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      09-23-2014, 11:10 AM   #1
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M4 F82 Dynapack Hub Dyno Results with vBox Road Tests

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Introduction:

Like everybody else, we want some answers about the F8x dynos and performance. Some say the engine is underrated, and some say it's just right. Dinan recently showed 484 crank horsepower, but questions swirled about the methods: did the engine really come out of the car, or did Dinan run the car on the Dynapack and estimate engine crank horsepower. We don't know, but we have access to a Dynapack and that gave us an idea. We decided to take our Alekshop F82 project car to our local Dynapack guy for some testing, and then take the car to the streets of Mexico for some runs and data logging.

Hub dyno basics

One of the most widely acknowledged, credible, and independent automotive performance testing firms is the Rototest Research Institute (RRI). RRI has tested hundreds of cars. In the F8x dyno wars for over/underrating, RRI is frequently mentioned as the definitive source, and their dyno the definitive dyno to answer this question (over/underrating). Unfortunately, RRI hasn't tested the F8x, so no results are available. However, RRI uses the same type of dyno that we can test ourselves.

The RRI dyno operates on the same principles as an engine dyno, but instead of attaching to the flywheel, the dyno attaches directly to the wheel hubs (with tires removed). The engine is run at full throttle at all times and the dyno applies a hydraulic load to the hubs to bog them down to the specified RPM for torque measurements. The amount of hydraulic pressure required to maintain the specified RPM is directly related to the amount of torque produced by the engine. The gear ratio is entered into the dyno, and the engine RPM is calculated by the rotational speed of the hubs using this gear ratio input. It's a simple, elegant, and highly accurate way to measure.

To further increase accuracy, RRI uses "steady state" testing. Instead of letting the engine "ramp" through the RPM range, steady state testing holds the engine at a specific RPM for a specific amount of time. The torque is measured and averaged over this longer time period. This method removes all inertial effects of the drive train and makes the results far more accurate. This is why RRI is the gold standard for independent dyno testing.


As perfect as RRI may seem, there's a downside to what they do.
  • Steady state testing is hard on the car and engine. The procedure puts so much load on the engine which in turn generates a lot of heat. The generated heat makes it impossible to run a steady state test during a single session. Most people don't realize it, but RRI results are an amalgamation of testing at different times, different days, and even different gears. Dig into the original BMW E92 M3 test (link), and you'll see two different gear ratio's being used. Dig into the BMW E90 M3 test (link), and you'll see three different gear ratio's used, and two different sets of weather conditions, most likely coming from two different days of testing.
  • RRI uses non-standard dyno correction factors. This makes it harder to compare their results to the ones we see flying on the forums. RRI uses ISO-1585 horsepower correction, but the rest of the world prefers to use SAE-J1349.
Dynapack Dyno

The Dynapack is identical to the Rototest design philosophy and principles of operation. Everything that applies to the RRI dyno, also applies to the Dynapack. Think of the Dynapack as the RRI dyno that anybody can buy and use. With the Dynapack, we can run all of the same tests used by RRI and expect to get the same results. We can either test ramp or steady state testing. However as we will demonstrate a little later, there really isn't any need for stead state testing because we discovered a long time ago that a carefully chosen ramp rate can eliminate the effects of drive train inertia and make the results virtually identical to steady state testing. This eliminates all of the nasty side-effects of heat generation, cool down, and running the car on multiple sessions and piecing the results together from those multiple sessions. We also don't believe in running in different gear ratio's. Once we select the gear ratio, we leave it alone.

So a few days ago we took our F82 M4 to the Dynapack dyno and crossed our fingers. Our fingers were crossed because we didn't know if BMW locked out dyno mode on this car and prevented power runs while the car is stationary. We discovered there was no dyno lockout!!! Whew!


Car and Modifications:
  • 2015 BMW M4
  • Bone Stock
  • 93 Octane (Mix: ~4-gallons 100 octane, ~12-gallons 91 octane)
  • DCT
Conditions (Dynapack Weather Station):
  • Temperature:: 92.9 degrees F
  • Atmospheric pressure: 29.932 inHg
  • Humidity: 29.43%
  • Density Altitude: 2346 Ft.
  • SAE Correction: 1.008
  • STD Correction: 1.030
  • Uncorrected: 1.000
Results:
  • SAE Corrected: 421 whp @ 6585 RPM, 404 wtq @ 3655 RPM
  • STD Corrected: 430whp, 413wtq
  • Uncorrected: 418whp, 400wtq
Dyno Database:Individual Dyno Results:

Individual dyno results are shown below. SAE corrected results are shown twice, using two different sources. The first source (dpc) are the SAE corrected results straight from the Dynapack. The second source (sae) of SAE corrected results are obtained by using the Kestral 4500 weather station data for each individual dyno run and running it through an independent SAE correction formula. This ensures that the dyno results are accurate and can be independently audited and verified for authenticity and accuracy.


The legend below has the following meaning:
  • Dyno Run: Dyno run file
  • Timestamp
  • Temp(F) = Temperature (Farenheit)
  • RelH = Relative Humidity
  • Pressure(Hg) = Barometric Pressure
  • DA(ft) = Density Altitude
  • WHP(unc) = Uncorrected wheel horsepower
  • WTQ(unc) = Uncorrected wheel torque
  • WHP(SAEd) = Dynapack SAE corrected wheel horsepower (SAE-1349 2004+)
  • WTQ(SAEd) = Dynapack corrected wheel torque (SAE-1349 2004+)
  • WHP(SAEk) = SAE-Adapted wheel horsepower (SAE-1349 2004+)
  • WTQ(SAEk) = SAE-Adapted wheel torque (SAE-1349 2004+)


Graphs:



Boost was calculated using a 60-FPS video camera on the AWRON digital gauge and M4 instrument cluster for RPM. After downloading the Solo-DL data logs, we analyzed the video frame-by-frame to log boost data. We matched the dyno logs with Solo-DL logs to get RPM data we could use for the boost log. The RPM to video frame resolution was perfectly accurate (no extra frames at the end of the dyno run), and the AWRON boost gauge seems to have 1/4 PSI granularity. So the boost log above is in 1/4 PSI granularity and is per-RPM accurate.

Comparing Dynapack to Dynojet Results:

I've seen lots of people asking about comparing Dynojet to RRI or Dynapack. I'm not making any statement about what it means, but here's what the comparison looks like.




Selecting the gear ratio
5th Gear

We started testing in 5th gear because it's 1:1 and many people prefer using this gear. From the E9x M3, we settles on a ramp rate of 1000 RPMs per 4-seconds because it seemed perfect to eliminate the effects of inertia, and match steady state testing. So we started testing in 5th gear at 1000 RPMs/4-seconds. We obtained a reliable and repeatable 396-399 whp.




4th Gear

Next we reprogrammed the Dynapack for 4th gear but kept our 1000 RPMs/4-second ramp rate. This test gave us a reliable and repeatable 405-412 whp.




3rd Gear

We finally programmed the Dynapack for 3rd gear and still kept our 1000 RPMs/4-second ramp rate. This gave us our best results. Using 3rd gear, we obtained a very consistent 418-420 whp.




Comparing Gear Ratio Results: 3rd to 4th

Even though we did the remainder of our testing in 3rd gear, after getting home we started comparing the different gear ratio results to see if it all made sense. It seemed very clear that the power was identical up to a certain point. Comparing 3rd to 4th gear, the power was identical from 2000-5800 RPMs.




Comparing Gear Ratio Results: 3rd to 5th

Comparing 3rd to 5th gears showed similar results. The power was identical up to a point, but afterwards they drifted apart. In the case of 3rd vs. 5th, the power was identical from 2000-4600 RPMs. The fact that the power is identical but diverges sooner than 4th gear tell us one of two things: 1) the ECU is programmed to make different amounts of power in different gears, or 2) our RPM ramp is still too fast for higher gears -- and they are experiencing the inertial effects we are trying to eliminate.

The low ramp speed makes some sense because the 5th gear diverges sooner than 4th gear. We didn't test this theory on this trip because we ran out of time. We might revisit the ramp speed test and try different values for higher gears to see if it makes a difference when the car is tuned.




Comparing Gear Ratio Results: 3rd to Steady State

During this dyno session, I wanted to test another theory floating around the F8x dyno debate threads. Will steady state testing produce significantly different results than a carefully constructed ramp test? In theory, steady state will produce significantly different results because the inertial effects of the drive train are completely eliminated. But is the theory really backed up by reality? We've done this before with the E9x M3, and found we could carefully construct a ramp test to equal steady state testing. But since this is a new car, new chassis, new engine, we thought it would be a good time to put it to test again.

Our ramp test still used 3rd gear and 1000 RPMs/4-seconds. Our steady state was 1-second for each 100 RPMs increments. At each 100 RPM intervals, the Dynapack would hold the engine for 1-second, measure the torque, then move up 100 RPMs for the next test. This is hard on the car and engine because this isn't how you drive. So we only did this test long enough to confirm or deny our previous experiments. If the results confirm, we quit...no need to continue testing to prove anything else.



The graph above clearly shows equality between our ramp test and steady state tests. The steady state test kind of falls apart at 6300 RPMs. This is almost surely because of the extra heat build up in the turbos, coolers, etc. over the ramp test. It's very important to understand: if there are inertial effects, the ramp test results will be LOWER, not HIGHER than steady state testing. So just as the E9x M3, a carefully constructed ramp test can equal the results of a steady state test, and the inertial effects of the drive train are effectively mitigated.

Last but not least, here's a complete picture of all the results from each gear and steady state tests.




Performance Results:

After the dyno results, we took the car to "Mexico" for some vBox tests. Using the same tank of 93 octane gas, we headed to Mexico for some vBox testing. We used our higher resolution vBox Sport (20 Hz sampling) for greater accuracy. We also data logged with the AIM Solo-DL for back up. We ran the car in eight identical tests: 0-135 MPH, slam on the brakes and back down to 0 MPH. Four runs were made in one direction, and four runs were made in the other direction on our Mexico roadway. There's two things running against us on these tests: 1) Street tires instead of drag radials; 2) Road was very rough, and this will definitely hurt the performance. But regardless, we made the best of it to bring some real life data to the discussion.


Using this method, we can obtain the following test results:
  • 0-100 MPH (1)
  • 1/4 Mile Drag Race (2)
  • 60-130 MPH
  • 100-0 MPH (Braking)
  • 0-100-0 MPH (3)



Notes:
  1. 0-100 MPH calculated using 1-Ft rollout as per American car magazines typical methods.
  2. Trap speed and ET calculated according to official NHRA rules with www.vboxtools.com software, not using other vBox software that only calculates vMax. Results equal drag race timeslips.
  3. Calculated by combining 0-100 MPH (1-Ft) time, plus 0.25s reaction time, plus 100-0 MPH time.
  4. Complete results and graphs for all runs are available at this location.
0-100 MPH: 9.492 Seconds




0-100 MPH (1-Ft Rollout): 9.137 Seconds




100-0 MPH: 4.182 Seconds




0-100-0 MPH: 13.319 Seconds

Back in the old days, a guy mashed the gas pedal, watched the speedometer, and mashed the brakes when he hit 100 MPH. Without a vBox or other speed logging device, you never knew if you actually hit 100 MPH, or were falling short due to speedometer error. Then you have the reaction time to hit the brakes followed by the braking time. These days, we do things a little different. A magazine will typically make many runs up to 100 MPH, and make many braking attempts until they put the best of each together to create a single 0-100-0 result. It's easy for us to do the same thing with a vBox. This will also be a great way to test the Carbon Ceramic Brakes (CCB's) for things like brake fade.

Our 0-100-0 time is taken from our quickest 0-100 MPH time (1-Ft Rollout), and our quickest 100-0 MPH time. When you put the two together, you end up with 13.319 seconds. BTW, American car magazines use a 1-Ft rollout even on these types of ET tests from 0 MPH; that's why we're using the 1-Ft rollout version. Here's a spreadsheet to show how we rate compared to some other great cars.




60-130 MPH: 10.586 Seconds




1/4 Mile Drag Race: 12.590 Seconds @ 117.850 MPH




Performance Results Summary:

The car performed flawless. All of our performance results met or exceeded expectations. All of our runs were very consistent with only one outlier or two which came on the first run as things were getting warmed up.

The braking tests are worth a special mention. Our CCB's performed better than expected. When you look at those 100-0 MPH results, the M4 gave the second quickest 100-0 on record (on that list of cars). Granted I found evidence of other cars stopping 100-0 qucker than the M4 (as quick as 3.6s), but they don't appear on this list. So to be second quickest stopping car on that list is pretty impressive. I was also impressed how consistent the 100-0's were. There was only 0.5 seconds difference from quickest to slowest brake test. As the timestamps show, runs 6 and 7 were back to back. The CCB's didn't fade a bit. Just look at the braking graphs, the line is perfectly linear and doesn't start to curve even the slightest bit. This shows the CCB's don't fade a bit under a test like this. But I did get them to fade a little at the track.

I haven't seen any bone stock 60-130 times yet, so I'll enter mine at 10.586 seconds as the first one.

Our 1/4 mile times aren't the greatest, but they're definitely in line with other magazine tests. If the road wasn't so rough, and if we had drag radials, I'm sure there's at least another 1-2 MPH we can get out of this car. I never use launch control, it's not my thing. So I'm not sure how much, if any I would improve the ET.

Anyways, these are my results for dyno and road testing. I'll be happy to answer questions about our tests, but not interested in another over/underrating debate. Thanks for reading.

Last edited by Alekshop; 09-23-2014 at 01:11 PM..
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      09-23-2014, 11:16 AM   #2
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Excellent write up, tests, and results. I wish there were shops around me like yours
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      09-23-2014, 11:19 AM   #3
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Good data... would u say that Vbox trap speed would be lower at a track?
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      09-23-2014, 11:29 AM   #4
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Quote:
Originally Posted by ASAP View Post
Good data... would u say that Vbox trap speed would be lower at a track?
We will see that on Oct 4th at the Sacramento drag strip.
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      09-23-2014, 11:31 AM   #5
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Quote:
Originally Posted by Alekshop View Post
We will see that on Oct 4th at the Sacramento drag strip.
Will you be taking drag radials?
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      09-23-2014, 11:50 AM   #6
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Quote:
Originally Posted by dmk08 View Post
Will you be taking drag radials?
No just stock tires
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      09-23-2014, 11:59 AM   #7
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420 whp, the myth, the monster...the M4!
Looks like solid work with much thought and care. Thanks for sharing!
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      09-23-2014, 12:05 PM   #8
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Thanks for sharing and thorough work!
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      09-23-2014, 12:34 PM   #9
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Avg. braking distance is 308 ft or 94 m.
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      09-23-2014, 12:57 PM   #10
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This car is FAST
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      09-23-2014, 01:04 PM   #11
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Do you have regular brakes? Or Carbon ceramic?
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      09-23-2014, 01:19 PM   #12
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Great work on all the dyno information! In your opinion what do you think the true crank hp and torque values are?
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      09-23-2014, 01:22 PM   #13
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So far tests showing under rating have out numbered all others. Everyone can speculate till blue but there is no denying this thing is a beast.

Solid test Aleks
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      09-23-2014, 01:28 PM   #14
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Lots of information to digest. Seems like all BMW petrol turbo engines do better than spec. The trap speed was not as good as someone else around here did.
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      09-23-2014, 01:38 PM   #15
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Quote:
Originally Posted by Diver View Post
Lots of information to digest. Seems like all BMW petrol turbo engines do better than spec. The trap speed was not as good as someone else around here did.
Those 275s bog the car down so bad... Even using MDM it pulls power... You better know how to drive with traction off if you want to post good times with this car, and even then the tires will continue to be the weak point.
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      09-23-2014, 01:40 PM   #16
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Quote:
Originally Posted by RingMeister01 View Post
So far tests showing under rating have out numbered all others. Everyone can speculate till blue but there is no denying this thing is a beast.

Solid test Aleks
Agree that we so far probably have more dyno results at 400+whp (with many of those in the 415-420 bracket).

But, we also have the only manufacturer and legally approved chassis dyno (MAHA) at 453-465PS at the crank. We have the K&N Superflow dyno at 380(ish)whp and a few Dynojets at 370-380whp.

Going to be interesting to see if RRI.se also puts one on their Dynapack and if they get similar results as the OP.

And as you say, we can speculate till we're blue, but there's no denying that this car thoroughly outperforms it's predecessor
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      09-23-2014, 02:19 PM   #17
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Great results and write up !
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      09-23-2014, 02:25 PM   #18
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Thanks for the data OP!

If it was 93 degrees outside during testing the F8x will be even more impressive during the cooler temps in Fall/Winter/Spring.
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      09-23-2014, 02:29 PM   #19
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Quote:
Originally Posted by 335iRlz View Post
Those 275s bog the car down so bad... Even using MDM it pulls power... You better know how to drive with traction off if you want to post good times with this car, and even then the tires will continue to be the weak point.
Definitely takes time to learn how to drive this car efficiently to squeeze every bit of performance to archive great results. Haven't done many Mexico runs and no experience at drag strip but we are working on it

On another hand it's a fun car to drive on the road course 😉
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      09-23-2014, 03:00 PM   #20
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This is information that Dinan WILL NEVER SHOW YOU !

OP thank you VERY MUCH for this post.

How I would pay to see the looks on some peoples faces after they get the Dinan piggyback and see that in reality they are not getting that much of power for that type of money they spent. Hell No !

I am sure someone down the line will crack or find a away around BMW's locked system.
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      09-23-2014, 03:06 PM   #21
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This is very useful. Many thanks for posting this information. I appreciate the transparency and your willingness to follow up on questions posed by the community. Looking forward to you hitting the track with this beast. Good luck.
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      09-23-2014, 03:25 PM   #22
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Excellent post. Loads of data, exactly what the forum needs. Thanks for posting.

Given that conventional wisdom/practice is to dyno in a gear that is 1:1 or as close as possible, the 396-399 number seems reasonable on a dynapack (reduced rotational losses, albeit slightly).

I agreed that the car is severely traction limited off the line. I don't know, however, whether DRs would significantly improve the trap speed. The ET would fall dramatically but the trap may not change a lot.
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