98 octanes fuel
 

yesterday , for the first time, I used the 98 octane gas in my Corvette. Even if it was a mix 50/50 with the standard 93 oct gas already in the tank, so obtaining a 95-96 oct gas, my God what a difference!
The engine is much more responsive , above all at middle throttle and the engine sound is different , less boomy and more crisp ( more sport sound). I look forward to have only 98 oct in my tank and see what happens...
Until this 98 oct fuel will be available , I think I'll use only this. it's just 3-4% more expensive than the 93oct but the engine performances are far better and the fuel consumption ( in terms of $$$ per KM) seems about the same , due to the higher efficiency.
This 98 oct gas is advertised as a more refined gas that keeps the engine cleaner in respect to the standard gas.
which is your experience in the US about non standard gas?

I have still to check-tune my engine's timing. But I have now to pay attention because the timing should be advanced for 98 oct and retarded for 93 oct. I think I should find a mid timing to be sure to don't have my engine pinging with the standard gas ( if I need to switch back to 93 oct due to no 98 availability) . this 98 oct is available just from 1 oil company and not everywhere ( but in my town yes)

which is the power HP increase when switching from 93 to 98 oct? 5-6% more , considering that 98 is 93+ 5-6% ?

RE: 98 octanes fuel
 

man, wish I could find some 98 octane, the highest they have around here is 94, and its 4% more. Theres a station leaving town that sells 104 octane when the track is open, but its about twice what normal fuel costs

RE: 98 octanes fuel
 

To get the full benefit of higher octane fuel, you need a higher CR and advanced timing. The gas has no more stored energy with a higher octane. It just helps prevent pre-ignition with the higher CR.

Aldo, is your 98 octane unleaded?

RE: 98 octanes fuel
 

they went over the benefits of octane in my Chem class. I'm a little rusty, but the lower octance gas burns REALLY fast and really hot, and the higher the octane, the longer the gas takes to burn because the hydrocarbon chain is longer and the lower the cylinder temps. This helps the fuel to burn completely in engines that have more compression, because the lower octane fuels will burn off before the compession stroke is done, leading to spark in an empty chamber.

RE: 98 octanes fuel
 

Rusty or not, you got it right. If you don't have the compression it won't help if you put Jet fuel in the tank. PG.

RE: 98 octanes fuel
 

Hi there

the 98 oct is unleaded

I'm a bit confused about the answers of you all...

even if my engine is 9:1 CR and the advance setting seems to be a bit conservative ( I got a timing light just yesterday and I'm going to check-tune the timing asap) , I see only improvements in using the98 oct fuel instead of the 93-94...

The engine is not "sleeping anymore" , it's very quick and responsive now, the engine sound isreally beautiful , with a very aggressive "roar" , I'm possibly wrong but it seems to me that there's less tendency to overheating too...what else?

Am I wrong in using the 98 oct gason my car?

I'm searchingtech infos about high oct gas but I still don't understand why an higher oct gas can improve the engine performances. I supposed that an hi oct gas was more powerful than a low oct , but I was wrong. So which is the technical reason of better performances on Hi-performance engines?

RE: 98 octanes fuel
 

This is just a guess but maybe you have too much advance for the 94 octane and it is just on the verge of preignition. So when you go to 98, it takes advantage of the timing. Like I said that's just a guess. ;)

RE: 98 octanes fuel
 

At the gas station today:
87 oct=$3.16
100 oct=$5.99 PG.

RE: 98 octanes fuel
 

I'm possibly going to check the timing today-tomorrow. I'll post the results.

the 98 oct gas i'm using is usually purchased here by motorcycles owners and someperformance cars drivers. here is the link ( english) to this gas.

http://www.agip.eni.it/agip/internal.do?icommand=show&RID=@29u9R|0?xoidcmW opk&menu=false&lang=en&sessionId=87789 63&mncommand=openById&mnparam=agip_blusupe r&mnselected=agip_blusuper

Motorcycles shops sells also various additives to increase the octanes in standard fuel. they are small bottles to be added to about 40 litres gas. I haven't checked the prices of these additives, but they seem not very expensive, at the end

PG. 87 oct? so low?

RE: 98 octanes fuel
 

sunny day today and I finally checked my engine timing.
very funny and easy indeed ( I did it by myself with a digital timing light lended by a mech)

please check the graph.

I have

-initial timing : 10°
-vacuum : 23°
-centrifugal : 20° at 3000 rpm ( this is the max rpm I have measured.I didn't go further.I have obtained the values above 3000 rpm by interpolation with the MSD street fire graphs)

so I have these timing values:

IDLE = 33°
Mid-throttle= 53-54° ( max allowed 54°)
WOT= 34° ( max allowed 38°)

I think they are OK. I am at limit with the mid-throttle advance but I have never heard my engine pinging with the 94 oct gas , so no problem at all with higher oct gas.

Any advise is welcome...





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