Autocrossing and power steering

[Jovan Ceklaj]

It seems that regardless of what car I drive, going through a tight chicane will get the stock power steering system to go out.  I'm just wondering if anyone knows the cause of this and what kind of potential fixes there are.  Note also that I'm not talking about how power steering cuts out at high RPM on a DSM, I'm talking about cranking the steering one way, then the other, then back again and noticing that the power assist cut out.  It's almost put me in the rhubarb once at an autocross and has definetly lost me some time.

[Martin Raska]

Flow control since the pump is driven off engine speed usually I think.  On the DSMs I believe it is just ball-spring valve and you can shim the spring (or remove it?) such that it will never close.  You might encounter an undesirable pressure condition though because this wasn't put there for no reason of course.  Could go manual rack, or electric power steering pump as well.

[Jovan Ceklaj]

Definetly makes sense and I'd be inclined to agree.  Does anyone happen to know the reason for doing that?  I would assume that when you turn hard, you get spikes in pressure.

[Ryan Lore]

How hot is the fluid when you autocross, I wonder if it's boiling like brake fluid can. I've been burnt by the fluid reservoir on at talon before. You guys are the brains you should be telling us the answer.

[Martin Raska]

Good question Ryan.  It would be neat to find some time to put some thermocouples in series there get an idea, but I think going with a manual rack would be time better spent.

On a side note I'd like to take a BMW with their newest active steering for a autocross.  It would be interesting.  It's awesome to drive around the city with a combination of roads and parking lots, but having that huge variation of speeds in a race might change my opinion of them.

[KevinBuckham]

I use Mobil1 Synthetic fluid and I routinely boil it out.  I really should add a cooler for the power steering fluid as recommended to me by Ryan Lore about 3 years ago.  

Hamish Sandwith (local Autoxer and handy DSMer) borrowed some hydraulic gauges and ended up analyzing the power steering cut on a 1G.  He now uses a different method to "shim" the pump than the 1G VFAQ.  

I honestly don't remember the details, but I believe that he is basically increasing flow without affecting the high pressure cut off point.  Some shimming techniques increase the cut off point forcing the pump to run hard continuously.  We really just want more flow and the pump to turn off at some point.

Since I've driven his car on a tight autox (much tighter than the ones at Boundary Bay) I can tell you that his 1G does not have power steering cut out that I could find and he also doesn't seem to boil out fluid like me.  

My 2G has never exhibited power steering cut after Lowell shimmed it.  Hamish's favourite course designs have slalom stretches that will make stock power-steering 1G Talons a "handful".  (Picture heading 45 degrees into concrete at 50km/h with no power steering.)

Ryan H's 1G still doesn't have pump shimmed and it can be scarey on these tight "miata" courses on about the third consecutive turn.

[Martin Raska]

I didn't autocross this year at all, but I really should do something about it before going back out.  It would change my driving style pretty considerably especially at the beginning of some courses, because I'd want to get out of first gear asap to reduce the revs.