Bikespace

The entire front suspension is out right now, as part of the front-end rebuild project. All new stuff is going in. The only stock parts that remain will be the spindle, single-hole steering arms*, and (modified) hubs. So once it is put back together, I'll have a much better idea if what I felt is due to old parts, alignment (toe-out, too little caster, etc), or just the Borgeson ratio change.

Certainly the increased effort would be an improvement. I may have misspoke saying "twitchyness", as the very light effort is more of a concern. The car doesn't feel light, or darty, or all over the road, or any of the other ways you can describe it. Increased steering effort, and more caster probably would fix the issue, along with all new suspension and steering parts.

But I won't know until I reassemble everything.

* I wonder if it is cost-effective to drill a second set of holes in the current steering arms. I'll follow up on the Bump Steer thread.
https://www.corvetteforum.com/forums...p-steer-4.html

leigh1322

If you had the light weight Corvette or Borgeson box with the stock low caster alignment settings I would expect it to wander a little. Just not feel too stable or track straight.
4-6 Caster fixes most of that.
The higher "weight" at the steering wheel just lets you feel everything which is going on at the tire tread.
This is the main argument the manual steering "fans" have vs the stock C3 power steering. It's all about the "feel".

But it can be remedied....

73ls1

I feel my Borgeson box has a light feel to it . I would like to have it rebuilt. What is the turnaround on the rebuild? Thanks for the tip.

augiedoggy

I believe there a line pressure restrictor you can use to help with this also?

leigh1322

Yes the stock C3 or Borgeson "feel" is a little bit too light for a sports car.

IIRC their turnaround was a couple weeks.

I have talked to engineers before about restricting the flow and/or pressure, in the past, to tune the system. They recommend against it. That just restricts the max power level of the power assist at max load. The flow rate and the max pressure are set for high max effort steering input. The actual pressure at the assist ram/piston changes all the time, from zero to 1300psi, due to the control valve. At idle, there is a lot of volume of fluid moving thru the hoses, but at zero pressure. The system supplies increased (or decreased) pressure according to what is called for by the C3 control valve or the rack-pinion / Borgeson torsion bar control valve. The control valve actually restricts the flow down, (not the reverse), causing pressure to build quickly. The faster you move the steering wheel, the more caster you have, the fatter your tires are, the slower your parking speeds are, then the more pressure the system "uses/supplies". Doing it this way means the system is in low-power-mode 99% of the time.

Restricting the flow or the pressure would restrict the max assist available and will cause it "run out of assist force" in a strong/sudden turn situation and would suddenly get "hard" with no power. Systems that do that either need more flow, or more pressure capability. It usually shows up in the parking lot, or a fast lock-to-lock transition like a slalom type manuever. There is both a flow rate valve and a max pressure control spring in the OEM pump. Usually the stock OEM settings here are just fine. There are two typical flow rate valves and two common pressure settings. A stock C3 uses a lower pressure pump (870#) than typical GM (1350#).The higher flow rate valve is used in certain applications. Both of these are easily increased if you find yourself running out of assist at max effort. But changing to the lower rated ones has almost no effect at normal driving levels, just max-effort ones.

PS systems that "run out of assist" don't just revert to manual effort level, they get extremely difficult to turn at the wheel. And the sudden onset is frightening. I almost drove into oncoming traffic once because of this, the car just wouldn't turn (blew the belt). In normal driving, you are not "using" that much pressure assist. Whatever the force level it is that pushes the "spring" in the control valve or "twists the torsion bar" spring in the Borgeson, is the amount of force/feedback you will actually "feel" at the wheel. (That is the spring you want to change to change the "feel"). The pressure assist supplies all the rest. Take off the PS pump belt and try to drive the car. It is crazy stiff. You now have to use steering wheel effort to push the hydraulic fluid thru the system, and thru the control valve, in reverse, since it is still plumbed up, and it is leveraged against you. You can barely move it.

The max pressure spring is in the pump. When the pump maxes out the flow at the flow orifice at the pump outlet, the spring pops-off and it recycles into the pump. This is most likely to occur at higher rpms since it is a constant volume vane pump. If you get hard steering in the parking lot, the first thing to try is a larger flow orifice, since there is very little flow at low rpms. (At those speeds you are at low flow and low pressure). That could help the control valve build pressure quicker, and the pump to supply more power. The same thing is true during a slalom run. You need more flow. I am sure you haven't hit the psi spring yet. A C3 probably never needs the 1350# spring. It is a light car and just does not need that much power. Even if you have it, it is OK, cause it will just never go that high.

Problems with overheating, blowing hoses, etc, are usually problems with the control valve. Building too much pressure (and heat) too much and too often.

OldCarBum

So this might be a dumb question, but what if you moved the tie rod ends from the inner holes (power steering, quick position) on the steering knuckle to the outer holes (manual position) on the steering knuckles?
I would have to ask again, because I was talking with an old vintage race car guy and I think he said they used the borgenson box on their race cars and moved the tie rods to the outer holes.

leigh1322

Very good question! Took some research to figure it out.
The C3 stock box is a 16:1 ratio but the overall ratio has two settings with the two holes in the spindle steering arm:
That would be 20.2:1 on the standard or manual or the outer hole and 17.6:1 on the inner or fast or PS mode

When you change to the Borgeson box with it's 21% faster 12.7 ratio, both steering arm settings also get 21% faster.
Those settings would now be 16.0:1 or 13.97:1 overall.
For comparison a 2015 Z06 has a 17:1 steering ratio.

So the conclusion is the Borgeson box is probably best used in the standard/outer hole on a C3 for a 16:1 overall ratio. Just like the race car guys did. The inner hole would yield an even faster ratio, and may be useful in low speed autocrosses, but may be too fast and too sensitive and not ideal at high speed.

TurnOne does offer even faster gear ratios, but I will stick with the standard 12.7:1 Borgeson ratio, and the outer spindle arm hole. I can always experiment with the inner hole.

Steering wheel turns lock-to-lock is spec'd as: 3.4 or 2.92 (on fast)
With a Borgeson box turns would be: 2.7 or 2.3 (on fast)
2017 Z06: 2.5 turns

So while it would be nice to speed it up some, I do not want it to be "too fast"
The standard 3.4 turns feels pretty slow compared to newer cars.

wheresmyhorsepower

FWIW the 10:1 ratio yields 2 turns lock to lock on my car. With the 12.7 ratio it was ~2.5 turns. My tires rub before hitting any steering stops, hence the slightly different numbers.

leigh1322

HOW TO TUNE A POWER STEEERING SYSTEM

I have heard from a couple of guys on how to tune the "feel" of the Borgeson. The normal being "too light"

Some of you guys are running Type 1 pumps, some Type 2, some a Hydraboost, and some a rack-n-pinion. so there are many variables.

Here are some remarks from the Pro-Touring Forum, from the head engineer for Hydraboost, regarding a power steering that is too "light" but the Hydraboost brakes are fine. With all of the above being said, the driver essentially has five basic choices:

1) Detune the PS pump GPM further still with an even smaller jet / orifice size
2) Replace the steering gear with one that has a stiffer torsion bar (the input shaft) to increase steering effort
3) Blow off the volumes / pressures available to only the steering gear (the Heidts PS101 valve)
4) Increase the caster which will require more effort to steer from center
5) Live with it

Unfortunately in a hydraboost brake situation several of those choices also affect the brakes. 2,3 & 4 do not and only affect the steering.

He also mentioned:"We coach customers daily that 2.2-2.6 GPM and 1350-1450 PSI max pressure relief is our general target."
(These are basically OEM specs). And many aftermarket parts have way too much flow.

"A flow of 2.0 GPM +/- typically results in a no-load gauge reading of 100-150 PSI depending upon the steering gear design."
This is where the psi remains for 98% of the time. And when you change the flow restriction larger for more flow, this no-load pressure also increases, giving you more assist/more power/less feel. If the no-load psi is too high, you will also have over-heating problems. Max pressure usually only occurs when you hold the system against it's stops. This "no-load" pressure is far more important the rest of the time.

To tune the flow restriction here is a procedure: (like if you have too light of a feel)
KRC Power Steering says:
Too much flow results in overly-sensitive steering feel.
The larger orifice provides maximum steering assistance while the smaller provides maximum steering feel. If it’s too heavy, increase the orifice diameter; if too light reduce it."

So how do you achieve optimum steering feel? According to KRC’s Ken Roper you reduce the size of flow valve orifice until you experience pump catch. Characterized by a momentary loss of hydraulic assistance, pump catch can be induced by steering the vehicle in one direction then swiftly changing to the other direction—as oval track and road racers do. The quick change of direction increases the pump flow requirements and the momentary deficiency is caused by a sudden lack of flow of hydraulic fluid. When pump catch is encountered you can increase the orifice by one or two sizes, which will eliminate it and cultivate a better feel. As a result, the steering will be accurate, responsive, and without any tight spots.

wheresmyhorsepower

This generally aligns with my experience as well, although I'll clarify that there's a difference between over-sensitive "twitchy" steering and light/numb steering feel. Changing the orifice (flow rate) affects how reactive the steering feels but has minimal impact on feel/feedback.

At this point I've tried options 1, 2, 4, 5. I don't have hydraboost. Also don't know anything about option 3, assuming it's a bypass valve?


In chronological order:

Option 4: Still felt numb and sloppy even with 8 degrees of caster. This much caster is detrimental on tight courses with how much it unloads the inside rear wheel coming out of a turn. Plus it caused tire clearance issues with moving the wheels rearward in the wheel well.

Option 1: My Turn One pump out of the box flows about 2.5 gpm. Swapping out the orifice for one that flowed 2.0 gpm helped the feel a little, but not much. It kind of made steering a tad bit harder, but still numb if that makes sense. It also "caught" on really tight courses so further restricting the flow wasn't an option. Overall was a minor improvement but wound up drilling out the orifice to about 2.25 gpm so it wouldn't catch. At that point, the already minor improvement was basically null.

Option 5: Had accepted my fate for a while.

Option 2: By far the most significant improvement. This is what made the steering what it should be.

leigh1322

Terrific Feedback.
That was pretty much my experience as well.
The Torsion Bar (#2) is the one item that made the most difference!

WESCH

Hi
I am presently a manual steering driver on my 68 BB, mainly because of the light steering feel of the Borgeson box reports.
If I buy a new Borgeson kit, sending it to Turn-One, what will they have to do in addition to change the torsion bar ?
Meaning, is a rebuild/teardown required ? Is a re-valve necessary ?
I am planning to run it on electric hydropump.
Sorry for the possibly dump questions .
​​​​​​​Brgds. Günther

OldCarBum

You can run a Borgeson steering box without any modifications and most people do.
Follow the instruction instructions and be done.
Leigh and the others in this thread are tailoring their Borgeson boxes and their complete steering systems to meet their specific needs for how they want their steering to respond.
Yes you can upgrade and modify the box to improve the steering of your car, but for the average person, it isn’t necessary.
It is a very interesting thread and I’m following along even though I have manual steering and don’t “plan” to change.

leigh1322

Yes it means a tear down/rebuild ($400) + revalve ($300)

Their standard 39 in-lb torsion bar would have about 5.2# of pressure measured at the wheel rim.
I am currently guessing that stock C2/C3 PS is half of that.

I am currently collecting some data on steering wheel force. If you had a way of measure your manual steer car at the steering wheel rim and sending it to me that would be great.

WESCH

Hi

But steering wheel force is highly depending on car speed and tire size and ....., isn't it ?
When do I measure ?
In stand still situation, I nearly cannot turn the steering wheel. Need to slighly move the car while steering .

Rgds

TommyFox

I installed mine last year and am well pleased with it the way it is over stock. Not sure why one would want a heavier feel on a street car but could see on a track car for the feel of stability.

leigh1322

The increased or heavier feel gives you much better information to your fingertips as to what the tires are doing.
But like most things, if you go to far, it is just too much work. (Like manual steering while still).

As you increase speed in a corner, this 5# ? "force" lets you feel if the tires are responding crisply when you turn the wheel, or not.

All race car drivers "at the limit" saw the wheel back n forth slightly. As the tires start to "slide" it happens at the rear of the tread first, and the "force" at the steering wheel lessens just slightly, (gets lighter). This effect gives you some warning that you are right at, and maybe just slightly over, the limit of tire adhesion. It is your "warning" not to push any harder. It also enables a race driver to be able to "hold it" right at the limit. The better you can feel this, the faster you can drive.

When the steering wheel is very light you can not "feel" a thing going on at the tires.

This feedback also gives a driver great confidence, and makes driving very comfortable and enjoyable, when driving below the limit. You can tell you are not "over-cooking" it.
I enjoy the crispness and feedback.

Bikespace

For a good example of what it looks like when you are doing it just right, here's Ayrton Senna driving a Honda NSX, in loafers.


To GM's credit, the original power-assist system gives the driver some of that feel through the manual box, and only "assists" when needed. In theory, anyway. I'm glad to see there's now a proven Borgeson option that can give me a manual steering feel, without making parking lots a chore.

leigh1322

I am doing some research, and measuring, on what steering wheel force feels "good"

So far:
2# at the 7 inch rim is the old style "little finger" PS.
Many std GM cars are around 3#.
Some Hi Perf cars are in the 4# range.
A few very high perf cars are in the 5# range.
6# and up seems to be too much and too stiff.
I have 2 cars that take 10# to turn with the engine off. That's way too stiff.

What I need now is three C3's to measure up, and see where they fall on the chart, so we know where we stand now.

• A manual steer C3.
• A stock PS one.
• And a Borgeson one.

Anyone want to help document this for the good of the group?

I could show you how, send you my gauge, we could get together, etc.

Bikespace

I am down for any science. I have a manual steering car available right now.

Can you post a picture of your gauge? I might already have something that works.