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Old 04-07-2018, 06:31 PM   #1 (permalink)
chefdave
Master EcoModder
 
Join Date: Nov 2013
Location: john o groats
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Question Baffled using 99 octane fuel

Hi hope this is right place for this post. Drive a peugeot 406 estate with 2.0 petrol 16v and auto box. Gearing is on a par with a diesel. 60mph = 2200rpm. Auto box is ecu controlled. Why is it when i use 99 octane fuel my engine runs smoother and auto box is fantastic compared to using 95 octane fuel. Mods done are front air dam; radiator grill blocked so all air has to pass through radiator; lengthen air intake by 6"; fitted an exhaust that is 1/4" bigger in diameter and all tyres 4psi above recommended. Cannot think of a logical reason to why it is smoother and mpg is up 5+%. Tail pipe had a lot of carbon on it so i think its running rich. Mpg is up from 35-37mpg to 40mpg. Coasting distance is up as well as power for climbing hills box changes up sooner on 99 octane. Engine temp is bang on thermostat opening temperture. Can anyone shed any light on why this is as engine is designed for 95 octane.

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