Engine Braking w/ignition off

I used to drive downhill for long distances (descending from treeline to 5,000ft) here in Colorado and sometimes I just wanted to completely implement gravity. I've driven quite a few times downhill with the ignition off but the engine in gear. This practically made the fuel cost one-way whenever I went somewhere in the mountains.

The cool thing here is that you are not using any energy (fuel), but you still have power steering and brake booster vacuum. You can always flick the ignition switch to "on" if you need power. I can't think of anything I could be harming while doing this.

Has anyone ever done this? Any downsides/ dangers to engine components?

Almost every night while going to night school in a Ford Pinto. Once at the top of the hill and ridge the road ran along, if I was doing 60 on the nose, I could go from Bloomsbury to Quakertown and never touch the ignition. There was one spot where you would really slow to 15 or 20 for a few moments and had to watch for lights behind you. It was "an exercise in energy management" because the radius of each turn counted.

In older cars that made sense, as even when coasting there was fuel being sucked in through the carburetor or throttle body (early fuel injection), but on modern cars that is useless, as on most gears when you are coasting above a certain rpm the engine cuts fuel delivery completely.

I am almost 100% certain SAAB Trionic 5 cuts fuel completely on third, fourth and fifth gear when there is zero load on the engine (e.g. coasting), and it cuts fuel above 1800 rpm in second gear with no load. On first gear I think there is still fuel delivery when there is no load. People more versed in Trionic tuning may chime in and correct me.

Off topic, are you in the military? Moving to Europe, and where?

Interesting. I like to drive using the minimum amount of energy, even if it is unsafe at times. You can really control things with the c900.
Thanks for the clarification- I knew ECU's probably had some sort of a feature that cuts fuel supply on coasting but was never sure of it.

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Off topic, are you in the military? Moving to Europe, and where?

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No, I was born and raised in Bulgaria. I spent some years in the US but now it's time to go back- there are a few projects I am planning which I cannot complete here. Definitely planning to be back to the US some day, perhaps as a tourist this time.
Since I just sold my Saabs, people think I am done with the brand but that's far from true.

Before the days of ignition locks I would run it up to 60 and then just shut the engine off and coast in neutral.

These were also the times that I was into soaring (as well as flying), and those quite moments either in the air or on road were great times of peace.

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Originally Posted by nuclear944

Interesting. I like to drive using the minimum amount of energy, even if it is unsafe at times.

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In that case you should mount the narrowest tires available and pump them up to 60 psi.

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Originally Posted by nuclear944

No, I was born and raised in Bulgaria. I spent some years in the US but now it's time to go back- there are a few projects I am planning which I cannot complete here. Definitely planning to be back to the US some day, perhaps as a tourist this time.

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Ah, the great diaspora. There are lots of foreigners leaving the US, all the Brazilians are gone from South Florida and Atlanta (and I am sure other places). The few left are guys like my dad who have business and roots in the US.

My dad has a friend from Bulgaria, he used to work for the [FONT=sans-serif]КДС[/FONT], the Bulgarian KGB, and defected in the early 90s when all went to shit in the USSR. He now owns a spy shop in the US.

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Originally Posted by rpiereck

Ah, the great diaspora. There are lots of foreigners leaving the US, all the Brazilians are gone from South Florida and Atlanta (and I am sure other places). The few left are guys like my dad who have business and roots in the US.

My dad has a friend from Bulgaria, he used to work for the [FONT=sans-serif]КДС[/FONT], the Bulgarian KGB, and defected in the early 90s when all went to shit in the USSR. He now owns a spy shop in the US.

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My family wasn't too affected by the USSR or its collapse, but we did lose some land and property. Both my parents and two of my grandparents were teachers/ headmasters at some point. My father did try to start a business here a few times here, but it was unsuccessful. We pretty much came at the worst possible time for the things we were trying to achieve.
This is his website: http://www.sarikov.com (maybe mods will be merciful and let this one pass)

Back on the subject:

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[FONT=arial]In that case you should mount the narrowest tires available and pump them up to 60 psi.[/FONT]

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I see. That would create the least rolling resistance I assume. I always pump the tires to 50psi on our Metro. Gets 50+mpg.
There is a fine line between performance and economy, and I think this is where a Saab scores top marks. Someday when I get my project c900 notchback, I want to implement some sort of a system where you can switch between "economy" and "performance". Maybe something that limits the fuel flow or something like that. Also, some sort of a electromagnetic clutch at the power steering pump which lessens the load on the engine.
I'd also want to convert it to direct ignition.

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These were also the times that I was into soaring (as well as flying), and those quite moments either in the air or on road were great times of peace.

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You are pilot? I am quite the aviation addict. Also, I'm finishing up my private pilot certificate this spring.

You kind of remind me of my dad's Bulgarian friend, he is quite the mechanical freak (and I say that as a compliment), always with weird ideas for new machines and contraptions. He is the kind of guy who would buy his cars at a junk yard and make it work with a hodgepodge of parts!

I say your C900 already has a system that can switch from economy to performance.... it's called the accelerator pedal! :lol: Press hard for performance, press lightly for economy!

I'm also an aviation nut, grew up listening to grandpa's stories of flying a DC-3 in the Amazon jungle after WWII, and with grandpa taking me to the airport to see aircraft take off all day! Now I am a helicopter maintenance supervisor and on the way to finish my PPL.

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Originally Posted by rpiereck

You kind of remind me of my dad's Bulgarian friend, he is quite the mechanical freak (and I say that as a compliment), always with weird ideas for new machines and contraptions. He is the kind of guy who would buy his cars at a junk yard and make it work with a hodgepodge of parts!

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Yep. That definitely sounds like me.

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I'm also an aviation nut, grew up listening to grandpa's stories of flying a DC-3 in the Amazon jungle after WWII, and with grandpa taking me to the airport to see aircraft take off all day! Now I am a helicopter maintenance supervisor and on the way to finish my PPL.

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Well what do you know! Surely our interest in Saabs isn't coincidental!
I'm a fixed wing guy though...Currently struggling with the c172r's performance charts- damn density altitude here in Denver! My flight school recently bought a Maule M-7 and perhaps that's the aircraft I'm going to finish my PPL rating on. The Cessna's build quality is appalling and fuel consumption isn't much worse due to the poor aerodynamic qualities.
Definitely considering a experimental aircraft project in the future..

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Originally Posted by nuclear944

This is his website: http://www.sarikov.com (maybe mods will be merciful and let this one pass)

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Back off subject...

That stuff is amazing! He's very good at what he does!