The more you know the more you grow!

 

Just a thought but I try and get away with using as low octane fuel as possible for 2 reasons. 1. With a higher octane fuel you get harder starts espically in cold weather (just my findings) because it is more resistant to predetonation. 2. For shot sprints you want a fuel that will burn eaiser to make the most of your power. My engine builder used to race flat track and ice racing and he said for short sprints use low octane fuel and for motorcross etc.. use a higer octane fuel because of increased temps. Just my 2 cents

 

Octane has nothing to do with performance. Octane does not increse the amount of "energy" in the fuel. It determines how fast the fuel will ignite and burn. Laws of chemistry tell us that as you increase the compression of a gas or liquid it will heat up to the point where it will combust without a spark...knocking and pinging! More octane is needed to control or slow down this process of uncontrolled ignition. If your quad runs fine on 87 or 89 octane don't mess with it unless you plan on towing a ton of weight and then some extra octane will be a good safety margin. However the premium fuel usually contains a bit more additives for engine cleaning. Compression and timing effect how much octane you need. Too much of either and you have to increase the octane. Octane only effects the rate of burn. You need more oxygen and fuel to make more power not octane!

 

p0opeYpAntZ,
You said "Racer18J, your analogy that high octane fuel makes more power because it burns slower is incorrect."! I hate to tell you, but you are the one who is incorrect.

I have worked at a machine shop for 5yrs that does motor work for Ron Krisher (NHRA Pro Stock), he quilifies top 5 at every meet. Anyway, I have a dyno sheet in front of me that has a 480 hp sbc, just changing the fuel and nothing else, had a gain of 34 HP. We changed the fuel from BP 93 octane to VP Red 114 octane. If you would like, I will scan this dyno sheet so everyone can see it. Racers do not run higher octane fuel because they like to spend money, they do it because it makes more power.

There are way too many variables to add to explain about fuel and power. Every motor combination accepts fuel and makes power in a unique way. I'm sure you have some idea of the basics (so do I), but unless you are an engine expert and a chemist, all these variables are way to deep to follow. So I'm not even going to get into it. In my post I was not getting technical because I wanted the average person to follow what I was saying. But everything I said is the basics. We could be here all day saying stuff like "fuel burns in the center of the piston", that true "but if you add a bigger bore it's not true". ect.......

 

i could use some help on my homework for school.Just kidding.This is the part of the forums that i find most interesting.I have a very basic(and dangerous)mechanical ability.Keep slugging it out.MY QUESTION IS not quad but car related.
1. 1998 Caddalic northstar-35 to 50 degrees level road run mid grade fuel. Manual call for supper.
2. the computer should auto retard the timing?
3. any harm from diong this cheap? if something does'nt seem right back to prem.
4.1987 Buick grand national in every day driving should the computer or wastegate take that in mind as you are driving. I don't drive the gn much as i would like-my delima is that it curruntly has a 1/2 tank of 6 month old prem in it.Should i feel it up and carefully run it out?add some booster and run it out?after it is out fill it full,1/2,1/4??? warm it upandrive 15 miles 2 times a week??i would appricate your help on any of this questions

 

14mins stated: (snip)
<<1. 1998 Caddalic northstar-35 to 50 degrees level road run mid grade fuel. Manual call for supper.
2. the computer should auto retard the timing?
3. any harm from diong this cheap? if something does'nt seem right back to prem.>>

Northstar engines are designed to run on Premium fuel, 92 octane or better. While they will run on regular or mid grade unleaded you will see a decrease in performance since the knock sensor detects the uncontrolled combustion of the fuel and it retards the timing. Run what it says to run. If you can afford the car you should be able to afford the fuel.




<<4.1987 Buick grand national in every day driving should the computer or wastegate take that in mind as you are driving. I don't drive the gn much as i
would like-my delima is that it curruntly has a 1/2 tank of 6 month old prem in it.Should i feel it up and carefully run it out?add some booster and run it out?after it is out fill it full,1/2,1/4??? warm it upandrive 15 miles 2 times a week??i would appricate your help on any of this questions>>


The wastegate on a turbocharged vehicle does nothing more than dump boost once a preset level is reached. The GN's wastegate is vacuum operated and it doesn't care what octane fuel you use since it doesn't monitor the fuel. The ECM also has no provisions for modifying timing based on a fuel's octane rating. The ECM can modify it based on output from other sensors but thats preset and once again has nothing to do with the fuel you use. GM's ecm's have whats called a limp mode that will set the timing to a pre-determined level in case of catastrophic computer or sensor failure. The car runs like crap in that mode but it will get you home.

Your best bet is to dump a bottle or two of drygas in the tank since, after sitting for a few months, the fuel will absorb a fair amount of moisture. Running a bottle or two of fuel injector cleaner, preferrably Chevron since it's one of the best over the counter injector cleaners will help. You're could run into a problem with some varnish buildup on the injectors but running those chemicals through it should make a difference. Go out and give it an "italian" tune up. Run the hell out of it, within reason of course and that should be all it needs. Also, do NOT use regular unleaded fuel in that car since you can do serious damage once the engine is warmed up. Boost and low octane do not mix.


Hope this helps.

Phil

 

Phil-thanks for the answers.the question on the caddy was not phrased right.in cool temp,wife driving 65mph down the freeway,midgrade fuel who would notice the difference.? I am not worried about the extra 25cents a gallon. Under a situation like that i was of the impression it did not take much power to maintain that speed hence less need to have higher octane. Any way not going to tear the caddy up to save a couple hundred dollars of fuel a year.Would my 1-ton crewcab truck benifit in the summer using prem. unlead,pulling a 8000 pound trailer. The owners manual says 87 octane alright. Would the engine make more power under this situation due to the ecm retarting? or be back to where it should have been to start with?

 

If you are getting detination it dosent mean that the spark is fireing at the wrong time. Detination occurs when the piston is on the compression stroke and the the heat generated by compression ignites the air fuel mixture. If you doubt me run karosine in your lawnmoer start it let it run than pull the plug wire I bet you 9 times out of 10 it keeps running.

BooBoo

 

14mins asked:

<>

Since the engine is designed to run on 92 or better you would probably see an offset in mileage that would likely be made up by the reduced cost of midgrade fuel.

<<I am not worried about the extra 25cents a gallon. Under a situation like that i was of the impression it did not take much power to maintain
that speed hence less need to have higher octane.>>

Remember the rule, unless the fuel is made up of a completely different set of matrices, that is the chemical properties of the fuel are different which would yield a gain in performance simply because it had a higher energy content per gallon, you'd notice a difference. But...you are correct. I would make an educated guess that the Caddy only needs about 10-15 HP in a steady state cruise at 55-60 mph.


Any way not going to tear the caddy up to save a couple hundred dollars of fuel a year.

I'd be surprised if you spent that much extra per year for premium unleaded. Stick with at least 92 octane fuel.


<<Would my 1-ton crewcab truck benifit in the summer using prem. unlead,pulling a 8000 pound trailer. The owners manual says 87 octane alright. Would the engine make more power under this situation due to the ecm retarting? or be back to where it should have been to start with?>>

You didn't specify what kind of truck it is but unless you hear or feel ANY decrease in performance from pulling, other than the load hanging out back, switching to premium only lines the pockets of the oil companies. Listen for knocking. And no the engine will NOT make any more power using premium fuel. As someone said here, the only difference might be in the amount of detergents in the fuel.

If it knocks, use premium and see about cleaning the injectors,fuel system, etc... Many shops have top end cleaning systems that do a fantastic job of cleaning the crud out of the upper end of the engine. I used to use a particular set up where a clear flexible plastic tube went in downstream from the mass airflow sensor. You plugged a can into a special valve/hose assembly. Started the engine and turned the valve on. You controlled the amount of air, which is important because you want far more of the cleaning solution than air to enter the engine. This is to "wet" the induction system and the valves, piston crowns, combustion chambers,etc... Let me tell you, it made one HELL of a lot of thick white smoke You simply hold the throttle WFO and it's wheezing because it's getting so much "fuel". You also disconnect the factory fuel system from the loop so it runs entirely off the solvent. It takes longer to hook the system up than it does to clean the engine.

It's something to consider...and if done properly, it works wonders on engines with a bit of mileage on them.

My experience with running a repair shop has been those that run their cars HARD tend to have much cleaner top ends and much less oil contamination than those folks that baby their autos. I always drive my vehicles like I stole them, ATV's included

Ask away...

Glad to be of assistance.


Phil

 

Phil- thanks for spending the time to go back over the questions that i posted.I enjoy reading replies like this over the ones that state my xyz quad goes 200 mph. I wish i had alittle better mechanical grasp of how some thing works. Thru these replies i feel that i can learn some. As they say a little knowledge can be dangerous.Thank you.