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Old 31-10-2009, 03:47 PM   #21
70NYD
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so twin cams aid comrpession?? fascinating...
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Old 31-10-2009, 03:51 PM   #22
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so twin cams aid comrpession?? fascinating...
70, will you lay off the technical stuff. 91 octane does not burn as efficiently as 98/100. I agree it may not be crucial to use better fuels on lowr comp engines but, get the best is always a sensible notion to me

I get better mileage from higher octane that simple. May not be much but either is 4c docket

back to the question........I wouldn't bother using an additive. Just a con!
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Old 31-10-2009, 04:03 PM   #23
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Originally Posted by BADMIXY View Post
70, will you lay off the technical stuff.
Just cause you don't understand it? Twin Cam has nothing to do with higher comp and pinging. SOHC engine with high comp pistons can ping just as easily, but you'd never notice as most people would throw the SOHC out before modifying it.

I run 98/95 and never use 91. Get 50-75km more to a tank on 98 and it idles, starts and runs much smoother. Plus I advanced the timing when i fixed it a couple of weeks ago, cant go back now
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Old 31-10-2009, 04:05 PM   #24
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I run 98/95 and never use 91. Get 50-75km more to a tank on 98 and it idles, starts and runs much smoother. Plus I advanced the timing when i fixed it a couple of weeks ago, cant go back now
^^^^^^^^^^^^^^^^^^^^ really what I was stating if you bothered to read properly. The twin-cam was simply an example So, guess we totally agree for once

unwitingly (you need wit) you just shot your mates down in flames
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Old 31-10-2009, 05:23 PM   #25
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yes watch me burn.... lol
what i was saying before
we dont have 91 in qld that i have seen (only 91E10 energy 31MJ)
pure gasoline has a energy rating of 32MJ.. octane rating does not relate at all to the gasolines energy rating..
however being able to compress it further without self ignition (knock) you can get more power out of it. this is shown in a pressure volume diagram for a otto cycle (PV as per what i said before)
the area within the PV loop is the energy extracted per cycle.
most simplified PV diagrams are idealised to the point of not showing the intake and exhaust cycle, its shown as one step and this is where new energy is imputed to the system
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Old 31-10-2009, 05:27 PM   #26
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we still got 91 down here.....wish they'd can it funny how even my 4 stroke mower goes better on high octane. That's not a smart comment either, it's true! & I can't see it being race-tuned lol
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Old 31-10-2009, 11:42 PM   #27
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may just use one to clean the injectors. getting the whole kitten kaboodle reworked, new fuel filter etc.

our bloody prices on normal unleaded are 126 cents a litre at the moment while premium is almost even with victoria at 134, last time i checked vic that is.
checked cause i'll be cruising around in melbourne in two days!
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Old 01-11-2009, 07:52 AM   #28
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I don't know much about fuel, but when I had a car that used 91ron, it ran better on 95ron, but often times 98/100ron wouldn't make that much of a difference, so the 95ron was a good trade off. With the Mazda2 I found that E10 [dunno what octane] wouldn't give me the economy that even 91ron would. Once again, 95ron was a good trade off.

My tastes in fuel are:
95ron: Caltex Vortex95
98/100ron: Shell V-Power [sometimes Vortex98]

This opinion is derived from driving interstate, driving in traffic, touge, you name it. A lot of ppl like BP Ultimate [98ron?], but I found it made my SP18 lose a lot of power. However, the 95ron BP fuel seemed to be much of a muchness compared to the other brands, but I have more Caltex servo's around me. Both my cars really need Shell V-Power now, so I would only put 95ron in and poosay foot it if I was caught out and desperately needed fuel...

Gav.
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Old 01-11-2009, 08:03 AM   #29
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i wouldn't worry about fuel additives. use 95ron or wind the timing forward a few degrees and 98ron fuels.
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Old 01-11-2009, 11:26 AM   #30
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alrighty
just want a good cleanout
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Old 02-11-2009, 12:04 AM   #31
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So is VPower the best? I use Vpower once in a blue moon because it just looks so convincing lol
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Old 02-11-2009, 06:34 AM   #32
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yep, I get great power/economy from using either Shell/BP 98/100

Others will profess that 95 is adequate. They're right! I just personally like the higher octane cleaner fuels
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Old 02-11-2009, 07:30 AM   #33
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It's engine dependant. The BAs BP from experience will take advantage of the higher octane while the Demio has no effect what so ever.
Take a survey of your fuel usage over 5-6 consecutive tanks of 91, 95, 98 and maybe E10. Note:
  1. Type of fuel
  2. Amount of fuel (litres)
  3. Price of all fuels (for comparison)
Once you have enough data you can work out your average fuel usage on different types of fuel and cost per 100km for each.
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Old 02-11-2009, 10:57 AM   #34
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+1 for what Cosmo said.

Since there are so many variables it's hard to know what will make a difference and why, and whether any perceived gains outweigh the additional cost of premium petrol. Also, keep in mind that the ECU needs to adjust between different batches of petrol let alone different types, so it helps to get petrol from the same station each time. Also an engine that has had a recent oil change will typically run more efficiently than one that is in need.

I have tried 91, 95 and E10, but not 98. From what I've seen in my SP:
  • E10 made my car run like a dog, with less power and lower economy. The lower price of E10 did not justify the drop in performance, although it was useful in cleaning it up and getting rid of water after a really bad batch of petrol;
  • 95 felt better than 91. It felt like there was more power when I put my foot down, and I went roughly 20kms further on the same sized tank with similar driving style. My timing has been advanced 3 degrees, which might have something to do with it.
  • 91 gave the best economy for the price. That is, although it didn't take me as far as 95, the difference in price was so great that 91 represented the best value in the long term. Note that my car doesn't ping without using premium despite advanced timing.
Unfortunately though I didn't write down any hard data. Does anyone know the likely effects of my engine having had the timing advanced by three degrees (by the previous owner), and the implications on the differences I saw?
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Old 02-11-2009, 12:45 PM   #35
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You're running 91 with advanced timing?
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Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall, torque is how far you take the wall with you.

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Old 02-11-2009, 01:15 PM   #36
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I haven't checked the timing to see what it is, but yeah I was reading through the previous owner's receipts a little while ago and found out that at one point the timing was advanced, and I couldn't find anything to say it was put back. No detonation though so I can't see why using 91 would be an issue.
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Old 02-11-2009, 01:51 PM   #37
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I can't remember where i heard it but apparently at some stage in the future the standard fuel here will be 95RON.

Don't quote me on it.
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Old 03-11-2009, 03:27 PM   #38
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oddly enough, after i run a tank of 95 (mobil 6000) then put normal 91RON (non e10) in, i seem to get maybe 40km extra out of it.. then again, i drive like a granny most of the time.
as for fuel additive - i got a dodgy partial tank of shell 91 that ****ted me with sloppy starts and rough idels so i got nulon pro strength fuel system cleaner - u might have to get a mechanic to supply it but if u have a Mr Filter shop around, get it from them. its same price as the retail/consumer grade stuff but who knows what the difference is? *shrugs*
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Old 03-11-2009, 04:04 PM   #39
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Quote:
Originally Posted by mussing View Post
Note that my car doesn't ping without using premium despite advanced timing.[/LIST]
that's amazing no, really




Quote:
Originally Posted by RibZe View Post
I can't remember where i heard it but apparently at some stage in the future the standard fuel here will be 95RON.

Don't quote me on it.
GOOD

Quote:
Originally Posted by juld0zer View Post
oddly enough, after i run a tank of 95 (mobil 6000) then put normal 91RON (non e10) in, i seem to get maybe 40km extra out of it..
^^ no, you won't get better mileage from a lower actane fuel, period!
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Old 03-11-2009, 04:28 PM   #40
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milage/performance/economy is related not just to the octane rating but also to the energy content.. eg LPG 110RON while ultimate/premium has 98-100RON (3 times the price difference but) but LPG energy is 26 MJ/L while petrol 32MJ/L (THIS IS THE MAIN DIFFERENCE IN FUEL CONSUMPTION UNDER SIMILAR CONDITIONS)

ONLY THING THAT OCTANE DOES IS ALLOW FOR THE FUEL TO BE COMPRESSED/PREHEATED FURTHER PRIOR TO SELF IGNITION. combine this with advance in timing (or diff doming in pistons/higher boost) and you get more energy out of the system.
they put effective octane boosters in to gearoils that are under enormus pressures and heats (to raise the flashpoint and prevent the machine from exploding..)

this is the same point i was making before.. get off your placebo horse

edit
sorry bout the caps i didnt notice..
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