matttheboatman

Thanks guys for all the good information in this thread - it has helped me. So, I went back and tested my car. Confirmed. Hill Hold engages (without light) for approximately 1 second on my car. Long enough to get off the brake and on the accelerator, true. I also tested driving through the brake after engaging. It worked fine.

This means to avoid hitting the car behind you, you will have to ride the clutch.

In traffic, I suggest engaging the ebrake manually where you are confident it will prevent the car from rolling backward. You can drive through it without needing to release it.

Reborn996

Had an interesting response from Porsche on this as they had my car all last week... they said the GT4 has "brake assist" rather than "Hold" but in looking at the owner's manual there is no mention of this. I did find online there is that feature for Cayman 981 models but it is part of the PSM and not related to braking on inclines.

http://www.porsche.com/usa/models/ca...anagement-psm/

The situation we seem to have is a variant of the Hold assist that Porsche references for 981 models but is not functioning the same... very odd. See below Porsche video which shows how it should operate.


Now for the kicker! My service rep and I noticed a new GT4 sitting in the showroom and when we looked at the window sticker there was NO mention of Auto Start/Stop or Hold... so this could be a matter of Porsche screwed up on my window sticker. LOL

But none of this explains why we have a car that will only hold for a second or two with no indicators and then release. So odd...

hccyong

Unfortunately, Porsche and the video seem to be causing more confusion. First auto start/stop is entirely unrelated and relates to the engine turning off when you're at a stop light under the right conditions. "Brake assist" has nothing to do with hills either. It's a function in the PSM aka electronic stability control (ESC) in industry speak that adds brake pressure beyond your foot command in emergency situations when the system thinks you need it. There are also many variants of this, but that's not the topic here. The video is also wrong because the parking brake has nothing to do with the various hill functions.

Hill hold is the generic name for keeping the car from rolling back on a hill. However, in recent years, the term has split slightly to differentiate between the newer, more advanced feature of continuous holding with indication (which is still called hill hold) vs. holding for a second or two without indication which is often now called hill start assist (but some companies still call it hill hold). The video suggests that this is called "drive off assistant" at Porsche.

It sounds like the two key questions for your system are:
1. Does it at least hold 1 second like what others here have confirmed, or is it so short it's insufficient for you to add accelerator and release the clutch to the engagement point. If so, then there's a problem with your system, whichever system it is.
2. Do non-GT4 981's light the hold light and hold indefinitely. If so, then Porsche has downgraded the hill hold for hill start assist for whatever strange reason, but there is not much we can do.

Reborn996

Can you please share your source that says Hold assist doesn't use the parking brake system? You keep saying that but I have found nothing to support it and the Porsche video contradicts that statement.

I only brought up Auto Start/Stop as it was featured on the same line as Hold Assist in my window sticker, I know they are not related.

The hold for one second is a glitch in my opinion as I do not see what value that could have in real world driving. LOL

Reborn996

Drive off assist is the automatic release of the parking brake when driving off and has nothing to do with holding on hills.

hccyong

I have no source other than some experience working with brake control systems at one manufacturer and now work part time evaluating brake control systems at another manufacturer. Using parking brakes for hill hold doesn't make sense these days because it's very slow; it takes about 2 seconds to engage and disengage. It definitely doesn't use it on the GT4 because the system is very loud and would be audible. Also, you'd feel the grab on the rear axle (the rear would squat upon driving off on it). Also, as you come off the brake and transition the load onto the parking brakes, the car would also change its stance somewhat, and that doesn't happen on the GT4.

If you find the one to two second hold too short, then I suspect your system is canceling out and not holding long enough. As others have noticed, the hold should be more than long enough for you to apply apply drive torque through the accelerator and slipping the clutch. I'm very surprised that Porsche cannot provide a very comprehensive answer to your questions or run the service diagnostics procedure for the system.

My colleague tells me that some PDK cars have a different system to protect the transmission. I think the key is to understand the behavior on other manual 981's. But then again, it is possible that there is some other requirement/conflict that drove Porsche to change the GT4's system relative to their other ones.

IrishAndy

To be honest I've no idea why 1 second (ish) isn't enough to engage the clutch to bite point. It seems to work very well to me. You just sit in neutral until the cars ahead start to move and then depress clutch, select gear and find your bite point. The process doesn't feel hurried at all to me.

Agree that it's not using the e-brake (or at least not in a conventional way) because that's a slow, audible system that never goes unnoticed

STLPCA

If a driver can't get a stick shift car moving on a hill with the brake engaged within about a second he needs to go back to manual transmission 101

user1029

I have a thing for women who drive manual sport cars, that video isn't helping

needmoregarage

^fixed it for ya ^

My window sticker shows "Auto Stop Start and HOLD functions" under Standard Equipment

Owner's manual shows "HOLD" may show as an indicator light (page 74) but I can't find anything on what "HOLD" means

mathfuzzy

Posting here as a PSA for other new GT4 owners to bring the thread up again.

I was trying to figure out if my car had it because the hold light doesn’t come on and it doesn’t (seem) to kick in on less steep inclines like my 991 does and 997 did. Anyway, this thread cleared it up.

Thankfully my car (didn’t read the whole thread to find out about others) doesn’t seem to have *** (appropriate acronym for auto start/stop). Or if it does it’s been, mercifully, disabled.