musclecarconvrt

Wow. Guess I need to change an old habit. I often coast down long hills. Going to be leaving it in gear from now on.

Stavesacre21

I must say that this fuel cut-off comes as a pretty big surprise! Just as with Raptor, I too have always coasted in neutral...very very rarely in gear! However, it's gonna take some getting used to though.

I'm a lil surprised at the inactivity of this thread as well! This is pretty awesome...definetely gonna have to try it out.

MazdaManiac

iTrader: (3)

Fuel cut doesn't care if you are in gear - when the PCM sees no throttle input and the wheel sensors are still spinning, it pulls fuel until the RPMs get down to 2200 or so.
You can prolong the agony by leaving it in gear, but the fuel difference is negligible.
The main reason for fuel-cut is anti-buck, not fuel economy.
I suppose over the life of the car the 1/2 to 3 seconds or so that you are not under power while moving might add up to a mililiter or two...

Freddie

I was taught at an early age, by some damn good drivers, never to coast long distances in neutral, especially down hills. Low speed up to a red light or backward out of my gently-sloping driveway, stuff like that would be OK. Reasons given were lack of control (RWD), delay in accelerating if needed, and brake wear. Downhill at highway speeds, stay in appropriate gear for amount of engine braking desired. 'Never thought about fuel consumption but now that we know about this DFCO, add that to the list of reasons. Also coasting downhill in neutral is illegal, at least in California, presumably for the other reasons listed.

Gomez

I go through a dozen sets of traffic signals on the way to/from work each day. I decelerate up to a red light rather than coast up to one (because I enjoy using the gearbox....not the brakes). I'm hopeful that in the fullness of time I'll find this practice allows me to one day drive up to the bowser......not push my car to it!!!!

I agree......you're not going to add 20 miles to a tank during normal driving. You might add one or two though, and that may make the difference one day .

Raptor2k

Yeah, my tank is at the half way line and I have my usual 120 miles. I did play around with a WRX for a little bit, however, so meh. Oh yeah, the synchros sound sweet.

AdRoCK3217

Yeah, I'm at 1/2 tank right now, with 120 miles..


I did 2 highway pulls with a 3000GT, paced my brother in 4th at like 7000RPM for about 10 minutes, raced my brother in his MSProtege, and have been doing a good amount of general buzzing around.


Heh.

kuleto

I didn't read all the responses to this thread but why would you coast in neutral. If you ever had to make an emergency manuver, it would take more time to stick it in gear. And if you keep it in gear while decelerating it, it's easier on the brakes therfore leading to longer life of the brake pads/rotors. It also prevents the pads from overheating and obviously you slow the car down faster while in gear.

Gomez

We've had this debate here a number of times in the past. Any minute now you'll get some geezer pipe up about how brake pads are cheaper than gearboxes. Don't use engine braking....use your brakes, dumbass.

Funny thing is though, in over twenty years of driving manual cars, I've never had a clutch or gearbox replaced. Spent plenty on brake pads/rotors though.

MazdaManiac

iTrader: (3)

'Cuz brakes are cheeper than clutches!

That said, I tend to use whatever forces are available to me - I'll leave it in gear and keep the clutch in while I use my brakes and then gradually slip the clutch back on to apply some engine braking.
Hell, I pull my e-brake on the highway sometimes if I don't want to give away my intention to slip back into a spot in another lane when I've been shut out by a crawler.

Gomez - you've never replaced a clutch? You must not hold onto vehicles for long.

Gomez

The RX-8 is my second new car. All the used cars I've purchased in the past have been vetted by me for abuse before purchase. I like to buy something that hasn't had the bejeezuz thrashed out of it.

I drive in a spirited fashion....but I'm mechanically sympathetic. I don't burn rubber.

MazdaManiac

iTrader: (3)

I didn't push my Honda too hard, either. I still used up the clutch by 100k miles.
Most are designed for about 60k miles.
I've never owned a vehicle that didn't require a new clutch at some point and I've mostly bought new since 1987.
I have plenty of mechanical empathy, but friction is friction.

Stavesacre21

I've always agreed with the old fashioned "pads are cheaper then engine/trannys" slogan.

Its for this very reason that I find this decelleration fuel cut-off to be so interesting...because i've always been one to use brakes, not an engine...to stop.

I haven't read into any past debates about this, but I find this to be pretty intregeing.

And btw, my old daily driver has about 80K miles on the clutch....still no slip whatsoever.

Gomez

100k, bloody hell.

I've owned 16 cars. I've only had one that I kept for more than 40,000 miles.....and it was an auto. My RX-8 has done 30k miles.

CarAndDriver

MazdaManiac

iTrader: (3)

Ah, OK. I'm only up to 11 over the last 24 years, but I drive them.

Smileynh

Wow, you all kill clutches. My infiniti g20t had the original one at 120k till I Sold it.

It was alot of hwy miles but I still had a spirited 20 miles of curvy backroads to drive everyday.

Astral

I think the wear on the transmisison when decelerating in gear is rather minimal--not much different, surely, than acceleration, and probably even gentler? And the engine is probably not worn all that much either by deceleration with fuel cut off.

So really the only wear point is during downshifting, if you don't revmatch and end up slowing the car down via clutch friction.

Georgia8er

It's also illegal in most states to coast...

zaglo6204

werd...

zaglo6204

really? i wonder how they could ticket you for coasting...

SoFL_RX8

As Astral said earlier, I always keep it in gear because then you're always in controll. In spirited driving I dont see any situation where it would be benifitial to be breaking in neutral as apposed to downshifting to engine break or heel/toeing. I always rev down to at least 3rd gear before putting in the clutch and breaking. Trust me, downshifting comes in handy when the light changes in the middle of you decelerating and you wanna get back on it in a hurry.
I had no idea this had an effect on our fuel economy though. Nice to know that my style of driving is conducive to how the car is tuned.

Georgia8er

It's unusual, and I haven't heard of a case made in years. It mostly applies to road tractors and other very large vehicles.

SoFL_RX8

Seems to be a safe law to have for vehicles of that size and weight... I wouldnt want any trucks near me coasting in neutral, especially going down hill!