Petrol

[carryondentist]

Now this is going to seem a really stupid question... but it is one that is rather important to me.

Does everyone run their elans on unleaded (95, 97 or 99 if you are lucky)
??

As for the last 10+ years of elan ownership I have run my '90 SE on 4*, then LRP or unleaded or unleaded with lead replacement additive. Now I was browsing through the elan sales leaflet and it says fuel 98ron 4* or 95ron unleaded...

So my question is.. does the engine management compensate for this and can the elan be run on either with no damage to the valve seats?

Thank you for your help!

[muley]

Now this is going to seem a really stupid question... but it is one that is rather important to me.

Does everyone run their elans on unleaded (95, 97 or 99 if you are lucky)
??

As for the last 10+ years of Elan ownership I have run my '90 SE on 4*, then LRP or unleaded or unleaded with lead replacement additive. Now I was browsing through the Elan sales leaflet and it says fuel 98ron 4* or 95ron unleaded...

So my question is.. does the engine management compensate for this and can the Elan be run on either with no damage to the valve seats?

Thank you for your help!

Yes and Yes

Jim

[Nige]

SE and NA are fine on leaded or any suitable lead substitute added to unleaded I have no view or knowledge of the effectiveness of the various lead substitutes but was advised to use Millers VSP in my S4 Elan. Under no circumstances whatsoever run an S2 on leaded (if you find it) as it will destroy the Cats, for the same reason I advise against using lead substitutes although I am less certain of their potential harm to the Cats.

However, bottom line is the car runs perfectly well and without adverse effect on unleaded, it will run just fine on 95, 97 or 99 octane but if you are driving hard or have any mod which increases boost beyond standard then I advise using the higher octane fuel as this will delay the onset of knock which when detected causes the ECU to retard the ignition which reduces performance (this is how the ECU compensates) for different octane fuel.

[johnbenk]

Hi

Leaded petrol helped with the valve seats on certain types of engine

(injected TR 6). the lead actually lubricated the valves.

With advent of unleaded the Lotus engine with replacable cast iron valve guides and sintered steel valve seat inserts is able to run on unleaded 95 97or 99 if available.

The ECU will adjust for the grades as there is a "knock sensor" in the engine to stop damage shoud detination occur caused by using diffent grades of fuel.

The ECU also has a learning curve and you may find that if you fill up
with SHELL OPTIMAX or BP 97 the engine may RUN BETTER.

The engine in my view GETS BETTER WITH MORE MILEAGE and if serviced correctly (CAM BELT ETC) could do upto 200,000 miles without major parts needing replacing.

Question



Why do when buying a Lotus Elan people want a "low mileage" example when there are better cars that may have a higher mileage AND HAVE A GOOD SERVICE HISTORY would in my view be a better choice.

They may need seals replacing on the doors hoods etc but the engine will be well run in and be better driver than a "tight" 30,000 mileage car

Any views please????????????

[Scott J]

Unleaded fullstop.




ALL Lotus engines have ran unleaded since the 900 series engines way way way back in 1973.

Optimax will give you a bit more oomph though

[TheBard]

Numpty time again, but here in Virginia I have a choice of 87 89 91 and 93 octane petrol??? Now is this the same RON value as in the UK?

Currently I drop in the 93, and add a Prestone "octane booster", and get about 28mpg. Should I add the booster, or just go back to daydreaming about Shell Optimax?

Cheers,
Ian

[pjohn151]

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel through a specific test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of isooctane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON), which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "normal" gasoline in the US and Canada, would be 91 in Europe.

The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.

It is possible for a fuel to have a RON greater than 100, because isooctane is not the most knock-resistant substance available. Racing fuels, straight ethanol, Avgas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher. Typical "octane booster" additives include tetra-ethyl lead and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition.

Phil

[Candles]

Awesome level of knowlegde!

[nitroman]

Phil, you sound like the logical person to ask this question of. Something I've always wondered is, on a FI car sans converters, will adding a Tetra-ethyl lead octane-enhancer clog the fuel injectors?

[pjohn151]

Unfortunately that knowledge is based on my work bible that is the Bosch Automotive Handbook, so sorry Nitroman, I have no idea...

Phil

[Aurora40]

Numpty time again, but here in Virginia I have a choice of 87 89 91 and 93 octane petrol??? Now is this the same RON value as in the UK?

Currently I drop in the 93, and add a Prestone "octane booster", and get about 28mpg. Should I add the booster, or just go back to daydreaming about Shell Optimax?

Cheers,
Ian

FWIW, the best way to tell if you need more octane would be to scan the car under load. I tend to do this in 3rd gear on a flat open stretch of road through the rpm range, and see if the ECM is using any knock retard. If there is none or only a degree or two, you probably don't need any more octane and wouldn't have any benefit from it. Generally you'll notice any knock retard around the peak torque rpm since generally cylinder pressures are highest then.

Here's an interesting article on gas and additives. Not a gospel, but interesting. One thing that struck me is the mention of MMT and that manufacturers feel it compromised durability. That's the octane booster in the Prestone 0-60 product you are referring to.

http://www.idavette.net/hib/fuel/index.htm

Nitroman, I'm no expert (by far) but I wouldn't think TEL would hurt your injectors. But I have heard it can coat your O2 sensors and cause them to get lazy over time. There are a few ZR-1'ers I've heard of that keep a second set of O2 sensors just for use at the track, so that they are the ones that get messed up by the leaded racing fuel they run there.

Edit: as an aside, the EPA in the last few months repealed their requirements for oxygenated fuels, so hopefully ethanol will be less common at the pumps in the US.

[nitroman]

...you probably don't need any more octane and wouldn't have any benefit from it.

Except for one thing. Lead provides an excellent valve-seat "cushion". That is why cars had to start using hardened valve-seats when lead was pulled from petrol. My Maserati would audibly run more quietly when using a lead additive; and in fact required a valve job after I stopped using it. It had one cracked valve almost like someone took a slice out of a piece of pie.

As an aside, has it made the news in the UK that there have been 3 fatal alligator attacks in the last week in Florida? http://www.news4jax.com/news/9224137/detail.html

[Aurora40]

Well I was replying to choosing an octane grade from the pump or using a street legal octane enhancer, none of which will contain lead.

Do many Elans suffer valve problems over time? There are certainly disadvantages to using lead. I'd think the main reason people would use it is for the octane boost on a heavily modified engine, not to quiet valve noise. But it's your car and your call of course. I would say you must have a quiet car if you can hear the valves seating against the head over the sound of exhaust, intake, tires squealing, and whatnot!

Is your car on the juice or have other major power adders? Just wondering from your screenname and your wanting to use leaded fuel. Seems like more of a dragracer thing (or NASCAR I guess) Would the O2 swapping thing work for you? I'd guess you'd want to have the cat removed too, as I *think* leaded gas can clog them up over time, but I may be mistaken. But if you don't mind somewhat shorter life from some of the engine control components, I'm sure you could run leaded fuel without issue. Do you, or anyone dragrace? Generally speaking, on any car board I check out, I search first for 1/4 mile times because it's an interesting yardstick by which any car can be measured. But I couldn't find any times here. Does anyone run their Lotus in the 1320'?