High octane fuel.
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ctmccloskey (02-27-2019)
02-26-2019, 09:21 PM
#22
Le Mans Master
02-26-2019, 09:21 PM
#23
Le Mans Master
02-27-2019, 01:02 AM
#24
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St. Jude Donor '05
Put a tank of pump and a can of Torco in it thats more than enough.
Or Wild Bills Supreme Octane 100...if you have cats know that stuff has lead in it.
Or Wild Bills Supreme Octane 100...if you have cats know that stuff has lead in it.
02-27-2019, 05:28 AM
#25
Safety Car
Correct, which means spontaneous combustion due to heat and pressure causing the remaining fuel to explode and not burn at a controlled rate. The spontaneous combustion causes a shock wave and that is what you hear as knock.
02-27-2019, 08:17 AM
#26
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Royal Canadian Navy
Everything you wanted to know about octane rating and effects:
https://en.wikipedia.org/wiki/Octane_rating#Effects
https://en.wikipedia.org/wiki/Octane_rating#Effects
02-27-2019, 12:45 PM
#27
Burning Brakes
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Interesting, I got my but kicked by the octane experts when I talked about burn rate. This makes me feel better that it is addressed. Wish I had help back then. The worst I was called in a post was a pea brain.
Dom
Dom
02-27-2019, 06:31 PM
#29
Le Mans Master
Dynamic compression (utilizing cam events)
chamber design
head/block material
engine coolant temps
intake temps
All of this dictates what an engine can handle and with what fuel. Just being 11.0-1 means nothing. There are modern engines with 12.0-1 compression that run fine on 87 octane.
On our old school, iron head motors with dome pistons etc, its probably a good idea to run some race fuel if your true measured compression ratio is 11.0-1 and running a stock-ish cam etc... as they were designed to run on 100+ octane leaded fuel...definitely an added safety factor, but slapping some 110 in a stock L71/L78 isn't just gonna add power.
02-27-2019, 06:46 PM
#30
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Ethanol blends can cause premature failure of some soft parts in the fuel system (hose, fuel pump/carb rubbers, etc.) and I've heard plenty of stories though personally I've never had a problem.
10% ethanol content also reduces fuel efficiency a little as ethanol has a lower heat capacity (basically available energy per pound) than gasoline. Generally not an issue with our antiques. Most of our carbs are jetted on the rich side, and some ethanol fuel reduces the gasoline content but increases the oxygen content for a better A/F ratio. E85 is something like 25% less efficient than straight up gas.
On a side note there was a (maybe still is) a trend of guys building motors to run on E85 to take advantage of it's high octane rating at lower cost than race fuel. I've never had much interest in building a motor that I can't get gas anywhere/anytime so haven't paid much attention to that genre and don't honestly know how successful guys have been.
Anyway, more on topic. As already stated octane is a measure of burn rate No. with higher being slower. Not necessarily. High compression engines need slower burn rates No. Slower burn rates reduce the engine's efficiency by increasing the number of crankshaft degrees that the piston is moving up against the additional cylinder pressure caused by lighting off the mixture earlier due to having to advance the timing to make up for a slower burning fuel. due to ignition by compression (the basic theory of diesel engines). If the fuel burns too quickly you'll get pre-ignition also called detonation or spark knock. Pre-ignition and detonation are NOT the same thing. Pre-ignition happens before the spark/TDC, and detonation happens after the spark/TDC. Pre-ignition is caused by hot spots in the chamber or on the piston, and detonation is caused by high pressure/hot mixtures at the tail end of the flame front.
If you're getting detonation, short of actually going through the hassle of lowering CR, you can dial back timing a degree or three and/or switch to a higher octane fuel. That will solve most street driven motor detonation issues.
Also as stated, the comments from the speed shop guys on ethanol is utter nonsense. Probably talks about 3/4 race cams and high nickle blocks too.
In broad strokes: For a street driven, naturally aspirated motor run as much timing with as little octane as possible. Detonation is the limit on both.
10% ethanol content also reduces fuel efficiency a little as ethanol has a lower heat capacity (basically available energy per pound) than gasoline. Generally not an issue with our antiques. Most of our carbs are jetted on the rich side, and some ethanol fuel reduces the gasoline content but increases the oxygen content for a better A/F ratio. E85 is something like 25% less efficient than straight up gas.
On a side note there was a (maybe still is) a trend of guys building motors to run on E85 to take advantage of it's high octane rating at lower cost than race fuel. I've never had much interest in building a motor that I can't get gas anywhere/anytime so haven't paid much attention to that genre and don't honestly know how successful guys have been.
Anyway, more on topic. As already stated octane is a measure of burn rate No. with higher being slower. Not necessarily. High compression engines need slower burn rates No. Slower burn rates reduce the engine's efficiency by increasing the number of crankshaft degrees that the piston is moving up against the additional cylinder pressure caused by lighting off the mixture earlier due to having to advance the timing to make up for a slower burning fuel. due to ignition by compression (the basic theory of diesel engines). If the fuel burns too quickly you'll get pre-ignition also called detonation or spark knock. Pre-ignition and detonation are NOT the same thing. Pre-ignition happens before the spark/TDC, and detonation happens after the spark/TDC. Pre-ignition is caused by hot spots in the chamber or on the piston, and detonation is caused by high pressure/hot mixtures at the tail end of the flame front.
If you're getting detonation, short of actually going through the hassle of lowering CR, you can dial back timing a degree or three and/or switch to a higher octane fuel. That will solve most street driven motor detonation issues.
Also as stated, the comments from the speed shop guys on ethanol is utter nonsense. Probably talks about 3/4 race cams and high nickle blocks too.
In broad strokes: For a street driven, naturally aspirated motor run as much timing with as little octane as possible. Detonation is the limit on both.
02-27-2019, 07:05 PM
#31
Safety Car
I run 12.25-1 Compression Ratio on my 1968 Corvette with it's 427. I have been driving with this compression ratio for many years and even traveled with it. I do not have a problem with detonation nor ever have with this engine. In the old days Compression meant "power" so I basically did my research on which cylinder head to use (as I could not afford the aftermarket aluminum in the early 1990's). I chose a Closed Chamber Cylinder head made by GM used on several applications of Big Blocks both 396 and the 427's. My chamber is only 100.3 cc and the pistons fit into the pockets in the heads. These cylinder heads resist detonating far more than the newer style Open Chamber Cylinder head. Unfortunately for me they are made of cast Iron but they have had larger valves and some professional Porting work.
I have tried it all at one time or another in the name of preventing detonation, I installed an MSD Knock Sensor to monitor the engine. I used all sorts of race fuels and they are just too expensive to use everyday. I like driving my Corvette and I love the sound it makes when pushed a bit.
Snow Performance makes a nice Water/Methanol Injection system which I have tested on my engine with success. By the end of this winter my water/methanol injection system will be using -4AN SS Braided fuel lines from it's tank to the injector. Using windshield washer fluid in a tank in my rear section I get the equivalent of 116 Octane fuel. My 427 likes this stuff and especially while the motor is under load and accelerating. The injection system also cools down the combustion a bit with the water. My ignition system has been beefed up to handle lighting off the mixture after squeezing the heck out of it. I am using a MSD Distributor and a MSD 6al ignition box and their hot coil. I will be installing a J&S Safeguard Timing control box this spring. This will allow my engine to retard a particular cylinder without the entire engine making less power.
The lesson on Octane is a tough pill for some out there. I love watching people with stock Civics putting 93 octane in their car, sadly it happens way too often. About 6 years ago I drove across this great country of ours and I was surprised to find 100 octane gasoline at stations along the interstates. Where I live they sell us this 10% ethanol stuff and call it "gasoline". Then the stations who sell real 100% gasoline charge a premium for it, it should be cheaper as the ethanol costs more than gasoline and is used in addition.
There are ways of living with High Compression, it can be very rewarding if done right. Race Fuel is not the only solution to cars with higher compression. Technology has come to the rescue! I guess those 13 quarts of Tetra-ethyl Lead might go to waste.
Good Luck and ONLY buy the amount of octane you REALLY need.
I have tried it all at one time or another in the name of preventing detonation, I installed an MSD Knock Sensor to monitor the engine. I used all sorts of race fuels and they are just too expensive to use everyday. I like driving my Corvette and I love the sound it makes when pushed a bit.
Snow Performance makes a nice Water/Methanol Injection system which I have tested on my engine with success. By the end of this winter my water/methanol injection system will be using -4AN SS Braided fuel lines from it's tank to the injector. Using windshield washer fluid in a tank in my rear section I get the equivalent of 116 Octane fuel. My 427 likes this stuff and especially while the motor is under load and accelerating. The injection system also cools down the combustion a bit with the water. My ignition system has been beefed up to handle lighting off the mixture after squeezing the heck out of it. I am using a MSD Distributor and a MSD 6al ignition box and their hot coil. I will be installing a J&S Safeguard Timing control box this spring. This will allow my engine to retard a particular cylinder without the entire engine making less power.
The lesson on Octane is a tough pill for some out there. I love watching people with stock Civics putting 93 octane in their car, sadly it happens way too often. About 6 years ago I drove across this great country of ours and I was surprised to find 100 octane gasoline at stations along the interstates. Where I live they sell us this 10% ethanol stuff and call it "gasoline". Then the stations who sell real 100% gasoline charge a premium for it, it should be cheaper as the ethanol costs more than gasoline and is used in addition.
There are ways of living with High Compression, it can be very rewarding if done right. Race Fuel is not the only solution to cars with higher compression. Technology has come to the rescue! I guess those 13 quarts of Tetra-ethyl Lead might go to waste.
Good Luck and ONLY buy the amount of octane you REALLY need.
02-27-2019, 07:40 PM
#32
Burning Brakes
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Most people, if ALL never used high octane fule!!! They profess the lower octane to feed their needs and not use the rated HP the car was to have.
SORRY,you will loos a race if you would ever do it. Grandma drivers.
Dom
SORRY,you will loos a race if you would ever do it. Grandma drivers.
Dom
02-28-2019, 01:00 PM
#33
Burning Brakes
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NOW I am going back to the 50's when they had 2 long glass tubes. One had a few drops of low octane and the other high octane. The low beat the high to the end of the tube when ignited by the same source! That was or lesson as to using the octane the engine was designed to use. That was back then and they actually had pistons out of a car that used a low octane. They were damaged on top.
On the other hand I don't want to go to jail for display, but I do get crazy coming out of the parking lot late a night where I can see a half mile in either direction.
One night I took the old vette out to show a younger what he was missing. I didn't check the tire pressure and one in the rear was low. When I power shifted into 2nd the vette went sideways and took out a few taxi way lights.
Dom
02-28-2019, 01:34 PM
#34
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St. Jude Donor '05
dom has a point..how many threads do we see with "I got this much hp" but put the cheapest pee gas they can in it. Esp a brand new engine never figured out that one
jbsblownc5 is a torco dealer here, hit him up for Torco delivered to your front door.
jbsblownc5 is a torco dealer here, hit him up for Torco delivered to your front door.