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Old 05-06-2020, 10:37 PM   #66 (permalink)
JulianEdgar
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Quote:
Originally Posted by Yippeekyaa View Post
Your welcome Julian, was very disappointing that the throttle stop method will not work on a Prius. My moms Ford has an 8 speed transmission.
There is possibly a way of doing this with electronic throttle.
  • You will need two people, flat and straight road, decent speed update OBD data.
  • Drive car at constant speed eg 100 km/h. You will probably be able to do that more accurately than the cruise control, but see which is better.
  • Passenger reads actual throttle blade position (or total engine load if such a figure is available).
  • Figure needs to stabilise eg less than 1 per cent variation as you hold speed constant.
  • Repeat test and make sure figures are very close.
  • Open all windows. Go back over same stretch of road with all windows open.
  • Maintain same speed.
  • Read what actual throttle blade position (or total load number) now is.

If the blade opening or load number has distinctly increased, then you have a base reading for what causes a major (eg typically 12 per cent) change in drag.

If that is the case, you have a go / no go indicator for aero mods - so long as the change with the aero modification is above the variation in the readings at a constant speed.

However, do not apply any maths to attempt to work out percentage changes - too hard when throttle blade position / load number is probably not linear with power (or torque).

(And I wouldn't do it with the Prius yet, in case electric power is also changing.)

Let us know how you go!

Last edited by JulianEdgar; 05-06-2020 at 10:48 PM..
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