Posts by PoweredByCNG

The forum is in reduced operation. The Addon and Support forums remain open.
Please note that OMSI is no longer under development. Some of the developers are now working on a new simulator. Further information concerning the LOTUS-Simulator can be found here.

    People seem to forget two things when it comes to the Volvo hybrid bus concept.

    Firstly, the gearbox is an automated constant mesh manual with three forward gears, high and low range and a split, making 12 possible forward ratios. This means that there's a conventional clutch involved as opposed to a fluid coupling and therefore there will be breaks in tractive torque during gear changes, giving the impression of slower acceleration.

    Secondly, the hybrid powertrain consists of either a 4.7 or 5.1-litre diesel engine (D5F215 or D5K240) coupled with the i-SAM electric motor in parallel as opposed to in series, meaning that either or both motors can directly power the driving axle at any given time. After the first gear change or when the battery charge is low, both motors power the driving axle, giving high combined output figures equivalent to that of a regular diesel-only bus.

    I would love to see a true Volvo i-Shift implementation, i.e. one that skips gears like they do in real life. It's not unusual for a Volvo hybrid bus to only use four or five gears to accelerate from standstill to top speed.

    Also, the Volvo hybrids (at least in Euro V / EEV form) have engines fitted with exhaust brakes, that are actuated when slowing down from high speed.

    See this video:

    Furthermore, there is no sound from the releasing of the door interlock / "door brake" / "bus stop brake". On the real bus, there is such a sound.

    Otherwise, I'm really enjoying the map and buses.

    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.

    Thanks for the detailed explanation!


    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.

    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.

    Thanks again for the information. I'm going to include the engine_constfile with the correct torque values in the next update, but so far there's no plan to upload one just for this one file.
    In order to reduce the maximum speed to about 85 km/h I had to choose a 5.1 axle ratio. Or am I missing something?

    Based on 5.263:1 being the final drive ratio, I am seeing roughly 85 km/h with the governed speed set to 2300 rpm.


    I don't know anything about diffs from the O405 in the O305G axle (I would assume that the axles were more or less identical anyway) but also don't forget that the diff is only one factor of the final ratio, as the reduction hubs add to it and they were available in different ratios too. The O405 series had smaller wheels which had to compensated by a different geared final drive (of which the wheels themselves are a part too, of course). I'm absolutely sure that your final drive ratio was never available in Europe in the O305G, even the O307 had a maximum speed of only 98km/h with its fastest rear axle (and so did the O407 and O408 ).

    The diff centres on the O 305-series and O 405-series are interchangeable. Also, the diff centres on MAN SL 200/SL 202s are interchangeable with Mercedes-Benz ones.

    Regarding the tyres on the O 405-series, you are correct, they are generally smaller than the ones used on the O 305-series (the steel wheels themselves are actually the same). My O 405 (as seen in my display picture) was actually constructed with 'regular' 11R 22.5 tyres as found on the O 305-serie but other O 405s in my group have 11/70R 22.5 tyres. Smaller tyres indeed have a 'gearing down' effect so you lose roughly 10 km/h with that change alone. Also, generally, the O 305/O 307s were offered with 4.768:1 as the tallest final drive ratio option, which in practice is good for about 100km/h.


    The vehicle weight has got no impact on the maximum speed by the way, at least as long as the road is totally flat. It only takes longer to get there


    Absolutely correct. I thought that I'd add that comment anyway just out for interest.

    Hi and thanks. I've got the performance charts myself in a brochure from an exhibition in 1978 and the values in the engine_constfile should be correct. I chose the final drive ratio for a roughly 85km/h top speed, as apparently Omsi doesn't calculate correctly and the bus would be far too fast with the correct value. As far as I remember Mercedes claimed that the articulation control is working reliably up to a speed of 95km/h but no O305G was able to go that fast with the factory adjustments.

    The following was extracted from the performance charts that I have:


    According to the aforementioned brochure the following final drive ratios were available: 6.734, 5.921 and 5.263, the latter most likely only in combination with either the OM407hA or the 4-speed gearbox with a very low 1st gear. I think this Bahnbus version is almost too powerful and accelerates too fast too, which might be down to Omsi again not calculating for example driving resistances correctly. It's fun though


    I understand that there are many combinations possible. I have seen O 305s with O 405 diff centres, O 405s with O 305 diff centres and so on. My own O 305 G has an unusual specification with a 4.203:1 final drive to allow for a top speed of 110 km/h. My city also at one stage had 3-speed 240hp O 305 Gs with the 5.263:1 final drive delivered new in 1979-80. These were adequate for our generally flat topography and allowed them to be used on freeway services. Later deliveries (1986-7) were 3-speed 280hp units with 5.409:1 final drive and performed much better. Regarding OMSI, I find that the achievable speeds are quite close to the numbers that you can calculate manually, and even a little bit lower than expected. Just for reference, an O 305 with a 5.22:1 final drive has a theoretical top speed of 87 km/h at 2,200 rpm and the same bus type but with a final drive of 5.937:1 has a theoretical top speed of 75 km/h.

    I should note also that the O 305 Gs with third-party bodywork in Australia are much heavier than the ones built in Germany. My own O 305 G has a dry weight of 14,820 kg.

    I have the engine performance chart for the M-B OM 407 hA if you are interested, as my own O 305 G has this engine.

    The final drive ratio would likely be 5.409:1 as in practice, buses fitted with this ratio with a good engine can can achieve 85-90 km/h. The standard ratio of 5.921:1 is good for only 75 km/h or so.

    The ratio for the first gear of the W 4 A 110/3,5 R gearbox is 3.51:1. It should be noted that on my O 305 G fitted with this gearbox, 1st gear is only used when ranges [1] or [2] are selected. In ranged [3] or [4], 2nd gear is used for starting, so in the normal driving range [4], the gearbox behaves like a W 3 A 110/2,2 R.

    Isn't it a 470LA-machine? Because it's an articulated Citaro G of second generation.

    No, it is definitely an OM 457 LA in Euro V/EEV specification. The OM 470 doesn't have such an audible turbocharger, and the exhaust sound is definitely indicative of an OM 457. The first of the second-generation Citaros (2011-) were built as Euro V buses. Also, at the end of the video, you can see that the rear of the bus is missing the tell-tale roof-mounted air intake pod that only the Euro VI buses feature.

    You can increase this value to get a more powerful TC:

    Thanks. Another thing that I just remembered too. Ecomat 2 gearboxes and newer tend to change down into 1st gear a lot easier than the original Ecomats. Is it possible to implement this feature? On that topic, the downchange into 1st gear, particularly on kickdown, is usually met with a half-second delay. I'll show you an example of a ZF 6 HP 592 C being driven hard on a bus with a 299 PS Mercedes-Benz OM 457 hLA Euro V engine. You can also hear the different gear sounds on the lower torque gearbox.

    Do they really have different cogs thus resulting in a different sound? I'm not really sure.

    It's an interesting question that I will forward to my contacts at ZF. I will get back to you with an answer, but the 50x and 59x definitely sound distinctly different to the 60x.

    Another thing I also noticed is that the restriction in unlocked 1st and 2nd gear is far too much and actually prevents certain buses from starting on a hill. I notice that the torque converter restriction has been removed from the antrieb constfile. Where are the parameters set for this now?

    Hi Morphi,

    Just a couple of suggestions for the Citaro sound pack.

    Firstly, I notice that the sounds used for the ZF 6 HP gearboxes were all taken from a 600/602/602 gearbox. The only Citaros to use the 6 HP 602 or 6 HP 604 gearboxes are those that have the highest output version of the OM 457 LA (354 PS, 1850Nm)) or OM 457 hLA (354 PS, 1600Nm) engines due to the high torque. The ZF 600/602/604 gearboxes sound distinctly different to the 500/502/504 or 590/592/594 gearboxes. It would be good to have two different sets of gearbox sounds, one for the 5 HP/6 HP 500/502/504/590/592/594 and the other set for 5 HP/6 HP 600/602/604.

    Secondly, I don't really like the close-up view in the cockpit as it requires a view change to see the driver's side rear view mirror even on my 2560x1440p resolution monitor. Would it be possible to change the views to closely match that of M&R's original views as seen on the SD/D/GN/EN buses?

    Oh, and one more thing, is it actually possible for ZF Ecomat 2 gearboxes to have retarder release sounds like the original Ecomat? I can't say that I have come across any in my country that sound like that. It's not possible for the Citaro to be fitted with a gearbox generation older than Ecomat 2.

    Thanks again.

    Let me post my log file.

    Further to the above, I have just reinstalled OMSI including all addons. Iam still having the same problem.

    Can anybody give me some advice?

    Many thanks.

    Hi all,

    Many thanks for a fine map and collection of buses.

    I am, however, experiencing a rather annoying problem, as can be seen in the following screenshot.

    Does anyone know how I can fix the partially-white roads? I have all of the 'addons' that are prescribed in the instruction manual and no files are missing, according to MapTool.exe.

    Any assistance is greatly appreciated.