2010 GT Manual slows itself going down hills to keep speed stable - normal?

[LittleRedGT]

My new GT seems to slow itself(feels like the brakes are coming on) when it goes down a hill - just enough to keep the speed stable. Cruise control is NOT on. Thought it was kind of cool at first but now I'm finding it annoying and also wondering if it's normal and how it works.

Anything to do with my horrible 12.4l/100k fuel economy?

[slam525i]

First time owning/driving a manual? It's engine braking that keeps your speed down.

(Unless something is really broken. If you slip the clutch very slowly in 2nd gear with no gas from a stand still, does the car roll along okay? It should if your brakes/hand-brake isn't grabbing.)

[MistaChin]

First time owning/driving a manual? It's engine braking that keeps your speed down.

(Unless something is really broken. If you slip the clutch very slowly in 2nd gear with no gas from a stand still, does the car roll along okay? It should if your brakes/hand-brake isn't grabbing.)

+1! Engine braking!

[m_bisson]

if you want to coast just put the clutch in. Saves gas, but you'll need the real brakes to maintain speed.

I've gotten into the habit of pressing the clutch every single time I brake, simply because there are too many idiots on the 401. If you lock up your front wheels with a standard the car will stall, leaving you with zero power to get out of an emergency situation unless you start the car again. This can happen easily in the winter on icy roads even under normal braking. At the very least, cover the clutch with your foot while braking.

[MistaChin]

I wouldn't clutch every time you brake, especially at high speeds. You'll wear the brakes a lot faster. Unless it is an emergency situation then don't do it.

[m_bisson]

It's actually easier to lock your wheels up at high speed... But you seem to be the expert driver here, so I'll stop giving advice. I'll take safety over wear any day :)

[slam525i]

Putting the clutch in doesn't save gas. When the engine is spinning due to the car's kinetic energy, the fuel injectors shut off and absolutely zero fuel is used.

"Best practices" is to row your way down the gears as you slow, or at least leave it in high gear while braking. That way if you need to accelerate again, you can do so almost instantly. If you clutch in while at speed and you suddenly re-engage the engine without rev matching, you apply a bit of a shock through the drive train. If you do that in low traction, you'll lose front end traction.

[slam525i]

I forgot to mention:

If you're on a long hill and you ride your brakes all the way down, you'll heat up / over heat your brakes and lose braking power. Even in an automatic, it's advisable to descend a hill using engine braking.

[MistaChin]

It's actually easier to lock your wheels up at high speed... But you seem to be the expert driver here, so I'll stop giving advice. I'll take safety over wear any day :)

I never said it wasn't easier to lock your wheels at high speeds, did I? I said clutching in EVERY SINGLE TIME you brake shouldn't be done.

I agree with slam525i.

[LittleRedGT]

[QUOTE=slam525i;608629]First time owning/driving a manual? It's engine braking that keeps your speed down.

I've been driving a manual for 20 years ;-). Granted I just traded in a 1991 Mazda Protege so I'm not used to the new technology! I don't think it's simple engine braking. It comes on briefly - just as if I had touched the brakes and then let's go, and then maybe again but not continuous such as when gearing down to maintain speed. And it's not random but clearly only happens when the car would otherwise be accelerating due to the grade. Any other thoughts?

[slam525i]

Could be these new fangled electronic throttles you're not used to. Or the fuel injectors shutting off on coast.

I find the 3 acts a wee bit funny when near idle compared with older cars. It will open the throttle a touch if it gets too close to idle, and then re-close it when it knows it won't idle-cough-out. Could also be that when you coast down the hill, the fuel injectors cut off completely after a brief while, adding a little extra deceleration after you've already come off the gas which you don't get with carb engines.