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Old 11-09-2007, 05:57 PM   #11
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Blanket statements like 'an engine operates most efficiently at such and such RPM' won't necssarily get you the best fuel economy. All engines are somewhat different. To think that, say, an old-school carbureted two-valver is going to have the same efficiency curve as a fuel injected four-valver is simply absurd. So, in order to determine the best shifting RPM for fuel economy, experiment.
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Old 11-09-2007, 08:22 PM   #12
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i can't experiment without a supermid, hence why I want one, unless I drive consistently one way on an entire tank, and then another on another tank.

clencher: so you think then that it's prolly better to leave it in 4th and go for not full enrichment rather than puttering up in 5th with barely enough power?
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Old 11-10-2007, 10:40 AM   #13
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Quote:
Originally Posted by civic94 View Post
I had a supermid before but i sold it since i drive 100% city now, with tons of stop and go, so i dont want to concentrate on looking at it when theres alot of people and cars around me, can be dangerous
I think you don't have to watch the SuperMID display all the time.

It tells you the fuel efficiency results among different driving styles, then you will be able to find your best technique to get the best results on your own route.

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Old 11-10-2007, 02:17 PM   #14
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Quote:
Originally Posted by theclencher View Post
ftw?

you aint no noob are ye?

get in top gear asap but don't floor it on the way there
If I get in top gear goign up the hill, i have to hold the pedal down as much as it will go in order to make it up without lugging. If I leave it in fourth, I don't hvae to go full enrichment (maybe 80% instead, prolly not 60%) and fourth gear is only about 20-25% faster revs. Prolly bout the same either way.
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Old 11-11-2007, 07:52 AM   #15
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Just shift without fuel, from a standstill with ice on idle get up to 20mph's or so then shift back to 4th and slowly get up there. If you have a light that might be helpful, but I usually give it just a tee bit of fuel after I get up to some kind of speed. However, the clutch is the only pedal in use until that car is idling in 5th, then after I drop to 4th I give it a notch.

My 1.8 litre does fine if from a standstill I let out the clutch easy and wait until the rpm's are at 800... First gear is the only gear I let out the clutch easy, once the car gets going that clutch comes out quick. First gear hardly takes a few seconds, second is almost as easy, third works the ice some and 4th tests it, but a high compression ice will get up to idle rpm's even in 5th.
So once idling in 1st then I shift to 2nd the rpm's drop to 5-600 and the engine's idle power gets it back up to idle speed, then shift again into the next gear, repeat until idling in 5th.
Once at 750-800 rpm's in 5th, take back down to 4th and give it just a tee bit of fuel, this should get it up to 30-35mph then back to 5th and once again a wee bit of pedal, voila.

The technique is a little bit like a ice OFF rolling start down hill, except this works best on level ground.

Notes: Doesn't work going up a hill
> Depending on ice compression some cars may not do well past 4th gear, the higher the compression the better the highest gears work, also 5th should be no real problem on a 6 or 7-speed transmission thou into and past 6th might not work on any.
> You could probably give it a go, when idling in 5th don't down shift but instead use 5th with an ultra light foot on the throttle, I find this tests my patience too far thou theoretically it should work.
> Yes you need a manual trans

Car used for the above technique: 1991 bmw 318is.
My mpg: 25 - 28, worst 22 best 30
EPA mpg: 17 - 23

Quote:
Originally Posted by StorminMatt View Post
Blanket statements like 'an engine operates most efficiently at such and such RPM' won't necssarily get you the best fuel economy. All engines are somewhat different. To think that, say, an old-school carbureted two-valver is going to have the same efficiency curve as a fuel injected four-valver is simply absurd. So, in order to determine the best shifting RPM for fuel economy, experiment.
Thank you.
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Old 11-11-2007, 08:34 AM   #16
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I found that a takeoff from a stop at 500 rpm and shifting at 1000 into the next gears to get back up to 30mph impacted the trip MPG the lease with light throttle - which lugs it anyway at that low an rpm. Lubrication does a weird thing at low RPM - here is a graph of Synlube vs Regular lubricants.
Attachment 1065
So you want to stay in the mid-rpm range for reduced friction whereas with Synlube I can go really low on the RPM and still have only a little friction.
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Old 11-12-2007, 08:51 PM   #17
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Originally Posted by JanGeo View Post
I found that a takeoff from a stop at 500 rpm and shifting at 1000 into the next gears to get back up to 30mph impacted the trip MPG the lease with light throttle - which lugs it anyway at that low an rpm. Lubrication does a weird thing at low RPM - here is a graph of Synlube vs Regular lubricants.
Attachment 1065
So you want to stay in the mid-rpm range for reduced friction whereas with Synlube I can go really low on the RPM and still have only a little friction.
Oh I'm sorry, yeah I do run synth in everything, I like that chart.

Amazing, I discovered most of these things on my own, never knew there was a world of like-minded folks.
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