What's up with the fan being powered by the power steering pump ?!!

[RockyTop]

What\'s up with the fan being powered by the power steering pump ?!!

I was told by my tech today that the ST-10's fan is powered by pressure from the power steering pump rather than being electric. For those who track their SRT-10, I sure hope the pump is a LOT better than the one that came stock on the RT-10 and GTS (or you get an underdrive pulley). THE PS pump is typically the first component to go on tracked cars. On the SRT-10, doesn't that also mean you will get rapid coolant temp rise to go along with your substantially decreased steering capability?

I guess you'll know about the imminent temp increase potential by the increased steering effort. I am told that the hydraulic powered fan can move more air, but the coupling of the fan to a part that has a long history of failure on the road courses seems unfortunate/not well thought out.

Can someone set me straight?

 

[GR8_ASP]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Question from a novice. How much of the time is the fan operating while tracking the car and if it does operate, is it required. It just does not seem that the fan would be necessary while at speed. Like I said a question from a novice so please don't shoot too hard.

 

[GTS Dean]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Hydraulic drive fans are more and more common these days. One positive aspect is that they significantly reduce a heavy demand on the electrical system. The steering pump is sapping power 100% of the time the engine is running, but the demand for hydraulic assist is usually very minor. This is an instance of making more efficient use of engine accessories.

 

[Jay Lopez]

Re: What\'s up with the fan being powered by the power steering pump ?!!

When we had our Tech meeting a few weeks ago, we discussed this topic. We were told not to change out the power steering fluid to something other than the factory fill (like Redline), as it might through off the hydraulics for the fan.

 

[Steve-Indy]

Re: What\'s up with the fan being powered by the power steering pump ?!!

I had asked this same question under a thread that Janni started...it does WORRY me slightly that we now have two major systems that have become "co-dependent" on one pump. So, if one is on the highway OR track and the power steering goes out...STOP before one fries one's V-10 ???

 

[GR8_ASP]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Back to my original comment. Does the fan run while on the highway or track? I would suspect that it would not run. But if it did it would be ineffective while at speeds sufficient for normal air flow through the radiator. If so increases in temperature do to pump or fan malfunction would occur at lower speeds when the threat of serious overheat is much lower and the time to respond is higher.

 

[Tom Sessions]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Rocky I don't know if you can be set straight but I'll try.This is the same set up that the comp coupe is running and they didn't have a P/S failure at thunder hill this weekend and these cars were pushed quite hard.The pullies on the SRT engine are different than the older engine The crank pulley and water pump pullies are smaller(under drive) the P/S pulley is now metal and not plastic so no more breaking of that.The largest benefit of this fan is it will pull a bunch of air at idle(sitting in traffic with the ac on) so this means a cooler engine.The way this fan workes is it will duty cycle a selnoid that tells the fan how fast to run based on engine temp and AC Hi side pressure.So this is a good system they didn't build any junk so don't worry be happy.
Are you straight or more confused now.

 

[Steve-Indy]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Thanks for the explanation, Tom.

 

[Rich Carlson]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Let me add to what Tom said. The old system is basically temperature/pressure controlled. The engine temp or A/C pressure reaches a certain temp or pressure and the fan is turned on. The temp or pressure drops to a certain point and the fan turns off. The new system still looks at the engine temp and A/C pressure but the PCM will ramp up, ramp down or hold the fan speed until the temp/pressure is under control. The neat part is that even if there is no request for the fan to be on, the fan is spinning at between 100 to 500 RPM when the engine is at idle. Not only does this keep oil flow moving thru the fan drive but it minimizes the deep thermal cycling because air is being drawing through the radiator at all times. The P/S cooler has also been moved to the front facia for max cooling. Hope this helps.

 

[RockyTop]

Re: What\'s up with the fan being powered by the power steering pump ?!!

Tom. Thank you for your explanation. What I think I am reading is that at high RPMs, the pulleys lessen the strain on the pump and they are made of stronger material. At low RPMs, the fan is more efficient due to its hydraulic operation. Nevertheless, as many PS pumps as have been lost on the track over the last 10+ years, I am concerned that the pump itself (which I am told looks identical to the one on the GTS and RT10) perhaps did not get the upgrade that it perhaps should have. As I am still driving on my orignal stock pump with no underdrive pulley, I have no personal foundation for concern (yet).

 

[shifter]

Re: What\'s up with the fan being powered by the power steering pump ?!!

The hydraulic fan isn't more efficient at idle speeds. It just has more power (torque) available to spin a more aggressive blade at higher speeds. For example, the hydraulic fans can put out about 1100 watts of power, whereas the electric fan is under 450 watts. Engine load is higher with the hydraulic fan, but not significantly on a high HP engine.

At idle, available electrical power is limited, and the electrical architecture of the vehicle limits the electric cooling fans' speed and torque.

The biggest issues with hydraulic systems include noise (cavitation of the pump, and air rush noise from pulling so much air), and leakage. It is of extreme importance that zero contaminents get into the system, as the fan motor has some pretty tight tollerances.

The Grand Cherokee has the same hydraulic system. It's well designed, and has a safety back-up. If you lose the fan motor, the Power steering will still operate since the circuits are seperated.

Lastly, about racing and fan usage, at speeds over 45 MPH or so, the spinning fan actually impedes airflow through the radiator. Most fans on street cars turn off at these speeds to reduce static pressure behind the radiator, encouraging more ram air to get through (hence the flaps on the Gen II fan shrouds). Fans are typically not needed for race cars, unless they spend time at idle or want to cool down before the next run. A/C performance and idle time (traffic) require fan input to keep temps under control on street cars.

 

[Steve-Indy]

Re: What\'s up with the fan being powered by the power steering pump ?!!

THANKS, shifter !!!