Cup electric PS pump conversion
Thanks...
1. BMWTYE, where did you get the mounting bracket from?
2. Mine came with the motorsports lines, but they are a PITA with the other stuff I already have in the frunk. Using the HRG/ Rebel racing fittings, did you just use standard AN lines to make the lines, or are special high pressure lines needed?
3. Any special fluid needed? Or just using the standard Pentosin stuff?
4. Does it have to rubber mounted or can it be hard mounted like the one with the band clamp showed?
Thanks
Brandon
One post mentioned that it eliminates a Pentosin fire hazard at the rear. But the fire hazard of engine oil, coolant, and gasoline is still there. And then it moves the fire hazard to the front, where there's already gasoline and brake fluid that can burn, and it adds an electrical connection which carries a small risk too. I can see that it eliminates the need to undo a hydraulic line during an engine drop, but how often do you really do an engine drop? And undoing that line during an engine drop only takes just seconds if you know what you're doing. My guess is that the weight is similar either way and that the power draw is similar too, whether it be through the mechanical pump or through the alternator. And by moving it to the front, you eliminate some trunk space, which wouldn't be ideal for a street car. I don't know the reasons the factory did it for their race cars, but my guess it was mostly for simplicity. But if you already have a working system built in to your street car, is it worth this change from any measurable mechanical standpoint? It's fine if the only reason is "that it's cool." Lots of changes are made for that reason, and that's legitimate as far as I'm concerned. But let's call it what it is...
Last edited by Rob S; May 21, 2018 at 01:15 PM.
One post mentioned that it eliminates a Pentosin fire hazard at the rear. But the fire hazard of engine oil, coolant, and gasoline is still there. And then it moves the fire hazard to the front, where there's already gasoline and brake fluid that can burn, and it adds an electrical connection which carries a small risk too. I can see that it eliminates the need to undo a hydraulic line during an engine drop, but how often do you really do an engine drop? And undoing that line during an engine drop only takes just seconds if you know what you're doing. My guess is that the weight is similar either way and that the power draw is similar too, whether it be through the mechanical pump or through the alternator. And by moving it to the front, you eliminate some trunk space, which wouldn't be ideal for a street car. I don't know the reasons the factory did it for their race cars, but my guess it was mostly for simplicity. But if you already have a working system built in to your street car, is it worth this change from any measurable mechanical standpoint? It's fine if the only reason is "that it's cool." Lots of changes are made for that reason, and that's legitimate as far as I'm concerned. But let's call it what it is...
I agree that to go electric, the engine compartment would be one notch less cluttered, if that's important to you. But there's still a lot of mechanical clutter that you can't eliminate there, and by moving the pump forward, the trunk becomes one notch more cluttered in the process. It's a trade-off.
So, I'm not convinced that there's a good and legitimate performance, convenience, or safety reason to do this to a factory street car, even if it's used on the track. But hey, if you think it's cool, then go for it! I even have a pump to sell if someone's interested. This is a newly remanufactured VDO pump that is equivalent to those used in the earlier 996 Cup, R, and RS cars, and is a drop-in replacement for them. Obviously, to fit it to a street car would take some mounting hardware, plumbing, and electrical work. PMNA wanted about $1800 for the new version of the early Cup pump last I looked, which was 3 years ago. I'll sell for $600 plus shipping.

But seriously think of it this way:
- Weight - You are not saving weight, you are distributing it to the front, which is significant as these cars obviously have a rear weight bias. Every bit helps on a track car, otherwise why would light weight mods like battery, windows, etc. exist and be expensive? Less weight = speed.
- Safety - On a street driven car there are no leaks as the pump is not under stress. If you have a cup car conversion and are using wide front tires and go fast around the track it will definitely overheat and fail, so having the pump up front reduces the risk. Installing an overflow reservoir is a possibility, but now you have to find the space in the engine compartment.
- Convenience - Race teams run these pumps for 40 hours and replace them, because they fail due to stress. Having easy access to the pump and the steering system makes it easier and faster. You don't have to drop the engine to take out the original pump and can just drain and leave the plumbing in the car.
- Efficiency - The alternator already provides sufficient current to drive the pump. I am not sure that the engine has to work any harder to produce that energy.
Overall there is a clear reason as to why the race car comes with this setup, but you are absolutely right, that on a normal street drive GT3 the mod is pointless other for the "uniqueness" factor. I was just sharing the reasons I would have it in my street car that became the track car.
My pump is fine. Engine came out.
I kept stock setup. Just didn't want to mod my RS to that extent
Fire from pentosin is a very very real issue. .
On my 964 we ditched the PS system and put a cup pump on it. There is a definite weight savings and complication saving on these cars.
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An electric pump has fewer losses. I.e. Electric motor can operate the pump at a fixed speed and will only draw as much current as is required, whereas an engine driven pump is always spun at (some ratio of) engine RPM. Any excess is then continually pumped through the bypass valve. So, a pump that can supply adequate fluid at 2k (engine) rpm is going to be pumping way more than is necessary at 8k rpm while also dealing with the mechanical losses from friction and inertia.
Last edited by powdrhound; Jun 21, 2018 at 03:14 AM.



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