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Old 02-13-2013, 02:54 AM   #42 (permalink)
renault_megane_dci
Master EcoModder
 
Join Date: Feb 2009
Location: France - Paris
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la_voiture_de_courses - '03 Renault Megane Estate
OldContinents
90 day: 44.34 mpg (US)

xiao lan - '01 Audi A2
90 day: 38.88 mpg (US)

Brit iron - '92 Mini Mini
90 day: 45.5 mpg (US)

Prius - '09 Toyota PRIUS Lounge
90 day: 47.37 mpg (US)

Beemer - '06 BMW F800 ST
90 day: 53.06 mpg (US)
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Quote:
Originally Posted by nemesis View Post
There are lots of variables that you can change and retarding the intake cam does sound like it would decrease dynamic compression/horsepower/torque which should decrease pumping losses in theory and less power would requier less fuel, but altered ignition maping along with fuel mapping with vvt timing should make this combo work pretty good. Vvt would retard intake cam while you're cruising and when you need more power it would advance the intake cam to gain more power. It would be tricky to get igntion/vvt/fuel timing to work all at the same time on top of other variables like map sensor, air intake temp, engine coolant temp, oxygen sensor, bap sensor, tps sensor.
VVT as it is done on car engines is very challenging to retrofit on a bike engine for a DIYer.

We are not dealing with car engines where the high torque at low RPM is mandatory to make the vehicle move, we are detuning overly powerful engines to make them reach a more acceptable FE to capacity ratio.

If a 500 bike was doing 195 km/h and return 45 mpg, I don't mind it is modified to hit only 130 km/h but return 80 mpg.

But I don't know how to extrapolate either MPG improvement or power loss induced by Atkinsoning of those engines.
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