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Guest Message by DevFuse
 

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driving tip?


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11 replies to this topic

#1 Uberoo

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Posted 18 March 2013 - 04:26 AM

I found a BSFC chart for a EJ22 and from my understanding you will get the best MPG possible between 1800 and 3500 RPM at WOT.At anything less than WOT the engine has to work harder fighting the vacuum the engine produces against the closed throttle plate.By comparison a diesel which has no throttle valve will use the least amount of fuel at its torque peak and use more fuel as RPM's increase.

 

So my question is how exactly are you supposed to drive at 1800-3500 RPM at WOT in city traffic?

 

Just for reference the BSFC can be found here:

http://www.rs25.com/...s-shifting.html



#2 1 Lucky Texan

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Posted 18 March 2013 - 08:32 AM

they speak to that in the thread. Of course you can't drive our cars, or most cars, at wot at road speeds because you will accelerate.

 

 

if no one cared about acceleration, you could use a 10-15 hp engine at wot to drive at a constant 55mph - and get great gas mileage.


Edited by 1 Lucky Texan, 18 March 2013 - 08:34 AM.


#3 spazomatic

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Posted 18 March 2013 - 09:33 AM

You could do it like sammy hagar....one foot on the brake, and one on the gas, yeah!
Jk. I try to explain to people how gasoline burners are most efficient at WOT, and they give me blank stares like im crazy.

#4 CNY_Dave

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Posted 18 March 2013 - 11:35 AM

I remember a research car built with no throttle, it had an insane constantly variable transmission (connected to the gas pedal) that could gear the car up enough to produce any desired slow speed.



#5 efseiler

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Posted 18 March 2013 - 06:27 PM

That sounds like a bunch of baloney...the computer adjusts the mixture on the fly...it's smarter than you think.

 

 

That's why there's two oxygen sensors and an air flow sensor.

 

 

 

I usually get 25-27 mpg highway no matter what I do (dry conditions, touring tires) with a '98 OBW.

 

 

 

 

--Damien



#6 Numbchux

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Posted 18 March 2013 - 07:43 PM

BAAAAAAAHAHAHAHAHAHA




That's awesome. I needed a laugh.


By that logic, shift to 5th immediately, and stand on the throttle....give it a try for a tank and see what kind of mileage you get.

Edited by Numbchux, 18 March 2013 - 07:45 PM.


#7 nipper

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Posted 18 March 2013 - 08:09 PM

Keep in mind that is all in a test lab with no wind drag on an engine Dyno. There is some truth to this. If you open the throttle wide and climb in the gears as quickly as possible yes you will get the best MPG. However screaming around in 2nd gear because the speed limit is 30 mph will hurt your mpg and engine life.

 

Lab tests are great, but the real world has 100's of vairiables and everything on a car is compromise to work within these variables.



#8 nipper

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Posted 18 March 2013 - 08:10 PM

I remember a research car built with no throttle, it had an insane constantly variable transmission (connected to the gas pedal) that could gear the car up enough to produce any desired slow speed.

I have something like this, its called a CVT. The transmission does almost all the work, engine RPM rarely raises over 3800 RPM on WOT.



#9 CNY_Dave

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Posted 19 March 2013 - 08:01 AM

Any engine works most efficiently at about 80% of full load.

 

Any throttled engine works more efficiently at wider throttle openings due to losses in 'pulling vacuum'.

 

These are fundamentals that every IC engine engineer and scientist understand.

 

Matching the engine's efficiency (turning fuel into power) and the vehicle's efficiency (MPG, what you care about) is the art to that science.


Edited by CNY_Dave, 19 March 2013 - 08:02 AM.


#10 mikaleda

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Posted 19 March 2013 - 09:46 AM

1800-3500 rpm at WOT? sounds like a great way to wear your car out in a hurry.



#11 efseiler

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Posted 19 March 2013 - 12:45 PM

I'm glad you laugh cuz the admission ticket is non-refundable.  :grin:



#12 Fairtax4me

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Posted 20 March 2013 - 09:58 AM

Engine efficiency does not equal fuel economy. And it's impossible for us all to drive around at 2500 rpm with the throttle wide open all the time. One day when we all fly to work maybe that will be possible, but for now you'll get your best fuel economy between 2000 and 3000 rpm at 15-20% throttle. Even though that is not the most efficient operating point (as far as power output and heat generaton are concerned) for the engine.




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