MagicRat

So in a continued attempt to bring scientific rigour to the Porsche-fettling world I set out in my Spyder today to try to log some 0-60 times with and without my Cobb OTS tune. Found a decent bit of road (few people, good turning places) and gave it a go. First problem was the 0-60 would only record one time in three, and the one that did record I f*ed up the shift anyway. Second problem was the thought that my quality of launch and gearchange would probably overshadow any changes from the tune, and third was the clutchy smell that was enveloping the car after those three dumps of the pedal at 5,000 rpm.

But then I saw the Cobb Accessport has a dyno mode. It asks for the car's weight, the gear of choice (I went for 2nd because licence) and the starting and finishing revs (2k and 7k are the defaults, which I kept). The idea (I think) is to floor the gas at low revs in that gear and back off when 7k is past. Driver error and clutch torture solved!

Except the results were rather strange. My first read was 300hp, but the stretch of road was slightly uphill, so I turned around and did it the other way, and got 425hp. This was, y'know, quite different, but maybe the Cobb is just really sensitive to gradient. 425+300 / 2 = 362.5, which is not a terrible approximation of the car's stated power. What I needed was a totally flat piece of road.

And I found one. Gentle right-hand bend, but flat as a pancake. I'm tempted to ask for answers on a postcard here, but what the Cobb told me my car was putting out there was...wait for it... 465hp. Nice though this number would be, it is absolutely definitely isn't even near accurate. Plus I then did the same bit of road in the same direction - literally identical conditions - and got...

Oh yes...

535hp

Either I am using dyno mode massively incorrectly, my car is morphing into a Turbo S under my backside, or Cobb has produced a random-number generator.

I then went back to old unscientific methods and drove really fast down the road. Then I took the map off and did the same. Then I put it back on and did the same. I concluded (again) that the map is a Minor Good Thing (Stage 1 93). It makes the car rev more cleanly and I am sure adds some in the midrange. The car feels like it takes off at 5,500 with the map off but has a consistent pull to redline with it on. If I had to bet money I would say the top-end power is the same but the area under the curve is greater with the map on, which improves driveability.

So I'm not, like, an unhappy customer, but that dyno mode - really? Anyone else tried it, or would Cobb care to tell me what I was doing wrong? Know that I was not expecting supreme accuracy, but I got a variance of 225hp. That's like a whole not-slow car's worth of difference between my lowest result and my highest, on similar bits of road on the same day.

What gives, people?

mrmandmman

What car do you have?

extanker

its the type thats gonna need a new clutch soon if he keeps testing at 5 grand

MagicRat

981 Spyder



Yes quite that's why I stopped doing it!

MagicRat

Yet with PDK cars it is apparently fine, and produces no smell of clutch whatsoever. Maybe dual-clutch transmission less stressful?

randr

You have a NA car, not sure what you're expecting - but it wont be much. Run a 1/4, check the trap it'll tell your everything you need to know.

COBB Tuning

Dyno mode (and the rest of the performance features) can be tricky to use with many Porsche applications because it's based off the wheel speed sensor data. Any, and I mean ANY, wheel slip at all will cause the test to shut down (see your results with 0-60) or give fictitious readings (see your results from dyno mode). The features are ported over from our Subaru APs where universal AWD makes the features slightly more reliable, but still not particularly accurate, as a small amount of wheel spin is required for best 0-60 and 1/4 mile times.

Additionally, for dyno mode to be accurate at all you'll need to have your exact car weighed, with you in it, so a set of portable scales (most often used for corner balancing) or the use of a public truck scale would be required for the weight to be correct. Otherwise, using posted curb weights and estimates will also result in skewed results.

Let me know if you have any additional questions!

~Jared

WaltB

My recommendation would be to find someone else in the area that has a stock Spyder and do some 2nd and 3rd gear runs together and see if you run away from him, slowly walk away or stay relatively close to each other.
That will give you a little more real world understanding of what your tune is doing compared to the stock version.

For me to want/pay for a 981 tune I want my car to run away from the stock version. Slowly walking away is not worth the cost in my opinion.

Walt

MagicRat

Ah, that would explain it! Thanks. Weight I guess wouldn't matter if I just wanted a pre-post tune comparison, but there was definitely some wheelspin.

I shall abandon that particular data-gathering mission...

Voyager6

PDK clutch is kept cool via ATF fluid. Heat gets taken away to oil/water heat exchanger and very little wear results on the clutch material.

V6

MagicRat

Interesting. Thanks.

Dicknose

Where is this dyno mode?
Under performance I only see the 0-60 and 1/4 mile.

MagicRat

It's next to those in mine, but if you haven't got it you're not missing much!

Dicknose

Just saw the release notes, it was removed end Feb 2017.
I got mine in March!

As you said, not missing much, maybe they thought it wasn't up to required standard.