Steering rack speed

[valentinoamoro]

Yeah, as others mention steering quickness and effort are to different things.

My Volvo has speed sensitive steering and changes the effort depending on speed (loose at low speed). That is a good implementation as simply making a steering heavy/loose is strange to me (my M6 does that, I believe thats what the Mustang will do as well as the most cars that offer variable effort). I prefer a low effort steering at slow speeds when parking and a higher effort at highway speeds when straight line tracking is critical.

Some cars also change the ratio depending on the distance from the center (this is variable quickness) etc. That's a different thing.

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[EXP Jawa]

It shouldn't. Electric power-assisted steering (EPS or EPAS) is just a form of steering boost to reduce the amount of effort it takes to turn the wheel. The different settings should increase or decrease the steering weight. That might have an impact in steering feel and/or responsiveness, but those are typically depend far more on other factors.

There are also forms of EPS that have the ability to alter the steering ratio on the fly as well. My company also has a steering system division. I don't have contact with those guys, but I've seen the product, its pretty cool. Basically, it has a planetary gearset in the ESP drive that can be engaged to speed up or slow down the steering input before it gets to the actual steering rack. This can also, with programming, be used to allow the stability control system some access to steering input, which gets a little too Big Brother for me. I have no idea who is using it though.

 

[MyRed97]

I haven't heard anything about it on the new S550, but 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?

 

[OppoLock]

There are also forms of EPS that have the ability to alter the steering ratio on the fly as well. My company also has a steering system division. I don't have contact with those guys, but I've seen the product, its pretty cool. Basically, it has a planetary gearset in the ESP drive that can be engaged to speed up or slow down the steering input before it gets to the actual steering rack. This can also, with programming, be used to allow the stability control system some access to steering input, which gets a little too Big Brother for me. I have no idea who is using it though.

That's awesome. I like to say I'm not a big fan of traction nets, but I'm all for tech that improves it so long as it's transparent and natural. Not to go too off tangent, but I've been trying to do more reading on eLSDs. They're my new obsession, but what I'm curious to know is whether or not the inclusion of EPS is a requirement or even some kind of influencing factor for its operation. I don't know of many cars with a hydraulically powered steering system and an eLSD. Are you familiar at all with them?

 

[EXP Jawa]

That's awesome. I like to say I'm not a big fan of traction nets, but I'm all for tech that improves it so long as it's transparent and natural. Not to go too off tangent, but I've been trying to do more reading on eLSDs. They're my new obsession, but what I'm curious to know is whether or not the inclusion of EPS is a requirement or even some kind of influencing factor for its operation. I don't know of many cars with a hydraulically powered steering system and an eLSD. Are you familiar at all with them?

I've been exposed to various forms of eLSD, and have done some investigation into developing one for the company I work for. But there are a lot of different solutions out there. They really all can potentially operate independent of other systems, depending on the intent. Its really up to the chassis controls people to decide how integrated - and complex - they want the system to be. It can be as basic as the eLocker in the Raptor (I know, not technically an eLSD, but I'll include anyway), where its on/off at the driver's whim (with some stipulations). Or it can very integrated into a complex AWD system, like the former Honda SH-AWD.

Any proper eLSD designs use some form of electronic governed clutch or lock-up device, and as long as a signal is sent to the actuator, it engages. Some are on/off, so can vary torque bias ratio on the fly. It depends on the sophistication of the controls and the hardware. But none really need to have any tie-in to the EPS, ESP or even the TCS, though it makes a lot of sense for to be connected to the later. The lack of HPS and eLSD on cars probably stems more from the timing of the introduction of eLSD and the coincident switch in the market from HPS to EPS.

For the record, though, there are any number of OEMs that are using the term "eLSD" for a glorified traction control system. These do not have actual differential-based slip-limiting features, but rather depend on brake control to try to get to the same result. The difference between these and more traditional TCS systems is really just in the sophistication of the controls. The Focus ST is an example of this, and while it does a lot of neat things, there are shortage of people crying for Ford to include an actual LSD...

 

[OppoLock]

I've been exposed to various forms of eLSD, and have done some investigation into developing one for the company I work for. But there are a lot of different solutions out there. They really all can potentially operate independent of other systems, depending on the intent. Its really up to the chassis controls people to decide how integrated - and complex - they want the system to be. It can be as basic as the eLocker in the Raptor (I know, not technically an eLSD, but I'll include anyway), where its on/off at the driver's whim (with some stipulations). Or it can very integrated into a complex AWD system, like the former Honda SH-AWD.

Any proper eLSD designs use some form of electronic governed clutch or lock-up device, and as long as a signal is sent to the actuator, it engages. Some are on/off, so can vary torque bias ratio on the fly. It depends on the sophistication of the controls and the hardware. But none really need to have any tie-in to the EPS, ESP or even the TCS, though it makes a lot of sense for to be connected to the later. The lack of HPS and eLSD on cars probably stems more from the timing of the introduction of eLSD and the coincident switch in the market from HPS to EPS.

For the record, though, there are any number of OEMs that are using the term "eLSD" for a glorified traction control system. These do not have actual differential-based slip-limiting features, but rather depend on brake control to try to get to the same result. The difference between these and more traditional TCS systems is really just in the sophistication of the controls. The Focus ST is an example of this, and while it does a lot of neat things, there are shortage of people crying for Ford to include an actual LSD...

Ah yes, the cop-out "e-diff" that's become so common with the vanilla German offerings. I like to call that the brake toaster. One of the reasons that the Mk7 GTI was so intriguing to me was the fact that it had a true electronically controlled mechanical LSD up front if you opt for the performance package. Otherwise it comes with XDS, the marketing term for their brake torque vectoring system. Not a fan. I'm just anxious to get out of my 335i... it should be a crime to sell a RWD car putting out more than 300 ft-lb and stick it with an open diff.

And thanks for the info! The timing explanation explains a lot.

 

[Feeshta]

I've always wondered why no aftermarket companies seem to offer any upgrades or even just alternatives when it comes to steering. The only real options I have ever seen revolve around swapping a factory option into a car that didn't come with it stock.

Steering performance is a defining characteristic of a cars performance, often one of the key things mentioned in reviews of performance cars. It's not particularly complex or difficult to replace/modify. So why is it that no aftermarket companies offer alternatives?

 

[valentinoamoro]

I've always wondered why no aftermarket companies seem to offer any upgrades or even just alternatives when it comes to steering. The only real options I have ever seen revolve around swapping a factory option into a car that didn't come with it stock.

Steering performance is a defining characteristic of a cars performance, often one of the key things mentioned in reviews of performance cars. It's not particularly complex or difficult to replace/modify. So why is it that no aftermarket companies offer alternatives?

True! Also, in the few months I've spent on 6G I've not noticed anyone mention anything about the steering - most talk about power.

I know the steering will have more feel than the S197 - Ford mentioned that multiple times in their press releases, they also bolted the rack directly w/o soft bushings etc....I do wish its (Steering) quicker than the current car though.

 

[valentinoamoro]

Ah yes, the cop-out "e-diff" that's become so common with the vanilla German offerings. I like to call that the brake toaster. One of the reasons that the Mk7 GTI was so intriguing to me was the fact that it had a true electronically controlled mechanical LSD up front if you opt for the performance package. Otherwise it comes with XDS, the marketing term for their brake torque vectoring system. Not a fan. I'm just anxious to get out of my 335i... it should be a crime to sell a RWD car putting out more than 300 ft-lb and stick it with an open diff.

And thanks for the info! The timing explanation explains a lot.

Wanted to add some more detail, agree with the comments.

The reason a lot of the cars offer that is its 1) a cheap way to simulate the LSD (stop spinning the inner wheel and ensuring power goes to the outer wheel) and 2) go beyond to compensate for understeer (by causing a wheel to drag creating a turning effect, something I think an LSD cant) - all it takes is programming and has no added weight while doing two different tasks. Its not shabby if implemented well on a street setup however for 1) compared to a traditional LSD for it is not as effective as it has delays (not instant), heats up the brakes and cant reign in all the torque. It's not as good as a clutch driven pure torque vectoring system for 2) as it reduces power to the inner wheel to create a turning moment and that too partially Vs adds more power to the outer wheel to cause rotation - meaning, its slows the car.

My ideal though is a proper LSD (ex: Torsen) and optionally, the ability to overdrive a wheel like Audi does with its rear torque vectoring diff in select cars and of course, SH-AWD offers. However, these kinds of tricks (the torque vectoring) are not needed if the car is balanced as it adds weight and complexity - I dont believe the Cayman and Boxster use torque vectoring (although I would argue they are crying out for an LSD) and they put down incredible times for their power, the 911 offers it as its rear heavy.

The STI is a odd one here, offering 3 LSD's (I think the center one is fully lockable) and the brake based e-diff in the new gen (drag effect).

The Evo offers the LSD's and torque vectoring through clutch, not brakes (overrotation). So does the RS5.

I know the Focus and Fiesta have a brake e-diff, which works well for the street (and as you mention GTI with XDS) - drag effect.

I'm happy the Stang offers the Torsen LSD - it is a proper enthusiasts traditional setup. Not sure if they are doing a brake based torque reduction on select wheels to make the car rotate faster, but the Torsen is what I want. It will put the power down. It will not help with a creating a turning moment like a over-rotating torque vectoring or a braking torque vectoring would do.

 

[OppoLock]

Steering "feel" is influenced by a bunch of factors. Suspension geometry and tuning will make a huge impact. Overall weight, distribution, steering boost, tired size and compound, etc. play into it.

I'm in the camp that thinks a whole lot of modern cars don't have a lot of the so-called feel; that's something you'd find in a kart. I do hope that the S550 is accurate and changes enough to let you know when you're at or over the traction limit though.

 

[OppoLock]

My ideal though is a proper LSD (ex: Torsen) and optionally, the ability to overdrive a wheel

This is why I love eLSDs. Instead of being reactive (like a torque sensing LSD), it uses a number of active factors to preemptively send torque to the wheel that needs it most. I feel like it's the next requisite for high powered RWD cars if they want to keep up with AWD cars. It's come down to figuring out how to get torque to the ground now.

 

[Feeshta]

Steering "feel" is influenced by a bunch of factors. Suspension geometry and tuning will make a huge impact. Overall weight, distribution, steering boost, tired size and compound, etc. play into it.

I'm in the camp that thinks a whole lot of modern cars don't have a lot of "feel"; that's something you'd find in a kart. I do hope that the S550 is accurate and changes enough to let you know when you're at or over the traction limit though.

yes all of those things have an impact, but the most raw and easy to change thing about steering is the ratio. The steering ratio is probably the single thing I would change in my 540i. It's simply too slow for a performance car.

I don't expect items that have thousands of hours of track testing, I just think that somene out there should be offering a quicker ratio steering rack or the like for most performance cars.

As far as steering feel,, unfortunately I feel it is a dead art to a large degree. Honestly the best car I ever drove for steering feel was my first car, which was a 1980 VW rabbit diesel with no power steering. Every other performance aspect of that car was horrific, but the steering was clear and communicative. The pizza cuter tires were actually better in that respect than modern wide profiles.

 

[valentinoamoro]

yes all of those things have an impact, but the most raw and easy to change thing about steering is the ratio. The steering ratio is probably the single thing I would change in my 540i. It's simply too slow for a performance car.

I don't expect items that have thousands of hours of track testing, I just think that somene out there should be offering a quicker ratio steering rack or the like for most performance cars.

As far as steering feel,, unfortunately I feel it is a dead art to a large degree. Honestly the best car I ever drove for steering feel was my first car, which was a 1980 VW rabbit diesel with no power steering. Every other performance aspect of that car was horrific, but the steering was clear and communicative. The pizza cuter tires were actually better in that respect than modern wide profiles.

I agree, steering feel is a dead art. My M6 has accurate steering thats well weighted but it has as much life as a zombie. I hear the new STI has an incredible quick (but like 99.9% of cars a dead) rack

 

[OppoLock]

yes all of those things have an impact, but the most raw and easy to change thing about steering is the ratio. The steering ratio is probably the single thing I would change in my 540i. It's simply too slow for a performance car.

I don't expect items that have thousands of hours of track testing, I just think that somene out there should be offering a quicker ratio steering rack or the like for most performance cars.

As far as steering feel,, unfortunately I feel it is a dead art to a large degree. Honestly the best car I ever drove for steering feel was my first car, which was a 1980 VW rabbit diesel with no power steering. Every other performance aspect of that car was horrific, but the steering was clear and communicative. The pizza cuter tires were actually better in that respect than modern wide profiles.

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 agree, steering feel is a dead art. My M6 has accurate steering thats well weighted but it has as much life as a zombie. I hear the new STI has an incredible quick (but like 99.9% of cars a dead) rack

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.

 

[valentinoamoro]

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.

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!

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