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Old 10-12-2018, 07:28 PM   #141 (permalink)
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Originally Posted by 19bonestock88 View Post
My ex got 28mpg hwy with her 2011 1.4T Cruze while my 2004 Saturn with its 2.2 liter engine got 30-32hwy when stock, at a similar speed
But @ far lower rpm

When not pulsing & coasting, I do 20mph / 30kph zones in 4th these days
Barely above tickover with a 1L (atmospheric) , small car.

Great mileage due to low rpm.

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Old 10-13-2018, 12:31 AM   #142 (permalink)
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New turbo engines have relatively high compression. Plus direct injection, which theoretically gets you much better idling efficiency.
Direct injection usually can do miracles in regard to fuel savings.
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Old 10-13-2018, 02:27 AM   #143 (permalink)
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^ How many furlongs per bushel are you getting?
A lot, damn animal was stuck in eco-mode

Driving back home gave me the chance to try and find out a bit about my car's DFCO (which only seems to work above ~40MPH), so I've learned a lot yesterday!
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Old 10-13-2018, 03:25 AM   #144 (permalink)
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Direct injection usually can do miracles in regard to fuel savings.
The problem is when she's running hot, she's running hot. Fuel economy goes out the window.
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Old 10-13-2018, 03:19 PM   #145 (permalink)
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With numbers like that, will it just convince people the V8 is the way?
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Old 10-15-2018, 12:36 PM   #146 (permalink)
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So these turbo engine vehicles might get better fuel economy in stop and go driving, but worse in steady cruise?

I know Toyota gave the Gen III and IV Prius a larger displacement than the Gen I and II. Displacement must not be such a huge economy penalty as long as you can keep the engine near the BSFC sweet spot.
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Old 10-15-2018, 01:57 PM   #147 (permalink)
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Originally Posted by niky View Post
The problem is when she's running hot, she's running hot. Fuel economy goes out the window.
Well, at least with port-injection and a lower compression ratio, not only there is some temperature drop in the air intake due to the fuel vaporizing but also the aerodinamic heating is not so intense. No wonder Chevy retained the port-injection 6.0L V8 in the Silverado 2500 and 3500 instead of resorting to direct injection like it did in the 1500, not to mention the Suburban HD.
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Old 10-16-2018, 01:24 PM   #148 (permalink)
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I get the impression that turbo charging a smaller engine is no longer the fuel efficient way. Perhaps due to the lower compression ratio?
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So these turbo engine vehicles might get better fuel economy in stop and go driving, but worse in steady cruise?

I know Toyota gave the Gen III and IV Prius a larger displacement than the Gen I and II. Displacement must not be such a huge economy penalty as long as you can keep the engine near the BSFC sweet spot.
I don't believe everything this guy says. But he seems to have a good point. Traditionally turbocharged engines are made with lower CR's, use a lot more high load enrichment and retard the timing much more than N/A engines. The result is worse fuel economy. But if other forms of knock control are done properly, like cooled EGR, a turbocharged engine can theoretically get good fuel mileage.

[YouTube]
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Old 10-16-2018, 06:13 PM   #149 (permalink)
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Cooled EGR sounds like a reasonable approach to knock control too. Well, unless it's some random engine fitted with VVT and resorting to some "internal" non-cooled EGR to raise its temperature quicker, I see no reason for EGR to not be cooled anyway...
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Old 10-16-2018, 06:17 PM   #150 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
Cooled EGR sounds like a reasonable approach to knock control too. Well, unless it's some random engine fitted with VVT and resorting to some "internal" non-cooled EGR to raise its temperature quicker, I see no reason for EGR to not be cooled anyway...
That's covered in this video:


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