Premium fuel difference?

5th December 2008, 22:07

yo vts owners... can anybody vouch for the use of premium fuels?
seeing as though the map is wide enough to cope with 98RON, do you perceive a power difference or economy difference?

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5th December 2008, 22:24

i'm not a vts owner lol, but when i use high octane in my 2ltr turbo i normally get a few more miles off a tank. i normally get about 200 miles of £45 but high octane maybe get 220ish? the performance goes up a little bit, like driving your car on a cold day, just fit more oxygen psi in the cylinders.

5th December 2008, 22:27

I own a MK2 vts and i always use BP ultimate, i no that not everyone will agree but i personally believe that the car performs better and the economy is better than using 95 ron standard unleaded.

5th December 2008, 22:30

For the most part there hype and as you quire rightly point out the cars are tuned to run on your normal sludge that come out of the pump. Really to take advantage of any of these fuels you would at very least want to increase compression, advance the ignition and possibly even cam timing slightly. You may even consider running a higher temp thermostat. I suspect you would be far better spending money on changing engine oil and all filters a little more often as this would increase fuel economy, clean your engine internals, make everything last longer, give you more power and well everything and more that they claim the fuel may do.

6th December 2008, 02:40

i do, but i just like the smell of it

6th December 2008, 04:26

I've always run my westcoast on Opti flop 99RON.

The 1.4 engine always used to idle smoother and generally run better on it and seeing as the 16v engine is high comp i like to keep it on 99

6th December 2008, 08:33

As Ax has already stated...

To gain any performance from the higher octane fuel, the ignition timing would have to be advanced, and that's only if the ignition timing isn't currently spot on. For example, if you're running 95RON and your ignition timing is spot on as such the maximum power output from the explosion is taking place exactly where its most optimum - normally around 20 degrees after TDC - then moving to a higher RON fuel won't do anything for you.

I don't know whether or not the stock ECU on the Saxo makes any adjustments to the ignition timing on its own accord, in fact, I would kind of doubt it. Probably the only thing it will do it retard the timing if the knock sensor picks up on something.

I'm not hot on turbo charged set ups, but from what I can gather, a main reason why they drop the compression ratio is because the performance loss of a lower compression ratio is far less than the performance loss of an ignition timing that's far too retarded: to stop knocking. You see, you always want to achieve that maximum power output around 20 degrees after TDC. If knocking is preventing you from achieving this, it's more benificial to lower the CR and get the ignition timing spot on, as opposed to just retarding the ignition timing. Of course using higher RON rated fuel if the solution, but you can't do this for your typical road car.

It's also worth mentioning that the premium fuels tend to be better fuels anyway, and can give a greater energy release during ignition, so there's every chance that without any intervention from the ECU as such, you could get more power from the engine with these fuels.

6th December 2008, 09:29

Hi there,

just a couple of points, and a few corrections. Max cylinder pressure needs to be around 14 degrees, 20 is a little too late.

Higher octane fuels are more resilient to uncontrolled explosion. For example due to hot-spots in the combustion chamber, and higher compression.

Higher octane fuels burn SLOWER, hence the *requirement* to advance the ignition.

Since they resist uncontrolled burning, they are more ideally suited to the turbo environment which is extremely hot and more turbulent.

Hope that helps

Andy
PS Yes, higher octance fuels will be of a better quality

6th December 2008, 12:29

its better for the engine anyway soo, might aswell use it.

6th December 2008, 12:38

the vts feels alot better on 99ron from tesco, i always seem to get more MPG as well.
The same goes for shell, i can tell that the car runs alot smoother on the opitmax than it does on the equivelant bp ultimate.

if i have been stuck and had to use the pish unleaded, it dosnt seem to last as long and dosnt feel as smooth.

im always trying to fill up with the tesco 99ron

6th December 2008, 14:27

I dont notice a difference tbh, i havn't checked my MPG between the two but i think i will do.

6th December 2008, 14:37

I noticed smoother running but with more mpg there was a difference but not huge

6th December 2008, 14:42

Quote:

Originally Posted by Sophia_Bush

I noticed smoother running but with more mpg there was a difference but not huge

yea i agree, just gotta work out if its worth paying the extra, i run my sax on 95 cos its pointless on anything else really cos its only a vtr, but my other car i run on high octane cus its a turbo so it can make the most out of thhe high octane

6th December 2008, 17:33

20VT marea - sleeper!

6th December 2008, 18:09

Quote:

Originally Posted by luthor1

Hi there,

just a couple of points, and a few corrections. Max cylinder pressure needs to be around 14 degrees, 20 is a little too late.

Higher octane fuels are more resilient to uncontrolled explosion. For example due to hot-spots in the combustion chamber, and higher compression.

Higher octane fuels burn SLOWER, hence the *requirement* to advance the ignition.

Since they resist uncontrolled burning, they are more ideally suited to the turbo environment which is extremely hot and more turbulent.

Hope that helps

Andy
PS Yes, higher octance fuels will be of a better quality

This is also why in many test high octane fuel and octane additives have often proven to loose power. I recall one test that utilised a standard rover K series engine that showed substantial power losses with some of them.

People often confuse octane ratings with how much power a fuel will give. When this is not so and in reality its often the other way round. It is really the calorific value of fuel that defines how much energy it contains. The octane rating in simplistic terms refers to how stable the fuel is within the engine and in so allows it to be used in a more exstream environment ergo more exstream engines.

This is why to take advantage of high octain fuels you really have to increase the compression of a engine and/or on a boosted car increase the boost pressure. There is the matter of timing but as people have pointed out generally speaking manufactures will general have it set quite tight to the fuel the car is specified to run on.

6th December 2008, 19:12

cheers gang. Up until I changed from my 1.5D to my petrol saxo I'd never seen the point in putting premium petrol into a saxo. However I've just completed 300 miles using V-Power and the difference (MPG) was quite noticeable in fact - which was a little surprising seeing as though I thought it would take a while for the ECU to adjust.
Anyway the result was... an extra 35 miles to half a tank (usually get 200, got 235)

so if that continues it'll stay on v-power. couldn't tell any performance difference tbh

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6th December 2008, 19:13

saxo has a map from 95RON to 98RON btw...

7th December 2008, 11:30

Quote:

Originally Posted by adsayer

saxo has a map from 95RON to 98RON btw...

Yours or all saxos?

7th December 2008, 11:39

i run mine on wine... its cheaper!

asda deals ftw!

7th December 2008, 12:04

Quote:

Originally Posted by Goodwrench

Yours or all saxos?

says in the handbook matey

7th December 2008, 12:15

Since I've moved house I've been using Tesco's 99ron stuff. Performance wise, it's the best fuel I've ever put in the wee mota. AFAIK, Tesco put a little methenol in the mixture.

7th December 2008, 12:19

it's bioethanol actually Toady

7th December 2008, 16:36

I've always tried to go for T99, even when driving a 1.1 lol its betterer!

7th December 2008, 18:03

Quote:

Originally Posted by adsayer

it's bioethanol actually Toady

LOL. I was close... ish.