Top speed for '21 Powerboost

[Diligenthunter]

Consider the rotating crankshaft or the rotating valve trains... consider the chain drives inside the engine. The RPMs go from around 1300 up to over 5000 and they are higher RPM than the transmission or driveline. Balancing various components and balancing between them makes a difference. And keep in mind that damage from rotational vibration is not a linear increase, it's a square function. But in the end, I think that Ford is just minimizing cost when they specify certain elements of these components to be within a given tolerance.

I would certainly agree that higher rpm increases rotational vibration and thus more damaging to an engine.

My question is how that relates to top speed and engine balance. Are we saying that holding the engine at 5k rpm in 1st is more, less or the same wear as 5k rpm in 5th? And the effect of that wear could be reduced by better engine balancing? Wouldn’t your transmission/driveline balance play a bigger role?

Appreciate the discussion.

Sponsored

 

[Gros Ventre]

I would certainly agree that higher rpm increases rotational vibration and thus more damaging to an engine.

My question is how that relates to top speed and engine balance. Are we saying that holding the engine at 5k rpm in 1st is more, less or the same wear as 5k rpm in 5th? And the effect of that wear could be reduced by better engine balancing? Wouldn’t your transmission/driveline balance play a bigger role?

Appreciate the discussion.

Remember the driveline is at a lower RPM below 7th. Is there more damage in, say, 2nd gear? Well consider the cylinder pressures. They'll all be lower in 2nd than in say 10th at max RPM. Thus the force on the piston and connecting rod, and therefore the forces put on the crankshaft, will be lower in lower gears. Given the close ratios between 7-8-9 &10 I suspect the forces are nearly the same at max RPM in those gears But keep in mind you're talking of max RPM and likely max boost at top speed, I doubt at max RPM in lower gears you'll be at max boost (unless you're climbing a 45º hillside).

 

[HammaMan]

5K was just a random value I threw out.

My question was the relationship between “engine balance” and top speed. Traction equal is there a difference to the engine being at redline in 2nd gear vs say 5th that would be effected by how “balanced” the engine is. Per Gros Ventre’s post.

Top speed and engine balance? Makes no sense. Where does the truck put RPMs in tow/haul? Ford uses the 3.5 in the GT as well. The amount of dev that's gone into this motor has it operating as good as it could be barring some new tech that comes about.

 

[Diligenthunter]

Top speed and engine balance? Makes no sense. Where does the truck put RPMs in tow/haul? Ford uses the 3.5 in the GT as well. The amount of dev that's gone into this motor has it operating as good as it could be barring some new tech that comes about.

Please read Gros’s post that I was quoting.

Remember the driveline is at a lower RPM below 7th. Is there more damage in, say, 2nd gear? Well consider the cylinder pressures. They'll all be lower in 2nd than in say 10th at max RPM. Thus the force on the piston and connecting rod, and therefore the forces put on the crankshaft, will be lower in lower gears. Given the close ratios between 7-8-9 &10 I suspect the forces are nearly the same at max RPM in those gears But keep in mind you're talking of max RPM and likely max boost at top speed, I doubt at max RPM in lower gears you'll be at max boost (unless you're climbing a 45º hillside).

Yup definitely didn’t think about cylinder pressure, I have reading to do tonight.

Agreed for max speed runs at sustained high rpm under full boost.

I would think a relatively quick pull to 120 should be okay vs a hard run to whatever these trucks actually top out at 150 plus?

Thank you for the learning Gros!

 

[Gros Ventre]

Another thought... If you look at racing engines, they go up to 10,000 and higher RPM. in order to reach that they finely balance things along with using alcohol and other exotic fuels because of the higher octane ratings. Also keep in mind that internal friction is going up, up , & up at these higher RPMs. The reason about 1500 to 1800 RPMs is targeted by the gear ratios at normal highway speeds, is that is the minimum point for fuel consumption... And the whole reason for a 10 speed is to drop fuel consumption for the advertised EPA MPG wars.

 

[HammaMan]

Please read Gros’s post that I was quoting.



Yup definitely didn’t think about cylinder pressure, I have reading to do tonight.

Agreed for max speed runs at sustained high rpm under full boost.

I would think a relatively quick pull to 120 should be okay vs a hard run to whatever these trucks actually top out at 150 plus?

Thank you for the learning Gros!

I did, but lend very little credibility to his opinion/s

 

[Tank]

Yeah I need to find my Dragy.

Dyno tune from them or just remote data logged?

Okay so that’s just a cat back exhaust right?

I've just been remote datalogging..

 

[Chili]

There is a real issue with driveshaft speed, especially with 3.73 gears and 32" or smaller tires. They will and have come apart before the tires will. I suspect that's the reason my truck won't do the 112 or so the tires are rated at.

 

[JJSnell]

I had a big ol Expedition pull up along side me and started 'jumping' his throttle... I floored it and left him dusted but as we were neck and neck at the biggining I could here his turbos whine like a jet airplane. I was waiting for him to scream passed me, didnt happen. Last I saw was 103mph and started slowing down....

 

[Gros Ventre]

Here's a discussion. Consider #1... I hadn't thought of a cam shaft destroying itself when over-revving... But that goes into the design of the engine and how much Ford is willing to pay for the metallurgy of the camshaft design...

Sponsored