Shark Man

Now this is probably unanswerable to the majority


What I want to know is if manufacturers measure the burn rate of their Petroleum fuels. And if it is specified, what is it.

I know that typically, higher octane fuels burns slower, due to the additive they use to obtain the higher knock rating. But, understandably this will differ from manufacturers of fuel with teh same octane depeding on what additive they use.

For example. I would like to know what the difference in burn rate that a traditional 98Ron 4star leaded fuel is compared to Shell 98Ron Optimax and BP Ultimate and Tesco Super 99Ron.

The reason for doing so is I have a vehicle that ran on 98Ron 4 star leaded. When running 98Ron unleaded fuel, like Optimax I should maintain power and not need to adjust ignition timing from stock.

I have found this is not the case, and I'm almost certain that a factor in this is the fuels have different burn rates, which require a different ignition timing for the fuel, despite it have the same octane. So I would like to confirm this, if I had access to the data.

Also would be handy to know if there is any differece in calorific value per litre for each of the mentioned fuel, as this would be another factor that needs to taken account for. As from what I gather, non-flammable additives used to reduce knock, can lower the calorific value of the fuel, giving less bang for you buck. Again I need the data to confirm this.

Thanks in advance

MJW

Where's Mycroft ..... ?

Rioja

I think the speed a fuel burns at is measured as the 'flame front speed', did a search on this and got this website; http://www.gardlite.co.uk/page11.html

Hope it helps.

David Lock

May be worth a gander?

http://www.intertek-cb.com/newsitete...FQIgXgodcUZcpA

Shark Man

Thanks

The Miller's link does provide confirmation of the difference between leaded an unleaded, although maybe biased on the promotional side of a product. I still think its valid. Might try some Millers as a temporary measure and see if it will behave itself on stock timing/fueling until I get more permanent solution.

I'd still like to know what differences in the burn rate or flame front speed between different brands. I know they do burn differently - as shown by the masses of fuel threads and mapper's preferences. How differently remains the question.

Still fathoming out the other link

David Lock

Don't forget it's not just RON there is also MON (Motor Octane Number) value which will have a bearing on the matter and may well be different for unleaded and leaded of the same RON.

Bruce Hamilton's stuff is always worth a read if you have a spare week

http://www.faqs.org/faqs/autos/gasoline-faq/part1/

dl

What car is it btw?

MJW

There was a thread a while ago on the GTR register about this sort of thing ..

http://www.gtr.co.uk/forum/upload/24...e-booster.html

Shark Man

Thanks, Looks like I have some more reading to go through.

Car is an unhappy '82 XJ-S. I've got an exhaustive check list to go through, and fuel is one of them.

I know this is not the main cause. But would be minor contributary to the requirement of slightly different timing and fueling, especially when using original factory data as a reference point.