N54 – Stock vs. PPK1 vs. Cobb – Here's some acceleration results...

[wjk_glynn]

Hi folks,

There’s many N54 dyno tests (with varying setups) to peruse on the internet. But rather than duplicate those, I’m more interested in actual acceleration results at “real-world” speeds - e.g. what you might see say canyon-carving...

So since acquiring the car, I’ve recorded relative acceleration results with my car as it has evolved from 100% stock to its current configuration. There's no earth-shattering revelation in the results below. But as these modifications are fairly common (i.e. modest/inexpensive), I thought some people might be interested…

Acceleration tests were performed on the same car as it evolved through the following setups:

1. Stock 2008 N54 135i 6MT Coupe, with a Dinan oil cooler
2. Added PPK1
3. Replaced with PPK1 with Cobb V2, running the Stage1 Drive (ACN91) map
4. Added a VRSF 5" stepped FMIC, and switched to the Stage1+FMIC Drive (ACN91) map

The attached picture summarizes the results:

• I converted the various interval times to acceleration rates (∆v/∆t) in units of G, which is directly proportional to engine torque
• Then calculated the corresponding Gain over stock with each modification

The best was with the VRSF FMIC and Stage1+FMIC Drive map, resulting in a 29% gain through the entire rev-range (and as much as 32% in the mid-upper ranges).

When you consider I paid only $300 for the Cobb V2 (used), and $390 for the VRSF FMIC (new), they were fantastic bang for the buck...

Karl.

PS: It’s best to focus on the relative gains not absolute gains in the attached picture, more in the following post on the test method...

[wjk_glynn]

As regards the test method...

I'm fortunate enough to have intermittent access to a private expanse of smooth concrete where the tests could be done safely.

The test runs were all rolling starts, accelerating from low in the rev-range to near the rev-limit:

• Begin by rolling in 3rd gear at 600-700 rpm (~9 mph) with traction control fully off
• Floor the throttle
• Start the clock as the car passes 20 mph (~1,300 rpm)
• Record the time at each successive 10 mph interval (i.e. 30 mph, 40 mph, etc.) all the way up to 100 mph (~6,600 rpm)
• Repeat the runs a number of times in both directions to cancel out effects such as gradient or head/tail winds

I don’t have access to sophisticated timing equipment (e.g. RaceLogic VBOX). My crude technique was to point a GoPro camera (720p, 30 fps) at my P3 Gauge and measure time using timestamps in the resulting video clips. I wouldn’t trust the absolute measurements from this method, but I think it’s sufficient for relative measurements between configurations so long as it's consistently applied.

And I've tried to have consistent conditions for each test so as to minimize their impact. Things like:

• Try to do the tests at the same ambient air temp. I wasn't 100% successful, but the variations weren't too dramatic
• Consistent weight (e.g. fuel tank always full)
• Same gasoline (i.e. Chevron ACN91 from the same pump each time)
• Same tires, at the same pressures
• Etc.

Now some may wonder why I’m using the Drive maps instead of the Sport maps. The reasons are:

• Here in California, our 91 gas is actually ACN91
• Cobb recommends the Drive map when using ACN91 – see Fuel Requirements on page 2 of their N54 map notes
• There’s anecdotal reports on this forum of some people having undesirable amounts of timing corrections with ACN91 on Cobb's regular Sport maps
• I’m too lazy to mess around with E85/meth/etc – I just want to “set it and forget it”
• And I’m past the traction limit in 2nd gear with my current rear tires (245/35-R18 RE050A RFTs) and my current suspension setup

There you are...

Karl.

[wjk_glynn]

And then just for yucks, the attached are professional road tests of comparable cars that have 3rd gear results...

Look at the 3rd gear 70-100 mph segments for comparison with the above.

Karl.

[Orpo]

Great information and thank you for your efforts. I will definitely use this as a reference for my next upgrades.

Nb: I remember reading something about issues when flooring a turbo car at low rpm. Obviously I don't remember the details, but I remember that it was bad.

[wjk_glynn]

Originally Posted by Orpo

Nb: I remember reading something about issues when flooring a turbo car at low rpm. Obviously I don't remember the details, but I remember that it was bad.

Lugging the motor from low revs is not advisable, certainly not on a regular basis.

However I wanted to see the effects across the entire rev range - especially as BMW claims the N54 hits its peak torque as low as 1,500 rpm (with OEM tunes).

Hence the method above.

But not something you'd do every day...

Karl.

[mike@x-ph.com]

Awesome thank you for sharing

You got yourself a really good deal on that FMIC

[wjk_glynn]

Originally Posted by mike@x-ph.com

...You got yourself a really good deal on that FMIC

Indeed Mike, loved your Black Friday sale...

Karl.

[mike@x-ph.com]

Originally Posted by wjk_glynn

Indeed Mike, loved your Black Friday sale...

Karl.

[gap]

Thanks for sharing Karl. I've settled on Stage 1+ FMIC LT Drive too. Ran 1+ aggressive for awhile but it wasn't as smooth and I was concerned about overworking the stock turbos.

If I'm reading the data correctly my car, at least in a straight line, could keep up with a stock M2.

[wjk_glynn]

Originally Posted by gap

Thanks for sharing Karl. I've settled on Stage 1+ FMIC LT Drive too. Ran 1+ aggressive for awhile but it wasn't as smooth and I was concerned about overworking the stock turbos.

If I'm reading the data correctly my car, at least in a straight line, could keep up with a stock M2.

Maybe, but I'd be very careful jumping to conclusions from the data above.

All it really shows is the relative gains on my car when the ambient temperatures were in the mid-upper 40s (°F).

The data points that support your conjecture are:

• Professional road tests of stock N54 cars saw an average 70-100 time of 5.3 seconds
• My technique on my stock 135i yielded 5.2 seconds, so the technique seems to yield results that are 'reasonably' similar to the professional lads
• Car and Driver saw 4.5 seconds on a 6MT M2 (and its 3rd gear RPM-vs-Speed ratios are similar to a 135i)
• With Cobb Stage1+FMIC Drive, I saw 3.9 seconds
• Ergo Cobb Stage1+FMIC Drive must be quicker than a stock 6MT F87 M2

However, there are unknowns that potentially undermine that assertion. A few things that come to mind:

1. BMW has (from a product positioning perspective) torque targets that vary the boost to hit consistent acceleration rates independent of weather conditions - so generally you'll see the same acceleration rates at 40F and at 80F. But does Cobb do the same thing? Or do they give you the full beans (for the conditions) across the board? Would you see relatively less gains as it gets hotter, or do they compensate by raising the boost as it gets hotter? I haven't had it long enough to tell.
2. Does the Cobb SW affect the scan rate of the P3 gauge when reading the uncorrected speed signal from the VSS? Probably not, but again I don't know for sure.
3. And finally, it's early days yet in terms of seeing data from F87 M2 tests...

Having said all that, I do think you'd give a stock 6MT F87 M2 a serious run for its money.

Karl.

[gap]

After 8 years of owning my 135 I still love it and will keep it for a long time.
If I was looking for a new BMW the M2 would be it. I think it is a good value
since with all my mods I probably have the same amount invested as the price of
a M2 that comes with everything I've added and more.

[wjk_glynn]

Originally Posted by gap

...If I was looking for a new BMW the M2 would be it...

Same here, and I'd leave it stock. It seems plenty quick, and the reviews are reporting excellent dynamics/handling.

An alternative in the same approximate price range is a 2016+ GT350. But only with the TrackPack as lot of owners are reporting limp-mode issues without it...

Karl.

[wjk_glynn]

Postscript...

After ~13 months (and 5.5K miles), I uninstalled Cobb and reverted back to PPK over the weekend.

The reason is that I'm actively purchasing a 997.2 Carrera 4S and I expect to put the 135i on the market in few months. I've begun transitioning the car in anticipation.

Plus I couldn't have the 135i (w/Cobb) being quicker than the Carrera (when I get it). Definitely wouldn't do

But shock-horror...

I actually think the car drives better with the PPK.

Now clearly no where near as quick as with Cobb. But on a Sunday morning blast though the hills, it felt 'better' somehow. Hard to quantify, but it was definitely more smooth and refined, less 'frenetic' than you get with Cobb.

And it's still an exceedingly quick car (by my standards) with just the PPK.

Anyway, just thought I'd share the observation.

Karl.

[ianc]

I like frenetic. ;-)

ianc

[wjk_glynn]

Originally Posted by ianc

I like frenetic. ;-)

I hear ya!

But can't have it upstaging the 997...

Side note, since you're also in the Bay Area, my two favorite Sunday morning blasts are the:

1. The run from Saratoga down to Boulder Creek on Hwy-9
2. The climb up to Lick Observatory

Karl.

[ccdre]

Originally Posted by wjk_glynn

I hear ya!

But can't have it upstaging the 997...

Side note, since you're also in the Bay Area, my two favorite Sunday morning blasts are the:

1. The run from Saratoga down to Boulder Creek on Hwy-9
2. The climb up to Lick Observatory

Karl.

+1 on the Lick Observatory - both the SJ side and the Livermore side

[ianc]

Thanks for the road tips; it's certainly tough to find a fun drive around the bay area. I've just about given up, but will def check these out when I'm next in the neighborhood!

ianc