Use of 110 Octane Leaded in 327

[Bryan L.]

Re: Is no lead regular "greener" than no lead prem

I haven't seen green gas in 20 years. Back in the 80's I worked on general aviation aircraft and have fueled them on occasion. The color code for avgas used to be the blue was 100/115 octane, the green was 130/145 octane and the purple was 160 octane. The FBO I worked at was in S. Texas and we got a lot of aircraft in from Mexico to work on and update the avionics, etc. At that time in the early 80's the 130/145 octane avgas was still available south of the border. It looked like lime Kool-Aid.

I have on occasion siphoned a few gallons of the Mexican avgas and ran it in a hotrod 69 Z/28 Camaro with a 355 SBC and 11.5:1 pistons that I had at the time. It sure ran good with the green gas and it also had a totally different smell than other gas.

BL

[Rob Dame]

Re: Is no lead regular "greener" than no lead prem

We have a small 5/8 mile race track near us. The gas station down the street sells Turbo Blue 110 octane. It does make the car run better the pipes seem much cleaner and I too, like the smell of it out the exhaust.

Rob

[Chuck S.]

If You Are Asking...

Is no-lead regular more "environmentally friendly" than no-lead premium, I think it would depend on how each gasoline is formulated. You shouldn't be concerned about trying to help the environment by buying one or the other...buy what the owner's manual recommends.

In the old days, Amoco's "white" gasoline derived its high octane rating from light petroleum fractions rather than tetra-ethyl lead. The more light fractions you have, the higher the octane rating. Today, gasoline octane rating is increased by using unleaded additives like MTBE (methyl tertiary butyl alcohol?), ethanol, and also by using lighter fractions same as Amoco.

In conventional refining (catalytic cracking), light fractions are the top of the barrel and there is limited yield out of each barrel making them a very expensive way to increase octane rating. In the future, "reforming" or the process of combining hydrogen molecules with heavier petroleum molecules to produce more high octane material will provide our premium gasoline. MTBE is itself becoming a health concern, and I expect it will eventually go the way of TEL. Ethanol is not cost effective without government subsidy.

The answer to your question (I think) is that there is probably not much difference between regular and premium regarding environmental impact. The primary environmental effect of any fossil fuel these days, outside of the health risks of MTBE, is combustion gases, and that will not be appreciably reduced unless we take up riding bicycles in lieu of SUVs, use candles for light, and heat our homes with solar heat.

The bottom line is the Feds aren't going to allow ANY gasoline to be environmentally unfriendly for very long these days...well, except for that CO2 thing.

[Ed Jennings]

A little gas trivia

Avgas color codes as follows

Red 80/87

Blue 90/95

Green 100/130 (Note: numerical ratings in excess of 100 are refered to as power ratings and not "octane")

Purple 115/145 This gas was phased out of production in about 1975-76.
I was an Aircraft Maintenance Officer in the USN at the time and I remember that we had to retard the timing on all the aircraft with reciprocating engines and limit the boost from the superchargers to about 52" vs 56". Made takeoff on a hot day interesting.

[John C.]

Re: If You Are Asking...

It's ironic that the Feds actually pushed for that MTBE crap which is not environmentally friendly whatsoever.

[Clare Carpenter]

Thanks Chuck, exactly what I was asking.....

Although this thread took an interesting turn, "color" had nothing to do with my original question, which stemed from GM's "green" corp policy to have all their cars run on unleaded fuel in 1971. In my original question I wondered why GM specified unleaded regular instead of unleaded premium for their performance engines, such as the LT-1. The reason provided by Duke is as follows but he didn't answer the original question, whether unleaded regular is "greener" than unleaded premium:

"The petroleum industry said they could only produce unleaded gasoline of about 91 RON, given the rapid transition that GM was pushing. I don't know if the fuel industry was dragging their feet, but that was the basic compromise that GM worked out with them. Thus, all engines had to operate on 91 RON, which required all high compression engines to drop about two points from their 1970 levels. Lower CRs also helped reduced NOx emissions, and most OEMs were struggling to meet emission standards in that era."

Footnote: On the various colors and octane levels of Av gas. We auto hobbyists have less to worry about than aviation folks flying vintage airplanes. The comment about having to retarding timing and boost, affecting takeoff is a bit scary.

[Duke W.]

Re: A little gas trivia

Ed - I believe avgas ratings above 100 are referred to as "performance number" or "PN", and the test procedure is different than what is used to test octane number of road vehicle fuels as the high octane avgas is focused at supercharged aircraft applications.

Duke

[Clem Z.]

when i still had contact gulf research labs

engineers i was told that 100 LL AVGAS was 106 octane when rated the same way as auto fuel. we would add 2 more ccs of real TEL per gallon to raise the octane.

[Duke W.]

Re: Thanks Chuck, exactly what I was asking.....

No, I would not say that lower octane fuel is "greener". Back in the early 70's the lower compression ratios required for 91 RON fuel reduced engine out NOx emissions, but reduced thermal efficiency, which reduced fuel economy.

Today, OEMs are pushing CRs back up, which improves fuel efficiency and output. NOx control is better, and detonation is handled by the knock sensors(s) and engine control electronics.

The new LS2 sports a CR of 10.9:1, and GM says 93 PON fuel is recommended, but not required. Lower octane fuel will likely reduce quoted output due to spark retard, but on a long freeway cruise 87 octane fuel should provide about the same fuel consumption.

Back when I was a grad student at the Univ. of Wisconsin Engine Research Center circa 1970 I visited the GM Tech Center. I asked about the emission levels of SHP engines. The engineer I was talking to responded that NOx was low due to all the valve overlap, which effectively creates an EGR system at low speed and load, but they were very high on HC and CO due to the rich mixtures that are required at low speed and load when there is lots of exhaust gas dilution of the fresh charge.

Excess valve overlap actually became an NOx control strategy that was used in the seventies. My Cosworth Vega is an example. The inlet/exhaust centerlines were established at 102/110 for a lobe center angle of 106 degrees on a seat to seat duration of 268 degrees (258@.006" valve lift). In order to generate a high and steady manifold vacuum the recommended idle speed is 1600, and it pulls about 16" manifold vacuum. Even after adding a vacuum advance (not OE) the lowest idle I could achieve with acceptable idle quality was 1200@12".

After extensive computer simulations I reindexed tha cams to 110/118 centerlines (8 retard on inlet, 8 advance on exhaust), 114 lobe center angle, which showed the best torque bandwidth. Turns out that these centerlines are the same as the L-79 cam, which is probably no coincidence being as how both the CV and 327 have nearly the same stroke, and "ideal" valve timing to achieve the greatest torque bandwidth is more a function of stroke than cylinder head architecture. It now idles butter smooth, 900@18", has better low speed torque and operating characteristics due to the reduced overlap, and pulls stronger at the top end due to the later closing inlet valve.

In my last emission test the NOx doubled, but it was only one-quarter of the allowable limit prior to the cam reindexing, so it's now only half the limit.

Duke

[Ed Jennings]

Re: A little gas trivia

Duke, you may be correct in the terminology. The point is that when I went to AMO school, we were told that "there is no such thing as an "octane" rating in excess of 100%". Fuels that have anti detnotion qualities in excess of 100% octane are assigned "power numbers" or perhaps it was "performance numbers" to designate the fuel qualtiy. Might be a difference here in USN and USAF nonenclature. If I remember the class correctly, and I may not 30+ years later, octane ratings are expressed as a percentage of the anti-knock quality of 100% octane.

[Clem Z.]

that is why a LS-1 engine

in a camaro and firebrd needed a EGR valve and the LS-1 in a corvette did not was because of more overlap in the corvette camshaft

[Chuck S.]

Duke, I Think You Said...

Lower octane gasoline will be "greener" PROVIDED that engines are designed with lower compression ratios, and more valve overlap? So, it is actually the engine design, which implicitly requires regular or premium gasoline, that is "greener"...maybe a Malibu is "greener" than a Corvette?

I was unaware that GM was going for corporate "greeness"; it's a good thing and you can't argue with that. But, if we are going to be forced to drive "green" cars, then GM better start boarding the hybrid market where the engine only runs half the time. Now, I suppose we will be seeing lower compression ratios again to allow "green" engines to use regular gasoline. I guess that's what this is all about...anti-knock controls can only go so far.

I was looking at this question as for a given vehicle with a fixed engine design. In that case, wouldn't low octane gasoline actually increase the HC and CO levels because of slightly richer mixtures at any given speed? Back in my youth, I remember that premium gasoline was the only way I could feel good about the gas mileage of my old flathead Ford; there was a noticeable change (increase) in the way it sucked down that regular.

[Duke W.]

Re: that is why a LS-1 engine

I could also have something to do with the Corvette's lower EPA inertia class due to lighter weight. A lighter car can have greater proportional emissions than a heavy car because it takes less power, which means less exhaust flow, to to run a car through the test.

All "passenger cars" have to meet the same absolute emission standard in grams per mile, so a small light car can have higher proportional emissions. During the test the entire exhaust gas mass is collected in a big plastic bag. Then proportional emissions are sampled and converted to grams per mile based on the total volume of exhaust gas.

Duke

[Clem Z.]

the hybrid cars will only appeal to very small

amount of the car buying public and wait till those hybrid cars need new batteries for for big $$. they only get a few MPG more than a all gasoline small car. i refer to all those small cars as "2 man coffins". i also do not think those hybrid cars will pull my quad trailer to the mountains. we could cut the gasoline use in this country if we would just close down all the shopping malls and keep all those little old ladies home.

[Duke W.]

Re: Duke, I Think You Said...

Well, I have to add that the question is somewhat rhetorical. Back in the late sixties GM was looking at the proposed 1975 emission standards with trepidation. Their conclusion was that catalytic converters would be required, and converters required unleaded fuel. The petroleum industry said the best unleaded fuel they could produce in the required volume was 91 RON. Thus the die was cast, and to get the ball rolling management decreed that ALL 1971 engines would be required to operate on unleaded 91 RON (comparable to today's 87 PON) fuel. This stand was based on both technical and "political" considerations as GM wanted to be seen by the public and environmentally aware and concerned.

Since that era, emission control technology has advanced by orders or magnitude and has become relatively insensitive to compression ratio and octane. Manufactures design high output engine with higher CRs to improve advertised output and fuel economy, but these engines can be operated satisfactorily on lower octane fuels, and in normal driving, they achieve better fuel economy due to the higher CRs. Fuel economy may be reduced slightly if lower octane fuel is used, but the difference may not be measureable for most drivers unless they are heavy footed and do a lot of stop and go driving. A high CR engine can cruise on the freeway with optimum spark advance on lower octane fuel than it needs for optimum spark advance at high load (low manifold vacuum).

IMO it makes sense to raise CRs across the board, then let the owner select the octane based on his needs - regular if you're thrifty and premium for those who always want the highest engine output available at all times.

As far as emissions are concerned, there isn't much if any difference. Emission certification is done with a homogeneous reference fuel such as octane to eliminate any variation with available commercial fuel, and all passenger cars have to meet the same absolute grams/mile limits. Emission levels may vary slightly from blend to blend, but there is no way for us to tell which produce the lowest emissions.

This thing has gone to extremes with all the "boutique blends" that are required in various parts of the country at various times of the year, which has been a big contributor to recent shortages and price spikes. Generic gasoline blends can no longer be shipped to parts of the country where more supply is needed. Each region has a specific blend that only some refiners can readily produce without major reconfiguration.

Technical data I have seen questions the efficacy of this policy, but the average voter/taxpayer doesn't understand. Some environmentalist wacko screams about the environment and the government responds with regulations that cost consumers more while having little or no effect in some cases. The EPA is not legally required to conduct cost benefit analyses of the regulations it promulgates.

It's a sad commentary that our society is being driven by small activist groups that promote junk science, which is amplified by the mass media, who don't know a hydrocarbon from carbon paper. We ignore good science for "political correctness", and the average citizen knows nothing about the underlying science and doesn't want to learn.

If you want to be "green" drive a modern passenger care, not a truck, which includes minivans and SUVs. Passenger cars have to meet tighter emission and fuel economy standards than trucks, which is a loophole that the manufacturers have exploited by putting station wagon bodies on truck frames and only having to meet truck emission and fuel economy (and safety) standards. The proliferation of truck based passenger cars has increased our petroleum consumption, increased emissions, and placed passenger cars drivers at higher risk of death and injury in the event of a collision because truck bumpers can be higher than passenger car bumpers and passenger car side guard door beams.

Duke