Random Thoughts... [Automotive Edition]

It was 45? here this morning, so I had to put my heated gloves on before riding off. And it's Spring Break here, so there's no morning traffic. And it'll be low 60s this evening :whistle:
 
When did idling become more economical than engine braking?

Apparently, my dad's Skoda Yeti disengages drive and drops to idle whenever you let go of the throttle. Coasting in neutral means it has to burn fuel to idle.

Engine braking (or coasting along in top gear, rather) does not. What am I missing here?
 
JimCorrigan said:
I should neg rep you for that. :p
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I try :D

JimCorrigan said:
I was referring to the blatant teasers in this video:

2018-Ford-Mustang-Bullitt-4005.jpg


(Start at 3 min mark)

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Hey! I used to walk by that room all the time! Never been in it though.

On a separate topic, we used to have a thread on here that cataloged all the automotive idiot fail threads out there, but I can't seem to find it. It had stuff like the DEI guy, the NOS energy drink in a GSX-R gas tank guy, the tranny oil in a WRX engine guy, etc. Can anyone helped me find that thread? I can find all the individual cases, but I believe that thread had more that I can't think of right now (and I want to send it to some coworkers who aren't familiar with some of these cases).
 
I did some plowing for my parents since they are away in Florida. This is the second time I have done it and the second time it was during a major snowstorm.

The "plow truck" is a Jeep Wrangler. It was not designed for this. There is way too much weight over the front end so the rear slides around all over the place and gets you into compromising positions. The oversize tires and not-enough-lift kit do not help matters. Just getting out of the uphill driveway was nearly impossible, the Jeep does not have enough weight to push the snow for more than a few feet at a time. The electric cable for the plow controls kept coming loose which is always fun in a blizzard.

It's not really much to complain about since the Jeep fine in anything less than state of emergency weather, and it's not like anyone else was having an easy time, but it sure wasn't fun.
 
You should be able to hook up a badass snow blower apparatus to the front instead.
 
CrzRsn said:
Meanwhile in Michigan, we got about 1 inch of snow on Monday and it took me 2 hours to get to work instead of the usual 30~40 minutes.
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At least here, 50ish miles north, we had a bit of rain mixed in that early on. Still no excuse, salt trucks should have been out. But as always, people suck at driving when,... well, always.
 
FG Aussies - do you think it's possible to source a set of 302 Cleveland heads at a junkyard or swap meet for a reasonable price?
 
Perc said:
When did idling become more economical than engine braking?

Apparently, my dad's Skoda Yeti disengages drive and drops to idle whenever you let go of the throttle. Coasting in neutral means it has to burn fuel to idle.

Engine braking (or coasting along in top gear, rather) does not. What am I missing here?
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IIRC the answer depends on whether the vehicle is diesel or gasoline powered. I presume it's an automatic by your description?
 
I remember my 1987 Oldsmobile always seemed like a "fast coaster" to anyone who drove it, because it wouldn't slow down when the engine slowed. It would "free wheel" coast.

As for economy, well...I suppose if you are coasting in "neutral", you are slowing down less, so that you don't have to apply as much gas to get back up to speed...so there's that. :dunno:
 
NecroJoe said:
I remember my 1987 Oldsmobile always seemed like a "fast coaster" to anyone who drove it, because it wouldn't slow down when the engine slowed. It would "free wheel" coast.
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I picked up some rusty steelies free of charge and put them in the trunk of my Polo. Surprisingly I don't think the free wheels make it coast any better.
 
Spectre said:
IIRC the answer depends on whether the vehicle is diesel or gasoline powered. I presume it's an automatic by your description?
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It's a 2.0 TDI and yes it's a DSG. It's just half a year old, but the Yeti is not on the MQB platform so it lacks some tech (it doesn't have radar guided cruise control, for instance) but Skoda still gave it the same engines they put in the MQB cars.

And AFAIK both diesel and gasoline powered cars shut off fuel delivery completely during engine braking.
 
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Perc said:
It's a 2.0 TDI and yes it's a DSG. It's just half a year old, but the Yeti is not on the MQB platform so it lacks some tech (it doesn't have radar guided cruise control, for instance) but Skoda still gave it the same engines they put in the MQB cars.
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Since diesels can provide virtually zero effective engine braking without the installation of either a compression release brake or exhaust brake (neither one of which are fitted to most passenger car diesels), there's no point in trying to engine brake unless you have some really short gears - that's how you sort of counterfeit engine braking with a diesel. So, if you don't have stupid short gears, you might as well declutch the rest of the drivetrain from the diesel and let it coast for better fuel economy.

And AFAIK both diesel and gasoline powered cars shut off fuel delivery completely during engine braking.
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No, they don't shut off fuel delivery completely on decel. They cut fuel back to idle levels or sometimes (rarely) a little less, but they never shut off completely. If you did, especially on gasoline powered cars, you could get a lean condition that burned holes in pistons if you should suddenly open the throttle with the fuel cut off and it suddenly had to inject more fuel. The catch is, the "idle fuel level" is adjusted for current RPM so it doesn't go piston-burning lean on run-down. Sitting at actual idle RPM consumes less fuel than an engine with a closed throttle at 3000rpm.
 
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I've been reminded that there *are* a few systems out there that actually do completely shut off fuel to the engine on coast-down, but they're under a decade old and most new cars still don't have it.

However, there's a relatively easy way to see if a gasoline car is doing that - simply tap a noid light in to a fuel injector connector and watch it.

The issues with fuel cut on decel are also some of the reasons why 'variable displacement' or 'displacement on demand' cylinder deactivation systems proved a quite hard thing to reliably achieve.
 
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My driving school had Peugeot 306 hatchbacks with the HDI engine, first-generation commonrail from the mid-to-late 90's. They had a trick aftermarket fuel economy computer thing on the dash and it most certainly showed 0.0 (liters per 100km) during engine braking. Ecodriving was a thing even 17 years ago (has it really been that long?) so we did quite a lot of the stuff.

My own car shows 0.0 too, when I set the OBC to show current fuel consumption. I have to downshift a gear (or three, out of 7) to achieve 0.0 but still.

And I know perfectly well that diesels don't achieve much engine braking. I drive one every day and has done so for a long time. But it obviously still slows down the car better than coasting in gear does. Not that slowing the car down is the point of this discussion, anyways.
 
Perc said:
My driving school had Peugeot 306 hatchbacks with the HDI engine, first-generation commonrail from the mid-to-late 90's. They had a trick aftermarket fuel economy computer thing on the dash and it most certainly showed 0.0 (liters per 100km) during engine braking. Ecodriving was a thing even 17 years ago (has it really been that long?) so we did quite a lot of the stuff.

My own car shows 0.0 too, when I set the OBC to show current fuel consumption. I have to downshift a gear (or three, out of 7) to achieve 0.0 but still.

And I know perfectly well that diesels don't achieve much engine braking. I drive one every day and has done so for a long time. But it obviously still slows down the car better than coasting in gear does. Not that slowing the car down is the point of this discussion, anyways.
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My gasoline powered 1987 XJ6 shows 0.0l/100 or 99mpg on its internal trip computer when you let off the gas and coast down. I know for a fact that it's not cutting fuel completely. Same thing with most other cars I've had that have a fuel computer from vintage to recent - the fuel injectors are still firing even though the computer claims no fuel is being used.

On many OBD2 cars you can connect a scanner as you drive around and see what the injectors are doing. With the exception of some recent models, you will see that the duty cycle never goes to zero and the pulsewidth never goes to zero on coast-down.
 
Have anyone ordered something from Faxon Auto Litterature? The have a few things of interest but I don't want to be scammed.
 
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