102 RON; will it make my car's engine happy?

[Menno van Rij]

Nearly all fuel here in Holland has 95 RON octane. I had to search for 98. Luckily, a petrol station nearby has been selling 98 for some years. Until yesterday. When they introduced fuel with 102 RON octne and... no ethanol and no lead - off course. The same type of fuel you can find across the border in Germany.

 

Now, what do you think: can I use this for my TR?

 

Menno

[peejay4A]

I'll be looking for some of that next week in Germany. I'll be interested to see how Eric likes 102.

[Quicksilver]

Hi Menno,

 

have seen this yesterday to. I have to refill my TR4 to day and will give it a try this evening.

 

Firezone is the brand.

 

Marcel

[Peter Cobbold]

If your engine is knocking then 102RON should stop it.

Octane only relates to the ability of a fuel to resist detonation and has no benefit for normal combustion.

Richening the mixture, retarding the spark, running cooler etc are better ways to reduce knock.

 

The high RON can be made by adding benezene or toluene - both of which may be restricted on pollution hazard grounds.

If the company is not using ethanol it may be using MBTE or other oxygentates. These reduce the energy density of the fuel, so consumption will go up a small percentage. But MBTE has its pollution problems:

http://www.essentialchemicalindustry.org/chemicals/methyltbe.html

 

But an engine with 9.5:1 compression should not need anywhere near 102RON. IIRC the TR head is said to be OK on 97RON to 10.5:1

 

Peter

Edited September 6, 2014 by Peter Cobbold

[jean]

Good new for the TR6PI. My 1970 glove box manual says: Five star or 102 Octane fuel to be used.

I believe a TR3 can easily cope with less. Unfortunately old specifications can't be compared with the actual ones .

[Peter Cobbold]

Good new for the TR6PI. My 1970 glove box manual says: Five star or 102 Octane fuel to be used.

I believe a TR3 can easily cope with less. Unfortunately old specifications can't be compared with the actual ones .

A RON value from over 50 years ago can be compared precisely with today's. The method uses a standardised engine ( 'CFR') and compares the fuel under test with pure chemical fuels in identical intake and operating conditions. The test has not changed for decades.

http://www.runyard.org/jr/CFR/octane1.html

So 97 RON when any TR was built is exactly the same today.

 

The reason TR6s were advised to use 102 is because of a design flaw in the PI. It has no acceleration enrichment. It lacks the Weber throttle pump or damped SU dashpot. So it pinks when the throttle is floored. The high RON is needed just to kill a second or so transient pinking.

 

Any TR with 9.5 compression will run fine on 97RON. Indeed any engine with that design of bathtub head and piston crown and similar CR will be fine. If the combustion chamber had been designed with better squish then lower octane fuel or higher compression could be used. A lot depends upon how much turbulence occurs in the chamber after the spark has lit the flame: the more the better, within limits. Thats where combustion chamber shape is so important in the need for RON. More turbulence speeds up the flame (reduces optimum advance) and leaves less 'end gas' to detonate.

 

Petrols have different, secret formulations within standards set by government regulations. The precise design of the fuel can change its 'feel' in an engine. A fuel can be designed to give a crisper response to the throttle etc. But the octane value of the fuel does not relate to that. RON is purely a measure of resistance to detonation.

 

Peter

Edited September 7, 2014 by Peter Cobbold

[jean]

Correct Peter, but here I did not speak about a RON value, but just the octane requirement for a TR. better call it the ONR .. Octane Number Requirement or maybe call it the Road Octane Number for a specific car.

It lies between MON and RON and as far as I could find, its calculation procedure was slightly adjusted over time and even may differ from country to country.

 

While my car runs perfectly on Continental fuels it runs horribly on UK fuels displaying the same octane number.

[Peter Cobbold]

 

 

Correct Peter, but here I did not speak about a RON value, but just the octane requirement for a TR. better call it the ONR .. Octane Number Requirement or maybe call it the Road Octane Number for a specific car.

It lies between MON and RON and as far as I could find, its calculation procedure was slightly adjusted over time and even may differ from country to country.

 

While my car runs perfectly on Continental fuels it runs horribly on UK fuels displaying the same octane number.

Jean,

 

I have no idea what ON and PON Triumph stipulated - maybe for exported cars they did, never seen that In UK.

 

RON and MON criteria are absolutely fixed and have been for decades. They do not change.

 

But it is possible to have fuels with high RON and low MON, or fuels where MON approaches RON. It depends upon the formulation. The difference, RON minus MON, is know as the fuel's 'sensitivity'. Since a higher MON value favours better hard running (hot, more rpm) a low sensitivity fuel is usually favoured in hotter regions.

This might explain why UK fuels appear to be worse in your TR. UK pumps display RON, but the sensitivity if the fuel has to be within stipulated British Standard limits.

Continental fuel may have lower sensitivity than UK, meaning that MON is nearer the RON value. This allows for hotter running engines.

So your poor running in UK might reflect higher UK fuel sensitivity and running the TR with cooler water jacket, cold air intake etc might cure the problem. Running richer will also help, but not easy to adjust with PI. But probably easier than actually finding the RON and MON for all UK 97RON fuels!! And the British Standard ** is behind a paywall.

 

Peter

 

** EN228.

Edited September 9, 2014 by Peter Cobbold

[stuart]

Peter, Jean runs EFI on his 6 so adjustments would be made differently.

Stuart.

[Peter Cobbold]

Peter, Jean runs EFI on his 6 so adjustments would be made differently.

Stuart.

Ah, thanks Stuart. The precision of EFI may have something to do with Jean detecting a difference between fuels. Peter

[MikeF]

Menno

generally speaking manufacturers specify a minimum octane, but not a maximum. Probably the higher number will make no measurable difference, except of they charge more for it [Over simplistically back then a higher octane allowed a higher state of tune]

 

MIke

[MikeF]

Menno

generally speaking manufacturers specify a minimum octane, but not a maximum. Probably the higher number will make no measurable difference, except if they charge more for it [Over simplistically back then a higher octane allowed a higher state of tune]

 

MIke

Edited September 13, 2014 by MikeF

[Quicksilver]

an update; I had the first change of fuel, 37 litre a €1,795 p/l ( euro 95 ron € 1,69 p/l).

 

Before this change there was a problem above 3000 r/pm that unfortunately did not disappear with this change of fuel.

A long story short,I had the following done as well; reset the timing and contact breaker points, check the damper oil (SU), check the float chambers (there was a lot of sediment), fit a new petrol filter.

 

After having above all done, it is time for a ride....

 

I have only done 100 miles now and it performs well. There is no running on (when the engine has been switched of) and the sound of the engine is good, even at higher rpm.

Is it the benefit of the new fuel? I do not know yet.

 

However, the "102 ron competion" fuel does not have any ethanol; this is fine when not driving so frequently as well as for car storage in winter time.

 

Marcel

Edited September 14, 2014 by Quicksilver

[Rob Salisbury]

"a design flaw in the PI. It has no acceleration enrichment. It lacks the Weber throttle pump or damped SU dashpot. So it pinks when the throttle is floored."

 

Peter, is this correct? ..... the Pi system delivers metered petrol by monitoring manifold vacuum ie. high vac on closed or partial throttle, small amounts of fuel, .. low vac, vice versa so when you go to WOT the manifold vac drops to zero and the fuel cam follower drops to maximum fuel delivery point, thus you get fuel enrichment on acceleration. I have to add that I'm still a big fan of the Pi system and it's remarkable tune-ability, (I just can't seem to fine a way of fitting it to my 4A!!)

Cheers Rob

[Peter Cobbold]

"a design flaw in the PI. It has no acceleration enrichment. It lacks the Weber throttle pump or damped SU dashpot. So it pinks when the throttle is floored."

 

Peter, is this correct? ..... the Pi system delivers metered petrol by monitoring manifold vacuum ie. high vac on closed or partial throttle, small amounts of fuel, .. low vac, vice versa so when you go to WOT the manifold vac drops to zero and the fuel cam follower drops to maximum fuel delivery point, thus you get fuel enrichment on acceleration. I have to add that I'm still a big fan of the Pi system and it's remarkable tune-ability, (I just can't seem to fine a way of fitting it to my 4A!!)

Cheers Rob

Rob

Yes, it is right. Any manifold-sited fuelling system whether PI or carbs - on any spark igntion engine - needs transient enrichment to cover fuel depositing on manifold walls. Its a transient phenomenon described in the textbooks** .When a throttle is shut fuel that forms a liquid film on the manifold walls evaporates. Upon opening the throttle some of the fuel ends up being used to re-wet the walls, leaving behind a lean mixture. After a second or so the rate of evaporation from the film of liquid fuel matches the liquid deposition rate and restores the correct mixture. The 'lean spike' lasts a couple of seconds. More here, including measurements of the lean spike from Lucas PI:

http://supertrarged.wordpress.com/2013/06/12/the-lucas-pi-lean-spike/

It would be good to cure it as that would allow the PI at cruise to be run leaner without rattling the pistons upon wot'ing the throttle.

http://supertrarged.wordpress.com/2014/05/26/a-possible-cure-for-the-pi-lean-spike-and-pinking/

Nor would it need more than 97RON.

Peter

 

**excerpt:

http://books.google.co.uk/books?id=mX1-OJBQ6ngC&pg=PA189&lpg=PA189&dq=%22charles+fayette+taylor%22+%2B+manifold+%2B+transient&source=bl&ots=imjmQC8ApS&sig=L8PfgCIkOkv7OfIsdtJD2m18en8&hl=en&sa=X&ei=KFMbVLP_FsO1iwLNi4GwCA&ved=0CCMQ6AEwAA#v=onepage&q=%22charles%20fayette%20taylor%22%20%2B%20manifold%20%2B%20transient&f=false

Edited September 18, 2014 by Peter Cobbold

[Rob Salisbury]

Thanks for that Peter, you've just confirmed my long held belief that I should have done Mechanical Engineering instead of Chemistry all those years ago!! (1968-71)

Cheers Rob

[Peter Cobbold]

Thanks for that Peter, you've just confirmed my long held belief that I should have done Mechanical Engineering instead of Chemistry all those years ago!! (1968-71)

Cheers Rob

Rob,

Zoology '63-'66.

Would have enjoyed mech eng but didnt have the maths....

Cheers

Peter

Edited September 19, 2014 by Peter Cobbold

[Rob Salisbury]

I know, things just don't add up!!