Vapor pressures of fuels

[pavulon]

I have an '08 Z06 that has been to Lingenfelter and has 93 octane specified for fuel. The only 93 octane pump fuel around here has ethanol in it. I'd like to avoid that. So, when shopping for unleaded race fuel, I'm wondering what vapor pressure I should be looking for. Any ideas?

[asphaltgambler]

I'm lost on this one...........but here goes.

Unless I'm missing something on your post - 93 octane is well 93 ethanol or not. Modern engine management can add or subtract fuel, timing individually per cylinder. If the engine 'sees' it's running a tad lean ( with 10% ethanol ) it will add a bit more fuel - that's it.

You should be fine -

[pavulon]

The part I left out is that it's still almost an hour each way to 93 with ethanol. Otherwise it's 91 ethanol-free locally.

[sammyg2]

RVP changes by region, laws, and season.

here in smogifornia, the fuel suppliers are allowed to sell fuel with a higher RVP in the winter months, but have to switch to a blend with a lower RVP during the summer.

With hydrogen treating, the refiners can force hydrogen into the chains and make for a less dense product, and gasoline is sold by .... VOLUME!!!!
Usually a little cheeeeper to make octane that way and it can be less stable and has lower shelf life. it's still good, just not the best possible. We call it winter blend and it has a max RVP of 9, but can go up to 10 with 10% ethanol. That's high.

But during the summer, johnny law says they have to lower the RVP so they strip out more of the light ends and add more high octane alkylate or platformate blend stocks. More $$$$$$.
Max RVP of summer blend is 7.8, same as most fed regulated areas. But again, add ethanol and they are allowed to cheat up by 1 whole number.

If you have your heart set on no ethanol and want to spend bux on racing fuels, you likely looking at between 4.5 and 7 but there are some racing fuels with a rating as high as 9.
Too high and you risk vapor lock, too low and it doesn't like to vaporize and you can end up with hard starting or fouling plugs if they're cold.

Then ya gotta look at dielectric rating, color, etc. gets complicated.

I'm thinking that any decent 104 or higher octane racing fuel with no ethanol and an RVP below 8 should be just fine. 7 is good, 6 is better, 4 might cause problems.
if you need higher octane you can jump off the checkbook and get 110, but that's prolly overkill.

Racing Gasoline Comparisons

If yer just looking for unleaded 93 octane street gas with no ethanol, look for an RVP below 7.8. if you can find it.
BTW ethanol won't really hurt your performance much, the engine will just use more of it. Lower MPG.
is this a boosted engine?

Doan know if it's really a thing nowadays, but back in my day some less scrooop-ulous folks blended in as much tetra-ethyl lead as they could keep in solution to boost octane cheaply, and that can be bad fer your health. bad juju.
I only ran it fer a season, money was tight.

[Sooner or later]

Is 93 a requirement or a recommendation for max performance?

[pavulon]

Originally Posted by Sooner or later

Is 93 a requirement or a recommendation for max performance?

Lingenfelter states it as a requirement.

[JackDidley]

Why the hate for alcohol ? It helps you get that 93 octane. I ran E85 in a Corvette for 3 years and loved it. I burns soooo clean. Only quit using it because it was not available everywhere.

[RWebb]

lotsa places to Reid up on it

[Arizona_928]

Devils adovcate here; Octane booster!

[pavulon]

Thank you for your insight. I appreciate it and it helps me with my decision making process. I don't "hate" ethanol it just seems like there should be a better and more convenient (for my situation) answer.

I've always been skeptical of octane boosters. I spoke with a guy running a C7 Z06 yesterday. He runs a Torco octane booster. He's the second guy I'v met this summer running it and both claim it prevents pre-ignition well. However, this fellow showed me the brown residue all over his exhaust and it seemed pretty odd to me. Anyone familiar with that phenomenon or potential issues with build up on plugs or sensors?

I'm okay with this thread covering all the angles.

Originally Posted by sammyg2

RVP changes by region, laws, and season.

here in smogifornia, the fuel suppliers are allowed to sell fuel with a higher RVP in the winter months, but have to switch to a blend with a lower RVP during the summer.

With hydrogen treating, the refiners can force hydrogen into the chains and make for a less dense product, and gasoline is sold by .... VOLUME!!!!
Usually a little cheeeeper to make octane that way and it can be less stable and has lower shelf life. it's still good, just not the best possible. We call it winter blend and it has a max RVP of 9, but can go up to 10 with 10% ethanol. That's high.

But during the summer, johnny law says they have to lower the RVP so they strip out more of the light ends and add more high octane alkylate or platformate blend stocks. More $$$$$$.
Max RVP of summer blend is 7.8, same as most fed regulated areas. But again, add ethanol and they are allowed to cheat up by 1 whole number.

If you have your heart set on no ethanol and want to spend bux on racing fuels, you likely looking at between 4.5 and 7 but there are some racing fuels with a rating as high as 9.
Too high and you risk vapor lock, too low and it doesn't like to vaporize and you can end up with hard starting or fouling plugs if they're cold.

Then ya gotta look at dielectric rating, color, etc. gets complicated.

I'm thinking that any decent 104 or higher octane racing fuel with no ethanol and an RVP below 8 should be just fine. 7 is good, 6 is better, 4 might cause problems.
if you need higher octane you can jump off the checkbook and get 110, but that's prolly overkill.

Racing Gasoline Comparisons

If yer just looking for unleaded 93 octane street gas with no ethanol, look for an RVP below 7.8. if you can find it.
BTW ethanol won't really hurt your performance much, the engine will just use more of it. Lower MPG.
is this a boosted engine?

Doan know if it's really a thing nowadays, but back in my day some less scrooop-ulous folks blended in as much tetra-ethyl lead as they could keep in solution to boost octane cheaply, and that can be bad fer your health. bad juju.
I only ran it fer a season, money was tight.

[sammyg2]

Originally Posted by AZ_porschekid

Devils adovcate here; Octane booster!

LOL,
there is an octane booster that suggests it is over 104 octane.
Long time ago, it also advertised up to a 4 point increase in octane. But what they didn't explain was that it boosted the octane up to .4
so if you had 91 octane, it'd take it up to 91.4. Max.

They got in trouble and don't make those claims no more.
it was mostly ethanol anyway

[sc_rufctr]

Impressive posts Sammy. Bravo!

[sammyg2]

even a blind squirrel,
LOL


Here's a mind-blower:
You can mix a little 91 octane LEADED fuel with 91 octane unleaded, and end up with over 91 octane.
I sheet you not.

See, a little lead makes a big difference, but more gives diminished returns.
Good ole leaded fuel wasn't all that good because it didn't need to be, the lead made up for it. But to make higher octane UNLEADED, it had to be better gas cause it didn't have lead to help.

So you take a little leaded fuel and add it to better unleaded.
You get the ben-E-fit of the quality unleaded, and the big bump from a little lead.

[asphaltgambler]

What Sammy said..........................

Again - if the engine is tuned to that - pump gas 93 octane meets the requirement. Just know the higher octane the lower heat energy per fuel unit. So as you go up in octane rating the amount of fuel required increases to achieve the same heat energy.

MO - don't over think this.

[Rusty Heap]

Octane requirements are only driven by Compression Ratios and Ping elimination.

With today's Variable Valve timing, using Higher octane simply means less pre-ignition. correct?


I believe running say VP105 or even plane AV gas which I believe is 100. Is a waste, unless it truly is required by 12:1 pistons or such.


Pcar brain trust much smarter than I


other burning up your wallet, doesn't TOO high a octane actually can make you lose HP ?

[masraum]

I thought ethanol was often desirable for forced induction applications due to the lower energy.

I would think that a car as late a model as that wouldn't have an issue with fuel lines and ethanol like a car from the 70s or 80s.

[Tobra]

Ethanol has the effect of cooling the intake charge somewhat, or so I understand

Originally Posted by AZ_porschekid

Devils adovcate here; Octane booster!

Premium with octane booster!

Dad used to get leaded AV gas and ran it mixed with unleaded premium in the XKE. no road tax.

You used to be able to get cans of tetraethyl lead, which also worked well. Can of that in a tank of 91 octane unleaded ostensibly gets you up around 98, according to the petroleum engineer who used to live next door. Pretty sure that was illegal too, off road use only written on the can.

Excessively high octane will not make it run worse.

[sammyg2]

Originally Posted by Tobra

Ethanol has the effect of cooling the intake charge somewhat, or so I understand

Premium with octane booster!

Dad used to get leaded AV gas and ran it mixed with unleaded premium in the XKE. no road tax.

You used to be able to get cans of tetraethyl lead, which also worked well. Can of that in a tank of 91 octane unleaded ostensibly gets you up around 98, according to the petroleum engineer who used to live next door. Pretty sure that was illegal too, off road use only written on the can.

Excessively high octane will not make it run worse.

So when we heard old people talking about filling it up with ethyl, now we know why. Ethyl was another word to describe leaded gasoline, usually in premium form.


Just fer giggles, here are a few clips from the MSDS for tetra-ethyl lead. One of the reasons John Q Public don't have it no-mo:

[Sooner or later]

Back in the day ethyl and regular were both leaded fuels.

[sammyg2]