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My previous car, an RCZ ran better on Shell Ultra so I tried it in my GTI for 3 fills, all I noticed was that the tail pipe was always sooted up, gone back to normal Shell, car is running better and tail pipe isn't sooted up anymore!
 

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Do NOT waste your money on those fancy fuels! It makes no difference and can actually make older cars run worse!Ill explain why the best I can....

Fuels are given an octane rating. This is its RON. We'll use petrol for this example as that's what was used by bradshaw. You have standard unleaded which is 95 RON, super unleaded which is 97 RON and Im sure the nitro plus stuff is 99RON. Now the higher the octane rating of a fuel, the quicker it can burn so people think great it burns quicker so it can male my engine go faster. This is WRONG. Your car engine is designed to run on standard unleaded which means its timed up to inject that fuel (say 8ºBTDC) at the precise moment it needs to, achieving maximum performance from the engine. Now say you have filled up with Super unleaded and you start your car. Yes it will run fine but the fuel thats now getting injected burns faster, meaning it has combusted before it should have, meaning the car has actually got poorer performance. Don't get me wrong, those high octane fuels ain't a total con. They are actually designed for the higher performance cars such as your BMW M3s all the way up to the lamborghini's.Some tuners after remapping their ecu use super unleaded as their engine is now designed to run on a faster burning fuel.
If I have missed something out then please feel free to add as it's a while since I learnt all of this and never really put much thought into it since
 

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@Duffy.

Yes it will run fine but the fuel thatsnowgetting injected burns faster, meaning it has combusted before it should have, meaning the car has actually got poorer performance.

The octane rating of a fuel has nothing to do with how 'fast' it burns. This is more to do with the volatility of the fuel which differs between seasonal blends to account for environmental temperature changes. The higher octane rating means the fuel has a higher resistance to auto ignition (when the air/fuel mixture explodes before the spark from the plug under high compression) or 'pinking'.


They are actually designed for the higher performance cars such as your BMW M3s all the way up to the lamborghini's.Some tuners after remapping their ecu use super unleaded as their engine is now designed to run on a<strike> faster burning </strike>higher octane fuel.


This is true, some cars do have an ECU thataccommodate higher octane fuels to alter engine conditions to give higher compression making use of the fuel's properties to not auto ignite.

But back to the point, I am unsure if the 208 gti has the ability to benefit from the more expensive fuels. I certainly can't tell the difference in my gti?
 

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The gain(using 97,98,99,100ron) is not noticable but if your reving high such as stage 2 then you dont want knock sensor pulling back timing else you may as well be stage 1. Using higher ron fuels is safer for tunes but performance wise, sitting in the driving seat you wont notice any power gain as you cant get 10% more power from using 99ron for example compared to 95ron. As a guy once said, at a refinery all ron fuels come from the same tank then blended by those who buy them using additives. My car runs fine on 95 but I prefer to use 99 due to tune, its safer. Its actually mapped for 98ron. I wouldnt expect a turbo petrol engine running on 99ron to make more 1-2% power than over a 95ron but its not about power, its about how safe(reliable) your tune is.

Pinkwafer said:
@Duffy.

Yes it will run fine but the fuel thatsnowgetting injected burns faster, meaning it has combusted before it should have, meaning the car has actually got poorer performance.

The octane rating of a fuel has nothing to do with how 'fast' it burns. This is more to do with the volatility of the fuel which differs between seasonal blends to account for environmental temperature changes. The higher octane rating means the fuel has a higher resistance to auto ignition (when the air/fuel mixture explodes before the spark from the plug under high compression) or 'pinking'.


They are actually designed for the higher performance cars such as your BMW M3s all the way up to the lamborghini's.Some tuners after remapping their ecu use super unleaded as their engine is now designed to run on a<strike> faster burning </strike>higher octane fuel.


This is true, some cars do have an ECU thataccommodate higher octane fuels to alter engine conditions to give higher compression making use of the fuel's properties to not auto ignite.

But back to the point, I am unsure if the 208 gti has the ability to benefit from the more expensive fuels. I certainly can't tell the difference in my gti?
 

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I filled today in germany on Aral Petrol station unleaded 102ron:)
 

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I have always used Super unleaded shell Optimax then nitro and now nitro+ I perfer it for the chemical structure and cleaning properties over the regular stuff.

Your exhaust getting all Sooty is more from Oil being burnt in the cylinder as well more than the exhaust gases. The oil comes from your blowby. If your a Euro 5 engine typically you will burn more of this than a Euro 6 Engine.

Some GCSE science for you here:

Fuels burn when they react with oxygen in the air. If there is plenty of air, complete combustion happens. Coal is mostly carbon. During complete combustion, carbon is oxidised to carbon dioxide.

If there is insufficient air for complete combustion, incomplete combustion (also called partial combustion) happens. Hydrogen is stilloxidisedto water, but carbon monoxide forms instead of carbon dioxide.Carbon monoxideis a toxic gas, so adequate ventilation is important when burning fuels.Solid particles (particulates) are also released. These contain carbon and are seen as soot or smoke.
 

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Schneider said:
I have always used Super unleaded shell Optimax then nitro and now nitro+ I perfer it for the chemical structure and cleaning properties over the regular stuff.

How do the perceived extra cleaning properties of the 97RON fuels help the GTI. It has a direct injection engine... the fuel is injected directly into the combustion chamber so it has no ability to clean anything.

If you want high octane then you could use E85 - that is around 105RON
 

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I'm a bit of a Shell fan boy, I like their loyalty scheme with money off vouchers etc.

Will let you know how I get on with the different fuels when mine arrives tomorrow.

Cheers

Mike
 

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Errrrmm Valves. The inlet valve opens and that how direct injection fuel gets into the combustion chamber, you cant just squirt it in, you then dont want pre det from knocking, the fuel then passes through the exhuast valve and through the exhuast and cat. You also get scavenging(direct/ loop /cross, uniflow and reverse)

I wouldnt dream of running a tuned car on 95ron, det would not be far away on anything more than stage 1

Pug208GTI said:
Schneider said:
I have always used Super unleaded shell Optimax then nitro and now nitro+ I perfer it for the chemical structure and cleaning properties over the regular stuff.

How do the perceived extra cleaning properties of the 97RON fuels help the GTI. It has a direct injection engine... the fuel is injected directly into the combustion chamber so it has no ability to clean anything.

If you want high octane then you could use E85 - that is around 105RON
 

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Direct injection sprays the fuel directly into the combustion chamber. So it can't do any cleaning of the inlet valves etc like on a port injected or carburettored car.
 

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Another common mis conception of how an engine works. I did word poorly but valves still let 90% of whats needed in and out. Most importantly the oxygen in so a burn can happen but with direct injection please read on to see the problems.

Direct injection is simply a term used if the air and petrol is not mixed before going into cylinders. The main point of direct injection is to get a fine particle/spray of fuel for efficiency and emissions and correct amount in each cylinder so lean cylinders have less chance as engines are only 30-40% efficient due to the nature of petrol not being a great fuel. The older method though worse for emmisions was actually better as fuel is corrosive and would clean an inlet valve stem to a point when going passed it, with direct injection thats not possible and carbon build up is worse on the stems due to pcv.

Scavenging is happening at any point a valve is open. positive crank ventaltion(pcv) puts blow by back into intake, through turbo and into engine via the inlet valve which doesnt solve the problem of carbon build up and thus valve stick. The more knock you have the more unburnt fuel/air youll have which inturn through blowby(pcv) will pass the inlet valve for next burn.

Its another great debate that most owners need not bother with as they dont tune a car but post most the information that others can read.























Edited by: Comkotes
 

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I suppose Pug208gti This link will demonstrate why a higher ron fuel creates more power, this link does mention knock and advance timing which may require a few more links to understand what they do and why ,but he does explain and demonstrate the effects of running high and low octane levels pretty well on the link http://www.youtube.com/watch?v=gqvhaPLuTPI

Members should note you probably never feel a gain that is less than 10% when driving hence why a 3-4% increase in power using high ron fuels is not noticable, they are safer and it is mentioned for tuning. when youre tuning - reliability and getting the maxiumum power safely from your tune is whats important. A small error can be a big problem with cars under extreme forces, These begin at and sometimes before stage 2.

I Apologise - that I'm a determined guy by nature, full of respect, will power, empathy and patience to succeed which means I am very direct at times in the way things are beyond all the blurb some might access or assess on. Its a strength as I see the world quite different so can problem solve in ways which often could stop others from trying.

Pug208GTI said:
Direct injection sprays the fuel directly into the combustion chamber. So it can't do any cleaning of the inlet valves etc like on a port injected or carburettored car.
 

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I tried Tesco 99 in mine for a few tanks and noticed zero difference other than extra clubcard points
. If anything the car felt happier on regular. So now I run on BP or Shell standard 95. Averaged 45.5mpg over the last 3500 miles somehow!
 

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What despite science, chemistry and physics? I suppose google earth doesnt exist, we have no sat nav nor went to the moon? F1 isin't strictly regulated in fuels?

You wouldnt notice a 1mpg gain or loss over many driving styles plus cold start up when car in open loop is hugely inefficient and would cancel out any higher ron fuel savings. I cant get 22mpg in open loop but can do 5 miles still in open loop.

I'll baffle you some more then that in parts of the world where ron levels are lower than in other regions the map is different so it can run on that lower ron.

I wouldnt try to design a car that can only run on 98 or 99ron fuel as my customers would be a lot less than if it is regular fuel, I could but would be manufacturer lunacy.

Since fuels dont have lead in them anymore valve seat errosion is not such an issue but many countries still have 87-92 ron fuels as standard.

Any respectable tuner will mention that it would be better to run on a higher ron and think they dont make any money on you going to the pump and paying extra, the map is the same price no matter which ron you want it for. They just have a duty of care and want your tune to be safe but people can refuse to understand such a complex subject so its best to just mention it and move on if the customer doesnt except a proven fact.

As I was informed one time "you cant tell em, only they can discover it for themselves when its right for them"
 
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