High octane fuel and the truth

[Drewie]

Talking about the LS1 engines, as has been mentioned before they have 2 fuel/spark tables, a high and a low, from what I can gather on the VT/VX the higher table is tuned for 91 RON fuel but if the knock sensors detect pinking (the LS1 runs 10:1 CR) the computer pulls timing and the lower table is used, thus performance drops, so I gather then that by running the 95 or 98 fuels it would more than likely mean there would be no knock and thus the computer would keep the timing in the upper table. Meaning it should run better. I may be wrong but that is my understanding of how the dual tables work on the V8. Plus supposedly it is meant to keep fuel system cleaner and less deposits... I have always run my VX SS on premium and it runs faultlessly. I think the later V8's can take more advantage of the higher octane fuels.

 

[thewheeldeal com au]

An anecdote of my own..

2006 Jeep TJ Wrangler Inline 6cyl 4.0L (Old school push rod motor from the early nineties Jeep Cherokee/Wrangler - nothing technical or fancy at all, just reliable)

All just regular around town driving
10-15 tanks of regular unleaded: 16.6L/100km (Average)
5 tanks of super premium Mobil 8000 (i think thats what they call it): 17.3L/100km (Average)
5 tanks of regular unleaded: 16.7L/100km (Average)

Proof enough to me that premium did SFA performance or efficiency wise in this particular application.

Now, had I had some fancy modern VVti, V-tec, SiDi motor, I'm sure the results would be different.

 

[peckzz]

all they done to cop cars was put different springs in them, a bigger alternator as they were parked idling with lights at long periods of times, different tyres and a lower diff ratio lsd

also with this fuel thing, i had a old magna 4 cylinder 2.6 litre, and it wouldnt pull a burnout unless it was running 98 premium, so explain that 1?

 

[Robbo VS3]

also with this fuel thing, i had a old magna 4 cylinder 2.6 litre, and it wouldnt pull a burnout unless it was running 98 premium, so explain that 1?

Hahaha..!! :rofl2:

 

[kane88]

also with this fuel thing, i had a old magna 4 cylinder 2.6 litre, and it wouldnt pull a burnout full stop.

Fixed that one up for ya mate :thumbsup:

 

[Robbo VS3]

Who said anything about more fuel?
Dude, do you even know what an octane rating is?


Heaps of people are talking about a 'tune', whatever that is. If you are talking about eeprom/ECU programming, then you should know that you can't change the compression ratio of the engine this way.

Remember, a higher compression ratio is the only reason that you would ever need to change from regular fuel to premium...no other reason. A tune will change how much fuel is injected, when it's injected and a host of other changes to increase performance, but it won't need premium fuel to do it. The power increase comes from the fuel and ignition mapping changes, not the fuel octane rating.

I should have expected the sheep on this forum to trash my thread just because they don't like what I'm talking about. That's fine, but tell me why so we can all learn instead of just calling bullshit. Go and do some reading on what a knock sensor does, and why it does it.

guess my engine tuner is wrong when he said its tuned for premium.

so the rules of higher octane and tuning is all wrong. i think the OP needs to walk into a good tuners workshop and tell them this.

Think they will show you hundreds of dyno charts to prove otherwise.

Also the LS1's have from factory in the standard tune low octane and high octane fuel maps. Therefore i beleive high octane fuel makes a difference.

plus i never beleive whats written in book.

Im still a little unsure about this. I also just got a tuned performance memcal for my V6 Ute, and my tuner also told me it would run at its best on premium fuel either 95 or 98 RON. So from what i have read here so far, that must be bullshit??? I have been using 91RON since i have had the chip and it is running fine, i don't want to spend the extra on premium fuel if it WON'T make any difference performance/fuel economy wise. Apparantly premium has special cleaning detergents in it to clean the engine, so that might be one good thing about it.
Apart from a CAI and the new memcal, my engine is stock. So will premium fuel give me any benefits at all with my tune, or is it true that i would need a higher compression ratio to gain any benefits?

 

[Grennan]

Hmm, i guess I am only imagining the 91 pinging its head off and not wanting to rev over 4k rpm without playing up. Damn that no difference premium.

guess my engine tuner is wrong when he said its tuned for premium.

so the rules of higher octane and tuning is all wrong. i think the OP needs to walk into a good tuners workshop and tell them this.

Think they will show you hundreds of dyno charts to prove otherwise.

Also the LS1's have from factory in the standard tune low octane and high octane fuel maps. Therefore i beleive high octane fuel makes a difference.

plus i never beleive whats written in book.

Yeah...look, im with Nanos and minux. I know how much of a slug my car is to drive (post Mafless tune) on 91, it pings its head off and just feels horrible.

 

[marcdon]

I read this forum and thought i would give 91 a go. I have owned my VZ Exec 3.6 auto for 18months and only ever put 95 octane in it...just my choice no other reason. The last four tanks of fuel have been 91 octane from the same servo which gets a fuel delivery every 2-3 days so its always fresh fuel. I dont fill up until im in the red or when it beeps at me. I just checked my fuel average after 350kms and it is sitting on 11.8L/100Km....95 octane was always 10.5L/100Km. I drive my car to and from work everyday in free flowing traffic with speeds averaging 80Km/Hr. Premium fuel is definitely better on fuel economy. my rough guesstimate says that i get extra 60 odd Km out of a tank of premium. only ever used caltex fuel. i figure caltex is the main refinery in sydney so why would they give their best fuel to anyone but Caltex servos.

 

[2DIE]

I use 91 cos my car is crap anyway:computer:

Not worth a extra $20 or whatever every time I go through a tank to me.

 

[Jezza]

with my current car 91 is what its built to run on so thats what i use but when i first got it because it had been sitting for 1 1/2 years i ran it on bp ultimate for about 2 months just to give the fuel system a good clean out after it not being driven for so long. When i used to drive my mums 2004 Subaru Forester she always put 91 in it and when i started driving it more i started filling it up and i used 98 and you do notice a improvement in performance, response and economy compared to 91