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Old 10-30-2013, 08:40 AM   #43
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Again, you do not understand how octane affects MPG. It does not unless you are running at WOT the entire tank. Most people run the speed limit of 65-70 MPG. Under these conditions there is little to no boost. So what this means is there is not high combustion chamber pressures that require higher octane fuel.

For instance, this truck ran in the high 12s. Higher than normal boost levels and torque. But on road trips I would use 87 octane fuel because it made no difference in MPG and the combustion pressures were similar to a stock 5.4L engine. Highway was 18.5 MPG. And yes, I was used as a tow vehicle.
I agree 100%. I can stay off boost up to about 68mph in my car with good aerodynamics. Unfortunately, our speed limit is between 65 and 75, so if you're not going 80mph, you get run over.
I suspect a current F150 is less able to stay off boost at highway speed just from wind resistance.

As to WOT, I just don't agree in the context of these small turbos. They spool up early by design without WOT, and when you're towing, even more so. Peak torque is down around 2,000rpm on my car. You don't need WOT to hit full boost. It can put out the same 12psi under load at 2,500rpm as at redline. Once you hit that 12psi at any throttle position, going to WOT does not create more boost.

Now for me, I run diesel all the time in this. 627lb-ft at the wheels (with AWD). 25mpg combined longterm average. 16mpg towing my 26'TT.
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Old 10-30-2013, 08:49 AM   #44
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I agree 100%. I can stay off boost up to about 68mph in my car with good aerodynamics. Unfortunately, our speed limit is between 65 and 75, so if you're not going 80mph, you get run over.
I suspect a current F150 is less able to stay off boost at highway speed just from wind resistance.

As to WOT, I just don't agree in the context of these small turbos. They spool up early by design without WOT, and when you're towing, even more so. Peak torque is down around 2,000rpm on my car. You don't need WOT to hit full boost. It can put out the same 12psi under load at 2,500rpm as at redline. Once you hit that 12psi at any throttle position, going to WOT does not create more boost.

Now for me, I run diesel all the time in this. 627lb-ft at the wheels (with AWD). 25mpg combined longterm average. 16mpg towing my 26'TT.
You have to think about what your saying. I agree that these turbos are cabable of full boost under lower RPMs but what you are saying is at 1/2 throttle these trucks are making 420 torque. That is just not so. That should be limited to when it is demanded at or close to WOT. Under medium throttle accelerations, boost is about 1/2 what max is. And yes I have monitored and recorded this information.
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Old 10-30-2013, 09:45 AM   #45
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You have to think about what your saying. I agree that these turbos are cabable of full boost under lower RPMs but what you are saying is at 1/2 throttle these trucks are making 420 torque. That is just not so. That should be limited to when it is demanded at or close to WOT. Under medium throttle accelerations, boost is about 1/2 what max is. And yes I have monitored and recorded this information.
Sorry, not everything that was in my head made it to the keyboard.

I was not thinking of specific power output, but pressure inside the cylinder where the gas is introduced. Gas turbo engines usually run fairly "low" compression ratios at the bench when you do a compression test without boost. But once running and the boost comes up, the actual operating pressure inside the combustion chamber does too. So at any throttle position with boost, you will run into a detonation issue if that operating pressure (combined with heat) is significant enough with low octane.

It just seems like most buyers of something like a gas turbo will likely put the hammer down every now and then during every tank of gas. And back to towing with a F150 ecoboost, you will be running on constant boost a significant part of the time so having sufficient octane seems important to both performance and health of the engine.
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Old 10-30-2013, 10:27 AM   #46
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Sorry, not everything that was in my head made it to the keyboard.

I was not thinking of specific power output, but pressure inside the cylinder where the gas is introduced. Gas turbo engines usually run fairly "low" compression ratios at the bench when you do a compression test without boost. But once running and the boost comes up, the actual operating pressure inside the combustion chamber does too. So at any throttle position with boost, you will run into a detonation issue if that operating pressure (combined with heat) is significant enough with low octane.

It just seems like most buyers of something like a gas turbo will likely put the hammer down every now and then during every tank of gas. And back to towing with a F150 ecoboost, you will be running on constant boost a significant part of the time so having sufficient octane seems important to both performance and health of the engine.
Believe me, I know the keyboard brain fart. I also assumed that the 3.5 ecoboost was a low compression ratio engine. But the specs for it is 10:1. fairly high by any gas boosted standards.
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Old 10-30-2013, 12:06 PM   #47
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Again, you do not understand how octane affects MPG. It does not unless you are running at WOT the entire tank. Most people run the speed limit of 65-70 MPG. Under these conditions there is little to no boost. So what this means is there is not high combustion chamber pressures that require higher octane fuel.

For instance, this truck ran in the high 12s. Higher than normal boost levels and torque. But on road trips I would use 87 octane fuel because it made no difference in MPG and the combustion pressures were similar to a stock 5.4L engine. Highway was 18.5 MPG. And yes, I was used as a tow vehicle.
If that's a SVT Lightning, you obviously know it's a supercharged 5.4l at 8lbs stock and requires premium fuel. Can't run 87 or you will get detonation, unless you have some kind of custom tune that bypasses the supercharger alltogether. If you have a stock tune and tow, running 87, I'd think you would boom boom the engine in very short order.
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Old 10-30-2013, 12:16 PM   #48
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Per my butt-o-meter, my 2912 F-150 EcoBoost doesn't seem to run any better on premium than it does on regular unleaded. But it gets about 1.5 to 2 MPG better burning 91 octane premium when dragging a 4,870-pound TT at 65 MPH between Midland and Austin, including the Hill Country between Brady and Austin. The improved MPG is just about enough difference to break even on the price of premium over regular. So I pay the extra for premium when towing on that trip, or any trip with hills or steep grades, such as crossing the remnants of the Rockies between Midland and El Paso. But going east on I-20, I-30 and I-40 from Midland to Memphis, I just run regular (87 octane here at 2,500 ft. altitude).
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Old 10-30-2013, 12:28 PM   #49
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I said in the other thread so here is my take on it in this one. The big three will NOT do diesels right in the half tons. (Fords not doing it at all i think)This is history repeating its self for GM, if you folks remember GM did this back in 1977-80 with the 5.7L Olds diesel (somewhat a converted design) and if i recall correctly there wasn't a tow rating because it was for MPG, not work.
And we see how well that worked out now didn't it!!
Had one. MPG out the wazoo. MN to NY loaded 22 mpg. HP was 150 and forget torque, if there was a coating of snow it would turn the rear wheels just putting it in drive. Loved the way it ran, starting it...... I burnt out at least 3 battery cables, had to cycle the glow plugs many times, had to add a booster, at times, with 200 amp start along with the 1600 amps of battery..... HATED starting it.
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Old 10-30-2013, 01:13 PM   #50
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If that's a SVT Lightning, you obviously know it's a supercharged 5.4l at 8lbs stock and requires premium fuel. Can't run 87 or you will get detonation, unless you have some kind of custom tune that bypasses the supercharger alltogether. If you have a stock tune and tow, running 87, I'd think you would boom boom the engine in very short order.
It helps if you read the part where I would run 87 on road trips. This was only highway driving. At 70MPH the intake was still under a negative atmospheric pressure so no boost. I did do a custom tune on it because of running a max of 18 PSI. Under highway driving is was just a lower than a normal compression N/A 5.4L. Under racing conditions it was ran on 91+ octane.

Since it is supercharged, there is no tune in the world that would by pass the supercharger. The supercharger is belt driven with only a blow off valve. Boost is controlled via the right foot. More foot pressure, more on the fun gauge.
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Old 10-30-2013, 01:29 PM   #51
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These were three runs with a brand new ecoboost f150. It is a supercrew (4 door), 4x4, with 3:31 gears. Higher engine load under accel. The first run shows about 5 PSI of max boost under this accel. 1/2 throttle shows about 10 psi. Wot throttle shows a max of 14.5 psi. However this truck is brand new so there has not been a completed drive cycle so the adaptives have not completed. If you look closely, the throttle body (etc dsd) is ever changing to find the correct boost level. The air/fuel ratios are also slightly off. During the first run at wot it was at 9.5:1. Way to rich. It was adjusting to around 11 and some change. It should settle in at that area under WOT throttle though because it is turbocharged.
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Old 10-30-2013, 01:34 PM   #52
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I did forget to check map pressure when driving at 70 mph. I did check around 50 mph and it was showing about 1 lb of boost. I suspect it would be a few lbs more than that at 70 but that is just speculation until I get a chance to actually check.
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