Hi All,
Having read some high quality technical input on this forum, I?d like to pick everyone?s brains on an issue that is vexing me but one you probably haven?t come across before: that of running modern car engines on LEADED fuel.
Background
Here in Jordan almost all the second-hand cars imported into the country are sourced from Europe (Germany provides 75% of total, mostly BMWs and Mercs) or the USA, i.e. are catalyst equipped. However, you can only get UNLEADED fuel at a few fuel stations here in the capital, Amman. UNLEADED is simply not available at all outside the capital. So most people just fill up with the 4 star or 2 star that is widely available and cheaper than unleaded to boot. Crazy government policy, I know, and this is before we get into the discussion of the total prohibition of diesel-engined passenger cars and station wagons!
After a while, most cars suffer a significant performance drop which is normally resolved simply by sawing off the now-blocked catalyst?(The all-too-true joke goes: You can give a [insert Third World nationality] a brand new, top-of-the-range car and he?ll bu66er it up in two weeks but keep it going for 30 years?) Anyway?
My question is:
What are the long-term effects of running cars designed to use UNLEADED on leaded fuel? Either in general terms or vehicle specific.
Issues to consider might be: fuel injection system, ECU control of timing, combustion temps, combustion chamber materials, spark plugs, Lambda sensor. Some vehicles have an additional sensor in the catalyst itself ? what happens when that is removed/ disconnected (apart from a dashboard light coming on)?
A subsequent issue is that of the removal of the catalyst itself and the subsequent change of exhaust backpressure that may have a detrimental effect on engine longevity. What effect might this have on exhaust valve temperature?
Whilst most interested in people?s opinions, I am also looking for research papers and test results, both lab-controlled and any owner?s experiences.
Of course, much has been written about using UNLEADED in old LEADED-spec engines e.g. valve seat and ignition timing issues. Looking for answers to my question I have spent many an hour with search engines, but as yet to no avail. Here is where any web whizzos might be able to help. Obviously, there is not going to be a huge amount of info to answer my question, as it is not relevant to most car users. But I would hope that somewhere there might be something useful or interesting.
The reason I would like this information is that many of my acquaintances know I am an automotive engineer so I get constantly asked for advice on this one. Until now, I can only offer second-hand anecdotal evidence, which I will gladly offer if anyone is interested.
I would be delighted to discuss this at length on email wilson@nol.com.jo
Sorry for the long post and I hope someone can help,
CMark
"Don't tell him, Pike!"
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Running a modern car on leaded fuel is going to cause a number of problems:
1) The cat will fail. OK so remove it.
2) The O2 sensor will fail by being polluted by the lead, OK so remove it.(except that...)
3)The management system won't run properly without an O2 sensor.
etc etc
I can't really see how you are going to get around this problem unless the later generation of O2 sensors are unaffected by the added lead.
Perhaps someone can enlighten us...
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I had mate with a Pontiac that pre-dated the catalyst requirement of Mot test, so when the cat went he replaced it with a length of tube, but I think he kept the lambda sensor. It sounder much nicer, and he reckoned it had little or no effect on performance. 10 years later it may be a different story, but fuel injection can be remapped, so I wouldn't think it was too much of an issue. The plugs may go yellow and need cleaning more often.
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CMark
You've identified the key problem of the catalyst being destroyed by the lead in the fuel, but its removal solves that one. This may reduce back pressure on the engine and slightly upset the engine management, but I doubt that's a big problem.
There was a useful article in the Morris Minor Owners Club Magazine a while back, and this is a summary of the issues.
The main problem with leaded fuel is more related to the combustion chambers. Why was lead (in the form of tetra ethyl lead) added in the first place?
In the 1920's the US Navy started using it in aircraft engines to enable higher compression ratios, reduced pinking and hence more power. Octane ratings of fuel were then probably in the order of 70 or 75. It works by decomposing in the flame, leaving a 'fog' of lead oxide which reflects heat and reduces combustion speed, reducing detonation (pinking).
Now, the lead isn't ideal. The lead which exits corrodes the exhaust valve on the way, and the remainder forms that hard deposit on the valves and cylinder head we used to call 'carbon' and which needed regular removal. Remember decarbonisation? The regular decarbonisation of engines was accepted, and it allowed the damaged valves to be reseated or replaced at regular intervals. It was even noted that high speed use of engines was best achieved on 'non-ethylised' fuel to avoid valve burn out.
Nevertheless, the benefits in power output were considered worth pursuing, and various methods of adding chemical eliminators to the fuel to reduce this regrettable tendency to wreck the engine were developed and used. These included ethylene dibromide, which reacted with the lead producing lead dibromide, which melted at a much lower temperature than the lead oxide, and so was expelled from the chamber. It was found this protected the exhaust valve seats, which was a bonus. It formed the white deposit you'd see on the inside of cars exhaust pipes after a good thrash on leaded fuel. The problem is that the eliminators don't completely solve the problem and TEL still tends to cause valve corrosion and seat problems. Various steels were developed to reduce the problem to manageable proportions, and this was the situation by about 1990.
Which leads us to the modern engine and leaded fuel. You'll certainly get a more extensive build up of 'carbon' in the engine and on the valves, significantly harder and more adhesive than with unleaded. We can't assume that the valve material is designed for the damaging effects of lead, as unleaded fuel already has octane ratings up to 98. There's therefore every chance of reduced valve and seat life. Not ideal and not exactly what you might expect.
Regards
John S
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I would imagine a discussion with the engineers attached to the export sales department of the relevant manufacturer might help on this. Until 2000 I was in Syria where the petrol is much the same as in Jordan (or at least no difference was detectable in general running). Our 'company' cars were often a bit long in the tooth but were mostly Volvos and US Fords. The big late 90s Volvo estates were not supplied with catalysts but were prepared for this export market. I am not certain about the smaller Dutch-built ones delivered new in 2000 but I am pretty sure they were also tuned for Middle East fuels. My mid-90s Ford Taurus V6 certainly had no catalyst and had completed nearly 160,000 km on Syrian leaded, as had the other 15-20 examples in the fleet.
I can't imagine Volvo and Ford are exceptional in this and the other manufacturers must have the knowledge to allow the removal of at least some of the emissions gubbins for this market. What about all those shiny Mitsubishi taxis going around Amman? Surely the owners aren't hunting down only unleaded fuel for those?
Sorry this isn't really of much help re non-local market imports but I am sure the information is probably with those makers who have markets outside the USA and Europe.
PS: Great Chinese by the Fourth Circle (or is it Fifth) but then they are a bit scarce on the ground in that part of the world.
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Thanks all for your replies and now "our" weekend is over and the family asleep in bed I can provide some deserving responses :-)
Hi Andrew,
instead of simply removing the O2 (Lambda) sensor, how about just replacing it when defective? Any ideas how long a new one should last when run on leaded? 10 miles, 1000 miles or 10,000? If they have a short life, instead of just removing it, a mate of mine suggested making up a "black box" to replicate the output of this sensor to trick the ECU into thinking it was still present and correct. However, as the sensor plays such a crucial role in keeping the fuelling stoichiometric (i.e. they are constantly feeding back in a closed loop to the ECU to prevent the mixture being too rich or too weak), I thought it would be probably be too tricky to do so. What do you think? (My mate does have the capability to make up some pretty neat little gizmos.)
Is it possible to "decontaminate" them? Can the lead (Pb) be cleaned off? Perhaps ultrasound? I had a look at www.lambdasensors.com (Just Lambda UK) to view pictures of the common sensor faults - no mention of cleaning there.
Hi Doug,
was your Pontiac owning mate running on 4 star or unleaded?
Hi John,
interesting background info made me realise I knew only half the story and as you say, "not exactly what I expected". I assumed that the hardened, unleaded valve seats would be fine. Not so, it seems.
Hi David,
you make some good points along the same lines of my thinking. What also confuses the issue is that some franchised dealers in Amman sell EEC spec new cars (unleaded only) and others sell Gulf spec (leaded compatible). For example: all new Subarus from the main dealer are EEC spec. whereas Toyotas are Gulf spec.
My 1995 Grand Cherokee 4 litre (currently 140,000 kms) is an "export" model bought new in Amman; leaded spec with neither catalyst nor Lambda sensor. However, a colleague here has a US spec 2000 model with the new 4.7 litre V8 which, he has been told by the Jeep export service department, must always be run on unleaded with no possibility to convert to leaded (contrary to what was told him by the selling dealer! "No problemo," he said "just remove the catalyst when you get to Jordan"). What I should find out on my next trip to the Jeep dealer (and they are frustratingly frequent) is whether that 4.7 V8 engine is also available in Gulf spec. (I would have thought so considering how popular these cars are in this market).
PS you wouldn?t recognise 5th Circle now! It is a four-way underpass flanked by 2 huge new hotels (with no occupants) and not a Chinese in sight!
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Isuzu, it seems, have 2 similar but different petrol engines for their Trooper selling in the 2 different markets, leaded and unleaded. In the US and EEC they offer only the newer 3.5 litre V6 (with 215 bhp), whereas for Rest of World applications they retain the 3.2 litre V6 (with 205 bhp).
Based on the above facts, one might therefore conclude that it is cheaper for Isuzu to do this than to modify the newer unleaded-only engine to be compatible with leaded fuel. (This theory assumes that the engines themselves are similar in terms of unit build costs and that it would be cheaper to maintain one production line building twice as many of one engine than two production lines, etc.)
One might also conclude that they have already tested the newer engine with leaded fuel and found it does not meet their standards. And they are probably pretty fussy about their standards; in the USA Isuzu offer on all their SUVs a 10 year, 120,000 mile powertrain warranty, which they claim to be the longest in the industry. The assorted bean counters at Peugeot and Vauxhall (amongst others) must wince at the very thought, judging from all the posts about expired engines on this site.
It is this very policy of Isuzu's of providing 2 different engines that is one of the cornerstones of my uncertainty with this discussion subject. They must reckon it is worth their while.
Incidentally, I know of a EEC-spec Trooper which is thrashed up and down from here to Baghdad at 180 kph, is run half the time on "half-star" leaded Iraqi petrol costing 2 quid for a 90 litre tank-full, has got over 100,000 km on the speedo and still has the original cat fitted!
CMark
(humorous film quote deleted ;-)
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The cat probably died 99,900 km ago, and just became an exhaust pipe.
The Pontiac ran on 2 star as was, if I remember rightly.
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CMark
Interesting. Confirms the info. I have that it's not just the cat etc that need to be removed from engines to make them suitable for leaded. Sounds like there are mechanical differences too.
Regards
John S
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