PoweredByCNG's "Stadtbus O305 / City Bus O305" Upgrade Pack v1.2.1

Nicely done, as always!

Zitat von PoweredByCNG

Change log:-

1. Added new park brake apply sound for the StÜlB-fronted bus variant.

2. Slightly changed the behaviour of unlocked 2nd gear (2W).

3. Added a "version.txt" file in the root directory of the downloadable archive file.

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What exactly is "unlocked 2nd gear"? The W3D080 doesn't have the ability to open the torque converter lock other than in first gear. Or wait, that might be the explanation for the extremely smooth gearchanges of your Australian O305/O305G, but they must have a special version of the gearbox then, it definitely wasn't common or even available in Germany where the torque converter was locked within the 1st gear and only opened again in 1st gear below a certain speed. The gearbox is fully hydraulically controlled, the only external factor being the throttle linkage for kick-down which provides a controlled internal oil leak which then leads to a later build-up of oil pressure in the secondary oil pump which initiates the gear changes.

Zitat von Morphi

I guess the reason for this is, because it's a "Motordekompressionsbremse" (eng: engine decompression brake) and it works way different than the hydrodynamical retarders in Voith or ZF. If activated the pressurized gas in the compression stage will be released resulting in a braking effect. In addition, throttle injection will be reduced to idle.

No, it's actually not

An engine with a decompression brake (Jake Brake) would have a separate exhaust valve in each cylinder head, releasing the pressurised air from the compression stroke into the exhaust, the injection is also being put to zero-injection when activated. It's very (very) noisy. Very similar, but by far quieter, is the constant restrictor, also placed in the cylinder head and activated all the time while braking (whereas the decompression brake valve is only opened after each compression stroke when activated).
Mercedes' older OM4xx engines were optionally equipped with exhaust brakes, here the injection is pushed to zero and the exhaust is being blocked by a (only on-off) throttle very close to the manifold, so compressed air which is released in the 4th stroke is being pushed out against the throttle, thus creating a brake moment. This wasn't feasible for turbocharged engines, so the 280hp OM407hA and the newer OM447hA or hLA always came with retarders (the O305G with that engine thus always had a W3A110/R gearbox with integrated retarder) or similar systems where reqired (the constant restrictor - Konstantdrossel - being one of them).

Hi!

Do you create an new Upgrade Pack for the Citybus O 305 in Omsi 2? It would be nice!

Greets

So this one doesn't work with OMSI 2? Did you try?

I try it yesterday in omsi2 an the O305 1.10 works

Have fun

Am I the only one who doesn't see any download links?

Yes, you are

http://www.mediafire.com/?rb38qbb99qqf7am

thanks all

Amazing Sound recording from your own bus, thanks for sharing!

I have copied the files of V1.2.1 into the MB O305, OMSI 2.
However, I am getting the following results when loading the bus:

- engine is already switched on, bus starts moving
- engine cannot be turned off
- electric is off, cannot be switched on

The bus works properly with the original files.

Where is my mistake?

Greetings
Peter

Zitat von PoweredByCNG

e2h1986:

Unlocked 2nd gear is the hydraulic part of 2nd gear, where the torque converter clutch is not locked up. I have done extensive research into this, and I can tell you factually that the European O 305s have the same gearshift characteristics as the Australian O 305s, for example:

http://www.youtube.com/watch?v=kQmsqZ6ihnk

http://www.mediafire.com/download/kdaaa6dsiadk5m2/mo2619.mp3

You will find that upon upshift into 2nd and 3rd gears, you will feel a "double" gearchange, which correlates to the torque converter unlocking and then locking up again. When an O 305 re-accelerates from near-standstill, it actually moves off in unlocked 2nd gear, and shortly after locks up in 2nd gear, as demonstrated in the above video at 0:58.

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After only 2.5 years here's my prompt reply!

By pure chance the bus in the video was mine (part-owned) at that time and I was even driving it myself. I know the W3D/W3A gearbox almost inside out and I can tell you that it's technically not possible to unlock the torque converter in 2nd gear. At 0:58 the bus was almost stationary and the gearbox had then changed back from 2nd locked into 1st unlocked, as if moving off from standstill.
On those purely hydraulic controlled gearboxes there's a centrifugal governor that enables/disables the up- and down changing of gears as well as the torque converter locking according to the speed of the drive flange. The "double gearchange" you mention is in fact the result of a reduced clutch pressure for a softer gearchange, here the oil pressure that engages the multi-disc clutch for the third gear is slightly and shortly reduced to avoid jerking at the price of a short and slight clutch slip which then sounds like a double gearchange. On older and worn-out gearboxes this pressure reduction leads to the engine speed going up considerably before the clutch finally grips, this was a rather typical phenomenon on older O305.
You might be thinking of the 4-speed W4D/W4A gearboxes (which were very rarely ordered by German operators), which use 2nd gear with an unlocked torque converter to move off from standstill. I'm not entirely sure how 1st gear comes into action but I reckon that's got to do with the use of kick-down. Your Australian O305G with that very long final drive for a very high maximum speed might have a modified version of the W4A gearbox which generally starts in the rather short 1st gear.

Zitat von PoweredByCNG

There was actually no 'W 4 D' gearbox. All 4-speed gearboxes of that period were 'W 4 A'. My O 305 G uses 2nd gear for standing starts as well. 1st gear is only used if you manually select ranges '1' or '2'' on the gear selector controls. Even with a 4.203:1 final drive ratio, 2nd gear provides more than adequate startability.

Yes, that's true, there only was a W4A, which is essentially the same as the D variant, only reinforced for the higher torque.
Thanks for the information about the use of 1st gear on those 'boxes!

Zitat von e2h1986

Yes, that's true, there only was a W4A, which is essentially the same as the D variant, only reinforced for the higher torque.
Thanks for the information about the use of 1st gear on those 'boxes!

1st gear is mainly used for hill starts, for example in the AEC Routemaster the 1st gear has a very short ratio and is used for hill starts or when there is a full load.

Zitat von Whiskey .Stuffs

1st gear is mainly used for hill starts, for example in the AEC Routemaster the 1st gear has a very short ratio and is used for hill starts or when there is a full load.

While as a regular Routemaster driver I can confirm what you're saying, the same isn't generally true for automatic gearboxes (the SCG gearbox in the RM isn't an automatic gearbox as such - it's got some similarities though but is in fact an epicycling gearbox and lacks the torque converter which is typical for an automatic gearbox).
The MB W4A110/R gearbox was a rather special version for hilly areas, it's 2nd gear has almost got the identical ratio as the 1st gear of the three-speed version W3D/W3A and as we know now its 1st gear is only used when the driver presses the "1" or "2" button on the gearbox keyboard. But generally all automatic gearboxes always start in 1st with the odd exception of a few Allison 'boxes.