SivaSuryaKshatriya
SivaSuryaKshatriya New Reader
3/19/18 2:25 p.m.

Hi all,

After having driven a FRS for a few years, I grew bored of the lack of power and ended up getting a 2008 Corvette Z06. While my need for additional power has been more than sated, I now find myself missing the absolute perfect steering feel of the FRS. It was highly responsive, communicative and inspired a lot of confidence, allowing me to easily push the car to the limits in corners without exceeding them. When I put 18x9.5 wheels with 255's on them, the steering became wonderfully weighted and was even more Go-kart like.

The Corvette steering, while being very precise, is a bit too light for my taste. There's no feedback from the wheel. In addition, I often find myself banging my hands against my knees when taking tight corners on the track (I did not have this issue in the FRS, which has a 12:1 steering ratio as opposed to the Z06's 17:1 ratio). I know that putting solid bushings on the steering rack will increase the feedback, but that won't fix the 'light' feel or high steering ratio.

 

My questions:

1) I found a bolt-in steering pump with adjustable flow (link is here). Basically, I can replace the Z06's stock unit with this one, which allows me to increase or decrease the flow rate to the pump, affecting how much assistance it gives in turning the wheels. The question is, will lowering the flow rate increase the amount of feedback from the steering wheel? Or does it simply make steering heavier with no benefit towards feedback and steering feel?

2) Is there anyway I can drop in a rack with a lower ratio? I called Sweet MFG and Flaming River, and neither could modify or build a rack with custom ratios. I really want something that's around the FRS ratio at 12:1

The Corvette forum is mostly unhelpful, as most responses are simply a permutation of "it's not a Lotus, deal with it." However; I'm not asking for a Lotus, and this isn't an issue of weight, as I've driven heavier cars such as the BMW 128i that felt better.

Thanks.

johnnie
johnnie Reader
3/19/18 2:42 p.m.

Could more caster in an alignment help?

stafford1500
stafford1500 GRM+ Memberand HalfDork
3/19/18 2:46 p.m.

There are some inline steering quickeners (changes ratio thru a planetary gear set). That should get you closer to the ratio you want, but I only recall seeing them in 2:1 ratios. Apparently Howe has one at 1.5:1 which would put you right at the ratio you want. Not sure if the feel would be any better.

steering quickeners

Stefan
Stefan GRM+ Memberand MegaDork
3/19/18 2:54 p.m.

Quaiffe makes steering rack ratio improvement kits for many cars, perhaps contacting them to see if they could make something for you?

Any chance the rack is compatible with any other cars in the GM lineup?  Perhaps the GTO/Camaro/Solstic/Sky?

Stefan
Stefan GRM+ Memberand MegaDork
3/19/18 2:59 p.m.
stafford1500 said:

There are some inline steering quickeners (changes ratio thru a planetary gear set). That should get you closer to the ratio you want, but I only recall seeing them in 2:1 ratios. Apparently Howe has one at 1.5:1 which would put you right at the ratio you want. Not sure if the feel would be any better.

steering quickeners

They can cause some additional slop as they wear and finding room sometimes can be a little tricky.  It might be a good option though.

If you can get the dimensions of the stock rack (or grab a spare to measure) and then grab some similar sized racks from the local salvage yard, etc. you might find one with better ratio that can be made to work.

Caster is a big piece in steering feel, there's also the ackerman, the wheel offset and tire width that play into this as well.  Going from a smaller car to a larger one with wider and heavier tires will hurt feel and response somewhat.

SivaSuryaKshatriya
SivaSuryaKshatriya New Reader
3/19/18 5:25 p.m.

Johnnie - actually, haven't tried more caster. That's a good idea.

stafford1500 - didn't know that such a thing existed! Thank you very much. I'm gonna see if they make a custom ratio at around 1.3:1

Stefan - Gonna look into Quaiffe, thanks for that. Regarding compatible racks, I know the '09 Z06 has a variable ratio rack that goes from 17:1 on center to 14:1. However, despite the mechanical changes being purely limited to the steering rack itself, which would be a direct bolt-in, the ECU needs to be reprogrammed with an '09 map, otherwise the active handling on the car may have issues (no info on whether this would happen or not, but it's a theory).

Stefan
Stefan GRM+ Memberand MegaDork
3/19/18 6:07 p.m.

In reply to SivaSuryaKshatriya :

Sounds like the 09 rack might be worth looking into, if you know someone who knows them and is willing to talk to you about whether the 09 software would have any issues on your 08 with the 09 Z06 rack.

SivaSuryaKshatriya
SivaSuryaKshatriya New Reader
3/19/18 6:23 p.m.

Finding out 100% whether it'll have issues or not will be tricky, but at this point that would make my life a lot easier if I could just retrofit.

Does anyone have comments on first question about the steering pump with variable flow? Any idea if reducing the flow will reduce the assistance (it should) and whether that will increase steering feedback, or if it just makes it feel heavier?

SivaSuryaKshatriya
SivaSuryaKshatriya New Reader
3/20/18 4:35 a.m.

Looks like the C5 and C6 use a MagnaSteer rack. A MagnaSteer is basically an earlier iteration of a variable effort steering rack, using a magnetic field to manipulate the amount of hydraulic pressure going through the pump. At high speeds it uses less assist, and at lower parking lot speeds it uses more. Anyway, the MagnaSteer is programmed to the 2008 steering rack ratio of 17:1. There's a different MagnaSteer program for the 2009 variable ratio rack, but that cannot be programmed into the 2008 even with a tech 2 GM tool.

Any future C6Z owners looking at this, you're better off trying a Turn-One pump with lower flow. Or just buying a FRS and turbo'ing it.

jfryjfry
jfryjfry HalfDork
3/20/18 9:08 a.m.

I know a guy who is a genius and owns a power steering company.  I'll ask him about this!

from one c6z owner to another!  Haha

SivaSuryaKshatriya
SivaSuryaKshatriya New Reader
3/20/18 1:39 p.m.

In reply to jfryjfry :

Thanks! It's appreciated :)

Mad_Ratel
Mad_Ratel Dork
3/20/18 3:47 p.m.

So i'd suggest a slightly smaller aftermarket steeringwheel.

it'll increase steering effort, while also giving some clearance for your knees...

jfryjfry
jfryjfry HalfDork
3/20/18 10:30 p.m.

Here is his response:

Changing the pressure and flow of the pump can have a small effect on steering feel but mostly it’s a mod in the rack itself. Is he saying it steers to light or the ratio is off? I always am telling customers that the pump and rack are just 2 links in the chain of steering. Front end geometry is a big part of it too. The other part of what we do relates to steering fade during competition due to oil heat. Give me a buzz or have him call.

Allan Padelford Owner, Steering Technology Group www.steertechgrp.com 818-768-0371

Vigo
Vigo UltimaDork
3/20/18 11:11 p.m.

I think all of the above is probably the best answer. I.e. smaller steering wheel, reduce pump flow, stiffen rack mounting.  If you want to get serious about the steering ratio, i looked at the c6 front spindle and it looks like there is room to redrill the tie rod hole farther inboard which would quicken the effective steering ratio. Most people are chicken about such suggestions, but maybe you're not, so there it is! May still have software problems as far as stability control no longer seeing right correlation between steering angle and lateral acceleration yadda yadda.

I bought some spindles with much shorter 'steering arms' which will quicken the steering ratio of my b250 dodge van. They're from a Dakota and require some modifications. If i want it faster i could always get one of my welder friends to lengthen my pitman arm.cheeky

freetors
freetors Reader
3/21/18 7:48 p.m.

Steering feel is mostly going to be dominated by steering geometry, tire characteristics, and compliance or stiffness of all the steering parts and their mounts. As has been said previously, decreasing the steering assist and changing rack ratio will have little effect on steering feel, just like removing the vacuum assistance on your brakes doesn't improve braking feel, it only requires you to press the pedal much harder for the same braking effect.

Probably the easiest thing you could do is max out your caster to weight the steering and get a stronger return to center.

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