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04-21-2017, 10:49 AM | #1 |
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M4cs Power output analysis - This S55 variant is quite potent
I originally posted this in the M4cs thread, but decided to start a separate thread in the engine section for a more in depth technical discussion. The S55 variant in the M4cs seems to be quite potent. Much more so than the modest 10hp peak increase over the CP suggests.
I had a little fun plotting the base and Comp Pack rated power curves over the CS (preliminary) rated power curve. It is interesting to see that the CS provides substantially more area under the curve over the CP compared to what the CP provides over the base S55; and this despite having half the peak gain (10hp vs 19hp). That is what 37lb-ft of extra torque does for you . It should make the CS quite quicker than the CP and even more so than the base M3/4. It's also interesting to notice the CS has less power than the CP and base S55 below ~2300RPM. I wonder what changes were made to the engine? Is this the result solely from a different tune? EDIT (Nov-2017) On a quiet, cold and rainy Sunday afternoon, I had a little time to kill. So I set out to capture test results from European publications (mostly German) for acceleration to compare the different M4 variants. To remove the effect of the added grip at launch provided by PSC2 when the cars are so fitted, I only set out to capture the 100 to 200km/h acceleration. I compiled 21 different tests and then averaged the results for each M4 variant (DCT only). While this is not the most scientific approach, it does provide a decent perspective. Here are the results: 100km/h -> 200km/h acceleration 9.52 M4 Base (6 samples) .... ∆ 0.20 9.32 M4 CP (9 samples) .... ∆ 0.67 8.65 M4 cs (4 samples) .... ∆ 0.20 8.45 M4 GTS (2 samples) First, I think this dispels the rumours that the CP is not any quicker than the base model, having a ~0.2 second advantage from 100 to 200km/h. Second, it also shows how the CS pulls quite strongly in the top end, being ~0.7 seconds faster than the CP and only ~0.2 seconds short of the mighty water injected GTS. Which is in line with the conclusion reached when looking at the power charts . CS in black, CP in red, base S55 in blue:
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04-21-2017, 11:02 AM | #2 | |
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04-21-2017, 01:00 PM | #3 |
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Your statement tells me you don't know much about engine testing and how official manufacturer ratings are obtained
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04-21-2017, 01:04 PM | #4 | |
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04-21-2017, 01:05 PM | #5 |
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Knowing what we now know about the S55 now, they're just running more boost and maybe some overlap changes @ Peak VE to get that extra power under the curve.
I'm not sure why BMW didn't just reuse the water Injection from the GTS, TBH. |
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04-21-2017, 01:12 PM | #6 |
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Interesting analysis of the 3 variants. I also think its important to note the flat power curve for the CS model. Doesn't seem to peak like the CP.
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04-22-2017, 11:22 AM | #7 |
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Someone always has to argue with the engineer....
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04-23-2017, 06:01 AM | #8 | ||
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Further, did you notice that in the press releases they talk about a lightweight magnesium oil sump?
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04-23-2017, 06:49 AM | #9 | |
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As for the magnesium oil sump, I must have totally missed that as I didn't see it. I need to go back and read that press release again. |
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04-23-2017, 07:09 AM | #10 | |
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About midway in the 4th paragraph of the engine section in the "long version" of the press release.
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04-23-2017, 08:55 AM | #11 |
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I saw that but assumed that they were referring to the S55 engine in general rather than the CS variant. Didn't the early S55 come with a magnesium oil pan ? (happy to be corrected if it didn't). And what about the extra oil suction pump ? Does the CS variant actually have an extra oil pump or, again, are they talking about the S55 in general ?
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04-23-2017, 12:00 PM | #12 | |
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04-24-2017, 07:50 AM | #14 | |
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But I wonder why they would have purposefully reduced the low end-power on the CS by so much if it were through software only ??
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04-24-2017, 12:53 PM | #15 |
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BMW just plays with the timing and boost control and fine tunes the engine map even more.
Maybe the stepper motor on the boost control is even finer resolution. I bet you in a year or so some tuner will offer the update for the ECU for all cars... |
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04-24-2017, 02:36 PM | #16 |
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Why would BMW REDUCE the power below 2300RPM on the CS engine if it is only from a change of tune ?
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04-24-2017, 04:46 PM | #17 | |
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That is the only logical reason I can come up with. |
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04-24-2017, 04:46 PM | #18 |
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There would be no point. Stage 1 flash tunes already exceed the performance of all factory available tunes for the S55. For the majority of people, if you're splitting your DME case, you're not going to go with a mild OEM upgrade. VF offers a ZCP-style/performance map, but I can't imagine the uptake on that is very high when the cost for the much more significant performance bump (Stage 1) is marginal.
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04-24-2017, 05:47 PM | #19 |
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You're reading too much into the marketing 'power' graph that BMW publishes.. it's a gross representation of the engine power curve and each motor varies over production tolerances. Best thing to do is wait until someone actually dynos a CS and then you can see the differences...
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04-24-2017, 06:02 PM | #20 | |
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The challenge with modern engines, particularly forced induction ones, is that they can produce more power when in transient than in steady state, giving the impression that they are "underrated" from the factory.
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11-05-2017, 03:44 PM | #21 |
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On this quiet, cold and rainy Sunday afternoon, I had a little time to kill. So I set out to capture test results from European publications (mostly German) for acceleration to compare the different M4 variants. To remove the effect of the added grip at launch provided by PSC2 when the cars are so fitted, I only set out to capture the 100 to 200km/h acceleration. I compiled 21 different tests and then averaged the results for each M4 variant (DCT only). While this is not the most scientific approach, it does provide a decent perspective. Here are the results:
100km/h - 200km/h acceleration 9.52 M4 Base (6 samples) .... ∆ 0.20 9.32 M4 CP (9 samples) .... ∆ 0.67 8.65 M4 CS (4 samples) .... ∆ 0.20 8.45 M4 GTS (2 samples) First, I think this dispels the rumours that the CP is not any quicker than the base model, having a ~0.2 second advantage from 100 to 200km/h. Second, it also shows how the CS pulls quite strongly in the top end, being ~0.7 seconds faster than the CP and only ~0.2 seconds short of the mighty water injected GTS. Which is in line with the conclusion reached in the OP when looking at the power charts .
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