Let’s talk about gasoline

[Mark Maras]

 Engine Masters devoted one episode to low, and high octane fuel as well as E85 fuel while fooling around with timing and boost. The bottom line was the E85 didn't need the expected timing advance as much as expected and E85 produced slightly more power than high octane at high boost. E85 loves high compression ratios.

[texasz]

52 minutes ago, Av8ferg said:

I use ethanol free gas too . I’m lucky we have 93 available. I’m not sure what my CR is after shaving my head .020” with flat top pistons on a P79 and I’m using higher octane just to make sure I don’t get pre detonation, probably don’t need it but maybe one day I’ll try the 89.
 

Use the Z engine calculator to compute your compression ratio if you really want to know it.

[S30Driver]

 

[Captain Obvious]

5 hours ago, Mark Maras said:

 Engine Masters devoted one episode to low, and high octane fuel as well as E85 fuel while fooling around with timing and boost*.

Way cool! I just watched this episode last night!

So the basic takeaway from the episode (as they described it) was that if you engine isn't having detonation issues, then the octane rating of the fuel doesn't matter at all.

The longer story was.... They ran the same engine on a dyno a whole bunch of times running different fuel varieties. They did pulls using 87 pump gas, 91 pump gas, two higher octane race gas varieties (110 and 116 I think?), and then at the end they ran E85. 

They were expecting to have to adjust the timing for the different fuels, but they found that they did not. The engine wanted 29 degrees of advance for every fuel, and made the exact same power (within experimental tolerances) regardless of which fuel they used. The only exception was that the E85 actually made more power than any of the straight up gasoline varieties.

Now... Are any of their findings directly applicable back to our engines? I can come up with a bunch of questions that would need to be answered before I would believe they are, but I'm just in this for the academic entertainment.

 

* One correction to Marks note above... There was no boost. This was all N/A,

[Av8ferg]

I need to find this TV series you all are talking about.  I found this article, that discusses the problem E85 has with older cars.  Talks about why you need to make some changes when / before using E85 on classic cars and what consequences are.  Carbureted cars seem most at risk, but the the hydroscopic properties of ethanol may effect seals and gaskets on all cars built before mid 80’’s

https://driving.ca/auto-news/news/higher-ethanol-fuel-and-classic-cars-dont-mix

 

[Namerow]

I believe you meant, 'hygroscopic' (ability to absorb water).  No such word as 'hydroscopic' 

The history of E85 was (and remains) quite politically-driven.  At the start, it seemed like a win-win proposition from the environmental perspective -- an organic, renewable commodity used to reduce exhaust emissions from gas-burning vehicles with not much required in the way modifications to the vehicle.  The corn-growing regions loved it.  Then squabbling started over the diversion of food-production land towards non-food use.  IIRC, other regions got upset over the environmental impact of consuming grassland in their territories for ethanol feedstock.  Now we see ethanol being used to offset embargoed Russian oil stocks.  And on it goes.

[Zed Head]

7 hours ago, Namerow said:

No such word as 'hydroscopic' 

https://www.merriam-webster.com/dictionary/hydroscope#:~:text=Definition of hydroscope,steel tube — compare water glass

[Namerow]

16 hours ago, Zed Head said:

https://www.merriam-webster.com/dictionary/hydroscope#:~:text=Definition of hydroscope,steel tube — compare water glass

OK, fine.  No such adjective as 'hydroscopic'.  At least, not in common use.

[bartsscooterservice]

On 4/12/2022 at 5:23 PM, Av8ferg said:

 

So what fuel were are our Zs designed to use and should we use non-ethanol gas.

 

 

Sent from my iPhone using Tapatalk

 

Unleaded 95 ron.  ( You can use higher Ron doesn't really matter this is only to prevent pre ignition )

Ethanol fuel is only for modern cars that are adapted to it. Ethanol eats rubber and corrodes metal in older cars.

[the_tool_man]

On 4/12/2022 at 1:44 PM, S30Driver said:

Bottom line, use non-ethanol fuel if it is available in your area.   Where I live, only regular grade has ethanol,  I use the mid grade to avoid the ethanol in the Z cars and the mowers...

I had an opportunity to get a close look at some gas pumps being installed a few months ago. With the covers off, I noticed there were only two supply lines for the gasoline side of the pump. I asked about it and was told they mix regular and premium at the pump to make mid grade. Indeed, another station confirmed they only have two fuel storage tanks. I don't know if this practice is pervasive (I'm in the SE US). But if so, mid grade has some ethanol in it.

[SteveJ]

18 minutes ago, the_tool_man said:

I had an opportunity to get a close look at some gas pumps being installed a few months ago. With the covers off, I noticed there were only two supply lines for the gasoline side of the pump. I asked about it and was told they mix regular and premium at the pump to make mid grade. Indeed, another station confirmed they only have two fuel storage tanks. I don't know if this practice is pervasive (I'm in the SE US). But if so, mid grade has some ethanol in it.

You are correct. Mid-grade is typically a blend of premium and regular.

I am fortunate enough to live near a boating area so I can get 90 ethanol free or 87 ethanol free. I can even get 110 at a pump about 10 miles from my house.

[Zed Head]

You never really know what you're getting at the typical pump.  Today's cars are designed to adjust to the variation.  

https://www.fueleconomy.gov/feg/factors.shtml

"Some fuels contain less energy than others.

Using oxygenated fuels or reformulated gasoline (RFG), for example, can cause a small decrease (1%–3%) in fuel economy.

Most of the gasoline now sold has a small amount of ethanol in it—up to 10% by volume depending upon the region. Using gasoline with 10% ethanol decreases fuel economy by 3%–4%.

The energy content of gasoline varies seasonally. Typical summer conventional gasoline contains about 1.7% more energy than typical winter conventional gasoline."