: how much extra HP will i get



capn
08-18-04, 08:36 PM
hey all

im trying to find out about how much extra hp i will get when i run 115 or 110 octane gas with my 93 N* that is

Mikethegreeat
08-18-04, 08:39 PM
holy crap ive been thinking the same thing man, im planning on going to irwindale speedway and run their 1/8 track tomorrow

they sell 100+ octane over there..

capn
08-18-04, 08:41 PM
holy crap ive been thinking the same thing man, im planning on going to irwindale speedway and run their 1/8 track tomorrow

they sell 100+ octane over there..


theres a better gas these days and its cheaper ;)

mcowden
08-18-04, 08:55 PM
I can tell you exactly how much of a horsepower gain you will see with a 4.6L Northstar V-8 engine and 110 octane racing fuel:

0 (zero)

The same goes for any other engine designed to run on normal pump gasoline. Octane doesn't give you horsepower. It makes it possible to increase the compression without causing detonation, and that's where the horsepower comes from. If you don't touch the compression, you won't see any performance gains from 110+ octane gasoline.

Check this out:

http://auto.howstuffworks.com/question90.htm

capn
08-18-04, 09:10 PM
that really doesnt explain if it will owrk in our engines, because of the computers and stuff in our engines its retarding the timing because of our fuel grade so with a higher grade fuel 100+ it would allow the computer to change the ignition timing and possibly free up Hp

mcowden
08-18-04, 10:18 PM
Well, the timing won't advance past its programmed set point. That's the sticking point. It goes to the limit it knows and no further. It's designed to run best on 93 octane gasoline. It doesn't know how to compensate for higher octane ratings because it has no idea you're using higher octane fuel. It only knows to retard the timing because there may be engine knock. That's the tip-off. I still say zero benefit.

capn
08-18-04, 10:26 PM
Well, the timing won't advance past its programmed set point. That's the sticking point. It goes to the limit it knows and no further. It's designed to run best on 93 octane gasoline. It doesn't know how to compensate for higher octane ratings because it has no idea you're using higher octane fuel. It only knows to retard the timing because there may be engine knock. That's the tip-off. I still say zero benefit.


well i'll just have to post times of 0-60 with and without 100+ octane and show my results

i say i'll get at least 10 hp

BeelzeBob
08-18-04, 10:54 PM
Technically you should get absolutely zero power from anything higher than 93 octane fuel. The compression ratio and spark advance is optimized for the engine for 93 octane fuel so additional octane will not provide any additional spark advance as there should be no detonation with 93 octane fuel and no resulting spark retard....

However....there is more to fuel and power than just the octane. The volitility of the fuel can affect the atomization of the fuel when it is injected which can affect the power especially at higher RPM's. Racing fuel/high octane fuel is often less volitile than normal pump gas (to avoid vapor lock in carbed racing engines) so there is a case to say that the racing fuel might be slower....but...it is hard to say without testing the racing fuel in question and also the pump gas you are buying.

I would guess that the differences are pretty small and the engine would likely be fine and running at maximum spark advance with somewhat less than 93 octane fuel anyway so I suspect the racing gas will do nothing in terms of improvement in power but it will be interesting to see if you can do the comparison.

Be aware that a direct comparision at the strip is very difficult as many things can change run to run that will affect performance so don't put too much stock into immediate results comparing fuel.

The engine is designed for premium 93 octane fuel under worst case conditions of high barometer, high temps, low humidity, etc...so as to provide the maximum power under worst case conditions for detonation. There should be none with 93 octane fuel so additional octane will do nothing. If you are under more humid conditions, lower temps, higher altitude, etc... then the engine will make max power even with lower octane fuel placing less and less dependence on having good gas to prevent detonation.


Remember also that a lot of premium fuel contains alcohol and the racing fuel will not. Alcohol makes the air fuel ratio leaner (10 percent alcohol in the fuel will result in a 5 percent lean condition at WOT) so if you are running pump fuel that contains alcohol and compare the performance with racing fuel without alcohol then that might cause some slight gain in performance totally independent of the octane rating.

mcowden
08-19-04, 11:25 PM
Man, Bbobynski, you're down to a meager, minuscule, diminutive 8.75 posts per day... The well at Lourdes is running dry! I remember the days of 10+... :D And don't give me that excuse of "I have better things to do..." On your feet, soldier! Quick, what are the dimensions of the intake manifold ports at the gasket and what material are they made of? How deep are the ring grooves on the pistons of a 1996 SLS? How often should you change a gonkulator valve? Why do light bulbs burn out? How much gas does it take to fill up the radiator of a 2002 DeVille? MOVE IT MOVE IT MOVE IT MOVE IT!!!

The Oracle speaks again. Thank you for your time and effort with Cadillac Forums. We all learn important stuff from your wealth of knowledge and it saves real people real time and real money. Your contributions are greatly appreciated.

Cheers! :cheers:
Michael Cowden

Mikethegreeat
08-20-04, 12:49 AM
yes, thank you Bbob i decided not to waste my money and use 100+ octane... but i did go to the track...forgot my shoes..so i didnt even get past inspection :p ill be going back next week

capn
08-20-04, 10:12 AM
well how abot 110.5 octane gas for 2.82?? thats cheaper then some premium gases over in cali :)

KHE
08-20-04, 11:29 AM
that really doesnt explain if it will owrk in our engines, because of the computers and stuff in our engines its retarding the timing because of our fuel grade so with a higher grade fuel 100+ it would allow the computer to change the ignition timing and possibly free up Hp

I would not expect any significant gains....but if you want to try it anyway, make certain that the fuel is UNLEADED or you will screw up the catalytic converter...

LymanSS
08-22-04, 05:30 PM
People need to think harder before they posts hard and fast statements. When someone tells you that high octane fuel will get you "zero" power gain without first taking a look at how the car is programmed he is probably just repeating what he heard somewhere else say, which is about as helpful as a kick to the crotch.

Here's the deal as far as I can tell after monitoring the Northstar in my 02 Deville under actual driving circumstances with a laptop and OBDII cable and software.

On 94 octane gas (which was available in my area untill a few months ago) in 65-70 degree weather (I don't know the humidity) the car was running about 2.4 degrees of knock retard fairly consistantly. Basically the car has a timing curve that's optimized for performance/economy/emmissions and to account for fuel quality they dial in a certain amount of knock retard. The management system will advance the timing as far as it can before knock occurs and then back off a bit - much like a real human tuning it by hand would....only more accurate. It seems that even on 94 octane gas the computer is still running more retard (2.4 degrees) than it has to . For this reason we can probably noticeable benefits by running higher octane fuel. If you just pour some in it might not do the trick....you might have to drive for a few tanks or perhaps pull the battery to reset the computer. The only way to really tell if you're getting the benefits you're seeking is to do multiple track runs and average them, dyno the car, or hook up a computer and watch what it's doing. In any case I'm convinced there's power to be had by running better fuel, but not a boatload. And the cost of 100+ octane fuel is pretty prohibitive.

Scott

dkozloski
08-22-04, 06:15 PM
It's interesting to note that the knock sensor works by detecting noise in a particular frequency range that indicates that engine parts are springing and deflecting from the stress of the fuel-air mixture detonating rather than burning progressively. You can test the sensor by rapping on the engine block with a plastic hammer and observing the speed decreasing as the spark retards. On a Mazda RX-7 the engine lifting ring is the specified striking point. The sensor detects the detonation long before it becomes audible to the driver. As the engine nears the destruction range you hear the customary pinging noise that resembles the sound of pea gravel hitting an iron pipe. The noise you hear is the sound of cylinder walls and other parts being deflected. Water cooled automobile engines will tolerate some degree of pinging but an aircooled aircraft or motorcycle engine can be destroyed in less than 30 seconds. A lean mixture has a much lower octane rating than a rich one. Some of the older Yamaha road racing twins would seize before you could get the clutch disengaged when they ran out of gas on the track. A typical automobile failure would be a hole through the head of a piston or a section of the piston head melted down into the rings. On teardown a common sign that the engine has suffered mild detonation is that the top edge of the piston looks like a mouse has been gnawing on it.

STS 310
08-22-04, 07:39 PM
well how abot 110.5 octane gas for 2.82?? thats cheaper then some premium gases over in cali

It aint that bad!

STS 310
08-22-04, 07:43 PM
[QUOTE=LymanSS]People need to think harder before they posts hard and fast statements. When someone tells you that high octane fuel will get you "zero" power gain without first taking a look at how the car is programmed he is probably just repeating what he heard somewhere else say, which is about as helpful as a kick to the crotch. Scott QUOTE]

I would believe BBOB if he told me my car would run on rat piss. Or give it some serious thought. Most of the "knowledgable" folks on here are well established.

But go on with your lap top if it makes you happy.

LymanSS
08-23-04, 12:40 AM
I would believe BBOB if he told me my car would run on rat piss. Or give it some serious thought. Most of the "knowledgable" folks on here are well established.

But go on with your lap top if it makes you happy.

Ok, go ahead with the rat piss if that's what floats your boat, but it won't change the 2.4 degrees of knock retard. I think even BBOB will tell you that getting 2.4 degrees of timing advance by eliminating knock will probably make more power. But go ahead and tell other people that they will get zero power gain from high octane fuel if it makes you happy. It doesn't matter a whit to me. I'm just sharing real world observations gained from actually working on these cars.


Scott

STS 310
08-23-04, 02:37 PM
Just trying to get a rise out ya Lyman:rolleyes:, wasnt try to say you dont know your stuff. Let us know what you find out.

BeelzeBob
08-23-04, 04:17 PM
People need to think harder before they posts hard and fast statements. When someone tells you that high octane fuel will get you "zero" power gain without first taking a look at how the car is programmed he is probably just repeating what he heard somewhere else say, which is about as helpful as a kick to the crotch.

Here's the deal as far as I can tell after monitoring the Northstar in my 02 Deville under actual driving circumstances with a laptop and OBDII cable and software.

On 94 octane gas (which was available in my area untill a few months ago) in 65-70 degree weather (I don't know the humidity) the car was running about 2.4 degrees of knock retard fairly consistantly. Basically the car has a timing curve that's optimized for performance/economy/emmissions and to account for fuel quality they dial in a certain amount of knock retard. The management system will advance the timing as far as it can before knock occurs and then back off a bit - much like a real human tuning it by hand would....only more accurate. It seems that even on 94 octane gas the computer is still running more retard (2.4 degrees) than it has to . For this reason we can probably noticeable benefits by running higher octane fuel. If you just pour some in it might not do the trick....you might have to drive for a few tanks or perhaps pull the battery to reset the computer. The only way to really tell if you're getting the benefits you're seeking is to do multiple track runs and average them, dyno the car, or hook up a computer and watch what it's doing. In any case I'm convinced there's power to be had by running better fuel, but not a boatload. And the cost of 100+ octane fuel is pretty prohibitive.

Scott


Point well taken. If you are referring to my post on the subject I will have to add that I am assuming that the fuel that you are buying is REALLY 93 octane fuel. Rarely is the fuel octane rating as good as the pump says....close...but who really knows. It is certainly possible to get lower octane fuel than is advertised on the pump.

The engine is set up and calibrated so that there should be little to no detonation and therefore no spark retard on 93 octane fuel. As I stated, there are extenuating curcumstances surrounding the temperature of the inlet charge, the ambient baro, the ambient humidity, etc...that ALL affect the detonation characteristics of the engine as well as the octane rating. That is why I said that I would expect no gain but if a small gain was achieved then it would be certainly explainable by one or more of the factors mentioned.

BTW...there are multiple spark tables in the system....I assume the "retard" you were seeing was from the optimum "premium fuel" table. If there is about 2 degrees of retard from that table then the engine is pretty darned close to the optimum output. The spark advance system works off of a base table that approximates the spark requirements for different fuel octanes at about sea level typical barometers/atmospheric pressures. If the system hears detonation it retards the spark to a lower base table and then starts advancing it to "see" if it can jump to the next table for higher octane. It is really a slow trim type system...not the very active "retard only" style of knock control that was used in yesteryear.


Even with a chassis dyno and different fuel octane ratings you would have to be very very careful making judgements on power gains purely due to the octane rating of the fuels tested. As mentioned, things like alcohol content and volitility can affect the overall power and performance more than just spark retard due to knock from lower octane.

Not that I totally disagree with you ..... but my info is a little better than a kick in the crotch. Not much maybe...but a little better. And it is condensed into a simple post. The subject could expand to a book to cover ALL situations, engines, knock systems, fuel quality, etc.......