Un-Leaded or don't Worry About It.

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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Clifford Pope
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Re: Un-Leaded or don't Worry About It.

#11 Post by Clifford Pope » Tue Aug 15, 2017 9:24 am

Thanks David, I'd forgotten about that article, but recall it now.

But I'm still puzzled about the actual mechanism, both of original lead tetra-ethyl and of lead-memory:

"When an engine is run hard and at high speeds, the exhaust valve can get hot enough to pull flecks of iron from the seat in the cylinder head. These flecks then get hammered onto the mating face of the valve and become very hard. As the valve rotates (which it is intended to do so as to even out any wear, also to keep the sealing faces clean). "

If an engine with lead memory is "run hard and at high speed", does the exhaust valve still get hot enough to pull flecks of iron from the face?
Does the lead prevent the valve from getting so hot, or does it still get hot but the tendency to pull flecks is suppressed?
If the valve face is coated in lead additive, does it still provide as good a heat contact as direct metal to metal?

Presumably it takes a long time for the protective coat to be laid down? After all, it apparently lasts for years after the use of the additive stops.
Does say manganese additive work in the same manner - ie it will take many thousands of miles of use to build up protection? Can this protection be laid down on top of residual lead memory, or do the valves have to be lapped in before starting the manganese use?

Or do other additives work in a different way - perhaps by influencing the manner of the combustion rather than by a physical deposit?

I remain a bit sceptical - what exactly is the process here? Could it not be that it is the other property of these additives that is indirectly at work: ie the violence of the combustion is mitigated through preventing any tendency to pinking, and that reduces combustion temperature and hence erosion?

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Re: Un-Leaded or don't Worry About It.

#12 Post by David Withers » Wed Aug 16, 2017 7:24 pm

You raise some very interesting questions again, Clifford, but I'm not knowledgeable enough to answer them with any confidence.

Prior to my article, I'd studied the subject quite deeply out of personal interest, and my research plus occupation led to me being given access to the FBHVC/MIRA/ARG tests and results. My article was a collation of most of what I'd learned on the subject at the time - apart from the test results which unfortunately I was obliged to keep to myself - and there's not much I can add to it.

Having said that, I'm pretty sure that lead compounds residing on the valve seats won't reduce the temperature of the valve to any significant degree, unlike - for example - oiling a drill bit where the oil runs away and takes heat with it. Perhaps the opposite happens in fact, as the compound probably acts to a small degree(!) as an insulator, slowing the transfer of heat from the valve into the cylinder head. Its benefit is its performance as an anti-stick and possibly long-life lubricant, somewhat similar to the PTFE (Teflon) coating on a frying pan.

There is nothing to be sceptical about regarding lead memory and the way it works; it's existence and properties have been well known for decades. The only thing that's relatively new is its particular importance in connection with old-technology engines running on new-technology fuel.

As an aside, diesel engines don't suffer from any notable valve seat recession so far as I'm aware, despite the huge reduction in sulphur content in the fuel over the past couple of decades, the sulphur having been important as a lubricant in the injection system (and replaced with chemical cocktails with almost unpronounceable names!). However our company's gas engines, which were very like their diesel equivalents in general construction, suffered in the prototype/pre-production stage from quite severe inlet valve seat recession and valve guide wear. This was caused by the incoming gas washing away any inherent lubricant. The exhaust valve heads and seats were fine.

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Re: Un-Leaded or don't Worry About It.

#13 Post by David Withers » Mon Aug 28, 2017 7:39 am

Here's an interesting article on the origin of leaded petrol: http://www.bbc.co.uk/news/business-40593353

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Re: Un-Leaded or don't Worry About It.

#14 Post by johnnydog » Mon Aug 28, 2017 9:35 am

Again David, a very interesting article which older petrol heads should find very interesting! Or possibly younger petrol heads who haven't really been brought up with leaded fuel!

Links from that article took me to two ther BBC 'lead' articles, which are equally as interesting, although the content of each article overlaps the others to some extent.

http://www.bbc.com/news/magazine-29568505

http://www.bbc.com/news/magazine-27067615
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Re: Un-Leaded or don't Worry About It.

#15 Post by johnnydog » Wed Aug 30, 2017 9:53 pm

Just side tracking, but still on the subject of unleaded fuels, whilst on holiday recently in Bulgaria, I stopped at a Shell garage, and was surprised at the fuels on offer -
Shell 'Fuelsave' Unleaded 95 octane,
Shell V Power Unleaded 95 octane, but best of all .....
Shell V Power Unleaded Racing 100 octane!
I was surprised why the first V Power was only 95 octane whilst in the UK it is 98, but what intrigued me the most was why there isn't the V Power Racing 100 octane in the UK? Wouldn't mind trying that in a PI!!!...........with the appropriate additive of course which could increase the octane level to 102!
The down side to the Shell fuels available there was that they contained a frightening 7% ethanol content, opposed to the UK's current 5%. And we all know the harmful effects of ethanol on older cars...........
Needless to say, the Renalt Megane I was driving didn't merit getting anything other than the cheap stuff!
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Re: Un-Leaded or don't Worry About It.

#16 Post by torque2me » Fri Sep 01, 2017 10:15 am

johnnydog wrote:Just side tracking, but still on the subject of unleaded fuels, whilst on holiday recently in Bulgaria, I stopped at a Shell garage, and was surprised at the fuels on offer -
Shell 'Fuelsave' Unleaded 95 octane,
Shell V Power Unleaded 95 octane, but best of all .....
Shell V Power Unleaded Racing 100 octane!
I was surprised why the first V Power was only 95 octane whilst in the UK it is 98, but what intrigued me the most was why there isn't the V Power Racing 100 octane in the UK? Wouldn't mind trying that in a PI!!!...........with the appropriate additive of course which could increase the octane level to 102!
The down side to the Shell fuels available there was that they contained a frightening 7% ethanol content, opposed to the UK's current 5%. And we all know the harmful effects of ethanol on older cars...........
Needless to say, the Renalt Megane I was driving didn't merit getting anything other than the cheap stuff!
Surely, it is illogical to stock two 95 octane fuels (I guess one will have more ethanol in the mix). E10 (EU standard) allows 10% ethanol so 7% is mid-way.
As to 100 and then needing an additive? Is that something to give lubrication to the injection system?
I use Tesco 99 Momentum (or it was when I last looked and checked the issued blurb (quite a few years ago now) but no additives.
Kev

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Re: Un-Leaded or don't Worry About It.

#17 Post by johnnydog » Fri Sep 01, 2017 10:37 pm

torque2me wrote:
johnnydog wrote:Just side tracking, but still on the subject of unleaded fuels, whilst on holiday recently in Bulgaria, I stopped at a Shell garage, and was surprised at the fuels on offer -
Shell 'Fuelsave' Unleaded 95 octane,
Shell V Power Unleaded 95 octane, but best of all .....
Shell V Power Unleaded Racing 100 octane!
I was surprised why the first V Power was only 95 octane whilst in the UK it is 98, but what intrigued me the most was why there isn't the V Power Racing 100 octane in the UK? Wouldn't mind trying that in a PI!!!...........with the appropriate additive of course which could increase the octane level to 102!
The down side to the Shell fuels available there was that they contained a frightening 7% ethanol content, opposed to the UK's current 5%. And we all know the harmful effects of ethanol on older cars...........
Needless to say, the Renalt Megane I was driving didn't merit getting anything other than the cheap stuff!
Surely, it is illogical to stock two 95 octane fuels (I guess one will have more ethanol in the mix). E10 (EU standard) allows 10% ethanol so 7% is mid-way.
As to 100 and then needing an additive? Is that something to give lubrication to the injection system?
I use Tesco 99 Momentum (or it was when I last looked and checked the issued blurb (quite a few years ago now) but no additives.
Kev
If you go back to the beginning of this topic, and read my post (2nd post in this topic), then the reasons for an additive are explained! The additive is primarily to give protection to the valve seats - boosting the octane rating by 2 if using say Millers VSPe is just an added bonus; more beneficial if using a 95 or 97 grade fuel to bring it nearer to the 100 octane that was available when PI's were first designed.

I have also used Tesco Momentum in my Triumphs in the past, but generally I have always used Shell - primarily as my nearest Tesco is on the wrong side of town, and not usually in a direction that I go very often.

In the UK, Shell V Power is around 98 - 99 octane, but the actual figures didn't used to be widely published by Shell.

As for the VPower 95 octane in Bulgaria, I can only assume that it is a higher quality or more refined fuel dispite being the same octane level.

All the Shell fuels in Bulgaria are 7% ethanol content, which us higher than the current 5% in the UK, dispute the E10 standard. There has been talk for a few years of the ethanol content increasing in the UK from 5%, but thankfully to date, it hasn't. As said, older cars weren't designed to run on fuels with a high ethanol content, with it's corrosive nature doing untold damage to the components of the fuel system without the use of an additive that gives a degree of ethanol protection.
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1967 Mk1 2000 in Gunmetal Grey
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