down shifting and not coasting

[wushumasterku]

Hi folks,
I have a question about driving manual. do you downshift all the time? or do you let you car coast to stop and use brakes when necessary?

i heard that the "modern" engines don't actually use any gas when you leave the car in gear. now is this same as downshifting (when they say leave it in gear?) but when you let your car coast in neutral, the engine actually uses some gas.


I'd like to hear your thoughts on this.

thanks

[DJ_SpaRky]

good question, I am interested to know too as this will be my first manual car.

[celica girl]

Personally I don't downshift unless I'm taking a corner. The way I see it brakes are cheaper to replace than a clutch. Unless you know how to rev-match properly when you downshift I say just pop it into newtral.

[echo_hrs]

Downshift all the way...If you downshift properly you're not going to wear out your clutch...

[celica girl]

Originally Posted by echo_hrs

Downshift all the way...If you downshift properly you're not going to wear out your clutch...

Exactly... that involves rev-matching. I'm not too good at that.

[Idjiit]

Heel-toe'ing is half the fun of owning a manual, so you bet I downshift/rev-match.

As for the technical question, I would be very surprised if downshifting consumed less fuel, but I suppose it's possible.

[SmellyTofu]

Yes all modern engines from the 90's to now run on no fuel when it's at a certain engine speed so yes, downshifting runs over (general rule of thumb is around 1500-1700rpm for petrol.. lower on diesel) will use less fuel than coasting down but you wouldn't use all that much at idle anyway. It also helps emissions in case anyone really cares.

[Idjiit]

Originally Posted by SmellyTofu

Yes all modern engines from the 90's to now run on no fuel when it's at a certain engine speed so yes, downshifting runs over (general rule of thumb is around 1500-1700rpm for petrol.. lower on diesel) will use less fuel than coasting down but you wouldn't use all that much at idle anyway. It also helps emissions in case anyone really cares.

Err... But downshifting would mean higher revs if you're maintaining the same speed.

[SmellyTofu]

Originally Posted by Idjiit

Err... But downshifting would mean higher revs if you're maintaining the same speed.

Your wheels run the engine when you're going down a hill in a lower gear (rather the other way around when you're accelerating). Engine speed doesn't mean you're using more fuel.

Out of interest, drive a car with a instantaneous fuel consumption gauge. You'll find idling at say 80km/h down a hill, you'll be using <0.5L/100km but when you're using engine braking, you'll be using 0.0L/100km.

[TRD_Yaris]

This is an EXTREMELY interesting topic..i've been wondering about this for many years. I love rev-matching on both up and down shifts, and I pretty much coast to slow down for stop lights. but, it would be really cool to use a measuring device to check actual fuel consumption (like in many 90's BMWs)..

[boxerboy]

When the engine is running it is burning gas. I have yet to wear out a clutch in any car. My highest mileage was 108,000 on a toyota tercel mostly city in Dallas. I was a service rep. Any way I almost always downshift, so if the light changes or the traffic starts to move I will be in the right gear to keep moving. When I see that the light has just turn red or traffic is not moving I will just brake. Of course that depends on the speed. I will downshift a higher speeds and not at low speeds.

[why?]

I use my brakes as little as possible, but I don't make the engine brake any more either, as that uses fuel. I just disengage the clutch and coast to a stop.

[Master2192]

When you are engine braking, the ECU turns off the injectors until the rpms get down to a certain value (~1500). This is very easy to see on a AFR Gauge or a scanner showing Injector duty cycle.

I rev-match downshift all the time, and it doesn't add anymore wear to my clutch and my brakes last 2x as long. I believe it is a skill that all manual drivers should learn. It is definitely an advantage to be already in gear if you need to start accelerating again.

[hoahmaru]

I just started driving manaul again when I got my Yaris. I normally leave the gear in neutral and use my break to stop but some of my friends says that it is dangerous especially in the winter time because your wheel will slide easier if you don't have the car in gear. I just wanted to know if anybody knows if this is true or not. And also does the car stop faster if it is in gear or in neutral?

[60 Somethings]

Guess it's time for us older folks to chime in.

We have been driving mostly stick-shift cars for the last 45 yrs - including 3 ALFA's, 3 VW's, a Ford Fiesta, Datsun 510, Dodge PU, Ford Explorer and a Ford Ranger.

We have kept out cars for long periods, replaced very few clutches and required very few brake jobs. Our last two vehicles ('97 Explorer & '98 Ranger) had 114,000 and 90,000 miles respectively and both had the orginal brakes and clutches operating properly when sold. The '79 Fiesta was finally wrecked by our daughter at 180,000 miles and it was still pretty much all orginal. It was the most like our Yaris - very fun to drive.

We brake by downshifting and NEVER coast in neutral. My dad told me at a very young age that you have no control over a car running in neutral. (This was in the early 1950's, and I recently learned he had been an auto mechanic in San Diego around 1914, before he was an airplane mechanic in the Navy in WWl, which was before he was a minor star in silent movies in Hollywood - an interesting man.)

The secret is driving SMOOTHLY. As my wife says, when you are doing it right it's like a dance. As others have said, brake going in, rev up, back-shift and accelerate out. The Yaris is very quick thru tight turns.

I am currently experimenting with driving styles and gas mileage. Got 37MPG on last tank driving more spiritedly.

Must note thet we have had problems with two of our manual transmissions - both the result of towing, not normal driving. It's also the reason we now tow with a 2006 4Runner V8 - with an automatic transmission.

[ricko]

This is a great thread. I had no idea that ECU technology was that "smart"!

Although the original question was in reference to coming to a complete stop, my comment relates to the car's behaviour while cornering. Downshifting and keeping the power on (even very moderately) has the advantage of keeping the suspension under load, which improves the car's ability to make the turn. It is safer to drive around a corner than it is to coast around. The process is: brake to reduce speed, downshift, and drive through the corner (the more skilled can do this all at once). This SEEMS to be especially true for front-wheel drive vehicles, although I have no concrete evidence to back this up. Maybe someone can explain the physics of cornering and braking in better terms for us.

[plushDJ]

I'll downshift from 4th to 2nd but that's about it

[pennystocks]

Bad news, the yaris doesn't "en-lean" when engine breaking. All the GMs i'v owned you could really feel it kick the fuel flow down when engine breaking. My aurora you could see then MPG increase when engine breaking, it auctually got less MPG when in neutral vs drive for coasting.

My scan gauge shows 0.2 Gallons Per Hour when costing in neutral for the Yaris. I did some engine breaking in 2nd and it was around 0.5 GPH. Also when you feel that slight engine break when coasting (you can slightly feel it kick in and out on my auto) is putting the PCM into open loop for a couple of seconds and the GPH is the same as in neutral. Also coasting it reads about 200-250 MPG and when downshifting it drops to 60-100.

I dont think there's a need for the yaris to enlean tho. I just did a trouble code test on a chicks car at work and her 2000 or so neon 4 banger showed 0.6 GPH at idle. I cant imagine what my aurora was at at idle. So thats round 5 hours for the car to idle out a gallon of gas. and 2 days to idle out a tank, not too shabby :)

So coasting in neutral is the best way in the yaris for MPG. BTW full throttle is around 6-7 GPH and normal driving is 1-3 ish and idle w/ the AC on is 0.3 and auctually shutting the car off while long coasting can add 1 or 2 MPG as long as its done on a normal basis. I have an auto so it kinda sucks to crank the starter 50 times a day. Just think of them as free miles that dotn cost you $$$ :)