[Shop-talk] Premium for Turbos

[John Miller]

On 6/8/2010 11:20 AM, Nolan wrote:
> Generally speaking, because of the turbo boost the effects of pinging
> are far more dramatic. You'll hole a piston far quicker in a turbo
> engine than a non-turbo engine.
>
> That said, most have a knock sensor that knocks back the ignition
> timing, or kills turbo boost. Which makes the car as fun to drive as
> watching mold grow on a shower wall. Defeats the turbo. Some are soft,
> some are very abrupt. It depends entirely on the car.

With some vehicles (normally-aspirated as well as blower) you will hit a 
point in the engine-protection strategy where the resultant reduction in 
spark timing, etc. ends up costing you big-time in driveability or fuel 
economy.

My E39 M5 loves 100AKI and was quite happy on Euro-market 98RON back on 
the Euro Delivery trip, on the factory tune there was a noticeable drop 
in throttle response just going from the 92AKI that used to be 
California crap-premium to the adulterated 91AKI crap-premium we get now 
(or a bad tank of 92, or the occasional tank of 89.)  It's got a 
Powerchips flash in it now that is marginally better.

John.