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F10 / F11 (2011 - Current)
The new chapter in the highly successful story of the BMW 5 Series Sedan (F10) and wagon (F11)

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  #1  
Old 02-11-2013, 04:55 PM
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cordoor cordoor is online now
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535i probably only has 300 hp/300 tq

This is a follow up to the other thread that discussed how underrated (if any) the hp and tq are on the 535i.

I bit the bullet and paid $12 for the NxGTR sim software. You can read about the software here: http://www.nxgtrsim.com

I wanted to see if the 8 speed transmission made as big of a difference as I thought it would when compared against the 6 speed of other vehicles used to guess the 535i's true hp.

It turns out, the 8 speed makes a bigger difference than I thought.

I basically inputted all of the information I knew about the 535i automatic, my weight of 185 pounds, and ran it. The results were very much inline with actual reported track times from actual 535i owners.

Here are the results:

Time to Speed
0-30 mph: 1.873
0-60 mph: 5.424
0-100 mph: 13.83
0-200 kmh: 22.85

Time to Distance
0-100 m: 5.887 @ 63.2 mph
1/8 Mile: 8.997 @ 81 mph
1/4 Mile: 13.94 @ 100.4 mph
0-1 KM: 25.46 @ 129.5 mph

Top Speed
172.93 @ 96.92 s

At the end of the day, while horsepower is cool, it is not everything.

I've attached screen shots of the settings I plugged into the software. Not shown in any of these screen shots is my 185 pound weight, which was used in the simulation. Please let me know if you see any errors in what I plugged in. I believe I was accurate.
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Last edited by cordoor; 02-11-2013 at 05:55 PM. Reason: Wrong engine and results screenshots
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  #2  
Old 02-12-2013, 12:18 AM
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Die Wolfe Die Wolfe is offline
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Wow, that's awesome info to know...thanks man!
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  #3  
Old 02-12-2013, 12:50 AM
RambleJ RambleJ is offline
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But a 2004 mustang also gets 100mph in the 1/4 mile so we have to have 340hp

I keed I keed

Yes our cars are close to what they are rated.. We cannot compare any other N55s to our f10s, the drivetrain is different and so is our output.
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  #4  
Old 02-12-2013, 01:17 AM
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mryakanisachoad mryakanisachoad is offline
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The 8 speed auto is a gem.

I think it's one of the most important automotive milestones in years.

I've read that it can be built to handle over 1000 ft. lbs of torque while keeping all shifting specifications. An engineering masterpiece.

Last edited by mryakanisachoad; 02-12-2013 at 08:00 AM.
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  #5  
Old 02-12-2013, 03:27 AM
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K-A K-A is offline
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We still have unbroken-in N55's dyno'ing in the 266-280 RWHP range (Insideline got 277 RWHP/283 RWTQ, and on a thread I posted in the F30 section a Member said he saw an N55 dyno at 268 HP).

To add to that, here's an interesting link to an N55 VS N54 dyno comparo:

http://www.automobilemag.com/reviews.../photo_01.html

What's very interesting about that dyno is it recorded 266 RWHP on the N55, but a whopping 302 lbs of RWTQ.

I guess what really matters is a pretty standard trap speed of 100 MPH and a pretty solid dyno base of 27x RWHP (especially with a broken in motor). The "guess" is what the drivetrain loss % is.

The 8-Speed is clearly a very efficient force to get power down, and factoring in weight/trap speed/dyno, you have two options to get a 4100 lb car to a 99-101 trap: Very little drivetrain loss off of 27x RWHP, or 27x RWHP and a 15-18% drivetrain loss (which would get crank HP to levels that "make more sense" to get a 4100 lb car to trap 100-ish MPH, i.e around 325 HP).

Anyone know what a 535i 6-Speed Manual traps? That could answer a lot of questions as to whether the physic defying 300 HP/4100 lb/99-101 MPH Trap Speed is due to a super efficient auto that gets the most out of a 300-ish crank HP, or if the car is making a more "standard drivetrain loss" off of its documented RWHP numbers, thus taking it healthily over 300 HP.
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  #6  
Old 02-12-2013, 06:31 AM
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cordoor cordoor is online now
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I thought the physics based simulation that accounts for all of that plus more would be sufficient evidence to show the vehicle has 300 hp, 300 tq flat (notice I actually customized the torque curve to be close to what it actually is), a super efficient drive train (calculated by the software to be 16%), and that an 8 speed gear box and tight gearing makes a world of difference in the vehicles performance.

I wasted a few hours of work yesterday (even though I'm on a tight deadline to complete something by Thursday, but I own the place so I guess I can "goof off" if I want. LOL) playing around with the sim and verifying it is accurate and I am convinced that it is. It is extremely accurate.

If you'd like, I can post some screen shots of various tweaks to the vehicle so you can see how a max horsepower of 325 would effect performance.

At the end of the day, max hp doesn't really mean much. It's the total hp put down through the run and that is directly a result of tq x rpm over time (area under curve).

Also remember that once you get to redline in 1st, you shift up. With the 8 speed and its tight gearing, rpm drops less (significantly less) than on a 6 speed. With a 6 speed, rpm probably drops 500 or more than the 8 speed and so you are stuck with 500 rpm worth of lower horsepower. The same holds true for 3rd, so by the time you shift to 4th you've already included in the total hp under the curve for the run at least 1000 rpm worth of lower hp. This makes a huge difference (I could easily show this by putting into the sim the gearing of a 6 speed automatic).

Also very important: the 200 ms shift time of this particular 8 speed (probably because the gears are tighter). This makes loads of difference (most automatics are probably 500 ms at best) because during the shift you are putting down zero hp. Note that a dual clutch system shifts in about 150 ms. I think the average fantastic person shifting a manual can do it in 250. So even the 200 ms 8 speed vs. a 250 ms human would be a at least a tenth more of a second putting down zero hp for the manual (I suspect that right there being the reason 0-60 on this vehicle with the manual takes a tenth of a second longer).

Clearly, as seen by the sim results, 300 hp and 300 tq is sufficient to get 100 trap. After two hours of serious tweaking to see how changes to the vehicle's design would effect performance, I am convinced this is true.

I hope I'm explaining the "why" good enough. Maybe my explanation is bad.

Personally, I would be fine owning a vehicle that did 100 trap with only 300 hp and 300 tq. That's a fantastic example of how kick A BMW's engineering is, especially when it comes to transmissions.

Note to people considering waiting for the 2014 550 with the bigger N63: You will knock 3-4 tenths off your 0-60 and add about 3-4 mph to your trap. I'm sort of feeling like I should have waited but oh well.
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Last edited by cordoor; 02-12-2013 at 06:50 AM.
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  #7  
Old 02-12-2013, 07:07 AM
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mryakanisachoad mryakanisachoad is offline
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My opinion and impression is that the 535 is a fast car!!!
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Last edited by mryakanisachoad; 02-12-2013 at 07:55 AM.
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  #8  
Old 02-12-2013, 07:49 AM
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mryakanisachoad mryakanisachoad is offline
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Thumbs up

"Only" 300??? Only?????


Fear not, 535 drivers! Your cars are plenty fast as I found out last night.

Ok, so which one of my fellow festers wanted to race a silverstone II e60 m5 on the LIE heading eastbound past exit 35 @ around 8:00pm last night?


You drive a de-badged Alpine White with quad exhaust. Nice looking car! I know your car is x drive by the way she made a clean pull on a very wet road. I also know that it's probably running about +4 boost.
You pulled up next to me and paced my car for about a thousand yards. I rev matched a downshift into third and you let her rip. nice pull - you car is fast.

No racing for me - I had my son in the car and very rarely "race " to begin with...
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Last edited by mryakanisachoad; 02-12-2013 at 07:56 AM.
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  #9  
Old 02-12-2013, 08:18 AM
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dunderhi dunderhi is online now
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Thanks Codoor. I've never been a fan of rolling dynos. There's a reason why manufacturers don't use them to determine their power outputs.

I'll buy a copy of the software a see how it compares for other models.

I also need to warn you, when the 6 Series went to the higher output engine they gave it taller gearing which offsets some of the acceleration gains.
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  #10  
Old 02-12-2013, 08:44 AM
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cordoor cordoor is online now
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Quote:
Originally Posted by dunderhi View Post
I also need to warn you, when the 6 Series went to the higher output engine they gave it taller gearing which offsets some of the acceleration gains.
And I'm sure you will spend plenty of time verifying your hypothesis using the software

I've been playing around a bit more this morning. It turns out, and this seems obvious now that I've tried it, the power curve has a greater impact on final performance than the gearbox. I've tried the following three independent adjustments:

1. Put a crappy CTS-V 6 speed auto on the 535i. The result was 0-60 in 5.672 s and 1/4 Mile in 14.31 s @ 99.5 mph. This shows that the gearbox makes a difference.

2. Put an (apparently) crappier E60 6 speed auto on the 535i. The result was 0-60 in 5.767 s and 1/4 Mile in 14.36 s @ 99.6 mph. Notice the trap speed is slightly higher than the CTS-V even though the 0-60 is not as high. Again, this adjustment was only a gearing adjustment. Gearing matters.

3. Ever so slightly adjusted the torque curve of the 535i. I adjusted *only* the portion of the torque curve after peak horsepower. Essentially, I pushed the three right-most levers up one pixel, which gave the vehicle a bit of horsepower increase at the end of the rpm band. Bumping the lever up one pixel adds about 5 torque to that particular rpm of the curve (5 is *not very much*). So this change really was seriously subtle. The result was 0-60 in 5.331 s and 1/4 Mile in 13.83 s @ 101.7 mph. This shows that area under the curve is what matters most. Note that I have the software set to using an optimal shift method, not a redline shift (an optimal shift on this transmission is probably 200 rpm before redline).

I think my third test was a bit of a cheat. With the software, when you put in max hp and max tq and their corresponding rpm's, it uses math to calculate the torque curve. On my original spec, I went in and adjusted the bottom end of the torque curve (before max hp) so that it was flat according to BMW's stated claims. I did not touch the torque curve after max hp. That's how I got the original numbers, which are probably fairly accurate.

I assume BMW has a flatter than usual torque curve because their turbo(s) are integrated right into the engine in a way that allows it to take advantage of exhaust much more quickly than traditional turbos and they are able to use exhaust during each cylinder firing cycle.

So, notice how much I was able to improve performance of the vehicle by simply nudging up the torque curve by 5 torque after peak horsepower. This makes a *huge* difference (even though I think it was cheating). What I'm trying to show here is that peak torque and peak horsepower don't tell the full story. They are more marketing than anything.

Clearly BMW could improve the performance of this vehicle much more easily by finding a way to avoid bleeding off torque after peak horsepower than they would be trying to add torque before peak horsepower (which I think would consequently increase max horsepower).

By the way, the biggest difference between the N63 in the 550i and S63 in the M5 is how the turbos are fed. They are fed much more efficiently in the S63 than they are in the N63. Here's a link that explains it: http://bit.ly/lUrGW5

I don't know if it is because the S63 turbos are fed more efficiently or not (it could simply be higher boost), but I suspect the S63 bleeds off less torque at the end of the curve than the N63 and that is where the biggest gains are. Evidence of this: The S63 in the M5 has peak horsepower from 6000-7000 rpm (with a redline of 7000 or 7200, depending on TU update or not).

Last edited by cordoor; 02-12-2013 at 08:49 AM.
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  #11  
Old 02-12-2013, 09:43 AM
SuperTerp SuperTerp is offline
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Quote:
Originally Posted by K-A View Post
To add to that, here's an interesting link to an N55 VS N54 dyno comparo:

http://www.automobilemag.com/reviews.../photo_01.html

What's very interesting about that dyno is it recorded 266 RWHP on the N55, but a whopping 302 lbs of RWTQ.
I guess if you're going to keep it bone stock its kinda neat... Vishnu is going for 700whp as week speak on their single turbo n54 [they have it at 627 at the moment]. When I see an n55 be able to pump that out I'll be in awe of that engine too.
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Old 02-22-2013, 12:52 AM
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Found this article in another forum. Don't know if anyone posted it here, but good info anyway. Enjoy


1) Trap Speed will tell you about your HP to weight.
2) ET will tell you more about traction and your launch.

Of course ET is important to true drag racers, because the winner is the one that gets there first. However, we're not necessarily true drag racers in our attempt to get a power estimate. Honestly, ask 10 guys at the track "What kind of trap speed are you running?" and 8 out of 10 will answer with their ET - to one or two decimal places even. When you say, "No, no, I meant trap speed", they will fumble with a broad estimate with NO decimal places and might even have to pull a time slip out of their pocket to check. Try this question when you're at the track; it's almost funny.

THE DYNAMICS OF TRAP SPEED VS. ET

After running lots of quarter miles, it becomes clear that how well you do in the first 100 feet of the track is KEY to a good time. The last half of the track is KEY to a good speed.

Let's use an example of a stick-shift mini-pickup that on a perfect run, gets a timeslip of 19.50 seconds at 70.00 mph in the quarter.

Imagine that the light turns green, the truck moves two feet and the engine dies for three seconds. After restarting the engine, the driver proceeds to then complete a perfect pass. His time slip would show 22.50 seconds at 69.97 mph. The ET was 3.00 seconds high but the speed was almost unaffected.. why?? It's because his racetrack was 1318 feet long instead of 1320, and in those last two feet this truck usually gains an additional 0.03 mph. However, the clocks recorded the long time. My point? Much of a great ET is made by a great launch.

Now take this truck again, and the driver leaves right on the green light. However, he misses the 3-4 shift when he's at 1250 feet. He coasts for the last 70 feet while trying to find fourth gear. Now instead of accelerating another few mph in this final 70 feet of the track, he decelerates over this distance. His timeslip; 19.51 at 67.83 mph. Note how the et is almost perfect (only off by 0.01 second) but the trap speed is way off (over 2 mph slow)! On a good run, traveling that last 70 feet at an average of 69 mph, would have taken .692 seconds. At a 68 mph avg., that 70 feet takes .682 seconds. That's why his ET only varied by .01 seconds, yet the trap speed was 'way off'. My point here: the end of the track is critical to trap speed; shift rpm, missing a gear... these are the big players.

Hopefully these examples are clear. Neither of these runs are 'perfect' runs, it's just that one has an error at the start, one at the finish and the results are obvious. The start of the track is a big player in the ET, but a small player in the mph. The end of the track is a big player in the mph, but a small player the ET.

So for the casual T-Bricks member who wants to get a HP value, you don't have to buy slicks, or wish you had a limited slip differential. You don't really need to heat the tires in the waterbox, or launch with huge power braking. As long as people get their shift rpm right and don't miss a gear, even a rookie will get the appropriate trap speed for their vehicle.. but honing the perfect ET. requires being rude to a clutch, buying steeper gears or slicks.... hey, we're trying to make this recreational.

OPTIMIZING SPEED

If your goal is to get a good trap speed, what are your options? More power, of course - and less weight is obvious (but it will come out in the power calculations as no increase in power). Shift rpm chosen (auto or manual) and the time it takes you to shift (with a manual) are probably the most important tools you've got. Try different shift points to maximize your trap speed. Reduce rolling resistance by pumping up all tires to their rated pressure. Some people think that running lower pressure might help the traction in the rear, though. Of course more traction will help et, but with most street tires, running street tires within 5 psi of rated pressure will provide you with maximum traction in the first place.


REACTION TIME

The ET clocks don't start until you've actually moved around 8 inches (this is called the rollout)... so don't worry about trying to leave right on the green light. You could wait 5 seconds after the light turned green, and still get a 19.50 timeslip in our truck example above. Your timeslip does show a separate calculated time, the "Reaction Time", which in this case would be 5 seconds. That is the time from the light turning green until you rolled out of the starting zone. It's not a big thing for our discussion here.

THE LAUNCH

For the most part, a decrease in ET is accompanied by an increase in trap speed, but don't go overboard on the launch in your zest to rule the world. Just try to get smartly underway without spinning the tires much at all. Traction levels usually drop a solid 0.10 g when the tires start spinning.

THE HP FORMULA

Here's the formula to use to calculate HP:

Net HP = Weight in pounds* (Speed in MPH/228.4)^3

As an example, Car & Driver tested the 744 Turbo in their June 1990 issue. The car weighed 3,081 lb. without the driver.. the 'race weight' was 3,231 lb. The car ran a 15.7 second quarter at 86 mph. Let's plug it in to the formula:

HP = 3231 * (86/228.4)^3
HP = 172 Net

Volvo rated this at 162 Net. We come out a little high. Or does Volvo underrate a little? I'll say this - I've used this formula for years and that's how the 228.4 was honed - actual experience from cars that had actual power curves - and when I use it on Volvos it tends to always come out a few percent higher than the factory rating. This could simply be that Volvo underrates just a little.

Still, for such a simple formula and such a simple test, it's surprising how accurate this can be. And the best thing is - there's no arguing the numbers on a timeslip. There are always differences between a DynoJet and an Eddy Current Dyno, or G-Tech numbers, but every setup is done by someone different and subject to error. The quarter mile is arguably the best comparison a diversely located group like Turbobricks will ever have. The only real difference to argue about is the altitude of the track! You can compare ET and mph all day and have a good discussion.

HANDY RULE OF THUMB

Once you have a baseline, you should probably use a rule of thumb that each additional 6 HP will give you another mph. That's for a 3200 lb car that runs 88 mph. If you want the real formula for different weights or speeds, here it is:

HP for another mph above "X" speed: = Wt * (((X+1)^3-X^3) / (228.4^3))

For instance a 89 mph quarter vs. an 88 mph quarter for a 3200 lb car:

HP delta = 3200 * ((89^3-88^3) / 228.4^3))

HP delta = 6.3 HP

Once you're going 110 in the quarter, it would take an additional 10 HP to go 111 mph in the 3200 lb car.

60 FOOT TIME

This is the standard measurement tool to evaluate your launch. It's the time that it took you to travel the first 60 feet of the track. Naturally, patterns emerge again after looking at lots of runs and of course these correlate best to time, not mph. Typically, most everyone's 60' time will be between 14% and 16% of their quarter mile time. If it's under 13% or over 17%, this was not your best pass.

1/8 MILE VS. 1/4 MILE

After monitoring tons of good passes, patterns emerge. Typically, the mph at the quarter is around 1.26 times of the mph at the eighth, and the time at the quarter is around 1.55 times the time at the eighth. You can use these values if you only have a 1/8 mile track and get a real good idea of the theoretical 1/4 mile.

IS MY ET TO SPEED RATIO REASONABLE?

One fact of the quarter mile is; no matter how slow or fast your car is, the mph multiplied by the ET will pretty much be the same number every time. Before the NHRA changed the way that speed is measured in 1989, the product of speed and time was around 1400. Let's calculate some easy examples of this. A 14.00 et usually resulted in a trap speed very near 100 mph. A 10.00 et meant around 140 mph. A 200 mph pass usually takes around 7.00 seconds. These are still good rules of thumb to remember, but now the product is more like 1380 for us - The example from Car and Driver above comes out at 1350. (The reason for this shift is explained below). Remember, most everyone focuses on ET so much that they'll even optimize a car for slower mph if it gets them a better ET. (Rear end gearing is one way to do this). Those guys tend to have a product closer to 1300.

RESPECT MORE SPEED - A LOT. EVEN 3 MPH.

If you look at the formula again, you'll note how trap speed shows up as the cube root of power to weight. That's critical to understanding how fast one car is over another. Let's say your car does a 90 mph quarter and the guy who raced you in the other lane ran 71 mph. After the race, he wanders over to you to say the 'race was close'. Your reply: "I could have towed you and still smote you". (This might not be the best way to make friends, but yes, it is TRUE if the cars weigh the same.)

Do the math. (90/71) cubed is 2.04. Yes, the 90 mph car has 2.04 times the power to weight of the slower car. It has 2.04 times the acceleration of the slower car. It's just that the track is a fixed length, and in accelerating to higher speeds, you use up the track quicker. You accelerated to 90 in about 20% less time than he had to accelerate to 71, right?

Bottom line; Down where most of us run, a 3 mph difference between two cars is NOT a race. It was a clear win. There's a full 10% difference between these cars.

SOME MAGAZINES SHOW THE CONSTANT AS 230.5 OR 234.0. WHERE DID YOU GET 228.4?

Some people try to correct to different things. Like Gross HP instead of Net. But most commonly, these other constants that you'll see in magazines were originally published before 1989 when the NHRA changed their lights, and the 'new' journalist doesn't realize the formula should change accordingly. Here's what I mean; previous to 1989, there were three timing lights at the end of the track; one AT the end of the quarter mile, and one 66 feet before, and one 66 feet after. The middle light was used to calculate the et of the run, and the time to travel the 132 feet at the end of the track was used to calculate the trap speed. This gave the average speed at the end of the track, but you can see what this lead to. Most of the racers stayed on the gas for an additional 66 feet past the quarter to get a consistent speed to evaluate their setup. The track's 'shut down area' of course is a fixed length, but the pro racers were starting to hit 300 mph plus by the end. In an attempt to get these guys off the gas 66 feet earlier and 'make' the cars appear slower, the NHRA stopped using the last light around August of 1989. Today, the trap speed is calculated between the light at the quarter mile and the one 66 feet before. So any timeslip after 1989 is really giving the average speed 33 feet from the finish, which is pretty close to one percent slower than before. The old constant of 230.5 became 228.4 to compensate.

CORRECTING FOR ALTITUDE

If we were dealing with non-turbo cars, this would be easy and we'd publish a formula. But with pressurized cars, the correction factor for altitude depends on the boost you run.

For instance, Sea Level air pressure is 14.7 psi. If you go to a track in Boise, Idaho (2850 feet above sea level) the air pressure is now around 13.25 psi. That's 90.1% of sea level pressure. If the temperature doesn't change and you have an normally aspirated car, your power output will now be 90.1% of what it used to be, so I'd tell you to correct by multiplying your calculated HP by an extra 10.9% (1/.901, or 1.109).

However, (and this is the beauty of turbo cars!!) Let's say you were running 10 psi of boost in the first place. So at sea level, your car was really getting 24.7 psi (14.7 + 10). Now you leave the wastegate at 10 psi and race at Boise. Your manifold pressure is now 23.25 psi (13.25 + 10). Note that YOUR power isn't down as much.. it's down to 94.1% of what it is at sea level. So you should correct with an extra 6.2% (1/.941, or 1.062).

If you wish to calculate your own correction factor, here is a handy table of elevation (feet above sea level) vs. standard day atmospheric pressure (psi):

0 14.70
500 14.43
1000 14.18
1500 13.92
2000 13.67
2500 13.42
3000 13.17
3500 12.92
4000 12.69
4500 12.45
5000 12.23
5500 12.00
6000 11.78
6500 11.56
7000 11.34
7500 11.13
8000 10.91
8500 10.71
9000 10.51
9500 10.30
10000 10.11

Yes, the detail oriented will notice that I'm ignoring lots of small effects of higher pressure ratios in the compressor, lower density air across the intercooler and even the fact that there's less wind drag at higher altitudes, and they're right. However, the overall concepts above still hold true.

Some calculators: http://www.theddddirectory.com/calculators.php#

(The above calculator gives 320hp for a 4100lbs car with a 100MPH trap speed)
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Old 02-22-2013, 02:59 AM
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I think when gauging HP by Trap Speed (the most honest way to get it, I agree), we need to remember to include driver weight.

Let's just be moderate and say our 535i's weight in at 4080 lbs, and then let's say someone who weighs 140 lbs is driving it (again, just being moderate to not risk "inflating the #'s), which would give us 4220 lbs total race weight. The above calculator gave me 329 HP with a 100 MPH trap speed, 319 HP with a 99 MPH trap, and 339 HP with a 101 MPH trap speed.
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Old 02-22-2013, 07:58 AM
Silververtu Silververtu is offline
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I did some math on 550i with a 185 lb driver:

550i weight plus 185 lb driver: 4550 lb
ET (Road & Track on 2011 550i): 13.4 s
Trap Speed (Road & Track on 2011 550i): 106.8 mph

HP is 465 hp and it will need an extra 13.2 hp to get 107.8mph trap speed.
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Last edited by Silververtu; 02-22-2013 at 08:02 AM.
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Old 02-22-2013, 08:04 AM
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Yeah, but again, guys, you have to use something like the software I used or the calculations are too simplistic and don't account for the shape of the torque curve, which is what really matters (see my post about raising torque after peak by 5 torques and how that dramatically effected the vehicle's performance).

The bottom line is the 535i is amazingly fast for its weight and displacement. There's no need to inflate the horsepower number using simple calculations to agree that the vehicle is freaking awesome.

If anyone is interested, I've ran the 550i in the software and can post results.
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Old 02-22-2013, 09:12 AM
Boss330 Boss330 is offline
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Quote:
Originally Posted by cordoor View Post
Yeah, but again, guys, you have to use something like the software I used or the calculations are too simplistic and don't account for the shape of the torque curve, which is what really matters (see my post about raising torque after peak by 5 torques and how that dramatically effected the vehicle's performance).

The bottom line is the 535i is amazingly fast for its weight and displacement. There's no need to inflate the horsepower number using simple calculations to agree that the vehicle is freaking awesome.

If anyone is interested, I've ran the 550i in the software and can post results.
Ok, this is not my field of expertise

But remember that there is a difference between real world results and analysis and a software simulation program. From what I have read it seems like 1/4 mile MPH is a fairly good indicator of HP and have shown itself to be fairly accurate based on a lot of cars with known HP and how that correlates to 1/4 mile MPH.

The dyno results someone referred to also indicates around 320HP at the flywheel (with a 15% drivetrain loss). This again correlates with the 1/4 mile MPH of 100.

So my guess is that 320-330HP is fairly accurate for the 535i.

BTW, I only saw torque figures posted on the results from the simulation program. Is there a different screenshot with HP as well?
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Old 02-22-2013, 10:32 AM
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BTW, I only saw torque figures posted on the results from the simulation program. Is there a different screenshot with HP as well?
Horsepower is on the screenshot with the torque curve (it is the other curve).

Horsepower is a calculated value. Horsepower is calculated by multiplying the torque by the RPM and then applying some kind of constant adjustment factor that makes it what it is (one semi-interesting thing most people don't realize about this fact is that the torque and horsepower curves will *always* cross at the exact same RPM).

The software simulation (this particular one) is very accurate. I would hesitate to dispute its results vs. a dyno or by just going off trap speed. Seriously. Dyno results are not very accurate. They are really only useful for comparing the performance of a vehicle before and after adding mods.

I spent several hours playing with this software in a variety of scenarios and replicating vehicles and trying various things and it is very much accurate. The results I posted are so close to what good track drivers are achieving with this vehicle that to my mind it removes all doubt that it "only" has 300 horsepower and 300 torques. To my mind, that's what it has. It is properly rated (but still fast).

Remember that it is the traversed area under the horsepower curve that determines the total amount of power put down to the pavement (which determines results). So even a very marginal power increase in torque at the end of the power band, say 5 torques after peak, makes a *huge* difference even though it does not increase peak horsepower or torques *at all*.

Nonetheless, I think this discussion will continue because for some people, I guess, 300 horsepower and 300 torques getting you to 60 in 5.4 and a 1/4 mile at 100 is "not good enough."
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Old 02-22-2013, 10:38 AM
Silververtu Silververtu is offline
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Originally Posted by cordoor View Post
If anyone is interested, I've ran the 550i in the software and can post results.
I would like to see the result
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Old 02-22-2013, 11:37 AM
Boss330 Boss330 is offline
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Quote:
Originally Posted by cordoor View Post
Horsepower is a calculated value. Horsepower is calculated by multiplying the torque by the RPM and then applying some kind of constant adjustment factor that makes it what it is (one semi-interesting thing most people don't realize about this fact is that the torque and horsepower curves will *always* cross at the exact same RPM).
That only holds true if you have torque in lb.ft

Horsepower is defined as:
DIN 66036 defines one metric horsepower as the power to raise a mass of 75 kilograms against the earth's gravitational force over a distance of one metre in one second; this is equivalent to 735.49875 W or 98.6% of an imperial mechanical horsepower.

If you have the HP figure for a engine at a given rpm you can calculate torque, or vice versa.

And, have you tried other simulation software and checked if they provide the same results? Simulation is a great thing but with limitations. To take one example; F1 team Marussia (previously Virgin) had a concept of developing it's aerodynamic programme on CFD (Computational Fluid Dynamics) only. No aero tunnel verifications. The big F1 teams all said that this is not going to work, to many variations to get a real result that works in real life. The big teams all used CFD but WITH corresponding aero tunnel work to verify any gains that the CFD simulations indicated. Their experience was that simulations didn't allways give the same results on a real car as it did in the simulation. After a few years with just CFD, Marussia realised this and are now combining CFD with aero tunnel work as well.

The "problem" with simulation software is that you might get very realistic results for ET, MPH, etc based on the car specs etc. But if the software developer have used a different equation (or merely a slightly different factor in the equation) to calculate HP and Torque from the results, then your simulations will show up with one set of HP and Torque and a different software will show different values for Hp and torque for the same car...

I don't doubt that the simulations are consistent and respond to different inputs, hence giving the impression of being realistic. But it's "only" simulations and are dependent on mathematical equations with many variables that have been chosen (not randomly) by the software developer. In theory you could get the same ET, MPH etc with just 100hp and 100lb.ft as long as you change the factors in the equations in the software, but 100hp/100lb.ft would obviously not give the same results in a real car. IMHO this is the "great unknown" factor in simulations... Which factors have been chosen to calculate the results? A different software might have slightly different factors and therefore show slightly higher or lower HP/Torque for the same results...

Dynos obviously have their shortcomings, especially calculating flywheel hp from RWHP. That's why one really should look just at the RWHP from a dyno because that number is generally more accurate.


Last edited by Boss330; 02-22-2013 at 12:28 PM.
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Old 02-22-2013, 12:42 PM
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Quote:
Originally Posted by Silververtu View Post
I would like to see the result
I should re-run the 535i because I did not realize these vehicles to *not* have a limited slip differential! The 535i was run with a limited slip diff.

At any rate, the software is very accurate. The inaccuracy is in my ability to tweak the torque curve, the guessing that goes along with that, and a limitation in the software that does not allow specifying specific torque values at specific RPM's. So what you see is the best I could do.

Also, I weight 180 (which the simulation considers), and the test was performed at about 65 feet above sea level, 68 degrees, and 60% humidity.

Notice the results are in-line with the previous excellent post about trap speed (xDrive is quicker to 60 and 1/4 but has a slower trap speed).

The results are these:

550i

0-30 mph: 2.15
0-60 mph: 5.077
0-100 mph: 11.20
0-200 kmh: 17.31

0-100 m: 5.946 @ 68 mph
1/8 mile: 8.83 @ 86.9 mph
1/4 mile: 13.38 @ 108.3 mph
0-1 km: 23.89 @ 140.8 mph

Top speed: 188.68

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550i xDrive

0-30 mph: 1.699
0-60 mph: 4.58
0-100 mph: 10.99
0-200 kmh: 17.39

0-100 m: 5.565 @ 68.7 mph
1/8 mile: 8.446 @ 86.4 mph
1/4 mile: 13.02 @ 107.3 mph
0-1 km: 23.64 @ 139.1 mph

Top speed: 186.69

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Old 02-22-2013, 12:58 PM
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Quote:
Originally Posted by Boss330 View Post
have you tried other simulation software and checked if they provide the same results?
Your post was excellent.

Regarding other simulation software, I first paid for and tried this one:

http://www.cartestsoftware.com/index.php

It is the latest version of an age-old DOS program I used to play with "back in the day."

Most of these simulators will calculate a torque curve for you based on the peak torque and horsepower at given RPM's. I don't know what formulas they use to do this.

This software is limited by the fact you cannot manually adjust the torque curve to accommodate peak torque spanning a range of RPM's like BMW states these engines do (e.g. the N63 has peak torque at 1750-4500 lb/ft).

When I asked the developer about this, he said to enter the high end of the range as peak into his software and it would "do the right thing." When I did this, the vehicles performed much more poorly than real world results.

Again, I went back to the developer and asked him about this inaccuracy. He said it's because BMW under-reports their engine's torque and horsepower (what everyone has claimed for ages) and that I should simply and blindly add more torque and horsepower (which does indeed solve the problem).

But knowing the math of it, I knew that the shape of the torque curve actually did matter (and in conjunction with the RPM range of each gear). And looking at the graph of the torque and horsepower curves produced by his software, I knew that his software would not be putting as much power to the pavement as it should (again, based on what BMW reports these engines can do in terms of peak horsepower and torque).

So I moved on to look for better software that allowed for adjusting the curve. That's when I found the one I used, which allowed me to adjust the torque curve to be what it is in the screen shots I included in my posts.

But yes, using the software isn't going to be perfect. Its accuracy depends on my ability to adjust the torque curve to what it really is, and how can I really do this without being a BMW engineer who develops the engine.

But I believe one can get the settings in the software "good enough" to show that BMW is reporting accurate horsepower and torque numbers for their engines.

It's also just fun to play with. I can put in my altitude here in Utah and see how much it sucks to live this high above sea level. It cuts 0.6 off my 0-60 time!
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Old 02-22-2013, 01:12 PM
Boss330 Boss330 is offline
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Agree with you.

Software like this is really fun to play with and see which effects different setups can do. And I honestly have no clue how much power the 535i REALLY has. 300/300 might be completely correct for this engine.

Very interesting post.

Could you do a simulation for the F10 523i and 530i with the 8-speed auto - 3900lbs

530i: N53 3l with 7000rpm redline and peak power at 6600rpm.
Spec as the 523i and 528i found here: http://f10.5post.com/forums/showthread.php?t=324662 apart from engine HP for the 530i

530i engine:
Cylinders/valves 6/4
Capacity (cc) 2996
Capacity (cinch) 183.00
Stroke/Bore (mm) 88.0/85.0
Stroke/Bore (inch) 3.50/3.30
Max output (kW/hp/rpm) 200 (272)/6100
Max torque (Nm/rpm) 310/1600-4250
Compression ratio : 1 12.0

Would really appreciate if you coukld do this

Last edited by Boss330; 02-22-2013 at 01:13 PM.
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Old 02-22-2013, 03:36 PM
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Could you do a simulation for the F10 523i and 530i with the 8-speed auto - 3900lbs
I can try, but it will need to be over the weekend. I'm currently swamped trying to meet a self-imposed unattainable deadline for work
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Old 02-22-2013, 03:46 PM
Boss330 Boss330 is offline
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No problem

Only if you have time to do it, no stress

Best of luck with your deadline...
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Old 02-22-2013, 03:53 PM
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K-A K-A is offline
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Quote:
Originally Posted by cordoor View Post
Nonetheless, I think this discussion will continue because for some people, I guess, 300 horsepower and 300 torques getting you to 60 in 5.4 and a 1/4 mile at 100 is "not good enough."
For me it's just hard to believe because it seems physically impossible for a 4100+ lb car to hit a documented 100-101 trap speed with "just" 300 HP. Also taking into consideration the dyno video's we've seen which translate to over 300 HP with a general 15% drivetrain loss, etc.

If the engine truly does make a 300 HP flywheel dyno, then it just speaks volumes in how well BMW can engineer their power to the ground, and how amazing the power delivery considering what its working with this engine/tranny combo makes, so either way it's good news.
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