100vll

[Domenic T.]

Re: 100vll

Unfortunately Dom, that's more myth and misunderstanding. All gasoline burns more or less at the same speed and any variation is independent of the octane rating. There's 'fast burning' premium and 'slow burning' regular and vice versa.

The octane rating of a fuel represents resistance to detonation and nothing more.

To be clear, what John said is true- different types of fuels burn at different speeds.

Michael,
Don't know where you got your info but it might look that way when you throw it on a camp fire but in an engine it is different.

I can tell you that it does burn at different speeds as I studied that years ago when I got my aircraft mechanics licence.

Put lower octane in a high octane aircraft engine and you get detonation.

A engine is a engine and there is no difference air cooles or water cooled.

When I drove my C2 I had to loosten the distributor so I could twist it when I used pump gas, I could tell you the octane difference from 91 at one station and 91 at another. some advertised 91's would ping and some didn't, A difference of 1/2 octane.

Now maybe these new fuels burn at the same speeds but the GOOD fuel we had didn't.

That is exactly why the C2 and older cars don't run that good on the fuel you can use in the later vettes.

I HAVE tried it and it simply does not work.

The PING happens when you put a lower octane in your car, the fuel is BURNING faster!

On paper is one thing, hearing it and doing it is another.


DOM

[Michael W.]

Re: 100vll

Dom,

With all due respect, you've got a few facts confused. Here's one of my favourite definitions of detonation:

Knocking (also called knock, detonation, spark knock, pinging or pinking) in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.
..........
Knocking should not be confused with pre-ignition (also discussed in this article).


source: http://en.wikipedia.org/wiki/Engine_knocking

The key sentence in this paragraph is: one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.

If high octane fuel actually meant 'slow burning fuel' how/why would these other pockets 'explode' independently of the normal combustion process? Further down the same page there is this paragraph:

"When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur. Detonation is characterized by an instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front. A local shockwave is created around each pocket and the cylinder pressure may rise sharply beyond its design limits."

The bolding above is mine. Again- octane rating is a measure of resistance to ignition/explosion and not a measure of burn speed. In simplistic words, low octane fuel is easy to light, high octane is more difficult. It's always been that way, nothing new or different.

I was oblivious and indifferent to these semantics until my job brought me to a review of engine certification paperwork filed with our DOT. Therein was documents from each of the fuel suppliers used indicating and certifying the 'burn speed' or rate of flame propagation. As stated, no difference with high, low, leaded unleaded or even the much revered 100LL. If I remember correctly, there was one set of documents where 115/145 was tested. Those papers were pretty brown at the edges.

[Duke W.]

Re: 100vll

Well, I hope everyone in this thread attends the 2012 National Convention in San Diego where I will be discussing this and related subjects at the technical seminar I will host. For the time beinging I'll subtitle it as "The Combustion Process in Spark Ignition engines". (BTW, compression ignition combustion, otherwise known as diesel combustion, is a very different phenomenon.)

In the meantime. I'll let Michael Ward continue his accurate discussion of the subject and his attempts to kill all the myths and misinformation.

It may make my job in San Diego easier.

Duke

[Philip C.]

Re: 100vll

I use 100LL because it doesnt eat or gum up anything in the fuel system. I have used it for years, had it in the tanks of my cars for years and never had a prolbem with fuel when restarting them. My old 56 chevy race car had cam 2 in it for 25 years. That car sat in a unheated garage for all those years. I drained the tank, it had about a gallon and half in it, it looked like trans fluid but the tank looked brand new inside. The electric fuel pump worked and is still working. If you drive your car a lot, pump gas is OK but if it sits more than a couple of months I would never ever use pump gas. Phil 8063

[Clem Z.]

Re: 100vll

I use 100LL because it doesnt eat or gum up anything in the fuel system. I have used it for years, had it in the tanks of my cars for years and never had a prolbem with fuel when restarting them. My old 56 chevy race car had cam 2 in it for 25 years. That car sat in a unheated garage for all those years. I drained the tank, it had about a gallon and half in it, it looked like trans fluid but the tank looked brand new inside. The electric fuel pump worked and is still working. If you drive your car a lot, pump gas is OK but if it sits more than a couple of months I would never ever use pump gas. Phil 8063

i think that is why they suggest you fill the tank to the top before winter storage because if some gas does evaporate there is still a lot left so it does not become thick and gummy. i fill the tanks and use stabil in all my toys,quads,dirt bikes and mowers i store over the winter and have had no problems starting them in the spring. just make sure to run them after putting in the stabil so it gets into the whole fuel system

[Domenic T.]

Re: 100vll

Michael,
It is obviuus that you need to get your hands dirty in a shop.
I don't need the book work as I studied that years ago when they trusted me and licenced me.

I have a licence to work on aircraft and we had to re-stamp engine data plates and install 100 octane valves to run the 100 octane when 80/87 was discontinued, yes even the valve angle and seat were changed because of the temp & burn time using a slower more complete burning gas.

I have guys ask me to build them an engine that will run on pump gas.

What does that mean?

That means lowering the compression ratio.

In ALL cases we do that to run todays gas.

This can all look good on paper but doesn't fly in the real World.

With the compression ratio in your 1973 you can burn anything.

In high compression engines without a computer you can with ugly results, and that is what people are accepting that read to many articles and have not worked DIRECTLY with the problem.

I am not confused, I am experianced with this problem since the 50's.

It seems that the ones that do not have the choice of using this fuel seem to defend what they read and have to use.

Do you think the oil companies are going to tell you they are making a killing selling the fuel made for TODAYS engines, NO WAY, they sugar coat it in articles, octane is EXPENSIVE.

Our high compression engines of yesteryear (which by the way is above 10:1) are NOT concidered at the pump.

I have guys that buy the older high compression cars and ask me to drive them and tell them what I think .

The truth is that I can't hurt their feelings. They were not there 45 years ago to see how they really ran.

I CAN'T time them to factory specks without them PINGING on pump gas.

Now if you can time a 11.7 :1 to factory specs running 91 and not hear the noise then you do not have the compression you think.

I have experiance with the old & new fuel and COMNPLETLY understand slow burning VS fast burning fuels.

Maybe all the pump gas today burns at the same rate but av-gas and the gas we had back then didn't.

With the compression in my obsolete STOCK cars I have to use high octane to get them to run.

Put the books down and do a dyno test or run or run one down the drag strip and see if your ET is the same as it was when the older high compression cars were in.

My 365 felt like a weak 300 HP on 92 octane, I didn't read that, I felt the difference.

We do mostly muscle cars and are asked to change the compression ratio when we rebuild.

DOM

[Michael W.]

Re: 100vll

If you drive your car a lot, pump gas is OK but if it sits more than a couple of months I would never ever use pump gas. Phil 8063

Phil,

I've been storing summer toys over the long Canadian winters since the late 60s. Conversely, I also store winter toys over the short Canadian summers. I've never once had problems at start up time and use straight pump gas, no Stabil. I understand that lawn equipment and their carbs with tiny passages might benefit from Stabil, but on cars, bikes snowmobiles it seems to be redundant.

For very long term storage, probably a drained and dry tank would be the best solution.

[Duke W.]

Re: 100vll

i think that is why they suggest you fill the tank to the top before winter storage because if some gas does evaporate there is still a lot left so it does not become thick and gummy. i fill the tanks and use stabil in all my toys,quads,dirt bikes and mowers i store over the winter and have had no problems starting them in the spring. just make sure to run them after putting in the stabil so it gets into the whole fuel system

The smaller the "vapor dome" in the tank, the less chance for water condensation, which is the primary reason for keeping the fuel tank full during storage.

Lighter components, which are usually the highest octane components are the most likely to boil off during storage, but this is minimized during winter storage in most parts of the country due to low average winter temperatures, which are well below the 10 percent point of even winter blends of gasoline.

Models with evaporative emission controls are less likely to suffer from either water condensation or boil off due to having a pressure/vacuum release valve that will hold about 2 psi pressure and about the same vacuum before opening.

Duke

[Domenic T.]

Re: 100vll

I use 100LL because it doesnt eat or gum up anything in the fuel system. I have used it for years, had it in the tanks of my cars for years and never had a prolbem with fuel when restarting them. My old 56 chevy race car had cam 2 in it for 25 years. That car sat in a unheated garage for all those years. I drained the tank, it had about a gallon and half in it, it looked like trans fluid but the tank looked brand new inside. The electric fuel pump worked and is still working. If you drive your car a lot, pump gas is OK but if it sits more than a couple of months I would never ever use pump gas. Phil 8063

Philip,
I have to do the same because I live in the desert and the fuel takes a beating here and smells like road kill in a few months,

A lot is relative to the climate.

Also we have found that if you drain some carbs or gas tanks completely the rubber cracks, especially the cars with the fuel pumps inside.

DOM

[Domenic T.]

Re: 100vll

Well, I hope everyone in this thread attends the 2012 National Convention in San Diego where I will be discussing this and related subjects at the technical seminar I will host. For the time beinging I'll subtitle it as "The Combustion Process in Spark Ignition engines". (BTW, compression ignition combustion, otherwise known as diesel combustion, is a very different phenomenon.)

In the meantime. I'll let Michael Ward continue his accurate discussion of the subject and his attempts to kill all the myths and misinformation.

It may make my job in San Diego easier.

Duke

Duke,
It seems that none of the paper solutions work well in the real world.

NONE of the pump gas octane #s I read worked.

We built a paper 350 for a customer/ friend and he designed the cam, pistons, chambers, everything on PAPER.

Looked good to him and bad to us. The cam was all low end torque.

It was all on paper and was to put out 440HP.

Who ever wrote the artical that led this guy down the path must have believed every thing he read.

I do hope that you do not believe that all gas burns at the same rate in a cumbustion chamber.

DOM

The owner was happy untill I told him that it ran more like a 300 HP 327.

It insulted him and he brought it to a dyno in so cal where the engine was about 150HP shy.

The guy told him it wasn't breathing right.

We almost got stiffed for the money because a cam wasn't doing what the article said it would.

[Michael W.]

Re: 100vll

On the subject of burn speed vs. octane, here's an interesting paper from a gasoline supplier written in an attempt to separate myth from facts:

http://www.google.com/url?sa=t&source=web&cd=2&ved=0CCAQFjAB&url=http%3A%2F%2Fwww.rockettbrand.com%2Ftechsupport%2Fdocuments%2FTechBulletins%2FFlameSpeedOctaneAndHpRelationships.pdf&rct=j&q=burn%20speed%20octane&ei=GfuAToWQMOnI0AHj9fHtDw&usg=AFQjCNEhebCqx2HwW8OivvBcSmqxQZLRwA&sig2=2GUs0SCOngHcX1s0bcDCTw&cad=rja

This is a .pdf download.

Here's a few titillating excerpts:

"Flame speed is determined by the hydrocarbon components in the gasoline. It is critical to making max power, but not related to octane quality.

The octane number of a gasoline has little to do with how fast it burns or how much power the engine will make. Octane number is the resistance to detonation. ....... Octane number is not related to flame (burn) speed either. Variations in octane quality are independent of flame speed.

There are some high octane gasolines in the marketplace with fast flame
speeds and some with slow flame speeds."

Enjoy.

[Domenic T.]

Re: 100vll

On the subject of burn speed vs. octane, here's an interesting paper from a gasoline supplier written in an attempt to separate myth from facts:

http://www.google.com/url?sa=t&source=web&cd=2&ved=0CCAQFjAB&url=http%3A%2F%2Fwww.rockettbrand.com%2Ftechsupport%2Fdocuments%2FTechBulletins%2FFlameSpeedOctaneAndHpRelationships.pdf&rct=j&q=burn%20speed%20octane&ei=GfuAToWQMOnI0AHj9fHtDw&usg=AFQjCNEhebCqx2HwW8OivvBcSmqxQZLRwA&sig2=2GUs0SCOngHcX1s0bcDCTw&cad=rja

This is a .pdf download.

Here's a few titillating excerpts:

"Flame speed is determined by the hydrocarbon components in the gasoline. It is critical to making max power, but not related to octane quality.

The octane number of a gasoline has little to do with how fast it burns or how much power the engine will make. Octane number is the resistance to detonation. ....... Octane number is not related to flame (burn) speed either. Variations in octane quality are independent of flame speed.

There are some high octane gasolines in the marketplace with fast flame
speeds and some with slow flame speeds."

Enjoy.

Michael,
I sugest you look at my next thread on this subject, you and another may learn about,

1- fuel burn times
2- timing
3- octane ratings to use for different compression ratios

This has very little to do with ENGINE MAGENMENT SYSTEMS, ( computers) just the 1971 and older that have to loose up to 20% of the HP they had when they were built by burning the octane rating that is so called 98 to the old standards.

performance is NOT driving your car in a parade, its turning in the high 11's not the 15's. That means seconds.

DOM

[Duke W.]

Re: 100vll

I have a decent body of empirical evidence on what maximum CRs various OE configurations can tolerate on modern gasollines, especially small blocks.

CRs are typically half a point lower than advertised, an most will operate on locally available premium fuels without modification. If anything, detailed preparation such as grinding chambers to minimize CR spread between cyliinders yields CRs that will work with all OE equivalent components.

Depending on locally available premium fuel octane (as low as 91, as high as 94) total WOT timing may have to be run a few degrees less than optimum, but three degrees less only reduces peak power about one percent.

In the real world of vintage Corvettes, low end torque is a lot more useful to owners than top end power. Fewer than one percent seriously race their cars.

As far as flame propagation speed goes, all other things equal, most blends of hydrocarbons that can be called "gasoline" burn at about the same speed. That's not my opinion. It's the result of 100-plus years of research.

The above applies to "normal combustion". However, if combustion is "abnormal" i.e. detonation, it's a whole other ballgame.

Duke

[Philip C.]

Re: 100vll

Phil,

I've been storing summer toys over the long Canadian winters since the late 60s. Conversely, I also store winter toys over the short Canadian summers. I've never once had problems at start up time and use straight pump gas, no Stabil. I understand that lawn equipment and their carbs with tiny passages might benefit from Stabil, but on cars, bikes snowmobiles it seems to be redundant.

For very long term storage, probably a drained and dry tank would be the best solution.

Hi Mike we here are talking about vintage (cars) corvettes, with fuel injection and old carbs. I leave off the fuel pump drive cables on my fuel cars (4) so I can turn the fuel pump by hand with a cable once a month to keep it from seizing and thats with 100 LL.The other carb cars (8) I have to start and still have to take one off once in a while to go thru. I have had rubber fuel lines eaten on my 2-cycle backpack blowers and other 2-cycle small engines that sit with sh&t pump gas. I dont use reg gas in them, I use middle grade because reg gas doesnt stay well mixed with the 2-cycle oil (I use only synthetic 2-cycle oil) I run them empty in the off season and still have some trouble with starting up. Phil 8063

[Clem Z.]

Re: 100vll

Phil,

I've been storing summer toys over the long Canadian winters since the late 60s. Conversely, I also store winter toys over the short Canadian summers. I've never once had problems at start up time and use straight pump gas, no Stabil. I understand that lawn equipment and their carbs with tiny passages might benefit from Stabil, but on cars, bikes snowmobiles it seems to be redundant.

For very long term storage, probably a drained and dry tank would be the best solution.

pumper carbs like used weed wackers and chain saws do not seem to be a problem but gravity filled carbs you should leave the fuel tank petcock open to keep refilling the carb with fresh gas as it evapoarates from the float bowl. some of these carbs the idle jet is as small as .015 and does not take much to get gummed up.