Octane debate settled?
Burning Brakes
Joined: Jan 2001
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From: Manhattan
Re: Octane debate settled? (Nathan Plemons)
...It also tells me though with my mods if I can run middle grade with very little timing retard, any stocker should be able to run it with NO problems...
--steve
Thread Starter
Race Director
Joined: May 2001
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Re: Octane debate settled? (Raistlin)
I agree w/ everything else, but this made me think. Since you're running a cam with larger duration and more overlap, your dynamic compression is lower. I would guess the need for octane would be less.
Thread Starter
Race Director
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Re: Octane debate settled? (CentralCoaster)
So, I'd add to you recommendation and say, "Run the lowest octane your car would require under the worst expected conditions you'd ever need to run WOT in."
BTW, for the record I do have a 180 thermostat in the car. I wanted more heat this winter and I've never swapped it back, call me lazy.
[Modified by Nathan Plemons, 7:51 AM 5/7/2004]
Pro
Joined: Jul 2001
Posts: 557
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From: Taxahoma
Re: Octane debate settled? (Nathan Plemons)
That's a very good test and it shows what some have been saying all along but monday there will be yet another thread on "do you think i can use 89 instead". :smash:
Le Mans Master
Joined: Mar 2004
Posts: 8,700
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From: Ft. Lauderdale Fl
Re: Octane debate settled? (Netnarc2)
Last week I went from 93 to 87. I have been keeping a data log. Performance is about the same and the gas millage increased .5
( 1/2 ) mile per gallon better. I will advise if the lower octane has
any effect one way or the other. :cheers:
( 1/2 ) mile per gallon better. I will advise if the lower octane has
any effect one way or the other. :cheers:
Former Vendor
Joined: Jun 2001
Posts: 7,204
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From: St Marys PA
Re: Octane debate settled? (elefkow)
Less is better. I have been doing some testing of my own on the 434. From what I am finding. I can go WOT without any detonation at all with 93 octane. Seems that the bigger cubes and cam are letting me get away with some extra compression at no downfall to needing race gas addition. My next trip to the track will be on pump gas alone. :cheers:
There is NO added benefit of running race gas, you should only run it if you need to because of compression etc. People think you make more power with it, but actually it tends to hurt more than anything if your motor doesn't need it.
:cheers: :thumbs:
There is NO added benefit of running race gas, you should only run it if you need to because of compression etc. People think you make more power with it, but actually it tends to hurt more than anything if your motor doesn't need it.
:cheers: :thumbs:
Safety Car
Joined: Sep 2000
Posts: 3,524
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From: Hinckley Ohio
Re: Octane debate settled? (ski_dwn_it)
This is a question out of pure ignorance, but lets say you put in some 104 octane and then went to the dyno & played with timing until you got maximum power at WOT.......then go back to say 87 octane and left the timing alone would you now get knock counts/retard?????
In other works is stock timing really based on maximum power or just using as much advance as you can use without causing knock on premium pump gas?
I would agree that to just put in 104 with no other changes would be a waste, but what if you then played with timing??
I am really suprised you can reduce octane to 87/89 without seeing timing retard!
:seeya
In other works is stock timing really based on maximum power or just using as much advance as you can use without causing knock on premium pump gas?
I would agree that to just put in 104 with no other changes would be a waste, but what if you then played with timing??
I am really suprised you can reduce octane to 87/89 without seeing timing retard!
:seeya
Advanced
Joined: Jul 2001
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From: ohio
Re: Octane debate settled? (Nathan Plemons)
I have a LT1 1995 and in the the "COR-VETTE SPECS" by Mike Antonick for this model year in the manufacturers specification summary it says to use 87 unleaded. I've been using the next level but I haven't noticed any difference using 87.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Re: Octane debate settled? (Nathan Plemons)
Aren't you putting a lot of faith in the knock sensor, a decent functioning EGR or something else to hold combustion temps down? Seems to me that you're going to have to look at more than knock counts - like the plugs & the top of the pistons to see if skipping premium is really economical and even doing that might not show or whole heck of lot in the short term. I'm more curious as to how Lexus, Infiniti and some of the others are going to handle warranty claims (assuming they start showing up a year or two from now) for all of the owners that are dumping in the cheapest stuff they can find, especially with premium at 2.50/gal & climbing here on the left coast.
Thread Starter
Race Director
Joined: May 2001
Posts: 14,165
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Re: Octane debate settled? (SunCr)
Aren't you putting a lot of faith in the knock sensor, a decent functioning EGR or something else to hold combustion temps down? Seems to me that you're going to have to look at more than knock counts - like the plugs & the top of the pistons to see if skipping premium is really economical and even doing that might not show or whole heck of lot in the short term. I'm more curious as to how Lexus, Infiniti and some of the others are going to handle warranty claims (assuming they start showing up a year or two from now) for all of the owners that are dumping in the cheapest stuff they can find, especially with premium at 2.50/gal & climbing here on the left coast.
Burning Brakes
Joined: Jan 2001
Posts: 1,169
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From: Manhattan
Re: Octane debate settled? (Nathan Plemons)
I agree w/ everything else, but this made me think. Since you're running a cam with larger duration and more overlap, your dynamic compression is lower. I would guess the need for octane would be less.
That's an interesting question. Ultimately though the whole purpose of the cam is to get more air into the cylinder so you can get more fuel, for a larger explosion. Wouldn't that ultimately lead to an increase in cylinder pressure? I can see an arguement for this both ways.
the lift of the camshaft determins the amount of air in the engine, more lift will produce more tourqe. the duration dertermins where the engines power band is, more duration will produce more hp (becuase hp = tq * rpm / 5250)
how much of a difference between your engine now and when it was stock? I don't know.
--steve
[Modified by Raistlin, 3:53 PM 5/8/2004]