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Page 133 in the November Car&Driver has an article that test an automatic GT with regular 87 fuel and then with Premium 91 fuel and says that the GT is .3 seconds quicker in the quarter and has 2 RWHP more when run with Premium. The article also states that the GT has knock sensors.

I dont think that the GT has knock sensors--nor does the Bullitt--am I correct?

And the article also states that coolant temperature differences between the two test on the same car was a factor in the how fast the car was and how much horsepower was made. This seems to negate the premise of the article--that the grade of fuel has an effect on the performance of the car. What confuses me is that the coolant temperature wouldnt have been that different--if the load on the engine and the engine RPM was the same during both tests on the same car. The ambient temperature would have an effect--it would effect the total timing advance of the car--but I cant see how the coolant temperature would be different--even if the ambient temperature was different( except for extreme ambient temperature differences). What do you guys think?



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2001 GT Premium
5 speed
Coupe

<font size=-1>[ This Message was edited by: phoneman91 on 2001-10-03 03:15 ]</font>
 

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<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-10-03 03:13, phoneman91 wrote:
Page 133 in the November Car&Driver has an article that test an automatic GT with regular 87 fuel and then with Premium 91 fuel and says that the GT is .3 seconds quicker in the quarter and has 2 RWHP more when run with Premium. The article also states that the GT has knock sensors.

I dont think that the GT has knock sensors--nor does the Bullitt--am I correct?

And the article also states that coolant temperature differences between the two test on the same car was a factor in the how fast the car was and how much horsepower was made. This seems to negate the premise of the article--that the grade of fuel has an effect on the performance of the car. What confuses me is that the coolant temperature wouldnt have been that different--if the load on the engine and the engine RPM was the same during both tests on the same car. The ambient temperature would have an effect--it would effect the total timing advance of the car--but I cant see how the coolant temperature would be different--even if the ambient temperature was different( except for extreme ambient temperature differences). What do you guys think?
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>

Hmmm. It seems like they are suggesting the lower octane fuel is causing the engine to run hotter. Thats possible I guess. If an engine was running premium as opposed to regular, cylinder heads tempertures would drop, in turn coolant temp would drop.

I was unaware of knock sensors on GT engines :???: But if the computer saw high coolant temp and higher exhaust temp, it probably would pull some timing out.

And as far as picking up three tenths with 2rwhp, thats a little hard to grasp. But maybe thats just a peak number and doesn't tell the whole story.

Funny thing is, this exact thing occured to me last week. I stepped up to 89 octane last Friday.
 

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To reduce ETs by .3 typically takes 30 horsepower.

That being said I have experienced spark knock running 87 octane. I now run 89.

Does anyone else get spark knock on 87 octane?
 

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My car has only 1000 miles, but has run very quietly on 87. I though all modern cars had knock sensors, the question was how many sensors? 1 per motor, 1 per bank of cylinders, or 1 per cylinder.
 

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the one time I ran 87 octane , my bullitt ran like crap...I don't know why, but it did
the moment I went back to 93 it was fine
sure it will ''run'' on 87 but what does that cost in performance etc..
 

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I ran 87 from day one. No pinging or knocking. Switched to 93 a few times but I didn't see any performance gains. 2759 runs great on the lower octane so I don't see any reason to pay the extra .15 per gallon. Funny how all the cars are supposed to be the same, but yet they all seem to be different.
 

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My car runs fine on 87 octane but if it pings I'd move a grade up. I find it hard to believe the octane rating would increase speed unless the car was knocking. More than likely the .3 increase was a coincidence. The times will be different every time. I am planning on switchhing to a synthetic oil like Mobil one which is so thin it does increase horsepower slightly.
 

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I thing that 2989 runs better on 93 octane gas,I know that my 88 5.0 does;I also know that my Eagle Vision TSI does.I think that the ECU on the Bullitt uses data from the coolant temp sensor as well as data from all of the oxygen sensors to modify timing on as needed bases,the main source of info being exhaust gas temperature.Detonation will increase both coolant temp and exhaust,causing a less than agressive spark curve.The only post that I have seriously doubted on this site was that some people have said that their Bullitt runs worse with higher octane fuel,I do not see this as possible.You can with the OBD 3 change your fuel octane requirements by programing in the octane of the fuel that you use.Their also is an improvement to be gained in a lower temp thermostat,it fools the computer into thinking that it is cold,which makes the car run in a closed loop mode where the fuel is richer the timing curve is more aggressive.Downside is heater is not as hot,condesation will not be evaporated out of engine oil as quickly,and converter life will be shortened as the richer mixture will allow more fuel to reach the catalyst.
 

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My Bullitt ran terrible on 87. Sometimes when I hit the throttle fast, the engine hesitated. I switched to 93 octane, no more hesitation. Runs awesome. I'm sticking with 93. :smile:
 

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Chevron 87 and not one ping even when lugging the engine or romping on it.
 

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The standard single cam motor does not have knock sensors, only the twin cam Cobra motor.

Mine ran fine on regular until a couple of weeks ago when , on a trip, I noticed some pinging. Filled up with premium and the pinging went away and the car seems a bit stronger.

If you have pinging and add a higher octane fuel, you will see a power increase because detonation will reduce the power output of a cylinder. If you are not getting any audiable pinging on regular, no reason to change.

Brian
 

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Backfire, Ping Ping Ping, 1st tank dealer supplied regular 87 unld. Now Premium 92 unld. Runs better but if hot and humid still an ocasional backfire WOT shift @ 5,000 rpm,2-3 or 3-4 :sad: . Cool mornings before warmed up, ping, ping, ping, with ANY hard acceleration. %&#$
 

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To the best of my knowledge ( I work for Ford) the 4.6L 2v does not have a knock sensor (the 4.6 - 4 Valve - Cobra Motor) does...I have run 87 octane - Shell brand gasoline in my Bullitt so far without any problem. I have never had good luck with "Watertown" (Gastown) or BP gas in any of my Ford products over the years....
 

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I stay away from the "10% ethanol" places, but other than that I run 87 in both my Bullitts. I have never heard any pinging and I shift first to fourth all the time? No problems breaking the tires loose from a roll either, when I get on it.
 

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Where do you guys get 93 octane? The highest in CA used to be 92. Now it's 91.

and as far as your car "running like crap" with 87, what's your definition of crap? Does that mean the car shudders and stumbles all the time and vibrates and has a crummy idle?

Personally, if my car is supposed to run on 87, and if it runs like crap on 87, i take it to the dealer and tell them to fix it because something obviously ain't right. With the horrible gas prices, i don't feel like spending an extra 20-30 cents/gallon on premium fuel.
 

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personally '' crap'' means not running as well as I have gotten used to it( on premium....) it will run acceptable on 87 and thats about all.I am not going to go to a dealer for negligible performance if any. If u like the way your car runs on 87 good for you.....
as for me, I do believe the xtra octane and detergents that are in premium help the car run better and I for one can feel it.
 

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>Where do you guys get 93 octane? The highest in CA used to be 92. Now it's 91.<

I can get 94 from Sunoco in Michigan. There is also a station down the street from me that sells 110 Octane race fuel. He lets anyone drive up and pump it into any year car.

Did I mention that we do not have smog testing?
 

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[/quote]
Hmmm. It seems like they are suggesting the lower octane fuel is causing the engine to run hotter. Thats possible I guess. If an engine was running premium as opposed to regular, cylinder heads tempertures would drop, in turn coolant temp would drop.
[/quote]

Actually, that's not possible. Cylinder head temp is affected by several things, but gasoline doesn't "cool" it down. It's more of an indirect relationship. If the heads are hotter than normal operating temp, you may be experiencing detonation (plug fires, chamber ignites before piston hits TDC, forcing it back down) or pre-ignition (plug doesn't fire, chamber ignites because of extreme heat or pressure, usually while piston is on exhaust stroke). By running higher octane, you are decreasing the possibility of either of these two occurences. By doing so, the head temps may lower because they aren't firing more than they are supposed to. That's what octane is & that's what it does. It is not, in & of itself, a power adder (that being said, we're not talking 104 race or aviation gas). If somone sees a significant performance increase by running 92 or 93, they should take the car in for service because it's designed to run on 87 & obviously, somethings not right. Perhaps the computer was retarding the timing or there was major knocking. Also, running a richer gas than the car is designed for can have adverse affects on the catalytic converter, because not all the fuel is being used in the combustion cycle & the cats are getting dirtied by the larger amount of unspent fuel traveling through them. However, as somene else stated, the computer can be reprogrammed to run on a higher octane fuel & it should be if you chose to continually run 92 or 93. But I remind everyone, we have low compression engines designed to run on 87 & if you think yours runs significantly better on 92, you should get it checked by a dealer or mechanic who works on 4.6L 2v motors. Here are two links that give some more info.

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

http://www.osbornauto.com/octane.htm

Hope this helps.
 

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<<<It's more of an indirect relationship. If the heads are hotter than normal operating temp, you may be experiencing detonation (plug fires, chamber ignites before piston hits TDC, forcing it back down) or pre-ignition (plug doesn't fire, chamber ignites because of extreme heat or pressure, usually while piston is on exhaust stroke). By running higher octane, you are decreasing the possibility of either of these two occurences. By doing so, the head temps may lower because they aren't firing more than they are supposed to. That's what octane is & that's what it does. It is not, in & of itself, a power adder (that being said, we're not talking 104 race or aviation gas). If somone sees a significant performance increase by running 92 or 93, they should take the car in for service because it's designed to run on 87 & obviously, somethings not right.>>>

Well, not exactly. Detonation occurs when you get an uncontrolled burn of the charge in the cylinder including 2 flame fronts meeting and hammering the piston. It can raise egt's and therefore cylinder head temperatures. Octane rating of a fuel is essentially it's resistance to ignition.

As for our car's octane needs, specifically, the combustion chamber design, timing curve and initial timing are optimized for 87 octane regular gas. There is power in more timing advance and where you advance it. This will generally require the engine to use a higher octane fuel as the advanced timing starts the ignition sooner and creates the possibility of multiple flame fronts and detonation. If you are experiencing knock on regular gas, then yes, something is out of whack. As our 2V motor does not have knock sensors and if you don't mind the additional cost of a higher octane fuel, you can eliminate the knock and perhaps gain a bit of performance. If not,s ome are getting their computers reflashed which is likely changing the timing advance amount and the advance curve and allowing them to run regular gas.

Where you have an engine with knock sensors, running a higher octane fuel will almost always net a performance increase through more aggressive timing advance/curve, especially with forced induction.

Brian
 
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