Engine braking with 6MT?

[TheFlyingMouse]

Hi All,

As I've been driving in the Alps during my ED trip I have noticed that the F80 M3 tends to run up a lot more speed going downhill than I am used to. In my previous (naturally aspirated) cars, taking your foot off the throttle would introduce enough engine braking so that you do not have to press the brakes very often at all when going downhill. In the F80, I had to pretty much ride my brakes like I was driving an automatic today in order to avoid tailgating the car in front of me.

Is this just a characteristic of turbocharged cars, and is it inline with what you all are experiencing with your F8xs? Is more engine braking available in Sport/Sport+ throttle modes? I've been running efficient mode to avoid getting into the gas much and/or forcing the turbos to spool before the engine has had at least a few hundred miles on it.

[CanAutM3]

Originally Posted by TheFlyingMouse

Hi All,

As I've been driving in the Alps during my ED trip I have noticed that the F80 M3 tends to run up a lot more speed going downhill than I am used to. In my previous (naturally aspirated) cars, taking your foot off the throttle would introduce enough engine braking so that you do not have to press the brakes very often at all when going downhill. In the F80, I had to pretty much ride my brakes like I was driving an automatic today in order to avoid tailgating the car in front of me.

Is this just a characteristic of turbocharged cars, and is it inline with what you all are experiencing with your F8xs? Is more engine braking available in Sport/Sport+ throttle modes? I've been running efficient mode to avoid getting into the gas much and/or forcing the turbos to spool before the engine has had at least a few hundred miles on it.

FI engines usually run a lower compression ratio, which reduces engine braking. Further, the F8X has rather tall gear ratios, which also reduces the effect of engine braking.

Trying using a lower gear to match the target speed and road grade.

[solstice]

Originally Posted by CanAutM3

FI engines usually run a lower compression ratio, which reduces engine braking. Further, the F8X has rather tall gear ratios, which also reduces the effect of engine braking.

Trying using a lower gear to match the target speed and road grade.

But not too low...we had enough money shifts
Rather use the brakes to pick up the slack, it's what they are there for.

As you start driving you car harder and hopefully using the excellent rev. match you'll want to get away from the downshift to slow the car habit to a large extent. Not fully and not in all situation but in general it's better to limit that usage of the engine.

[CanAutM3]

Originally Posted by solstice

But not too low...we had enough money shifts
Rather use the brakes to pick up the slack, it's what they are there for.

As you start driving you car harder and hopefully using the excellent rev. match you'll want to get away from the downshift to slow the car habit to a large extent. Not fully and not in all situation but in general it's better to limit that usage of the engine.

It's not quite how I read the OP.

Using constant engine braking (as opposed to the "compression" of a downshift) to manage your speed going down a long grade is a perfectly acceptable practice in my book

I agree, the brakes should be used to slow you down in most driving conditions (coming to stop/red light, stop-and-go traffic, etc...).

[solstice]

Originally Posted by CanAutM3

It's not quite how I read the OP.

Using constant engine braking (as opposed to the "compression" of a downshift) to manage your speed going down a long grade is a perfectly acceptable practice in my book

I agree, the brakes should be used to slow you down in most driving conditions (coming to stop/red light, stop-and-go traffic, etc...).

Well a downshift is the only way to increase engine breaking in his scenario since letting off the throttle in the current gear is kind of a given

[TheFlyingMouse]

Sounds like it's a combination of heavier car, taller gear ratios, and FI behavior that lead to less effective engine braking. I haven't had to go to a lower gear than 4th to hold speed reasonably well down steep grades in my previous cars (usually 5th or even 6th is enough). I guess the F80 is just a different beast and I'll have to make a behavior change somewhere.

@solstice:
I don't think I'm likely to money-shift it as I've been driving nothing but BMW manuals for the last 12 years. Using engine braking to control downhill speed is perfectly normal and will not hurt the engine or the clutch as long as you rev-match it first and keep the RPMs sane. Just letting the clutch out with RPMs at idle isn't engine braking; it's a sure-fire way to buy a new clutch (and possibly other expensive, hard-to-install parts!)

@CanAutM3:
I usually rev-match into second gear as I slow down for a traffic light, then push in the clutch as I come to a stop. There's very little wear on the clutch when you do that, and you don't chew up your brakes as much if you let the car slow down over a longer period using engine braking. Personal preference on how you want to balance the wear.

For stop and go traffic I always try to select a gear and constant speed to match the average speed of the traffic. If that doesn't work, I lift off when I see brakes lighting up several cars ahead, and only add gas once the gap to the car in front of me has opened up a bit. Saves a lot of stress, in addition to wear and tear.

[solstice]

Originally Posted by TheFlyingMouse

Sounds like it's a combination of heavier car, taller gear ratios, and FI behavior that lead to less effective engine braking. I haven't had to go to a lower gear than 4th to hold speed reasonably well down steep grades in my previous cars (usually 5th or even 6th is enough). I guess the F80 is just a different beast and I'll have to make a behavior change somewhere.

@solstice:
I don't think I'm likely to money-shift it as I've been driving nothing but BMW manuals for the last 12 years. Using engine braking to control downhill speed is perfectly normal and will not hurt the engine or the clutch as long as you rev-match it first and keep the RPMs sane. Just letting the clutch out with RPMs at idle isn't engine braking; it's a sure-fire way to buy a new clutch (and possibly other expensive, hard-to-install parts!)

@CanAutM3:
I usually rev-match into second gear as I slow down for a traffic light, then push in the clutch as I come to a stop. There's very little wear on the clutch when you do that, and you don't chew up your brakes as much if you let the car slow down over a longer period using engine braking. Personal preference on how you want to balance the wear.

For stop and go traffic I always try to select a gear and constant speed to match the average speed of the traffic. If that doesn't work, I lift off when I see brakes lighting up several cars ahead, and only add gas once the gap to the car in front of me has opened up a bit. Saves a lot of stress, in addition to wear and tear.

Good to hear I've driven manuals for over 25 years and things has changed. Brakes are now more than capable to do all the slowdown of a car street driven for years of hard use. There is no need to save them by engine braking. I used engine braking a lot more in the past but now I use it a lot less and the lesser engine brake in the S55 vs the S65 for example never bothered me at all. But if you like to use it heavily while going on steep downhills there isn't much if any harm done either I guess

The money shift comment was just a lame joke, no offense meant.

[JoeFromPA]

Originally Posted by TheFlyingMouse

Sounds like it's a combination of heavier car, taller gear ratios, and FI behavior that lead to less effective engine braking. I haven't had to go to a lower gear than 4th to hold speed reasonably well down steep grades in my previous cars (usually 5th or even 6th is enough). I guess the F80 is just a different beast and I'll have to make a behavior change somewhere.

Remember that, in some ways, what you might be used to as 5th gear is now 4th gear in this car after accounting for the totality of gearing and powerband changes.

On truly steep grades, I've used 3rd and 4th to control my speed as I simply don't like to have my foot rest of the brake. The engine marvelously engine brakes in 3rd at 5000 rpms (and it's good for your rings!)

[TheFlyingMouse]

Originally Posted by solstice

Good to hear I've driven manuals for over 25 years and things has changed. Brakes are now more than capable to do all the slowdown of a car street driven for years of hard use. There is no need to save them by engine braking. I used engine braking a lot more in the past but now I use it a lot less and the lesser engine brake in the S55 vs the S65 for example never bothered me at all. But if you like to use it heavily while going on steep downhills there isn't much if any harm done either I guess

The money shift comment was just a lame joke, no offense meant.

I guess it's a personal preference. I'd rather hold a semi-constant speed via engine braking as I run down a mountain for 10+ minutes following another car than have to apply the brakes every 5-10 seconds to scrub a 15 mph speed increase, or possibly ride the brakes all the way down. (I suspect you might share the same opinion for this situation).

This is the behavior I was seeing today when I was trying to use 5th and 4th gear engine braking coming down the mountainside from one of the towns near Innsbruck, Austria. I would stay off the throttle and inevitably I would build up 15 mph and have to apply the brakes much more frequently than I would under the same conditions and gears in my current daily driver (128i). I did not want to try third gear at the time, probably because I'm used to it running the RPMs up too much.

Regarding the money-shift joke, I guess I'm just really bad at detecting sarcasm in text, despite perfectly legitimate use of a smilie.

@JoeFromPA:
Sounds like third is the way to go the next time I have to run down a long grade like that, although I don't think I would want it to sit at 5000 rpm. The good news is that my brakes are probably decently broken in by now! I'll have to make sure they haven't glazed before I head out in the morning.

Thanks for the input, guys. Lot of firsts for me on this car and I've only had about 6 hours in it so far (first FI engine, first M, first 3500 lb car, first 4-door, first E.D, etc.). Just trying to figure out how it wants to be driven and loving every minute of it!

[solstice]

Innsbruck, brings back memories from last summer, huge beers along the river with the evening sun just above the surrounding mountain tops, listening to live oompa-pompa and sharing laughs with locals in the beer garden after a fantastic drive from lake Como, through Switzerland and into Innsbruck. Enjoy!

To answer you Q, I did not solely engine brake in the steep downhill through the alps and certainly never at 5k rpms. Preference as you say but for me also a measure of caution of the engine ( valid or not ) and the added dynamics and modulation with using the brakes a bit more.

[Jim B]

That's why F8x cars come with with those BIG DISC BRAKES!!

[rr006rbc]

Use your brakes, stomp on them hard, make sure you wear them out before your warranty goes up. BMW likes to design brake pads to last 51,000 miles so you have to pay for them when you're out of warranty lol. So STOMP HARDER.

[TheFlyingMouse]

Originally Posted by solstice

Innsbruck, brings back memories from last summer, huge beers along the river with the evening sun just above the surrounding mountain tops, listening to live oompa-pompa and sharing laughs with locals in the beer garden after a fantastic drive from lake Como, through Switzerland and into Innsbruck. Enjoy!

To answer you Q, I did not solely engine brake in the steep downhill through the alps and certainly never at 5k rpms. Preference as you say but for me also a measure of caution of the engine ( valid or not ) and the added dynamics and modulation with using the brakes a bit more.

It sounds like we're actually (at least mostly) on the same page. I just want enough engine braking so that the speed does not run away from me and I can control it with light use of the brake pedal. The run today required pretty hefty use of the brakes and reminded me of the last time I'd driven someone's automatic car downhill. It's not really a pleasant experience, if you know what I mean.

We didn't go to Innsbruck proper (I wanted to, but I don't run well on local water... ). Instead, we had an interesting encounter with an angry local in Seefeld, who tried to smash my camera because he thought I had taken a picture of him. I was just starting to frame a part of the town with a mountain in the background and hadn't even taken a picture yet. Everyone else was very pleasant though. I'm also not normally one to like beer, but whatever they make in this region is really good.

[TheFlyingMouse]

Originally Posted by rr006rbc

Use your brakes, stomp on them hard, make sure you wear them out before your warranty goes up. BMW likes to design brake pads to last 51,000 miles so you have to pay for them when you're out of warranty lol. So STOMP HARDER.

Lol. They're going to get me for brake pads and tires for sure. I plan on keeping the car well past warranty unless issues crop up later on. If that doesn't do it, HPDEs and track days will take care of the rest!

[yosman8]

Originally Posted by solstice

But not too low...we had enough money shifts

When I came to the forum for answers to some questions, I definitely didn't come for unnecessary comments like this. Please grow up.

[solstice]

Originally Posted by TheFlyingMouse

It sounds like we're actually (at least mostly) on the same page. I just want enough engine braking so that the speed does not run away from me and I can control it with light use of the brake pedal. The run today required pretty hefty use of the brakes and reminded me of the last time I'd driven someone's automatic car downhill. It's not really a pleasant experience, if you know what I mean.

We didn't go to Innsbruck proper (I wanted to, but I don't run well on local water... ). Instead, we had an interesting encounter with an angry local in Seefeld, who tried to smash my camera because he thought I had taken a picture of him. I was just starting to frame a part of the town with a mountain in the background and hadn't even taken a picture yet. Everyone else was very pleasant though. I'm also not normally one to like beer, but whatever they make in this region is really good.

Smash your camera for taking a tourist picture that he might have been part of, wtf? Never heard or seen something like that in Europe and I lived there for almost 30 years. Don't let it discourage you from keeping that shutter busy, very unusual and not at all part of the Euro culture.

[Squddie]

The amount of engine braking you get not only depends on the compression ratio but also on the stroke/bore ratio.

[VCP]

Sport + has max engine brake. Eff and sport with rev match eliminate the engine brake for a few seconds.

[solstice]

Originally Posted by Squddie

The amount of engine braking you get not only depends on the compression ratio but also on the stroke/bore ratio.

And engine displacement + valve action etc.

[VCP]

The primary factor with this in the F8x is the rev match.

Originally Posted by solstice

And engine displacement + valve action etc.

[solstice]

Originally Posted by VCP

The primary factor with this in the F8x is the rev match.

Not in this case when we are talking continuous engine breaking going downhill.

[VCP]

Oh I see. Like when you are driving a 18 wheeler, lol. All kinds of wrong with that practice.

Originally Posted by solstice

Not in this case when we are talking continuous engine breaking going downhill.