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John B

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I'm not gonna get sucked into the back and forth, but having boosted experience with superchargers, not turbos, I found and copied a post that does a great job of describing the issues. Fwiw I'm a fan of using high octane with 10% ethanol, since it does a great job of suppressing detonation. The short version, with modern turbos, you don't need to go higher or lower with octane. Of course, I'm always open to a scholarly discussion of this concern.
What model year Tundra are you driving?

If it is a 2022 model it will have turbochargers on it. The turbochargers don’t care what altitude you are at, if there is enough air available to produce positive intake manifold pressure once the turbine side (hot side) of that turbo spins fast enough then your altitude is meaningless. The turbochargers effectively compensate for or eliminate altitude as a limit on power output.

Your naturally aspirated engines running at 3,000ft above sea level or higher will be OK on 85 Octane assuming they’re designed to run on 87 Octane at sea level. They’re not sucking in air at 14.7lbs/sq-in like they would be at sea level; at 3,000ft atmospheric air pressure is nominally 13.2lbs/sq-in, and it continues to drop the higher you go. For example TFL Truck starts their Ike Gaunlet testing high enough air pressure is just above 10PSI and ends just below 10PSI.

A turbocharger capable of positive manifold pressure will not be safe using a lower grade of fuel. The engine will be using air at a higher pressure than sea level all the time under boost regardless of altitudes an internal combustion engine is capable of running at. Most modern turbocharged engines can make more boost than they are tuned to use and bleed off the excess capacity via the wastegate to prevent over boost. As the altitude get higher and the ambient air pressure reduces the wastegate has more than enough range to compensate by not bleeding off as much pressure. So the system still makes full boost most of the time. If the turbo engine is tuned to make 15lbs/sq-in of boost at sea level, it’s going to very likely make it at 10,000ft too by spinning a bit faster and not opening the wastegate as much or at all. So if the truck calls for 87 Octane feed it 87 Octane at a minimum.
Edited to add that overall the power at higher altitudes will go down since turbo boost level controls most likely measure boost based on psig over atmospheric psig which goes down as you go up. This is an engineers "simple" way of saying the higher you go, the less air/fuel is actually going into the engine..... grinning
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RRaptor 405

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I would never use lower than 91 if tuned no matter how much time retards it can make a nice hole in a piston if detonates
 

Arsenall11

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So, if you are going to the extent of tuning, wouldn’t you automatically go to a higher grade for performance in general?
 

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I'm not gonna get sucked into the back and forth, but having boosted experience with superchargers, not turbos, I found and copied a post that does a great job of describing the issues. Fwiw I'm a fan of using high octane with 10% ethanol, since it does a great job of suppressing detonation. The short version, with modern turbos, you don't need to go higher or lower with octane. Of course, I'm always open to a scholarly discussion of this concern.


Edited to add that overall the power at higher altitudes will go down since turbo boost level controls most likely measure boost based on psig over atmospheric psig which goes down as you go up. This is an engineers "simple" way of saying the higher you go, the less air/fuel is actually going into the engine..... grinning
Boost is Absolute measured at the manifold as in Manifold Absolute Pressure MAP sensor. Fuel is added based on the MAP and desired Lambda. The turbo compensates for thinner atmospheric pressures which is why turbo work great at high altitudes.

So, if you are going to the extent of tuning, wouldn’t you automatically go to a higher grade for performance in general?
Definitely I do and will. My comments were regarding the notion that our sophisticated engines could not compensate for lower octane in fuel if there was no other choice.
 

Chassis N2531

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Interesting convo about octane, turbos and altitude. Aren't jet engines essentially gas turbines? Basically a fan to suck in air, compress it, mix it with fuel, ignite it, and then shoot it out the back to create thrust? Without all the EPA hanging off the exhaust... How high do jets fly and what octane is jet fuel?
 

Deleted member 9086

Interesting convo about octane, turbos and altitude. Aren't jet engines essentially gas turbines? Basically a fan to suck in air, compress it, mix it with fuel, ignite it, and then shoot it out the back to create thrust? Without all the EPA hanging off the exhaust... How high do jets fly and what octane is jet fuel?
First off, your description of how a jet engine operates is incorrect. You’re attempting relate the operation of a turbocharger to a jet engine. Very simply doesn’t work the same way.

Jet engines don’t work off the same principles of ICE’s, nor can their operation be described as such. Their fuel requirements are completely different. Jet engines run on a highly refined form Kerosene jet fuel. In There is no crossover between octane ratings for gasoline and Kerosene.

  • Jet A: This is the most commonly used jet fuel, known for its excellent energy density and affordability. It has a relatively low octane rating, typically around 15-20, which makes it suitable for commercial airlines and general aviation. Jet A provides efficient combustion and stable performance for most aircraft.

  • Jet A-1: Similar to Jet A, Jet A-1 is a widely used jet fuel with a slightly higher freeze point. It maintains excellent performance in colder climates, making it the fuel of choice for airlines operating in colder regions. Jet A-1 also has a lower octane rating, typically around 15-20

  • JP-4: Developed specifically for military aircraft, JP-4 possesses a higher octane rating of around 25-30. This higher rating allows military aircraft to operate at higher altitudes and speeds, maximizing their performance capabilities. However, JP-4 is not commonly used in commercial aviation due to its lower flash point and potentially hazardous properties.

  • JP-8: Another jet fuel used by the military, JP-8 offers similar benefits to JP-4 in terms of higher octane rating, allowing for enhanced performance. JP-8 also possesses better storage stability and compatibility with aircraft systems, making it the preferable choice for military operations.
Bottomline; the higher jet-fuel octane rating, relates directly to maximum performance and higher altitude operation.

Gasoline is rated on flash point alone to prevent knock. Jet fuel is graded based on its higher flash point, density, and freeze point to ensure safe and efficient operation in aircraft engines at extremely high altitudes.

Literally, jet-fuel has a much higher flash point than automotive combustible fuel. Where fumes from automotive fuel will ignite with a match, JP fuel will actually smother or extinguish open flame, in direct proportional amounts.

Additionally, it’s important to understand, the octane rating used to measure the performance of gasoline, is not applicable to jet fuel.

I’m not going to get into; jet engine vs ICE comparisons, as their construction and operation are vastly different.??
 
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Chassis N2531

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First off, your description of how a jet engine operates is incorrect. You’re attempting relate the operation of a turbocharger to a jet engine. doesn’t work.

Jet engines don’t work of the same principles of ICE’s, nor can their operation be described as such. Their fuel requirements are completely different. Jet engines run on a highly refined form Kerosene jet fuel. In There is no crossover between octane ratings for gasoline and Kerosene.

  • Jet A: This is the most commonly used jet fuel, known for its excellent energy density and affordability. It has a relatively low octane rating, typically around 15-20, which makes it suitable for commercial airlines and general aviation. Jet A provides efficient combustion and stable performance for most aircraft.

  • Jet A-1: Similar to Jet A, Jet A-1 is a widely used jet fuel with a slightly higher freeze point. It maintains excellent performance in colder climates, making it the fuel of choice for airlines operating in colder regions. Jet A-1 also has a lower octane rating, typically around 15-20

  • JP-4: Developed specifically for military aircraft, JP-4 possesses a higher octane rating of around 25-30. This higher rating allows military aircraft to operate at higher altitudes and speeds, maximizing their performance capabilities. However, JP-4 is not commonly used in commercial aviation due to its lower flash point and potentially hazardous properties.

  • JP-8: Another jet fuel used by the military, JP-8 offers similar benefits to JP-4 in terms of higher octane rating, allowing for enhanced performance. JP-8 also possesses better storage stability and compatibility with aircraft systems, making it the preferable choice for military operations.
Bottomline; the higher jet-fuel octane rating, relates directly to maximum performance and higher altitude operation.

Gasoline is rated on flash point alone to prevent knock. Jet fuel is graded based on its flash point, density, and freeze point to ensure safe and efficient operation in aircraft engines at extremely high altitudes.

Additionally, It is important to understand, the octane rating used to measure the performance of gasoline, is not applicable to jet fuel.

I’m not going to get into; jet engine vs ICE comparisons as the differences of construction and operation are vastly different.??
Thanks for the detailed explanation. I'll just stick to 93 octane in my 500 and RR at any elevation and call it good.

Jeff
 

Deleted member 9086

Thanks for the detailed explanation. I'll just stick to 93 octane in my 500 and RR at any elevation and call it good.

Jeff
Good call.
This is a good read and explanation of Air Density, which is directly affected by altitude and relates to overall hp production.;

https://www.garrettmotion.com/news/...at-elevation-counteracting-lower-air-density/

If you decide to use a lower octane fuel at altitudes above 5000 vertical feet, will reduce the overall combustion and resulting in reduced engine output and performance.???
 
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The tune is now showing as having a CARB number for use in CA (for the ’24 RR).

Question to those that have it, many here are saying the changed trans shifting makes for big changes, holding gears longer etc. This is exactly what sport mode does. So are sport and normal now very close to each other (at least as far as engine/trans feel)? I like that sport is available but also like how much more “civilian” normal feels when you just want to drive calm.

Also, a question on the warranty component: does the installation of this VOID your original factory warranty, and you have to have Ford (or a certified installer) install it and then Ford Performance gives you a NEW and separate 3/36 warranty? What about extended warranties purchased with the truck?
 
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CapH

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H
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Thanks for the heads up. Anyone know where we can get it for the best price?
 

Blue_Raptor

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Thanks for the heads up. Anyone know where we can get it for the best price?
Well....just be aware there are possible warranty implications.

I was chatting with someone from Ford Performance asking about the warranty. They initially said the tune will not void the original factory warranty, but did not know about extended warranty plans (said to check with dealer and/or warranty holder). I specifically asked if I install the tune myself, will that void the original factory warranty. He said he didn't know.

So, having said that, I have seen other threads (not just for the RR) that people got the tuner & tune from a lower cost source online, and their local dealer either was not stoked on installing it or would not do it because they did not purchase the tune+tuner from them.

Seems very petty I know. But check into this first before making your purchase.

But, places like Livernois have it listed for a decent amount less than direct through Ford Performance

https://www.livernoismotorsports.co...Qe5zFZwjFkixHwJ2cjeY4jRu6fpogb_VJOsFeD8&gQT=2
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