Benefits of running premium...

[Beowulf]

Again - if anyone has experience to share on how to advance the timing, please pass it along.

This article explains how to advance the timing on the 1FZ-FE.

I am curious on your explanation of what is happening during the pinging. I am not challenging your explanation but I would appreciate knowing where you got the information or, if you are an expert in the field. Thanks.

-B-

 

[Buckru]

Are there any long term negative effects of an advanced timing (engine wear, etc)? How has advanced timing affected gas mileage?

As I am currently running 35's on stock gearing, a little more power down low would be beneficial for me. Regearing is coming, but I have a few other mods to complete first.

Buck Buchanan

 

[NaterGator]

I'm pretty damn sure pinging is primarily caused by predetonation and not by an irregular flame front....

 

[CJF]

I'm pretty damn sure pinging is primarily caused by predetonation and not by an irregular flame front....

Where's your data for that?

I did some serious looking around a while back, and most sources agree that true pre-detonation is quite rare.

Curtis

 

[SteveH]

The Feds require all octane levels of gas to have 'deposit control' additives, due to consumer confusion years about about 'premium' gas that was supposed to keep your engine clean. Some fuels have more addtitives, but all have some.

A good discussion about octane and fuel issues is located at: http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/8_q-a/#6
No affiliation - and it seems unbiased, in spite of it being an oil company page.

Steve

 

[NaterGator]

Where's your data for that?

I did some serious looking around a while back, and most sources agree that true pre-detonation is quite rare.

Curtis

There you go, from the Chevron site even:

8. What is knocking?
Spark knock is the sound of abnormal combustion. When combustion in a spark-ignition internal combustion engine is initiated by a spark, the flame front should fan out from the spark plug and travel across the combustion chamber rapidly and smoothly. If the last part of the air-fuel mixture ignites spontaneously (autoignites) before the flame front arrives, the sudden jump in the pressure in the cylinder creates the characteristic knocking or pinging sound. Knocking occurs because the octane of the gasoline is below the antiknock requirement of the engine at that moment.

 

[RavenTai]

No affiliation - and it seems unbiased, in spite of it being an oil company page.

That is one of the many things I like about Chevron, they provide a lot of technical data about their products. There is one near my house so I use mainly chevron gas.

As to irregular flame fronts, detonation could be described as an irregular flame front or multiple flame fronts. I think the difference is just semantics. regardless we are looking for a smooth ramp up in pressure that can best match the mechanical advantage of the crank and the expanding volume of the cylinder that it lives in, a very fast burn causes stress on the engine in extreme can lead to damage and power is lost as the best power comes from a sustained push on the piston not a short hammer like impact.

 

[NaterGator]

Agreed... however calling it a flame front issue makes it sound like the fuel burns 'top down' but at different rates. In reality the pressures in the cylinder cause the fuel to predetonate, thus the spark is retarded to compensate.

Also, unless timing advance is present using higher octane fuel to fix pinging is a band-aid to the real problem and I am a firm believer that it increases soot on the combustion chamber. You need to run the fuel the engine was designed to run and fix the pinging, not change the fuel, if you have a problem.

My $0.02.

 

[CJF]

There you go, from the Chevron site even:

Are you supporting your viewpoint or mine?

Like Raven says, probably just semantics. What I meant to classify as very rare is actual pre-spark spontaneous combustion.

Curtis

 

[NaterGator]

Hrm. Hard to say

I'm saying that a perfectly even "top down" flame front is not as important as a single flame front. I agree that the spark and subsequent increases in pressure in the cylinder cause the secondary det... it's not as if a single irregularly shaped flame front is causing the spark knock.

I'm disagreeing with this bit:

A more uniform explosion in the combusion chamber that starts in the center at the spark plug and spreads out uniformly at the same rate in all directions prevents torqueing the piston, and results in a "centered punch" on the top of the piston. The pinging noise that we hear if a car is pinging is either the piston being torqued, or a non-uniform "punch" on the piston as it is still travelling up to top dead center.

 

[SUMOTOY]

When I worked at Lexus, we did a study that determined premium gas has a better additive package and produced less cylinder deposits over a typical ownership cycle (3 years). So we opted to require premium fuel for all Lexus vehicles to reduce durability and reliability issues. Translation: Get the customer to use premium and you'll have fewer drivability complaints. Since this literally means my vehicle will benefit over a long life, I use premium frequently though I don't claim power advantages unless it's under heavy duress usage like towing on a hot day. So, don't buy it for power advantages but there's evidence your engine will benefit from the cleaner burn and fewer engine deposits of premium fuels. Personally, I think using 87 all the time but strictly from top shelf fuel brands like Chevron will provide similar benefits over always using crap 7-11 gas or grocery store gas.

DougM

I agree with this, I have run premium in every vehicle I owned in 20 years. It's just not that big of a deal to me. Remember too, the base stock for gasoline has all the brando trucks pulling from it as 86 octane. Then the truck goes over to his corner of the depot, and adds in the additives that makes it Chevron 93, texaco 89 etc.

It's also pretty well known in the industry that Shell has the highest consistent octane rating for premium (at 91.5 IMS) because they use separate trucks to transport premium fuel. I don't use regularly use shell myself, but that was the information I gleaned from my bro at Amoco oil. You mix 93 with 87 that was in there last time, it's something less than 93.

The side benefit from running premium (before I got my SC) was that the base timing is very conservative on the 80, so you can get more performance by running premium and tweeking up the baseline timing (procedure is in the FAQ's IMS). You might as well get the performance when you spend the money.

Edit: Found the procedure
http://www.safari4x4.com.au/80scool/tech/timing.html

HTH

ST
94 FZJ80 Supercharged

 

[sdbrassfield]

The Feds require all octane levels of gas to have 'deposit control' additives, due to consumer confusion years about about 'premium' gas that was supposed to keep your engine clean. Some fuels have more addtitives, but all have some.

A good discussion about octane and fuel issues is located at: http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/8_q-a/#6
No affiliation - and it seems unbiased, in spite of it being an oil company page.

Steve

Correct. All the fuel that comes from the refinery to the bulk terminals for delivery to transports and then your store is the same. The fuel types (gasoline/diesel/low and hi sulfur products) are delivered in slugs, seperated by slugs of water, up the pipelines to the bulk terminals which usually split the products. Your unbranded products are actually branded product that are sold as unbranded fuel. Its the same stuff folks. All gasolines (unbranded and branded fuel) sold at the terminals for delivery are then required to have a certain minimum percentage of detergent additives that frankly, are designed to do the job. The same oxygenates and octane enhancers are added to either fuel. The product we sell at the 23 unbranded locations my employer operates comes from either the Phillips 66 or BP/Amoco terminals. We have Exxon and BP branded locations too...

The branded fuel folks (Exxon, Shell, Chevron, BP) then add there little squirt of proprietary mixture (perfume) to the fuel at the loading rack to sell as their products (eg. chevron w/ techron). They can then market their fuel and say it is better. It likely is not, as it is the same fuel. Your unbranded products came from the same batch. There may be advantages using a branded fuel, if there are, they are only minute, if any at all.

The deciding factor is more the history of the tank you are buying the gas from. You would be suprised what has been found in those tanks...If you have good luck buying your fuel from a certain location and have had good results, stick with it...

 

[tech_dog]

On the preignition vs. flame front discussion, I don't think the shape of the flame matters for beans if the timing is wrong.

Preignition has got to be the big problem, and a nice symetric flame distribution more of a fine tuning parameter.

Since my 80's engine was designed for 87, and since I do not have any problems with preignition with 87, I see zero benifit in buying a gasoline designed to solve a problem I'm not having.

I buy top tier brands only for the quality and detergents, but I'll save the higher octane fuel for my other vehicles with higher compression.

 

[NaterGator]

Here is a good article on premium
http://www.sciam.com/article.cfm?chanId=sa003&articleId=373086C9-E7F2-99DF-385F3705197C1D4F

And!

Knock occurs when the compression of the fuel and air mixture alone, and not the spark plug, sets off an explosion. This results in a very loud noise and a lot of vibrations in the engine itself; "it's very bad for engines mechanically," Shepherd notes, driving the piston down before it has reached the top of its cycle.

 

[OZCAL]

...Gasoline?

Are there any?

...

More frequent flyer points!

 

[CJF]

And!...

So?

Are you going with that explanation now instead of the one you quoted in post #26, or what?

 

[NaterGator]

They both say essentially the same thing?

 

[chacoetaco]

Borrowed from poster on Tundrasolutions who wrote up a nice explanation on Octane ...

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

 

[DTAYLOR]

Curtis,

What - that I own the fastest normally aspirated 4.5L 80 on the planet??

DougM

For now, my friend. Just wait till Crushr comes back to life!

On the octane issue, I agree with Doug. My experience tells me all gasoline engines run better on higher octane. My father in law is a chemist retired from Shell Oil. He tells me the same thing that Doug is saying came out of their R&D department.

When you get right down to it, our 80s were not "built" to run on low octane, rather "marketed" as such. This is a common practice with many manufacturers. Cheaper to run=easier to sell.

I've had the same experience with Harley, and Honda motorcycles. The manufacturer advertises low octane recommendations, then the dealer's own service manager tells you the truth, because he has to deal with performance issues for a living.

Same experince with Kubota, Honda, Koehler powered mowers, Mercury boat motors, and other power equipement. They all run better and cleaner on high octane.

In every real life experience I've had with gasoline engines this has been the case.

I have never understood the rationale behind buying a luxury 4X4 that is not fuel milage oriented, then skimping on gas, maintenance, repairs, or any related expense. Just look at all the expensive mods we all do.

Thank God I am past driving a gas milage Civic or Tercel with plastic floor mats, vinyl seats, bycicle tires, and a stingy washing machine engine!

rant over for now..

 

[agomez]

no pinging.......