Fuelling my GT

[jdjd]

Listen, I am telling you all now the 99ron fuel from Shell or Tesco, DOES make a big difference to my GTI's performence, The pickup in the gears is alot quicker pulls though the range faster. 
 FACT,

[ub7rm]

If using 98 ron was beneficial Vw would recommend you use it,if its more economical and you get higher performance then why don`t they tell you to use it?,its only more economical if the extra miles per gallon you get out weighs the price difference.The fact they say use 95 says it all.

A lot of people weren't very happy that they 'had' to run their mk5's on the good stuff.  Especially given that its not widely available once you get out of cities. Rural GTI owners felt slightly cheated that their cars couldn't make the 'stated' power / economy etc. VW addressed this and got more power and better economy in comparison to the mkv out of the cheaper petrol.  Everyones happy.  Doesn't mean you cant get more performance / economy by using higher ron petrol. 

[mac7]

Doesn't mean you cant get more performance / economy by using higher ron petrol. 

Agreed. Any car with ECU-controlled variable ignition timing, provided the map allows sufficient advance, will see gains in power and economy when using fuel with a higher octane rating.

[rjwojcik]

Chaps.  The Revo site states that "three performance modes, supported by Revo Select and Select Plus switches" for 95ron, 98ron and 100ron.  If the ECU is capable of detecting and dealing with different fuel grades why do they offer the different maps?

[mac7]

Chaps.  The Revo site states that "three performance modes, supported by Revo Select and Select Plus switches" for 95ron, 98ron and 100ron.  If the ECU is capable of detecting and dealing with different fuel grades why do they offer the different maps?

Agreed. Any car with ECU-controlled variable ignition timing, provided the map allows sufficient advance, will see gains in power and economy when using fuel with a higher octane rating.

I am not an expert in ECU mapping, however I do know the ECU doesn't detect the fuel RON, it reacts to the consequences of using a particular octane rating within the limits of the ignition, fuelling and inlet pressure maps. Remember Revo are increasing boost pressure as well as fuelling and ignition advance, etc, so maybe they can take full advantage of the increased resistance to detonation of each higher RON fuel without being concerned that the owner might put a low octane fuel in.

But you'd have to talk to someone who plays with ECU's like Revo to get a proper answer.

[ub7rm]

As well as that, when VW sell the GTI it has a lot of compromises built into it to allow for poor quality fuel which may be availble in certain countries, the extremes of weather from one coutry to another, making it as reliable as possible given that some people maybe wont service it right etc etc.  If you take away a lot of these uncertainties, good fuel, temperate climate, good servicing regime you can start to take away the compromises from the map that restricts power.  Hence Revo.

Of course they do more than just cut out compromises but its much easier to write a focussed map when you assume your petrol quality is fixed and not floating from 95 to 100...