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kaismaeel2000
02-25-2007, 01:35 PM
Any word about the coming 535i fuel economy? Do the twin turbos mean better or worse fuel economy? BMW.com says 5.9 to 10.9 l/km in "combined" fuel economy, but it does not say for which engine though.

BmW745On19's
02-25-2007, 01:44 PM
Any word about the coming 535i fuel economy? Do the twin turbos mean better or worse fuel economy? BMW.com says 5.9 to 10.9 l/km in "combined" fuel economy, but it does not say for which engine though.
Turbos usually help with efficiency as you can get to and maintain a speed with less gas because the turbos help boost power.

Ugly Bear
02-25-2007, 04:57 PM
I believe 535 is the same as 530. BMW added some 'hybrid'-like features like bigger battery which rechanges from braking and is able to power car network without consuming power from the engine. Also, A/C disconnects from the engine when not needed, reducing engine load.

SteVTEC
02-25-2007, 07:09 PM
Turbos usually help with efficiency as you can get to and maintain a speed with less gas because the turbos help boost power.That's on diesels, not petrols. Diesels and turbochargers were practically made for each other, but it's not quite the same on petrols. Usually petrols take a pretty big efficiency hit because they need to have lower static compression ratios which kills your off boost cruising efficiency, and then they take another efficiency hit because they need to have richer air fuel ratios to avoid melting the turbos. The BMW N54 is one of the best turbocharged petrol engines to date. Direct injection improves knock resistance and lets them still run a decent compression ratio so off boost cruising efficiency is good, and then they're using advanced materials in the turbos to make them a lot more heat resistant which lets them run leaner A/F ratios. Without all this technology the N54 would have had much greater fuel consumption, like most other turbo petrol engines.

Ugly Bear
02-25-2007, 09:46 PM
From UK LCI briefing papers 530i is about 10% more fuel efficient

not_too_shabby
02-26-2007, 11:21 AM
The way I look at turbos is analogous to a displacement on demand system. When you are not using the turbos, for instance just cruising down the highway at moderate speeds, you would get the fuel economy of an engine with similar displacement. When you accelerate quickly and spool up the turbos you get fuel economy more consistent with the peak horsepower rating of the car because the turbos force more air into the cylinder effectively increasing its displacement. For instance on our saab 2.3T, it has 220 HP. Going down the highway you get 30MPG no problem because you get the fuel economy consistent with a 2.3L four cylinder. Around town the mileage is more around 20MPG, because you are using the turbos more to accelerate from stop lights, etc.

shabbaman
02-26-2007, 01:55 PM
Any word about the coming 535i fuel economy? Do the twin turbos mean better or worse fuel economy? BMW.com says 5.9 to 10.9 l/km in "combined" fuel economy, but it does not say for which engine though.

Look at the fuel economy of the 335i. 535i should be equivalent.