Is every tank that uses the R975-C4 nerfed?

I’ve been on a bit of a Israeli kick recently, looking into options to flesh out the tree from 1.0 to 6.0. as I have been doing this I’ve been looking at the differences between the M50 Degem Alef (in game this is basically the french M4A4 (SA50) and the M50 Degem Bet. The Degem Bet uses HVSS, and a new Cummins Diesel engine that produced 460 HP. I’ve seen sites say that it was more powerful than the previous engine, the Wright Continental R975-C4. This has not sat well with me. I thought that I had read that engine had a gross HP of 460?

So I looked at some sources. “Sherman, a History of the American Medium Tank” by R. P Hunnicut" sure enough says that the engine has a gross HP of 460, and that is as good a place to start as any. I looked a bit more and found this very helpful technical manual.

Which says that it has a gross H.P. of 485 at 2400 RPM. There is also a document on the development of the R975 engines during the war, and at the end there is a nice table detailing the differences between them. This table lists the HP of the R975-C4 as 480 at 2400.

Now, none of these may exactly line up, but they do show significant improvement over the 400 gross HP R975-C1 engine. In game, however, it seems that all of the continental radial engines are treated as C1.

as a result, the following vehicles are missing out on at least 60 extra horsepower, if not 80.

M4A1 (76)W

M4A1 (75)W

M4 Hybrid
M4 Tipo 1C

M4A1 FL10
M4A4 (SA50)

I’ve looked and I have not seen any bug reports on this. let me know if I am way off base or if I missed any vehicles or added ones that should not be there. Thanks.

Gaijin has decided that only the M4/T26 is equipped with the R-975-C4 engine, while every other tank with an R-975 uses the C1 variant with 400 horsepower.

They have also decided to use the source “Catalog of Standard Ordnance Items, Volume I” for the horsepower values of the R-975-C1 and C4, as this is an official source groups together information on multiple tanks and multiple engines. This source states 400 and 460 gross horsepower for the R-975-C1 and C4 respectively, so that’s the horsepower values they have gone with.

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I have looked more into what tanks were being introduced when in order to see which ones would have the C1.
For the American tanks the specific flavors of M4A1 (76)W and M18 would have used the C1. I think it would be cool to have the M18 at least get a folder version with the upgraded engine (visual model changes are very minimal) but that is besides the point.

The M18 statement applies to the Italian and Chinese tanks as well

as far as the M4A1 (75)W goes I do not know enough to opine if the engine is correct. the model in game seems to have the wrong turret, which would imply that it is actually a later tank that uses the C4 engine but I do not know the fine details.

The italian M4 hybrid and Tipo 1C similarly were actually made before the C4 was approved so they would not get that engine.

The ones that make absolutely no sense to me are the french, especially the SA50. after the war the french standardized on the continental engine, rebuilding all tanks with different engines to use that one. after the war the continental engine that you could get your mitts on was going to be the C4. So why are those using the C1?

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I don’t really know. Would have to ask Gaijin themselves for a clear answer.

Hello gents I’ve just run into this issue, and created a bug report.

With TM 9-1725 as a source the gross output of the R975-C4 should be about 465 hp @ 2,300 rpm.

Gaijin uses a different source for power in all these engines (Catalog of Standard Ordnance Items) and they will always stick to it, your bug report will be rejected.

Also, getting horsepower at different RPMs isn’t as simple as doing this:

That’s because it assumes torque is the same between the two different RPM values. Which it isn’t.

Also, the R-975 is governed to 2300 RPM but can be pushed to 2400. As shown in TM 9-1725.

I can’t find the CSOI with the M22 in it but thank you for highlighting that, I’m just getting into US equipment.

Yes hp calculations aren’t so simple but it will do for the report.

I think the section you’re referring to is to do with engine break-in, it does talk elsewhere about testing up to 2,400 rpm and then adjusting the governor down to 2,200-2,250 rpm. I could be entirely wrong, but I’ll leave it up to them to review.

The M4A1s and M4s with their R-975 engines, for example, can only reach their top speeds of 39 km/h specifically if the engine is allowed to run 2400 RPM. You can do the math yourself if you have the data on the gear ratios and sprocket radius of these tanks, I have.

Here’s the math I just did with “Catalog of Standard Ordnance Items”:

Additionally, this source (which Gaijin uses above all) explicitly states that 2400 is the maximum governed speed of the R-975 engines.

Speaking of gear ratios, now that the M18 and the black cat have different engines (a change from last time if i recall correctly) does the tech tree M18 have the correct lowered final drive gear ratio?

The later M18s had a reduced final ratio, going slower but having better performance at lower speeds. Think that both M18s have same speed currently, and black cat should be faster.

They don’t have different gear ratios.

Currently the stats for all M18’s top speeds come from, yet again, “Catalog of Standard Ordnance Items”, with the page of the M18 being dated “1 October 1944” but the catalog itself stating “1 June 1945”. Both dates are after the engine and gun upgrades of the M18, and on top of that the page mentions that M18’s can come with either the M1A1 or M1A2 cannons, or the R-975-C1 or C4 engines.

Gotta look into it, but i think I am screwed up on this, thought that the first ones with the bad gear ratios were never fixed, but looks like they were before they were allowed into service. Think you are right.

I meant that they don’t have different gear ratios in game. I have no clue about real life.