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22-07-2009, 01:14 PM | #1 | ||
Resident AFF detailer
Join Date: Dec 2008
Location: Melbourne, VIC
Posts: 3,730
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Just an observation I've picked up on whilst driving around.....
Whilst my engine is stock (ie runs on regular 91RON unleaded), I have usually been running on BP Ultimate......I guess the videos on their site about the cleaning stuff in the petrol got to me....I want to keep my engine clean inside!! Anyways, on the 98RON stuff, when accelerating, I can really feel the difference at 2500rpm when the engine just seems to pick up a lot in the higher rev band, right through to 4000rpm (is this when the stock cam seems to die out?). Just filled it right up last night with the 91RON regular stuff, and the kick at 2500rpm is no longer there, it's more like a constant acceleration with no real noticable improvement at any level...... Does this mean that the car runs better and faster on the 98RON, even if everything is stock?? I don't know all the technical stuff to do with cams, timing and all that stuff......How would some of you more learned guys explain this in laymans terms???
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22-07-2009, 01:41 PM | #2 | ||
Critical Thinker
Join Date: Jan 2005
Location: Adelaide
Posts: 20,374
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Hey Dave,
I believe that when you put the better fuels in, the engine notices it and the ecu advances the timing a little to compensate for the better grade fuel. i.e. Higher RON fuel, the more power you'll get, but only up to the limit of your engine mods. Thats the way I see it, but Im sure someone here will explain it better than me.
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"the greatest trick the devil pulled, is convincing the world he doesn't exist" 2022 Mazda CX5 GTSP Turbo 2018 Hyundai Santa Fe Highlander 1967 XR FALCON 500 Cars previously owned: 2021 Subaru Outback Sport 2018 Subaru XV-S 2012 Subaru Forester X 2007 Subaru Liberty GT 2001 AU2 75th Anniversary Futura 2001 Subaru GX wagon 1991 EB XR8 1977 XC Fairmont 1990 EA S Pak 1984 XE S Pak 1982 ZJ Fairlane 1983 XE Fairmont 1989 EA Falcon 1984 Datsun Bluebird Wagon 1975 Honda Civic |
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22-07-2009, 01:53 PM | #3 | |||
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Posts: 15,524
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Quote:
The ECU follows a timing map, however when it registers detonation via the knock sensor it will retard the timing by a certain amount (4deg I believe) until the detonations stops. After a very short time has passed (literally seconds), it will read direct from the map again. That's also why, as you already mentioned, performance will only increase up to a certain point. I believe that pont is actually 95 with the AU Falcons. IME, 98 fuels have no performance advantage over 95 on AU's with mostly standard and even mildly modified engines. IME 91 has caused very minor detonation and as a consequence slight retardation of timing under heavy load. Particularly in hot weather and when the throttle is snapped open quickly. It's only once you have a cam and increased compression that 98 is an advantage.
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22-07-2009, 03:07 PM | #4 | ||
Flairs - Truckers Delight
Join Date: Aug 2006
Location: Brisbane Northside Likes: Opposite Lock
Posts: 5,731
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orly sox
95 hey that's excellent information.
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23-07-2009, 01:02 AM | #5 | ||
Resident AFF detailer
Join Date: Dec 2008
Location: Melbourne, VIC
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Thanks Sox, great info there!
will have to run this tank of 91 down to empty, then fill her up with 95 and see what happens! Am I right about the stock cam running out of guts around the 4000rpm mark?
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23-07-2009, 08:20 AM | #6 | |||
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Quote:
4000rpm is close to where the inlet manifiold changes from long to short runners, so the timing map is also changing at that point (actually 3800rpm). I'm not sure if the ignition timing is increased or decreased at the 3800rpm. If it's increased it stands to reason that you might experience some power loss if the advance is too much for the 91 fuel. BTW, when this detonation occurs, you should be able to hear a slight rattling noise for a split second (until the ECU has pullled our some timing). If you don't hear anything, then it's possible nothing is happening at all and you might be imagining it.
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23-07-2009, 09:39 PM | #7 | ||
FF.Com.Au Hardcore
Join Date: Feb 2005
Location: Melb north
Posts: 12,025
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engine compressions have a bareing on the fuel type for each engine. low compression engines tolerate cheaper fuels(lower octane) as a rule, the higher the cylander pressure the more the fuel wants to burn faster and explode in the cylander, uncontrolled burning ,exploding fuels becomes ie pinking (or pinging) sending shockwaves through the rotating mass shortening the life of your engine, pistons ,rods,crank bearings etc hence the need for slower burning fuels (higher octane) for higher compression performance engines.
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24-07-2009, 12:07 AM | #8 | ||
Resident AFF detailer
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So....you're saying my engine will actually last longer as well by using higher octane fuel???
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25-07-2009, 07:38 AM | #9 | ||
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how does 95RON ethanol fuel fit into this???
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25-07-2009, 12:30 PM | #10 | ||||
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Quote:
Quote:
But it's a lot cheaper, so the worse economy is offset. I can't say I'm sure of the long term effects, but I doubt it would be a problem.
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25-07-2009, 09:50 PM | #11 | ||
Regular Member
Join Date: Sep 2008
Posts: 56
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Runs BP Ultimate and only that .. AU's run better on Higher RON Fuel
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06-08-2009, 02:52 AM | #12 | ||
Resident AFF detailer
Join Date: Dec 2008
Location: Melbourne, VIC
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**UPDATE**
Last week - ran my tank almost bone dry and filled up on BP 95RON premium unleaded......the 'kick' in acceleration at around 2500rpm was back, everything went nicely......went for a drive out to Yarra Glen over the weekend, felt pretty responsive! Tonight, got home about 12:30 and wasn't tired, so decided to go for a drive around the suburbs to run my tank dry before going back to filling up with BP Utimate (98RON) to see if there was any noticeable difference.......managed to get pulled over by a cop who reckoned one of my headlights was too bright, so I showed him high beam vs low beam and he couldn't say anything..............ANYWAYS... There was definately a difference going fron 95 to 98RON petrol, even the shortish drive from the BP servo to home, I pushed the car and the 'kick' that I could feel is even more pronounced with the 98RON fuel. Have generally been running on it as of late, but definately going to stick to it from now on - will have to give Shell V-Power and the Mobil a go as well, but BP Ultimate is just plain good. Might also try out the 98RON ethanol fuel you can get from United servos....see what the difference is!!!
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06-08-2009, 10:12 AM | #13 | ||
Critical Thinker
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Location: Adelaide
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this is a good little comparison Dave. Im keen to see what you find.
Generally there isnt a massive difference on an NA untuned car between 95 & 98 fuels. But if you can notice a difference, then that is something. Running on the more cleaner refined fuels should give you better economy also.
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"the greatest trick the devil pulled, is convincing the world he doesn't exist" 2022 Mazda CX5 GTSP Turbo 2018 Hyundai Santa Fe Highlander 1967 XR FALCON 500 Cars previously owned: 2021 Subaru Outback Sport 2018 Subaru XV-S 2012 Subaru Forester X 2007 Subaru Liberty GT 2001 AU2 75th Anniversary Futura 2001 Subaru GX wagon 1991 EB XR8 1977 XC Fairmont 1990 EA S Pak 1984 XE S Pak 1982 ZJ Fairlane 1983 XE Fairmont 1989 EA Falcon 1984 Datsun Bluebird Wagon 1975 Honda Civic |
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06-08-2009, 10:25 AM | #14 | ||
Resident AFF detailer
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No worries mate, yeah I'm not saying the difference from 95-98RON was huge, but it was definately there - it felt that little bit more responsive, and the engine just revved out that little bit easier!
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06-08-2009, 01:31 PM | #15 | ||
FF.Com.Au Hardcore
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v-power is miles better than vortex but id still give bp ultimate the edge
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