Discussion
Unleaded 91 octane or higher is fine for the standard CV8 (as per the manual) but if it's in a higher state of tune then it may need Super....depends on whether it's detonating or not. They are quite a low compression engine compared to rice burners..as the V8 has the cubes and the cylinders.
Usually optimax. There does seem to be a significant increase in performance with 100LL Avgas, 100+ octane with a nice shot of lead ! (I have no cats!) It even smells like real petrol, not the paint thinner you get from the pumps. Anyone else tried it? would be interesting to do some dyno tests on the stuff.
Previous owner of my CV8 had a Wortec Focus Pac fitted & it was tuned for 98RON Super Unleaded. It runs a treat & is definately the best for the car, however not every garage sells it so I carry a bottle of Millers Octane Booster up 95 to 97/98. Difference is un-noticable!
Which is a nice link to:- cost of full tank of 98RON v full tank of 95RON + 1 bottle of Millers Octane booster. Cheaper? Harming the engine? Not good?
Which is a nice link to:- cost of full tank of 98RON v full tank of 95RON + 1 bottle of Millers Octane booster. Cheaper? Harming the engine? Not good?
Edited by Paul.H. on Thursday 8th June 09:19
I use BP Ultimate plus Millers CVL, one bottle per 20 litres (no cats). It increases octane by up to 3, ie 98 Ultimate to 101. The difference can not only be felt, but the cost of the octane booster is offset by better mpg! I get an average 22.4 mpg without, 26+ with (cruising). I have tested octane boosters on 2 engines on an Engine Dyno (not Rolling Rip Off!) and found Millers worked, the 'others' made much smaller gains, and better than all 'exotic' fuels I tried. As it is the only FIA approved product I guess that tells a tale too? There is a version that can be used with cats but CVL is OK for track days on cat equipped cars........I use it in 2 others and no problem to date.
Optimax has caused me problems as allegedly it 'goes off' if the supplying garage does not have a fast turnover of it, ie it sits in their tanks too long, and found reduced performance on 3 occasions after not running a car for up to 3 weeks with it too. Told by a reliable Tuner they have experienced batch problems with it after trying everything to set up a Monaro on Optimax only to find it was bad fuel!
Optimax has caused me problems as allegedly it 'goes off' if the supplying garage does not have a fast turnover of it, ie it sits in their tanks too long, and found reduced performance on 3 occasions after not running a car for up to 3 weeks with it too. Told by a reliable Tuner they have experienced batch problems with it after trying everything to set up a Monaro on Optimax only to find it was bad fuel!
Edited by Paul-C on Thursday 8th June 13:11
v8d said:
Usually optimax. There does seem to be a significant increase in performance with 100LL Avgas, 100+ octane with a nice shot of lead ! (I have no cats!) It even smells like real petrol, not the paint thinner you get from the pumps. Anyone else tried it? would be interesting to do some dyno tests on the stuff.
Wouldn't the lead affect your Lambda sensor?
Hi,
vauxhall plus the handbook says "premium unleaded" so I'm not sure if I should use normal or super for my 6.0VXR.
Wortec did the ecu remap and catback exhaust however I have not been advised to make sure SUL/optimax is used only!?.
I would like to know the best option as I dont want to damage anything!
Regards,
Mike
vauxhall plus the handbook says "premium unleaded" so I'm not sure if I should use normal or super for my 6.0VXR.
Wortec did the ecu remap and catback exhaust however I have not been advised to make sure SUL/optimax is used only!?.
I would like to know the best option as I dont want to damage anything!
Regards,
Mike
maverick964_uk said:
Hi,
vauxhall plus the handbook says "premium unleaded" so I'm not sure if I should use normal or super for my 6.0VXR.
Wortec did the ecu remap and catback exhaust however I have not been advised to make sure SUL/optimax is used only!?.
I would like to know the best option as I dont want to damage anything!
Regards,
Mike
vauxhall plus the handbook says "premium unleaded" so I'm not sure if I should use normal or super for my 6.0VXR.
Wortec did the ecu remap and catback exhaust however I have not been advised to make sure SUL/optimax is used only!?.
I would like to know the best option as I dont want to damage anything!
Regards,
Mike
I'm sure 95 would be ok. In NZ you only get 91 or 96 octane so there are HSV's (and Ferrari's etc) running on no more than 96. The manual for the CV8 says "91 octane is sufficent".
But if your really not confident then just run 98 (or keep an ear out for it "knocking"
After my ecu re-map and catback, Greens told me that either fuel is OK as the car drops back to another map for the lower fuel and then steps back up (after a few tanks) for the high(er) octane fuel. The only difference being a drop in BHP with the lower octane fuel.
No damage will be done.
No damage will be done.
Optimax for me every time too, Tesco 99 in my experience does not offer more power over optislurp plus I get worse economy with it, don't like BP Ultimate, use Esso 97 ron or Texaco 98 Ron if no slurp around. Been warned about additives too many times, mind you that is what the fuel companies do I suppose. Good point about petrol going off, need to use a garage that has a busy forecourt to ensure fresh supplies.
Hmm, I think you will find the low octane table is only used when knock is detected. Once you power cycle you start on the high octane table again unless you have a maf or similar failure which drops you permanently into the low octane table.
However that said lower octane fuels contain more energy and burn faster, if your engine is tuned for them and has good spark timing there is zero point in running a higher octane.
Higher octane is useful in obtaining good spark timing with higer compression engines as it is less likely to spontaneously combust and is somewhat more controlable even though it burns with a little less energy. The benefits of increased efficiency from higher compression outweigh the power loss from the fuel.
I think untuned engines are fine with 95, LS2 and tuned (for 98 octane) engines are better off with 98 obviously.
You can retard spark timing to prevent knock in higher compression engines but eventually you end up with the charge still being burnt closer to BDC of piston power stroke well after the best work is done (~14 ATDC). This means hot and burning fuel out the exhaust (not pushing the piston) and lower power. So really ideal spark for NA seems to be anywhere from 22 to 28 deg at WOT.
Sorry if this went over anyones head, just thought it might be interesting to add my 2p.
However that said lower octane fuels contain more energy and burn faster, if your engine is tuned for them and has good spark timing there is zero point in running a higher octane.
Higher octane is useful in obtaining good spark timing with higer compression engines as it is less likely to spontaneously combust and is somewhat more controlable even though it burns with a little less energy. The benefits of increased efficiency from higher compression outweigh the power loss from the fuel.
I think untuned engines are fine with 95, LS2 and tuned (for 98 octane) engines are better off with 98 obviously.
You can retard spark timing to prevent knock in higher compression engines but eventually you end up with the charge still being burnt closer to BDC of piston power stroke well after the best work is done (~14 ATDC). This means hot and burning fuel out the exhaust (not pushing the piston) and lower power. So really ideal spark for NA seems to be anywhere from 22 to 28 deg at WOT.
Sorry if this went over anyones head, just thought it might be interesting to add my 2p.
ringram said:
Once you power cycle you start on the high octane table again unless you have a maf or similar failure which drops you permanently into the low octane table.
What do you mean by power cycle ? I have monitored my knock learn factor and it takes ages to move back to the high octane table after detecting knock (usually caused by revving the engine on downchanges, but how else can you get it to pop and bang on the overrun
) I have tried filling up the tank etc but the only succesful method I found is to perform a PCM reset.
Paul.H. said:
Forgive my ignorance - I've never had a car with THIS performance before so I haven't actually heard 'knock' - & ringram mentioned retarding the timing - so is 'knock' the same as 'pinking' or am I all at sea with this?
Same as Pinking which also known as detonating, in the long term this can damage the engine. Detonating is when the fuel/air mix ignites too quickly (with higher compression engines) so the higher the octane the better and more efficent the ignition of the fuel/air mix.
V8HSV said:
Optimax for me every time too, Tesco 99 in my experience does not offer more power over optislurp plus I get worse economy with it, don't like BP Ultimate, use Esso 97 ron or Texaco 98 Ron if no slurp around. Been warned about additives too many times, mind you that is what the fuel companies do I suppose. Good point about petrol going off, need to use a garage that has a busy forecourt to ensure fresh supplies.
Just a quick comment........there are additives, which are all a complete rip-off except two brands of injector cleaner and Millers in my experience. I have used, and still use CVL in a number of seriously expensive performance cars, not just Holdens, as learnt it genuinely works with no detremental effect during my racing days. Given the engine rebuild cost on just one example would be circa 100K trust me when I say I would not recommend anything that I have not had (long term) first hand experience of.
Hey alfie, you must have bad gas or a lead foot to stay in adaptive spark for that long. As you say it will come back without any knock or a power cycle/reset/flash of pcm. As long as there is no knock it will recover to high octane. I must admit Ive not tried to time it. Id be too scared to knock it down too much. You can lock it in high octane with manual over-rides if you have the right PCM OS.
Ive also just realised that the adaptive spark does not get learnt/active until map is over 50, or in some cases 60 kpa. This means that and KR on decel wont affect it. I think your popping is more likely caused by the DFCO feature which cuts spark and fuel, this might let a little unburnt mixture out the exhaust at the time.
Ive also just realised that the adaptive spark does not get learnt/active until map is over 50, or in some cases 60 kpa. This means that and KR on decel wont affect it. I think your popping is more likely caused by the DFCO feature which cuts spark and fuel, this might let a little unburnt mixture out the exhaust at the time.
Edited by ringram on Friday 9th June 08:55
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