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Old 06-24-2013, 09:20 AM   #4 (permalink)
ever_green
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Join Date: May 2011
Location: Toronto
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gueff - '19 Mercedes Benz A250 4MATIC AMG
90 day: 30.55 mpg (US)
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get up to speed how? if you mean WOT then no, that gives me horrible mileage. anything above 3000rpm and my car really burns a lot of gas. high load and over 2500rpm it also burns a lot of gas. I found being gentle is the best. accelerating at 30kw power range.

Quote:
Originally Posted by TheEnemy View Post
There are a couple of things going on there.

First most engines have their best BFSC at about 2000 rpms give or take.

Second at full throttle most engines run a little rich to prevent detonation.
I certainly never go full throttle. just a 1/3 throttle is enough to achieve 0 vacuum at 1500rpm. but it seems it would be better to shift at say 2000rpm vs. 1500 from my experiments while making the same amount of power. the difference is not that great but its there...this is for around town driving though. on the highway I can pass without downshift due to the 4.11 final drive that puts me in 2500rpm at 65mph. but I found whether I pass at full load or ~70% manifold pressure doesnt make much difference at those speeds.

so in my notes higher loads are better at higher vehicle speeds while lower loads lead to better results in city driving.
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Last edited by ever_green; 06-24-2013 at 09:31 AM..
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