octane

[dzalj1]

what octane requirements do i use on my strangler v4? the engine is fully rebuilt but not yet started? would 98% octane fuel be ok to use? just for the holidays? i'm gonna have my timing set to around 24-26 degrees, my commpression per each cylinder's are around 140-150pds and i mwill be running jets inbetween 66c to 76c

[Prof. O/B]

dzalj1, I don't know a thing about a Strangler V-4, but what I do know about is octane requirements for an engine. What was the original CC's of the head, what was the original timing of the engine, and what were the original jets?

I normally predict octane requirements based on compression ratio. Generally on a 4-stroke motor, using the standard 4-stroke method of determining compression ratio. A increase of two (2) octane numbers (not points!) will allow the increase of one (1) compression ratio. The 4-stroke method of determining compression ratio is to determine the swept volume of the cylinder. Sweep volume is the stroke in inches X area of the cylinder bore. An example in determining area of the bore could be a 3-1/2" bore motor with a 2.650" stroke.

Area = radius squared x PI

Radius of 3.5" bore is 1.75", so 1.75" x 1.75" = 3.062"

3.062" x PI (3.1416") = 9.621 sq. in. (area of bore)

For Sweep Volume, we must multiply Area of the bore X the Stroke, e.g.,

9.621 sq." x 2.650 in. Stroke = 25.496 Cu. "

The conversion of Cubic In. to CC'S is to multiply the cubic inches x 16.39, or
417.88 CC's

If you had a 26 CC head (417.88 sweep volume/26 head volume) the compression ratio would be = 16:1, however we know this is not true for a 2-stroke. We then must use the "Japanese" method for calculating the compression ratio. Sweep Volume can not be used in the same manner as was done for the 4-stroke as the cylinder is not "sealed" up like a 4-stroke. That is, the exhaust port is open. If for instance, the exhaust is set at 1.500" from the top of the deck, then we must calculate the volume of the cylinder from this point:

again, bore area = 9.621 sq.in. X 1.500" = 14.431 cu. in. or (multiplied by 16.39 as was earlier done = 236.53 CC's

236.53 CC's / 26 CC's = 9.09:1 compression ratio, however this is not true either. The reason being, you are not calculating for "Dynamic Compression". When the RPM increase in an engine the charge is being "pressured" up into the cylinder head. The charge is more than the simple Japanese Method calculation would account far. If we were to "blend" the two methods (4-stroke method and the Japanese method) which would be 9.09:1 + 16:1 you would be closer, 9.09 + 16 = 25.09/2 = 12.545:1. This is a really probably a bit to much, more like 11:1 which would require approximately 100 Octane. We know this to be true, because what I described is basically a 26CC head 2.5 LTR Merc motor which would run quite nicely when you blend 108 octane with 93 octane pump premium. 108 + 93 = 201 /2 = 100.5 octane (it's really a little higher). So, figure what your stock heads were, re-calculate your compression ratio for the change you made in cylinder head CC's, and allow two (2) more octane numbers for the increase of each compression ratio .................Prof. O/B

P.S. Forget about using octane boosters, you can use Toluene for the boost, which with a natural octane of around 119 will work wonders

[Jay Smith]

Welcome back..........And Merry Christmas.

[Prof. O/B]

Welcome back..........And Merry Christmas.

Same to you and the Miss's, just write a little when time is available. You have a Merry Christmas, Hannaka and Kwanza. Note!! If there's anyone reading this post I left please email as I'm trying to workout my unresolved "Culturial Sensitivity" issues........... Prof O/B

[Prof. O/B]

Dgalz1, in the discussion of the 2.5 LTR I outlined above, it has a cranking compression of 180 PSI. So the 150 or so PSI should be no issue on 98 Octane......Prof. O/B

[GTO GEORGE]

Where can you (the public) buy toluene; it's a known carcinogen.

[Mark75H]

You can buy it at any hardware store ... don't freak out, many components of dirt, paint, burnt toast and black residue around the top of your ketchup bottle also contain "known carcinogens"

[staylor]

...it's in many paint thinners and has been commonly used to "hop up" gasoline for the last half century or so. It became popular as a solvent when they outlawed benzene- which was known to cause cancer, especially when buried underground with other chemicals where benzene combines to form dioxin- which is extremely toxic. My business has used toluene for cleaning aircraft parts for more than 50 years with no issues at all. OSHA has been in from time to time with sniffers to check our in-plant levels. Even if you spill a quart on the floor in a small room it's hard to exceed the allowable limits while cleaning it up- although it will dissolve many types of floor tiles....

As an aside, the old Merc manuals, circa 1950, for the old Hurricane & Lightning engines used to tell you to use benzene or benzol to clean carb parts and spark plugs. I used to buy it in the late 1950s at a drugstore, but eventually even the druggist wouldn't sell it to the public anymore.
Doug

[MattGreen]

The official designation for toluene, by (arguably) the most respected authority on the subject is "toluene is not classifyable as to carcinogenicity in humans".
It does however cause central nervous system (yer noggin') damage in high doses, amongst other things. Benzene on the other hand, is a confirmed human carcinogen, leukemia specifically. There are low levels of benzene in road gas, lots in race gas (one of the things that makes it smell great), and LOTs of TOLUENE in high-test pump gas. That's why people who actually know what they are talking about when it comes to fuels often suggest toluene as an "octane booster" - aromatic rich blending stocks (like toluene) are used to make premium gas - it's already there, feel free to add more ! You can buy it at any paint store.

By the way, neither of these compounds "forms dioxin in the soil". Dioxins are formed in high-temperature reactions involving chlorinated organic compounds, which are essentially absent from gasoline. The best known source of dioxins was the poor quality 2,4,5,-T herbicide sprayed to kill trees over Vietnam - Agent Orange. Many high-temperatiure industrial processes, such as incineration, generate low but measurable concentrations of dioxins.

What a nerd, is anybody still reading this ?

ha, ha,
Matt

[Prof. O/B]

Fellows, I wasn't trying to kill Dzalj1, and all known animal and plant life, just trying to help him up his octane a little, honest..........Prof. O/B

[staylor]

You're one of the good guys, Professor. I was going to suggest a mix of nitro, alky, and hydrazine- a mix that some of the kneel down racers played with back in the 1960s up here in Buffalo. We got the hydrazine out the back door of a local plant that built rocket engines. I was trying to remember the exact mix proportions but I think that sniffing the exhausts from motors running that mix eliminated that portion of my brain. Now if these headaches would just go away.....Doug

[Forkin' Crazy]

Fellows, I wasn't trying to kill Dzalj1, and all known animal and plant life, just trying to help him up his octane a little, honest..........Prof. O/B

Hi Prof O/B. Ya left my head swimin' abit with that first post... I had to read that a couple times. ;)

How much difference would that make in a crossflow? Would the deflector heating up be an issue?

[YELLOWSS]

ok you have my attenton!!! if you use toluene what ratio for octane boost.
exp: 10 gal of 93 oct, and 1 gal of toluene so added 10% what oct would be created??????

Does toluene come in different % in thinners or is it 100% toluene.

Also does it change the rate of burn like airplane fuel??? in other words is rejetting or changing your ecu/pcu an issue?

Roy

[Juggernaut]

...it's in many paint thinners and has been commonly used to "hop up" gasoline for the last half century or so. It became popular as a solvent when they outlawed benzene- which was known to cause cancer, especially when buried underground with other chemicals where benzene combines to form dioxin- which is extremely toxic.benzene is in gasoline. i dont believe they ever outlawed gas.. and who's burying gasoline? they should be burning it in a outboard or a big block!

[Mark75H]

Benzene used to be in gasoline, the present allowable percentage of benzene is microscopic. If you read about gasoline you will find words something like "mixture blah, blah, blah containing aromatics .... blah blah" and then an example of what chemicals are aromatics usually follows mentioning benzene, but that does not mean benzene is a current gasoline ingredient. Other aromatics such as toluene and xylene are current ingredients of gasoline.

I have used high toluene ratio gasoline and DID NOT FIND any need to make a jetting change, my plugs still look like light chocolate regardless of the toluene content. My guess is that the talk of needing to make a jetting change comes from some theoretical GUESSWORK that is for the most part, or perhaps completely, wrong.

[Dave S]

results use lead. Darn EPA.:(

[raymar]

Find a friendly airport and buy yourself some 100LL aviation gas. It is good for about 115 octane when running rich in an engine running as cool as an outboard. Aircraft engines run much hotter than outboards, as much as 450 degrees or more cylinder head temps. Some aviation fuel also contains toluene
too. I have had no piston failures when running avgas, even when racing.:rolleyes:

[MattGreen]

Sam,

I don't know about the US, but in Canada it's limited to 1% in road gasoline. From a "toxics" perspective this is still significant, which is why it was brought down from previously higher limits. I would imagine the US laws are similar.

It would be difficult to entirely remove in a cost-effective manner.

Matt

[Prof. O/B]

ok you have my attenton!!! if you use toluene what ratio for octane boost.
exp: 10 gal of 93 oct, and 1 gal of toluene so added 10% what oct would be created??????

Does toluene come in different % in thinners or is it 100% toluene.

Also does it change the rate of burn like airplane fuel??? in other words is rejetting or changing your ecu/pcu an issue?

Roy


Roy, our friend Mark75H is right no "up jetting will be required". Actually jetting of non-oxygenated distillates all things the equal, are determined by specific Gravity (weight). Obviously, if something of a greater weight passes through an orifice than something of a lighter weight you are going to get more of it. Pump gas is say .750 Sp. Gravity (relative to water at 1.00), Toluene is .866 Sp. Gravity. Pretty heavy, of course all Sp. Readings are taken at 68 DEG. F. in accordance to API (American Petroleum Institute) Specs. Now when I told ya that toluene was 119 octane, that's true, but that's RON (research octance number), it's about 113 on the MON (Motor Octane Number) scale, and you have to add the two together: 119 +113/ 2 = 116 octane as would be read at the pump. Toluene, is 100% Toluene.

If ya had 93 Octane and we were going to be mixing-up Toluene with it, as you said at a 10% level, let's make a 10 Gal. mix

9 Gals. (pump) x 93 = 837
1 Gal. (toluene @116 = 116
----
953

953/10 (Gals) = 95.3 octane

That will support one (1) compression ratio, greater compression

.....................Prof. O/B

[Prof. O/B]

P.S. It burns slower because it is more dense

[Mark75H]

P.S. It burns slower because it is more denseWould it then follow that propane would burn faster than almost any other hydrocarbon?

[YELLOWSS]

thanks prof. o/b that is exactly what i needed to know. my heads are a little tight for 93 oct. i use to be able to buy 94 at the pump. i have a 2.5 260 with about 160 lbs of comp. so i need to change heads or run higher oct. i think 95.3 should be close to what i'm looking for.

roy

[Techno]

I'm not sure what the answer to dzalj1 was:confused:
But If you need high octane then you must run it on the weak days also.
If you don't need it then your only throwing your money away and any increase is mostly from the fact you spent so much money that you can "feel" the improvement, but there ain't any. In fact you could lose a bit of power.
High octane fuel is for engines that are built to use it, must have it. You lose far more power by detuning the engine to run low octane than if it was built to use low octane to begin with.
Low octane engines cost less to run.

[Prof. O/B]

I'm not sure what the answer to dzalj1 was:confused:
But If you need high octane then you must run it on the weak days also.
If you don't need it then your only throwing your money away and any increase is mostly from the fact you spent so much money that you can "feel" the improvement, but there ain't any. In fact you could lose a bit of power.
High octane fuel is for engines that are built to use it, must have it. You lose far more power by detuning the engine to run low octane than if it was built to use low octane to begin with.
Low octane engines cost less to run.

Techo, I think Dzalj1 was really hunting a "safe" fuel. I believe he said he was running @160 PSI cranking, I think we would both agree 93 octane would be pretty "iffy" at this cranking compression. You do however raise an valid issue in regards to lost of performance by over-octaning the fuel.

However, it is not the over-0ctaning of the fuel that really concerns me. My primary concern in regards to lost of power would the difference of "Heats of Combustion" between regular gasoline and the gasoline/toluene blend. Another concern could possibly be in the theoretical difference in "perfect" stoichs of one fuel relative to the other. For example, the "Perfect" stoich (complete combustion), of toluene is 13.5:1 fuel/air ratio Vs. Octane (yes, the distillate octane does exists, with a rating of 100) is 15.11:1. The distillate "Octane" is a convenient method for clculations and considerations of fuel/air ratios. Once again these are "Perfect Stoichs", not "realistic stoichc".

However, at the concentration of this blend level, and in consideration of the off-set afforded by an actual increase in fuel delivery due to the higher Sp. Gravity of gasoline/toluene blend, it should be a "wash". If less efficienct combustion occurs, it would be evidenced by a lower reading on the E.G.T.s. I do agree that he will probably be slightly over-octaned at 160 PSI cranking. Because his present increase in compression would not justify a 10% blend, i.e., he has not exceeded the maximum compression ratio of 93 octane fuel by yet another "full" compression ratio, that would be afforded by a 10% blend. If power does fall off a little I would counter with a slight increase in ignition lead in lieu of a decrease in fuel delivery...............Prof. O/B

[Prof. O/B]

Would it then follow that propane would burn faster than almost any other hydrocarbon?

Actually, the fastest one would be the one with the greatest amount of hydrogen. That would be methane (CH4), followed by ethane (C2H6), then Propane (C2H8) and finishing-up the natural paraffinic LPG series, Butane (C4H10). You will note that volatility is relaitive to the increase of hydrogen; as well as is the "heat of Combustion".

Heat of combustion for straight Hydrogen (H2) is 61,031 BTUs per Lb., for methane is 23,890 BTUs per Lb., ethane is 22,329 BTUs per Lb., Propane is 21,670 BTUs per Lb., Butane is 21,316 BTU's per Lb. Using a reference of gasoline, and for for convience I use "Octane" @20,529 BTUs per Lb. (a true Gasoline @ .739 Sp. Gravity @60 F. API will yield 20,750 BTUs per Lb.).

Practical Engine fuels would be of course, Propane, Butane and gasoline. Methane, with it's formidable BTUs and accelerated flame Speed would prove itself unmanageable as a fuel source for a conventional engine. In regards to Propane, I do not remember off-hand what the octane is, but Butane is approximately 100 octane if memory serves me correctly.

In regards to propane, yes, flame speed is faster due to greater hydrogen content, but is a viable fuel (as is butane), for a contempory internal combustion engine. A lot of this is do to a couple of factors, while both are carried as LPG (Liquified Petroleum Gas), they are in a liquid state stored somewhere around 180 PSI. They take a reduction in pressure a couple times, generally arriving at the butterfly at less than atmospheric pressure. This reduction in pressure (an accompanying expansion to vapor) has a very pronounced and positive effect in absorbing heat. This coupled with natural octane make it a viable fuel. If you would check the "perfect" stoichs of these fuels you would find them very favorable with gasoline. However, in the real world, the efficiency suffers because the injection of a vapor lacks the full cooling "punch" when compared to gasoline. Some claim more efficency in Gal. to Gal. comparision to gasoline, however in the latest tests of 50/50 mixes of Propane/Butane blends appear to be only about 80% efficient by volume as compared to gasoline. However, with their low carbon content they are an extremely clean burning fuel. It may be of note, that for years natural Butane (n-butane, a single chained hydrocarbon) has been injected in gasoline to increase Volality. This is part of the "Climatizing" of gasoline, in this case for "winter-starting". It maybe also of note, that n-butane can be isomerized by a catalysis into "iso-butane" (a branched-chained hydrocarbon), which has long been used to increase the octane of existing gasoline fuel stocks
................Prof. O/B

[dzalj1]

hey guys thanks for all your octane help, i went for a run this
weekend and i was haing problems, but i will put a new thread about the issue, fut for the fuel, i used 93% octane, just for my first run, it seemed to like it very much lol but yeah its ok for now until i buy a better faster type boat.

[Juggernaut]

Benzene used to be in gasoline, the present allowable percentage of benzene is microscopic. If you read about gasoline you will find words something like "mixture blah, blah, blah containing aromatics .... blah blah" and then an example of what chemicals are aromatics usually follows mentioning benzene, but that does not mean benzene is a current gasoline ingredient. Other aromatics such as toluene and xylene are current ingredients of gasoline.

I have used high toluene ratio gasoline and DID NOT FIND any need to make a jetting change, my plugs still look like light chocolate regardless of the toluene content. My guess is that the talk of needing to make a jetting change comes from some theoretical GUESSWORK that is for the most part, or perhaps completely, wrong.i assume that boosting octane with toulene does not require upping the jets.. i wasnt aware that benzene in gasoline was reduced.. well, thanx 4 the update.
anyways, with all this talk about propane, its got me thinkin.. nowadays, many performance diesels are running propane injection. normal diesel fuel is about 45 cetane, i think.. how do they inject something soo volatile into the intake? couldnt it be possible for it to self-ignite in the intake?

[Mark75H]

The injected propane is too lean to ignite, it depends on the regular Diesel injection flame to ignite it.

I did this many years ago on a Mitsubishi turbodiesel. I had gone beyond the point of practical injection enrichment (there was a intake pressure sensed enrichening circuit on the regular injector pump) and decided to to try dumping a lean mixture of propane in with the incoming air. My first runs were with the propane tank on the passenger's seat and a hose going up to a fitting on the intake manifold ... after deciding the results were impressive I rigged up an automatic system that opened a regulator type propane valve only when the boost pressure was up above 4 or 5 psi. The automatic valve was pretty simple ... just a regulator I took apart and put a spring on the gas side of the diaphragm and closed the vent and connected a line from the vent side to the intake manifold. When the normal spring pressure plus the manifold pressure were greater than the new internal spring pressure, propane was fed into the intake manifold.

[capnzee]

I ran toluene in my 6 liter hydroplane for many years. I mixed it at a ratio of 1 qt to 5 gallons of 100 octane aviation fuel. An engineer for Chevron advised me that this mixture would give me 110 octane. I ran a 350 cu. in. chevy at 10 plus to 1 compression ratio with absolutely no ill effects. In the old days (WWII) military aircraft would carry toluene over Europe in case they had to land at a foreign field and needed to pump the 100/130(green) up to 115/145 octane(purple)(required for maximum take-off power. if my memory serves me right. red blue green purple--Rich Boys Get Pussy. Some things never change! Red=80 octane Blue=100 octane Green=100/130 Purple=115/145! Now hows that for a memory? Capnzee

[CALVIN]

What technology do the european offshore diesel boats use to get the crazy speeds...propane?