| Author | Message | ||
     KC Saayman Frequent User Username: kc_saayman Post Number: 25 Registered: 10-2004 |
Hi all In a month’s time we will no longer get leaded fuel here in South Africa. I have spent a lot of time reading articles in the archives, and would like to know if I have come to the right conclusions. There are so many varied opinions! Would you agree with the following: 1) We can use unleaded fuel in our Silver Shadow’s, without the need for altering the timing. (Is this true for high altitudes, as well as at sea level?) 2) Additives and lead replacement fuel should be avoided (no Shadows here have cat converters) 3) We should use the highest octane unleaded fuel available. 4) Unleaded fuel should not be left in the tank for more than three months if the car is not in regular use. 5) The same applies to 6-cylinder post-war cars. 6) What about pre-war? Kind regards KC South Africa | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 484 Registered: 9-2004 |
Yes ok to use UL. Do not use any additives,waste of loot. If a cat fitted on any car,still do not use an additive. It may kill the cat. UL fuel can be left in tanks for longer periods it the tank is left totally filled. Pre war cars running with cast iron valve seats, run a larger valve clearance[more cooling] this helps,some say the memmory effect helps but i have not had probs with new valves and ground seats. I have had no probs with old cars [valve ressesion] but am running with Shell optimax ul higher octane also cooler running and more power! Timming depends on what octane fuel is used. | ||
| Robert Wort Grand Master Username: robert_wort Post Number: 252 Registered: 12-2004 |
Hello KC. I can still remember all the hoo-haa ten or so, years ago when we, in Australia were changing to unleaded fuels. There were great recitations about valve seat recessions, holed pistons and god knows what else. A decade on and guess what happened? Absolutely nothing! Our cars are still here and the only ones that aren’t went by the way of general neglect rather than the effects of unleaded fuel. High octane unleaded still isn’t as high as the old leaded fuels but there is no appreciable difference in power. Pre-war and early post war cars ran on Standard fuel, which was about the same octane level as unleaded anyway so there will be no problems there. We are also fortunate that the company in its wisdom had hardened valves and seats. We must remember that there are many countries that always had low-grade fuels and Rolls-Royce had early on taken that into consideration. I wouldn’t panic too much KC., with regular servicing and normal due care you will find that fuel changes will be the least of your problems. While I don’t generally go along with conspiracy theories, there could be a little one here. The Spin Doctors (In this case, motor manufacturers) could well have started this panic so that we would buy new cars. I’m not saying that they actually did start it, but it wouldn’t surprise me, nor do I particularly blame them if they did either. They are in the business of selling cars aren’t they? Interestingly enough, my old hack of a 1978 Ford XC is still going strong even without leaded fuel. 450,000 kms for an old banger aint too bad. My Silver Spur ( ANC04359) runs perfectly on Shell Optimax, so the proof of the pudding is in the eating.  | ||
| David Gore Moderator Username: david_gore Post Number: 532 Registered: 4-2003 |
Hi KC, Do you know if South Africa received V8 vehicles with the low compression ratio for "colonial use" as we did here? If you have the 7.3:1 or 8:1 versions, these will run quite happily on standard UL [92 Octane in Oz] and using premium fuel is a gross waste of money. UK delivered vehicles with 9:1 compression ratio must have premium grade fuel as close to 100 octane as possible; our standard premium is 96 Octane and specialty fuels such as Optimax are around 98 Octane depending on the blend from the refinery. If using 96 Octane in a 9:1 compression engine; the static timing should be retarded by one or two degrees to avoid pinging [pre-detonation]. In Sydney last week, I saw 98 octane ethanol blended fuel on sale which worries me somewhat - not many people are aware that 1 litre of ethanol blend fuel has significantly less energy content available than 1 litre of conventional fuel; vehicles with modern engine management system compensate for this by increasing the volume of fuel supplied by each injector on the intake stroke thus increasing fuel consumption. In older vehicles, you just push harder on the accelerator to get the performance you want also increasing fuel consumption! Time for one of my favourite soapbox topics!! Ethanol blend fuels are a blatant consumer rip-off unless the fuel price is reduced to match the lower energy content. After all, you are purchasing energy at the pump not a fluid to be used and discarded afterwards. The best fuel from renewable resources for our current vehicle fleet is bio-diesel however one has to ask why this has never been given high priority by the farm lobby and government. By the way, I suspect Robert's XC Falcon has enough residual lead in the cylinders after 450,000Km to last another 450,000 on unleaded fuel  | ||
| Robert Wort Grand Master Username: robert_wort Post Number: 253 Registered: 12-2004 |
Good one David, You may just be right with the XC.  | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 26 Registered: 10-2004 |
Thank you for all the replies. You have certainly set my mind at ease. To answer David’s question, I’m not sure if we received the low compression engines, and to add to the confusion, we have many UK delivered vehicles here. Fortunately it is easy to tell if a vehicle was delivered here, or in the UK, as our speedo’s have the Km/h on the outer circle, and the UK vehicles have mph on the outer circle. Is there any way to tell if a vehicle has the low compression engine or not? Regards KC South Africa | ||
| David Gore Moderator Username: david_gore Post Number: 533 Registered: 4-2003 |
Hi KC, A compression test will quickly reveal which compression ratio is used; 7.3:1, 8:1 or 9:1. Unfortunately I cannot find my archive material on actual compression pressure testing values and I hope one of our other contributors is more organised than I am at present with most of my reference material in storage. An uneducated guess would be around 80/100 psig for a 7.3:1 engine; 100/120psig for an 8:1 engine and 120/140 psig for a 9:1 engine. These are values at sea level and these decrease with altitude. Can anyone help with more precise information please | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 27 Registered: 10-2004 |
Thanks David. I am almost certain that we would have received the colonial low compression vehicles, like Australia. I will do some more research on that. Are there any ill effects (apart from cost) with using high octane unleaded fuel in the low compression engines? Regards KC South Africa | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 489 Registered: 9-2004 |
Just one query is the Shadow engine size 6230cc or the 6750cc If the latter Davids lower figures given are correct by the data i have. | ||
| Peter Colwell New User Username: peter_colwell Post Number: 2 Registered: 3-2005 |
The main advantage of using the highest octane fuel available, is that its use will avoid any semblance of pinging. Pinging is deadly to any engine, because when it occurs, - even briefly, - the temperature inside the cylinder rises instantly to extreme levels. The extra cost of premium fuels is very cheap insurance against damage from momentary localised overheating. Most of the time it is not necessary, but even a few second of pinging can do irreparable damage. Better to be safe. Peter | ||
| David Gore Moderator Username: david_gore Post Number: 534 Registered: 4-2003 |
Hi Peter, You are correct especially about the damage caused by pinging - I took the head off my trusty 4WD diesel after 280,000Km and was surprised at the amount of heavy pitting on the top of the pistons and pitting erosion of the edge of the cylinder bores due to predetonation [pinging]. This occurred notwithstanding the fact that the engine has additional combustion chambers and has obviously been designed in the knowledge some pinging is inevitable from variable quality diesel fuel. However, we must also be aware that the actual compression pressure in the engine will be less than the theoretical pressure due to the effect of valves being open during part of the stroke instead of being closed at the beginning of the compression stroke thus reducing the potential for pre-ignition of unstable fuel/air mixtures. | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 28 Registered: 10-2004 |
I have now established that from January our highest octane unleaded fuel will be 95 octane. Is this high enough for the high-compression engines? We will also have a Lead Replacement Fuel, pre-mixed and available from the pumps. However, that will be only 93 octane here at altitude, and 95 octane at the coast. So, in the high compression-engine, do I use 95 unleaded, or 93 LRP?? Regards KC South Africa | ||
| Robert Wort Grand Master Username: robert_wort Post Number: 254 Registered: 12-2004 |
KC., Have you had a look at the online library on the homepage yet? You may find what you are looking for there. Here is the link. http://www.rroc.org.au/library/unleaded/index.html | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 928 Registered: 4-2003 |
KC. If you search this site for LRP fuel topics, you may form your own opinion. Many of us would never touch LRP with a barge pole. 95 RON ULP should be fine. Unfortunately, any pinging would require retarding the ignition slightly. Whilst this is highly undesirable, it is necessary if adequate octane rated fuels are unavailable as the only alternative is a new set of low-compression pistons. Don't even think of buying expensive fuel additives, which no doubt are being advertised like hell right now. Given the change in fuel types, the additive companies can feed on the uncertainty and make a killing for a while. | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 29 Registered: 10-2004 |
Thanks Richard and Robert. Those articles are most interesting! I am trying my best to make an informed decision as to what to do, as I really don’t want to suffer any damage on my engine. My car has the high-compression UK spec engine, which is why I am worried that 95 octane UL is not high enough to prevent pinking. I am also not that keen on retarding the ignition, and want to avoid doing it if I can. Would I clearly hear it if my engine pings? These cars are so well sound insulated, I am worried that it will go un-noticed, and damage the engine. Should the car ping, by how many degrees can I safely retard the timing? Thanks for all the advice and opinions. It is most valuable. I will share it with other owners here in South Africa, as this is a hot topic at the moment. Regards KC | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 929 Registered: 4-2003 |
At the risk of being branded a bush mechanic, this is the method I have used on our big carb, high compression Australian-delivered 1972 T-Series, one of the last so-equipped for the Australian market. This is short of a very expensive session on a dynotuner with electronic analysers, which is no better anyhow in my opinion. I run it on ULP of course, and it has been running ULP for many years trouble-free. It has never run on LRP, and I switched to ULP as soon as the intermediate low-lead fuels were introduced. Check the points and set the dwell if not done recently. Disconnect the kickdown solenoid cable at the transmission. Loosen the distributor clamp a little. Drive the car on the widest throttle opening possible without a changedown at 35mph in third gear. Do this several times, advancing the ignition timing about a degree at a time by hand, no strobe required. With the window open, you will finally reach a point where audible pinging can easily start to be heard. The pinging is unmistakable, sounding like milk bottles rattling in a crate. Driving again in the same manner, back off the timing until the pinging has only just been eliminated. Next, return to the garage. Check the timing reading with the stroboscope (by the book), and note the reading. With a single-point distributor, if it is 8 degrees BTDC or more, back it off to the standard 5 degrees BTDC (as per specification for single point distributors). If it is less than 8 degrees DTDC, back it off three degrees from where it is. With the early dual-point distributor, the figures are 6 degrees BTDC and 3 degrees BTDC (spec value) respectively, again backing off three degrees from where it is if the reading is less than 6 degrees BTDC. In both cases, the 3 degrees minimum margin at wide throttle, low speed, will ensure that no pinging can occur over the entire range as that condition is the severest. Reconnect the kickdown cable and retighten the clamp before a quick final check with the strobe to be sure that you have not bumped it during retightening. You also metion the earlier vehicles. The same method applies: allow the specified timing if advancing it by more than 3 degrees from spec does not start pinging. Otherwise, if pinging just stops less than 3 degrees advanced from spec, back off 3 degrees from where pinging just ceases. | ||
| Peter Colwell New User Username: peter_colwell Post Number: 3 Registered: 3-2005 |
Reading Richard's post on timing to avoid pinging made me think just how amazing the modern electronically controlled engines are. They actually do what is describded, - on a continuous basis, every second, - as we drive. I recently rode a very smooth new BMW motorcycle through Norway. Its compression ratio? 13 to 1. Not a sign of pinging and turbine like smoothness. Amazing. Peter | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 930 Registered: 4-2003 |
Quite correct, Peter, That's why my Turbo R could run happily on 85RON (I use 100RON ULP by the way). With a pair of Lamerholm VR50/1 knock sensors to tell the ECU to retard the ignition if a knock is sensed, it is safe... until a knock sensor, or the ECU, fails that is. It means that, on low power demand, low RON fuel is fine, and the retarded ignition compromise is only applied when it is useful to protect the motor. I prefer the high RON so the sensors are not vital to the motor's survival when driving hard. Most Turbo motors run compression ratios of less than 7.5:1 nominal or less, but the Bentley Turbos have superior response with a relatively high 8:1 and control electronics, and a unique air recirculation system with a dump valve. This all leads to better power and response, and better fuel economy when driven normally. RT. | ||
| Peter Colwell New User Username: peter_colwell Post Number: 4 Registered: 3-2005 |
With all of the foregoing in mind, there is still nothing like a 50+ year old, large capacity, long stroke, heavy flywheel engine, at slow tick-over......the new ones are fun, but the old ones are what makes me smile. Peter | ||
| bob Unregistered guest Posted From: 81.168.83.66 |
Yes you will hear the pinging. I am in the UK and have a 9:1 6750cc. SRH17768. Drive car at 30 mph in top gear. Press the accelerator pedal into the carpet. just before the gearbox kicks down into second is when pinking will show up. In the UK about 15 years ago we went through al this unleaded bit. Before I was using 5 star petrol then I went to 2 star unleaded. The timming had to be backed off from 6 BTDC to 4 BTDC. I found this made no difference to power or ecomnomy. Now I am using LPG which is 110 RON and timing at 8 BTDC. To find this setting I drove the car at 30 mph then full throttle and kept advancing until the engine pinked then backed it off a tad. Then strobed it to find where it was at. (Message approved by david_gore) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 492 Registered: 9-2004 |
Just a note. Aways do the test as above with a fully hot and correct running engine with regard to the carbs fully tuned [balanced and correct mixture]. As for the correct running engine,one that has not carboned a plug valve cylinder etc. This will give premature pinking but not completly timing related. But a sluggish engine will result with heavy fuel use. Nice to see Bob is back with his vast knowledge. Turbo "r" another ball game! |
