Can steering feel, tactility, be improved? Without sacrificing adjustability?

[cmspooner]

Originally Posted by mobybrz

What good is the warranty for if not replacing parts when I experiment? My prototype version is getting installed this weekend, hopefully ordering a PCB version this week...

Did you get a chance to try this out yet, and if so; how did it work?

[mobybrz]

Originally Posted by cmspooner

Did you get a chance to try this out yet, and if so; how did it work?

No...haven't been home in over a month due to work

[JDKane527]

Lexus has used different steering ECUs to change the feel of the car. Between the IS250/IS350 and IS-F, they had used different ECUs where the IS-F was stiffer and turning on sport mode further increased the stiffness to make it feel more direct.

Not sure if these cars have a steering ECU or if it is integrated into the main ECU or steering rack.

[mobybrz]

Originally Posted by JDKane527

Not sure if these cars have a steering ECU or if it is integrated into the main ECU or steering rack.

Yes, there is a power steering ECU. It is connected to the CAN, the TRQ1 and TRQ2 steering sensors, and an angular resolver (angle sensor). It outputs to the power steering motor.

What you mention between the IS versions isn't (or at least is extremely likely to be) different ECUs. It is more likely different *maps* juts like we are all aware of with ECUTEK on the engine ECU. Theoretically, it should be possible to perform the same reverse engineering work on the power steering ECU to allow maps to be edited or adjusted. I wouldn't be surprised if there is a different EPS map between the FR-S and the BRZ given the differences in suspension.

As it stands, I would imagine the GT86/FR-S/BRZ steering maps based on mostly on speed and driver applied torque. There is might be/likely is an influence from the VSC mode settings, steering angle, gear, and measures of yaw angle (side slip/rotation, the same measure that drives VSC intervention).

To give an example, one could theoretically create a map that is designed to assist the driver i an accident avoidance manuever on the highway. The ECU could detect a likely avoidance maneuver and provide an increased steering torque initially (effecitvely increasing the drivers turning rate) before ramping down the provided torque (slowing the drivers turning rate) to prevent an overcorrection and help dampen any potential for a tank slapper. You could use (again theoretically) anything coming over the CAN to influence the map.

[regal]

But the issue is the numbness because the EPS gear holds the wheel so tight that you will never have the manual rack feel. I doubt that can be programmed out its pure mechanical.

[mobybrz]

Originally Posted by regal

But the issue is the numbness because the EPS gear holds the wheel so tight that you will never have the manual rack feel. I doubt that can be programmed out its pure mechanical.

Just to clarify, my last post was simply about the operation of the eps ecu as it related to JDK's question.

I honestly don't know if it can or cant be programmed out. I do know that we have sen through the engine tuners how conservative they have been with the car. The motor itself is variable torque and any change in that torque (whether it is a change in the applied torque or turning the motor off) will change the entire mechanical dynamics of the system. I have no way of modeling it but its just basic physics. Any change you make, bushings, tires, wheels, shocks, etc. Are going to have an effect. Personally I feel my Brz is overboosted for my personal tastes even with stickier tires. I can tell you from having unplugged the eps that feel was greatly improved but effort was then to high at low speeds. The car also lost some invented resistance. I think the eps is a fair tradeoff for the quick ratio rack as it stands but obviously can be better.

Obviously this is all just my .02 but it is a forum after all

[regal]

Originally Posted by mobybrz

Just to clarify, my last post was simply about the operation of the eps ecu as it related to JDK's question.

I honestly don't know if it can or cant be programmed out. I do know that we have sen through the engine tuners how conservative they have been with the car. The motor itself is variable torque and any change in that torque (whether it is a change in the applied torque or turning the motor off) will change the entire mechanical dynamics of the system. I have no way of modeling it but its just basic physics. Any change you make, bushings, tires, wheels, shocks, etc. Are going to have an effect. Personally I feel my Brz is overboosted for my personal tastes even with stickier tires. I can tell you from having unplugged the eps that feel was greatly improved but effort was then to high at low speeds. The car also lost some invented resistance. I think the eps is a fair tradeoff for the quick ratio rack as it stands but obviously can be better.

Obviously this is all just my .02 but it is a forum after all

Interesting thoughts, I agree as far as EPS goes this car is pretty good. It will be interesting to see how the arudino programming posted earlier turns out.

[Trettiosjuan]

Originally Posted by Trettiosjuan

Is it possible that the rack is stiff when brand new? Perhaps explaining my relative disappointment compared to other testimonies?

I had another car that had this effect, not much feel in the beginning, after 6000miles or so, it loosened up and really started talking to me...

A little follow up. I now got myself a GT86 with little miles on it, and I have a similar impression as the first car I testdrove. But as stated before, the second one I testdrove seemed to have good feel to me, and on mine I do think I can feel som tightness in the rack. So I will just give it some time to see if it loosens up, if after 10k or so it still feels the same, I'll have a shot at those rack bushings...

[Trettiosjuan]

Update 2: now I have changed to the Turn in Concepts steering rack bushes. This made some difference, now some feel is coming trough but still felt muted. But then I realigned the front end with some moderate neg camber and especially some toe-out and this boosted the communication felt from the solid rack bushes. Now the steering talks and feels in sync with what you feel trough the seat of the pants. Now a happy camper!

PS: otherwise stock chassis and 16" wheels with OEM grade tyres.

[SeanBlader]

Can you post the specifics of your alignment in case some of us want to try it out?

[Trettiosjuan]

0,2 degrees toe-out per side and, in lesser degree relevant here, 1 degree neg camber.

[regal]

Has good as a Miata now?

[Trettiosjuan]

Sorry, no recent experience with a Miata...

[JDM-dono]

I've had similar experiences to you regarding steering feel from day 1. My advice is get a set of coilovers and decent set of tires. This is coming from experience after driving a mate's car with coilovers then my car without coilovers. You get a lot of communication through the steering wheel after having coilovers but keep in mind the car will perform differently compared to stock.