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04-12-2012, 09:00 PM | #24 |
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Comparison to other E9x M3s
The blue and green lines on this plot represent other E9x M3s runs on the same dyno (diff day.) No mods other than rear section exhaust.
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04-12-2012, 09:07 PM | #25 | |||
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You can see in the post above this the comparison to other E9x M3s on the same dyno (diff day.) Wildly different...
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04-12-2012, 09:17 PM | #26 |
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To add to the insult, the other two runs were done in even warmer weather.
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04-12-2012, 11:15 PM | #30 |
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Hmmmm. I have never had a car that didn't dyno in direct when the car did have a 1:1 gear. Not saying thats how it is with this one, just haven't run into it. Gonna keep my eye on this one.
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04-13-2012, 09:07 AM | #31 |
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Where did you get your dyno done?
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04-13-2012, 09:28 AM | #33 | |
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04-13-2012, 11:57 AM | #35 | |
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Sometimes this is the case. Read this: Will different final drive ratios affect the dyno readings? This one's tricky. First, there are potential discrepancies because different gears have different inertia values, generate more friction, and change the amount of tire slip. Higher numerical gears tend to be more inefficient, so as gear ratios increase numerically, power levels tend to slightly drop, particularly on an inertia dyno. When torque is multiplied by steeper gears, tire slippage also tends to increase. However, there's another, often overlooked, factor in the brew: rpm and torque are inversely related to calculating horsepower, so changing the rear axle ratio or testing in other than a 1:1 transmission gear seemingly shouldn't change the horsepower numbers. But this doesn't take into consideration the fact that changing gear ratios changes the engine's rate of acceleration. For example: We know that on an engine dyno, if you change a sweep test's acceleration rate from, say, 300 rpm/second to 600 rpm/second, the flywheel power number (bhp) drops due to the faster rate of acceleration. As an engine accelerates at a higher rate, the power required to accelerate the engine increases, and a greater portion is consumed before it gets to the flywheel. Going to numerically higher gear ratios-whether in the trans (testing in a lower gear) or in the rearend-is like increasing the rate of acceleration in a sweep test. Whether this actually changes a given chassis dyno's reported results depends on how the specific dyno manufacturer does its math. For the most consistent results, always test in the same trans gear (generally 1:1) and rebaseline the vehicle after a rear-axle ratio change. Read more: http://www.hotrod.com/techfaq/hrdp_0...#ixzz1rwMto5lN EDIT: There's a big BUT though. I think if this were the issue your torque would be higher than the other two.
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04-13-2012, 12:43 PM | #36 |
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OP, your dyno looks very rocky for a smoothing factor of 5 on the plot. If you have Winpep, load the data with a smoothing of zero, and you'll see it looking extremely jagged. Such a rocky dyno plot on smoothing of 5 is common on tuned N54s, but not M3s, so that indicates it more than just operator and/or environment. The car is not running right imho.
I would do a full PM on the car including changing the spark plugs (with proper gap), update the DME if at all possible. Then, drive it for a couple of days HARD, with several trips to redline in at least 3rd gear if you can do that safety somewhere. Then, immediately dyno the car and enjoy 340+ rwhp. Whatever you do, don't dyno your car after you've been featherfooting it for weeks on end. You want to really wring it out under as much load (as high a gear as possible) as you can all the way to redline several times (to set your trims), and then dyno as soon as practical after that. If you don't hit that 340+ rwhp, do a compression/leakdown test and let us know the results. |
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04-13-2012, 01:18 PM | #37 |
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My dyno was in 5th..however the difference wasn't that great when in 4th.
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04-13-2012, 01:21 PM | #38 |
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Thanks guys for all the input. Robertyu, I agree it looks choppy (I previously looked at it without smoothing) but don't have a frame of reference to judge that. What do you mean by "full PM"?
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04-13-2012, 01:21 PM | #39 | |
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Dave
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04-13-2012, 01:24 PM | #40 | |
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04-13-2012, 01:26 PM | #41 |
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No smoothing
No smoothing view attached. The guys at the shop were thinking it was pulling timing but wasn't sure what would be causing that.
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04-13-2012, 03:58 PM | #43 |
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Have you had your plugs done yet under warranty? Should be about in that window if not aren't you?
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04-13-2012, 04:39 PM | #44 |
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Pretty sure I have not. I think based on the recs starting with the plugs, a DME update and trying another gas station and getting it run again.
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