AZZ28

I found a station with VP 101 octane on pump. I am tempeted to run through a quarter tank during my next trip to the track, but I have a few concerns. This is only going to be a one time thing, but will it damage my 3" Magnaflow cat. 2. Will the stock ignition system (Accel wires, bosch plugs) handle it well.

flaming-ford

iTrader: (7)

all a higher octane fuel is, is slower burning....

That's why super high compression motors have to use race fuel only or else it will pre ignite *ping*.

Only thing octane boosters or higher octanes do to a street car in generalities, is reduce your ammount of spending money in hipo parts!

I suppose by running a higher octane fuel you can get by with running a decent bit more timing but, if it's a 1 time thing that'd be kinda annoying setting it up just right and all. Then again guys with serious nos do that all the time when racing without the nos.

F-BIRD'88

Hi octane gas is not "slow burning"
Hi octane gas resists detonation ( pinging) therefore can tolerate higher compression ratio an combustion heat.
Fuel burns in an engine. if the fuel getts too hot too fast it explodes and hammers the piston instead of burning and pushing on the piston.

Modern *unleaded* high octane gas will not mess up your cat converter. Gas that contains lead will mess up your cat converter. Some hi octane gas is leaded type.
VP actually sells both types leaded and unleaded.
As long as it is unleaded you'll be fine.

If your compression ratio is less than 10:1 and/or you don;t have a high boost supercharger, then high octane gas will not make you go faster. It only resists detonation better than low(er) octane gas in engines that require it. You only need enough octane performance to avoid detonation. More than that amount is just wasted money.

But trying to operate a hi compression motor at WOT with less octane than is indicated by its design, will cost you big. (rebuild)

coolram62

iTrader: (2)

Only way on a stock motor you could begin to take advantage is you could dial in more static timing.But how much the ECM will accept i have no idea.F'Bird'88 said it best and please listen when he says make sure you use the unleaded hi-test if you give it a try or you'll melt your cats - literally.

Vader

Not to throw any hand tools into the works, but I'm running 106 octane in my half-truck, and at $1.72/gallon, it doesn't seem like a waste of money compared to $2.23/gallon for regular. Unfortunately, I can't take full advantage of the fuel since the PCM is not flashed for higher timing advance, and there is no practical means to move the crank trigger to gain advance.

firebirdjosh

iTrader: (1)

Can I have some?

AZZ28

Thank you for the detailed responses.

flaming-ford

iTrader: (7)

[QUOTE]Originally posted by F-BIRD'88
[B]Hi octane gas is not "slow burning"
Hi octane gas resists detonation ( pinging) therefore can tolerate higher compression ratio an combustion heat.
Fuel burns in an engine. if the fuel getts too hot too fast it explodes and hammers the piston instead of burning and pushing on the piston.

Not trying to contradict or say your wrong, i'm just kinda looking for an explanation, basically i'm thinking that if it's detination resistant then it's a slower burn, am i wrong in thinking that?

If so just wondering how is it detination resistant t/y!

F-BIRD'88

Get the slow burn concept out of your head. A fuel's octane or resistance to detonation is not tied to or related to the "burn rate"

Gasoline in its pure raw form is relitively low octane.

Hi octane gas is blended with special chemicals like MTBE, ethanol, tolene, xelene and others that have a high tolerance to hi compression,heat, preesure without exploding. Other additives (solvents) are used to adjust the burn rate, reed vapour pressure and lubricity. other chemical additives like acetone help keep the mix/blend homogenized.

Hi octane gas is more resistant to unstable combustion (detonation) and priignition (autoignition before the spark occurs) caused by more heat and more pressure, than lower) octane fuel. thats all. Usually the motor will not want or need any more ignition timing at all. the fuel burn rate is the same or very close.

A hi performance hi compression motor need a fast burning, hi heat content ( BTU) and be resistant auto ignition ( detonation).
Think about it: a hi rpm motor, as it revs higher and higher has less time to burn the fuel on each power stroke as the piston goes down before the exhaust valve opens. if the fuel burned "slower" there would ne be enough time to burn it all at high rpm.
Jacking the timing up to try anc compenaste creates "negative torque" as the slow fuel burn resists the raising piston before TDC.

Some people get the idea that if they run hi octane gas in their street motor that they can and should jack the timing up. Not true. The motor will still want the same 32-36 deg total timing to make best power. Get much beyond this and power decreases. May not hear pinging for the overadvanced timing and the low end throttle responce may feel better but top end will be less ( too much total timing) . What you really need to do is recurve the distributor timing to allow more initial with the same total, for better acceleration and throttle responce.
A factory distributor is set up pretty tame.

A engine that wants much more than about 32-36deg timing indicates improper tune (over rich or over lean AFR or poor ring seal (ring flutter) or exessive valve overlap creating over scavegeing and/or exhaust dilution at speed) the motor really want different cam timing and or a different exhaust header configuration. the seeming need for more timing is just a crutch. When the valve timing, AFR and or exhaust system design is corrected the motor will want normal ignition timing. Often less timing. (more efficient combustion)

Some hi performance fuels can make (a little) more horsepower than pump gas because of a higher heat content (BTU)
than pump gas. This characteristic is independent to octane rating or burn rate.

Lots of disinformation and folklore about race gas and aviation fuel floating around.

vortech35091RS

What do you mean by More Static Timing? And what you said on How much the ECM will accept.

P.S: There's a lot of good information on this post

flaming-ford

iTrader: (7)

t/y good explanation like i said i was just thinking it was *slower burning because, that's what i've been told but, obviously i had been misled*. T/y for clearing that up and good explanation.

Vader

Any E-85 pump should take care of your needs.

88_Import_Slaye

305sbc

iTrader: (3)

Did you get this from Joe Pettitt's book or the Hartman book on hi-po fuels?

I've seen this information before as well, and I wonder if you've tested these ideas out in person? or perhaps things are different in Canada.

I have tested numerous times and though it may not technically be related to the octane content, I can tell you without a doubt that every race gas I've tested burned significantly slower than pump gas. It may be due to different specific gravity... I don't know, but the practical fact is that it does burn much slower in use.

Every car I've seen run race gas that didn't really need it has run slower times. Some of them have also run hotter and/or thoroughly confused the computers closed loop control.

edit: not trying to start an argument, just asking questions and reporting from my experience.

The E-85 if I'm not mistaken is a high percentage of ethanol (alcohol) which is resistant to detonation, but also makes less power in the process given equal amounts compared to gasoline. For everyday driving this isn't a problem as you use very little of the engine's potential power output.

Mkos1980

iTrader: (8)

I've run sunoco blue 100 through my system with cats and all with no problem. It did take care of the 2 degrees retard I had at the track that day. My compression is about 10:5:1

rx7speed

[QUOTE]Originally posted by flaming-ford
[B]here is something for you to think about.
head designs that are the least prone to causing detonation have much faster flame front speeds.
so basicly the fuel that is burning is burning a lot quicker.

contact

the fundamental property of hi-octane
is 'explosion resistance'.

I think it is possible that certain hi-octane
gasolines have slower flame speed.

IF SO...

there are now two timing issues,

Taking advantage of the high octane, which
lets you choose timing where you want, instead
of being timing-knock-limited at WOT.

and,
correcting for the supposed slower flame speed.

rx7speed

another thing to think of as far as flame speeds
nitromethane
it has less energy per pound of fuel compared to gasoline
it has a lower octane rating then gasoline
but here is the kicker it burns slower then gasoline


octane rating doesn't deal with fuel burn speeds sure some fuels might burn slower and have a higher octane rating but that doesn't mean that higher octane means slower burn rates.


if that was the case diesel should have a fairly high octane number also. it burns really slow if I remember right but isn't diesel very prone to detonation compared to gasoline?

flaming-ford

iTrader: (7)

i dunno about diesel being more prone to explosion you have to think diesels run around 20 to 1 compression.... They fire off of compression not spark plugs.

Then again maybe it is since they do fire off of compression.........

i dunno above my head. I just found out your suppose to add diesel additives to diesel tractors and such over the winter or else the diesel gels up (supposably i ran mine for a year and a half without it, with no problems).

Any1 feel like explaining diesel propertys by any chance hehe.

F-BIRD'88

Well in the early 70's when leaded gas was outlawed at the gas pump, a Canadian company was one fo the first to step up to the plate with a modern Unleaded high octane racing fuel.

It is called Pro Racing Fuel out of Mississauga, Ontario.

Distributed in Northern US also.

Norrmally does not need any more ignition advance than pump gas. Typically makes a little more power than pump gas. Documented in both dyno and track testing.
Some heavily oxegenated fuels with different specific gavities can confused a computer EFI and are not compatable with NOS. Not this one. Usually little or no re- jetting is required as the specific gravity is near pump gas. It is not oxyenated.
Often make a little more power than other racing fuels as well.
And does not burn any slower. Remember what I said about a high rpm engine having less time to burn the fuel during each power stroke as the rpm increases. A slow burning fuel just doesn't make sense.
If the race gas you're using "burns slow" maybe you should look into a fuel like this one.
A abnormally slow burn rate is just going to slow down a hi- perf or race motor.
if your motor suddenly wants more advacne with a certain fuel i'd suspect the AFR is off. If the specific gravity is much different and or it is heavily oxegenated then it will be lean(er) lean mixtures want more timing. Really it needs rejetting. May need a air bleed change as well. Then the motor should want more normal timing.

I'm not a real expert in race gas, but this guy is.
The stuff works and doesn't burn a hole in your gas tank.
.



Pro Fuels

If the engine runs hotter and looses noticable power when trying a race fuel, I'd suspect it is leaner. Lean mixtures burn slower and heat the cylinder walls instead of pushing on the piston. A slow burn rate is not what you want.
If you have to add stuff to a fuel that slows the burn rate in order to gain octane, You're not going to make power and win races.

My motor doesn't require it. The cr is only 9.8:1. but have used to in the past and use the "MARK II" when I want to get serious with the Nitrous.

If you're runing something like a Pro MOD then the "MARK V" is the way to go. This is some serious racing fuel yet 100% unleaded.

305sbc

iTrader: (3)

Thanks for clearing that up. I have actually never ran the high octane unleaded that is available here, so can't say the same about the burn rate.

IRT the above quote, that's not exactly what happened with the race gas. Leaning the mixture down further actually cleared up some of the problem by adding some power and lowering the coolant temp, though still not as good as lower octane pump gas.

The slower burn of race gas is to allow the use of higher compression ratios which speeds the burn up in the right place. As the piston approaches TDC the mix is compressed which increases the temperature. Adding heat speeds the burn rate. High RPM adds turbulence to the mix which also speeds the burn to an extent as well.

The idea is to time the pressure peak of burning mix to around the 14* ATDC mark for best power in most cases.

IMO the best way to do this is by using the correct compression (dynamic and static) for the fuel, vice starting the spark a significant amount earlier. This is not to say spark advance isn't important, but you reach a point when more advance becomes counter-productive IMO. Even if you're not getting knock, you are still losing power with more advance.

With the fuels I've used, this is what I've seen.

kind of off topic I know, sorry.

F-BIRD'88

Except that a hi performance motor revs higher with an decreasing burn time on each power stroke as rpm raises.
Yes high compression ratio and high chamber swirl increases burn rate but it is more than offset by less available burn time. (RPM)
The net result is about the same burn time (ignition timing requirement) as a low compression , low rpm motor.
So you really want a fuel that burns just as fast or faster using less timing to make max power.

When you re-think the concept that you need to slow the burn rate, you'll go faster, with less timing and negative torque.
This is why Pro Fuels and others like it typically make more power with increased reliability and less tuning issues the the "other guys". This is one reason (among others) that aviation fuel is not optimum or recomended for a automotive hi perf engine.
Airplane motors are relitively low rpm engines as a rule.

84z28350

Or you could just throw on a cheap cat or eliminate the cat for the run if possible. Being a one time thing i would eliminate the cat so long as the smog ***** dont get you

Problem solved

contact

305sbc, and others,

when you say 'i KNOW that race gas burns slower',

how do you know that?

rx7speed

some more fuel for thought for those saying that lower fuel burn rates means less of a chance of detonation

heads way back in the day used the huge open combustion chambers vs the newer heads with a much more closed in chamber that has a healthy squish pad.
both have the same combustion chamber yet the older design will have am uch slower burn rate and yet be more prone to detonation.

there was a motor built using a 502. it arn I think over 12:1 compression if I remmeber right on 87 octane. part of the reason it worked was the fueling heads. with the head design it promoted very fast burn.
there is a difference between a fast burn and an uncontrolled explosion arising from two flame fronts.


when the fuel is slow to burn it gives more time and chance for detonation to happen. typicly you want to speed the rate of fuel burn up to reduce detonation. when the burn speed of the fuel is slow it gives more time for the existing unburnt fuel to autoignite because of the pressure or heat. that is BAD JUJU.

again something to think about diesel fuel has an octane generally around the 30's
they instead use a cetane rating. the higher the cetane rating the lower the octane number generally. but think about it with diesel it burns slow as a *****.
doesn't that also counteract the higher the octane the slower the fuel burns?

so again octane rating doesn't have to deal with what speed the fuel burns. all the octane really is for is how easily the fuel will autoignite. how easily the fuel autoignites has nothing to do with burn speed, power output or anything like that all by itself.
just how easily the fuel will ignite under heat and pressuere.