100 Octane Pump Gas by 2020?

[David Redszus]

The IDEAL combustion of any hydrocarbon is:

HC + O2 --> CO2 + H2O

The actual combustion of any hydrocarbon is:

HC + O2 --> CO2 + H2O + hundreds of trace amounts of obscure hydrocarbons.

In fact, what comes out of a tailpipe often does not resemble what goes into the engine.

[n2omike]

The IDEAL combustion of any hydrocarbon is:

HC + O2 --> CO2 + H2O

The actual combustion of any hydrocarbon is:

HC + O2 --> CO2 + H2O + hundreds of trace amounts of obscure hydrocarbons.

In fact, what comes out of a tailpipe often does not resemble what goes into the engine.

That's what was emphasized in the below reply. The fact that 80% of the 'air' the engine is ingesting is Nitrogen and only 20% Oxygen... means nitrogen becomes a reactant, producing various Nitrogen Oxides... hence the 'x' in NOx. The limited amount of Oxygen means the reactions involving O2 don't always go to completion... You get CO, or Carbon Monoxide instead of Carbon Dioxide, etc. You also get Hydrocarbons that pass through without being fully burned.

How this is dealt with, is shown below...

Chemistry guy here...

The IDEAL combustion of any hydrocarbon is:

HC + O2 --> CO2 + H2O

However, this is a fantasy. The atmosphere is 80% nitrogen and only 20% oxygen.
Therefore... Since Nitrogen is present, it WILL get fused with oxygen into NOx. Heat and cylinder pressure are what cause this. In the old days before converters could split NOx into N2 and O2, they used low compression ratios and retarded cam timing to kill cylinder pressure to minimize NOx production.

Since oxygen is only 20% of the atmosphere, we encounter incomplete combustion... so instead of producing all CO2, we get CO formed. We also get the incomplete combustion of hydrocarbons (HC), so those exist in the exhaust as well.

The first stage of modern cats breaks down NOx... NOx ---> N2 + O2
The oxygen produced is then used to convert CO into CO2... CO + O2 ---> CO2
That oxygen is also used to finish burning any HC that makes it through.... HC + O2 ---> CO2 + H2O

NOx is a GOOD thing in modern cats. It breaks down to form the oxygen required for the other processes. It was bad before they came up with that first stage that breaks them down. Back then, they had to add air pumps to blow air into the exhaust so the old catalytic converters could react the CO and unburned hydrocarbons. You won't see limited compression ratios and cylinder pressure anymore. Higher compression, turbos, superchargers, etc are all very common nowadays.

[pdq67]

Two things here.

I think Gary, (aka, GOSFAST), on the boards has posted that some guys out east in dedicated engines have ran E85 up to 17 to 1 CR, (probably blown compression?).

Anyway, the ethanol deal got started because of SMOG in the air.

St. Louis found out that when the alcohol containing fuels got pumped, that the fumes coming out of the gas tank at fill-up caused SMOG, so they went to, "bellows pump dispensers", to combat this crap. They sucked the fumes at the tank fill-up and put them back in the underground storage tank.

At a hell of a cost to the consumer.

St. Louis finally got better air-wise and did away with this system of fuel vapor control.

pdq67

PS, a 3rd thing! O/H dissociates at around 4,000 degrees F because I wondered if something like a highly -OH containing material could be dissociated and made into a fuel.. I want to say Vit. C or ascorbic acid?? I think one compound contains like 6 or 8, "-OH's", in it...

[gmrocket]

Aren't we already just about there? 100 RON , 95 rated in the U.S. and Canada .

We can easily get 94...so what if they call it premium, it's readily available.

Anything above that would be beyond what they are talking about...unless that would be the minimum, which really isn't sensible because so many cars on the road do not need 94 or better.

Over octaning isn't good for emissions , mileage or performance, is it?

I remember reading a good article put out my shell fuels. They said today's oxygenated fuel is so much better than the old fuels,,,even the same octane rating, today's fuels can stand more combustion pressure.

[Truckedup]

I'm far from an expert....Some bikes and cars have static compression ratios of 12-1 along with variable valve timing that supposedly run at full power on 91 R+M/2 pump gas....Maybe in a few years designs will aloow even higher cyliner pressures, N/A or supercharged on the same or lower octane ?

[pdq67]

I am under the impression that E85, (when 85 percent alcohol), is good to right at 13.5 to 14 to 1 static compression ratio in our old engines.

Is this so because if it is, compression ratios like these are real horsepower makers.

pdq67

[naukkis79]

Mazda Skyactiv-X has 16.3:1 compression ratio, though uses HCCI at part throttle. With regular gas.

E85 can stand crazy amount of cylinder pressure, my daily driver has 15:1 cr 4-valve engine and it's almost impossible to get knock - it won't knock with lean mixture or with stupid amount of spark advance, plugs won't seize with stupidly over rich AFR - tuning window is enormous compared to gas. And main reason to use E85 is it's low price.....

[FC-Pilot]

I am under the impression that E85, (when 85 percent alcohol), is good to right at 13.5 to 14 to 1 static compression ratio in our old engines.

Is this so because if it is, compression ratios like these are real horsepower makers.

pdq67

I have built multiple 540 size BBC engines with compression right at that level without so much as one issue on E85. Both iron and aluminum heads. Personally I like iron heads with alcohol based fuels as I don’t see near as much inconsistency with iron like I do with aluminum. Aluminum head combos seam to be much more temperature sensitive, where iron will run the number with a much bigger running temp window. At least on my stuff. I don’t want to speak for everyone.

But back to E85, it will take the compression even out here in the desert. Sadly, for a daily driver you just don’t get the mileage.

On a side note, I tested a batch of “Flex Fuel” a few weeks ago and it was only about 55% alcohol.

Paul

[Tom Walker]

After watching video of the Mazda skyactiv-x theory of operation, I had the impression it does not require high octane fuel.
Lower octane fuel may help the compression ignition take place when it should. Sure looked like a complicated way to modify the simple diesel combustion process, but they want gasoline as the fuel, not diesel.

[naukkis79]

After watching video of the Mazda skyactiv-x theory of operation, I had the impression it does not require high octane fuel.
Lower octane fuel may help the compression ignition take place when it should. Sure looked like a complicated way to modify the simple diesel combustion process, but they want gasoline as the fuel, not diesel.

HCCI and diesel process are totally different. With HCCI you fill cylinder with burnable mixture and burn that simultaneously, in diesel engines you fill cylinder only with air and control burn with injecting fuel - the diesel principle is to burn mixture so slowly that burn happens in constant pressure not in constant volume.

VW also tries to use HCCI with their diesel engines at part throttle, so inject lean mixture in intake stroke and fire it at tdp with normal diesel injection to simultaneously combust all that premixed lean mixture but that isn't at commercial status yet.

HCCI is the holy grail of internal combustion engine, that has tried to do tens of year but only Mazda now has accomplished it so well that it can be used in production engine.

HCCI engine detonates. It's the most efficient way to get energy out of fuel but as engine tuners know, uncontrolled detonation will break engine very rapidly. It's a great engineering accomplishment that HCCI engine is now reality, and it's development is surely have costed Billions.

[gmrocket]

I'm far from an expert....Some bikes and cars have static compression ratios of 12-1 along with variable valve timing that supposedly run at full power on 91 R+M/2 pump gas....Maybe in a few years designs will aloow even higher cyliner pressures, N/A or supercharged on the same or lower octane ?

Yup,,I just bought a new bike,, it's 12:1 and it can run on 87., but they recommend 91

[naukkis79]

Mazda previous gen Skyactiv-G has 14:1 cr and will also run on standard gas. Key to operate with high cr is to scavenge hot exhaust gases out and have high turbulent efficient combustion chamber.

[Truckedup]

I'm far from an expert....Some bikes and cars have static compression ratios of 12-1 along with variable valve timing that supposedly run at full power on 91 R+M/2 pump gas....Maybe in a few years designs will aloow even higher cyliner pressures, N/A or supercharged on the same or lower octane ?

Yup,,I just bought a new bike,, it's 12:1 and it can run on 87., but they recommend 91

What brand and does it have variable cam timing and a catalytic convertor?...

[gmrocket]

I'm far from an expert....Some bikes and cars have static compression ratios of 12-1 along with variable valve timing that supposedly run at full power on 91 R+M/2 pump gas....Maybe in a few years designs will aloow even higher cyliner pressures, N/A or supercharged on the same or lower octane ?

Yup,,I just bought a new bike,, it's 12:1 and it can run on 87., but they recommend 91

What brand and does it have variable cam timing and a catalytic convertor?...

BRP Rotax ACE, which stands for advanced combustion efficiency. it has a huge catalytic converter which will be coming off soon. no VVT, 4 vlvs per cyl DOHC water cooled

[Truckedup]

I didn't know the Rotax engines were used in new bikes.....