Knock solution; seems too simple? Gasoline questions
10-29-2018, 12:55 PM
#1
Three Wheelin'
Thread Starter
Knock solution; seems too simple? Gasoline questions
I have been chasing knocks recorded by bosch hammer for nearly a year. may seem like an obsession, but car has felt like timing is pulled
back and not at full power.
since my first post(s) I have done intake refresh with new CPS, hall, and knock sensors. new hoses and flappy actuator. temp ll, hoses, and vacuum
lines and connectors, and fuel pump(s). every "little" (lol) thing has made a difference, and all advice received here, and from roger, has help immensely.
sincere thanks for all the info and guidance. would have been a very difficult journey without this forum.
knocks have gone from high double digits, to single digits and this AM settling around 18.
about 100 miles from home, I stopped to fuel up, and the game has changed!! after the new fuel, and multiple high RPM, and high MPH runs, the car
consistently recorded 0, yup ZERO knocks. not being able to leave well enough alone, I made a few thrashing runs, with no mercy, shifts to redline, and
taking no prisoners. two runs recorded 1 knock and the final was 0!
hard to believe that gas could make all the difference, and makes me wonder, if the local Texaco, that I have been faithful to, is cheating?? if its all about octane,
perhaps the station I use is not serving up the 93 octane listed on the pump? I try to use Texaco because of the techroline additive, thinking this is a good thing.
Fill up today was at Shell.....there is no denying the difference is knocks and power.
researching gasoline companies and anti knock additives has not provided much good info. can anyone confirm that a specific brand of gasoline offers a better
type, or amount of anti knock compounds?
back and not at full power.
since my first post(s) I have done intake refresh with new CPS, hall, and knock sensors. new hoses and flappy actuator. temp ll, hoses, and vacuum
lines and connectors, and fuel pump(s). every "little" (lol) thing has made a difference, and all advice received here, and from roger, has help immensely.
sincere thanks for all the info and guidance. would have been a very difficult journey without this forum.
knocks have gone from high double digits, to single digits and this AM settling around 18.
about 100 miles from home, I stopped to fuel up, and the game has changed!! after the new fuel, and multiple high RPM, and high MPH runs, the car
consistently recorded 0, yup ZERO knocks. not being able to leave well enough alone, I made a few thrashing runs, with no mercy, shifts to redline, and
taking no prisoners. two runs recorded 1 knock and the final was 0!
hard to believe that gas could make all the difference, and makes me wonder, if the local Texaco, that I have been faithful to, is cheating?? if its all about octane,
perhaps the station I use is not serving up the 93 octane listed on the pump? I try to use Texaco because of the techroline additive, thinking this is a good thing.
Fill up today was at Shell.....there is no denying the difference is knocks and power.
researching gasoline companies and anti knock additives has not provided much good info. can anyone confirm that a specific brand of gasoline offers a better
type, or amount of anti knock compounds?
10-29-2018, 02:00 PM
#3
Three Wheelin'
Thread Starter
When did you last fill up with gasoline prior to today?
still in amazement, and near disbelieve, that poor gas has been my issue???
10-29-2018, 02:13 PM
#4
Rennlist Member
It is all about octane so that would be the logical conclusion. Testing for octane is not simple or cheap, and modern cars (including the 87+ 928s) all pull timing as needed to avoid knocking. So a customer, without some diagnostic equipment, would never know the difference.
10-29-2018, 02:20 PM
#5
Three Wheelin'
Thread Starter
It is all about octane so that would be the logical conclusion. Testing for octane is not simple or cheap, and modern cars (including the 87+ 928s) all pull timing as needed to avoid knocking. So a customer, without some diagnostic equipment, would never know the difference.
10-29-2018, 02:30 PM
#6
Rennlist Member
Well, all fuel comes from the same place, the difference will be additives for cleaning/etc. But cheating is very rare, the delivery drivers dump fuel into the tanks, and they are not tied to the station managers.
The knock you get, depend on where they are. Gunna need some logs, but I dont think hammer can do that. Sharktuner can.
10-29-2018, 02:35 PM
#7
Rennlist Member
The 928 is tuned for 98 RON which as I am aware is what your system refers to as 93 octane [RON+MON]/2. I have to run 95 RON and to avoid knocks that required pulling back a degree or two of advance- that or live with the knocks which are immediately [next firing stroke] corrected by the knock control system. That is how sensitive it is.
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10-29-2018, 02:48 PM
#8
Three Wheelin'
Thread Starter
Do the same test with the same fill when the tank is near empty and report back what you find.
beginning to understand about what is stated regarding octane, but do different brands add more or less of an anti knock additive, or is
that all marketing BS??
10-29-2018, 02:51 PM
#9
Rennlist Member
They do not. They add cleaning additives.
They are added -after- the tanker fills up with the base load, its all the same fuel, regionally, from the mostly same refinery.
10-29-2018, 03:09 PM
#10
Rennlist Member
Some refiners add proprietary cleaners to the petrol- no idea how many of them do or how effective they are- Texaco Chevron use their Techron additive for instance. There are no additives to increase octane rating- just different blending stocks. There is an irony however in that whereas the gasoline has to meet specific octane testing requirements as I am aware there is no measure of how much heat they liberate when combusted. Thus the E10 formulation has an octane rating of 93 but it also has a reduced energy output as the alcohol has a lowish heat of combustion compared to regular h/c based gasoline. Put another way, to get the same energy output burning alcohol you have to burn more of it- not a big deal with E10.
10-29-2018, 03:22 PM
#11
Three Wheelin'
Thread Starter
if you filled up this morning and immediately ran the car, tested it for knocks and it was better than previous tests it may well be that the fresh fill answers why rather than the brew.
10-29-2018, 03:25 PM
#12
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
https://www.sunocoracefuels.com/tech...w-octane-fuels
Octane Stability: High Octane vs Low Octane Fuels
Octane is the most talked about property when it comes to gasoline. It’s no surprise because selecting octane of gasoline is the only choice the consumer has, except what station to buy it from. In this article we will focus on octane stability of 87 and 93 octane pump fuels versus racing fuels and what you can do to prevent octane loss in your fuel.
It is necessary to briefly review what octane is in order to dive deeper into stability issues. At fueling stations in the United States, octane is typically displayed as a number, 87 through 93. This number is known as Anti-Knock Index (AKI). AKI is the average of Research octane number (RON) and Motor octane number (MON)(Totten). Essentially, these numbers provide a scale to measure how much heat and pressure can be put on the fuel before it spontaneously combusts. Spontaneous combustion is a source of engine knock which can quickly damage an engine. Octane ratings are important because different engines expose fuel to different amounts of pressure and heat. Engines must use the proper octane fuel to avoid knock and provide reliable operation.
A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.
87 octane fuels tend to be less refined and contain more unstable hydrocarbons. As the months pass during storage these unstable components react to form gums, varnishes and lower octane hydrocarbons. As a result the octane can decrease within months for 87 octane fuels, especially when stored under less than ideal conditions. 93 octane fuels are more refined and contain more stable hydrocarbons. These stable hydrocarbons can last 2-3 times longer than 87 octane fuel. Even in proper storage 87 octane gas can start to degrade in 3 months, 93 octane fuel should last closer to 9 months before degradation is noticeable. Keep in mind that 93 octane fuels are still susceptible to octane loss and vapor pressure decreases due to butane evaporation.
Octane stability in racing fuels is much different because fuel quality is valued more than production cost, unlike the pump gas industry where cost drives the majority of refining decisions. A large part of any quality race fuel is consistency. Race fuels are designed to be high in octane to allow for increased compression ratios and boost levels. In order to achieve high octane and consistent composition, pure chemical components are mixed with highly refined gasoline. The components used in Sunoco race fuels are very stable and can retain octane in excess of 2 years when properly stored. We have test results confirming octane stability in our unleaded, leaded, ethanol-free and ethanol fuels. The butane vapor pressure issue is addressed with the use of chemical components that boil around 80°F. The higher boiling point means vapor pressure decreases won’t be as common until the fuel is exposed to temperatures above 80°F.
Some high octane unleaded fuels, 260 GT Plus, and octane boosters contain the additive MMT. MMT is a very effective octane booster and doesn’t harm oxygen sensors or catalytic converters so, it is ideal for modern vehicles. Please note this additive is degraded by sunlight and can lose all octane boosting properties within minutes of exposure (L.Ter Haar). Degraded MMT will settle to the bottom of the container as a rust colored material that can clog fuel lines and filters. Extra care needs to be used when storing and handling MMT fuels in order to minimize contact with sunlight. The additive is stable in gasoline as long as no UV light hits the fuel. Sunoco 260 GT Plus is our only race fuel that contains MMT.
Octane stability is greatly affected by the storage conditions. Proper storage can preserve octane for years but improper storage can reduce octane and degrade fuel within weeks. That is why we provide proper storage information on our website. Click here to view our storage recommendations. http://www.sunocoracefuels.com/tech-...e-fuel-storage
Octane is the most talked about property when it comes to gasoline. It’s no surprise because selecting octane of gasoline is the only choice the consumer has, except what station to buy it from. In this article we will focus on octane stability of 87 and 93 octane pump fuels versus racing fuels and what you can do to prevent octane loss in your fuel.
It is necessary to briefly review what octane is in order to dive deeper into stability issues. At fueling stations in the United States, octane is typically displayed as a number, 87 through 93. This number is known as Anti-Knock Index (AKI). AKI is the average of Research octane number (RON) and Motor octane number (MON)(Totten). Essentially, these numbers provide a scale to measure how much heat and pressure can be put on the fuel before it spontaneously combusts. Spontaneous combustion is a source of engine knock which can quickly damage an engine. Octane ratings are important because different engines expose fuel to different amounts of pressure and heat. Engines must use the proper octane fuel to avoid knock and provide reliable operation.
A key aspect of gasoline stability is vapor pressure. This is determined by how much pressure builds up inside a sealed fuel container when the fuel is heated to 100°F. A higher vapor pressure suggests a higher concentration of low boiling point hydrocarbons that vaporize under 100°F. Pump fuels with high (12 pounds/square inch, psi) vapor pressures are used in cold weather to prevent engine starting issues due to low temperatures. Pump fuels are limited to 7.8-9psi maximum in warm weather depending on county and state (www.epa.gov). If stored in a vapor tight container the vapor pressure can be maintained for long periods of time. Fuel exposed to the atmosphere can lose light components within a couple of days. Over time as vapor pressure decreases the fuel can become stale. Stale fuel doesn’t evaporate as easily and can cause rough engine idle and hard starting. Butane is a volatile gasoline component used to tailor vapor pressure in accordance with seasonal needs. Cold weather fuel has higher concentrations of butane. Butane has a high blending octane value which helps manufacturers hit their octane targets. The main downfall of butane is that it boils at 32°F. If the fuel tank is vented to atmosphere the butane can start to evaporate out unless the daily temperatures are below freezing. This makes cold weather fuel more susceptible to vapor pressure loss and octane decreases.
87 octane fuels tend to be less refined and contain more unstable hydrocarbons. As the months pass during storage these unstable components react to form gums, varnishes and lower octane hydrocarbons. As a result the octane can decrease within months for 87 octane fuels, especially when stored under less than ideal conditions. 93 octane fuels are more refined and contain more stable hydrocarbons. These stable hydrocarbons can last 2-3 times longer than 87 octane fuel. Even in proper storage 87 octane gas can start to degrade in 3 months, 93 octane fuel should last closer to 9 months before degradation is noticeable. Keep in mind that 93 octane fuels are still susceptible to octane loss and vapor pressure decreases due to butane evaporation.
Octane stability in racing fuels is much different because fuel quality is valued more than production cost, unlike the pump gas industry where cost drives the majority of refining decisions. A large part of any quality race fuel is consistency. Race fuels are designed to be high in octane to allow for increased compression ratios and boost levels. In order to achieve high octane and consistent composition, pure chemical components are mixed with highly refined gasoline. The components used in Sunoco race fuels are very stable and can retain octane in excess of 2 years when properly stored. We have test results confirming octane stability in our unleaded, leaded, ethanol-free and ethanol fuels. The butane vapor pressure issue is addressed with the use of chemical components that boil around 80°F. The higher boiling point means vapor pressure decreases won’t be as common until the fuel is exposed to temperatures above 80°F.
Some high octane unleaded fuels, 260 GT Plus, and octane boosters contain the additive MMT. MMT is a very effective octane booster and doesn’t harm oxygen sensors or catalytic converters so, it is ideal for modern vehicles. Please note this additive is degraded by sunlight and can lose all octane boosting properties within minutes of exposure (L.Ter Haar). Degraded MMT will settle to the bottom of the container as a rust colored material that can clog fuel lines and filters. Extra care needs to be used when storing and handling MMT fuels in order to minimize contact with sunlight. The additive is stable in gasoline as long as no UV light hits the fuel. Sunoco 260 GT Plus is our only race fuel that contains MMT.
Octane stability is greatly affected by the storage conditions. Proper storage can preserve octane for years but improper storage can reduce octane and degrade fuel within weeks. That is why we provide proper storage information on our website. Click here to view our storage recommendations. http://www.sunocoracefuels.com/tech-...e-fuel-storage
10-29-2018, 03:33 PM
#13
Three Wheelin'
Thread Starter
10-29-2018, 03:47 PM
#14
Rennlist Member
Although you are recording knock counts do you actually hear anything untoward going on? I used to pick up some knocks on ST2 but if I had not been using such I would never have known anything was going on. A friend of mine over here had a new GTS back in 1993 and that thing used to knock like a hammer on wood. My guess is you are not actually hearing anything- correct? If so, probably nothing to worry about.
10-29-2018, 03:52 PM
#15
Vegas, Baby!
Rennlist Member
Rennlist Member
The gas is the same in the pipeline that comes to the storage tanks at the racks where our trucks load for deliveries to the stations. The base gas is 84 octane for regular before the alcohol is added to raise the octane rating to 87 octane. Almost all gasolines have 10% alcohol added, determined by region and local laws, the only difference is the additive added by brand. All the blending is automated at the rack when the tanker is loaded. Alcohol first then the gasoline. All the trucks load from the bottom of the tanker. The loading racks have brand segregation, and most of the racks are community loading. In other words Chevron/Texaco products are loaded on a designated rack as is Shell, ARCO, etc. The other brands like you buy at Costco, is from a community loading rack. The different additives and whether it's a top tier gasoline, is determined by the additives. Mid grade is 89, premium is 91 to 93.
Shell V-Power ranges from 91 to 93 octane both with or without ethanol. It just varies from station, and it's up to the station owner whether or not to sell pure gas, providing he has that option. Because of the emission laws, it's rare for a station owner to order pure gas, but there are still a few that may be able to purchase pure gas. There are a couple of stations here in Las Vegas, where you can buy pure gas, and racing fuel, which is aviation fuel, it has the color additive, and will discolor if water is present in the fuel, it also has a lean mixture rating of 100 octane, and a rich mixture rating of 130, for supercharger pressures without detonation.
There is a rack outside of Vegas that is adding butane to it's winter blend gasoline.
FWIW, the price changes everyday at 6pm. The brokers buy the gas for the next days deliveries after 6, and customers are informed of the price changes by email. A few years ago we were loading our tankers in Tucson, Arizona, over 300 miles from Vegas due to the gas being 20 cents a gallon cheaper than we could buy it for wholesale in Nevada. The taxes change as soon as it crosses the state lines in the pipeline. We were still saving over a grand per load, with driver pay/per diem, and transportation costs.
We also haul a lot of transmix. Transmix is a combination of diesel and gasoline, when the refinery changes pumping products. Everything gets mixed up, and has to be re refined to separate the products. There are sensors that will divert the transmix to a storage tank, till pure product is charged in the pipeline. The fuels are cooked and the gas returns to vapor where it's condensed back to liquid and the diesel is heaver and flows out the bottom of the cracking tower. Nothing ever goes to waste. Even gas that's degraded in storage can be re refined and contaminates removed.
Shell V-Power ranges from 91 to 93 octane both with or without ethanol. It just varies from station, and it's up to the station owner whether or not to sell pure gas, providing he has that option. Because of the emission laws, it's rare for a station owner to order pure gas, but there are still a few that may be able to purchase pure gas. There are a couple of stations here in Las Vegas, where you can buy pure gas, and racing fuel, which is aviation fuel, it has the color additive, and will discolor if water is present in the fuel, it also has a lean mixture rating of 100 octane, and a rich mixture rating of 130, for supercharger pressures without detonation.
There is a rack outside of Vegas that is adding butane to it's winter blend gasoline.
FWIW, the price changes everyday at 6pm. The brokers buy the gas for the next days deliveries after 6, and customers are informed of the price changes by email. A few years ago we were loading our tankers in Tucson, Arizona, over 300 miles from Vegas due to the gas being 20 cents a gallon cheaper than we could buy it for wholesale in Nevada. The taxes change as soon as it crosses the state lines in the pipeline. We were still saving over a grand per load, with driver pay/per diem, and transportation costs.
We also haul a lot of transmix. Transmix is a combination of diesel and gasoline, when the refinery changes pumping products. Everything gets mixed up, and has to be re refined to separate the products. There are sensors that will divert the transmix to a storage tank, till pure product is charged in the pipeline. The fuels are cooked and the gas returns to vapor where it's condensed back to liquid and the diesel is heaver and flows out the bottom of the cracking tower. Nothing ever goes to waste. Even gas that's degraded in storage can be re refined and contaminates removed.
Last edited by polecat702; 10-29-2018 at 04:13 PM.