Thread: water pump UD pulley

It depends on your desired outcome. An electric water pump (EWP from here on) can use less engine power compared to a crank-driven pump. The reason the electric pump is able to do this is because it can operate off of the battery (essentially a power reserve). This is advantageous for heavy accelerating, where the engine is temporarily relieved of "water pumping duty" by using the battery power.

It should be noted that an EWP should decrease your MPG because of the inherent energy conversion process. You are converting mechanical power from the crankshaft into electric potential at the generator and back to mechanical power at the EWP. No energy conversion will be 100% efficient, so there are energy losses. In real-world situations, I suspect that the difference in MPG will be negligable between the two pumps.

Of course there are other factors to consider such as whether the electric pump can shutdown when water circulation is not needed. Also, the actual pump (not motor) has an efficiency rating that may be greater or less than the stock unit.

Why do I make such a detailed stink about everything? I'm a mechanical engineer.

ive had mine from zzp on my car for 5 years now. it runs cool, never had an overheating issue. the stock pulley weighs a lot compared to the zzp one so less rotating mass is good i guess.

Changed mine to ZZP's UD pulley, temps stay right near 180 still, the difference in weight is about a lb, but alot of that is in the middle where moment of inertia is changed the least. Over the next 3 tanks I noticed a .2 mpg increase, which is within the realm of being statistically insignificant, but I can see how it would be a real change.

But for 30 bucks used on CGP I have to say I think it was worth it.

Originally Posted by 01GTP

The alternator has the same drag no matter how much it is charging on theses cars. So adding more electrical load will not put more load on the engine.

No offense intended, but I would be happy to explain the fundamentals of this concept if you wish.

Originally Posted by matt5112

No...

It runs off of your alternator.




Again, alternator power. Not battery.



The alternator spins regardless.

They're 50% efficient.

But the pump draws 6-7 amps according to manu.

Thats 100 W.

Thats 0.26 HP draw from the engine.

ZZP claims it frees up 7 hp.



And not an electrical engineer.

Please try to read my posts a little more carefully.

Notice that I said "depends on your desired outcome" followed with "can use less power compared to a crank-driven pump...."

Clearly, I was stating this in the most general sense; disconnect your alternator when racing. That's why I called the battery a power reserve. I once drove my Olds Alero for over 50km without knowing that I had a broken serpentine belt (no alternator charging). The car did not stop until I turned off the ignition at my destination. That aside, disconnecting the alternator is something I will never do, for many reasons, but I will re-iterate that the aforementioned quote was clearly in the most general sense.

Your response of "The alternator spins regardless" is an interesting one. Very obviously, the energy conversion process I talk about is occurring. Again, you will want to notice some of my wording: "...an EWP should decrease your MPG..."

Nowhere do I give quantitative reference, simply qualitative.

You go on to mention some numbers and statistics which I don't care about because I was only providing theory between the two types of pumps. What the manufacturer claims is their claim and real-world testing sometimes provides unexpected results. Notice that I mention "real-world situations" in my second paragraph.

There are many reasons why ZZP claims that the stock WP is using almost 7 HP more than the electric version. Removing the the stock WP deletes one pulley and the associated friction, bearing losses, windage, etc. Also, how do the maximum flow rates compare....and there are many more reasons. The main point is that the theory I have provided is correct.

Again, read my posts more carefully.

Awaiting your response....

Originally Posted by bluegtp91

I read your post carefully...and if your going to debate something...you NEED numbers and statistics...saying you don't care means just that...you lost.

Done.

Nice try. I gave you 100% correct theory about these pumps. If you cannot comprehend that's fine.