which octane gas do you put?

[Tripped1]

Originally Posted by Enzo_Guy

If you would like to explain how ignition and valve timing pertain to helping a high compression motor burn lower octane fuel, I (and likely a few other members reading this thread) would certainly like to learn about the subject.

Dynamic compression for one.

You can run the Chevy small block head at 11.5:1 STATIC compression on 89 (I have for that matter) assuming to do a little math and get the Dynamic compression right.

Because nothing is prefect the piston is already moving upward on the compression stroke BEFORE the valve is actually closed. This is important because static compression is really just crap for impressing wannabe motorheads at the bar. DYNAMIC compression is the only compression that a running engine ever sees. The conventional logic is that with a 8.5:1 DCR (V8) it really doesn't matter what your static is, this is also why you see some aftermarket cams that recommend at least 11:1 CR for installation, they know the intake valve close late and need to be compensated for.

By 70 small block V-8 logic every one of our bikes would be running on methanol. My Daytona has something like a 13.7:1 compression ratio. Again it doesn't matter.

[Enzo_Guy]

Originally Posted by Tripped1

Dynamic compression for one.

You can run the Chevy small block head at 11.5:1 STATIC compression on 89 (I have for that matter) assuming to do a little math and get the Dynamic compression right.

Because nothing is prefect the piston is already moving upward on the compression stroke BEFORE the valve is actually closed. This is important because static compression is really just crap for impressing wannabe motorheads at the bar. DYNAMIC compression is the only compression that a running engine ever sees. The conventional logic is that with a 8.5:1 DCR (V8) it really doesn't matter what your static is, this is also why you see some aftermarket cams that recommend at least 11:1 CR for installation, they know the intake valve close late and need to be compensated for.

By 70 small block V-8 logic every one of our bikes would be running on methanol. My Daytona has something like a 13.7:1 compression ratio. Again it doesn't matter.

Good point about static compression vs. dynamic, but 9 times out of 10 static is the only thing you can go on because few manufacturers actually measure dynamic (at least from what I have seen, but I could be wrong).

For the guys that are lost, I'll do my best to help explain what we are talking about:

If you're not getting this whole compression, valve, ignition, piston, etc don't worry about it, it sounds more complicated than it really is. I'm going to assume everyone understands the cycles of a 4-stroke motor for this (if you don't know those just google it, the 4 cycles are pretty easy to understand). In order to maximize the amount of fuel that combusts at the top of the compression stroke, obviously by the name the fuel is being compressed. This ratio of 12:1 or whatever is measured by dividing the volume of the cylinder when the piston is at the bottom of the stroke by the volume of the cylinder when the piston is at the top of its stroke. It is actually a fraction, we are saying that the volume of the cylinder when the piston is at the top of the stroke is 1/12th of when it is at the bottom. This is called static compression, it is basically the nominal compression the engine will be able to achieve (kind of like input would always be equal output force if there were no friction, but since there is friction the number is never 1:1). The same kind of concept applies to the 4-stroke internal combustion engine, where the intake valve may not close completely at the top of the compression stroke and thus some of the force of the piston compressing the fuel is lost. Now, in a perfect world valves would open and close at the exact time needed and the spark will go off at the exact top of the compression stroke to create the nominal amount of energy from the burning of the fuel. Manufacturers have been trying to gain more efficiency out of this design since before the first car ever rolled off of an assembly line. Things such as dual overhead camshafts and electronic ignitions are improving the timing of the combustion event, these systems can be more precise than their mechanical brethren. This, couple with other advances in efficiency such as head and piston design, allow modern cars to run static compression ratios that will make those of us who hump V8s for a living go running in fear of detonation.

Before the '70s detonation was actually less of a problem, believe it or not. At this point our more life-experienced members will know what I'm talking about and the younger guys are looking at their screens asking WTF. In the '70s a bunch of people smoked a bunch of weed and then decided to go run for public office (hahahahahaha! I'm kidding). What happened was the EPA put a ban on lead in gasoline, it had to be refined out now before it could be burned in a car. Well, some cars from the '60s were running static ratios of 12.5:1 on lead gas (you say you can run a 426 Hemi with a 12.5:1 on today's pump gas and guys will want some of what you're smoking). The lead was actually an impurity of the gasoline, but it also acted as a deterrent of detonation so until the EPA decided they had eaten too many lead paint chips as kids and wanted their own children to not have to breathe it coming from exhaust pipes, the American automotive manufacturers were caught with their thumbs up their asses when it came to performance without high compression, then came emissions regulations, then came a couple periods of gas crisis, and so double digit static compression ratios were pretty much eradicated in the '70s and '80s. Take the 1978 Pontiac L78 400, it was reduced to a 7.8:1 static CR (down from the 10.75:1 the RAIV 400 ran in '69, making an advertised 345hp but in reality was over 400hp), which with the technology was barely enough to even get the gasoline to combust. However, out of this lead gas ban and total performance deficit came such things as multiple camshafts, improved combustion chamber and piston design, improved ignition systems, and the birth of the showroom-available turbocharger. Speaking of Pontiac and turbochargers together, quick fact is that Pontiac was actually the major American manufacturing force behind turbocharging their cars in order to meet emissions and gain performance. But that went downhill really quickly when the Pontiac-specific engine got killed off then Ford came out with the 2.3L turbo SVO Mustang (which was the first reliable American turbocharging system).

If you would like more information on early turbocharged American cars or just how American manufacturers rigged performance tests in the '60s to make their cars look much slower than they actually were, please fell free to PM me. Many of the guys at car shows today will actually joke about the performance "numbers" that their cars ran back in the day. GM was probably the best at BSing the public, much of what they did was both ingenious and very entertaining once we know the truth.

If you are still interested in the theory of efficiency of internal combustion engines here is a link as it pertains to old Pontiac motors:
Engine Theory by Wallace Racing-Home of Pontiac Powered Firebirds,Trans Ams,and Dragsters

[Electrical_Tech]

I run 92/93 in both my bikes.

[Anthonyd5189]

87 for me...no need to run anything higher.

[PAFizzer]

87 or bike runs like poo. sunoco only

[Tripped1]

I run 89 in both of mine.....guess what the they ask for.

[HKSpowered]

depends on the time of year, in the summer i use a min of 89 with octane boost or 93, but in the summer i tend to ride up to US FUEL in new jersey off 22 by easton for some CAM 2 110 LEADED race gas and ill either run it straight or just add like 2 gallons a tank, the lead really helps.... people always say its stupid, but in a carbed bike, it really helps smooth out all the response imperfections and really helps overall to make my motor run "happy".... it doesnt make it fast........ in the winter and fall i will usually just run 89

[Enzo_Guy]

Originally Posted by HKSpowered

depends on the time of year, in the summer i use a min of 89 with octane boost or 93, but in the summer i tend to ride up to US FUEL in new jersey off 22 by easton for some CAM 2 110 LEADED race gas and ill either run it straight or just add like 2 gallons a tank, the lead really helps.... people always say its stupid, but in a carbed bike, it really helps smooth out all the response imperfections and really helps overall to make my motor run "happy".... it doesnt make it fast........ in the winter and fall i will usually just run 89

WHAT?!!!!!!!!!!!!! Lead race gas!!!!!!!!!

Normally to even get my old Pontiac to start it needs 93 and then I have to buy lead additive at the store. She just barely runs on the 93 with additive in it.

Well, then again for all of the power that car makes (which is somewhere between "no sane person would ever own this" and "I can't even drive this thing") I guess something has to be a trade-off. 1968 Pontiac 400, some work done to it, but for the most part this was actually the best Pontiac motor money could have bought in '68 short of a Ram Air. True figures are unknown, but I would guess around 400-430hp and 450-480ft-lbs and those are pretty conservative numbers. The car is REALLY stripped and weighs right around 3000 pounds. Now, put 450ft-lbs of torque and a 3000 pound car on a 215 rear tire, you have what it is like to try and drive this car. The tires are so thin that I only have to give it 1/2 throttle in top gear going 40mph for the tires to spin, and I don't mean chirp, I'm talking white smoking and the rear kicking sideways.

So can you send me some of this lead race gas? No particular purpose, it's not like I have an absurdly powerful car that is already painted brown and with wide tires would be the best sleeper on the planet. It's not like lead race gas would help it or anything!

[HKSpowered]

its made by sunoco race fuels, the product is called CAM 2 , its 110 leaded raceing gasoline. although finding actuall leaded race gas shoudnt be too hard, VP sells 5 gal blue drums of C16 (117 octane leaded), usualy anything 110 and higher is almost always leaded. whats cool with US FUELS in new jersey is that they have it at the pump, and they will allow you to pump it directly into a vehicle lol... my suggestion would be to call a bike dealer and ask, or find a local drag strip and bring a gas can (drag strips almost always have 106 unleaded, 112 leaded, and 117 leaded....... at least up here they do!

PS, if you try to pump it into anything newer (POST CAT CONVERTER ERA) the gas pump nozzle wont fit inside the tank (leaded gas pumps have an oversized nozzle).... with my 94 sportbike, its no problem, but for anything newer with a standard size gas tank port, grab a funnel!

[HiSpeed48]

i used to put cam 2 in my integra, but are u sure its made by sunoco? i used to buy it from the pump at exxon.

and i put 87 in the bike

[Enzo_Guy]

Originally Posted by HKSpowered

its made by sunoco race fuels, the product is called CAM 2 , its 110 leaded raceing gasoline. although finding actuall leaded race gas shoudnt be too hard, VP sells 5 gal blue drums of C16 (117 octane leaded), usualy anything 110 and higher is almost always leaded. whats cool with US FUELS in new jersey is that they have it at the pump, and they will allow you to pump it directly into a vehicle lol... my suggestion would be to call a bike dealer and ask, or find a local drag strip and bring a gas can (drag strips almost always have 106 unleaded, 112 leaded, and 117 leaded....... at least up here they do!

PS, if you try to pump it into anything newer (POST CAT CONVERTER ERA) the gas pump nozzle wont fit inside the tank (leaded gas pumps have an oversized nozzle).... with my 94 sportbike, its no problem, but for anything newer with a standard size gas tank port, grab a funnel!

Oh, I thought you meant something other than CAM2 (read: cheaper). God, I can't afford to put that amazing stuff in my car!

Yeah, the local strip has CAM2, and they let you know it with their price. Last I heard they are over $8 a gallon now. Car can sit for all I care!

[DaleCaliente]

Shell 93. why cheap out. I would never ever use less than 91 on a Supersport

If i was a really smart mechanic, and had proof/reasons to go lower, I would, but I am not.

85 octane. good luck with that...minimums are on bikes for a reason.

[HKSpowered]

i know master technician / wrecking crew leader (one of many lol) uses 87 half the time in his zx-10, and throttles 120mph wheelies with it lol

[HKSpowered]

Originally Posted by HiSpeed48

i used to put cam 2 in my integra, but are u sure its made by sunoco? i used to buy it from the pump at exxon.

and i put 87 in the bike

cam 2 is a racing fuel produced by Sunoco Racing Fuels, a division of sunoco im pretty sure, its not sold at sunoco though, i find it at a US FUEL, the racing fuel market is a whole new ballpark, which my best guess is seeing how expensive it is to make and use, sunoco racing fuels are just sold at other fuel stations and racetracks so they dont have to employ more costs to get their product out, and their is almost no demand for it in comparision to reg. fuel

just my .02 cents

[yjsjin]

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