Reborn996

Well, ended up getting a very odd response to this from Porsche...

"When you are on a steep enough hill and the vehicle reads how hard you are applying the brakes it will hold the vehicle for 2 seconds before it lets you roll back. This is how the GT4 hill hold feature is designed. You have that amount of time to engage your clutch. Plus I talked to another GT4 owner here and his works the same way, even the light upon start up and no light on dash when activated."

I am NOT happy about this. It is a very poor behavior. Why shouldn't it hold fully until throttle is applied? The disengagement after 2 seconds seems silly and could cause an accident. Bottom line, I want it to behave just like it did in my 991. I will be escalating to PCNA about this.

Is this the way it behaves for the rest of you?

sapman

In so far as getting a limited amount of time to engage the clutch and gear, I think my e92 M3 worked the same way. I could be wrong because I sold that car ~4 years ago and my memory isn't what it once was. There are plenty of former and current e92 M3 owners on here who can correct me if necessary.

Reborn996

My 2014 manual trans 991 did not have this behavior. It held till the throttle was applied and the HOLD light showed in the dash when activated. Should be the same for all Porsche cars like it says in the owners manual.

sapman

My PDK 991 did the same thing.

vantage

2 seconds is plenty of time. That's actually the reason I have no idea whether the car holds indefinitely or not. Guess I'm used to cars w/o the feature. In any case, I'll try to report back to you if the opportunity presents itself.

STLPCA

I timed the release interval in my car and it's about 1 second which is also more than enough. Indeed,I find Hill Hold to be a bit too slow to disengage.

I had assumed Hill Hold used the e-brake, but I now believe it uses the main braking system. If, while HH is engaged you quickly release and then reapply the brake you'll find the pedal to be rock hard. I assume that's because the pads are already hard against the rotors. The drum e-brake would have no change in pedal feel.

I find it ironic that for a "pure driving experience" manual shift only sports car Porsche has Hill Hold and auto-blipping to eliminate the need for 2 of the skills that separate experienced from inexperienced stick shift drivers.

hccyong

There are some hardware duty cycle limitations here. The system in the 981 is likely done by using solenoids to hold the pressure in the brake lines (after you've applied it via the pedal). These are the same solenoids used to dump and hold brake pressure during ABS, TC, ESC, etc., and there are limitations on how long they can be held in the energized positions. There probably is room to add more time, but not forever, as is the case with some other ways of accomplishing hill hold. For example, if the limit is say 10 seconds before the hardware needs to release, then it could be even more confusing. Someone could think it'd last forever or forget that hill hold was engaged and then realize too late when it eventually releases when the driver is not paying attention (e.g., reaching for something in the glove compartment). I do agree though that eliminating the hold activation light is strange. Perhaps someone high up in the chain didn't like the look of it

hccyong

Sounds like they use a different system in the 991. If it holds indefinitely on the 991, then it definitely makes sense to light the lamp. Most cars in the field that do a short (1-2 second) does not light the indicator (and often don't have an indicator to light). It sounds to me that the part that Porsche missed is:
- deactivating the startup lamp in the 991
- correcting the manual

Are there actually any 981s that do hold forever or light the lamp when holding?

hccyong

So did they get back to you on why it doesn't work at all? Or are they saying now that it does work, just in a specific set of conditions?

jphughan

BMW's hill hold works the same way, and if I had to guess, the automatic release is so that people can roll backward into parking spaces while on an incline, for example, while keeping the car in a forward gear to slow their downhill momentum when needed. Do you really want to have to add throttle to back into a space downhill and then switch over to the brake to slow/stop? When I first got my M3 (first manual transmission car I owned), 2 seconds felt like too little time. Now it feels like an eternity. I can't even remember the last time the car started rolling back before I managed to get my foot over from brake to gas and start letting the clutch out.

Escalating with PCNA about this, really? Even if you don't accept the utility of this design decision in some cases such as the one I just described, what do you hope to achieve with that?

Reborn996

I see no reason why the behavior in my 991 wouldn't apply to the 981 as both were manual transmissions. The owners manual even shows the same behavior. Porsche is saying the hold is only for a second or two and then releases as designed. To me it's a safety issue, in not knowing when it's active via the HOLD light and for releasing after a few seconds without having throttle applied to ensure a rollback doesn't occur in steep areas like SF.

I never had an issue with it (actually liked it!) in my 991 so yes I am pursuing this further with Porsche. Guess I will see what they say.

Reborn996

Now if they had given us the manual parking brake instead of electric this would all be a moot point!

sapman

As I think you have seen, the user manuals are not always reliable. But it sounds to me that the hold light not working when active is a legitimate problem that somehow got overlooked in the GT4. Kudos to you for pursuing this and please keep us abreast of how you fare.

Reborn996

I just don't see Porsche developing a unique "Hold Assist" for various models... I have seen features and modules leveraged across multiple platforms all the time from VW to Audi to Porsche, and especially within a Mfg like Porsche. The Hold Assist used in GT4 models should be the exact same one for all Porsche models is my bet... something is just not working right.

vantage

It's actually an incredibly easy thing to change from a software perspective. Just a parameter. I still don't see the safety issue. If you are on a steep hill, you should either be on the brakes or attempting to move the car. Not sitting there indefinitely with no brake applies.

Good luck but don't let all these little things you are posting about ruin your enjoyment of the car. IMO!