Hydraulic cooling fan.. why?

Discussion in 'SRT Engineering Q/A Area' started by rukcus, Feb 1, 2013.

  1. rukcus

    rukcus Viper Owner

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    Why did the engineers feel it was better to have a Hydraulic cooling fan in the gen 3 than an electric fan? Wouldn't a hydraulic cooling fan put more stress on the P/S pump which in turn adds to parasitic power loss ?
     
  2. Viper Specialty

    Viper Specialty Viper Owner

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    Not at all. The Power Steering system is always pumping, using it to drive a fan actually reduces overall losses, as the hydraulic system is considerably more efficient than an electric one. Even an electric fan is parasitic by nature- just through the alternator instead. Power is not free, no matter where it is sourced from. A hydraulic fan motor is a mechanical device, meaning that there are no energy state changes occurring on a large scale in a hydraulic motor, where an electric motor actually takes energy from mechanical, to electrical, and then back to mechanical during use, creating losses each time.

    That being said, the hydraulic fan was utilized because hydraulic motors size for size are capable of considerably more output power than an electric counterpart. The hydraulic fan is also considerably higher torque, allowing a more aggressive fan pitch to be used, greatly increasing airflow. When couple this fact along with utilizing a PWM controlled continuously variable speed fan like the Gen-3, it allows fan temp targets to be achieved on a near constant basis. This reduces the cyclic nature of engine temperatures, in turn keeping the engine more efficient at all times due to overall temp stability.
     
  3. ViperGTS

    ViperGTS Enthusiast

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    theory: above.

    reality: lots of problems with the PS and fan in the Gen-3s...:eater:
     
  4. Jog

    Jog Viper Owner

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    This was direct result of the merger between Chrysler and Mercedes Benz. Chrysler decided to try something different with the Gen III and went took some engineering queues from Benz. Though Viper Speciality is correct in his in reasoning for the hydraulic fan, the engineers at Chrysler quickly realized that the hydraulic fan did not specifically work well with Viper due to it's uniqueness as a sports car. They quickly changed back to the electric fan during construction of the Gen IV model.....
     
  5. rukcus

    rukcus Viper Owner

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    I do understand your explanation although I am inclined to say that a P/S pump takes much more power to turn than an alternator. I just hate to see that my coolant temp rise so much after I shut off my car. I would have loved for them to allow the fan to keep operating even after the motor is turned off even for a short period of time like most other modern vehicles.
     
  6. Viper Specialty

    Viper Specialty Viper Owner

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    Incorrect.

    There was a manufacturing mistake [2003 Recall], as well as an informational mistake leading to mixing incorrect fluids, contamination, and subsequent failures. The system is unfiltered, and very susceptible to cross contamination and recurring failures due to incomplete cleaning. I have yet to see ONE legitimate fan failure that was not the result of someone up the line causing it inadvertently. There have been ZERO Gen-3 fan or power steering pump failures in WNY that I know of, with the exception of a bad fitting/leak.
     
  7. Viper Specialty

    Viper Specialty Viper Owner

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    Chrysler went back to an electric fan due to cost cutting measures. It is much cheaper, end of story. The electric fan DOES NOT work as well, I am not sure where you heard that it had anything to do with the Viper application specifically as sports car. I have yet to see a properly working Gen-3 overheat. I have seen plenty of hot-running Gen-1, 2 and 4 cars however. There is a reason, and you don't have to look any further than a Gen-3 sitting next to a Gen-4 with the fans on Hi to realize which one is substantially superior.
     
  8. Viper Specialty

    Viper Specialty Viper Owner

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    Yes, the PS pump takes more energy to turn- but it is already turning regardless, even without the hydraulic fan. If you want to argue the benefits of an electric PS system that is a valid argument, but when you have a mechanical system, maximizing its efficiency vs comparing it to a system that is not implemented, that is not. [You didn't intend to, but you did inadvertently]

    Even with the fan running after shutdown, heat soak is inevitable. It does not cause damage unless extreme or with contributing factors.
     
  9. rukcus

    rukcus Viper Owner

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    So in the pursuit of performance and reliability why don't we see upgrade kits for p/s cooling conversion fans on any gen 1,2,4 or other performance oriented vehicle. People blow tons of money for mods. I am going to have to explore this potential market ;)
     
  10. Viper Specialty

    Viper Specialty Viper Owner

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    Easier said than done. It is a special fan shroud and blade arrangement, so you would have to fit an OE fan and shroud. Assuming you could make it fit, it is a rather specialized routing of hydraulic lines, and a twin return reservoir. Again, a pain to implement, but doable. Lastly, the most difficult part is control. You need an ECU with a fully configurable PWM output. This is something that the better ECU's certainly offer, but all in all, it is a complicated retrofit, and pretty expensive overall- its a lot of pricey parts.

    All that said, I absolutely have considered doing this conversion. A Gen-4 with an aftermarket ECU would be the easiest addition by far, but I suspect that an adapter plate could allow fitment into a Gen-1 or Gen-2 without a ton of difficulty, provided the car had an aftermarket ECU to control it.
     
  11. rukcus

    rukcus Viper Owner

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    I still haven't found any resources on the pros and cons of hydraulic cooling except when converting from clutch fan to hydraulic in industrial applications. I hope the Viper engineers can chime in on this.
     
  12. Viper Specialty

    Viper Specialty Viper Owner

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    I could have sworn that I answered that exact question in post number two, and replied to every single comment on this thread otherwise. If you have a specific question, ask it- I would be more than happy to answer it. I realize you are relatively new around here, but I assure you that there is no better source for these oddball questions than who you are already talking to. There is a reason that we take on the projects that we do after all, specialty application automotive engineering and manufacturing is kind of our thing. :)
     
    Last edited: Feb 3, 2013
  13. Allan

    Allan Viper Owner

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    Dan, any news or progress on an improved pressure line/fitting? ....sorry to hi-jack the thread, but this is actually the only real concern of us gen III guys for the p/s and fan system.
     
  14. Viper Specialty

    Viper Specialty Viper Owner

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    Alan-

    Sorry, not yet. I have a full plate with what I am trying to get finished by spring- once these other projects are finished, I will definitely be back on it.
     
  15. Allan

    Allan Viper Owner

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    Thanks! The entire gen III population is ready for a cure to this weak spot.
     
  16. Garron

    Garron Viper Owner

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    How many pressure lines have blown out on you?
     
  17. Viper Specialty

    Viper Specialty Viper Owner

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    Actual blow outs [ruptures] are very, very rare. We are talking about the seeping/separating pump fitting that causes you to replace the whole line because you cant get the damn thing off reasonably, or it is damaged during an unintentional separation. The single O-Ring in it goes bad over time from dust & vibration, and the newer versions of this fitting have an additional design problem making them prone to coming apart. Its a 5 cent problem with a $300 price tag. We were working on an improved replacement fitting and a line exchange program so we can get the old fittings off and out and not lose the lines.
     
    Last edited: Feb 3, 2013
  18. Allan

    Allan Viper Owner

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    Three. ......over 50,000 miles though. the last 28,000 have been track only plus commuting. (I don't have a trailer) I have driven home from the track twice with no power steering after blowing the line/fitting. Totally sucks, and the mess is terrible to clean up.
     
  19. Viper Specialty

    Viper Specialty Viper Owner

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    Just to build on what Allan is talking about: "blow outs" refers to the line and fitting separating, not the hose actually rupturing. This is a more recent problem as Dodge changed suppliers of their line fittings, and this issue was created during the transition. The old [and new versions] seep/leak over time, but only the new one is prone to separation problems.
     
  20. Allan

    Allan Viper Owner

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    yes.............the actual line is ok, I got 2 of those new jacked-up connectors in a row without realizing what was up.
     
  21. Garron

    Garron Viper Owner

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    The "fitting" part number does not show an update, 52088914AA still an "AA". It would be nice to have a replacement, I have noticed slow leaks over time. It is a pain to change a perfectly good line because you can't replace the fitting.

    WOW three connectors, you sure everything else is ok and you don't have a restriction somewhere?
     
  22. rukcus

    rukcus Viper Owner

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    Oh my bad I didn't know you were one of the engineers this is my first time asking in this specific forum. I kept on looking on the internet because I like to see sources and read up on it.

    I have spent my whole life in engine rebuilding so if there is something I don't know about, I would like to get details. I like to research the exact benefits long term and short term. As well as the cons. Cooling efficiencies graphs, estimations you know.
     
  23. Viper Specialty

    Viper Specialty Viper Owner

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    Haha, I am an engineer, but not one of "those" engineers... though we all work on the same products at the end of the day. ;)

    Hydraulic cooling systems are nothing out of the ordinary. Nearly ALL heavy equipment uses them, as well as a number of cars. You will generally find them in vehicles that have high power per cooling system area and limited space, and especially on stationary equipment [heavy machinery], and towing vehicles. While Hydraulic Fans in heavy equipment are a near given since they are generally mostly hydraulic in nature already, the power steering version in the automotive market is an adaption of sorts. The power steering system is an already in-place hydraulic system that is parasitic by default, and offers an excellent drive source. Increasing efficiency of an already in-place system is a no-brainer. If a system is to use power anyway, it may as well be used to do something constructive. An electric fan will need to tax the alternator when it operates as well- all systems are parasitic, and nothing is free in this regard.

    The primary benefits are simple: a hydraulic fan motor per size and weight is considerably more powerful than an electric counterpart of equal size and weight. This equals better cooling capability per cubic of space and mass. This is especially important when stationary, with limited front airflow area, a large cooling demand and little space to accomplish the cooling... and without a weight penalty associated with a larger electric fan or multiple electric fans needed to do the same job. In other words, ideal for an application like a sports car.

    The other smaller benefits are:
    -Reduced weight of wiring harness components with fewer failure points. High amperage fan wiring is not light, and the relays are not the most reliable.
    -Target temp system due to continuously variable speed control keeps engine temps more stable.
    -Ability to vary duty cycle to low levels reduces underhood temps and heat soak by promoting light flow at all times.
    -Feature above can also be used to stabilize intercooler/cooler temps when full demand for engine cooling is not needed.
    -When system is "off", there is next to zero additional cooling system parasitic loss, allowing for additional acceleration if system is cut by throttle position. [Same CAN be done with alternators, but it is not always advisable, as the ignition system prefers higher voltages]

    Cons:
    These are quite obvious. In terms of function, none that I can think of. Otherwise;
    -Additional locations for hydraulic leaks.
    -Additional components to fail.
    -Cost.


    In general though, there are not many parts over a standard power steering system here, basically one hydraulic pressure line, one rubber return line, and a fan motor. That's it. All of the "hydraulic fan motor problems" other than the recall for incorrect manufacturing in 2003 are related to the pump or pump fitting/line, not the motor itself. Contamination in the systems cause the pumps to fail, which in turn takes the motor with it. Or in the case of 2003 recalls, a bad fan motor causes the system to be serviced, and when done incorrectly, the whole system fails. This is why it drives me nuts when people point towards the fan motor as the "problem" just because they don't understand what is happening. It is the victim of bad lines and fittings, and the victim of a botched service guide that results in all kinds of fluids being mixed. It is the victim of techs half-assing service, and contaminating brand new parts with old failure material. The Fan Motor is the VICTIM here, not the criminal.
     
    Last edited: Feb 4, 2013
  24. Viper Specialty

    Viper Specialty Viper Owner

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    Trust me, it has been. Part number does not always indicate a manufacturer change, usually only a specification change. I have even been in contact with the manufacturer of this particular part. Next time you have an original or replacement line kit in hand, look at the fitting it has on it or comes with. Now compare that to the replacement part sold separately. Look the same? Sure- from a foot away. Look closer at the tooling marks, it is very obviously not made by the same people, or at the very least not run on the same equipment. We have already determined the exact problematic change.
     
  25. Allan

    Allan Viper Owner

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    Yeah,.....the good fitting has a copper colored retainer, and jacked-up fitting has a skinny black colored retainer....................................-don't ask how I know. :crazy2:
     
  26. Garron

    Garron Viper Owner

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    Thank you for this information
     
  27. netapp

    netapp Viper Owner

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    You do not have to replace the entire power steering line if it is leaking at the fitting. 5 minutes with a dremel and I had the fitting removed and new one installed, if I remember the fitting was around $70.
     
  28. Viper Specialty

    Viper Specialty Viper Owner

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    And 0.5mm too far and you would have scrapped it. This is not something that everyone wants to do themselves, and is something we can do on a mill and save 95%+ of them without fear of damaging one by accident. However, it is a moot point: the problem isn't actually the line, it is the fitting. If a fitting can be engineered to not have a problem in the first place, THAT would be the correct solution.
     
  29. netapp

    netapp Viper Owner

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    Actually if you cut it with a dremel at the back of the threads that is where the c clip is, so if you do go a little far you only go into the c clip. It is actually pretty simple. Well worth the price of having to buy new lines. The dallas viper club had a good write up on this also, could probably get it dug up if someone would like it.
     
  30. Viper Specialty

    Viper Specialty Viper Owner

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    I understand what you mean, but my point is that you can replace the fitting as many times as you like- but the fitting is the problem, and without a proper design, it will be a recurring issue over the long haul. That is what we are trying to solve. And I am pretty sure if we couple a line exchange program with that where for a few bucks, we save you the hassle, expense, and time of removing your old fittings, people would jump on that rather than risk it.
     

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