Buying a used Golf R: mods and fuel

[55378008]

I intend to buy a Golf R mk 7 or 7.5

I would like a stage 1 or stage 2 tune (eventually) and I am weighing up whether to buy a stock car and modify it myself, or buy an already modified one. I know the latter is more risky. Where I like (Sweden) some examples from reputable car dealerships have full documentation of the mods done, which I tend to think I can trust.

At Stage 2 onwards some cars have a RON 98 "only" rating, which is fine. I know that the relative merits/risks of 95 and 98 on horsepower and engine wear have been debated many times on forums, including this one. My question is specifically about how mods relate to these.

Specifically, what is it about Stage 2 or 3 tunes that would take a Golf R from 95 or 98 to 98 only? Is it that the more precise combustion timing of 98 becomes more important to produce power but 95 could suffice? Or is it that people at Stage 2 or 3 add some kind of fuel injectors that can only tolerate 98? I have not found specific info on what it is that higher tunes involve that means only 98 should be used (other than that people want more power).

As you can sense probably, I'm only starting out here, so please be gentle. I'm trying to understand the influence of mods on what fuel is possible to use. I do already understand that/why 98 is generally superior to 95. What I'm less familiar with is how modifications impact why a golf could become a 98-only golf after Stage 2-3 mods.

Thanks in advance!

[aka_kerrly]

I'd suggest that firstly you ignore all the stage 1 stage 2 stage 3 bull st and actually make a list of what modifications you want or perhaps a power target and then speak to a VW specialist not a generic " I'm a mapper/ let's stage 4.9 with added over fueling/retarded timing type"

[Scrump]

Others with more knowledge will be along.

Higher octane petrol is more resistant to pre detonation. My understanding is that when a car , especially a boosted one, is remapped or tuned the boost and ignition timing can be adjusted to optimise the power at the levels enabled by the higher octane fuel.

If the car is able to run on standard and high octane fuel then the map is likely to be more conservative to be more tolerant of the low octane fuel

[tomsugden]

When I had my S5 remapped by APR, they had a stage 1 95, and a stage 1 98 available. The first could be run using 95 or 98 ron fuel, the second would cause damage if pushing on and using 95 ron.

[rev-erend]

Some tuners offer a multi position map adjuster. So you can choose a different map if you find yourself in a place that does not have higher octane fuel.

Think Revotec do one.

[anonymous-user]

VW recommend 98 in standard cars, yet alone remapped cars.