Octane... - CEG Archives

And for those SVT owners even THINKING of running anything other than premium DON'T DO IT.

It's totally lame and of course damagin to the engine. And when you do the math you are saving about $3 per fillup, which is nothing in comparison to a new engine!

Take your savings (per fill up) and add in the fact that you are getting worse gas mileage, causing more frequent fillups and you will see that you aren't saving more than a $1.00 (if that) while causing damage to an engine.

("knock sensor will catch it" is a false statemnt, too, so don't go there.. the knock sensor operates BY DETECTING KNOCK... it has to HAVE HAPPENED, before it can do anything... once the sensor sees it, its too late...)

Ray

Originally posted by Ray:
Take your savings (per fill up) and add in the fact that you are getting worse gas mileage, causing more frequent fillups and you will see that you aren't saving more than a $1.00 (if that) while causing damage to an engine.

("knock sensor will catch it" is a false statemnt, too, so don't go there.. the knock sensor operates BY DETECTING KNOCK... it has to HAVE HAPPENED, before it can do anything... once the sensor sees it, its too late...)

Ray

wrong.

Originally posted by SVT Owners manual supplement:

right...and we all know the factory is always right!

Originally posted by 99cougar:
right...and we all know the factory is always right!

Errr...so who's the final authority then?

Originally posted by b0mbrman:

Originally posted by 99cougar:
right...and we all know the factory is always right!

Errr...so who's the final authority then?

Ray.

Originally posted by guitarman19853:
Originally posted by SVT Owners manual supplement:

"Wrong", as you put it.

But, thank you for pointing out exactly what I just said..

"The knock sensor will adjust engine calibration..." I take it you agree with this logic as its in the picture you hosted.

Now, back to what I said... In order to ADJUST the engine.. it has to DETECT..... *awkwardly long pause*.... KNOCK.

Which means that if the sensor IS adjusting the engine, that KNOCK has already occured. You're not gonna tell me that you think the FIRST knock is a freebie, and all the REST are the damaging ones, are you?

The sensor is not a magic fix. And, fwiw, engine calibration adjustment (via knock sensor) is not a split-second thing.. Changing the logic the car uses is a gradual thing.

Ray

guitarman do me a favor and sell your SVT - being a cheap-ass with a high performance car is pathetic.

PS the knock sensor and ECU can only retard the timing to a certian point and then it can STILL knock and the ECU will NOT pull any more timing. PLUS when it pulls timing it ADDS fuel and thus your milage gets worse, so you use more fuel and therefore you just negated any savings you made by trying to be a smart-ass tight-wad and use craptastic tractor piss gas! I'd love to see how speckled the tops are you pistons are from use low gr4ade fuel

oh and PPS: when you can HEAR pinging with you ears it's already to late!

There are those of us who KNOW how the EEC-IV works and those of us who THINK they know - you fall into category two.

Originally posted by Stazi:
guitarman do me a favor and sell your SVT - being a cheap-ass with a high performance car is pathetic.

PS the knock sensor and ECU can only retard the timing to a certian point and then it can STILL knock and the ECU will NOT pull any more timing. PLUS when it pulls timing it ADDS fuel and thus your milage gets worse, so you use more fuel and therefore you just negated any savings you made by trying to be a smart-ass tight-wad and use craptastic tractor piss gas! I'd love to see how speckled the tops are you pistons are from use low gr4ade fuel

oh and PPS: when you can HEAR pinging with you ears it's already to late!

There are those of us who KNOW how the EEC-IV works and those of us who THINK they know - you fall into category two.

okay... I dont use regular in my SVT. I use 93 if you must know. I just get absolutely annoyed when people say it cant be used. I'll wrap up my position on this in 2 statements:

1. "regular gas" is of no lesser quality than permium. it is made the same. Lower octane's just burn faster than higher. It has nothing to do with being "craptastic tractor piss gas"

2. heres my reasoning for everything (in relation to this). The FORD MANUAL says that you CAN use regular in the SVT (Yes i know it reccomends premium). It also says in there that it can be done without damage to engine components. So according to ford - no damage! HOWEVER i do realize that it is not always right. But, if the engine should get damaged, it SHOULD be repaired for free (and anyone that gets damage this way should argue this) because it is in the ford manual that there would be no damage.

Does this make sense? im not saying to use regular fuel. because then id be a hypocrite (sp?).

With gas prices going to hit over $4 a gallon, SOME people might not have the funds to continue to use premium and the knowledge that regular can be used might help out.

and just to make a point, premium is 20 cents more than regular. say you fill up your car once a week. for me (since i fill when the gas light comes on) filling takes about 12 gallons. .20 * 12 = $2.40 $2.40 * 52 weeks = $124.80 saved a year with regular. thats not some small amount, at least not to someone like me.

And it would take you 12.01 years to realize the cost savings of that amount to overshadow the cost of a new engine (SHOULD that one be damaged, etc, etc.. That is using a generous amount of $1500 on the low side for a new engine/labor)

I know.. how likely to ruin your engine, but..
How much damage COULD it be doing?, over the course of 11.9 years?

Unless you expect your engine to last 12 + years, you wouldn't even begin to get back in the black. Your engine will die before that, and the 124.80 a YEAR you saved will be gone quicker than you can count.

Ray

Originally posted by guitarman19853:

and just to make a point, premium is 20 cents more than regular. say you fill up your car once a week. for me (since i fill when the gas light comes on) filling takes about 12 gallons. .20 * 12 = $2.40 $2.40 * 52 weeks = $124.80 saved a year with regular. thats not some small amount

Then some people should trade their car for a 4-banger.

In fact, IMO, if the cost of gas is really such an issue, than you should definitely be looking at a way cheaper/economical vehicle ... if you can't afford an extra 20cents per gallon, how can you afford maintenance ... unpredicted repairs ... mods ... even anything!

Originally posted by guitarman19853:
But, if the engine should get damaged, it SHOULD be repaired for free (and anyone that gets damage this way should argue this) because it is in the ford manual that there would be no damage.

Hmm... I wonder if anybody has tried to get Ford to do that yet, the "it should be repaired for free" portion.

We can't get ford to honor repair recalls on a "you HAVE to do it" basis, much less on a "you SHOULD do it!!" basis.

Ray

okay i was just trying to bring up a point. i did not mean to anger anyone. Like i said before, i dont, and would never use anything less than 93 in my car.

I think this should be stickied with the current gas crunch...

Originally posted by Ray:

("knock sensor will catch it" is a false statemnt, too, so don't go there.. the knock sensor operates BY DETECTING KNOCK... it has to HAVE HAPPENED, before it can do anything... once the sensor sees it, its too late...)

i can't tell you how many times i have had this conversation with mom. being a mom she is concerned about me. so she calls me every time some guy tells her i am wasting money on premium and explains (again) how i am wrong. i explain (again) what ray said. i have tried every method of explaining it to her short of sitting her down and giving her a full physics lesson.

bottom line:

can you technically use lower octane fuel in your csvt? yes
should you use lower octane in your csvt? no

engine knock
engine knock
engine knock, by stanford with pictures

I don't see the point in buying an SVT model, spending the extra $$$ over a reg v6 for a more powerful car, only to try and save money by putting reg gas in it. At the very least, you will have reduced performance and fuel economy because the high compression SVT engine is engineered for higher octane fuel. You may as well buy a, cheaper non SVT tour that will be happy with 87 octane, but will give you less performance.

Originally posted by dutchie:
I don't see the point in buying an SVT model, spending the extra $$$ over a reg v6 for a more powerful car, only to try and save money by putting reg gas in it. At the very least, you will have reduced performance and fuel economy because the high compression SVT engine is engineered for higher octane fuel. You may as well buy a, cheaper non SVT tour that will be happy with 87 octane, but will give you less performance.

Eaxactly!

agreed, and anyone who thinks otherwise can read the links and realize thinking otherwise is incorrect

I have not run anything less than 91/93 in my CSVT. However, on a very similar platform (SHO) I have and do run 87 in it (typically though only in cold weather and on highway trips) and have had no issues. In theory, you could then do the same on a relatively stock CSVT.

Originally posted by RTStabler51:
I have not run anything less than 91/93 in my CSVT. However, on a very similar platform (SHO) I have and do run 87 in it (typically though only in cold weather and on highway trips) and have had no issues. In theory, you could then do the same on a relatively stock CSVT.

All because you wanted a quarter pounder meal at McDonalds.

Seriously, that's about all you can buy with the extra $3.00 you save yourself on a fillup.

Mark

Actually, no, I did and do it because I can, simple as that.

Originally posted by Y2KSVT:

Originally posted by RTStabler51:
I have not run anything less than 91/93 in my CSVT. However, on a very similar platform (SHO) I have and do run 87 in it (typically though only in cold weather and on highway trips) and have had no issues. In theory, you could then do the same on a relatively stock CSVT.

All because you wanted a quarter pounder meal at McDonalds. Seriously, that's about all you can buy with the extra $3.00 you save yourself on a fillup.

Mark

You can even get a quarter punder mealk with that. Maybe two $1 menu hamburgers, with tax.

Maybe that explains why my Hybrid pulled on your Hybrid with PnP'd heads?

Originally posted by RTStabler51:
Actually, no, I did and do it because I can, simple as that.

Originally posted by Y2KSVT:

Originally posted by RTStabler51:
I have not run anything less than 91/93 in my CSVT. However, on a very similar platform (SHO) I have and do run 87 in it (typically though only in cold weather and on highway trips) and have had no issues. In theory, you could then do the same on a relatively stock CSVT.

All because you wanted a quarter pounder meal at McDonalds. Seriously, that's about all you can buy with the extra $3.00 you save yourself on a fillup.

Mark

Mark

Go ahead, make your jokes, Mr. Jokey... Joke-maker. But let me hit you with some knowledge. Quit now. Save yourself the embarrassment of losing with these losers in the Mid-West, Stazi.

"Nobody makes me bleed my own blood"

Mark

Originally posted by guitarman19853:
and just to make a point, premium is 20 cents more than regular. say you fill up your car once a week. for me (since i fill when the gas light comes on) filling takes about 12 gallons. .20 * 12 = $2.40 $2.40 * 52 weeks = $124.80 saved a year with regular. thats not some small amount, at least not to someone like me.

First off, this isn't a stab directly at you, but moreso an attempt to knock some sense into the people who think they are saving oodles of money.

There is a flaw in your logic. In order for this to be a true comparison, you must take into account the MPG drop you'll suffer from. We'll call it .5% as a safe (possibly even low) estimate.

So let's do the math.

We'll say an SVT gets 23 MPG on premium, so 99.5% of that is just shy of 22 MPG on regular.

Now take the 14.5 gallon tank, effectively your losing usefulness of .5% of that. So your 14.5 gallons is getting your the same distance that 13.7 gallons of premium would get you.

Now for the price per distance comparison.

Regular 2.40
Premium 2.60

14.5 * 2.40 = 34.80
13.7 * 2.60 = 35.62

0.82 more to use premium based on a low .5% MPG drop.

Someone would have to be out of their mind to put their engine in possible danger only to save $42.64 a year.

Originally posted by my csvt:
engine knock
engine knock
engine knock, by stanford with pictures

You should remove the link to the how stuff works page. The octane rating is not a rating of compression ignition it is a rating of how fast the flame front spreads. Gasoline engines do not run on the compression ignition principle because the ignition point is at too high of a temperature unlike diesel engines.

What the problem with low octane fuel is as compression ratio goes up the fuel burns more quickly. The SVT has the same compression ratio as the non-SVT, so can technically handle regular gas. But to get more out of each combustion the spark event is started sooner. With the regular gas this early spark can cause the combustion to reach higher pressures sooner causing engine problems. When the Ford manual says that the computer will account for it it means that it will adjust the spark later in the stroke.

It was nice to see that nobody (in this thread) has referred to there actually being octane in the gasoline.

Actually, the SVT does have a higher compression ratio...

Per Greg's site
2.5L

44.5cc = 9.70 to 1

50cc = 8.91 to 1

44.5cc 98-99 SVT = 10.02 to 1

44.5cc 00 SVT = 10.31 to 1

50cc 98-99 SVT = 9.28 to 1

50cc 00 SVT = 9.49 to 1

Originally posted by Bugzuki:

What the problem with low octane fuel is as compression ratio goes up the fuel burns more quickly. The SVT has the same compression ratio as the non-SVT, so can technically handle regular gas. But to get more out of each combustion the spark event is started sooner. With the regular gas this early spark can cause the combustion to reach higher pressures sooner causing engine problems. When the Ford manual says that the computer will account for it it means that it will adjust the spark later in the stroke.

Originally posted by Faze Away:

First off, this isn't a stab directly at you, but moreso an attempt to knock some sense into the people who think they are saving oodles of money.

There is a flaw in your logic. In order for this to be a true comparison, you must take into account the MPG drop you'll suffer from. We'll call it .5% as a safe (possibly even low) estimate.

So let's do the math.

We'll say an SVT gets 23 MPG on premium, so 99.5% of that is just shy of 22 MPG on regular.

Now take the 14.5 gallon tank, effectively your losing usefulness of .5% of that. So your 14.5 gallons is getting your the same distance that 13.7 gallons of premium would get you.

Now for the price per distance comparison.

Regular 2.40
Premium 2.60

14.5 * 2.40 = 34.80
13.7 * 2.60 = 35.62

0.82 more to use premium based on a low .5% MPG drop.

Someone would have to be out of their mind to put their engine in possible danger only to save $42.64 a year.

how do you know there will be a drop in MPG? people say that but from what i know (from a previous discussion about this on here) noone has actually tried regular in an SVT and done an exact comparison on the difference. Has anyone done this? Yes i agree that there would be a loss in performance... but that doesnt mean that it will lose fuel economy

Originally posted by guitarman19853:

Originally posted by Faze Away:

First off, this isn't a stab directly at you, but moreso an attempt to knock some sense into the people who think they are saving oodles of money.

There is a flaw in your logic. In order for this to be a true comparison, you must take into account the MPG drop you'll suffer from. We'll call it .5% as a safe (possibly even low) estimate.

So let's do the math.

We'll say an SVT gets 23 MPG on premium, so 99.5% of that is just shy of 22 MPG on regular.

Now take the 14.5 gallon tank, effectively your losing usefulness of .5% of that. So your 14.5 gallons is getting your the same distance that 13.7 gallons of premium would get you.

Now for the price per distance comparison.

Regular 2.40
Premium 2.60

14.5 * 2.40 = 34.80
13.7 * 2.60 = 35.62

0.82 more to use premium based on a low .5% MPG drop.

Someone would have to be out of their mind to put their engine in possible danger only to save $42.64 a year.

how do you know there will be a drop in MPG? people say that but from what i know (from a previous discussion about this on here) noone has actually tried regular in an SVT and done an exact comparison on the difference. Has anyone done this? Yes i agree that there would be a loss in performance... but that doesnt mean that it will lose fuel economy

Because as cheap as most CEG'ers are, the SVT owners still aren't dumb enough to run less than premium fuel.

Mark

It kills me how people cannot bear the idea of 0.20 per gallon to keep their engine running their best, but will gladly spend their money on other "unecessary" things like cigarettes, food, booze, etc. Seriously, I'm SURE there are other ways to save a farking $2.40 per week, that putting cheap gas in your car which might cause engine problems in the long term.

Originally posted by akrump47:
It kills me how people cannot bear the idea of 0.20 per gallon to keep their engine running their best, but will gladly spend their money on other "unecessary" things like cigarettes, food, booze, etc. Seriously, I'm SURE there are other ways to save a farking $2.40 per week, that putting cheap gas in your car which might cause engine problems in the long term.

EXACTLY!! People piss away $2.40 without even thinking about it. $.70 into the vending machine here, buying a soda at the gas station there, etc.. Are you going to be that much more outraged over a $35.00 gas bill, than you would a $32.00 gas bill? Gas prices are high and you're taking it in the arse, but it's not like going to regular gas is going to lube you up for the bill!

And for anyone to say that they are going to take that $2.40 that they saved and put it into a piggy bank, or a seperate savings account, they're full of crap!

Mark

correct me if im wrong but....iirc engine knock can and has ruined an engine....so that 2.40 actually becomes more like $2500 to fix the motor...definately worth the savings!...im gonna go fill up with 87 octane right now....
-Shawn

Blowing up the engine is a good way to justify a 3L conversion.

Originally posted by Bugzuki:
Blowing up the engine is a good way to justify a 3L conversion.

oh great thats all i need...a GOOD reason to damage my engine...my wifes gonna love me hangin around you folks...lmao

I've been avoiding this thread, but now I'll jump in.

I'm extremely picky about how I take care of my cars.

I have a lot of accumulated experience with many high performance cars.

I have a lot of knowledge gained from schooling as well as from personal experience about taking care of cars.

I run 87 octane in my SVT.

I'm not crazy or ignorant. I know what I'm doing.

I have run both 87 and 91 (highest available in California) in it enough to determine that there is absolutely no difference in how it runs or what the fuel consumption is.

As long as I can tell no difference, I'm not spending the additional money for higher octane.

I've owned the car since new. In that time there has been only two times that ANY ping has been observed. Both times (over a year apart) it was on a warm winter day (we get a lot of those in California) with winter blend fuel. There was a very slight part throttle cackle that went away with just a very little bit more throttle. I can live with that.

This has not been the case with any other high performance car I have owned. If it needed premium fuel, it got premium fuel.

As long as I take good care of mine (agressive maintenance) and it doesn't need premium fuel, it probably won't get it.

Normal disclaimer -- your results may vary.

So.. You're saying (as you and I have discussed on a personal basis more than once) that if you are ANALLY RETENTIVE about the maintenance you do on your car, withold nothing from the actions and cleaning you perform, and dedicate all but your first born to maintenance.... you will be fine?

AKA:99.9% of the readers of this post don't perform 2/3 of the maintenance required to place anything other than premium in their car, but those who are up to par with said maintenance procedures may not experience any adverse affects.

Ray

Originally posted by Big Jim:
I've been avoiding this thread, but now I'll jump in.

I'm extremely picky about how I take care of my cars.

I have a lot of accumulated experience with many high performance cars.

I have a lot of knowledge gained from schooling as well as from personal experience about taking care of cars.

I run 87 octane in my SVT.

I'm not crazy or ignorant. I know what I'm doing.

I have run both 87 and 91 (highest available in California) in it enough to determine that there is absolutely no difference in how it runs or what the fuel consumption is.

As long as I can tell no difference, I'm not spending the additional money for higher octane.

I've owned the car since new. In that time there has been only two times that ANY ping has been observed. Both times (over a year apart) it was on a warm winter day (we get a lot of those in California) with winter blend fuel. There was a very slight part throttle cackle that went away with just a very little bit more throttle. I can live with that.

This has not been the case with any other high performance car I have owned. If it needed premium fuel, it got premium fuel.

As long as I take good care of mine (agressive maintenance) and it doesn't need premium fuel, it probably won't get it.

Normal disclaimer -- your results may vary.

Just because your human ears cannot detect ping, doesn't mean it isn't happening. When you HEAR it with your own ears it is at a point where it is a BAD AS IT CAN GET. But at levels below your audible range it is STILL DAMAGING THE ENGINE. Next time you do a plug change, shine a light down the plug hole and look at the tops of the pistons. If they are speckled - which I can garantee you they will be, then YES, you are pinging and it is eroding way the face of the piston.

Jim, I'm really disappointed in you. Please don't be a stingy bastard in the name of saving $2!

When you run 87 it WILL pull timing as the knock sensor CAN detect ping even when yours ears can't. That REDUCES performance and REUDUCES mileage. If you think otherwise then you're sadly MISTAKEN. You've probably become so disensitized over the years of running 87 and are probably convincing yourself of no difference that you refuses to acknowledge the difference. For YOU only a dyno can prove that you are wrong. I have WITNESSED many SVT's trying to dyno with 87 and the operator INSTANTLY knows they are running less than premium gas as SOON as they get on it. From outside of the car we could hear ping even though the driver/operator inside the car couldn't. Also the dyno graphs told the tale - less power all across the rev range and worse as the rpms increased.

If you know say "Well I don't race the engine" or "I don't care if it makes less power" then I ask why in the hell do you have an SVT?? If it's for the looks or the leather interior then I say "Shame on you" because that's gay!

Jim - since you have over 200K on your engine you obviously know how to take care of the car despite running less than reccomended octane
- BUT -
Stazi is right, there is NO WAY your engine is running at its top performance or mileage on 87. Your spark timing is retarded and you are running richer than optimum. Now if you drive it real nice never run the egine to redline at WOT, maybe you won't notice anything. But if you dyno your car on 87 and then on 93 (after the engine has appropriately "learned") then you would undoubtedly see better results on premium.

Oh and why even bother running 87 winter piss blend? You yourself stated you heard a slight ping, so why even take the risk?

Here is what is happening to Jim's engine and anyone else who is putting cheap gas in their SVT:

http://www.caranddriver.com/article.asp?section_id=4&article_id=3604&page_number=1

Some quotes from the article:

"The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel."

"Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes."

Once again I say - If you want to save $2.40 a week, why do it by retarding your car's engine performance. I could save the cost of an entire months worth of premium but not eating lunch out once a month.

Originally posted by akrump47:
Here is what is happening to Jim's engine and anyone else who is putting cheap gas in their SVT:

http://www.caranddriver.com/article.asp?section_id=4&article_id=3604&page_number=1

Some quotes from the article:

"The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel."

"Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes."

Once again I say - If you want to save $2.40 a week, why do it by retarding your car's engine performance. I could save the cost of an entire months worth of premium but not eating lunch out once a month.

This is certaily not an issue that is going to be resolved on this thread.

This idea that detenation that you cannot hear is likely to do damage is not universally accepted. For example this is a quote from page 163 of my owner's manual. "Do not be concerned if your vehicle sometimes knocks lightly. However, if it knocks heavily under most driving conditions on the recommended octane, see yhour dealer or a qualified service technician to prevent any engine damage."

Actually, Ford even taught me in their traning programs that ocassional slight or trace ping is an indication that the engine has been optimally tuned. This was before computerized engine controls though.

Actually, I'm mildly disappoited that my car was factory tuned so that premium fuel is not that critical. I'm also disappointed that there has been so little equipment wise to enable me to tinker with the settings that I used to be able to do by hand.

In my capacity as a service manager, I have worked on and driven cars that had knock sensor systems that seemed to be much more sensitive to fuel grade than my SVT. Both Volvo and BMW come to mind, where you could substantually feel the difference.

If it makes you feel comfortable to think of me as studid or misinformed, then so be it. I am neither.

I dont think your stupid or misinformed, and your car obviously is in good shape to survive for 200K miles. It just dosent make sense to degrade performance, and have knocking and pinging, just to save a few dollars here and there. I'd rather put the good stuff in my tank and know that I can run my car hard, have maximum engine performance without any possible ill effects.

You should dyno your car sometime, with your preferred 87 octane, and see what kind of numbers it puts out and how much pinging there is under load. It would be interesting for comparison sake especially sice you claim to maintain it very well.

What have i started lol!

Originally posted by '99 Contour SE:
What have i started lol!

You started a ruckus. Most of this thread is lame.

You can run low octane fuel in your SVT, period.
Will it cause knock? Maybe. The chances are a hell of a lot better with low octane fuel.

Remember, the first thing that will happen when using poor grade of fuel is pre-ignition, or pinging depending on the load, outside temperature and timing.
Pinging isn't likely to damage the surfaces of the type of piston that we have in our motor.
This pinging will always precede full blown engine knock. The engine knock is what happens after preignition when the flame front (and overall cylinder pressure) gets high enough to slap the piston before the piston gets to top dead center, resulting in pushing against the piston as it comes up versus pushing it down on the downstroke.

So that tells you that preignition happens before the spark plug ignites the fuel and it happens a little too early so that a ping is made but the piston still travels over TDC in time so that the main force of the charge isn't against the piston movement.

The knock sensor is tuned to pinging and will operate as stated earlier in response to it. It will generally stop the pinging before it leads to knock.

Therefore you can run low octane fuel safely in cold weather or low load/highway cruise conditions. Mountain or hilly driving counts as HIGH load.
In summer time even low load conditions will result in pinging in a tuned performance motor and of course some motors will ping with low octane fuel at ANY time.

It is my experience with the duratec and 10:1 compression that 87 octane will suffice if ambient temps are 70F or less. 89 will work most of the time but IMHO it is a waste of money for what you get. 91 or better will always work and is a must for any temps above the 80F range.
If you drive agressively then 91 or better will always be the way to go unless the temps are really cool outside like in deep winter.

Originally posted by akrump47:
You should dyno your car sometime, with your preferred 87 octane, and see what kind of numbers it puts out and how much pinging there is under load. It would be interesting for comparison sake especially sice you claim to maintain it very well.

Pshhhhh! Dyno'ing the car costs ~$100.00. He'd have to save that $2.40 per fillup for close to a year to be able to afford it.

Mark

Originally posted by Y2KSVT:

Originally posted by akrump47:
You should dyno your car sometime, with your preferred 87 octane, and see what kind of numbers it puts out and how much pinging there is under load. It would be interesting for comparison sake especially sice you claim to maintain it very well.

Pshhhhh! Dyno'ing the car costs ~$100.00. He'd have to save that $2.40 per fillup for close to a year to be able to afford it.

Mark

pwn3d!

Honestly the though of people putting anything but Premium in an SVT makes me mad. Downright GAY!

Sorry but DON'T buy a performance car and then put cheap gas in it. Also I bet a lot of people who do this have power-mods like an exhaust, intake, etc. - which makes them oxymorons.

Originally posted by Big Jim:

<snip>
Actually, I'm mildly disappoited that my car was factory tuned so that premium fuel is not that critical. I'm also disappointed that there has been so little equipment wise to enable me to tinker with the settings that I used to be able to do by hand.
</snip>

It must not get that hot in your part of CA because mid summer temperatures in Phoenix make it evident that 91 octane is NOT enough. Knock or ping... I don't know, but the car definetely looses power after making a predet type sound. 100 octane resolves this issue, but is expensive... auto parts octane booster sometimes helps, unless I'm doing lots of city street driving.

So how about this... if you live where it can reach 120 degrees, drive with the a/c on, rarely let the secondaries close, and don't have enough faith in the knock sensor to risk your engine, then you CANNOT run less than 91 octane.

Temperature is a big factor in octane requirement. It is not nearly as hot where I live as Pheonix. If I lived in such a hot weather area I may see the need to increase octane.

However, even in hot weather for here (100 Degrees) I can climb either the grapevine grade on Interstate 5 (either direction, but northbound is steeper) or the Conejo grade on highway 101 with the A/C on holding 80 mph (probably more if I wanted to risk the ticket) with no hint of ping or power loss.

Actually I've climbed the Conejo grade much faster than that many times, but I don't remember if any of those times if it was over 100 degrees. It will climb the Conejo at 80 in 5th gear with the cruise control set with the feeling that it could do much more.

I guess that I can't quite get it across to you that I do understand octane. The last car that I owned that could be fully tweeked manually was a 1972 Ranchero. It came with a 429. When I threw a rod, I replaced the bottom end with a Lincoln 460 and added a Cobra Jet cam as well as a Super Cobra Jet intake manifold and liberally ported the heads to match. Carburation was from a Motrocraft 4300D that came off from a Pantera (850 cfm). I could play with the mechanical advance curve, the vacuum advance curve, the carb jetting, the trans shift points, and even the carb secondary openings to my hearts content. Others that drove it at the time referred to it as a bomb because of the explosive acceleration. I could come to a full stop at the foot of the Conejo grade and go over the top at over 120 with a full load of bricks in the bed. It was tuned so tightly to premium fuel that I would get a trace ping just from going from my house at about 1000 feet to a trip to the beach at near 0 feet.

My SVT just isn't near as sensitive, and I'm disappointed.

Originally posted by morbid:

Originally posted by Big Jim:

<snip>
Actually, I'm mildly disappoited that my car was factory tuned so that premium fuel is not that critical. I'm also disappointed that there has been so little equipment wise to enable me to tinker with the settings that I used to be able to do by hand.
</snip>

It must not get that hot in your part of CA because mid summer temperatures in Phoenix make it evident that 91 octane is NOT enough. Knock or ping... I don't know, but the car definetely looses power after making a predet type sound. 100 octane resolves this issue, but is expensive... auto parts octane booster sometimes helps, unless I'm doing lots of city street driving.

So how about this... if you live where it can reach 120 degrees, drive with the a/c on, rarely let the secondaries close, and don't have enough faith in the knock sensor to risk your engine, then you CANNOT run less than 91 octane.

Amen to that! I grew up most and spent most of my life in Tucson. It is hot there and hotter in Phoenix. I could never run less than 91 in AZ except maybe in the coldest part of winter (50F range

)

Originally posted by Stazi:

pwn3d!

Honestly the though of people putting anything but Premium in an SVT makes me mad. Downright GAY!

Sorry but DON'T buy a performance car and then put cheap gas in it. Also I bet a lot of people who do this have power-mods like an exhaust, intake, etc. - which makes them oxymorons.

The Vulcan Taurus has pinged for over a year now and no ill effects. It has 111K miles and it still runs wonderful. I understand your point about pre-ignition, but I don't think this is as much as a problem as you make it out to be. You might laugh at someone saving some money but not everyone cares about being a boy racer all the time and a penny saved is a penny earned.

People can do what they want and sometimes they know more than you do. The engine is not going to blow up from using 87 octane unless the driver is a fool and never kept his engine clean from carbon buildup and the like.

Originally posted by Majisto:

Originally posted by Stazi:

pwn3d!

Honestly the though of people putting anything but Premium in an SVT makes me mad. Downright GAY!

Sorry but DON'T buy a performance car and then put cheap gas in it. Also I bet a lot of people who do this have power-mods like an exhaust, intake, etc. - which makes them oxymorons.

The Vulcan Taurus has pinged for over a year now and no ill effects. It has 111K miles and it still runs wonderful. I understand your point about pre-ignition, but I don't think this is as much as a problem as you make it out to be. You might laugh at someone saving some money but not everyone cares about being a boy racer all the time and a penny saved is a penny earned.

People can do what they want and sometimes they know more than you do. The engine is not going to blow up from using 87 octane unless the driver is a fool and never kept his engine clean from carbon buildup and the like.

Now that's just plain dumb to me.
Continuous pinging is still harmfull. Small amounts of it are negligible but for a YEAR? I think Stazi pointed out that your pistons will have pits in them and this is kind of what he was talking about. Your pistons probably look like a small scale lunar surface if you ping all the time for a year (all the time means everytime you accelerate, not cruise).

I stated that the few initial pings befoe the knock sensor pulls some timing wouldn't hurt anything, but that was a very narrow statement with the purpose of pointing out that a knock sensor will save the engine from the damaging knock because it detects the light pings that precede it.

BTW, that's a TAURUS you're referring too, not a high performance car by a long shot. THe SVT is much closer to the realm of performance though some debate that it really is a performance car.