| From | Message |
Teamfast
Dodge Dakota
10/08/2001
18:09:51
|
 Subject: Octane
IP: Logged
Message:
I've heard a few posts claiming better
performance with more expensive gas so I
pulled this from Popularmechanics.
Octane rating in gasoline is a measure of its
resistance to preignition or detonation.
Specifically, when the piston is coming up to
the top of the cylinder, it compresses the
gasoline/air mixture to around 10 percent of
its original volume. As it's compressed, it gets
hotter. At the correct time, this hot, turbulent
mixture is supposed to be ignited by the spark
plug. A lower-octane fuel has a greater
potential for igniting prematurely, which
makes a distinctive pinging sound. This can
damage engines, and certainly has a poor
effect on economy. Higher-octane gas is more
likely to ignite only when it's supposed to. How
high an octane your engine requires depends
on many things, like compression ratio,
camshaft profiles, combustion-chamber
design, the state of your fuel injectors and
barometric pressure. Using a higher-octane
fuel than is necessary is expensive. And there
is actually more energy in lower-octane fuel,
meaning there is potentially more power and
economy available at the less expensive
pump.
Most modern cars can adjust themselves for
the amount of ping by using a mechanical
sensor bolted to the engine to listen for the
characteristic sounds of engine ping and to
change the ignition timing. This keeps the
engine from hammering holes in the tops of
the pistons–but it still means you're wasting
gas by running the engine at less than
optimum. Check your owner's manual for the
carmaker's recommendation and then use
the lowest octane fuel you can. If your car has
a knock sensor, use the fuel grade that gives
the best fuel efficiency.
|
CW
Dodge Dakota
10/08/2001
18:39:22
|  RE: Octane
IP: Logged
Message:
If you run octane that is more than required than it can hurt performance slightly, but if you need that octane then running too little will really hurt things. Dodge magnum engines don't use knock sensors, not sure about the 4.7 though. Recommended octane in my owners manual says 87.
|
bernd
*GenIII*
10/08/2001
20:45:22
| RE: Octane
IP: Logged
Message:
Uhhhh...I have to run 93 minimum. ;)
1997 Dodge Dakota SLT - V6
Supercharged @ 10# w/Nitrous
|
CW
Dodge Dakota
10/08/2001
21:05:56
| RE: Octane
IP: Logged
Message:
No kidding Bernd, I just wish I had the HP/CID in my V-8 that you have in your 6.
|
kota on 20s
Dodge Dakota
10/09/2001
01:53:58
| RE: Octane
IP: Logged
Message:
i run 87 regularly, and it seems to me that when i used 92 with 104 octain booster (black bottle) it ran better.
Eric
|
Matt Barret
Dodge Dakota
10/09/2001
08:07:57
| RE: Octane
IP: Logged
Message:
NOS octane boost, W/ Nitromethane, SILVER can !!
I think I should own stock in the company, or either start buying it by the 50 gallon drum!
Its good stuff, good for a quick tenth usually ;)
Matt Y2K-HEMI
'00 RC 4.7L 5spd 3.92
|
kota on 20s
Dodge Dakota
10/09/2001
09:27:57
| RE: Octane
IP: Logged
Message:
i have heard that the nos booster jacks up your cat.
Eric
|
CyberWolf
Dodge Dakota
10/09/2001
09:56:34
|  RE: Octane
IP: Logged
Message:
Teamfast, that is very true with most cars but I cant even get my Dak to quit pinging with 93 octane much less with something lower. The Steeda (mustang) catalog has a long article about how you should use the least amount of octane possible also.
|
G. Cowardin
Dodge Dakota
10/09/2001
11:19:36
| RE: Octane
IP: Logged
Message:
I would say for the average driver use 87 when the weather is nice, but if you drive it hard and its hot out, go for the 93 to be on the safe side and keep performance up. Does anyone know if the 4.7L has computer controlled timing? My car has it and you must run 93 or it will back the timing off to about -10 degrees, runs terrible. I doubt a truck engine would have this, but it would be good for the performance minded.
|
TallQuad
Dodge Dakota
10/09/2001
12:29:07
| RE: Octane
IP: Logged
Message:
CAR and DRIVER just did an article on different octanes, "Regular or Premium?". Its in the new November issue on pages 133-135. Just in case anyone is interested.
Long story short, if your car doesn't need 92 octane, it won't help the performance (in some cases hurt performance). However, there are other engines that it will, like older ones or high mileage engines. It was a good article! They also tested Ram 3500 5.9 and found little performance gain w/92.
|
Donald
Dodge Dakota
10/10/2001
22:03:05
|  RE: Octane
IP: Logged
Message:
I've seen differing opinions here based on different articles.. but here is my 2 cents worth:
The more octane a fuel has, the cooler it burns. The cooler the engine, the longer it lasts.. at least in theory. Any Air cooled engine should use at least 89 octane fuel as it runs cooler. most air cooled engines are used in the hot summer months like: lawnmowers, tractors. lawn trimmers, etc.
I've never ever heard of too much octane hurting an engine's performance although too much octane will cause excess pollution. My mechanic and I seem to agree that anything above 89 octane is overkill for 4 cycle non air cooled engines ie: any Car or Truck. I use 89 Oct in my 1987 Dak and it runs great!
BTW, i'm guessing since my dinosaur 1987 Dak automatically adjusts the timing virtually elimninating pinging, that the newer models should do the same. For a while my dak wouldn't stop pinging and it hesitated and died frequently, especially when cold. I tried new plugs, wires, etc. but it wouldn't stop. Guess what was wrong? the main system computer was dead. I had to buy a new one and now my dak rarely ever pings! woo hoo I was about to get rid of the thing had that new computer not fixed it. I got to keep my dak! woo hoo :)
Donald
|
TEAMFAST
Dodge Dakota
10/10/2001
23:05:51
| RE: Octane
IP: Logged
Message:
1. While some of the more expensive car
models require premium gasoline, for most
cars the right octane is regular.
2. Severe engine knock, which is identified as
a loud knocking or pinging sound in the
engine, should not be ignored because it can
cause engine damage. If switching to higher
octane does not solve the problem, see your
mechanic.
3. The octane number is simply the measure
of the antiknock performance of a gasoline.
Most cars only need regular (87) octane to
resist engine knock. Some sports and luxury
cars need higher octane (89 or 92) because
they have high-compression engines. In
general, higher octane gasoline will not
increase your car’s power or acceleration.
4. Unless your engine is knocking or pinging,
you car won’t benefit from higher octane.
5. As a rule, high octane gasoline does not
outperform regular octane in cleaning engine
deposits. In fact, the law requires that all
octane grades of all brands of gasoline
contain engine cleaning additives to protect
against the build-up of harmful levels of
engine deposits during the expected life of
your car.
6. Using high octane every few tankfuls in a
car that does not knock on regular gasoline
provides no benefit to your car, and is simply a
waste of money.
7. Most cars will run properly on the
recommended octane throughout their lives.
However, a small percentage of cars may
develop engine knock, and will need higher
octane.
8. Occasional light knocking or pinging won’t
harm your engine, and doesn’t indicate a
need for higher octane. In fact, light knocking
is often an indication that your engine is
performing at peak efficiency.
9. There is no scientific evidence that higher
octane burns cleaner or pollutes less than
regular. In fact, high octane gasoline
consumes more energy to produce at the
refinery and, in that sense, is worse for the
environment.
ANY QUESTIONS?
|
SuperDak
Dodge Dakota
10/10/2001
23:43:26
| RE: Octane
IP: Logged
Message:
nope...i just use plain old 87 and not a hint of pinging
|
jat
Dodge Dakota
10/11/2001
02:35:08
| RE: Octane
IP: Logged
Message:
I used to run 87 in my 4.7 but is was always pinging. started rund 89 and it took almost all the pinging away. Installed a JET stage II chip and started running 92 because that's what they recommend. No pinging at all with premium. I don't think the 4.7 has a knock sensor. If it does mine didn't work. jat
|
kota on 20s
Dodge Dakota
10/11/2001
02:46:38
| RE: Octane
IP: Logged
Message:
just wondering if higher octain does no good, why do people run 110-118 octain (aviation fuel) at the track? at $4-7 per gallon that would be a big wast of money
Eric
|
G. Cowardin
Dodge Dakota
10/11/2001
09:31:32
| RE: Octane
IP: Logged
Message:
Yeah, most of them are wasting their money. But if somebody has a supercharger, then they want to be safe. I think that I will run 89 and then 93 when I put in a chip. Which won't be long...
|
Erik
Dodge Dakota
10/11/2001
10:40:41
| RE: Octane
IP: Logged
Message:
kota the pople at your track or either wasting their money on overkill or running race engines at high compression. i would run a higher octane gas at the track especially if you are running a super or turbo. sometimes these power adders are "tweaked" for track use to got a little more boost for the 1/4 requiring a little higher boost, cause you dont really want the pinging or power loss especially if you are running really hard. but i agree with everyone else in that, it just aint gonna help a stock motor.
|
bernd
*GenIII*
10/11/2001
11:20:42
| RE: Octane
IP: Logged
Message:
The Race Fuel found at your local speed shop or racetrack is not "Aviation Fuel"...there is a difference.
However, the race fuel is much more refined and does help in most modified cases (90-100% stock...it's a waste).
With the "Chips" and PCM's out there, 99% of them advance the timing to gain you more TQ and HP...this requires the use of slower burning fuel (aka: High Octane). Since the spark is being ignited at an earlier point in the cycle, this requires that the fuel burn slower to provide as much force on the power stroke. (Suck, Squeeze, Bang, Blow - 4 Stroke)
1997 Dodge Dakota SLT - V6
Supercharged @ 10# w/Nitrous
|
G. Cowardin
Dodge Dakota
10/11/2001
13:44:54
| RE: Octane
IP: Logged
Message:
Its not slower burning, it justs is slower to "pre-ignite" or detonate. This means that you can compress it a lot more before the spark occurs. Just like a diesel, if you compress it, it will ignite if hit has a lower octane. In a gas motor if compression or pressure is too high, like when its air intake charge is warm, the gas will pre-ignite or detonate. That's why I would suggest 93 when, or at least 89, when it is hot. BTW, octanes are separated by gravity. That's why there is no such thing as a gas truck hauling 93. The truck pulls up, whatever is on the bottom is 87, and whatever is on the top is 93, and now you know why they call 89 mid-grade. Cuz its just the stuff in the middle. Later
|
bernd
*GenIII*
10/12/2001
16:41:17
| RE: Octane
IP: Logged
Message:
There IS a difference in fuels - aside from the octane rating.
Different fuel blends burn at different rates under the same temperatures and pressures. Absolute fact.
Peak cylinder pressure, for best power output, MUST be timed to occur around the top of the stroke. Fact, absolutely.
To tune for maximum power, you would like to use a fuel that burns at the quickest possible rate - without "knock" (there - that covers preignition and detonation) so you can initiate burning at the latest possible time and still produce peak cylinder pressure at around TDC. That way, the rising cylinder pressure pushes back down on the top of the rising piston for the shortest period of time - decreasing power lost there.
Octane?
If you look at the octane rating as only an indicator of what the fuel was designed for, you'd guess that a 120 octane fuel was probably designed for an engine that was prone to "knock" - like an older American V8 with relatively poor cooling and high compression. That fuel will be blended to burn at controllable rate that matches the high pressures and temperatures present AND resist "knock". A good match for those V8 engine conditions.
Burn Rates- That's the ticket!!
If you take that same fuel that worked well in the above V8, and run it in an engine with a lower cranking compression and lower combustion chamber temp, it will, without a doubt, burn much too slowly at those lower temps and pressures and reach maximum cylinder pressure too far after TDC for best power.
Things generally burn slower when they are cooler and vice versa. Peak cylinder pressure will occur much past TDC - decreasing the power produced if you keep the same ignition timing.
You can advance ignition timing to try to recover power, but that will cause the air/fuel mixture to burn earlier in the crank stroke and spend, percentage wise, more of the energy produced by the expanding, burning mixture, pushing back down, trying to prevent the piston from rising up to the power stroke - robbing power.
If you MUST use a slow burning fuel, which USUALLY has a high octane rating, advancing the ignition timing will lessen the power loss, but the best results are usually obtained with the quickest burning fuel obtainable, that, of course, doesn't "knock".
All other factors being the same, except for burn rate - use the quickest burning fuel that doesn't "knock", light the spark in the middle of the combustion chamber, adjust ignition timing to reach peak cylinder pressure ~TDC and keep your mixture correct. When the ignition timing is correct, the engine will make best power for that fuel.
There is a difference in the burn rates of different brands of fuels that are available. Some compliment one engine and some compliment the existing tuning of a different type of engine.
Does using a fuel with higher octane numbers automatically make more power?
Not unless they are preventing "knock".
Is there a difference in standard street pump premiums?
Yes. ~1%-2% power output. Try a few and use the brand that works best in your vehicle.
Energy content?
There is a really SMALL difference in different pump premiums - depending on the fuel recipe - I'd suspect a insignificant difference - like .01% power difference.
Is there a difference in 100-105 octane race fuels as compared to street pump premium when used in a your engine?
Yes. Some of the best WILL ADD, without a doubt, repeatably, no question about it, 3%-4% power improvement (under 2.6% oxygen content and without nitrobenzene or related compounds). Some of the 100-105 octane race fuels that were not designed for high revving, low compression engines don't work very well at all - making roughly the same power as pump premium.
Some more information:
http://www.medfordfuel.com/octane.htm
Just read before you post. ;)
1997 Dodge Dakota SLT - V6
Supercharged @ 10# w/Nitrous
|
surferpug
Dodge Dakota
10/12/2001
23:50:49
| RE: Octane
IP: Logged
Message:
Never run aviation fuel in a car with a Cat, since aviation fuel is slightly leaded, this will damage any exhaust component
|
teamfast
Dodge Dakota
JOIN HERE
1/31/2002
20:07:55
| RE: Octane
IP: Logged
Message:
bump for mig-29...
|
scat pack
GenIII
2/01/2002
15:58:01
| RE: Octane
IP: Logged
Message:
wish mine needed 93 !
2K RC 4.7 4x4
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
