Octane rating
- Thread starter RossWA
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stradaman
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Because of a better, cleaner flame, valves stay cleaner, giving more power/torque, and better fuel consumption. Reduces knock, so once map is reset, by removing battery cable, the map will be better, engine, more responsive.
At the recent DMS sessions, I think a lot of variation in the power outputs, could be solely down to fuel used! or, at least it contributed, towards it.
Andy
At the recent DMS sessions, I think a lot of variation in the power outputs, could be solely down to fuel used! or, at least it contributed, towards it.
Andy
stradaman
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When i had my Fiat Coupe 20vt, I ran that on Shell V max, or more then often, Tesco 99. At a RR day, the Tesco 99, gave me several more bhp, over 97 ron petrol. Reason i know this, It was the week before the RR, and there was no Tesco 99, so i filled up with 95 ron. Within a mile or so, the car had a little hiccup, and the response from the car, was worse. As soon as i refilled with Tesco 99, again, the car hiccuped [map reset?], and response was back!
As for the newer Shell V Power, I dont think Shell quote an actual ron rating? But, i know it has a very high detergent content.
Andy.
As for the newer Shell V Power, I dont think Shell quote an actual ron rating? But, i know it has a very high detergent content.
Andy.
Danny
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Do I really need to do a hard reset by removing the negative cable of the battery if I change from 95 to 98? Never heard of this before. I have been running 95 for about 1500 miles and I have just returned to 98.
stradaman
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If you remove Battery cutoff in boot, leave for 30 mins or so, then drive the car hard, the 'Go Pedal' learns your driving style. The high octane fuel, will allow the map to advance more, before any knock is detected. Higher the octane, less chance of knock.
Andy.
Andy.
conaero
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What happens when you zero the ecu by removing the battery cable overnight, is that the ECU goes back in to 'self learn' mode, which it monitors the parameters being given it by the various sensors and also how the car is being driven. If its being driven conservatively, it will set for economy, if its being thrashed, its set for power.
I have no knowledge if the Maserati use this system, but its fun to try!
I have no knowledge if the Maserati use this system, but its fun to try!
rotorheadcase
Junior Member
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This all sounds like a bit of a red herring...
The maximum timing advance on a map must be achieved at the rated fuel, which from memory is 95 RON. The ECU cannot adjust past this hard limit simply because it has a higher octane rating fuel. THe ECU only reacts to fuel octane in a limiting way, ie when the knock sensors tell it that detonation is occurring due to lower octane fuel, by retarding spark timing.
The ECU doesn't know what octane rating the fuel running through the car is, it just knows when the AFR is wrong, through the lambdas or when detonation is occurring, through the knock sensors. It will run the standard map for all fuel types until it gets negative feedback from the knock sensors. Typically detonation will only occur under sustained high loads usually in high ambient temperatures. How many of us subject our cars to repeated full throttle/ full boost for sustained periods except on the track?
I run 98 octane in mine because Perth summer temperatures are quite high and city traffic can drive up under bonnet temperatures significantly. I run 98 in my 911 because the custom chip is optimised for it and runs a more aggressive map.
Just my thoughts...
Neil
The maximum timing advance on a map must be achieved at the rated fuel, which from memory is 95 RON. The ECU cannot adjust past this hard limit simply because it has a higher octane rating fuel. THe ECU only reacts to fuel octane in a limiting way, ie when the knock sensors tell it that detonation is occurring due to lower octane fuel, by retarding spark timing.
The ECU doesn't know what octane rating the fuel running through the car is, it just knows when the AFR is wrong, through the lambdas or when detonation is occurring, through the knock sensors. It will run the standard map for all fuel types until it gets negative feedback from the knock sensors. Typically detonation will only occur under sustained high loads usually in high ambient temperatures. How many of us subject our cars to repeated full throttle/ full boost for sustained periods except on the track?
I run 98 octane in mine because Perth summer temperatures are quite high and city traffic can drive up under bonnet temperatures significantly. I run 98 in my 911 because the custom chip is optimised for it and runs a more aggressive map.
Just my thoughts...
Neil
davy83
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Hi Neil, not sure its that simple. I think the reason there are knock sensors is not just to cover low octane fuel, I think the ECU has an optimistic map of what ignition advance the engine will operate with and the knock sensors are used to map out the areas where the engine starts pinking, so it gradually develops an ignition advance map which gets as much power as its possible to get out of the engine. So i suspect if you reset the map and then run higher octane fuel you might get a little more, but it will be so small it is to all practical purposes unnoticeable. I don't think this is limited by 95 RON fuel. I suspect the time this would most noticed would be if you have run with poor quality fuel for a while and the timing map had been retarded a lot because of pinking, a reset and some good fuel would then show improvement.
stradaman
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OK, you need to have a high compression ratio, to achieve results. The more octane, the more it can be compressed into the cylinders, then more power/torque.
4200 engine is high, at 11.1:1, so it benefits. Also, turbo engines have a high dynamic CR too, so benefit as well. But you little shopping car, will not.
I ran my Fiat Coupe on a RR with 95 ron, then again later, with 99 ron, and it made 11 bhp, and 17 Lb ft torque extra!
Watch this video, interesting.
http://www.youtube.com/watch?v=Ospimy_4j9k
Andy.
4200 engine is high, at 11.1:1, so it benefits. Also, turbo engines have a high dynamic CR too, so benefit as well. But you little shopping car, will not.
I ran my Fiat Coupe on a RR with 95 ron, then again later, with 99 ron, and it made 11 bhp, and 17 Lb ft torque extra!
Watch this video, interesting.
http://www.youtube.com/watch?v=Ospimy_4j9k
Andy.
zagatoes30
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Apologies for reviving an old thread but given the imminent trip to Le Mans I though I would just check the acquired knowledge of the forum.
I always use Super Unleaded in the Spyder, preferably Shell if I can get it and never BP unless it is all that is available (long story). Past experience of our cross channel friends is that fuel availability is a bit hit and miss. The services always have a selection but in the towns you can't guarantee what you find, I sometimes also think that what the pump says and what it delivers is sometimes different as well, I say this because my Q4 only runs smoothly on Super unleaded and runs best on Shell. In France a few years ago I filled it from a super unleaded pump and it ran like a bag of spanners.
So two questions:-
1. What should the 4200 use?
2. What do you guys use?
I always use Super Unleaded in the Spyder, preferably Shell if I can get it and never BP unless it is all that is available (long story). Past experience of our cross channel friends is that fuel availability is a bit hit and miss. The services always have a selection but in the towns you can't guarantee what you find, I sometimes also think that what the pump says and what it delivers is sometimes different as well, I say this because my Q4 only runs smoothly on Super unleaded and runs best on Shell. In France a few years ago I filled it from a super unleaded pump and it ran like a bag of spanners.
So two questions:-
1. What should the 4200 use?
2. What do you guys use?
