S550 Mustang Suspension and Powertrain Discussion

[Grimace427]

I believe only the rear track is wider, from everything I've read so far.

S197 track 62.3F/62.9R, S550 track 62.3F/64.9R.

When they designed the new 5.0, they left provisions for an easy conversion over to Direct Injection.

That was a false assumption by a few magazine editors when they saw a little bump in the combustion chamber. When you look at the top side of the head you see there is actually no room for a DI piezo injector. The heads would need to be completely redesigned for DI still.

 

[sheizasosay]

S197 track 62.3F/62.9R, S550 track 62.3F/64.9R.





That was a false assumption by a few magazine editors when they saw a little bump in the combustion chamber. When you look at the top side of the head you see there is actually no room for a DI piezo injector. The heads would need to be completely redesigned for DI still.

Yeah that magazine that debuted the Coyote (5.0 mag I believe) was my info source.

 

[sheizasosay]

Yeah, and if you believe otherwise maybe you should read up on the 5.4/5.8L in NA configuration.

Can you reference your source?

 

[Grimace427]

Yeah that magazine that debuted the Coyote (5.0 mag I believe) was my info source.

Not to say it won't happen, but as the Coyote sits now it will require some redesign. Some of those magazine guys assumed the Coyote would get DI back in 2011.

 

[Norm Peterson]

I stumbled across this thread only a few minutes ago . . . haven't read it all yet.

Does this solid axle Mustang look like it is going into positive camber on the outside rear tire, in this image?

I'm absolutely certain that you're getting a little positive rear camber . . . not due to suspension geometry of course, but due to lateral load transfer and tire vertical stiffness effects. This effect is worth something like 0.5°/g - 1.0°/g, and since this happens outside the suspension it will happen in an IRS car as well. It even contributes to sprung mass roll, which explains in part why the "apparent roll" in pictures ends up being slightly greater than what you might calculate from roll stiffnesses alone. It's probably part of the reason people sometimes modify stick axles for a bit of negative camber . . . or don't get an axle "fixed" to zero camber when little negative cambers are found.

Also, Norm, where are you at? You made a fairly interesting (to me) comment over on Camaro 5 about the new front suspension needing a place of compliance with the dual ball joint suspension... any insight into what you are thinking? The dual ball joint setup screams bind during compression/droop + turning but I honestly don't know. That could kill off performance arms with solid bushings or near solid bushings if it does...

Unless the tension rod and lateral link have sphericals hiding inside their chassis-side ends, something's got to give under steering, suspension travel, and off-axis rotation will have to be accommodated under braking (toe consequences?). For classes where the method of accommodating multiaxis rotation disallows sphericals, you'd be in it for some sort of custom compliance redesign. DIY voiding might be where such tweaking begins.


Norm

 

[Whiskey11]

Unless the tension rod and lateral link have sphericals hiding inside their chassis-side ends, something's got to give under steering, suspension travel, and off-axis rotation will have to be accommodated under braking (toe consequences?). For classes where the method of accommodating multiaxis rotation disallows sphericals, you'd be in it for some sort of custom compliance redesign. DIY voiding might be where such tweaking begins.


Norm

So would a setup similar to this bind if you did use spherical bearings for the suspension bushings up front? To me it seems like it would be constantly fighting itself, between the two ball joints, the virtual pivot, and the steering arm. Or is it safe to assume that Ford calculated this out already to ensure that if bind occurs, it only happens at EXTREMES of travel?

The bushing compliance is certainly going to be fun to mess with... it's one reason I don't like these setups since a conventional lower arm doesn't take up more space than this does but the bushings can be made in a single axis and can use solid, non-metal bushings (Delrin, and other Acetals) for competition use to skirt rules about bushings being solid.

This may be the vehicle, if I buy one (if Ford hits my weight goal ), that pushes me to pick up a program like WinGeo or build my own suspension analysis Excel spreadsheet because I'm wondering if I couldn't gain more by widening the track for negative camber then by adjusting it at the strut top. I also don't wonder myself if Ford hasn't already thought of that and included it by default since small changes in the lateral link should make pretty decent changes to static negative camber.

 

[kcbrown]

This may be the vehicle, if I buy one (if Ford hits my weight goal ), that pushes me to pick up a program like WinGeo or build my own suspension analysis Excel spreadsheet because I'm wondering if I couldn't gain more by widening the track for negative camber then by adjusting it at the strut top. I also don't wonder myself if Ford hasn't already thought of that and included it by default since small changes in the lateral link should make pretty decent changes to static negative camber.

That would require that the tension link be able to swing horizontally about its inboard mounting location, though, right? It almost certainly does a bit of that anyway as a result of the bushing it's using there, so maybe that wouldn't be a concern...

Also, lengthening the lateral link would result in pushing the wheel towards the rear (I'm presuming that the tension link inboard mount is towards the rear) and would also require the lateral link to rotate about its inboard mount unless you also lengthened the tension link. Might not be enough to make any difference, though...

 

[jmauld]

Can't wait to see which company is the first to throw out a set of polyurethane bushings for that front suspension.

 

[Whiskey11]

That would require that the tension link be able to swing horizontally about its inboard mounting location, though, right? It almost certainly does a bit of that anyway as a result of the bushing it's using there, so maybe that wouldn't be a concern...

Also, lengthening the lateral link would result in pushing the wheel towards the rear (I'm presuming that the tension link inboard mount is towards the rear) and would also require the lateral link to rotate about its inboard mount unless you also lengthened the tension link. Might not be enough to make any difference, though...

The tension link should be able to rotate about it's bushing as well as the lateral link in 3D. Whether or not the length of the tension link becomes a factor when the wheel turns is a big unknown. I posted a .gif somewhere of the BMW 3 series front suspension and it does look like some force is applied and pulling on the tension link to change its length.

The tension link is mounted forward so lengthening the lateral link should pull the wheel forward some (yay caster change!). Both links will move in 3D so it couldn't be a cylindrical bushing with zero compliance (so no Delrin cylindrical bushings for the S550) but it could be Poly or some other compliant substitute... I'm questioning the wisdom of doing such as I think the system requires some compliance in the bushings to not completely bindfest itself. It's difficult for me to picture the motion, even with various videos and .gifs to show how it all moves.

 

[jmauld]

The tension link is mounted forward so lengthening the lateral link should pull the wheel forward some (yay caster change!). Both links will move in 3D so it couldn't be a cylindrical bushing with zero compliance (so no Delrin cylindrical bushings for the S550) but it could be Poly or some other compliant substitute... I'm questioning the wisdom of doing such as I think the system requires some compliance in the bushings to not completely bindfest itself. It's difficult for me to picture the motion, even with various videos and .gifs to show how it all moves.

Take a look at the old nissan suspension from the 80s/90s. It's very similar to this, except the Tension rod is hard mounted to the control arm. Lots of people liked to throw poly bushings into the front arms. Lots of those people then ripped the control arm into two pieces, since they removed the compliance from the tension rod. I doubt the ford setup will rip pieces apart since they aren't hard mounted to each other in the same fashion, but I would not count on them having designed it so that there is no compliance requirement for that tension rod. The best way to tell, IMO is by the size of that bushing. If it's a big rubber bushing, then you know it needs to move around in the joint.

 

[tjm73]

Looks like the front and rear suspension is in cradles.

 

[Norm Peterson]

So would a setup similar to this bind if you did use spherical bearings for the suspension bushings up front?

Only when the first spherical joint runs out of angular travel. When that happens, the four bar mechanism that it belongs to suddenly becomes a triangulated structure that doesn't want to move any further in that direction at all. Probably a worse bind situation than Delrin/Delrin bushed rear control arms.

To me it seems like it would be constantly fighting itself, between the two ball joints, the virtual pivot, and the steering arm. Or is it safe to assume that Ford calculated this out already to ensure that if bind occurs, it only happens at EXTREMES of travel?

Ford has to have considered this and put geometric bind out at or beyond the extremes of travel. Not doing this raises the possibility of catastrophic suspension component failure (resulting in the suspension becoming structurally unstable and collapsing).

This may be the vehicle, if I buy one (if Ford hits my weight goal ), that pushes me to pick up a program like WinGeo or build my own suspension analysis Excel spreadsheet because I'm wondering if I couldn't gain more by widening the track for negative camber then by adjusting it at the strut top. I also don't wonder myself if Ford hasn't already thought of that and included it by default since small changes in the lateral link should make pretty decent changes to static negative camber.

It takes the same amount of lateral relocation at the ball joint as it does at the strut top to accomplish a given amount of camber change. Guessing at a 20" strut top to ball joint length, a 1° camber change needs either end to move horizontally in front view about 0.35" relative to the other.


Building your own spreadsheet can be satisfying . . . and a never-ending effort as you keep refining and adding more to it.

Commercially, there is also Susprog3D (requires Excel), Performance Trends Suspension Analyzer, and Dynatune (I heard about this one only recently, also Excel-based).


Norm

 

[Norm Peterson]

Just because I had a rather exaggerated picture handy. Static front camber is something like -2.3°.


Norm

 

[Whiskey11]

Only when the first spherical joint runs out of angular travel. When that happens, the four bar mechanism that it belongs to suddenly becomes a triangulated structure that doesn't want to move any further in that direction at all. Probably a worse bind situation than Delrin/Delrin bushed rear control arms.

Solid copy, I wasn't sure if the tension link needed to change it's effective length slightly in order for the suspension to work since watching the video of the Pontiac G8 suspension and the gif of the M3 suspension, it looks like the tension link gets pulled some when turning the wheel, hence why I asked.

Ford has to have considered this and put geometric bind out at or beyond the extremes of travel. Not doing this raises the possibility of catastrophic suspension component failure (resulting in the suspension becoming structurally unstable and collapsing).

I would hope so anyway!

It takes the same amount of lateral relocation at the ball joint as it does at the strut top to accomplish a given amount of camber change. Guessing at a 20" strut top to ball joint length, a 1° camber change needs either end to move horizontally in front view about 0.35" relative to the other.


Building your own spreadsheet can be satisfying . . . and a never-ending effort as you keep refining and adding more to it.

Commercially, there is also Susprog3D (requires Excel), Performance Trends Suspension Analyzer, and Dynatune (I heard about this one only recently, also Excel-based).
Norm

What I meant is, will there be more adjustment at the lateral link than at the strut top since the strut tower pictures show a very small opening, smaller than the S197's opening, in which to adjust camber. If that is the case it may be more prudent for those of us looking at ST and SP to replace the lateral link then to use adjustable camber plates. I'd have to re-read the rules on whether or not you could still replace the stock strut mount then so long as the replacement isn't adjustable for camber (aside from slack in the factory bolt holes). With my luck, probably not!

The added track width could help with front end grip and dial out some of the dialed in track width discrepancies and it's negative effects.

FWIW, the rear end's lower control arm bushings give me a headache. Certainly not as simple as replacing with delrin... you might get away with one in Delrin and the other in poly since they are not linear to each other... I don't know why Ford chose that method of attachment, it seems to have no advantage over putting them in line with each other.

 

[Norm Peterson]

Not putting them coaxially is probably because the forces on the two attachments are not parallel (think about fairly large longitudinally rearward loads caused by hitting bumps). A cylindrical bushing that must pivot about its bolt axis would rather the big loads be radial than axial. Proper bushing design mitigates the induced bind.


Norm

 

[05yellowgt]

So what is this general rear suspension going to do say when subjected to a 4.5k clutch dump on bias ply tires on a prepped track? Is the design prone to wheel hop, or can that be anticipated at this point? I'm sure Ford has done more than their share of testing for the drag race crowd, but they never do as much as actual owners will.

 

[csamsh]

So what is this general rear suspension going to do say when subjected to a 4.5k clutch dump on bias ply tires on a prepped track? Is the design prone to wheel hop, or can that be anticipated at this point? I'm sure Ford has done more than their share of testing for the drag race crowd, but they never do as much as actual owners will.

Too soon to speculate probably, and, also, you're not asking people who care.



...that's a joke.

How did the Terminator react? I would guess, imagine how it did, and think it will do better since the S550 is designed from the start for IRS, is 10 years newer, and will need to probably run a 12.7 or quicker stock in order for the magazines to take it seriously.

 

[05yellowgt]

I'm actually more interested than ever in the handling aspects of the S550. Midly lowered with wide and sticky meats and a few exhaust and tuning mods will be the direction for an EB or 5.0 PP 2015 I hope to have in my garage

 

[Norm Peterson]

So what is this general rear suspension going to do say when subjected to a 4.5k clutch dump on bias ply tires on a prepped track? Is the design prone to wheel hop, or can that be anticipated at this point? I'm sure Ford has done more than their share of testing for the drag race crowd, but they never do as much as actual owners will.

We went through some of this - the geometry part anyway - over on Mustang6G, and IIRC the conclusion was that antisquat was going to be pretty good as A-S for IRS systems go. Not up to the 100% that's easy enough to get with a stick axle.

I don't recall any discussion getting into bushing compliance and that effect on hop though. I'd expect fixes similar to what they're doing for the 5th gen Camaros.


Norm

 

[kcbrown]

Frankly, I won't be surprised if the amount of difference in the handling between the S550 and the S197 on the track comes down to differences in the size of the tires, the effective wheel rates in various regimes, the front:rear grip balance dialed in, differences in CG and roll centers, and AS properties.

Which is to say, I somehow suspect that the IRS isn't going to make much of a difference on the track except possibly when comparing stock with stock.

But then, maybe that's because I own an S197.

Sure is going to be interesting to see just what can be done with the IRS in the S550, though.