Mystery Solved: Complete correlation between S55 Dyno's, Simulations, and Real World

[Boss330]

Originally Posted by CanAutM3

As I have already replied to you in another thread, the chart quoted above is utterly meaningless. To be able to properly compare the power curves, you need to plot against road speed. Plotting against road speed is also not fully accurate but does provide a better visual cue than plotting against RPM. See post here.

I believe the chart below also illustrates well the important point you are trying to make regarding average power. The importance of average power is a point I have been debating with Swamp for quite a while on a variety of topics.

Thanks for the correction. I welcome these kinds of feedback because it's constructive and I learn from them (albeit a slow learner it seems... ).

It's way better than just being told I'm wrong, but not giving any real substance to why and where I'm wrong

[swamp2]

Originally Posted by P1 Motorcars

Mystery Solved: Complete correlation between S55 Dyno's, Simulations, and real-world

Let's start with some basic comments. We can then move toward some possible joint work with each others simulations.

Originally Posted by P1 Motorcars

Yet others use CarTest simulators to "prove" the dyno's are wrong instead of using real-world results to see if their simulations are right.

Completely incorrect mischaracterization of my work. Read my post.

I used a combination of real world observations and simulation to answer questions for a baseline vehicle (E92 M3 w/ M-DCT) and applied what I learned about loss and drivetrain inertia to do the same for the M4.

Originally Posted by P1 Motorcars

Here at P1 Motorcars, we wanted to take a stab at this question ourselves. We believe we can do it, and here's why: we've done this before, we have the data, AND we have the expertise to put together an accurate simulation model. As far as we can tell, most people talking about this have been talking themselves in circles and haven't done the type of work we're planning to put into this.

And P1 Motorcars does tuning and have a Dynojet and thus have an inherent conflict of interest to "prove" that dynos and in particular Dynojets are accurate. Your entire argument here begins with this proposition that chassis dynos are accurate and that is a big problem. More on that in a bit.

Originally Posted by P1 Motorcars

and vBox results...

There is ample discussion as the the accuracy of the Vbox. I trust you don't have the high end $5k system? Have a look here for one example of how the Vbox gives inaccurate results if not manually corrected (link).

Originally Posted by P1 Motorcars

Terry ran stock dynos, and JB4 tuned dynos, then he went out and ran vBox results for both. So we have two full sets of data we can use to compare against CarTest. It may be only one data point, but it's better than the prior analysis that didn't have any data points.

I prefer to answer the question about crank hp and stock vehicles. Tuned vehicles simply muddy the water. Sure, it might be an interesting project but it really isn't the best way to control unknowns.

Originally Posted by P1 Motorcars

The Maha is purported to be the most accurate dyno and can calculate drive train losses to obtain an estimate for crank horsepower. We've never tried to use a Maha dyno in CarTest before, but it seemed like a good candidate because it gives an estimate of crank horsepower instead of wheel horsepower. This seems like a good candidate to try as well.

Maha dynos have been discussed extensively in this thread. Although I do believe they are an order of magnitude higher quality, more sophisticated, more expensive and more accurate than a Dynojet, it is entirely unclear how they can measure losses with a vehicle with the transmission in neutral... Link. This thread along is 18 pages... 385 whp is not an unreasonable meausurement for the whp of the S55. Maha simply can not be trusted for engine power.

Originally Posted by P1 Motorcars

We think it's nice to know how our vBox results line up with published magazine results. That's going to tell us if we're chasing an outlier or an average M3. This is an important step because we have dyno and vBox results for the same car. If our 1/4 trap speed is an outlier, then it may mean our dyno results are an outlier too. Our methods would still be valid, but we think it's important to know if our car is an outlier or not because so many dyno's keep popping up with very similar values.

BMW M4 M-DCT: 12.1 s @ 119 mph (Car and Driver)
BMW M4 M-DCT: 12.1 s @ 119.1 mph (Motor Trend)
BMW M3 M-DCT: 12.1 s @ 117.8 mph (Motor Trend)
BMW M3 M-DCT: 12.6 s @ 117.8 mph (Terry Berger, vBox Trap Speed)

Now we know we're not chasing an outlier. Our car is very average and gave the same exact results as Motor Trend. And since so many dyno's keep showing up with very similar results, that's a pretty good sign that our dyno's are just as average as well.

You are clearly cherry picking here! The results from the magazines range from 114.9 mph (6MT) to 120.9 mph (M-DCT). From the rest of the data the 120.9 result seems like a total outlier. Here is that huge amount of data I put together. Link.

Originally Posted by P1 Motorcars

Here at P1 Motorcars, we have extensive CarTest experience. We've generated models so accurate, our methods usually produce simulations within a few tenths of a second or few tenths of a MPH of real-world results. But in order to get this accurate, your CarTest model must model everything that happened in the real-world and on the street. If you don't model the real-world conditions, then you can't expect CarTest to match your real-world results. It's the old adage: "garbage in equals garbage out." So we start with the actual car dyno's, then add the real-world conditions the car ran on the street.

I suppose you generally use your Dynojet for such immaculate comparisons? Again, as others have pointed out Dynojets for the same car varying operators, process, corrections, weather, etc. result in a 13% variation (post all corrections). A presumption that dynos are accuarate and repeatable is an enormous fundamental flaw in your approach. The proof of this was simply running the numbers from the E9X dyno database. Post and results here.

Originally Posted by P1 Motorcars

Basic CarTest Model:

• Weight: 3578 lbs. (Measured)
• Weight distribution: 52.639% front (measured)
• Wheel weight 49.85 lbs. (measured)
• Wheelbase: 110.7 inches (BMW published)
• Tires: 275-40-18 (Stock, BMW published)
• Tire Pressure: 38 PSI (measured)
• Coefficient of Rolling Resistance: Proprietary, but uses well known physics formula and tire pressure to calculate this value.
• Drag coefficient: 0.34 (BMW published)
• Frontal area: 24.65 sq-ft (BMW published)
• Height: 56.0 inches (BMW published)
• Width: 73.9 inches (BMW published)
• Ground clearance: 4.72 inches (BMW published)
• DCT shift speed: Proprietary. Based on actual measurements.
• Driver weight: 175 lbs.
• Weight of fuel: 30 lbs.

• You should use revs/mile from the tire manufacturers as it is significantly more accurate than a nominal tire size. The difference from this can be around 0.2 mph in the 1/4 mi trap. Pretty sure I learned that from another helpful member here in the forum.
• It's pretty clear CarTest can't do much with a tire pressure measurement. Since it is not documented what the feature does and it does change results, I leave it at the default. If you can't justify it's change and function you probably should not use it either.
• I always use 165 lb for the driver. This is more consistent with new EU regulations for 68 kg + 7 kg for incidentals. Of course if you wanted to model a specific case with a 200 lb driver or a 100 lb one using such numbers would obviously be better.
• DCT shift times: A nice open attitude about getting good peer reviewed results and sharing... To me this only shows more commercial bias and protectionism. DCT shift times vary by vehicle gear and level of throttle application. I typically use 50 ms.

Originally Posted by P1 Motorcars

CarTest documentation instructs us to use SAE corrected results when we use the "Driving Wheels" power for our simulations. So that's what we did.

Really SAE corrections aren't much more accurate than dynos themselves. Have you read the SAE paper on this and looked at the formulas? This is just a semi-empirical correction that takes a first stab at accounting for air density, temperature and humidity. The power results used in CarTest should be the operators best judgement of what the actual wheel power produced during a test. The point about the engine having some additional capability to correct for some of these factors amounting in a double-dip correction has been discussed extensively here on the forum and seems very likely to be occurring. So although in general an SAE corrected value is generally better than no correction, in this case it is likely an error.

Originally Posted by P1 Motorcars

Since Maha dyno's are regarded as some of the most accurate AND have the ability to calculate drivetrain losses, we decided to add a set of Maha dyno results to a separate CarTest branch model. Using the same parameters as our stock vehicle, but substituting the Maha dyno results from the crankshaft instead of wheels, we input these results into CarTest.

Again see prior comments about Maha and Maha crank numbers. These dynos are ceritified accurate from the manufacturer to be within 2% on wheel power ONLY, not crank power. This is nothing more than a massive leap of faith to use Maha crank numbers.

Originally Posted by P1 Motorcars

Adding Weather to our model:

To create a fully accurate model, we also need to capture the actual weather data because it affects performance. This is going to be tricky because there would appear no way to capture this data. That is until you realize the vBox file has everything in it to figure out the weather. The vBox file doesn't have the actual weather data, but it does have two very important pieces of information that can help us figure it out: GPS coordinates, and GPS timestamp. Here's how we converted those two pieces of information into actual weather data.

Step-1: Look up GPS coordinates on Google Earth. That would be fine if we had access to the vBox files...but we don't. We had to beg for it, and we were only given a single GPS coordinate. It's better than nothing, and in fact it's all we really need.
Step-2: Use NOAA database to find a nearby weather station. We found a weather station almost right on top of the GPS coordinate we received. And best of all, it was a high resolution, high data rate weather station and reported results every five minutes. Perfect!
Step-3: Convert GPS timestamp to local time. That's not as easy as it sounds. The verified vBox results show the GPS timestamp. First you must convert the GPS timestamp to a UTC timestamp, then convert UTC time to GMT, then convert GMT to seasonally-adjusted local time. So that's what we did.
Step-4: Now that we know exactly when and where the vBox file was generated, we can look up weather data in NOAA database for that exact location, date, and time. As luck would have it, the NOAA database contained entries for these exact timestamps.
Step-5: Not related to timestamps, but capture the slope of the vBox runs from the verified and published vBox results.

But wait...there's more! What about wind? The NOAA weather station does show wind velocity and a very rough idea of direction. We could do some vector math to convert this data to headwind/tailwind if we knew what direction the car was headed. But with a single GPS coordinate, we don't. So we had to call our data guy and ask. After he gave us the heading, we did the math based on NOAA wind speed and calculated how much headwind/tailwind was on the car at the time.

Enter all of this back into CarTest.

This is very creative and cool work. Congratulations. This COULD clearly add to simulation accuracy. However, wind is often quite a micro climate type of phenomena and typically varies in time. I would not trust the changes from this correction without 2 key things. A truly local wind measurement and some indication that the wind was steady in magnitude and direction. Since you did not have this it is pretty well just like rolling the dice...

Originally Posted by P1 Motorcars

Drive train losses:
When you use CarTest to simulate based on wheel dyno results, it bypasses the drive train losses entered into the program. But when simulating based on engine dyno results, it doesn't. So we don't need this for the Dynojet, but we do need it for the Maha results. We entered the following drive train losses into CarTest and added the same 1-ft rollout to follow the vBox verification software model:

Losses:

• 1% for auxiliaries
• 3% for the DCT
• 3% for the differential
• 3% for the axles and shafts (2)
• 10% Total

10% drive train loss might sound a little light, but here's the rationale. Rototest (RRI) dyno database tested the E9x/S65 motor and found approximately 12% drive train loss (3). I think it's a safe assumption that the DCT in the F8x M3 is at least as efficient as the DCT in the E9x M3; so let's start with the 12% loss inferred in the RRI testing. The F8x M3 has a carbon drive shaft and less rotating mass. So the losses for axles and shafts on the F8x M3 will be less than the 12% on the E9x M3. I chose 10% for this value.

Drivetrain losses are one of the larger uncertainties in this type of modeling. Drivetrain inertia is the other. See my extensive relevant post on drivetrain inertia here. I'm sure you will learn something by reading the ENTIRE thread. Anyway losses are where you can basically curve fit (cheat or tune, however, you might be accomplishing it) a lot of observed performance variation. But if you read my post concluding the car is not under rated thoroughly, even just the opening first post, you would recall that CarTest is doing something quite funky with mixing losses and inertia. You would also realize that the total % loss you type in bears little in common with the actual losses spit out from CarTest when plotting the losses. In fact for the E92 vs. F82 when "requesting" the exact same total percentage loss you can get a whopping ~50% more loss than asked for. I corresponded with the author of Car Test, Patrick Glenn, and he said to trust the graphs over the input %. This is a pretty big problem with CarTest but I found a way around it. Again read my post.

Please post your actual loss graph when using the crank power numbers and compare the % total input vs. the graph. Be seated when doing so...

You will find you have done exactly what was plaging some of my early M4 CarTest efforts. Much more loss than realistic required much more power than actual to obtain realistic comparisons vs. test results.

Originally Posted by P1 Motorcars

Insoric RealPower Road Testing:
Recently the Swiss company Insoric came to our attention with a brilliantly conceived device that attaches to your wheel, captures acceleration and deceleration, and converts this data into wheel horsepower and crank horsepower. Their idea to calculate crank horsepower based on measuring drivetrain losses through physics equations of wind and rolling resistance is simply brilliant.

Here at P1 Motorcars we were so intrigued by this idea we immediately contacted Insoric to ask if we could become their US Distributor.
...
Look what's missing:

• Let's start with capturing velocity: Using a gyroscope and accelerometer to capture and approximate velocity isn't accurate. At the end of the day, it's just an approximation. This is exactly how your BMW Performance Steering wheel works. It's never going to be accurate compared to using a GPS that can capture velocity within a few hundredths of a MPH.
• SAE/STD/DIN correction.: All of the horsepower correction formulae require temperature, barometer, and humidity (or wet-bulb/dry-bulb). Humidity is missing from the input parameters. Their correction equations will never be accurate.
• Calculating losses due to wheel weight ("equivalent mass"): Like CarTest, Insoric has a one-size-fits-all approach to calculating wheel losses. They don't have separate input for front/rear tires, and they always seem to assume four wheels (no big deal, just pointing it out). To get more accurate calculations, one would like to know the wheel and tire dimensions, along with approximate weight distributions for each.
• Calculating losses due to aerodynamics: Without frontal area and drag coefficient, these losses can't be calculated. Insoric RealSpeed doesn't seem to account for this very significant force.
• Calculating losses due to rolling resistance: This is another of those areas where Insoric dropped the ball. The best physics-based calculations here require tire pressure, and for Insoric that is missing.
• Calculating losses (or increases) due to slope. Insoric says to run their product on a flat road or else it's not accurate. Without a GPS, you don't have this data. So just stay on a flat road when testing.

These are some very significant deficiencies in the Insoric RealPower product that will affect its accuracy. No matter how brilliant the idea, it's clearly not going to be nearly accurate enough. But here's the real rub from Insoric. Based on the hardware they described, Insoric RealPower should be cheap: maybe $100 - $200, $500 at the most. But the Insoric RealPower comes with a hefty $5200 USD price tag. That's right, $5200 for an electronic gyroscope/accelerometer ($2.00), a microcontroller ($4.00), and SD card writer ($4.00). With packaging, I doubt there's more than $20 bill of materials on the device itself, but it carries a $5200 USD price tag. That's definitely not worth it. No matter how brilliant an idea, the execution is poor and the price is too high. Let's keep looking.

Wow, talk about speculation. This is the only system on the market that does do measurements for losses. It looks to have significant promise beyond clumsy things like your shops Dynojet. I too have inquired with them on questions about how the system works. Some specific reasons your criticism are not entirely valid are:

• You do not know what sensor they use for capturing velocity or how accurate its specs or real world capabilities are. PURE SPECULATION. Shame on you.
• The system appears to be lumping in losses from various sources, wheels, aero and drivetrain. Ultimately those can be summed (just like the total loss in CarTest graphs) and converted to a total net loss. At least the system actually measures loss in some way. What does your wonderful Dynojet do here?
• The basic tire loss methodology from CarTest DOES NOT require tire pressure. I have documented the math behind this method and validated that this is what CarTest is doing here.

Originally Posted by P1 Motorcars

Remember what we said at the beginning: garbage in equals garbage out.

At the moment the biggest deficiency here in your work is the case with using crank power and losses. Graph the losses, they are WAY too high and this completely removes this as a valid data point here.

Originally Posted by P1 Motorcars

This confirms Terry's account of adding additional tuning after the original dyno session and explains our CarTest simulation underestimating the JB4 Tuned results.

Again although I do not want to get into the discussion about tuned vehicles here, this is 100% pure unadulterated speculation.

Originally Posted by P1 Motorcars

We can't explain why the previous CarTest models didn't produce results that match the real-world.

There are two different approaches to "matching" results with simulation. One can try to match a single very specific case. When doing so one may be able to obtain some excellent correspondence to that particular run. However, things vary, results vary and traps for any given car will vary. My approach is to capture a typical M4 and my results are within 0.7 mph trap speed of the average magazine reported trap speed. (link, deep into my primary thread on this topic..). There are advantages and disadvantages to each method. However, there is nothing "wrong" with any reported results in the large database of M4 (and competitor) data I put together. You can not match all of them with the amount of uncertainty in each. Kind of getting philosophical here...

Originally Posted by P1 Motorcars

we identified what we thought were two significant flaws in the original article: 1) The author repeatedly uses himself as his own reference or "proof" of something. That's not how science is performed. 2) When the author tried to mimic our P1 Motorcars "real-world" approach, he reported simulations 3-4 MPH higher than the real-world. But instead of suspecting fault in his own simulation models, he continued to have overconfidence in his CarTest model and believed the simulations were right...and the dyno's were wrong. Again, not very scientific.

What does statement #1 even mean? It is nonesense.

I will re-examine your point number 2 with my use of whp in CarTest. I am happy to post all of my inputs for this.

But again, dynos are EMPIRICALLY PROVEN to NOT OFFER ACCURACY NOR REPEATABILITY. Does that mean the NO single dyno run is "correct"? No, it doesn't. However, it very likely means that such a lucky run would then be right for the wrong reason!

Originally Posted by P1 Motorcars

There's no mystery here. The mystery is solved. The Dynojet numbers are real, and this is the performance you can expect on the dyno, on the simulation, on the street, and on the vBox dyno. Everything seems to match and there doesn't appear to be any consistencies. Case closed...for now.

Hardly. Before this effort, in which I have identified one very significant flaw and many other minor ones there was the following body of evidence

1. Chassis dynos
2. In-situ, wheel based, Insoric dyno
3. Maha whp results
4. Trap speeds (and other performance metrics)
5. BMW stated crank hp
6. Simulation
7. Legal requirements

Every single piece of this evidence points toward no or a minor (<5%) under rating..... except..... #1, chassis dynos.

Let's continue to amicably share more inputs and outputs and make some progress together.

[solstice]

Average power is as double compensation a solid argument IMO and would have been a reasonable way to explain inconsistencies between the metrics as high trap speed and low dyno results. Say that the car trapped 120 mph but only dynod 370 whp. However when all commonly used metrics and calculations match and seemingly provide good physics models for the S55 you have to ask: what's the purpose and why bother? Most physics and mathematics formulas are models of reality that works but are not perfect in including all parameters. To me this quest to prove stated hp is purely academic and rather obscure at this point.

[swamp2]

Originally Posted by CanAutM3

As I have already replied to you in another thread, the chart quoted above is utterly meaningless. To be able to properly compare the power curves, you need to plot against road speed. Plotting against road speed is also not fully accurate but does provide a better visual cue than plotting against RPM. See post here.

I believe the chart below also illustrates well the important point you are trying to make regarding average power. The importance of average power is a point I have been debating with Swamp for quite a while on a variety of topics.

Preface: We entirely agree here on the big picture...

However, vs. road speed is only slightly more useful than plotting vs. rpm. Please recall my post on this topic. Simulation takes us beyond both rpm and road speed and cuts to the chase really showing how much TIME averaged power is different.

What would the difference be between the existing S55 M4 and a theoretical one with the exact same peak power but a power delivery curve like the S65 (i.e. almost perfectly linear)? This is a trivial question to answer by simulation, of course. The difference is a 3 mph difference is trap speed. Again IDENTICAL peak power.

Original post with full results from this simulation.

Thus when we try to compare the M4 to other cars with only the same weight and PEAK hp the other car will need about 30 hp more the trap the same speed if it has a very linear power curve. Knee shaped curves will be something different but the same principle and effect exists.

The shape of the power curve matters and dynos do not generally capture this well. The factory stated power curves do...

[swamp2]

Originally Posted by solstice

To me this quest to prove stated hp is purely academic and rather obscure at this point.

This is about both whp and crank hp.

Put the S55 on a factory (multi million dollar) engine dyno FACILITY and what will the result be? This is extremely interesting to me and many others here.

And again, if the topic is not interesting don't bother following it. Didn't we have this exact exchange prior...

That being said I can see how this argument will be quite obscure to most folks.

[P1 Motorcars]

Originally Posted by Boss330

And the answer to your question on trap speed difference is really as simple as average power in each gear during the 1/4 mile run. I will paste one of my other posts on this topic, which compares to a C7 and not the E9x, but the point is the same:

Quite possibly correct.

Originally Posted by Boss330

http://eur-lex.europa.eu/resource.ht...C_1&format=PDF

Interesting, I already have that document. It's the EEC version of SAE Correction. It's the same formula as SAE Correction, but doesn't have engine efficiency factored in. Otherwise, they are identical formulas.

Before I get into the meat of the compliance question, let me make a few observations about the document itself.

• That document was ratified in 1980. Does anybody here believe that every single car manufactured since 1980 has complied engine output +/- 5% in all of Europe?
• The original compliance document (70/156/EEC), section-10 was ratified in 1970. According to this document, it was superceded in 1980 and again in 1997.
• Section 1.1.3 appears to allow self-certification. That contradicts what I've been reading here.

Here's what the compliance section says:

8. TOLERANCES FOR MEASURING THE NET POWER
8.1. The net power indicated by the manufacturer for the type of engine shall be accepted if it does not differ by more than ± 2 % for maximum power and more than ± 4 % at, the other measurement points on the curve with a tolerance of± 1,5 % for engine speed, from the values measured by the technical service on the engine submitted for testing.
8.2. During the tests to verify conformity of production the power shall be measured at two engine speeds S1 and S2 corresponding respectively to the measurement points ofmaximum power and maximum torque accepted for type approval. At these two engine speeds, which are subject to a tolerance of± 5 %, the net power measured at at least one point within the ranges S1 ± 5 % and S2 ± 5 % shall not differ by more than ± 5 % from the approval figure.

Section 8.2 is the compliance section that I'm pretty sure you and the other guys are talking about. But look very closely at what it says. It says power will be measured at two points (maxTQ and maxHP), and it must be +/- 5% at ONE of those points...not BOTH! That means BMW could comply with this simply be getting maxTQ within +/- 5% and still jack up the HP to whatever they want.

[Boss330]

Originally Posted by P1 Motorcars

Interesting, I already have that document. It's the EEC version of SAE Correction. It's the same formula as SAE Correction, but doesn't have engine efficiency factored in. Otherwise, they are identical formulas.

Before I get into the meat of the compliance question, let me make a few observations about the document itself.

• That document was ratified in 1980. Does anybody here believe that every single car manufactured since 1980 has complied engine output +/- 5% in all of Europe?
• The original compliance document (70/156/EEC), section-10 was ratified in 1970. According to this document, it was superceded in 1980 and again in 1997.
• Section 1.1.3 appears to allow self-certification. That contradicts what I've been reading here.

Here's what the compliance section says:

8. TOLERANCES FOR MEASURING THE NET POWER
8.1. The net power indicated by the manufacturer for the type of engine shall be accepted if it does not differ by more than ± 2 % for maximum power and more than ± 4 % at, the other measurement points on the curve with a tolerance of± 1,5 % for engine speed, from the values measured by the technical service on the engine submitted for testing.
8.2. During the tests to verify conformity of production the power shall be measured at two engine speeds S1 and S2 corresponding respectively to the measurement points ofmaximum power and maximum torque accepted for type approval. At these two engine speeds, which are subject to a tolerance of± 5 %, the net power measured at at least one point within the ranges S1 ± 5 % and S2 ± 5 % shall not differ by more than ± 5 % from the approval figure.

Section 8.2 is the compliance section that I'm pretty sure you and the other guys are talking about. But look very closely at what it says. It says power will be measured at two points (maxTQ and maxHP), and it must be +/- 5% at ONE of those points...not BOTH! That means BMW could comply with this simply be getting maxTQ within +/- 5% and still jack up the HP to whatever they want.

It was also amended in 1999 by Commission Directive 1999/99/EC

Section 1.1.3 refers to a "Tecnical Service". By EU definitions a technical service is a independent testing organization that has been approved to do certain tests.

A technical service is an organisation or body designated by the approval authority of a Member State as a testing laboratory to carry out tests, or as a conformity assessment body to carry out the initial assessment and other tests or inspections, on behalf of the approval authority.

A technical service is NOT the manufacturer.

Here is a list of all approved technical services:

http://ec.europa.eu/enterprise/secto...s/index_en.htm

As regards data points gathered during certification I refer you to section 5.4:

Test procedure
Measurements shall be taken at a sufficient number of engine speeds
to define correctly the power curve completely between the lowest
and the highest engine speeds recommended by the manufacturer.
This range of speeds shall include the speed of revolution at which
the engine produces its maximum power. For each speed, the average
of at least two stabilized measurements is to be determined.

Again, I will mention that any understatement (beyond what is allowed as a tolerance) on BMW's behalf will have to involve one of two scenarios:

-BMW presenting a tampered version of the engine and software for type approval testing. Implying a false and misleading conduct on their behalf
-The technical service having to be "in on the lie" and stating other numbers than they measured. This would be corruption and gross negligence. Potentially risking their certification and loosing multi million dollars of business...

(Possibly a combination of the two scenarios above)

[swamp2]

Originally Posted by P1 Motorcars

Here's what the compliance section says:

8. TOLERANCES FOR MEASURING THE NET POWER
8.1. The net power indicated by the manufacturer for the type of engine shall be accepted if it does not differ by more than ± 2 % for maximum power and more than ± 4 % at, the other measurement points on the curve with a tolerance of± 1,5 % for engine speed, from the values measured by the technical service on the engine submitted for testing.
8.2. During the tests to verify conformity of production the power shall be measured at two engine speeds S1 and S2 corresponding respectively to the measurement points ofmaximum power and maximum torque accepted for type approval. At these two engine speeds, which are subject to a tolerance of± 5 %, the net power measured at at least one point within the ranges S1 ± 5 % and S2 ± 5 % shall not differ by more than ± 5 % from the approval figure.

Section 8.2 is the compliance section that I'm pretty sure you and the other guys are talking about. But look very closely at what it says. It says power will be measured at two points (maxTQ and maxHP), and it must be +/- 5% at ONE of those points...not BOTH! That means BMW could comply with this simply be getting maxTQ within +/- 5% and still jack up the HP to whatever they want.

Your conclusion is clearly incorrect. They must adhere to BOTH 8.1 and 8.2. 8.1 states +/- 2% for maximum power (AND another requirement about the entire curve).

Either way, as you noted, this is a rule that certainly can and almost for sure has been broken. It is not proof, just another piece of evidence.

On a related note, its pretty clear to me that SAE "Certified Power" (J1394 and J1995), to which not at all a majority of OEMs adhere to (GM is one of the better), is a very stringent requirement to be within 1% and GM vehicle that meet this requirement are, in my evaluation, incredibly likely to fall within the rules of the certification.

[solstice]

Originally Posted by swamp2

Your conclusion is clearly incorrect. They must adhere to BOTH 8.1 and 8.2. 8.1 states +/- 2% for maximum power (AND another requirement about the entire curve).

Either way, as you noted, this is a rule that certainly can and almost for sure has been broken. It is not proof, just another piece of evidence.

On a related note, its pretty clear to me that SAE "Certified Power" (J1394 and J1995), to which not at all a majority of OEMs adhere to (GM is one of the better), is a very stringent requirement to be within 1% and GM vehicle that meet this requirement are, in my evaluation, incredibly likely to fall within the rules of the certification.

While I agree with the conclusion and methodology of the OP in this thread I think the interpretation of the certification is reaching at best and most likely wrong. Surely it could be used as a loophole if BMW did the certification but with an independent certification firm I see it as highly unlikely. There's no need for the OP to try to eliminate this piece of "evidence" IMO since none of the specific engines that has been dynod or trapped has been tested by regulators. It's not evidence at all to me, just law.

[Boss330]

Originally Posted by swamp2

Your conclusion is clearly incorrect. They must adhere to BOTH 8.1 and 8.2. 8.1 states +/- 2% for maximum power (AND another requirement about the entire curve).

Either way, as you noted, this is a rule that certainly can and almost for sure has been broken. It is not proof, just another piece of evidence.

On a related note, its pretty clear to me that SAE "Certified Power" (J1394 and J1995), to which not at all a majority of OEMs adhere to (GM is one of the better), is a very stringent requirement to be within 1% and GM vehicle that meet this requirement are, in my evaluation, incredibly likely to fall within the rules of the certification.

Agree. Section 8.1 and 8.2 clearly says that both HP and TQ is to be measured and checked for conformity of production.

Also, as I pointed out previously, the testing is required to take enough data points as needed to chart the power curve, throughout the complete rev range.

I'm also a bit surprised that the OP asked how it could be explained that the F8x could trap that much faster than the E9x with only 11hp more... The point about average power seems not to have been considered as a factor. Considering the background and work put in the OP, it seems strange that the difference in power curves between the S55 and S65, hasn't been evaluated and considered as a possible contributing factor in trap speeds?!

[Boss330]

Originally Posted by solstice

While I agree with the conclusion and methodology of the OP in this thread I think the interpretation of the certification is reaching at best and most likely wrong. Surely it could be used as a loophole if BMW did the certification but with an independent certification firm I see it as highly unlikely. There's no need for the OP to try to eliminate this piece of "evidence" IMO since none of the specific engines that has been dynod or trapped has been tested by regulators. It's not evidence at all to me, just law.

So you are saying that BMW doesn't adhere to type approved specs in production cars?

If they don't, then that is just as much a breach of type approval legislation as the previous examples we have discussed. This would be a serious breach of conformity of production requirements.

Legal requirements placed on the manufacturer isn't just law. It's law with serious consequences for the manufacturer if they are found to deliberately breach it. That should be considered one piece of evidence towards compliance.

[solstice]

Originally Posted by Boss330

So you are saying that BMW doesn't adhere to type approved specs in production cars?

If they don't, then that is just as much a breach of type approval legislation as the previous examples we have discussed. This would be a serious breach of conformity of production requirements.

Legal requirements placed on the manufacturer isn't just law. It's law with serious consequences for the manufacturer if they are found to deliberately breach it. That should be considered one piece of evidence towards compliance.

I'm saying that the cars that has been trapped and dynod has not been tested by regulators thereby I do not regard the regulation or the methodology as evidence of their crank hp. I regard measured and calculated power as real evidence.

[Boss330]

Originally Posted by solstice

I'm saying that the cars that has been trapped and dynod has not been tested by regulators thereby I do not regard the regulation or the methodology as evidence of their crank hp. I regard measured and calculated power as real evidence.

I see.

But be aware that this means BMW deliberately misleads type approval authorities. There is a requirement that the cars in production comply with the type approved model. No if or but, it has to comply and there are specific requirements for conformity of production in place...

If it doesn't, then BMW are involved in a pretty serious deception of EU authorities...

Measured power on which dyno? The MAHA that is certified to measure WHP with a 2% tolerance, or some of the others that show a 10-15% variation?

And calculated power, by whom? Swamp or P1? And why are you relying on one of them and not the others calculations?

[solstice]

Originally Posted by Boss330

I see.

But be aware that this means BMW deliberately misleads type approval authorities. There is a requirement that the cars in production comply with the type approved model. No if or but, it has to comply and there are specific requirements for conformity of production in place...

If it doesn't, then BMW are involved in a pretty serious deception of EU authorities...

That's your conclusion not mine. I can see other possibilities in difference between lab vs real world application etc. but it really doesn't matter, my point is that it is not logic to use the regulation as evidence of a suspected and measured real world deviation to the stated lab numbers. I'm NOT accusing BMW of wrong doing here just looking at where all data is pointing in terms of power generated in the real world. I'm mildly interested in the power made by the car and not if a regulatory breech is committed. I don't really care about that.

Btw I think your average power theory is valid and I would have easily agreed to it as an explanation if the car dynod low and trapped high. However the car is now dynod at level that matches it's trap speed. Your and swamp's problem is to explain the high dyno numbers. Dynos has less parameters than trap speed and they measure power, they are the strongest individual evidence of under rating IMO. Forget trying to explain the trap speed since it matches the dyno runs and vbox data. The regulation deep dive is also not bringing anything to the table in terms of explaining measured and calculated data. It's just distraction which will convince no one that the dynos are wrong.

[Boss330]

Originally Posted by solstice

That's your conclusion not mine. I can see other possibilities in difference between lab vs real world application etc. but it really doesn't matter, my point is that it is not logic to use the regulation as evidence of a suspected and measured real world deviation to the stated lab numbers. I'm NOT accusing BMW of wrong doing here just looking at where all data is pointing in terms of power generated in the real world. I'm mildly interested in the power made by the car and not if a regulatory breech is committed. I don't really care about that.

Btw I think your average power theory is valid and I would have easily agreed to it as an explanation if the car dynod low and trapped high. However the car is now dynod at level that matches it's trap speed. Your and swamp's problem is to explain the high dyno numbers. Dynos has less parameters than trap speed and they measure power, they are the strongest individual evidence of under rating IMO. Forget trying to explain the trap speed since it matches the dyno runs and vbox data. The regulation deep dive is also not bringing anything to the table in terms of explaining measured and calculated data. It's just distraction which will convince no one that the dynos are wrong.

Loopholes and differences between dyno and real world is of course a possibility. But a difference that amounts to a 60-70hp difference? I find that really hard to believe.


And what would those differences between dyno and in car consist of?

Same DME
Same engine
Same intake
Same exhaust
Same ancilliaries

This leaves us with the engine not being in the engine bay, optimal climatic conditions in a air conditioned dyno room and no heat soak...

And if we can't point to any relevant differences between dyno and real world that accounts for 60-70hp difference, then how else can we explain such a large difference then that BMW deliberately deceives EU?

And I also believe that if we look at the average power and trap speeds and compare that with cars trapping similar to the F8x, we must conclude that the S55 can't be significantly underrated... Unless my C7 vs F8x comparisons are completely flawed and meaningless of course...


And, no. The car is dynod at a WHP level that does NOT match it's trap speed!

With the average power that the dyno results show, it should trap much higher than the C7 for instance!

Legal requirements might be distractions to you, but it's actually what the manufacturer has to comply with. That IS a major part of being a auto manufacturer today and cannot be disregarded as evidence!

Finally, I would say that people who swear by the dyno results must also explain the 10-15% variation in dyno results...

And why disregard the MAHA dyno that is CERTIFIED to measure WHP with a 2% accuracy? Or the INSORIC?


-The car traps just as it should according to it's stated average power from BMW
-The car traps similarly to the C7 Corvette that peaks at 460hp, but has a average power just a tad lower than the S55
-The MAHA has measured 365whp
-Insoric has measured 449hp at the crank (within 5%)
-Dynojets have shown a 13% variation in S65 testing

Trap speeds point to around 425 in average power
Dynos show a wide variation in results and are not universally regarded as proof of crank hp, nor to be reliable in measuring .


And, remember that the OP (P1) didn't take into consideration average power and clearly didn't understand how a engine with only 11hp more could trap that much faster than the E9x. When I replied with average power and how that compared with the C7, the OP replied that this "quite possibly" could explain the trap speeds... Shouldn't that at least give a pause of thought on the OP's claims? How could he have missed the shape of the power curve of the S55 and the significance that might have on trap speeds?

[swamp2]

Originally Posted by Boss330

-Insoric has measured 449hp at the crank (within 5%)

Do they claim a 5% accuracy on crank numbers?

And to add further clarification to that it was noted that their best guess was that a small, likely unrealistic/noise related peak in the resutls meant that the measured number was more like ~434 hp. Graphs and discussion here.

[Boss330]

Originally Posted by swamp2

Do they claim a 5% accuracy on crank numbers?

And to add further clarification to that it was noted that their best guess was that a small, likely unrealistic/noise related peak in the resutls meant that the measured number was more like ~434 hp. Graphs and discussion here.

Sorry about my sloppy posting...

I meant that the 449PS was within 5% of the factory claimed 431PS

But I see that wasn't really what I wrote, but in my head it made sense...



To add to the "INSORIC database":

In the last edition of Auto Bild Sportscars they do a Supertest of the Lambo Huracan. They get 631PS/575Nm vs a claimed 610PS/560Nm, noting that it's "within tolerance".

[swamp2]

There is also a key follow on question for the OP:

How much whp and crank hp is the car making? Do you have any uncertainty bounds on your predictions? After pages of analysis this was never made quite crystal clear.

Are the conclusions from your efforts consistent across all cases for either crank or wheel power?

Again my claim/theory is the the crank hp is 425 hp (as stated by BMW) or at worst case 5% under rated.

[swamp2]

Originally Posted by Boss330

Sorry about my sloppy posting...

I meant that the 449PS was within 5% of the factory claimed 431PS

But I see that wasn't really what I wrote, but in my head it made sense...

I didn't think that was sloppy, I was just adding some additional clarity.

Originally Posted by Boss330

To add to the "INSORIC database":

In the last edition of Auto Bild Sportscars they do a Supertest of the Lambo Huracan. They get 631PS/575Nm vs a claimed 610PS/560Nm, noting that it's "within tolerance".

That is 3% accuracy comparison test vs. manufacturers claim.

Perhaps it would be valuable for those doubting the accuracy of the Insoric system for you to compile a short list of its published test results? A useful format IMO would simply be vehicle, manufacturers claim, Insoric test, % deviation. We've discussed quite a few of them already and their success (at least judged by this particular metric) has been quite impressive. That being said it would also be useful to have multiple parties test identical vehicles. That would be a similar kind of "stress test" similar to the data that supports my claims about the significant variation in chassis dynos. Last but not least such a "database" post may or may not belong here in the thread...

[swamp2]

Also for all of those discussing the Stingray vs. the M4 I covered this in my OP on the topic. The M4 besting the higher power car (in 7MT) is entirely consistent with simulation. However, the automatics trans car has been shown to get off the line really well giving it the performance edge.

Again, POWER DELIVERY...

Link.

[CanAutM3]

Originally Posted by Boss330

And why disregard the MAHA dyno that is CERTIFIED to measure WHP with a 2% accuracy?

Yet the Maha dyno showed 465ps at the crank. That is 34ps more than the official rating, or 7.8%.

As I posted more than once, the WHP, or P-rad, number obtained on a Maha dyno cannot be used for comparison. Only the crank power number is really valid for comparison.

That being said, I still believe that there is no "underrating" per say. I am still convinced that the S55 (and other FI engines) behave differently on chassis dynos compared to the official test protocol on bench dynos.

[CanAutM3]

Originally Posted by swamp2

Preface: We entirely agree here on the big picture...

However, vs. road speed is only slightly more useful than plotting vs. rpm. Please recall my post on this topic. Simulation takes us beyond both rpm and road speed and cuts to the chase really showing how much TIME averaged power is different.

What would the difference be between the existing S55 M4 and a theoretical one with the exact same peak power but a power delivery curve like the S65 (i.e. almost perfectly linear)? This is a trivial question to answer by simulation, of course. The difference is a 3 mph difference is trap speed. Again IDENTICAL peak power.

Original post with full results from this simulation.

Thus when we try to compare the M4 to other cars with only the same weight and PEAK hp the other car will need about 30 hp more the trap the same speed if it has a very linear power curve. Knee shaped curves will be something different but the same principle and effect exists.

The shape of the power curve matters and dynos do not generally capture this well. The factory stated power curves do...

Agreed, a full fledged simulation will yield much better results. But it is quite time consuming.

However, in less than 5 minutes, plotting against road speed does graphically nicely show how much more a power-train pulls at any given road speed compared to another one (all other parameters being equal).

However, plotting against RPM does not tell you much at all.