Re: Manual trans driving, saving fuel - coast or downshift? - Saab General Bulletin Board - Saabnet.com
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Re: Manual trans driving, saving fuel - coast or downshift?
Posted by cfishgo (more from cfishgo) on Wed, 15 Mar 2006 13:53:35
In Reply to: Manual trans driving, saving fuel - coast or downshift?, Caarma [Profile/Gallery]
, Wed, 15 Mar 2006 13:06:19
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My theory:
Neither makes a gas mileage difference on a fuel injected car. Basically, if your foot is off the gas, the injectors aren't dumping fuel any more fuel than they would at idle. Does the computer open the injectors more based on maintaining air/fuel ratios? I don't know, but you would have more air running through the engine at higher revs.
Wear and tear is a different matter. If you are engaging and disengaging moving parts, there will be wear. Also, gears are designed to take power in a single direction (as if accelerating), using them to fight opposing forces than they were designed for isn't a real good thing. The forces are minimal though, so unless there's a ton of backlash, I can't imagine a failure.
As for control, brakes stop cars much better than engines & drivetrain. The only exception I can think of is to use the engine drag to keep your car from accelerating instead of riding the brakes. You'd do this on a long hill, where riding your brakes could generate enough heat to damage them (not an issue for short duration braking like a stop light).
Rev matching and downshifting is done to anticipate going from a braking situation to acceleration. Think of it like a race: you'll downshift and rev match to get you in the power band so you can accelerate out of the corner.. you aren't doing it to slow yourself up for the corner (it's the exit and powering out that's important for the gear change)
posted by 66.166.132...
Posts in this Thread:
- Manual trans driving, saving fuel - coast or downshift?, Caarma , Wed, 15 Mar 2006 13:06:19
- Re: Manual trans driving, saving fuel - coast or downshift?, Caarma , Thu, 16 Mar 2006 13:14:00
- Re: Manual trans driving, saving fuel - coast or downshift?, Drew in Hosuton, Thu, 16 Mar 2006 13:22:55
- Ok, I don't get it...., Aaron Gilbert, Fri, 17 Mar 2006 18:25:28
- Re: Manual trans driving, saving fuel - coast or downshift?, TML , Fri, 17 Mar 2006 07:05:29
- Re: Manual trans driving, saving fuel - coast or downshift?, Caarma , Thu, 16 Mar 2006 14:11:06
- Re: Manual trans driving, saving fuel - coast or downshift?, TML , Wed, 15 Mar 2006 14:44:37
- T-7 shuts off fuel for sure, Drew in Houston, Wed, 15 Mar 2006 13:55:29
- Re: Manual trans driving, saving fuel - coast or downshift?, JimBlake , Wed, 15 Mar 2006 13:54:12
- Re: Manual trans driving, saving fuel - coast or downshift?, cfishgo, Wed, 15 Mar 2006 13:53:35 <-- Viewing This Message
- My question, idle or RPMs?, SeeVTSaab, Wed, 15 Mar 2006 13:51:30
- Re: Manual trans driving, saving fuel - coast or downshift?, Craig, Wed, 15 Mar 2006 13:47:20
- Free Wheeling Was an Atribute of Saabs, Ian Glenday , Wed, 15 Mar 2006 13:44:45
- Re: Manual trans driving, saving fuel - coast or downsh, jp, Wed, 15 Mar 2006 13:40:41
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