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Old 16-03-2007, 10:48 AM   #1
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high octane and optis

has anyone tried running optimax engines on shell vmax or bps equivelant. iv got a 200 opti would it damage the engine etc? thanks Andy
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Old 18-03-2007, 09:12 PM   #2
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It won't make the slightest bit of difference.
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Old 18-03-2007, 10:09 PM   #3
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has anyone tried running optimax engines on shell vmax or bps equivelant. iv got a 200 opti would it damage the engine etc? thanks Andy
Worried that you're not spending enough on petrol?
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Old 19-03-2007, 07:36 PM   #4
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has anyone tried running optimax engines on shell vmax or bps equivelant. iv got a 200 opti would it damage the engine etc? thanks Andy
Without pulling the mapping from the ECU it's difficult to say, but judging from the fact these engines are designed for the world market (i.e. designed to run on fuel as poor as 90RON) I'd say you'll be likely to make slightly less power due to the engine being optimized for 90RON.

It would, however, be possible to acheive more power from the engine if you were able to re-map the fuelling and ignition to suit Shell V-power.
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Old 19-03-2007, 08:32 PM   #5
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Wouldn't this mean that you would be stuck with only running the engine only on high octane fuel?
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Old 19-03-2007, 09:06 PM   #6
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Wouldn't this mean that you would be stuck with only running the engine only on high octane fuel?
Correct, but it depends what you want to acheive. Power at the sake of cost or cost at the sake of power. As with everything, it's a trade-off for best compromise.

Bearing in mind that standard UL fuel in the UK is 95RON, you're already forsaking the poetential power benefits of 5RON. Ideally engines destined for the UK market would be mapped for the lowest octane fuel it's likely to encounter (95RON).
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Old 19-03-2007, 10:25 PM   #7
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New opti XS's are all mapped for 92 Ron or 87 PON (US) - older Optimax XS's and Promax's were mapped for 98 RON or 92 PON (US)
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Old 20-03-2007, 01:52 AM   #8
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Actually both V-power and Ultimate do better than 'normal' petrol, about 2% more HP. If you want to get silly, Ultimate 102 will give you about 5% more power with the same mapping, and if you change the mapping to suit, around 12% more power.

Ultimate 102 is £2.80 a litre.
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Old 20-03-2007, 09:48 AM   #9
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Is this something you've tested yourself or just read on the 'net somewhere?
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Old 20-03-2007, 11:20 AM   #10
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Without getting into too much depth...

If a gasoline engine is tuned 'correctly' to suit a fuel of 95RON and it it operating within normal parameters, it will make no more power when used with gasoline of 98 or 99RON UNLESS the new fuel has a higher calorific value.

The problem often comes with how the fuel manufacturer has obtained the higher RON rating, has it been acheived by better refinement (costly) or has it been obtained by additives (cheaper) - Tesco for example are rumoured to have acheived their 99RON fuel by means of the addition of etahnol - This additive, while increasing the RON will have the side effect of reducing the calorific value thus decreasing the power acheiveable for a given amount of fuel although increasing the power acheiveable from ignition advance and/or boost.

IF any of the fuels in question have a higher calorific value then yes, they will deliver more power for a given tune over a lower octane providing the engine is within it's operating limits and there are no adverse outside factors BUT to put an across-the-board %age on it is totally unrealistic.

I seem to remember a test some years ago finding that the only 'high street' fuel with both a higher RON and calorific value was Esso Supreme.
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Old 20-03-2007, 12:48 PM   #11
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Tested in a pressure cortrolled and air conditioned Dyno room. ( you can get about 3% different readings with exactly the same setup and fuel if the weather changes!! )

Shell V Power is more refined and has less crap in it. It is a clearer fuel and burns better. ie it has more bang for the money.( calorific value ) Its octane is from refinement and this does translate directly into more power without any alteration to the engine. Obviously if you do tune the engine to the fuel you get more bang again. Ultimate is similar, but not as good as V-Power.

Ultimate 102 is a completely different animal - it is completely clear - like water. It has zero polutants like benzine etc, and has 2.7% oxygenates as part of its blend. It is a blended fuel, not a refined fuel. They refine the constituent parts of the fuel and mix them together to get what they want.

The oxygenates they have added is like adding a small amount of nitros oxide to the engine. It burns better because it has more oxygen in the mix, and it additionally is a cleaner fuel with a higher calory level than V-power. 102 is brilliant in turbo engines or high revving engines which are tuned for the fuel. 102 is legal pump fuel and meets the BS satndard for pump fuel for use on the road, meets the FIA race regulations as pump fuel and as it is dispensed at public forecourts at petrol stations around the country ( 18 of them! ) it qualifies as a generally avalable pump fuel by the RYA definitions...

102 does actually clean up deposits in an engine, left by other fuels. 102 does provide a 5% measurable increase in power to a low revving engine with no alteration to any other components, and if you play with the mapping, or if you have a high revving engine or a turbo charged engine you will double that more.
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Old 20-03-2007, 01:16 PM   #12
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Knock sensors?
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Old 20-03-2007, 01:31 PM   #13
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Excellent discussion

I would be interested to know what engine you performed your tests with and where you got the blending data for the fuel? I did try quite hard to get some proper technical data regarding composition of the afore-mentioned fuels but to no avail.

Re; knock sensors - are normally found on forced induction engines. If the engine is already running on fuel insufficient for it's mapping and suffering knock, the ECU (if capable) will retard timing and/or increase fuelling, decrease boost in an attempt to stop the knock within the parameters of it's fail-safe mapping. You are obviously losing power at this point.
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Old 20-03-2007, 01:44 PM   #14
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These days I think most petrol engines have them. I was under the impression that the engine management would advance the ignition timing as much as it could before detecting knock?
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Old 20-03-2007, 01:55 PM   #15
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These days I think most petrol engines have them. I was under the impression that the engine management would advance the ignition timing as much as it could before detecting knock?
Not on any management systems I've ever worked with. The problem is that you'll always be bouncing off the knock threshold, eventually this will cause damage to your engine. A map should be developed so that it encounters no knock at all even in the worst conditions it's likely to encounter. On modern engine management systems there are many maps controlling various parameters depending on operating conditions. The purpose of the knock sensor is to signal the ECU to operate at safer known settings on the onset of knock.
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Old 20-03-2007, 03:12 PM   #16
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Not on any management systems I've ever worked with. The problem is that you'll always be bouncing off the knock threshold, eventually this will cause damage to your engine. A map should be developed so that it encounters no knock at all even in the worst conditions it's likely to encounter.
This is true.

The sensor is there just in case of a very tiny possibility of poor fuel, not as a general rule.

I have the blending specifications for 102 if you are interested. I should also have the specification of V-Power but as it is a refined fuel with additives to bring it to their defined standard, and not a pure blended fuel, the specs change regularly.
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Old 20-03-2007, 03:18 PM   #17
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This is true.

The sensor is there just in case of a very tiny possibility of poor fuel, not as a general rule.

I have the blending specifications for 102 if you are interested. I should also have the specification of V-Power but as it is a refined fuel with additives to bring it to their defined standard, and not a pure blended fuel, the specs change regularly.
Yes please, would be very interested to see that data. Presumably there is a defined permitted tolerance for the V-Power variance?
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Old 20-03-2007, 11:26 PM   #18
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theres alot more to this than i first thought. its very interesting to see the difference in refinment etc. we use shell vmax on the racing car and had some left over in the cans we use for the rib (started using them over the winter) and now the seasons started i was thinkng about just using what i had in the cans in the rib as a test.
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