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Old 08-07-2006, 12:42 AM   #1
G.Subramaniam
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Default Question on NA vs Turbo fuel efficiency

Am I correct in assuming that since Turbo cars need a rich Fuel mix, they need to run AFR around 11, vs NA cars that can run around 14
This should make NA cars much more fuel efficient
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Old 08-07-2006, 12:43 AM   #2
reddevil
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goes 12.387 @ 116.5

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More power = more fuel. 600 hp NA monsters eat more fuel than 400 turbo monsters.
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Old 08-07-2006, 08:31 AM   #3
Master2192
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98 2.5 RS
04 WRX

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Quote:
Originally Posted by G.Subramaniam
Am I correct in assuming that since Turbo cars need a rich Fuel mix, they need to run AFR around 11, vs NA cars that can run around 14
This should make NA cars much more fuel efficient
First, turbo cars can run 14.7 (stoic) just as much as a N/A car. Its not the AFRs that make them inefficient, its that they have a exhaust restriction (turbo) and run a low compression ratio.

An all out N/A car will run around a 12-13 AFR anyway, thats not much better than a Turbo car either. But that is full throttle, which you shouldn't be doing if you are worrying about fuel efficiency.

What Red Devil said was right though.
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Old 08-07-2006, 04:28 PM   #4
G.Subramaniam
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Default

Does the WRX / GT give less mileage than the RS, and by how much

Does increasing compression increase mileage, and by how much
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Old 08-07-2006, 06:00 PM   #5
Master2192
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04 WRX

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Quote:
Originally Posted by G.Subramaniam
Does the WRX / GT give less mileage than the RS, and by how much

Does increasing compression increase mileage, and by how much
1. Yes, especially in the city. But on the highway the 04 WRX gets only 1 mpg less than my 98 RS. My RS cruises at about 500rpms higher than the WRX and still gets better mileage.

2. Increasing compression ratio raises the Engines Thermal Efficiency. IIRC it continues to increase until a 19:1 compression ratio. There was a graph inside one of the E85 threads from the EPA that showed this. Raising thermal efficiency means more of fuel gets turned to motion instead of just heat.

The RS should always get better fuel mileage than the turbo models, mostly because of compression ratio.
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