04-05-2024, 03:23 PM | #1 |
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How much drivetrain loss?
I know this isn't an exact thing, but in the past AWD cars I always assumed had pretty good drive train losses. 15 to 20%. As cars get newer and drivetrain component get heavier, wheels/tires get heavier I'd expect that to rise?
I've seen some wheel horsepower numbers for a stock X3M at around 460whp. Adding 15% to that seems like an unrealistic number so maybe the efficiency of modern cars actually makes it lower? For the dyno folks out there that can calculate drivetrain loss to some extend what is a good rough percentage of loss? |
04-05-2024, 03:51 PM | #2 |
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I would guess in the 15-18% range for this vehicle.
BMW always underrates their power ratings it seems recently. Although these are rated at 503 it seems likely they are more in the mid 500 range. |
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04-06-2024, 08:29 AM | #3 |
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So with the Bootmod3 stage 1 93 tune you are looking at 550 at the wheels.
Adding back in 15% you are looking at 630 or so at the crank. That seems a little on the high side? |
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04-07-2024, 01:33 AM | #4 |
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BMW is very conservative when it comes to their numbers. That 0-60 MPH they claim is measure with 4 medium sized passengers & a full or half tank of gas believe. That's why people often achieve better acceleration numbers.
And the same goes for their quoted power numbers too. That 503 HP for the Comp model is really how many ponies are transferred to the ground to all 4 wheels on 93 octane. So this means the S58 makes about 560 HP at the flywheel. If you don't believe me, go ahead & spend hours looking this stuff up. BMW uses a very VERY efficient ZF 8-speed & many strong relatively lightweight parts. So in today's world we often see about a 12% drivetrain loss. I've had 4 different flavors of F97's in less that 4 years. So I tend to know my stuff a touch better then the average Joe might.
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04-07-2024, 04:46 AM | #5 |
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FWIW,my stock LCI X3MC put down 506awhp at EuroMpire on their DJ w a tank of 93. There's pics/vids if you feel like searching
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04-07-2024, 08:59 AM | #6 | |
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what was the correction factor? Ambient temperature? Humidity? Thats pretty good. Need to dyno mine non comp Last edited by TacosRule!; 04-07-2024 at 09:06 AM.. |
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04-07-2024, 09:39 AM | #7 | |
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Just puttin that out there for anyone reading this for the 1st time;your particular results may vary up/down https://x3.xbimmers.com/forums/showthread.php?t=1944152
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04-07-2024, 10:07 AM | #8 | |
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460whp and 490whp are typical dyno numbers for a Non comp vs Comp. Which can certainly be skewed up if the dyno brand changes or the correction factor is altered. |
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04-07-2024, 02:28 PM | #9 | |
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04-09-2024, 09:02 AM | #10 |
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I've seen a couple YT videos of guys in the UK tuning M3 and m-sports with Xdrive and they all are estimating 20~22% drivetrain loss.
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04-09-2024, 10:31 AM | #11 |
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04-10-2024, 02:11 AM | #12 | |
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04-10-2024, 08:39 AM | #13 | |
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It's the same percentage that I've heard the guys from Integrated Engineering quote too.
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04-10-2024, 08:53 AM | #14 |
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I've used this calculator for years just for shits&giggles..if you know the exact weight of your vehicle w you in it,plus fuel(in other words,race-ready) it's been pretty accurate for me.
I used it all the time when I was drag racing my bikes and it was always close to the dyno rwhp Gives you a ballpark figure,and you can calculate drivetrain loss. It's not scientific by any means and YMMV http://www.wallaceracing.com/et-hp-mph.php
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04-10-2024, 10:13 PM | #16 |
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Here are Dinan numbers from a 2020 model X3MC.
https://x3.xbimmers.com/forums/showthread.php?t=1897657
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04-11-2024, 03:24 AM | #17 | |
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04-11-2024, 07:41 AM | #18 | ||
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For the original topic of this thread -- drivetrain losses are not static and increase at higher loads but for the purpose of general broad stroke calculations, modern RWD BMW's are in the 12-15% DT loss range whereas AWD platforms sit in the 18-21% spectrum. |
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04-12-2024, 01:29 AM | #19 | |
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04-12-2024, 07:11 AM | #20 | |
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Those look more like crank hp numbers to me... I guess that's the problem with dynos, they vary widely and can be manipulated by the tuners to show what they desire. |
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04-12-2024, 07:34 AM | #21 |
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508 BMW advertised HP is definetly under rated. I don’t think Dinan’s Dyno is off since they are in the hp business.
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04-12-2024, 10:00 AM | #22 | |
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Plus, the "508 HP" is the "under rated" part. Since BMW doesn't seem to want to use the SAE bhp standard that most other manufacturers use, them claiming 508 HP and putting down 490-500whp, makes them look under rated. When in fact, they're just choosing to rate their vehicles differently. Last edited by strohw; 04-12-2024 at 10:05 AM.. |
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