Warning POSSIBLE Tesco 99 Poor fuel problem
Discussion
Marf said:
Andyuk911 said:
Marf said:
clarkey318is said:
foz01 said:
clarkey318is said:
Could be that you ran the tank very low before filling up? If this happened the pump will have picked up all the crud from the bottom of the tank.
biggest misconception out there.....
t are more concentrated when there is less fuel. I'd be interested to know why you think otherwise.How did the crud get there in the first place?
Wouldn't any cars fuel system pick up crud as a matter of course given they pick up fuel from the lowest point in the tank?
What is a fuel filter for?
As you can see peoples level of knowledge of cars is amazingly poor.
2. Yes but the crud is more concentrated when the level of fuel is low.
3. For picking up the crud that you claim doesn't exist. They need to be replaced when they get clogged, I would have thought that was obvious. In an in tank system there are two filters, the sock filter and the in line filter. If the sock filter is clogged then the fuel pump will get starved of fuel.
Way to misread my post clarkey/motco 
I never said or implied there was no crud, just challenged the supposition that you shouldnt run your tank down to avoid it.
I'm sure crud will get in the system at some point, what I was getting at is that your fuel system picks up from the bottom of the tank anyway, so crud will end up being picked up, and then caught by the fuel filter.
I never said or implied there was no crud, just challenged the supposition that you shouldnt run your tank down to avoid it.
I'm sure crud will get in the system at some point, what I was getting at is that your fuel system picks up from the bottom of the tank anyway, so crud will end up being picked up, and then caught by the fuel filter.
Marf said:
Way to misread my post clarkey/motco
I never said or implied there was no crud, just challenged the supposition that you shouldnt run your tank down to avoid it.
I'm sure crud will get in the system at some point, what I was getting at is that your fuel system picks up from the bottom of the tank anyway, so crud will end up being picked up, and then caught by the fuel filter.
You said how does the crud get there, which to me meant that you didn't see how it could get there. Must have misunderstood.I never said or implied there was no crud, just challenged the supposition that you shouldnt run your tank down to avoid it.
I'm sure crud will get in the system at some point, what I was getting at is that your fuel system picks up from the bottom of the tank anyway, so crud will end up being picked up, and then caught by the fuel filter.
It gets caught by the fuel filter but if that gets clogged the car will not produce enough fuel pressure for higher revs, I was jsut giving the OP another thing to worry about
The Wookie said:
I wouldn't expect it to be a problem with the specific fuel batch or mixture. More likely water in the fuel from a leaking, rusty old petrol station tank, if the fuel is indeed the problem with the car.
You never know, you might have been the one bloke who had the last tank out of it before it got its weekly refill, and have a car that's sensitive enough to pick up the difference.
Oh and all this talk with knock sensors and such meaning the car 'pick's up' better fuel, just fill it with whatever the manufacturer has stuck on the inside of the fuel cap. Even if it has a knock sensor, if the manufacturer recommends 95 octane, beyond any extra detergents, sticking 98 in wont make any difference. The car will only pink/knock, and thus make any adjustment if it's received fuel worse than it is expecting, there isn't some magic sensor that can tell whether it's 95 or 98.
If the manufacturer recommends 98 with a minumum of 95, then it's mapped to 98 Octane and that's what you should use. If you fill it with 95 then you're relying on the ECU's engine protection strategy to avoid any damage. Perhaps an acceptable risk in a normally aspirated car, but I would never fill a forced induction car with anything less than manufacturer's recommendation unless it was an emergency
Modern ECU's are far more advanced than that, to gain maximum performance/economy they are constantly altering the ignition and fueling to run the engine at it's optimum, they don't just rely on the base map and then a safety strategy, they actively seek out the det point on the fuel in use and use that det point being seen in real time to build up a new active map that is read first. You never know, you might have been the one bloke who had the last tank out of it before it got its weekly refill, and have a car that's sensitive enough to pick up the difference.
Oh and all this talk with knock sensors and such meaning the car 'pick's up' better fuel, just fill it with whatever the manufacturer has stuck on the inside of the fuel cap. Even if it has a knock sensor, if the manufacturer recommends 95 octane, beyond any extra detergents, sticking 98 in wont make any difference. The car will only pink/knock, and thus make any adjustment if it's received fuel worse than it is expecting, there isn't some magic sensor that can tell whether it's 95 or 98.
If the manufacturer recommends 98 with a minumum of 95, then it's mapped to 98 Octane and that's what you should use. If you fill it with 95 then you're relying on the ECU's engine protection strategy to avoid any damage. Perhaps an acceptable risk in a normally aspirated car, but I would never fill a forced induction car with anything less than manufacturer's recommendation unless it was an emergency
My own car for example has active knock control that sees upto 10.5 degrees advance on top of the base map value, it's constantly logging the det point and altering the active base map to get closer to that optimal ignition/fuelling per load site for the current fuel. Thats why you can do things like an ECU reset to bring the ECU back to it's mapped defaults and start to rebuild the actively generated tables again from the original starting point. This can be handy if for example you take a trip to Ireland which generally only has 95RON, once back in the UK it's quicker to do a fill up with 99RON then reset the ECU, than wait for the tables to be overwritten again if you want to pick up performance instantly and populate the load sites to suit the new better fuel, otherwise it will take more time for the transient sites to be changed back to what suits the fuel the engine is base mapped for.
In my car I've got a real time display on my dash showing what the ECU is doing, amongst many other things it shows the active knock control advance and the base map advance levels.
Andyuk911 said:
The Wookie said:
Andyuk911 said:
Indeed, the latest Clio 1.2 TCE Turbo has a sticker on the inside of the fuel cap 95 and 98 ...
There's your answer then!The car has been running on T99 for at least a year ....
There is also a misconception about what the octane rating of fuel really means. All the octane number tells you is how susceptible to det the fuel is, it doesn't tell you how much energy the fuel is carrying. You can have a lower octane fuel with higher calorific content which would give you more power.
When you go up an octane number, you are slowing down the burn speed of the fuel, so if you have an old car that cant actively manage the engine, going up an octane value can make the combustion process slow down, which gives you less power. Thats why on an old points based disy car, to gain a benefit from higher octane fuel you have to alter the distributor timing to advance the ignition more.
When you go up an octane number, you are slowing down the burn speed of the fuel, so if you have an old car that cant actively manage the engine, going up an octane value can make the combustion process slow down, which gives you less power. Thats why on an old points based disy car, to gain a benefit from higher octane fuel you have to alter the distributor timing to advance the ignition more.
A slower burn gives greater BMEP or torque on the downstroke, lower octane fuels gives a faster burn giving a lesser BMEP or less torque assuming each is at their optimum ignition point & at optimum compression ratio. So you are incorrect. Hence a diesel gives massive torque due its slow burn (which is also why they dont rev as at higher revs the burn is too slow to keep up)
A turbo engined car effectively has a variable compression ratio, so at least 4 dimensional mapping is used: That's fuelling, ignition timing, V boost V temperature with knock sensing is used.
Edited by cptsideways on Monday 30th November 23:49
motco said:
Marf said:
Andyuk911 said:
Marf said:
clarkey318is said:
foz01 said:
clarkey318is said:
Could be that you ran the tank very low before filling up? If this happened the pump will have picked up all the crud from the bottom of the tank.
biggest misconception out there.....t are more concentrated when there is less fuel. I'd be interested to know why you think otherwise.How did the crud get there in the first place?
Wouldn't any cars fuel system pick up crud as a matter of course given they pick up fuel from the lowest point in the tank?
What is a fuel filter for?
As you can see peoples level of knowledge of cars is amazingly poor.
sjn2004 said:
kambites said:
TheEnd said:
Andyuk911 said:
kambites said:
Frankly, if your car goes into a "limp home" type mode without recording a fault, it's broken. No piece of electronics should actively enter a diagnostics mode without recording the reason. If the fuel was bad and there was nothing wrong with the car, it would have recorded that it was having some kind of combustion problem, probably a misfire or overheating or something.
No over heating or misfire .... Edited by kambites on Saturday 28th November 19:49
BlueMR2 said:
My last cars engine went pop on Tesco 99. The only other car to do the same thing we knew of at the time was also running Tesco 99.
The ingredients used to make it 99 are not appreciated by especially some older engines so if you run an older car with it make sure it wont damage it first.
I went back to Shell after that and have never used Tesco fuel in my cars since. My Dad uses the normal 95 ron from Tesco all the time though especially with 5p a litre off. I wouldn't use Tescos 99 again though only V Power.
Cobblers! That's easily the most bullsh*t "my engine went pop because..." story I have ever heard. I ran Tesco 99 on a couple of older, well-modified turbocharged engines, and knew plenty of others who did. Surprisingly, none of us ever had any problems which we could attribute directly to Tesco fuel...The ingredients used to make it 99 are not appreciated by especially some older engines so if you run an older car with it make sure it wont damage it first.
I went back to Shell after that and have never used Tesco fuel in my cars since. My Dad uses the normal 95 ron from Tesco all the time though especially with 5p a litre off. I wouldn't use Tescos 99 again though only V Power.
johnfelstead said:
Modern ECU's are far more advanced than that, to gain maximum performance/economy they are constantly altering the ignition and fueling to run the engine at it's optimum, they don't just rely on the base map and then a safety strategy, they actively seek out the det point on the fuel in use and use that det point being seen in real time to build up a new active map that is read first.
Of course what I described is a basic system, and not what you'd expect on a performance car or an expensive aftermarket ECU, but what you've described is still exactly the same principle. I doubt the average light pressure turbo supermini is going to bother with that level of sophistication, it'll probably just have a primary map that's on the safe side of the recommended octane rating, and a secondary map for the minimum stated rating that's triggered by a knock counter. Happy to be proven wrong though.Andyuk911 said:
The Wookie said:
Andyuk911 said:
Indeed, the latest Clio 1.2 TCE Turbo has a sticker on the inside of the fuel cap 95 and 98 ...
There's your answer then!The car has been running on T99 for at least a year ....
cptsideways said:
A slower burn gives greater BMEP or torque on the downstroke, lower octane fuels gives a faster burn giving a lesser BMEP or less torque assuming each is at their optimum ignition point & at optimum compression ratio. So you are incorrect.
I said "When you go up an octane number, you are slowing down the burn speed of the fuel", you said "lower octane fuels gives a faster burn" so I'm not incorrect, we are saying exactly the same thing, you've just read it wrong! 
The Wookie said:
johnfelstead said:
Modern ECU's are far more advanced than that, to gain maximum performance/economy they are constantly altering the ignition and fueling to run the engine at it's optimum, they don't just rely on the base map and then a safety strategy, they actively seek out the det point on the fuel in use and use that det point being seen in real time to build up a new active map that is read first.
Of course what I described is a basic system, and not what you'd expect on a performance car or an expensive aftermarket ECU, but what you've described is still exactly the same principle. I doubt the average light pressure turbo supermini is going to bother with that level of sophistication, it'll probably just have a primary map that's on the safe side of the recommended octane rating, and a secondary map for the minimum stated rating that's triggered by a knock counter. Happy to be proven wrong though.
johnfelstead said:
I think you are downplaying what modern cars have on them to get through the current EU construction regulations. BMW's, even the low spec TDI's have so many programmable tables it's silly, you can even map the performance of the engine mounts!
Really?? that's interesting as I've always thought that would be a good way to get an equivelant dyno reading if you used some sort of shear/load/torque sensing load cell in them.Tell me more, very interested......
Gassing Station | General Gassing | Top of Page | What's New | My Stuff