S550 Mustang Suspension and Powertrain Discussion

[claudermilk]

Pulling the most pertinent bits from the linked post:

TRANSMISSION:

Q: Tell us a little about the transmission.
A: It’s a Tremec 3160 transmission that’s been modified fairly significantly to cope with the demands of the flat plane crank engine.

Q: What about the fly wheel and the clutch?
A: It’s got a low inertial dual mass flywheel and two 15-mm dual disc clutch.


WHEELS/BRAKES:

Q: Why black wheels?
A: Actually there’s a reason for that. The brake pads we use, they create so much dust and customers just hate it. You drive the car once with clean wheels and they are dirty after a short drive. So that’s why we got dark wheels.

Q: Why no carbon ceramic brakes?
A: I think you’ll find out later that affordability was a big part of this car.

Q: So keeping price down was a big part of that?
A: Yes. That was a priority with this car.

Just saw the car in person yesterday (love it when a plan comes together--hit the show at opening & was one of the first half-dozen to it's stand, so no crowd to fight). I really like the visual changes, this is easily the best looking S550, particularly in the front. While the splitter could use a bit more work to clean up, the widened fenders fix my main gripe--it no longer makes me think of Marty Feldman looking at those headlights.

Finally decent shoes on it: PSS 305 rear, 295 front. The brakes look darn impressive, and the rears are two-piece rotors like the front, just a bit smaller diameter.

 

[Mountain]

An automatic?

According to Nair, during the sixth-generation Mustang’s planning GT350 emerged as the “buzz car” the team wanted to do first. And it just so happened that Ford Powertrain had begun exploring a wild new rev-happy V8 based on the existing Coyote architecture around the same time; the two became the foundation for continuing the Shelby Mustang legacy. (See http://articles.sae.org/13709/.) The “Voodoo” V8 is offered with either a Tremec 3160 six-speed manual or Ford’s own 6R80 six-speed planetary automatic.

Sort of setting up expectations on comparison performance to the Z/28:

Farley’s GT-3-fighter dreams aside, the GT350’s expected competitor will be the Z-28, at its heart a muscle machine aimed at track-day purists and devoid of many typical creature comforts. “Z-28’s a great car, but it’s got a lot of tire underneath it, and its track manners are built around that,” said Nair, himself an accomplished amateur road racer. “We’re less reliant on tire and we’re going to be a little more crisp and nimble. It’s a typical difference in approach between us and GM. I think we’ve coupled that into a better all-around vehicle rather than something that’s so track focused like the Z-28.”

About weight:

According to Jamal Hameedi, Chief Engineer of Ford Global Performance Vehicles, most of the team’s lightweighting measures went into “offsetting all the mass we added in terms of power, driveline, and brakes.” The development budget even included a line for a carbon-fiber grille opening and reinforcement, a lightweight metal strut-tower cross brace, and lightweight functional rear diffuser for improved aero and grip.

While Ford did not announce curb weight (or other key specs, including power and torque ratings) during the car’s L.A. show reveal, Raj Nair earlier told Automotive Engineering that he expected the GT350 will come in “slightly lighter than the current base Mustang GT—3618 lb (1641 kg) with a manual transmission.

About price:

While price has not been announced, Ford insiders indicate the new Shelby Mustang will come in underneath the roughly $74,000 retail figure of the 2014 Z-28. And that’s significantly less than a GT-3 Porsche.

http://articles.sae.org/13712/

 

[NUTCASE]

So they want to talk about the GT-3?

the day they put a 911 turbo motor in a Caymen its lights out for everybody

 

[claudermilk]

Yeah, a Cayman with a 911 engine will be a segment killer.

We’re less reliant on tire and we’re going to be a little more crisp and nimble. It’s a typical difference in approach between us and GM. I think we’ve coupled that into a better all-around vehicle rather than something that’s so track focused like the Z-28.

ZING!

 

[csamsh]

^^^^that right there already sounds like excuses for why the GT350 is slower. booo.

 

[dontlifttoshift]

A little less reliant on tire, 295s vs 305s........I'm assuming he meant we are less reliant on tire compound which could mean with equal 200tw the cars will be very similar.

 

[BMR Tech]

Linear Rates

165lb/in Front
728lb/in Rear

Just sharing some Performance Pack spring rates.

 

[kcbrown]

Linear Rates

165lb/in Front
728lb/in Rear

Just sharing some Performance Pack spring rates.

728 lb/in rear?

What kind of motion ratio is back there anyway???

 

[Norm Peterson]

Judging from this picture, 0.5-ish or quite possibly a bit less. Didn't bother measuring. From Mustang6g.com.

Norm

 

[Budwise]

Is that good or bad? Can someone explain?

 

[BMR Tech]

.492

 

[BMR Tech]

For the coilover I am testing, it is .774

 

[Norm Peterson]

Is that good or bad? Can someone explain?

Mostly, it's just something that . . . is. If you can't reasonably fit the spring anywhere else you put it there and select a stiffness that gives you the wheel rate you were looking for. Or something like that.


Norm

 

[NUTCASE]

Hmmm, how to do this without going into complicated science stuff


look at your lower control arm bushing on the body, then look where the center line of the wheel is. Lets say this is 20 inches. lets say you do your math and decide you need 300lb of force from a spring effective over the wheel. lets say your like yeah cool, get a 300lb spring and put it on your spring perch that is 10 inches from the bushing at the body. your effective spring rate at the wheel will actually be 150lb at the wheel becuase your 300lb force spring is halfway inbetween the wheel and the body and not directly over the wheel. so if your spring perch is halfway between the wheel center line and the bushing, and you need 300lb force over the wheel centerline, you actually need to get a 600lb spring.

B=bushing S=spring force W=wheel force D1=distance spring from bushing D2=distance wheel from bushing

S(D1)=W(D2)

then D1/D2 will equal the number you are talking about and will give a quick reference when deciding spring rates.

this is also in a perfect world where the control arm lies completely flat when the car is on the ground. The math gets more complicated then that. Also I have not accounted for compressed height.

If somebody can tell me I am wrong go for it, I am not accustom to any industry standards I just know a bunch of math and physics and shit.

 

[dontlifttoshift]

I'm just a guy that welds stuff but I don't think wheel centerline has anything to do with motion ratio. Ball joint centerline sounds right to me. Norm will have the answer shortly.

 

[NUTCASE]

by center line I meant a line that cuts down the middle of the tread if you were to view the tire from the back of the car.

I know suspension parts make all sorts of crazy angles and hub spacing and all that, but transmissability of force would still apply. and like I said I was assuming the control arm stayed perfectly level so I could explain without writing a book.

still waiting myself for somebody in the industry to chime in.

 

[Norm Peterson]

Wheel centerline location actually is involved, just that it's only a small effect.

The overall motion ratio that gets you from wheel travel to spring compression has several components. The obvious one is the ratio that you calculate based on the spring's location on its control arm and the distance between the chassis side pivot axis and the ball joint. I'll use the term 'loaded ball joint' just for clarity, since multilink and SLA suspensions also have "follower ball joints" that you don't need to compute the motion for here. Another one is the angle that the spring makes with the vertical (it's a cosine function).

And there's a third little piece, involving the distance from the front view instant center to the loaded ball joint and the distance from that FVIC and the wheel center. Remember that since the upright/steering knuckle/"spindle" is rotating in a lazy arc about the FVIC (and that the wheel is bolted to it), that the motion at the wheel does not have to be identical to the motion at the loaded ball joint. Of note - this ratio is frequently greater than 1. I'll try to put together a couple of sketches, probably tomorrow.

In most cases the wheel centerline matter is only a very small correction, and can probably be ignored without consequence. 1.05 would be a pretty high value (and would imply an unusually large scrub radius).


Norm

 

[Whiskey11]

728 lb/in rear?

What kind of motion ratio is back there anyway???

Sounds quite ridiculous until you consider that the wheel rate is going to be just shy of a quarter that rate. Your actual wheel rate from springs is only 176 lbs/in in the stock location...

Coilovers at the rear of this car are going to be a nice improvement in the ride category. Quite surprised we haven't seen issues with head toss in this chassis but then I remember we are also talking about a significant number less in the unsprung weight category.

 

[Budwise]

My head just exploded.

 

[Department Of Boost]

You guys think those motion ratio's are crazy. How about running a 650# spring on a 375# motorcycle?