Gas mileage

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Permalink Reply by mr bad example on July 15, 2008 at 11:43pm

matches my performance, 53mpg at 55-60mph. my first tank was 37mpg in january in chicago. my last tank of mixed driving was 45mpg.

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Permalink Reply by Bruce Fromoz on July 16, 2008 at 2:38am

I hope, someday, to equal your performance. I'm thinking the only way to improve this configuration, is to add a supercharger. My other car has a factory install, and it surprises me at times. (wanna pic?) Anyway, it's efficeintcy plus, and I'm betting that in this setup, it would be far superior to a turbocharger. Not for speed, but for economy.

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Permalink Reply by mr bad example on July 16, 2008 at 3:10am

i can't picture a supercharger in that little cubby hole the smart engine resides in. i've had a metro and justy where you could crawl in with the engine, so much room. the justy had guts and could smoke tires in first and second, the metro was lucky it could get out of it's own way.

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Permalink Reply by Tim Cowan on July 16, 2008 at 10:03am

Why? Supercharging robs horsepower because it is belt driven off the engine. It has to replace this horsepower before it ads a thing. Exhaust driven turbo boost is FREE. With a proper intercooler there is no compairison on a small engine. See Mini. If your talking about doing a large V-8 , the 4-6% belt loss is nothing. See NHRA. How many Supercharged motorcycles do you see vs turbo? This comes from 30 plus years of working with turbos and boost.

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Permalink Reply by mr bad example on July 16, 2008 at 10:04pm

why do top fuel dragsters use superchargers? it takes a second to "spool up" and the boost is on. once you're going, you got boost, and you got that all down the road, when you're at speed.

a smart would have the same performance with a supercharger at a smaller engine size. a turbo blocks the exhaust, turbo lag and it's blocking the free flow by it's existance. 12 years ago i worked at ford, they used superchargers on the t-birds, not turbos. turbos rob power by restricting exhaust (see the doug thorley exhaust vids).

4-6% belt loss is nothing to the 10% gain with a thorley exhaust. do the math. you choke a smart with a turbo.

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Permalink Reply by Bruce Fromoz on July 16, 2008 at 2:30am

I find that due to excellent design, our A/C effects our mileage less than most vehicles. The computer is on the job once again. It seems to do split second actuations based on demand of horsepower, and shape of the darts that I sweat! But out on the freeway, it loafs.

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Permalink Reply by 451 Kahn on July 16, 2008 at 3:47am

How about trying this and see the results you get.


Basically this technique calls for choosing some optimum speed, say 65, and gently pulsing up to about 5 mph above that before gliding back to a speed about 5 mph below it. In this case, a person would be ranging from 60-70.

Since our smarties are so quick to decelerate via the engine, you can extend the glide by shifting into neutral as soon as you hit your optimum+5 speed. This simply prolongs the glide and forces you to pulse (accelerate ) less often.
This came from another Smart web site.

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Permalink Reply by mr bad example on July 16, 2008 at 11:49am

i pop into N when i see a red light far ahead and coast til i have to stop, once in a while traffic will start moving before i come to a stop and have to pop it back into D. sometimes the tranny will pick the right gear, sometimes it'll go "one too low" and the engine will rev a bit. too bad you can't select the gear to drop it into like a regular manual tranny.

i'm just hoping i'm not damaging my smart putting it back in D while coasting.

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Permalink Reply by Dino on July 16, 2008 at 10:48am

This milage does not sound correct. While the cars that we are tuning are seeing an 8-10% improvement in milage, they were starting in the 40's, not the 20's. You are getting BMW 3 series milage. There is something amiss.

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Permalink Reply by Dorenda Truesdale on July 16, 2008 at 10:58am

I agree. As I stated earlier, I have taken it to the dealership and they stated that nothing was wrong with it and that i needed to use premium gas. I do use premium gas. In fact, used mid grade in it at first and got better gas mileage. My husband suspects that it was some glitch in the computer and now that the dealership has reset it, it will do better. We'll see.

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Permalink Reply by Dan on July 16, 2008 at 7:24pm

I am sharing the same low gas mileage. I just filled it for the 3rd time and after a tank's worth of my most conservative driving possible – I only averaged 32 mpg.

I am planning a trip back to the dealer to have it looked at.

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Permalink Reply by BJ on July 16, 2008 at 9:29pm

Check the tire PSI. You might be running on low PSI. The front 31 back 35 or check MR Bad Example posts on PSI.

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