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Old 07-30-2008, 01:24 AM   #1 (permalink)
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turbo engines: getting to speed

Anyone know what's the most efficient for why to accelerate with a boosted engine? I've read some claims that for n/a cars, it's best to go to 75% or even WOT at low rpm (shifting between 2000-2500 rpm) to get up to speed. Does anyone have links to actual tests that verify that? Or is gradual accel more efficient? What about with a turbo?

My car:

I have an '08 subaru spec b which has si-drive, which complicates things. In I mode, it limits boost to about 9psi, fwir and limits the throttle position to 40% (that's input, i believe, not the actual throttle plate). I think its ecu uses a torque target - it might go WOT with low boost, then ramp up the boost, rather than use a constant boost target across throttle positions and use the throttle to control engine torque (which would be less efficient and cause a lot of intake recirc thru the compressor). I need to do some research on that.

I'm not sure using I mode and flooring it (shifting at 2500rpm) is better than doing the same in S mode which will give 100% open throttle and maybe slightly more boost. Of course, you loose some turbine speed between shifts, so holding gears longer may be more efficient also.

Basically, I'm trying to make my city driving more efficient.

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