Steering rack speed

[Tim Hilliard]

With the current S197 cars you had to option to install the Boss 302S/R rack. It was "For Off-Road Use Only" but it was calibrated for road racing with slicks. My guess is it gave you plenty of 'road feel' and feedback.

https://www.fordracingparts.com/parts/part_details.asp?PartKeyField=13185

Personally I'm just waiting until mid '16 for Ford Racing to get the pieces out for the PWC/Conti Race spec cars so I can ruin all the street manners of my car :doh:

Sponsored

 

[EXP Jawa]

I should point out that you are incorrect in stating that an LSD helps put the power down but does not help reduce understeer. The truth is that a torque-biasing LSD is as much a handling aide as it is a traction aide. That's why Ford used it over their own Traction-Lok. A differential like the Torsen actually has a passive torque-vectoring behavior, and was doing so well before the term "torque-vectoring" was coined. That's basically exactly what it means to be torque-biasing. You actually do get a differential-induced oversteer moment if the conditions are right. For example, at corner exit under heavy throttle, the differential will essentially hold the inside tire at its traction limit and bias additional torque to the outside wheel. This has the effect of actually creating a yaw moment on the car in the direction of turn. If the car is prone to understeer, this essentially acts as an understeer correction.

The key is, though, that the torque bias ratio has to be tuned to the chassis properly to maximize the effect. You can see in the above example that too much bias could lead to too much oversteer, and not enough might not be able to prevent the inside wheel from slipping. So there is a tuning game that has to be played when the car is set up. It is passive - meaning it'll do the same thing no matter what, in a proactive way - whereas the electronic systems are active, and react to correct an unstable situation. So it has to be tuned right in the first place. In a lot of cases, a properly tuned mLSD can mitigate the operation of both traction and stability control intervention. Basically, it works ahead of the electronics, making it so that those systems work less often and less intrusively.

Also, in the Focus ST, the understeer correction comes from the ESP being tied into the stability program, or so I'm told. That's an area where the computer is helping to steer the car so that it feels less objectionable to the driver.

 

[w3rkn]

I have all the feedback I need in my hydraulically steered 135is... while the newer M235i went to electronic steering. The road's feedback will be different in both. Most prefer hydraulic... because it is direct feeling, where-as the electronic is all servos and the driver is isolated from the road feel.



Secondly, the steering ratio on my BMW is horrid & one of the main reason I will not be keeping my BMW. It's almost dangerously slow ratio. BMW knows this because of the rack they put in the 1M.


I hope Ford gets both the feedback, & the ratio just right...

 

[Feeshta]

I had to look up a 540i's steering ratio... 17.9:1... yikes. I feel like my car's 16:1 is on the slow side of a good compromise. I'd like something a little quicker, but I'll reserve judgement for an actual test. A ratio is only part of the story.


I have to give kudo to Subie for carrying over the hydraulic assist for the new-gen STi. You don't see that much anymore.

Yes the 540i has very slow steering. It's a bit of a bear in a parking lot and the like. It's actually a popular option to find an M5 rack and install it in your 540i, it reduces lock to lock from 3.6 to 2.9 turns which is quite a margin. An unfortunate side effect is that you lose the M5's servotronic variable assist, and are basically stuck with full stiff.

My cousin drives a 2006 STI, and I have driven it about 6 times. It has an extremely quick ratio, something like 13:1, or 2.4 turns lock to lock and is fun to toss around. That said, it is too heavily boosted, and has very little feel. Small bumps in the road make the car difficuly to control if you only have one hand on the wheel while shifting, which you have to do a lot with that gearbox. There isn't enough resistance to help you stabalize your arm, and the quick ratio means the car moves quite a bit. The STI also has a very poor turning radius, which seems to be an issue with many front and AWD cars.

Something in between would be welcome, If you could take the STI's rack and give it variable boost ratios like the Mustang has, that would be pretty good in my opinion.

I would like to give kudos to Subie but part of me suspects it had more to do with cost savings - the WRX got most of the love and they carried over the engine etc with poor STI...

Regardless, as you mention, the hydraulic assist was a good move. I did test out the 15 STI and while it was great, I felt it was a bit slow (Ok, I'm spoilt!!!), the interior was really iffy and primitive looking, it felt too stiffly sprung and it felt too boy racerish for my taste - that rear view and spoiler were over the top. Lastly, I was wary of the ringland stories (my friend has an STI that has had a few catastrophic failures and he is selling - had had a few). I did like the 4 doors, the increased rear seating space and the looks were not as bad as I thought it would be (frontal). Steering was super tight!

My Cousin's STI has has numerous quality issues in under 80K miles. The rear shocks have failed twice, they started sticking and made an already unpleasantly stiff ride pretty close to unbearable. The power steering pump went due to the fact that they didn't apply enough heat shielding around the plumbing where it passes near the turbo and it cooked the fluid. The turbo went just went out and had to be replaced. Since he had the turbo replaced, it has also had an issue with the AC compressor binding. It hasn't been the most bulletproof car out there, and does not give me a warm fuzzy towards buying one of my own.

I have all the feedback I need in my hydraulically steered 135is... while the newer M235i went to electronic steering. The road's feedback will be different in both. Most prefer hydraulic... because it is direct feeling, where-as the electronic is all servos and the driver is isolated from the road feel.



Secondly, the steering ratio on my BMW is horrid & one of the main reason I will not be keeping my BMW. It's almost dangerously slow ratio. BMW knows this because of the rack they put in the 1M.


I hope Ford gets both the feedback, & the ratio just right...

I had an 09 135i prior to my 540i. The steering was pretty decent, but not stellar. Honestly I have not driven a car made within the last 10 years that had really good steering. Personally I think it comes down to the proliferation of huge wheels with wide profile tires. All of that weight, and the large contact patch requiring more steering assist, has made it nearly impossible to provide quality feel.

 

[valentinoamoro]

I should point out that you are incorrect in stating that an LSD helps put the power down but does not help reduce understeer. The truth is that a torque-biasing LSD is as much a handling aide as it is a traction aide. That's why Ford used it over their own Traction-Lok. A differential like the Torsen actually has a passive torque-vectoring behavior, and was doing so well before the term "torque-vectoring" was coined. That's basically exactly what it means to be torque-biasing. You actually do get a differential-induced oversteer moment if the conditions are right. For example, at corner exit under heavy throttle, the differential will essentially hold the inside tire at its traction limit and bias additional torque to the outside wheel. This has the effect of actually creating a yaw moment on the car in the direction of turn. If the car is prone to understeer, this essentially acts as an understeer correction.

Got it. I was not aware that the LSD could help with understeer reduction. Thanks for explaining!

 

[EXP Jawa]

Got it. I was not aware that the LSD could help with understeer reduction. Thanks for explaining!

That's a big part of what sells them - part of why Ford uses it on Mustang, and GM on the Z/28, why they've become popular aftermarket for track day cars.

 

[S550Boss]

I know the new Focus ST (at least Euro Spec) is getting Fords new variable ratio steering rack. Maybe look for it on a future model or refresh of the Mustang?

No, the ST is not getting this in the refresh coming up. And it's not a variable ratio rack, it's a variable ratio actuator behind the steering wheel.

And the Euro and North American ST versions are identical, except for minor little details such as the door guards, folding mirrors, Recaro-matching *back seat*, radio/nav options, and the wagon version. Along with the non-North American diesel option.

 

[MadMoose]

The slow steering ratio on the previous GT/boss was one of my complaints. I love the quick ratio on the fiesta st which I believe is 13.6:1

 

[Sterling Archer]

You know, you guys can actually tune the steering. I don't know why more people haven't been doing this, but the same way you can flash the ecu to modify the engine parameters, you can modify the actuator output on the wheel.

So given that the new mustang has several driving and steering modes, you could hypothetically just tune the sport mode and sport handling to be super aggressive and leave the city modes alone for comfort.

 

[petraman]

For me, it's not really about the feel/heft, but more about the speed. I love heavy steering but more than that I love quick steering. In the ST, for 99% of turns, I don't have to take both hands off the wheel. I can keep them 9 and 3 all the way through.

 

[S550Boss]

You know, you guys can actually tune the steering. I don't know why more people haven't been doing this, but the same way you can flash the ecu to modify the engine parameters, you can modify the actuator output on the wheel.

So given that the new mustang has several driving and steering modes, you could hypothetically just tune the sport mode and sport handling to be super aggressive and leave the city modes alone for comfort.

You didn't read the full thread... that's feel, not ratio. It has nothing to do at all with aggressiveness.

 

[S550Boss]

The slow steering ratio on the previous GT/boss was one of my complaints. I love the quick ratio on the fiesta st which I believe is 13.6:1

Exactly... Ford of Europe has their dynamic tuning act together in a way that Team Mustang and SVT have never had. Team Mustang should have had their European team do the steering.
I was comparing my Boss and ST this morning and wondering what the heck the Dearborn people were thinking... what a dog. Giant bumper car steering wheel, slow ratio, lurching response. And the 2015 has the same rack and shaft, but a slightly smaller wheel (not small enough).

 

[Sterling Archer]

You didn't read the full thread... that's feel, not ratio. It has nothing to do at all with aggressiveness.

You can modify that as well, it's just an optical sensor that detects steering wheel position and outputs a command to turn the wheels. You can set that to even be exponential like the steering on the LaFerrari, such that you can make u-turn without overlapping hands.

 

[w3rkn]

You can modify that as well, it's just an optical sensor that detects steering wheel position and outputs a command to turn the wheels. You can set that to even be exponential like the steering on the LaFerrari, such that you can make u-turn without overlapping hands.

The discussion was, if the new Mustang has the same rack as the ST, etc.. & if it has a variable ratio.


Many do not think it does...

 

[Sterling Archer]

The discussion was, if the new Mustang has the same rack as the ST, etc.. & if it has a variable ratio.


Many do not think it does...

You don't have to take my word for it, but seeing how I am an electrical engineer working in the auto industry, I'd hope I'd know what I'm talking about...

Sponsored