Fuel & Performance
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MBWorld Fanatic!
Joined: Jul 2005
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From: London, UK
No longer stock '06 E55, A3 3.2 Quattro, GLE 400d, R107 280SL, Golf Polo
Fuel & Performance
Well there was a program here on telly in UK recently about the difference between fuels. Something that would certanly be of interest to us with Forced induction motors ... so here goes ...
Cars:
Renault Clio
Golf GTI (new turbo)
Impreza WRX STI
Fuels:
Normal Unleaded (95 RON)
BP Ultimate Unleaded (97 RON)
Shell Optimax (98 RON)
Mearuring BHP figures on a chassis dynamometer (bolted to the 2 or 4 driven hubs) they found the following....
Renault Clio - gave the same bhp on all 3 fuels (82bhp IIRC)
Golf GTI - Shell gave 5bhp more than UL, BP gave 2bhp more than UL.
WRX STI - Shell gave 15bhp more than UL, BP gave 8bhp more than UL.
Finally they tested the torque figures of the WRX. Shell was 15 Nm(IIRC) ahead of BP, which was a minor increase over normal.
So 98 RON vs 95 RON gave 15bhp difference which in the case of the Subaru worked out to around ~7% increase. What surprised me was the increase in torque which was up around 10% - pretty much across the entire curve (98 vs 95 RON).
Rule of thumb (as if you did not know it) : Put the highest octane you can source in your E55! 7% on 470 bhp is quite a few hp!!!
P.S. for UK drivers Tesco recently launched 99 RON - apparently as good if not better than Optimax but around 10p/litre cheaper!
Rgds Steve.
Cars:
Renault Clio
Golf GTI (new turbo)
Impreza WRX STI
Fuels:
Normal Unleaded (95 RON)
BP Ultimate Unleaded (97 RON)
Shell Optimax (98 RON)
Mearuring BHP figures on a chassis dynamometer (bolted to the 2 or 4 driven hubs) they found the following....
Renault Clio - gave the same bhp on all 3 fuels (82bhp IIRC)
Golf GTI - Shell gave 5bhp more than UL, BP gave 2bhp more than UL.
WRX STI - Shell gave 15bhp more than UL, BP gave 8bhp more than UL.
Finally they tested the torque figures of the WRX. Shell was 15 Nm(IIRC) ahead of BP, which was a minor increase over normal.
So 98 RON vs 95 RON gave 15bhp difference which in the case of the Subaru worked out to around ~7% increase. What surprised me was the increase in torque which was up around 10% - pretty much across the entire curve (98 vs 95 RON).
Rule of thumb (as if you did not know it) : Put the highest octane you can source in your E55! 7% on 470 bhp is quite a few hp!!!
P.S. for UK drivers Tesco recently launched 99 RON - apparently as good if not better than Optimax but around 10p/litre cheaper!
Rgds Steve.
Last edited by stevebez; Nov 18, 2005 at 05:20 AM.
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From: WOT somewhere in the Bay Area
1951 Caterpiller D6
All that is saying is the octane requirement of the Renalt is at or below 95RON and the other two cars are at or above 98RON. You can figure out what is right for your car by filling up a few tanks with a one octane rating and measuring the fuel mileage. Keep doing that for each different octane rating until your mileage reaches its highest. This isn't 100% accurate but very close.
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Joined: Jul 2005
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From: South Florida
2007 S65, 2005 Nissan Armada
I think it makes more of a difference with a turbo car since many of them will allow the boost to go a little higher with higher octane since it takes longer for knock to occur. I don't think on a supercharged car the computer has many options other than timing. Would be interesting to find out though...
Thread Starter
MBWorld Fanatic!
Joined: Jul 2005
Posts: 3,176
Likes: 19
From: London, UK
No longer stock '06 E55, A3 3.2 Quattro, GLE 400d, R107 280SL, Golf Polo
Yes power is the rate of torque delivery ... but what surprised me was an increased torque even low in the rev range... I would have thought the fuel would have most benefits at top end.
On cars where ECU have ability to remap timing to adjust for knocking is where a higher octane fuel helps - timing can be run very advanced without knocking.
Rgds Steve.
On cars where ECU have ability to remap timing to adjust for knocking is where a higher octane fuel helps - timing can be run very advanced without knocking.
Rgds Steve.
MBWorld Fanatic!
Joined: Mar 2003
Posts: 3,445
Likes: 3
From: WOT somewhere in the Bay Area
1951 Caterpiller D6
Originally Posted by pas
I think it makes more of a difference with a turbo car since many of them will allow the boost to go a little higher with higher octane since it takes longer for knock to occur. I don't think on a supercharged car the computer has many options other than timing. Would be interesting to find out though...
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MBWorld Fanatic!
Joined: Mar 2003
Posts: 3,445
Likes: 3
From: WOT somewhere in the Bay Area
1951 Caterpiller D6
Originally Posted by stevebez
Yes power is the rate of torque delivery ... but what surprised me was an increased torque even low in the rev range... I would have thought the fuel would have most benefits at top end.
On cars where ECU have ability to remap timing to adjust for knocking is where a higher octane fuel helps - timing can be run very advanced without knocking.
Rgds Steve.
On cars where ECU have ability to remap timing to adjust for knocking is where a higher octane fuel helps - timing can be run very advanced without knocking.
Rgds Steve.
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