MagicRat

Warning. This thread is going to contain data, published by someone (me), with no affiliation to any aftermarket provider. If you are of a superstitious or nervous disposition, then please consider reading no further.

The background: My GTS has an an ongoing minor problem. After it comes to a stop, if I press the brake hard enough to activate the start/stop (or, usually, the little light that says it isn't available right now) the car does a little lift of about 100-150 rpm, like a ghost has pressed the accelerator. This happens only when the engine is warm. It's not the end of the world, but it is kind of annoying.

(Question, as an aside - has anyone else experienced this, or does anyone have any idea what it is?)

Porsche took the car in and re-flashed the ECU and replaced the throttle body under warranty, which didn't help. They also said that because the car has aftermarket headers and cats, the powers at PCGB said they wouldn't investigate any further unless the car was returned to stock and driven for a bit, and the problem was still there.

I like things to work properly, so have decided to do as they asked. The good news is that my tuning shop now has a dyno, so we get to turn a problem into a learning opportunity. This Friday I am taking the car there. We're going to do one dyno run with the car as is (Fabspeed sport headers, with 200-cell cats), then put the stock headers back on and run it again. I will then post what we find, and then, hopefully, Porsche will be willing and able to fix the weird revving problem. It predated my fitting the headers, by the way, and is nothing to do with them, but so it goes. My bad for not getting it looked at before I fitted them, so I don't mind spending a few ££ in what is now the name of science.

My butt-dyno said the Fabspeed headers produced a slight gain, but that this gain was greater with PSE on - ie the exhaust flow was increased, so the PSE became a limiting step, which it isn't with the standard headers. I'll be interested to see if I'm right, or if it was simply that the noise was louder.

Can I also please ask that this not turn into another modding vs not modding warranty/legal etc thread. I'm of the school that believes even Porsche build things a) with a bottom line in mind, and b) to fulfil a whole lot of regulations not all of which are to do with my driving pleasure, and I don't feel the need for addtional debate about that. A big welcome, though, to anyone who has themselves modified a Porsche and dynoed it pre- and post. Let the fact-fest commence!

Obviously, in a couple of days...

Larry Cable

you probably want to reset the ECU after you return to the stock system to have it relearn mappings ... but you knew that ...

NoGaBiker

What is this "start/stop" you speak of? :Puzzled:

MagicRat

Thanks. Would driving the car around for a bit not do that?

Larry Cable

I believe so, but since you are trying to isolate a possible problem, an ECU reset and relearn eliminates any possible chance of some mis-configuration being the root cause.

PatrickC23

Curious - is your GTS wrapped? Your avatar looks matte to me, cant tell if that's just agate, or a matte paint/wrap.

Edit - found your post about the wrap, looks amazing.

MagicRat

Cheers. Yeah, gets a lot of compliments, and makes cleaning a great deal easier!

Re the ECU I'll ask my tuning guru, but car has already had all adaptations removed and full ECU reset which didn't solve the problem. We shall see!

John@Fabspeed

MagicRat,

Let me know if there is anything we can provide to assist in the testing and resolution of your drivability problem. I look forward to seeing the results and you getting back on the road without any hiccups

satoru

never thought too many peeps use the option, Macan guys just hate it

NoGaBiker

I'm just so grateful the 911 allows the off button to stay pushed when you restart the car. Of course, inexplicably the Sport or Sport+ or PSE buttons don't stay like they were, so I guess having to push one more button EVERY FREAKING TIME I START THE CAR wouldn't be the end of the world.

Seriously, anybody know why Porsche is so certain I won't want to be in Sport+ mode next time I drive, even though I wanted to be in it last time (and 98% of every other time) I drove?

Noah Fect

Regulatory agencies test the car in the default state. Allowing the owner to change the default would be seen as circumvention.

NoGaBiker

But surely the auto stop feature is a contributor to mpg and emissions. Why bother to make it permanent and the others temporary? obviously customer convenience is not the driving decision, so why not eek out every last bit of low emissions and fuel economy that you can?

That's what doesn't make sense.

NoGaBiker

Hmpfff... Clearly I've stumped you all.

Jhoffmann

Actually, manufacturers originally got the credit for offering a start/stop system regardless of the programming. That loophole is soon to close and new cars will require you to push the button to turn it off on each ignition cycle.

ibmiked

There is actually a modification you can have done that leaves either Sport or Sport Plus on as the default just like the Stop/Start. Can't remember where I saw it but I've been meaning to have it done myself.