Blown away by ICE GT Fastback

[Jimrpa]

Basic Physics....You're not operating in a vacuum. As you push more against the air it pushes back and it needs more and more power to accelerate at the same rate, which it doesn't have because the power is flat.

But it's also not flat. As you gain in speed, the amount of power available drops for thermal control and battery health. Additionally, the longer you accelerate the more power is pulled for the same reasons.



They changed the rear motor to the one used in the lightning and gave an available performance upgrade package for purchase which boosts power and reduced the power throttling which gave a significant decrease in both 0-60, 1/4 mile times and an increase in trap speed from 102 to 115 mph.

Thanks all! I had no idea that aerodynamic drag was THAT large of a factor between 60 MPH and ~ 120 MPH. I did consider thermal effects on drivetrain components and assumed that, at least until around ~120 MPH, the thermal management systems kept those relatively constant (for example, the battery would deliver the same energy to the motors, regardless of speed, at least until 120 MPH).

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[GreaseMonkey]

I’m not familiar with the specific engineering trade offs that Ford was wrestling with in their calculations, but I’m suspect they were balancing some component and assembly costs vs performance specifications vs customer expectations triangle, and I’d say they got it about right for me. I likely wouldn’t have paid $20k more if the car had a 175mph top speed and a 10sec quarter mile, because I’d never get to use those features. I *do* get a smile every time I launch from a green light, tho. And regardless of whether that fun lasts 5 seconds or 10 seconds, I wouldn’t know because I’ve already eased up off the throttle after 3-4. I don’t mind the occasional ticket (though it’s been years), but I don’t want to go to jail! ;-)

Exactly. At 36 mph, I’m getting a ticket mailed to my home. It takes me less than 1.5 sec to get to 30+ mph. That, however, didn’t stop me from buying summer Pirellis and am still planing to buy the $1,000 perf upgrade. So $2,500 extra to never experience the performance I’d be getting. Just simply having the bragging rights of a fast car. I’m blaming it on a midlife crisis. Can be way worse, I guess.

 

[gregsfortytwo]

Thanks all! I had no idea that aerodynamic drag was THAT large of a factor between 60 MPH and ~ 120 MPH. I did consider thermal effects on drivetrain components and assumed that, at least until around ~120 MPH, the thermal management systems kept those relatively constant (for example, the battery would deliver the same energy to the motors, regardless of speed, at least until 120 MPH).

Aerodynamic drag goes up with the square of velocity, regardless of velocity. So even at 80mph you’re using 51% more power than at 65mph.
This is DEFINITELY visible in your freeway range, so you’ll see people complaining they only get 2mi/KW right next to people loving their 3.5mi/KW that the car is about rated for.

 

[Mach1E]

Thanks all! I had no idea that aerodynamic drag was THAT large of a factor between 60 MPH and ~ 120 MPH. I did consider thermal effects on drivetrain components and assumed that, at least until around ~120 MPH, the thermal management systems kept those relatively constant (for example, the battery would deliver the same energy to the motors, regardless of speed, at least until 120 MPH).

The power of the air at 120 mph is very significant.

So significant it helps a 735,000 lb airplane take off at that speed!

But it isn’t just wind resistance, rolling resistance and all the moving parts resistance go up (also mass x velocity squared).

So even in a vacuum your car would be slower from 60 to 120 than 0-60.

 

[Mach1E]

To avoid humiliating defeats like this, the Porsche Taycan\Audi GT platform has that two-speed gearbox that shifts at around 45mph ;-)

Isn’t that two speed more about efficiency and top speed than higher speed acceleration?

For this rolling race (which would be in 2nd gear for the Porsche/Audi) I don’t think it wouldn’t really help.

 

[Graction]

I had a 22 GT non performance. Now I have a 24 GT with performance package. The other day I was going 50 and floored it to 90 expecting much better acceleration than my 22, but I was….underwhelmed. Really didn’t seem much different than my previous GT. Now I didn’t time it but still thought it would feel much quicker.

 

[Ahlarict]

Isn’t that two speed more about efficiency and top speed than higher speed acceleration?

For this rolling race (which would be in 2nd gear for the Porsche/Audi) I don’t think it wouldn’t really help.

Good question - It's just a piece of unsourced trivia that stuck in my head after watching too many reviewers on YouTube talking about the Audi GT when I was considering going that route. Here's what the likeliest among Bing's top search results has to say about it:

• Why the Porsche Taycan EV's Two-Speed Transmission Is a Big Deal
• Porsche Taycan Turbo S Two-Speed Transmission Explained
• Porsche Taycan 2-Speed Rear Transaxle: Performance Modeled

TLDR: It says it accomplishes both higher acceleration and higher efficiency because it has two widely spaced ratios instead of one do-it-all compromise ratio. Performance and\or efficiency benefits are observed throughout the speed range (depending on how hard your foot is pressing the go-button).

 

[pikepilot]

When I was on the way home with my Rally, I got behind a trUck/trailer and had to crawl @ 45mph for a bit. I noticed a GT right behind me. When we got to the passing lane section, I put it down (whisper mode). In about 2 (3?) seconds I hit 100 and backed off. Yoiks!

Eventually the GT caught up and I let it pass me. I knew I was heading to speed trap territory.

According to my research, the MME Rally does 0-60 in 3.4 and the Stang GT can do it in 3.9 (10spd auto).

This is probably a dumb question, but why put it into whisper mode in this scenario?

 

[GreaseMonkey]

This is probably a dumb question, but why put it into whisper mode in this scenario?

They didn’t change mode. That’s the mode they were in. They just kicked the go pedal down.

 

[Mach1E]

Good question - It's just a piece of unsourced trivia that stuck in my head after watching too many reviewers on YouTube talking about the Audi GT when I was considering going that route. Here's what the likeliest among Bing's top search results has to say about it:

• Why the Porsche Taycan EV's Two-Speed Transmission Is a Big Deal
• Porsche Taycan Turbo S Two-Speed Transmission Explained
• Porsche Taycan 2-Speed Rear Transaxle: Performance Modeled

TLDR: It says it accomplishes both higher acceleration and higher efficiency because it has two widely spaced ratios instead of one do-it-all compromise ratio. Performance and\or efficiency benefits are observed throughout the speed range (depending on how hard your foot is pressing the go-button).

Yes, but the “higher acceleration” would be in first gear.

Wouldn’t help for this rolling race. I would bet the added weight and much higher gear would actually make it slower in 2nd gear vs one “do it all” gear.

The compromise is weight and cost. Considering that our torque heavy GTs already spin the tires at lower speeds and a higher top speed isn’t really the goal, I’m glad we don’t have a 2 speed transmission. I don’t think we would like the price tag to go with it.

 

[Jimrpa]

Aerodynamic drag goes up with the square of velocity, regardless of velocity. So even at 80mph you’re using 51% more power than at 65mph.
This is DEFINITELY visible in your freeway range, so you’ll see people complaining they only get 2mi/KW right next to people loving their 3.5mi/KW that the car is about rated for.

I understand the range impact. What I still have problems wrapping my head round the the significant reduction. In acceleration as speed increases.

 

[Jimrpa]

The power of the air at 120 mph is very significant.

So significant it helps a 735,000 lb airplane take off at that speed!

But it isn’t just wind resistance, rolling resistance and all the moving parts resistance go up (also mass x velocity squared).

So even in a vacuum your car would be slower from 60 to 120 than 0-60.

Thanks! But the moving parts resistance should be significantly less, simply because there are fewer moving parts (the rotor in the motor, the reduction gearing, and whatever gearing is necessary to get to the wheels). There aren’t the thousands of bits and pieces flying around that there are in an ICE?

 

[MacherAWD]

Thanks! But the moving parts resistance should be significantly less, simply because there are fewer moving parts (the rotor in the motor, the reduction gearing, and whatever gearing is necessary to get to the wheels). There aren’t the thousands of bits and pieces flying around that there are in an ICE?

Is it the Torque curve? The mach-e gets it power from torque which appears to start falling after 3500 rpms. So we have lots of power low end, but that falls off at speed, vs a higher reving HP engine.

 

[Jimrpa]

Is it the Torque curve? The mach-e gets it power from torque which appears to start falling after 3500 rpms. So we have lots of power low end, but that falls off at speed, vs a higher reving HP engine.

Ah! I’ll bet that’s also a lot of it. I’ve been assuming torque would be pretty constant across the operating range (like most electric motors). If it has a drop off, that, coupled with all the other losses in the system, answers my question.
Of course, now I’ll be pushing for a flatter torque curve across a wider operating range, along with restoring my beloved frunk ???

 

[Ahlarict]

Yes, but the “higher acceleration” would be in first gear.

Wouldn’t help for this rolling race. I would bet the added weight and much higher gear would actually make it slower in 2nd gear vs one “do it all” gear.

The compromise is weight and cost. Considering that our torque heavy GTs already spin the tires at lower speeds and a higher top speed isn’t really the goal, I’m glad we don’t have a 2 speed transmission. I don’t think we would like the price tag to go with it.

That third "Performance Modeling" link indicates more torque at every speed, and enough more to offset the additional weight of the transmission - At least that's the theory. But, you don't need to worry about Ford even offering us the choice any time soon.

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