Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving - Fall 2012 on)

[some_other_dave]

Another way to explain it is that it's like the crank gears on your old 10-speed bike. The rear gear has 5 selections, and the front has two, giving you 10 speeds total. The numbers of teeth are calculated to give you relatively even drops between them.

The external OD can theoretically be triggered in any gear, in effect giving you an 8-speed box instead of the stock 4-speed one. However, due to the number of teeth used in each of the two gear selections in the OD box, it isn't very useful with 1st or 2nd. It sounds like it could/should be useful in 3rd and 4th, though!


....Oh, and to be clear: Technically the term "overdrive" simply means that the output shaft is turning faster than the input shaft. That can be done inside the gearbox (as most modern cars do) or with an add-on box, like the Laycock-De Normanville one we're talking about now. Because they hadn't figured out how to package 5 real gear sets in a transmission at the time, and using an external box to step up the RPMs even further was a viable alternative. Nowadays, they know how to fit as many as eight (so far!!) gearsets into a single housing, so the external OD isn't needed. For a while, you could find some literature mentioning "double overdrive" five-speeds, because the top two gears were both overdriven. Now it just seems to be assumed that at least the top gear (or sometimes more) have a ratio lower than 1:1, so nobody really uses the term much.

-soD

[changzuki]

Another side-note on this transmission swap:
The is as far as one can take the stock factory Spitfire drivetrain.
The 1500 4speed, equipped with the overdrive option, and connected to the 3.27 rear differential are the end of the line for Spitfire bolt on components.
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This will be a good test since as the rpms drop, so does the horsepower. Will the little Kubota's torque be able to carry the car over the roads at this reduced rpm while in 4th gear with overdrive engaged?
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We shall see!
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~CrazyJerry

[UltArc]

Jerry, I hope someone doesn't pick up your car and put it in their pocket and run away with it! I want to beat you at GGP2015!

This is cool stuff. Very interesting to me. Did you mention why you don't run a fuel log here?

[changzuki]

Originally Posted by UltArc

Jerry, I hope someone doesn't pick up your car and put it in their pocket and run away with it! I want to beat you at GGP2015!

This is cool stuff. Very interesting to me. Did you mention why you don't run a fuel log here?

UltArc,
When this current thread (the transmission/overdrive swap) is complete, I plan on posting fuel numbers from the beginning. When you see the numbers along with the associated notes, the numbers will make sense. Remember, this car has been taken apart, reassembled, quite a few times. Without knowing what was done, the fuel logs mean nothing - zero.
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Here's a quick example: The 1st fuel log I have is for 88.9mpg. Ok - STOP.
What comments or conclusions might be drawn from just that basic fuel log entry? Followers of the original Centurion and it's 128mpg figure would say this car fell short.
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Without the notes, the 88.9 mpg is open to interpretation, and it would likely be incorrect. 10 different people = 10 different opinions.
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When (and if) I end this thread with those numbers, you'll see that the first entry of 88.9 mpg is based on a "new engine" with "warm ups" . There was no glass at all in the car except the windshield. There was the unstoppable 25amp draw of the Kubota dynamo, a misalignment of front toe-in, and more importantly, the rear trailing arms which had to be attached to the frame and shimmed for correctness - thus throwing off the rear alignment. The maiden voyage was only on back roads where 55mph would've been very hard (if not impossible to obtain) and the roads are rough, very twisty, and very hilly to boot. So, without the details the previous fuel log of 88.9mpg doesn't mean much... Or maybe that's just my feeling on this....

The Green Grand Prix on the other hand was worth it's weight in gold. We know so many of the details: course, conditions, car, driver, passenger, mileage, accurate repeatable graduated non-heated fuel tank refill, etc... And, we have an entire fleet of vehicles competing at the same time to compare with! Awesome! So, whatever the number ended up at that event, would certainly be posted.

So, that's where the fuel log is at - most likely being posted in the last closing posts of the Centurion thread somewhere down the road.

As for you beating me at the 2015 GGP.... I would love it if you tied or blew past the current numbers!! They are beatable, and all records are made to be broken - period.

In a couple of minutes, I'll make a separate post of things I jotted down that may (or may not) help anyone, but did apply to Centurion's winning run!

~CrazyJerry

[changzuki]

11 Points to Ponder (especially #11)....

Using the course at the Green Grand Prix with its turns, hills, and traffic, or, using your own vehicle and driving conditions, let's look at some items that have been mentioned and think for a moment the effect they can have on fuel economy versus a complete clone (or not clone) that hasn't or can't take advantage of the following:

1) Lightweight where possible, including rotating mass. What's it worth in fuel savings while driving with varied, mixed conditions?

2) Aerodynamics - in the case of Centurion vs Centurion there are differences (windshield rake, ground effects, and underside). Aerodynamic differences in two clones - what's it worth? In the case of Centurion vs normal car - what's its small frontal area worth?

3) Drivetrain - again, in the case of Centurion vs Centurion both achieve 65 mph but there are stark differences in drivetrain methodology even though the agreement is on lowering rpm. But we've each tailored our drivetrains for the task at hand (urban driving vs more rural & highway). What is a more efficient drivetrain worth in fuel savings?

4) Fuel shut off - Governor behavior didn't seem clearly understood so I gave an example and a video clip. Being able to effectively shut fuel off to the combustion chambers "at will" - what might that be worth in fuel savings?

5) Decompressor - if you've never experienced the compression release while coasting, well - it's amazing! Releasing cylinder compression with potential to use the rotating mass of the engine - what's it worth in fuel savings? Anything?

6) An engine that's in it's perfect published bsfc range - roughly 80% loaded vs one that is not. what's it worth in efficiency / fuel savings?

7) Gas vs Diesel - from the btu angle. Any fuel savings there?

8) Air to fuel ratio - in discussions throughout the boards it appears that lean-burn is a desirable quality (setting emissions aside which is debatable). In terms of lean burn, a diesel "is" as long as it's not "rolling coal".. What's the lean burn worth in say fuel savings?

9) A driver who knows his/her vehicle - Each person who is driving a car has the ability to raise or lower their mpg on demand regardless of all the current technology. Initially, I learned to drive vehicles by the seat of the pants. Then for years, I learned on a human-dyno using a computrainer. Next came a scangage, and this was on both gas and diesel engined vehicles. Each had their own best practices to turn in great numbers, and so does Centurion. What are these driver applied strategies worth if done correctly?

10) Minimal electrical load - Eliminating alternator load has benefits especially when the engine is small and of limited power. This allows for more of the power it makes to be available, or reduces the load on the engine however one wishes to look at it. Centurion, the Listeroid, and Changzuki do not need electricity to run. Without the drag on the engine of some mechanism to create electricity, what's that worth in fuel savings?

11) ***A specific purpose-built vehicle vs one that is not. This point is huge and typically overlooked. Only a small handful of cars at the GGP (and around) are purpose-built for exceptional mpg. What is a specific purpose-built vehicle for high mpg worth vs one that is not?

There are enough examples above to ponder between any two identical vehicles, or between two different vehicles and what the overall effect will have on something like MPG.

The next logical step is to then put the items from above into practice to see if they work as predicted and make any adjustments/omissions as necessary.

Pulling a personal mpg best, or setting a record at an event like the Green Grand Prix is not a mystery, or looking for some magical alternatives to explain a high mpg run. It's a series of well thought out best practices that were put into a real world working example. (Now there's a quote!)

I think everyone that achieves personal best mpg's (be it at home or at an event) may agree with the above statement. And those ecomodders that did well at this year's Green Grand Prix, quite frankly had their act together, but that's just my observation.

Lastly, when you hear stuff like "so-and-so used every trick in the book", please keep an open mind... Records were made to be broken and occasionally are.

When this happens, "every trick in the book" - just got rewrote..

~CrazyJerry
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[UltArc]

I understand your point. I like to see how my vehicle has developed, and how it improves as I fix and change things- I agree, some of your numbers back in the day would not fairly show where you are now.

[Xist]

UltArc, you are able to calculate fuel usage to the 130th of a teaspoon? Do you also measure distances to the 1/19th of an inch?

[ME_Andy]

You've done so much but there's a lot more you could do. I bet you could hit 300mpg if you had $10k and a year to work on Centurion. Off the top of my head, you could go with LED bulbs, Lexan windshield, aluminum driveshaft...

[redneck]

Originally Posted by me_andy

i bet you could hit 300mpg

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[changzuki]

Originally Posted by redneck

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What Redneck said -

~CrazyJerry -