ScoobyDoo555

no (imho). economy is a factor too. Although my one mate with a 330 (bm) didn't seem to think so - I converted him to trying it.....

He reluctantly did so, and then found the virtues of higher octane fuel..... and put his foot down, thus negating the reason for changing!!

oh well

ALi-B

iTrader: (1)

IMHO The only benefit RON value should pose is increased resistance to knock; that is all the RON measurement is used for.

On my daily commute: I have not noticed any difference in any of my vehicles when I tried Vpower vs Shell 95RON. Be it differences in low or mid range torque, hesitency or any audible detonation.

I now use Tesco (Shell were diddling my driver point bonuses); and guess what, can't tell the difference either. I still average 24mpg to and from work. Not great MPG I know, but its mostly urban rush hour driving.

skoobidude

If it was the V8 version then the unit is the same as in the B7 RS4. Inside the petrol cap is a sticker stating it can run on both 95 or 98RON.
I tend to use VPower as I'm just used to it.

SRSport

Yes it was the V8

Jamz3k

I wonder how many people own rather than lease R8's. I think this may be a factor on what fuel is actually used in the vehicle.

bigredrob

i have had two p6b 3500 v8 rovers, one ran on 5 star, 101 ron, 10.1 compression, the other 4 star, 98/99 ron, 9,25 compression, new cars can adjust to the fuel they use, my fergie tractor will run on paraffin, turps, petrol , alcohol , creosote and white sprit,?? almost anything that will go bang, if its preheated, depends how much power you want I suppose

SRSport

This guy got out and was in work clothes with the company name Niels. On his car I noticed it said Neel so Im guessing it wasnt rented.

DoZZa

iTrader: (4)

I ran my TVR T350T on Super for a while, made no difference to performance from standard 95ron fuel.

My old Legacy GT-B hated standard unleaded but loved Optimax, with added octane booster it was like it was on steroids.

As has been said, each car will be different when it comes to fuel.

Personally for my car I dont think you can beat Tesco 99, or Momentum as its now known. And not for the price either, to me money is not an issue with filling up with fuel, the Tesco stuff performs the best for me out of all the Super unleaded I have tested.

You are what you eat, apparently!

bigredrob

yum yum rx8 unleaded, scooby texeco high octane.

Trout

iTrader: (1)

But here is the thing - knock resistance applies over the whole rev range. Certainly in a turbo car, peak torque is an area where a couple of degrees ignition advance will give great efficiency benefits. With higher RON you can increase the advance right across the map so giving greater efficiency at all levels.

ALi-B

iTrader: (1)

If only it was that simple.

You HAVE to advance the timing on a high RON fuel because it typically burns more slowly than fuel with lower RON value. Otherwise the piston is way past TDC and half way down the bore with the fuel still burning (that equates to less power). So it must be ignited earlier. Its not just it allows you to have more advance, its because it needs more ignition advance to burn correctly for it reach full combustion pressures just after TDC.

LPG is a prime example of this, you can run a converted car with the ignition advanced as far as you like as it is 106RON. BUT it gives little or no power increase and poor mpg - why? Lower calorific value, and slow burn speed, plus its difficult to ignite fully. More ignition advance does not equal more power; Ignite too soon and you lose power. The ideal world amount of advance is directly proportional to the speed of which the fuel burns. Faster burning fuel doesn't need as much ignition advance as a slower burning fuel, as if tuned correctly the full combustion pressure will occur at the exact same ideal point ATDC.

Knock or detonation is due to alot of things - combustion chamber design is one key often neglected when people call up the RON argument. Higher RON does help resist it obviously, but better control of combustion and point of ignition is at the compromise of a slower burn speed, and additives used are either oxygenates (oxygenates cause closed-loop controlled engines to run richer unless mapped to compensate, i.e. Tesco 99Ron) and/or lower the calorific value. If an engine is suffering knock or det, one has to look at the cause of it in the first place; is the ignition timing properly matched to the fuel? 95RON burns quicker, so doesn't need so much advance, this is NOT always detrimental to power so long as combustion is controlled and full combustion pressure is reached at the correct point ATDC. Controlled combustion is down to the engine's design, control system and its condition.

Ergo; Efficiency and power is down to completely burning all of the fuel injected and getting it to fully ignite and reach full combustion pressure at the correct point ATDC. RON is just a small chunk of the whole picture. If an engine can be optimised to do this on 95RON, it won't do any better on a higher RON fuel of the same calorific value.

I will concede there is no such thing as the perfect engine, and calorific value is the sticking point, as its often an unknown variable. Not helped that few people seem to care about how much bang there is in the fuel they stick in their car, they are just besotted with its branding or RON value.

Here's something via google which relates to the use of oxygenates and how it affects the amount of energy (calorific value) the fuel contains: http://www.epa.gov/OMSWWW/rfgecon.htm

Trout

iTrader: (1)

Again all useful stuff with a big BUT!

If what you are saying is completely true then why do amateur/professional/manufacturer mappers (and I have done a few rounds with an ECU)

a) want to run performance cars on higher RON fuel

b) go to very high RON levels for race fuel

if as you say a well optimised map/engine will be just as efficient at 95RON as it will be at any higher RON for the same calorific value? Why don't race cars simply use better quality fuel with a more predictable calorific value?

RON may only be a chunk of the whole picture and MON may be a more accurate measure of a fuels characteristics, but it does not move away from the fact that higher performing cars are typically mapped at highed ignition advance and use higher RON.

Having done a bit of mapping it is incredible how much difference even a quarter of a degree of advance can make to the overall power output.

ALi-B

iTrader: (1)

a) Personal choice; a higher RON is a easy fix to a limitation posed by a given engine; Be it glowing carbon deposits, gas-flow/swirl issues, too much compression or simply running too much boost. One has to weigh up the gain; if that gain is 5bhp (a lawn mower's worth), even if it across the whole rev band, its a drop in the ocean in a 300bhp+ car. If its 50bhp, then its worth it. Additionally does anyone map their car for fuel economy?

b)Race engines are not efficient; many have fuel still burning as it exits the exhaust ports. When exhaust valves are glowing red hot and enduring such high cylinder pressures, one has a choice of either a fuel more less prone to auto-ignition, doing physical changes to the engine, dumping extra fuel to quench it, or using water/meths injection, or a combination any variable that gets the desired results within budget or the regs of that racing class, not just the RON alone.

That the crux of the issue: Higher RON doesn't not have the same calorific values. If it did, it would be an easy comparison.

Once again, I repeat: That extra power gain from advancing ignition maybe because the fuel wasn't fully igniting at the right time in the first place, and wasting it by pushing a piston that is already half way down the bore, due to using a slower burning fuel. If 0.25degrees achieves this ideal, then you've done your job.

Anyhoo back to factory cars running standard tuning. Is the extra cost of the fuel worth, lets say, 5bhp or 1mpg gain?

For a daily commute in 20-50mph traffic; I say no its not and a waste of money

I may consider it for track use, but not if it was £3 a litre BP 102RON, unless it magically made it give an extra 100bhp.

So going back to the R8 for everyday use (which I fancy getting once the residuals drop), if the guy sees no advantage in it, who are we to deride him for it?

I won't even start on my stagnentation theory of the less popular fuels left sitting in forecourt tanks .

Matteeboy

I only ever used normal petrol in the R32 Golf - it was fine.

I'm convinced that the benefits of "premium" fuels are very rarely quantified. I reckon there's some benefit for highly tuned turbo'd petrols but that's about it.

The higher the octane rating, the quicker fuel degrades. Not that many people buy premium fuels so it's often likely that your overpriced stuff will actually have less octane rating than normal stuff. Despite being ripped off for fuel in the UK, we are quite lucky in that ours is actually decent quality. The stuff in the States (for example) is terrible.

DisoDisp

iTrader: (1)

Lots of specualtion on here.

The "RON" value, or Octane rating, is, as stated earlier just a numerical value defining its resistance of auto igniting, or "knock resistance", if you will.

How much the octane rating matters in normally aspirated engines is marginal, it is much more important in forced induction engines, as it allows you to significantly alter ignition advance timing as well as the amount of boost you can run with your engine.

Which is why forced induction cars will benefit from running V-power more than Naturally Aspirated cars.

However, I know that V-Power has a lot of different hexane based compounds which "clean" your engine, as well as some polyetheres iirc, which supposedly help create a "film" in your engine, reducing friction between pistons and cylinder walls etc, thus increasing your MPG.

How much of that is marketing hype, and how much is factual, is up to everyone to decide themselves, I do know that Shell buys their Petrol straight from our refinery and add their own chemicals to it on the way to the pumps.

Don't know how it is in the UK, does shell buy its refined petrol from BP and just add its own concotions before selling it as its "own" product?

SRSport

Not in practice for me.

https://www.scoobynet.com/scoobynet-...save-test.html

tony de wonderful

If we cared about thermodynamic efficiency we'd run diesel.

I want boost Baby!

ALi-B

iTrader: (1)

That link was used to refer to the energy contained in fuel (BTU per gallon); for more boost, you need more energy

Matteeboy

So if someone doesn't think it's worth using "super" fuel, they don't care about their car?

What an absolute loads of bo77ocks.

zip106

I don't know, Mattee.

I know of a lot of people with leased or company cars (one actually being an R8) and they all put normal fuel in them when 'super' stuff would/should be better.

Just like they don't look after them (i.e clean them) as you or I would if it was our own car.

I guess the thinking is that the car will be going back at the end of the lease so they're not really bothered what happens to it in the mean time!

Matteeboy

Zip - yep, leased cars are often abused but that doesn't mean those that use "normal" fuel are cut from the same cloth.

Jamz3k

no one said they are.

Trout

iTrader: (1)

My comment for option a) was referring to manufacturer cars. There are manufacturers from Subaru to Suzuki, through BMW to Porsche that recommend running cars on SUL. Why is that if it is so inefficient? These are no manufacturers renowned for making poor engines! Indeed, quite the opposite.

So I would argue it is not personal choice it is manufacturer choice.

Your argument is well made but does not seem to be supported by cars in the market.

graeme jones

If the filler cap specifies a 98/99 ron then thats what i would use for the sake of an extra 7p a litre.
I got caught out and put £20 normal petrol in my WRX 03 and it run very poorly until I filled up with V-power.

lozgti1

Are those £15 from Halfords bottle fuel additives any good as a matter of interest??

Just trying one at the moment.........

Aztec Performance Ltd

iTrader: (234)

Waste of time.

Aztec Performance Ltd

iTrader: (234)

The difference between putting 95 fuel into a R8 designed to run 98+ will be more than just a handful of bhp.

I've not seen a R8 being driven quick anywhere though

SRSport

I take it you don't live around Bradford then? The only place I see supercars driven as though they were stolen.

Mr Wagon

You guys make me laugh, the cost of filling a tank on a Scoob with normal compared to super is only £2. If the Audi has a bigger tank and the differance is say like £5 then that is nothing compared to running costs for that sort of car such as tyres, service etc.

At least with an Audi you do have a proper computer in the car that will tell you how many MPG you did.

scooby-tc

iTrader: (2)

i have the same engine in my car (well with 2 turbos bolted on) and i would never comtemplate using anything other than super unleaded anything else is madness even though the Audi ECUs are highly advanced units