LS Swap: GM P-pump to Toyota Steering Box - Flow Control Fitting (1 Viewer)

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I've seen this mentioned in the Trail Tailor's DINGO build. But I can't get much explanation. The GM P-Pump has a relief valve at like 1,460psi. The solution discussed reduces flow, but I don't know how that would reduce pressure in the steering box. I'm just a bit confused.



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SF23 - Flow Control Fitting with -6AN for P-Pump
Flow Control Fitting with -6AN for Saginaw
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SF27 - Flow Control Fitting with -8AN for P-Pump
Flow Control Fitting with -8AN for Saginaw
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MANUCHAO

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The solution discussed reduces flow, but I don't know how that would reduce pressure in the steering box.
The way I understand it.......at higher RPM's (hwy speeds) like 2k and 3k rpm's the pressure is much too high for the toyota box...
It can handle it, but with time the seals can't hold.....and premature failure happens....

I run one, on my set up, and it sure makes a difference specially at hwy speeds....
 
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TRAIL TAILOR

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The way I understand it.......at higher RPM's (hwy speeds) like 2k and 3k rpm's the pressure is much too high for the toyota box...
It can handle it, but with time the seals can't hold.....and premature failure happens....

I run one, on my set up, and it sure makes a difference specially at hwy speeds....

Also at full lock right or left the P-Pump will load up the box and make a weak hose leak/rupture.
 

MANUCHAO

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What psi is the stock fj60 and fj80 pump
For the 80 series i believe the pressure is 1351 PSI and at engine speeds between 1k rpm and 3k rpm the fluid pressure differential should be 71 PSI or less. Steering effort should be at 73 in.lb....

It would be interesting to know what the specs are for a GM steering system. I have read it can be from 1300 psi up to 1600 depending on vehicle size and weight.... I also wonder if the fluid pressure stays the same between 1k and 3k rpm's....
My rig steering (at hwy speeds) used to be hyper sensitive before this mod... (Yes caster is w/in spec) after the mod the steering effort is a bit more but sure feels much much better and does not dart as it used to

My deal is that the flow restrictor is not a pressure reducer. It actually just reduces assist. If you want to reduce the peak pressure, there are kits for that. This just ain't it.
The flow control fitting you reference above is not a pressure reducer by design, but it is a restriction orifice, a single stage restriction orifice at that...used as a flow control instrument device whose primary function to provide a restriction to the flow so that a controlled or restricted flow is achieved.

From the webs....
" restriction orifice is a device used for measuring volumetric flow rate in a pipe. Orifice plate works based on Bernoulli's principle. Bernoulli's equation states that pressure drop across the restriction orifice is directly proportional to the volumetric flow rate passing through the orifice plate. "
 
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I hear all the validations of the difference between flow and pressure. Nobody has still answered the question why there is a recommendation for reducing the flow as a solution to protect against excessive pressure. Technically the reducer will increase pressure on the pump side (which I guess is relieved by the relief valve). Is it really too much flow that's the problem in the steering box. It has the ability to relieve also, but perhaps it has a finite flow capacity it can relieve.
 

MANUCHAO

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Nobody has still answered the question why there is a recommendation for reducing the flow as a solution to protect against excessive pressure.
again, from the flow control fitting you posted.... it is to control flow, thus reducing pressure, thus having better feel for the road, or better control of the steering at higher speeds... at least that is what is sold/advertised under(flow control).
I also have read this was aimed at folks that frequent race tracks..

Other literature states the effect it has on reduction of heat on the fluid, and gain of HP, but I dont care to research if true or not.
TT mentioned the Loading up the box at full lock, which would find the weakest link past the fitting...
For me the end result (better feel / control at speed) is what was important...
At $20 if it helps the longevity of the box...that makes it a no brainer....


BTW you mentioned
If you want to reduce the peak pressure, there are kits for that.
Care to share what kits ?

megolfer posted the Borgeson kit, and I see its sold as a pressure reducer, but under the description it clearly states it is a flow reducer......
Any Orifice does this.... restricts flow and reduces pressure

It has the ability to relieve also, but perhaps it has a finite flow capacity it can relieve.
Perhaps......
GM steering pumps are cheaper to replace than toyota steering boxes...
 

MANUCHAO

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if you constrict flow you actually increase pressure in the system.
think if it as putting your thumb over the end of a garden hose
You do increase pressure on the pump side, not on the box side.....
Putting you thumb on the hose creates pressure on the hose side cause you restrict flow. past your thumb you reduce flow, thus reduce pressure down to whatever your PSIA is....
 

MANUCHAO

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Putting thumb on hose increases pressure on both sides of the hose.

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Going by your previous post....
Pressure is lower once it goes past your thumb (that's restriction) the pressure coming out of the hose is lower, but at a higher speed (cause of kinetic energy).
 
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Finally found something instructive:


There's a pressure drop across the nozzle. Plan and simple.
 
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Went ahead and installed the flow control fitting, as recommended. The highway boost is definitely more appropriate now. I appreciate the pioneers that have learned the hard way on this.
 

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