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speedbiu
speedbiu Reader
8/26/11 9:50 p.m.

Looking for a little more octane and the local marina has 101,the closest racing fuel is 50 miles away,will it work?

stuart in mn
stuart in mn SuperDork
8/26/11 10:02 p.m.

What kind of engine or vehicle do you want to use it in, and for what purpose?

curtis73
curtis73 Dork
8/26/11 10:18 p.m.

Yup, its just plain gas. Most marinas spec for no ethanol, and others cheap out and use extra ethanol to get the octane.

But marine fuel is the same gasoline as auto gas.

speedbiu
speedbiu Reader
8/26/11 10:31 p.m.

In reply to curtis73: Thanks.I thought so but just had to ask.

mad_machine
mad_machine SuperDork
8/26/11 10:35 p.m.

living at the shore.. you pay more for marina gas.. with a good chance of water in it.

Not sure.. but I think Marinas were one of the last places you could get leaded fuel

EvanR
EvanR Reader
8/27/11 2:33 a.m.

Be advised (and this depends on your state)...

Boat gas prices do not include a "road use" tax. Thus, it may be (technically) illegal for you to use boat fuel for on-road use.

I don't know if anyone has ever been caught at it, but...

NOHOME
NOHOME HalfDork
8/27/11 6:38 a.m.

What makes you think that you will benefit from race gas?

All it does is burn slower as the octane number goes up.

hrdlydangerous
hrdlydangerous Reader
8/27/11 8:04 a.m.

In reply to NOHOME: Moar boosts? I hope.

wbjones
wbjones SuperDork
8/27/11 8:31 a.m.

higher octane helps when you've advanced the timing ... no / yes ..????

curtis73
curtis73 Dork
8/27/11 9:27 a.m.

Octane requirements are entirely based on the combination; chamber design, static compression, cam timing, rpm of peak boost, etc.

wbjones: if your combo would benefit from more ignition advance and if that requires higher octane, then yes. A good example: my LT1 only requires 87 octane with 10.5:1 compression because of the knock sensors and superior fuel control. But, the ignition curve was less than ideal. I retuned it for a more ideal spark curve and then it required 91 octane.

curtis73
curtis73 Dork
8/27/11 9:30 a.m.
NOHOME wrote: What makes you think that you will benefit from race gas? All it does is burn slower as the octane number goes up.

That used to be true with tetraethyl lead, but its not really the case any more. The most that I've seen measured is a 2 ms delay in the flame front all things being equal.

But, typically if the combination is set up to need higher octane the flame front speeds are faster overall. For instance, an engine with 9:1 burning 87 octane will typically have a slower flame front than the same engine with 10:1 burning 91 octane. Octane rating isn't the biggest factor in flame front speed.

curtis73
curtis73 Dork
8/27/11 9:32 a.m.
speedbiu wrote: In reply to curtis73: Thanks.I thought so but just had to ask.

The truck that brings our fuel to the marina is the same truck that stops at the gas station on the highway.

alfadriver
alfadriver SuperDork
8/27/11 10:55 a.m.
wbjones wrote: higher octane helps when you've advanced the timing ... no / yes ..????

If there is a knock issue.

As a follow up to Curits, aerodynamics has a lot more influence on flame speed than octane does. By a lot.

Higher octane does not mean burn slower, it means that the molecules are more stable under conditions that start knock.

wbjones
wbjones SuperDork
8/27/11 12:33 p.m.

so.. ??? have I been wasting money ( dyno time is coming, just hasn't happened yet) by using 93 octane in the CRX (B16 stock internals) CAI, header, and all the timing I can crank in ( old enough that it still has a turnable distributor ) ... it's a TT and a-x car that drives to and from events

JoeyM
JoeyM SuperDork
8/27/11 12:37 p.m.

Does it have a catalytic converter?

You might be doing worse than wasting money on expensive fuel....you might even be clogging the cat with unburned fuel, thus reducing the amount of flow through your exhaust?

alfadriver
alfadriver SuperDork
8/27/11 12:41 p.m.

In reply to wbjones:

Maybe, maybe not.

Especially on older cars where temperature adjustments are not as sophisticated, you might be getting insurance from the engine running hot, which increases the knock sensitivity.

I run premium on my GTV since I know it runs hot. All in all, it's pretty cheap insurance. You've modified your car that may or may not have increased it's sensitivity to detonation. Not having hard data to show an influence, and running it hard, I would not faut anyone for running premium in your situation.

And I can't prove that I needed 104 octane on my turbo Spider back in '02-04's challenge.

IF it knocks, it's worth it.

alfadriver
alfadriver SuperDork
8/27/11 12:43 p.m.
JoeyM wrote: Does it have a catalytic converter? You might be doing worse than wasting money on expensive fuel....you might even be clogging the cat with unburned fuel, thus reducing the amount of flow through your exhaust?

If the fuel has lead in it, you would do damage.

Otherwise, unless you are running richer than 9:1, you are not causing damage. UNLESS (and this is important) UNLESS there is a misfire. If you are getting a misfire of anykind, with fuel, it takes almost no time to cook a catalyst.

JoeyM
JoeyM SuperDork
8/27/11 12:53 p.m.

Thanks. That's worth knowing.

speedbiu
speedbiu Reader
8/27/11 2:23 p.m.

OK,the car I was asking about has high comp.and is a race car with no hwy use.It was built to run on 93 octane but after the dyno test I was advised to boost the octane for max HP.I know running 110 or 112 will not help me but 101 would.As for exhaust I have open headers with no Cat. and it has a carburetor..Comp is 13.5 or more.

wbjones
wbjones SuperDork
8/27/11 3:34 p.m.

in my case ... yes to the cat... maybe to the high temps.... water temp on track stays about 210 - 220°... the oil temp was pegged at 250° before the oil cooler, will find out in 3 wks what it is w/ cooler

along the same lines... assuming for a moment that 87 octane would be ok.. which would be better... 87 name brand w/ethanol or 93 (no name ) w/o ethanol ?

curtis73
curtis73 Dork
8/27/11 5:48 p.m.
wbjones wrote: in my case ... yes to the cat... maybe to the high temps.... water temp on track stays about 210 - 220°... the oil temp was pegged at 250° before the oil cooler, will find out in 3 wks what it is w/ cooler along the same lines... assuming for a moment that 87 octane would be ok.. which would be better... 87 name brand w/ethanol or 93 (no name ) w/o ethanol ?

Ethanol has a higher octane rating, but less energy per gallon... about 2/3 the energy. Octane rating is octane rating. One way to increase octane level is by adding ethanol which ups the octane but reduces energy content. If you need 87 octane, then you will do best (make more power) with pure gasoline instead of ethanol blends.

As far as brand name vs. off brand: Most chains and even independent stores buy from major manufacturers or a generic local equivalent. They are heavily scrutinized on a weekly basis to conform to ASTM standards, so I don't care if you buy it at Exxon, Texaco, BP, or Mom and Pop's Shop, it all conforms to ASTM standards. Just buy it from a high-volume shop so you're sure it stays fresh and its all the same stuff.

... But good luck finding non-ethanol blends these days

wbjones
wbjones SuperDork
8/27/11 6:48 p.m.

thanks for the answer Curtis

there is a Solo station 100' from the entrance of CMP that has a sign on their pumps that claims 93 is ethanol free... 87 and 91 ... up to 10%.... don't know how high volume at other times they are , but on a track day or race day they have actually sold out by closing time Sun...

reason for the question is I'll try to get it tuned for 87 when we finally get it on the dyno

foxtrapper
foxtrapper SuperDork
8/27/11 7:09 p.m.

What is marine fuel varies state to state. Here, there is no special exemption from the state mandated ethanol content law, or the taxes. So you're legal (I think) to run it in your car, with no benefit whatsoever.

Avgas is different.

irish44j
irish44j Dork
8/27/11 7:12 p.m.
mad_machine wrote: living at the shore.. you pay more for marina gas.. with a good chance of water in it. Not sure.. but I think Marinas were one of the last places you could get leaded fuel

depends on the marina. My parents own one, and the fuel tanks are on the shore about 10-15 feet above water level. All of the piping to the pumps on the piers are suspended just below the pier decking, so they're not in the water (except during hurricanes) and are sealed anyhow (if gas can't get out, water ain't getting in)

Only marinas it could be an issue with are those that are on very low-lying land.

With regard to ethanol - good marinas use non-ethanol gasoline, since ethanol isn't good for many marine engines. If you find a marina using ethanol-added fuel, you'll find a marina that likes to do alot of boat repair work ;)

spitfirebill
spitfirebill SuperDork
8/28/11 12:16 a.m.
EvanR wrote: Boat gas prices do not include a "road use" tax. Thus, it may be (technically) illegal for you to use boat fuel for on-road use. I

Same dealeo with av gas. I was going to buy some when i used to autocross my TR3. Never got around to it.

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