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When you fill up with 98 octane, is it Shell or the other brands?
I have found Shell's formulation of 98 octane the worst of the lot. Ask any Subaru WRX club member or Harley Davidson club member who has been around for a while and they will avoid the Shell brew.
Try BP or Caltex or Mobil. Now, the fuel experts will come out of the woodwork to say that the fuel is all refined from the same place, but I beg to differ.
Usually fill up with Caltex or BP. The current tank has Caltex in it. Thanks for the comments :D
Cheers
Quote:
Originally Posted by tempestv8
mate ......its all refined in the same place .....:lol2:..............
:oops2:(sorry..at the risk of being accused of bringing attention to myself to boost my own ego...that was joke ...lol)
Unleaded Fuel Types Octane Rating:
Unleaded ULP
(also known as Regular Unleaded) 91 Octane
Premium Unleaded PULP
(Caltex Premium Unleaded is called Vortex Gold or Ampol Gold) 95 Octane
Higher Octane Premium Unleaded Fuel 98 Octane
BP Ultimate
Shell Optimax
Mobil Synergy 8000
I've can tell you the Shell is crap. It leaves deposits big time.
The BP & Mobil are much cleaner. When I used Shell after one week of around town use at 2000 RPM at the time, give it a 4500 rpm squirt and a large cloud of white smoke:eek:
Won't do that with the other 98 fuels.
Talk to anyone using in bike racing & karting using a high performance 2 stroke engine, they won't touch the Shell stuff.
A dodgy MAF reading will give these some pinging symptoms too, as the fuel mix will lean out and combustion temps go right up. I know testbook said no faults, but if you are getting a Kg/hr airflow reading at hot idle of less than 25Kg/hr, then there is a problem with the MAF. A normal reading should be in the region of 30 to 35. I have fitted many to these model V8's and it is a similar symptom. Poor running, 'Catalyst damaging misfire detected' fault codes coming up, etc etc .
JC
Thanks for that information Justin. I will be asking the mechanic that.
Could this still be the case if the MAF was only recently replaced (12 months ago) ?
Cheers
Peter
Just out of curiosity which V8 do you have?
The low or high compression one? Mines a 2000 model with the lower 8.23:1 compression.
https://www.aulro.com/afvb/
hiQuote:
Originally Posted by cucinadio
it might be refined in the same place, but if i were to order a product i would want it to be a certain way (my own formulation, the way i ordered it, because i am paying for what i get). Each "batch" would be made to order for each customer based on their needs and budget. The refinery would not care what goes into the fuel, just concerned with only a few things
1. that the customer pays for what they ordered
2. They can operate within government legislation ( get away with what they can, putting what ever makes the product cheaper).
3 That the customers return for repeat bussines. That Shell, Mobil, Caltex or whoever order more fuel from them.
In a nutshell they dont give a crap about the fuel, just as long as it is what the customer ordered and "Oils aint Oils". So if a fuel supplier orders an inferior product, maybe the only ones who know other than them are the customers through hard experience.
I am not a chemist nor does my back shed have a labratory so i cant test the fuel.
I would listen..... expensive mistake.....E10???
Cheers:D, alturbo68
Im not a mechanic, but this post tweaked my interest as i never imagined an EFI car would ever suffer from pre-ignition.
Pre-ignition is a messed up mixture burn.... when the spark ignites the mixture the burning process should be smooth and progressive and normally occurs at around 10 degrees after TDC.
If the petrol doesn't burn evenly and completely the "flame front" doesn't propagate smoothly and pressure variations can occur.
Higher octane petrol have additives to make them burn more slowly, evenly, and completely.
Rule of thumb for 95 octane fuel is 9.5:1 with cast iron heads and 10:1 with aluminium heads this is because heat plays a role in pre-ignition and aluminium dissipates heat better than cast iron. But it is all dependant on the shape of the heads, spark plug placement etc.
Also smaller displacement engines, like a 1.8 litre 4 cyl, 16 valve DOHC rice burner can run a higher CR because combustion chamber volume and bore diameter are also variables in the burn rate. (smaller is better)
Okay with all that said I cant imagine that fuel is the cause, even if it is the higher compression 9.35:1 V8, as its still pretty low compression in the scheme of things. I used to run 10:1 in my first motor i built 20 years ago which was a Chrysler 360 cu in with cast iron heads.
The question to be asking is what causes engine pre-ignition?
Low octane fuel with high engine compression.
Too much ignition advance due to ignition timing or valve timing.
Engine is overheating. (dont believe the temp gauge in the D2 it is useless)
Mixtures becoming too lean, check MAF
Carbon build up. (Unlikely on an EFI motor with modern fuels)
Knock sensor.
So my gut feeling would be:
Replace the MAF sensor, even if it isn't the cause you will need to replace it at some stage anyway.
Failing or improperly torqued knock sensor can cause the sensor to not function correctly resulting in the timing to be to far advanced. I haven't heard of this being an issue on the D2 though?
Overheating? I notice in the first post you said you have had the heads done, head gasket issue often is due to heat? I was speaking to a LR mechanic recently who was saying that almost all the radiators in the D2 that come into his workshop are half blocked he actually keeps change overs in stock now. Worth checking the radiator and thermostat in my opinion the D2 V8 really doesn't like heat. Also i read somewhere the D2 temp gauge is computer controlled and has no real reality on the real water temp, also stories of the motor boiling yet the gauge is still on normal.