know the T1. Seems like the 1.7 T4 enjoys 3k - 4k. I guess you need to check the specs for you particular setup.

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Re: Eary Bay - Top Speed?

Post by Amskeptic » Mon Apr 04, 2011 9:47 pm

hambone wrote:Installed a brand new Sunpro Mini tachometer from Autozone, $30 not too bad. Snap-On is the parent company.
SO, I see that I like to cruise around 2,400 RPM around town, shifting at 3,000. Seems much lower RPMs than highway speeds, is that desirable? These are far lower RPM values than I expected. Perhaps some soundproofing is in order.
It seems like a useful gage, perhaps more useful than the speedometer.
If you shift at 3,000 rpm from 1st to 2nd, you will be chronically pissing off the main bearings and piston skirts. My minimum upshift arrival rpm in 2nd is 1,700 rpm, in 3rd 2,000 rpm and 4th 2,500 under modest acceleration. That means I have to shift near 4,000 rpm in 1st. The higher gears are more closely spaced so you do not have to wind out so far. If you want to utilize your engine's available power, then there is no better 3/4 shift point than 45 mph early, 50-55 late.
Colin
(Hippie, I was offering theoretical gear ratio top speed @ redline. There is no way that a bus can power itself to those speeds)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Hippie
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Re: Eary Bay - Top Speed?

Post by Hippie » Tue Apr 05, 2011 5:25 am

Amskeptic wrote:(Hippie, I was offering theoretical gear ratio top speed @ redline. There is no way that a bus can power itself to those speeds)
Got ya.
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Re: Eary Bay - Top Speed?

Post by chitwnvw » Tue Apr 05, 2011 6:16 am

Amskeptic wrote:If you want to utilize your engine's available power, then there is no better 3/4 shift point than 45 mph early, 50-55 late.
Perfect for getting up to speed on the freeway on-ramp.

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Re: Eary Bay - Top Speed?

Post by Amskeptic » Tue Apr 05, 2011 9:05 am

chitwnvw wrote:
Amskeptic wrote:If you want to utilize your engine's available power, then there is no better 3/4 shift point than 45 mph early, 50-55 late.
Perfect for getting up to speed on the freeway on-ramp.
Borne out by the crafty German engineers who designed the gear ratios to swap the horsepower peak of the lower gear for the torque peak of the next gear at those shift points.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Eary Bay - Top Speed?

Post by hambone » Tue Apr 05, 2011 11:43 am

Gotcha, you want to shift so you arrive around 2000 RPM in the next gear. It's a weird backwards way of looking it at, being concerned with the arrival. I guess I've been doing it subconsciously, but a bit too low. I should also verify that the tach is accurate.

Does all that high revving around town contribute to poor fuel economy and accelerated engine wear? When puttering along at 35 on a flat, sometimes I put it in 4th for a gentle cruise. It doesn't seem like the engine minds. No lugging though.
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Re: Eary Bay - Top Speed?

Post by sped372 » Tue Apr 05, 2011 12:27 pm

Work is work. What does the work? Burning fuel (potential energy)! Theoretically, if you're doing the same amount of work, you'd use the same amount of energy. It shouldn't matter which gear you're in... less torque x more rpms = more torque x less rpms = same amount of work.

If you weren't doing the exact same amount of work (moving the bus along) you'd be speeding up or slowing down.

One simplification here is internal friction. As engine rpms increase the friction within the engine also increases - so, in addition to moving the bus the engine is also doing more work to overcome friction at higher rpms. It's a small piece of the overall total, though.

Thermodynamics!

You're within the range shown in the '70 owners manual:
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Re: Eary Bay - Top Speed?

Post by hambone » Tue Apr 05, 2011 1:11 pm

More great information! SO I've been driving for fuel economy, but possibly compromising the engine in the process. I'll kick up those RPMs.
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Re: Eary Bay - Top Speed?

Post by Hippie » Tue Apr 05, 2011 7:00 pm

sped372 wrote:Work is work. What does the work? Burning fuel (potential energy)! Theoretically, if you're doing the same amount of work, you'd use the same amount of energy. It shouldn't matter which gear you're in... less torque x more rpms = more torque x less rpms = same amount of work.
But at higher RPM, there are more bangs per second = more power in, more power out. At some point there is a cross over of diminishing returns on bangs for buck and internal friction, but beyond that, torque is the transmission's job. Must not confuse wheel torque on the other side of the gears with engine output.
The engine works hardest with the throttle wide open and at it's own peak HP RPM.
hambone wrote:More great information! SO I've been driving for fuel economy, but possibly compromising the engine in the process. I'll kick up those RPMs.
Yes, you want the bearings riding on a hydrodynamic wedge of oil that forms best at the somewhat higher RPMs so that the jam-bam of the piston thrusts don't push through it like when lugging along with big throttle and low RPM.
Engine oil pressure doesn't keep the metal from touching the metal. The wedge does. It surfs the oil film.
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Re: Eary Bay - Top Speed?

Post by sped372 » Wed Apr 06, 2011 6:39 am

Hippie wrote:
sped372 wrote:Work is work. What does the work? Burning fuel (potential energy)! Theoretically, if you're doing the same amount of work, you'd use the same amount of energy. It shouldn't matter which gear you're in... less torque x more rpms = more torque x less rpms = same amount of work.
But at higher RPM, there are more bangs per second = more power in, more power out.
Not quite... think about it. The end product is moving the bus down the road. Let's arbitrarily choose a vehicle speed and work from that... say 35mph? If you're going down the road at a constant 35mph you can assume that you require a constant amount of power (work) to get the job done. If the engine was producing more power/work the bus would speed up... less power, it slows down. You're overcoming air resistance, rolling resistance, and all those other little parasitic items that keep perpetual motion machines out of our reach. Lets just arbitrarily guess that a bus needs 15hp to drive at a constant 35mph.

Now, it doesn't matter what gear you're in... that has no effect on all those resistances you're overcoming (except the ones internal to the engine that are rpm dependent). In fact, you don't even need to be in any gear, or have the engine running! The fact remains that somehow, you need to come up with 15hp to keep that bus moving at 35mph. Well, we're lucky and we have an engine and a transmission so we have options. Let's see, I could get my 15hp in third gear... so I'd need a certain amount of torque (from the engine) at a certain rpm, through the transmission, to the wheels to get me 15hp. Or, I could go in fourth gear, I'd need more torque from the engine, but at a lower rpm, through the transmission, to the wheels, to get me the same 15hp. If I didn't get 15hp I'd speed up (or slow down). Make sense?

Just because there's more bangs doesn't mean you're producing more power. That's what the throttle is there for. Each individual bang at a higher rpm is producing less power so that the cumulative total is the same. The engine has the potential to create a certain amount of power/work... you use the throttle to dial it back to where you need it.

Wheel torque is completely dependent on engine torque, the transmission is just a multiplier - it doesn't "create" any torque.

If we continue with the thought process, you could conclude that if you were able to roll down a hill in neutral at a steady 35mph you would be reducing your elevation at a rate of 15hp. Height is one form of potential energy. Fun stuff to ponder while your brakes are fading. :king:
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Re: Eary Bay - Top Speed?

Post by Amskeptic » Wed Apr 06, 2011 7:36 am

sped372 wrote:
Hippie wrote:
sped372 wrote:Work is work. What does the work? Burning fuel (potential energy)! Theoretically, if you're doing the same amount of work, you'd use the same amount of energy. It shouldn't matter which gear you're in... less torque x more rpms = more torque x less rpms = same amount of work.
But at higher RPM, there are more bangs per second = more power in, more power out.
Not quite... think about it. The end product is moving the bus down the road. Let's arbitrarily choose a vehicle speed and work from that... say 35mph? If you're going down the road at a constant 35mph you can assume that you require a constant amount of power (work) to get the job done. If the engine was producing more power/work the bus would speed up... less power, it slows down. You're overcoming air resistance, rolling resistance, and all those other little parasitic items that keep perpetual motion machines out of our reach. Lets just arbitrarily guess that a bus needs 15hp to drive at a constant 35mph.

Now, it doesn't matter what gear you're in... that has no effect on all those resistances you're overcoming (except the ones internal to the engine that are rpm dependent). In fact, you don't even need to be in any gear, or have the engine running! The fact remains that somehow, you need to come up with 15hp to keep that bus moving at 35mph. Well, we're lucky and we have an engine and a transmission so we have options. Let's see, I could get my 15hp in third gear... so I'd need a certain amount of torque (from the engine) at a certain rpm, through the transmission, to the wheels to get me 15hp. Or, I could go in fourth gear, I'd need more torque from the engine, but at a lower rpm, through the transmission, to the wheels, to get me the same 15hp. If I didn't get 15hp I'd speed up (or slow down). Make sense?

Just because there's more bangs doesn't mean you're producing more power. That's what the throttle is there for. Each individual bang at a higher rpm is producing less power so that the cumulative total is the same. The engine has the potential to create a certain amount of power/work... you use the throttle to dial it back to where you need it.

Wheel torque is completely dependent on engine torque, the transmission is just a multiplier - it doesn't "create" any torque.

If we continue with the thought process, you could conclude that if you were able to roll down a hill in neutral at a steady 35mph you would be reducing your elevation at a rate of 15hp. Height is one form of potential energy. Fun stuff to ponder while your brakes are fading. :king:
You are indeed having fun in a theoretical pondering sort of way. The above highlight is where I do not have enough information to agree or disagree. The torque peak of any engine is where the bang is the biggest. VW's generally hit the torque peak at 3,000 rpm. The cumulative total of effort (torque) + work (rpm) intersects at the horsepower peak where a VW's torque is dropping off but the work getting done is increasing. This is about 4,400 rpm for the Type 1 engine.

Experience is another sort of fun. If you look at a 100 year-old coot driving a pick-up truck down a dirt road, you will see the experiential melding with the theoretical. He is trying to keep that old cast-iron water-cooled engine running forever. He barely ever sees 2,000 rpm as he gets it in high gear as soon as possible. He also disdains Porsche engineering . . .

We have Porsche engineering. We do. The benefits of low RPM full throttle (fuel economy, believe it or not) must be balanced against very light engine materials like aluminum and magnesium that are cooled by air only?? Do not underestimate this fact. Porsche engineering has always used high rpm to get the work down because you can use lighter materials and cool it with a hurricane of blowing air. VW engines get hot and pissed off below 2,000 rpm as you hammer the magnesium and aluminum. We see it in pounded main bearing saddles, pounded thrust surfaces, caved cylinder spigots, and cylinder imprinted cylinder heads. Do not screw around with hot magnesium and aluminum trying to "improve" theoretical fuel economy with "reduced friction" low rpms!

Like Hambone, I will putter around town in 4th gear at 30 mph if I am barely touching the gas. But if I am asking that poor little engine to haul the big bus onto an interstate, I am going to use rpm-supplied horsepower to make sure that I do not complete the shift at below the torque peak in the next gear. This is kindest to that brilliant engineering, especially on a 110* day.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Eary Bay - Top Speed?

Post by Hippie » Wed Apr 06, 2011 8:57 am

sped372 wrote:
Hippie wrote:
sped372 wrote:Work is work. What does the work? Burning fuel (potential energy)! Theoretically, if you're doing the same amount of work, you'd use the same amount of energy. It shouldn't matter which gear you're in... less torque x more rpms = more torque x less rpms = same amount of work.
But at higher RPM, there are more bangs per second = more power in, more power out.
Not quite... think about it. The end product is moving the bus down the road. Let's arbitrarily choose a vehicle speed and work from that... say 35mph? If you're going down the road at a constant 35mph you can assume that you require a constant amount of power (work) to get the job done. If the engine was producing more power/work the bus would speed up... less power, it slows down. You're overcoming air resistance, rolling resistance, and all those other little parasitic items that keep perpetual motion machines out of our reach. Lets just arbitrarily guess that a bus needs 15hp to drive at a constant 35mph.

Now, it doesn't matter what gear you're in... that has no effect on all those resistances you're overcoming (except the ones internal to the engine that are rpm dependent). In fact, you don't even need to be in any gear, or have the engine running! The fact remains that somehow, you need to come up with 15hp to keep that bus moving at 35mph. Well, we're lucky and we have an engine and a transmission so we have options. Let's see, I could get my 15hp in third gear... so I'd need a certain amount of torque (from the engine) at a certain rpm, through the transmission, to the wheels to get me 15hp. Or, I could go in fourth gear, I'd need more torque from the engine, but at a lower rpm, through the transmission, to the wheels, to get me the same 15hp. If I didn't get 15hp I'd speed up (or slow down). Make sense?

Just because there's more bangs doesn't mean you're producing more power. That's what the throttle is there for. Each individual bang at a higher rpm is producing less power so that the cumulative total is the same. The engine has the potential to create a certain amount of power/work... you use the throttle to dial it back to where you need it.

Wheel torque is completely dependent on engine torque, the transmission is just a multiplier - it doesn't "create" any torque.

If we continue with the thought process, you could conclude that if you were able to roll down a hill in neutral at a steady 35mph you would be reducing your elevation at a rate of 15hp. Height is one form of potential energy. Fun stuff to ponder while your brakes are fading. :king:
I think I misread what you were saying in your original post. Anyway, I'm way too tired and whackout out on Rx painkillers right now to think about it, as my back is out again. :lol:
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Re: Eary Bay - Top Speed?

Post by hambone » Wed Apr 06, 2011 9:19 pm

SO, I drove all over town today, shifting at 3500. Checked the engine at random stops, all cool. I feel like a kid in a '74 Nova gunning it. It is a peppier way to drive. The engine IS happier to have higher RPMS in the next gear. Strange that all that fast running is good for an engine. Shifting into 4th at 45! What a rush!
I kept second-guessing all your advice all day. "This CAN'T be RIGHT!!" Ok ok. This forum is a collection of me learning things the hard way.
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