K2 GTi
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Registered: 21st Oct 04
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quote:
Originally posted by Dave
So he did another run with 95ron to compare then?
Yes, came out the same 
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Brett
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Registered: 16th Dec 02
Location: Manchester
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Is it not supposed to be mapped again to take advantage of the higher octane fuel?
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Kyle T
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Registered: 11th Sep 04
Location: Selby, North Yorkshire
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Either a remap or a good few tank fillups for the ECU to adapt, depending on the car ofc.
Lotus Elise 111R
Impreza WRX STi
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Brett
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Registered: 16th Dec 02
Location: Manchester
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So why don't jap cars 'adapt' to the lesser octane fuel when standard? Why does it still state to fill with higher octane? Is it a one way thing? Also why would it take a few tank fill ups? It'd either be registered as higher octane or it won't? Not understanding why it takes a few tank fillups to realise what's going on. That'd mean if you reverted back to the lower octane it'd take a few fillups again to realise, in which case it wouldn't be running right and potentially go pop? All sounds a bit internet.
[Edited on 23-04-2013 by Brett]
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Tom G
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Registered: 4th Aug 08
Location: Cheshire
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quote:
Originally posted by Brett
So why don't jap cars 'adapt' to the lesser octane fuel when standard? Why does it still state to fill with higher octane? Is it a one way thing? Also why would it take a few tank fill ups? It'd either be registered as higher octane or it won't? Not understanding why it takes a few tank fillups to realise what's going on. That'd mean if you reverted back to the lower octane it'd take a few fillups again to realise, in which case it wouldn't be running right and potentially go pop? All sounds a bit internet.
 I thought exactly the same thing when Kyle posted it a few pages back.
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Brett
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Registered: 16th Dec 02
Location: Manchester
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My questions weren't necessarily aimed at Kyle, more to anyone who can help educate me on this strange topic. Conflicting information scattered around the internet. I feel like on the most part for people with regular cars not mapped to higher octane fuel, it's simply a placebo effect.
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SXI - Matt
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Registered: 8th Jul 07
Location: Leicestershire Drives: Corsa C SRI
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quote:
Originally posted by K2 GTi
quote:
Originally posted by Dave
So he did another run with 95ron to compare then?
Yes, came out the same
Just to throw a spanner in the works it would impossible to say it did nothing as no 2 rolling road results are never the same so even if he did do another few runs on a different tank of fuel the same day which would be a massive ball ache, it would be pointless as it would be different compared to the previous one any way. And minimal gains you'd get from the fuel if any would be lost in tolerances any way.
Surely if people want more power go get a remap or bolt a big turbo on your car, I always thought and was told when I opened a Tesco fuel site that sold momentum not long after it was released it was designed to last longer and run smoother not make more BHP.
Surely that goes the same for any other posh petrol to
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baza31
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Registered: 19th Apr 03
Location: yorkshire
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quote:
Originally posted by mwg
I'm expecting my car to do a wheelie when I fill up with it after work
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
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quote:
Originally posted by Brett
So why don't jap cars 'adapt' to the lesser octane fuel when standard? Why does it still state to fill with higher octane? Is it a one way thing? Also why would it take a few tank fill ups? It'd either be registered as higher octane or it won't? Not understanding why it takes a few tank fillups to realise what's going on. That'd mean if you reverted back to the lower octane it'd take a few fillups again to realise, in which case it wouldn't be running right and potentially go pop? All sounds a bit internet.
[Edited on 23-04-2013 by Brett]
Exactly, an ecu performs upwards of 2 million calculations per second.
There is no way in the world it takes any length of time to adapt to different fuel.
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BarnshaW
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Registered: 25th Oct 06
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I would be very suprised if a car did not make more power on 99 ron over 95 ron? if it was mapped suitably for them fuels there would be a noticeable power increase on the 99 ron.
thats why most people are getting meth mapped into cars nowadays as essentially its free power, you can get approx 10% extra power by mapping in 20% meth or similar
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ed
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Registered: 10th Sep 03
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I put super unleaded in my car 
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John
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Registered: 30th Jun 03
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Because an ecu can perform X calculations a second doesn't mean it will instantly respond to whatever input, it could very well be programmed to watch for changes over time, or any other combination.
There is a lot of drivel posted about vpower/higher octane fuels though. Especially those who get massive mpg increases.
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Kyle T
Premium Member
Registered: 11th Sep 04
Location: Selby, North Yorkshire
User status: Offline
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quote:
Originally posted by Brett
So why don't jap cars 'adapt' to the lesser octane fuel when standard? Why does it still state to fill with higher octane? Is it a one way thing? Also why would it take a few tank fill ups? It'd either be registered as higher octane or it won't? Not understanding why it takes a few tank fillups to realise what's going on. That'd mean if you reverted back to the lower octane it'd take a few fillups again to realise, in which case it wouldn't be running right and potentially go pop? All sounds a bit internet.
From what I understand, one of the end results of a higher octane fuel is that the point of detonation is more "predictable" and hence the engine can be tuned and timed with less tolerance. Less tolerance normally means more margin for squeezing performance and efficiency.
If you've got an engine mapped for 95RON and you put 99RON in it, you're not going to damage anything - but the noticeable benefits are also going to be limited. The engine is simply running in a sequence which will allow for earlier detonation, which may never happen providing you always run the 99RON.
In for example an Impreza engine, the engine is designed to run to lower tolerances as far as the detonation timing is concerned so higher octane fuel is recommended. A modern ECU can make some allowances for it but the tighter tolerances generally mean that an early detonation (low octane fuel) is going to cause issues. Scoobyclinic were making a coffee table last time I went out of an engine block which had been running low octane fuel, it's quite a sight
I have heard of many people with Impreza's (amongst other performance Jap cars) having their engines mapped for 95RON fuel because of availability issues where they live, which exchanges performance and potentially efficiency for tolerance and reliability.
As for the "multiple tanks to adjust" thing, that's something I had read a while ago on a NA Honda forum which suggested that the ECU was slowly tightening up the detonation tolerances over a window of time. The same engine ECU's had a characteristic of running rather rough and lumpy in the event of a flat battery or reset as the parameters were all "re-learned". Whether there is ANY science in that, I really don't know - but I've read on several occasions from several sources that unless remapping specifically for a certain octane, that ECU adapting can take some time.
Don't mistake me of being a champion of the high-octane movement, it's just something I did a fair bit of research into when buying a Scooby and reading all of the horror stories with engines blowing up due to peasant petrol being used. For the sake of an extra couple of quid on a fillup, I'll continue to use Tesco Momentum 99 on this car - but I'll never stick it in my missus' 1.2 corsa "for a treat" as I seem to read quite often.
[Edited on 23-04-2013 by Kyle T]
Lotus Elise 111R
Impreza WRX STi
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