100 octane makes a big difference
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Early Big blocks and small blocks are two completely different animals when you talk about compression ratio and octane. Cannot compare. My 390 hp 427 runs a lot stonger and it runs cooler, smoother and get this... gas mileage went from 11 mpg up to almost 17 mpg when I began using a product called Max lead 2000. They have a web site. 1 pint per 20 gallons will bring 93 Amoco up to about 102. The stuff cost about $8 per quart and contains real tetraeythlelead. WAY cheaper than 104 pump gas.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
comp, nitro does not add compression, compression is a mechanical engine property resulting out of the stroke, valve events & intake/exhaust efficiency. The nitrous only comes into play when the burning has started, the N2O molecules are broken apart and the oxygen released will aid the burn (w/ more fuel added), this all happens very quickly as the moleculs all dissect at the same temperature (someone care to look it up in deg. F?), the result is a violent increase in cylinder pressure under combustion.
Instructor
Joined: Apr 2004
Posts: 106
Likes: 0
From: Norfolk VA
Originally Posted by yellow 72
I've been experimenting the other way. From the start I've been running 93 octane in my 10-1 aluminum headed 350 with 37* total timing with no ping ever. So I have been using 87 and still no ping at any throttle any rpm. It proves you can run a lot more comp with aluminum heads and enough cam duration 
Todd
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Quote:
Originally Posted by yellow 72
I've been experimenting the other way. From the start I've been running 93 octane in my 10-1 aluminum headed 350 with 37* total timing with no ping ever. So I have been using 87 and still no ping at any throttle any rpm. It proves you can run a lot more comp with aluminum heads and enough cam duration
Originally Posted by yellow 72
I've been experimenting the other way. From the start I've been running 93 octane in my 10-1 aluminum headed 350 with 37* total timing with no ping ever. So I have been using 87 and still no ping at any throttle any rpm. It proves you can run a lot more comp with aluminum heads and enough cam duration
Team Owner
Joined: Jul 2004
Posts: 40,354
Likes: 787
From: Redondo Beach, California
If you're going to talk about "pinging," I believe you have to talk about more engine variables than just octane rating and compression ratio. Engine vacuum and cam overlap are also important players as to whether or not you're to get pinging. At low engine rpm, cam overlap will act to decrease effective compression ratio. As the piston comes up on the compression stroke, cam overlap will allow the piston to push some of the air/fuel out of the cylinder chamber. This effect is pronounced at low engine rpm when the upward moving piston is traveling relatively slow. When the exhaust valve does close at these low engine rpm episodes, there's just less air/fuel and the effective compression ratio is lessened. Similarly at low engine rpm, if you're just cruising with the carb throttles near idle, engine vacuum is high and once again there's less air/fuel to be compressed.
My L88 piece part built engine with 11.5:1 compression (pistons decked from 12.5:1), the L88 cam, did not ping with "bad" gasoline if I accelerated slow. My 3.08:1 rear end ratio kept engine rpms low cruising at street speeds.
My L88 piece part built engine with 11.5:1 compression (pistons decked from 12.5:1), the L88 cam, did not ping with "bad" gasoline if I accelerated slow. My 3.08:1 rear end ratio kept engine rpms low cruising at street speeds.
Safety Car
Joined: Oct 2004
Posts: 4,512
Likes: 0
From: Self-Governing
Am I confused?
I thought that octane rate equated to burn temperature, not burn speed. ie. the lower the octane rating the lower temperature the fuel will combust.
The resulting knock or ping from using lower octane fuel is due to pre-ignition also known as dieseling. Higher compression engines create a tremendous amount of heat while compressing the air and fuel. When enough heat is generated from compression the mixture can combust prior to reaching TDC, resulting in knocking or pinging.
...but what do I know I am just an ignoramous...
Yes, JP5, kerosene, K1, diesel, and fuel oil are very similar in chemical composition and all have huge octane rates 130 to 150+ although I would not recommend using them to boost the octane in your vette!
Also I think there is some confusion in the discussions about nitro-methane and nitrous-oxide in this thread.
Anybody know the octane rate of nitro-methane?
I thought that octane rate equated to burn temperature, not burn speed. ie. the lower the octane rating the lower temperature the fuel will combust.
The resulting knock or ping from using lower octane fuel is due to pre-ignition also known as dieseling. Higher compression engines create a tremendous amount of heat while compressing the air and fuel. When enough heat is generated from compression the mixture can combust prior to reaching TDC, resulting in knocking or pinging.
...but what do I know I am just an ignoramous...
Yes, JP5, kerosene, K1, diesel, and fuel oil are very similar in chemical composition and all have huge octane rates 130 to 150+ although I would not recommend using them to boost the octane in your vette!
Also I think there is some confusion in the discussions about nitro-methane and nitrous-oxide in this thread.
Anybody know the octane rate of nitro-methane?
Melting Slicks
Joined: Apr 2000
Posts: 3,341
Likes: 6
Originally Posted by ignoramous1
Anybody know the octane rate of nitro-methane?
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Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Octane number is the anti-knock properties of a given fuel. To confuse things here in the US we use the R+M over (divided by) 2. Research octane is the properties in an engine at cruise and Motor octane is in the engine under load. I may have that reversed but you get the idea. Now brand "A" may arrive at 93 octane by averaging R90/ M96, whlie brand "B" may use R96 /M90. That is why one fuel may work in your particular set up but not in someone else's. I have a Huge four part doc. on everything you ever want to know about gasoline. I will send it to anyone wanting it. It is a very technical but understandable and informative. It has a question answer format so you can find what you want easily or just read the whole paper if you are bored
Drifting
Joined: Aug 2003
Posts: 1,327
Likes: 16
From: Fl
Larry,
Could you send me the paper on gasoline ...
My email is: bill.chamberlain@onetechplace.com
Thanks,
Bill
Could you send me the paper on gasoline ...
My email is: bill.chamberlain@onetechplace.com
Thanks,
Bill
Intermediate
Joined: Nov 2003
Posts: 41
Likes: 0
From: Blacksburg va
I here all this talk of high octane being 93 and 104....boring.
If it's high octane it has to be 110 or nothing. These old engines love the lead. Unfortunately the emissions don't like it, but who needs emissions.
You can smell me coming a mile away
mmmm lead...
If it's high octane it has to be 110 or nothing. These old engines love the lead. Unfortunately the emissions don't like it, but who needs emissions.
You can smell me coming a mile away
mmmm lead...
Drifting
Joined: Sep 2003
Posts: 1,325
Likes: 6
From: FRANKLIN GA
I agree that all 93 octane is not the same. I can run without pinging (with the timing retarded a little) on Amoco, Cheveron, or BP but it will ping like crazy on Citgo or Racetrac 93. Which leads me to believe that you do get what you pay for.
At the track I run VP 110 unleaded (and can dial the timing back up) and I can see a .20 difference in my timeslip. I've ran it both ways to see the difference.
At the track I run VP 110 unleaded (and can dial the timing back up) and I can see a .20 difference in my timeslip. I've ran it both ways to see the difference.