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len

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  • Member
  • Member For: 22y 6d
  • Location: Canberra

I would say "damage" could be an overstatement. There was no evidence of detonation when using ULP.

But you'd think that an engine after say 100,000 kms that has been run on PULP 99% of the time would be running more effectively than one which hadn't...regardless of whether it's a turbo or not especially considering the extra detergents and such that PULP has. Perhaps a case of more upsides of using PULP than downsides of using ULP.

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Guest esky
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This is a tricky one, as only a dyno run with different fuels will give you a clear and predictable result.

The XR6T has a variable red line. 58000rpm - 62000rpm. If you've got poorer fuel (lower resistance to detonation, eg ULP) and high inlet temperatures, the redline will drop to 58000. If you’re running good fuel and cool inlet temps then you can push it to 6200rpm.

That being said, ULP will not cause damage to your engine. The knock sensor will retard the timing and that's where you get the lower power figure. But for your the ECU to retard the timing, detonation must be sensed by the knock sensor. Detonation, knocking pinging, what ever you call it, is very bad!

Generally speaking, there are four basic components of fuel; octane, flame speed and latent energy.

Octane: The rating of fuels ability to resist detonation.

Flame Speed: The speed at which fuel releases its energy. Peak cylinder pressure should occur around 20° ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure and a waste of energy.

Latent energy: An expression of the potential in the fuel. Diesel has greater latent energy than Petrol. The greater the latent energy the bigger the bang properties.

If your only cruising around than I'd expect ULP to cause no harm. But if you like to put the boot in occasionally, then PULP/Sloptimax is for you.

esky :ermm:

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  • Member For: 22y 1m 16d

Yep, my experience with motorcycles would back esky's explanation 100%.

I am planning most of the time to use 95 octane. Premium Unleaded but not Optimax. The difference in my town is 2 cents for the premium abobe the regular, but about nine cents for Optimax.

I'll take the middle road and buy from a reputable dealer.

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Guest DZ.
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I doubt you're going to get too much benefit in running with 98 RON anyway. The Barra 240 is with it's current compression ratio is designed to run on 95 RON so there's not much point paying the extra for Optimax - I imagine it would be like running 95 RON in a Barra 180 - no difference.

Chris - I drive from the Gold Coast to Dubbo every 3 or so months and there's ample outlets with premium unleaded so you won't have a problem finding a station with premium from Sydney to Melbourne.

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  • Member For: 22y 1m 20d
  • Location: Sydney

Just my 2c... and based on 2500km.

After 1500km (run on Synergy 8000 or Optimax) the car was great. Anyway, after those tanks run out I've been filling up with BP Premium... both my wife and I have been commenting on how the car doesn't pull from standing start like it use to (about 2000km)... anyway we thought it was just the case that we have done a lot of city driving and not putting our foot down. Anyway we have filled the last 2 tanks with Optimax, and holy crap, it now pulls hard, very hard. I found out later that the BP premium is only 95, not 98. Now it's little difference however it adds a hell of a lot to standing start power... maybe it advances the timing more when your foot is flat?? I don't know? Either way it's going to drink Optimax or Synergy 8000 from now on

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Guest DZ.
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:ermm: Hmmm, maybe running 98 RON does have an effect. Perhaps in higher temperatures the ability of 98 RON fuel to resist detonation means that timing doesn't get pulled back whereas if you're using 95RON it does in the heat.
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