VR6 - RON95 or RON98 ? - what do you guys use?

[Mawrick 0]

I'v always thought that RON98 will be the better choice for these engines - even if it states 95 in the "petrol filling hatch".

(reason being that it's a "better quality" fuel, and IIRC the service book from my old Passat 1.8 engine stated that the car would run on both 95 and 98 (obviously) - but would perform best with 98.)

 

 

Just wondering what you lot are running on your VR6's.

 

 

Sometimes I obviously will have 95 on the tank as some petrol stations don't have 98....

[JonnyHull 0]

Whenever possible I use the better fuel, 97,98 or 99 if available. To be perfectly honest I never really feel the difference with normal driving between the higher RON fuels and normal 95. Its just peace of mind really that you are putting in better fuel. I do think I get slightly better MPG with the higher RON fuels and I know in theory I should be getting slightly more power but for my standard vr it definately isn't very noticeable to me.

 

There is also the addatives that go into the more expensive fuels that are another benefit.

 

Although I don't use it very often, my vr runs perfectly on 95. But I would say stick to the good stuff if possible. Best to treat the car to the good stuff if only to make you feel better. :)

 

Anyone else have similar experiences?

Edited February 24, 2011 by JonnyHull

[robrado974 1]

98 all the time me mate had the vr before me and he didnt put anythin else in the tank

[Mawrick 0]

yea, normally 98RON for me as my closest petrol station luckily have it - but sometimes one doesn't have the option...lol....:)

[aide 0]

yep 98 all th way, would go higher if i knew who sold any locally.

[Toad 0]

Currently 95 octane with wurth octane booster. Seem to have had better fuel economy since trying it.

[Ben-B 0]

I'll be running on Ronnie 99 only (Shell V Power/Tesco 99)

 

I only ever ran my derv corsa on V Power Diesel, and it was worth the few pence a litre extra.

 

From what I understand, and forgive me if I'm wrong... but with petrol though, there will only be a power benefit if the ECU can adjust timings to take advantage of the higher RON. But with diesel, there is a power regardless, as it is a measure of how fast the fuel burns (petrol's is a measure of how resistant to detonation I think)

 

The additives in both super fuels clean the fuel lines, injectors and engine, so that can increase engine efficiency... that'd be good enough for me, an increase in power is a bonus

[RW1 0]

VR6 ECU adjusts automatically for fuelling with 95 - 99 RON. Difference in power thoughout the rev range. Generally about a 3 - 4% power loss between 98RON and 95RON at peak revs (5,800rpm) and proportionally below that.

 

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[Ben-B 0]

VR6 ECU adjusts automatically for fuelling with 95 - 99 RON. Difference in power thoughout the rev range. Generally about a 3 - 4% power loss between 98RON and 95RON at peak revs (5,800rpm) and proportionally below that.

 

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That's a good 6-8 bhp nearly on a standard VR then... I didn't realise it'd be that much

[daleyboy 0]

i would have thought any power figures VW give would be with 98 ron as it says on mine inside the filler cap to use 98 ron. So maybe a 6-8% LOSS if you use 95........... :shrug:

[RW1 0]

i would have thought any power figures VW give would be with 98 ron as it says on mine inside the filler cap to use 98 ron. So maybe a 6-8% LOSS if you use 95........... :shrug:

 

Correct :)

Only give it the best.

 

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[Toad 0]

VR6 ECU adjusts automatically for fuelling with 95 - 99 RON. Difference in power thoughout the rev range. Generally about a 3 - 4% power loss between 98RON and 95RON at peak revs (5,800rpm) and proportionally below that.

 

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How does it work out what fuel it has in it?

[mrbeige 0]

VR6 ECU adjusts automatically for fuelling with 95 - 99 RON. Difference in power thoughout the rev range. Generally about a 3 - 4% power loss between 98RON and 95RON at peak revs (5,800rpm) and proportionally below that.

 

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How does it work out what fuel it has in it?

It will adapt based on closed loop feedback from the lambda, Tom, however, the power increase wont necessarily be from the adaption, more likely the higher octane.

[Serial 0]

Does it also use the knock sensors to keep the ignition as advanced as possible without any knocking occurring? I.e when you change fuel types it'll either detect it knocking wildly and retard the timing (if you're going from 99->95), or if you've just filled up with 99 it'll be able to advance it more before the knock sensors tell it to stop.

[RW1 0]

It uses two knock sensors as well as the lambda probe. Knock sensors for the ignition timing, Lambda for the fuelling.

 

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[Jim Bowen 1]

95ron, always have and find i get better MPG with it.

 

also car is coming up to 200,000miles so can't of done it any harm

[big ben 10]

i just use tesco momentum 99RON, find i getter better mpg than v power for some reason...

 

super unleaded is a lot more improtant on forced induction as well, my mates G60 ran shit on 95RON when he uae to use it sometimes

[Kevin Bacon 5]

Does it also use the knock sensors to keep the ignition as advanced as possible without any knocking occurring? I.e when you change fuel types it'll either detect it knocking wildly and retard the timing (if you're going from 99->95), or if you've just filled up with 99 it'll be able to advance it more before the knock sensors tell it to stop.

 

Sort of! The ECU doesn't know or care about what fuel you've put in the tank. It runs the same ignition timing for all fuels, but if it hears knock, it will retard. It's as simple as that :D And simple is exactly what you need when selling a car to the public.

 

They have to account for the idiots who try and pull the car up a 1:3 gradient in 5th gear from 15mph, the people who like to bounce their engines off the limiter all the time, caravan towers and also for the home tinkerers, etc etc. You get the drift!

 

The ECU won't advance more than the factory preset timing. I'm not aware of any car maker who will allow their ECUs to constantly flit between peak advance and max retard permanently. It's too risky.

 

The performance benefit, if there is one to be had, comes from the fact the ECU simply isn't retarding the ignition. Obviously 98 or 99 RON will resist knock better than 95, so the chances of knock are significantly reduced. So it's not actually a gain as such, you're just not losing anything :wink:

 

It's a bit out of scope for this thread really, but the ECU contains preset ignition advance tables, which VW will have mapped to an MBT strategy (Mean Best Torque) on 98 RON fuel. 'MBT' means they find the peak torque on the dyno for a given rpm and load, and then add timing until there is no increase in power or torque, then back it off a pre-determined amount, thereby giving the engine a safe 'allowance' to work in.

 

Any race engine builder will tell you that engines make peak torque just before detonation occurs, aka 'edge of knock'. Some race cars don't run knock sensors because the rumble strips can send false 'knock event' signals to the ECU, which cuts the power mid bend. Not what they want. Knock sensors are just microphones at the end of the day and are easily susceptible to erroneous noises.

That's why BMW moved away from them and onto 'ion current detection' through the spark plugs instead, but that's a whole different thread, LOL!

 

It's that 'allowance' in the timing which rechippers exploit to make the engine feel livlier, by moving the base timing closer to the edge of knock, permanently.

 

That's all well and good if you have a guaranteed supply of 99 RON, but if you don't? Case in point - Mid 90s JDM import Imprezas mapped for their 100 RON fuel. Most of them blew up over here. Prodrive then got involved and things improved.

 

As standard, the VR6 has VERY tame timing in the lower rpms to make it smoother and less aggressive off the clutch. Easy to drive in other words, for your Aunt Mable. Chippers tend to whack these areas right up to make it feel more aggressive, but you don't actually gain a lot in power. It just feels as if it has. The only way to gain meaningful power is to burn more fuel and air.

[SamG40 0]

So what would you use in a standard VR then Mr Wire?

 

I myself use a mix. When using the car for pootling to work etc when I know I'll be stuck in traffic I'll put 95 in. If I'm going on a decent journey in it and know I'll be going on some decent roads it will get the good stuff.