Tesco Super 99 or 97 Octane

[bobcat]

Originally Posted by ttacornwall

Well there does seem do be a diffrence of opinion on this topic, it is very confusing, for the layman anyway.

bobcat: from my very very limited understanding, for ignition to happen anywhere other than TDC then there would be extra stresses put on the gudgon pin and con rod. When you talk about the timing changing then I assume the ECU changes the firing point on the stroke very slightly?

I will say that all the posts are very usefull and I am sure there are many forum members who will be reading this thread with interest and learning from it, please don't turn it into a personnal war of words with each other, like some of the chipping posts.

exactly, the ecu can fire the spark when the pistion is at different positions,it has to do this due to lots of varying factors - engine speed, IAT, Boost, AFR's.

[pigapumbu]

Originally Posted by bobcat

did you just copy and paste that from a wiki etc?

Well again thats more wrong info in the context of this thread*!!

imagine you had a fuel with a very low ron rating ie, you had to ignite the mixture when the pistion was nearing the bottom of the power stroke (for lower cylinder pressure) to get a burn rather than an explosion (knock), how much torque do you think that engine would make pigapumbu?

the greater the ron the nearer to tdc you can ignite the fuel and thus the more torque you make as your able to harness more of the mixtures energy. You also have to bare in mind that nearer tdc you will have higher pressure in the cylinder, and igniting the mixture there will create higher pressures than if you were to fire further down. so you can get a case were the fuel starts to burns and then as the pressure increases it then goes from a burn to an explosion. This is how you can have varying values of knock.


* however the above can be said to be true if the timing wasnt altered, as the higher ron fuel takes longer to burn and could still be burning on the exhuast stroke. so again its a case of using the correct grade of fuel.


But the std ecu is more than capable of varying its timing for greater efficiency, as well as other little tricks like fuel enrichment for pre-ign.

however if that above statement was copied from a wiki etc then it most likely in relation to engines with fixing timing and in those cases running higher octane fuel would actually be worse for the car assumming its running ok to start with.

Yeah part from wiki. We know you look through it from past posts so I thought it would be a good one to throw in. ,.. and edited it a little to help people understand. But rather than go around in circles and confusing the issue but saying the same thing all others think and know, here are a few links to explain properly. Let everyone read and there is lots of it and decide for their own if a modded car should run on higher octane or not. Thats the best way.

Lets start with the basics on simple english. Link..

Then on to more explanation from Wiki. Link here..

Last but not least, from Dinan. Catch the last bit on pg 4 especially. "how ignition timing adapts to different fuel octane ratings. The same car is represented here, the only difference being the octane rating of the fuel. If you were to add 1° of ignition advance, the engine management system would detect it and retard the timing 1°. You can see that adding timing in the engine management software or "power chip" is futile because the computer will negate the change, as sufficient octane does not exist. However, you can see that adding higher octane fuel is like adding a "power chip" as the system adapts to the better fuel, making more power."
Link..

So tell me after reading all that, do you really think a modified car thats going to run hard be using 95RON or higher? Its simple as that.

cheers

PS: How stuff works. Also a nice site for lots to read. Always best to read and make up ones mind rather than hearsay. And I for one will say, I could be wrong. So do read all this for yourself. How Stuff work..

[pigapumbu]

Originally Posted by ttacornwall

Well there does seem do be a diffrence of opinion on this topic, it is very confusing, for the layman anyway.

bobcat: from my very very limited understanding, for ignition to happen anywhere other than TDC then there would be extra stresses put on the gudgon pin and con rod. When you talk about the timing changing then I assume the ECU changes the firing point on the stroke very slightly?

I will say that all the posts are very usefull and I am sure there are many forum members who will be reading this thread with interest and learning from it, please don't turn it into a personnal war of words with each other, like some of the chipping posts.

The way I see it, the world contains a wealth of information and we just need to look, read, discuss, conclude. No need to start a post by saying, ITS ALL WRONG.. and then go on to confuse the situation even further by having twists in wording. To the lay car enthusiast, it doesn't help.

I have posted a few links in a previous post. To anyone interested in the topic, spend time to go through them. And like all adults, we have the power to make a conclusion. Anything not so clear, I am sure there are many members on this forum who will help.

For me its always going to come down to a clear answer. Should modified cars run on higher octane or not. A yes or no will do. Is a higher RON better or not? and so on.

Cheers all. Keep up the posts. There are bound to be some facts in it.

cheers.

[bobcat]

Last but not least, from Dinan. Catch the last bit on pg 4 especially. "how ignition timing adapts to different fuel octane ratings. The same car is represented here, the only difference being the octane rating of the fuel. If you were to add 1° of ignition advance, the engine management system would detect it and retard the timing 1°. You can see that adding timing in the engine management software or "power chip" is futile because the computer will negate the change, as sufficient octane does not exist. However, you can see that adding higher octane fuel is like adding a "power chip" as the system adapts to the better fuel, making more power."
Link..

Thanks for that.

so that actaully backs up what im saying and not what your saying which says you have to run higher ron fuel.

The above states that a modern engine management system will adapt to what fuel its running, so if your running your car hard on 95 ron and not getting knock it will hold the timing (offcourse over time it will try and advance the timing if it can), if it detects knock it will pull the timing untill the engine returns to safe operation.

so there you go, its safe to run your car hard on 95 ron unless your ecu has been badly modded an had its retard settings changed. even if you have had a remap that has changed the ignition maps for higher ron fuel, the ecu will still adjust the timing to suit the fuel.

if you want better performance and the abilty to maintain performance run a higher octane fuel, however just for getting around stick 95 in the tank like i do - actually run mine on asda fuel.

[bobcat]

Originally Posted by pigapumbu

The way I see it, the world contains a wealth of information and we just need to look, read, discuss, conclude. No need to start a post by saying, ITS ALL WRONG.. and then go on to confuse the situation even further by having twists in wording. To the lay car enthusiast, it doesn't help.

I still stand by my first post, yes i could have been a bit more polite but in the age of forums etc it dosent take much for the wrong info to become so called fact as one person reads it, posts it to someone else, it then gets copy and pasted onto a wiki, which is then copied by other people........

My first post was in response to comments that with higher ron fuel you can lean the mixture out, and by getting a remap you can re-raise the fuel pressure.

Anyway hopefully this post has given the readers of it a better understanding of what using different fuels means.

No hard feelings to anyone ive aimed posts at.
Matt.

[Engineer]

Originally Posted by pigapumbu

A little bit of help here...

RON

Octane rating has no direct impact on the burn of the air/fuel mixture in the combustion chamber. Octane rating is a measure of detonation resistance, not burn characteristics.


FUEL STRENGTH

Note that to a certain extent a fuel with a higher carbon ratio will be more dense than a fuel with a lower carbon ratio. Thus it is possible to formulate high octane fuels that carry less energy per litre than lower octane fuels. This is certainly true of ethanol blend fuels. and we all know what Tesco uses to obtain its high RON. (Duh.. now I know why Vpower has a marked difference than Tesco99)

The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common myth amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption.

So with the above simple explanation, using high octane fuel for an engine makes a difference only when the engine is producing its maximum power. This will occur when the intake manifold has no air restriction and is running at minimum vacuum. something like flooring the throttle. Its then when a higher RON comes to play. And going back a few posts, I think its important when a car is modified, a higher RON is advised to be used. If not,... well let the brave ones put 95RON or less and floor it all the time. I'm sure the standard ECU can cope. ...or not!!!

cheers

You have actually contradicted yourself a wee bit if Greenergy who make the fuel for Tesco use ethanol to boost the octane to 99 RON and therefore this fuel contains less energy than V Power then this will affect the length of the burn time in the combustion chamber necessitating corrections to the ignition timing and fuel delivery whether mechanically or by ECU.

I was generalising pump forecourt fuels as an example to explain the differences combustion chamber design etc. can have on combustion temperatures and so what fuel you could consider using, not all high octane fuels burn slower than lower octane fuels, some actually burn quicker but these are normally race fuels

Cheers

[pigapumbu]

Cool again the same thing being said but going around the bush. Ok.. lets put it this way. Not that I am in the business of modifying cars,.. I think you tend to do some ecu mods which I gather from posts etc.

So do you give a guarantee (written) to your customers that when you modify their cars, they can use 95RON (ASDA or other) and run it hard anytime, any place, cause the standard ECU can always adapt well. Just curious? If so maybe my next turbo volvo, I have a choice.

What others need to ask themselves, if a car has been modified, what would they rather have in the tank. 95RON or higher.. just incase! Maybe its just me. I like extra precaution.

cheers

Originally Posted by bobcat

Thanks for that.

so that actaully backs up what im saying and not what your saying which says you have to run higher ron fuel.

The above states that a modern engine management system will adapt to what fuel its running, so if your running your car hard on 95 ron and not getting knock it will hold the timing (offcourse over time it will try and advance the timing if it can), if it detects knock it will pull the timing untill the engine returns to safe operation.

so there you go, its safe to run your car hard on 95 ron unless your ecu has been badly modded an had its retard settings changed. even if you have had a remap that has changed the ignition maps for higher ron fuel, the ecu will still adjust the timing to suit the fuel.

if you want better performance and the abilty to maintain performance run a higher octane fuel, however just for getting around stick 95 in the tank like i do - actually run mine on asda fuel.

[pigapumbu]

Originally Posted by Engineer

You have actually contradicted yourself a wee bit if Greenergy who make the fuel for Tesco use ethanol to boost the octane to 99 RON and therefore this fuel contains less energy than V Power then this will affect the length of the burn time in the combustion chamber necessitating corrections to the ignition timing and fuel delivery whether mechanically or by ECU.

I was generalising pump forecourt fuels as an example to explain the differences combustion chamber design etc. can have on combustion temperatures and so what fuel you could consider using, not all high octane fuels burn slower than lower octane fuels, some actually burn quicker but these are normally race fuels

Cheers

I was just helping to correct the concept that higher RON = more power by the petrol itself. Power increase is obtained by the ECU readjusting to the higher Octane to gain some more power since the petrol is more stable.

That said, for energy purposes as we learnt in school. what gives more energy per ounce or litre, etc. Then the science comes in and hence what I posted.

and after reading that article, I myself learnt something new. I could not put my finger on why I could see a difference between Tesco 99 and Vpower. I realise Tesco use ethonol based fuels to make the higher RON. Can't remember but I think its 2% mix.

I think for me at least, I want my car to last especially when I run it hard. Its the same reason I put in synthetic oils or DOT4 brake fluid when it asks for 3. So when there is a petrol with higher octane, then it gets used. Why not? And if someone wants to run 95 knowing its not ideal for the max bhp output, then so be it.

For me as I look at it, higher RON is its resistance to detonation by heat sources etc. The benefit is that the ECU gets to run engine closer to optimum. Energy is basically after the spark when which petrol energy is going to give me the most for power output. I like the higher RON and higher Energy petrol.. er within costs.

cheers

[Engineer]

Originally Posted by pigapumbu

I was just helping to correct the concept that higher RON = more power by the petrol itself. Power increase is obtained by the ECU readjusting to the higher Octane to gain some more power since the petrol is more stable.

That said, for energy purposes as we learnt in school. what gives more energy per ounce or litre, etc. Then the science comes in and hence what I posted.

and after reading that article, I myself learnt something new. I could not put my finger on why I could see a difference between Tesco 99 and Vpower. I realise Tesco use ethonol based fuels to make the higher RON. Can't remember but I think its 2% mix.

I think for me at least, I want my car to last especially when I run it hard. Its the same reason I put in synthetic oils or DOT4 brake fluid when it asks for 3. So when there is a petrol with higher octane, then it gets used. Why not? And if someone wants to run 95 knowing its not ideal for the max bhp output, then so be it.

For me as I look at it, higher RON is its resistance to detonation by heat sources etc. The benefit is that the ECU gets to run engine closer to optimum. Energy is basically after the spark when which petrol energy is going to give me the most for power output. I like the higher RON and higher Energy petrol.. er within costs.

cheers

Fair enough but IMHO nothings ever black & white when it comes to vehicle technology despite peoples habit of pigeon holing it for convenience sake and as Matt said it’s not good posting info quoted off the internet or stuff you think is right if you don’t know it’s actually factually based and up to date, this is just miss-information and causes confusion. By the way including bioethenol it’s 5% and for what it's worth it’s not the only anti-knock additive which affects the cylinder flame path timing.

But if you’re happy recommending that people pay more for fuels their particular engine may not need then so be it

Cheers

[bobcat]

Originally Posted by pigapumbu

Cool again the same thing being said but going around the bush. Ok.. lets put it this way. Not that I am in the business of modifying cars,.. I think you tend to do some ecu mods which I gather from posts etc.

So do you give a guarantee (written) to your customers that when you modify their cars, they can use 95RON (ASDA or other) and run it hard anytime, any place, cause the standard ECU can always adapt well. Just curious? If so maybe my next turbo volvo, I have a choice.

What others need to ask themselves, if a car has been modified, what would they rather have in the tank. 95RON or higher.. just incase! Maybe its just me. I like extra precaution.

cheers

it isnt really the same stuff going around, im just answering your questions.

however ive got to ask, in regards to copying and pasting info - why have you given an example (the powerchip bit above) that uses a NA car (bmw)? as NA engines have completely different ignition maps.

this term run it hard seems to keep coming up, you seem to be implying that if running on 95 ron the engine will not last long, but chnage to 98+ ron and you wont have a problem.

you can still get knock on 98+ ron.

I think we are getting to the end of this post now, but to sum up: higher octane fuel will give better performance and economy if you car is mapped\supports it as i will advance the timing. however if you want to run on lower ron fuel the car will adapt its timing to suit. and if on that hot day when running even 95 or 98+ your engine starts to knock it will full the timing back.

so there you go, use what fuel you like. I run my car on asda fuel as its convenient and have not had any problems over the last 70,000 miles ive done using it.