Ulimate 98 in a n/a ecotec V6 ?

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Ulimate 98 in a n/a ecotec V6 ?

Post by OZ38 »

Been wondering if running my V6 manual Ecotecs on the BP Ulimate 98 octane fuel is actually of any benefit.
I read that high octane fuels burn slower, which is of benefit to the charged intakes of supercharged 6's & turbo'd 6's. I gather that's because of the greater spark advance put into their tuning to get peak cylinder pressures at that sweet spot just after TDC.
But in the case of the humble n/a ecotec V6 would the higher octane fuel be doing any good apart from maybe burning a bit cleaner ?

I read that in a factory forced induction engine (like the GMH Super6) using a little more boost than standard, the peak torque timing will be around 18-22 degrees, while in the naturally aspirated V6 engine converted to forced induction without internal modifications, timing should be well back at around 10 degrees.
Can someone explain to me why that is & what is going on inside the combustion chamber of a top swapped V6 as compared to the Super6 v6 to require that ?

Cheers

Deek
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by vlad01 »

Burn time isn't much different to regular fuel, but certainly does resist knock a LOT more than 91.

Pretty much a must for ecotec NA with stock internals with a good tune, they have very brittle pistons and shatter with any moderate knock. A tuned up ecotec NA really get up and go, certainly puts a stock 5L to shame.

As for cleaning, 98 fuel at least from BP does wonders in keeping the fuel system clean. I have done heaps of comparisons on my own cars in this regard. The worst fuel for ruining the fuel system believe it or not is premium 95. I did a post on it in my build thread and posted pics. There is some form of additive than just trashes the fuel system in matter of few months.

98 is definitely the way to go, I don't use anything less now.

A L67 top swap is like increasing the comp ratio of a normal L67 by a whole number. The pistons in an NA block have a way smaller dish that an L67 one, hence less timing is required to be correctly timed.
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by antus »

Ive noticed in my subaru with 4th gen ez30 flat 6 that 98 seems to go a lot harder. The car timing is set for 95 and im sure it could gain an extra % again with higher comp and i wish i could be more scientific but... i agree with vlad.
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by Dylan »

What sort of timing does a stock ecotec like on 98?
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by ralcool »

Well one of the first things I noticed while comparing different VS manual Bins, was that the low and high octane tables were the same. At least for the stock versions between generations. Its like Holden didn't have the budget to search for further gains. HSV traditionally has a bit more aggression... but emissions limited.

Yes higher octane burns slower, so we advance the timing to compensate & gain. Then the magic happens. Or raise compression instead.. or boost, or lean it somewhat. But if you can't do that... then run the lowest octane your motor will handle.

The variables are endless. Somehow the L67 tune did get different tables and a proper high octane mode. Probably the yanks paid for the telemetry and resulting data. If your ECU can't adjust and hunt for the optimum timing, then don't bother.

Remember, the additives that are used to raise (read as 'slow the burn') octane levels generally aren't/weren't combustible themselves. (Like Lead for instance)

Its a very dark science. Specifically, if it isn't programmed/tuned to benefit then there may just only be the slight cleansing effects of the detergents or solvents added..
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by wozza »

Hi
There is no gains by using 98 in a stock engine...you will see a slight increase in fuel economy but that doesn't offset the extra cost..That said I run bp ultimate in my stock vr because its a better product, 91 is shit fuel and is the equivalent of 87 octane in the US. Whilst its prob a placebo effect my car does appear to run better..Plus it was the only fuel my old modded VK 6 would happily run on so I stuck to it when I got the VR.
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by vlad01 »

I noticed a big difference with a good tune on my VP over using 91 on a good tune. With 91 it was knocking and pulling all the timing and ran worse than with a stock tune. Once 98 went in, boy did it bring it back to life.


We actually saw this on Biggvl's vn wagon when we loaded up the HSV tune on the dyno, power went backwards with more timing than factory. when we made a new tune using timing between HSV values and stock the power went up over stock. So what was happening is that knock retard was coming into effect with HSV tune on 91 fuel, ending up with less timing than stock and knock itself reduces power too.

Its not so much gains in the fuel itself, but gains by allowing you to actually reach MBT without knock, pretty much impossible with the quality of 91.
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by OZ38 »

vlad01 wrote: The pistons in an NA block have a way smaller dish that an L67 one, hence less timing is required to be correctly timed.
ralcool wrote:Yes higher octane burns slower, so we advance the timing to compensate & gain. Then the magic happens. Or raise compression instead.. or boost, or lean it somewhat
This is the part I am trying to get my head around & understand what is happening in the combustion chamber.
As stated the pistons in the n/a block are a shallower dish & about 1 % higher static comp ratio compared to the L67 engine. Is it the higher compression or boost that makes the burn time faster in the combustion chamber or the actual reduce volume due to the higher comp pistons ?
I have noticed when people throw more boost into the super6 engines & have them re-tuned, they seem to end up with more advanced spark timing than stock settings. With adding more boost the dynamic comp ratio is raised correct ?
So would this make the burn time faster requiring less spark advance ?

Cheers
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by vlad01 »

OZ38 wrote:
vlad01 wrote: The pistons in an NA block have a way smaller dish that an L67 one, hence less timing is required to be correctly timed.
ralcool wrote:Yes higher octane burns slower, so we advance the timing to compensate & gain. Then the magic happens. Or raise compression instead.. or boost, or lean it somewhat
This is the part I am trying to get my head around & understand what is happening in the combustion chamber.
As stated the pistons in the n/a block are a shallower dish & about 1 % higher static comp ratio compared to the L67 engine. Is it the higher compression or boost that makes the burn time faster in the combustion chamber or the actual reduce volume due to the higher comp pistons ?
I have noticed when people throw more boost into the super6 engines & have them re-tuned, they seem to end up with more advanced spark timing than stock settings. With adding more boost the dynamic comp ratio is raised correct ?
So would this make the burn time faster requiring less spark advance ?

Cheers

well yes, as you want peak cyl pressure to happen at 14-16º ATDC, so the faster the burn, the later the timing must be to get the peak pressure in that window to make the highest torque.
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Re: Ulimate 98 in a n/a ecotec V6 ?

Post by OZ38 »

vlad01 wrote: well yes, as you want peak cyl pressure to happen at 14-16º ATDC, so the faster the burn, the later the timing must be to get the peak pressure in that window to make the highest torque.
Yes all that part I understand, if it burns slower then advancing spark timing to get the peak cyl pressure at the optimum spot ATDC & if it burns faster then retarding the spark timing to get peak cyl pressure at that same optimum spot ATDC.

I suppose what I am asking is why raising the C/R as in the example of a Top Swap L67 onto a n/a ecotec V6, creates a faster burn in the combustion chamber. Where as in a L67 if you add more boost (raising the dynamic comp ratio) it doesn't seem to have that effect ?

Cheers
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