Water Pump Modification
 

Interesting thoughts brought up by Snrub in the Canadian forum, some of which I had been meaning to ask over here.

(Special thanks to renns for the free parts :p: )


Well, I went ahead and tore apart a water pump.

Heres some pics.

(I'll be posting information with pictures, so do your best to not interrupt me until you see my last post where I will say I'm done posting pics. :p: )

Pump housing:
https://www.rx7club.com/forum/attach...postid=2023553

One thought I had would be is does anyone think there would be anything to be gained by modified fins on the pump itself?

Have a look.

https://www.rx7club.com/forum/attach...postid=2023577

(*Cough* - Better view of the fins maybe in the 1st pic.. Stupid cheap digital camera..)

Polish the surface of the fins and knife edge their backside.

Cavitation is caused by excessive turbulence- the above mentioned will cut the turbulence down.

Another thought I had was:

"YAY! I can make a pulley without the stupid bell-shape sticking out (for the clutch fan)"

https://www.rx7club.com/forum/attach...postid=2023595

But to my dismay..

No

The shape of the pulley puts the bearings in the correct position relative to the loading on them (by the belts).

I would leave that alone in fear of short waterpump bearing life if it was messed with.

Re: Water Pump Modification
 

If the forum wouldn't timeout EVERY time I upload it wouldn't be so bad.. :(

NOT done..

STUPID SERVERS.

I am forced to to use my own hosting, where they will turn to big fat X's in mere weeks. So much for having pics for anyone who uses search! ;)

OK.

http://members.rogers.com/thecheat/wpmp7.jpg

I realized that you have to retain the shape, due to the pump design itself. Not worth messing with.

:)

Just spit it out and then post pics:p:

Finally:

http://members.rogers.com/thecheat/wpmp11.jpg

The pulley (in your hand) is very light, and where it mounts is fairly thin.

Machining new one(s) wouldn't be too tough I don't think.

A larger diameter pulley would result in a slower spin, which in turn would be better for higher RPMs, right?

One important thing I forgot to mention was this is for cars who see higher RPMs than most daily drivers. Snrub noticed his car got much hotter while racing at the track, and this is how the topic came about. A more efficient pump at higher RPM.

One thing I wanted to know (if anyone knows) is what is the most efficient engine speed (in turn, making the pump speed) for the most flow? Or is anything closer to idle speed best?

Would a bigger pulley (depending on how much bigger) make a big difference? I would think that it would, however thoughts are always welcome (yep, I'm done posting pics). :)

Edit: Radical Idea. Shave off 3 of the 6 fins on the inside of the pump? :D Comments! Now! ;)

If mazdacomp made a waterpump I bet it would be suitable for higher rpms...

If they made one?

I'd much rather modify my own if possibly to improve it any.. However if modifying a stock one yeilds next to nil for results, then I would have to get another one..

^

I did some EXTENSIVE searching and found the following:


Sounds like a reasonable solution.

I don't think removing fins would be a good idea. You could end up with more turbulence than when you started. Fluid dynamics is not intuitive.

Decreasing the speed of the water pump would probably be the best way to go (if you didn't want to do the polishing thing.)

:rolleyes: I saw that.

I'm not accepting one response as "the answer". I'm looking for thoughts or input on modification.



My thoughts exactly.. I'm not sure how much the polishing would help.. but then again I'm not an expert on the topic.. any more thoughts are appreciated. :)

Underdrive pullies.

I guess if the blades were more steamlined and polished when they cut into the water they would cause less disturbance and have less resistance so it would use less power to turn? I don't know too much about this stuff so just throwing it out there and keeping post alive

:boink:

Cavitation is caused by low pressure areas behind the impeller blades. I doubt you're going to remedy that with any modification you could make to the impeller.

Rob

You find a cure for impellar cavitation and the World will make you a rich man!!!

Ya, they sell these you know....

I thought of this already. Alternatives?

Duh.. :flipoff: :)

This is not necessarily for my own application. Perhaps a replacement pulley that can be installed before going to the track, and can be replaced. Removing the pulley itself is not a tedious task.

I would have liked to hear thoughts on preventing cavatation, but looks like theres no real solution I haven't heard before this.. :(

Modifying fins was just something that popped into my head, hence "radical idea". :p: Bad idea then, I take it?

Also:

Electric water pump won't cavitate...

Since he put my post in here, I still want to know if changing the pully is going to effect the cooling if I'm boosting for prolonged periods on the highway in the 3-4k range. :)

Anyone make one? Tough to install at all?

Sounds like an excellent mod for a track car! :)

Not for street use obviously.. At least I wouldn't imagine.. could it? :scratch:

May sound silly to the rotary community (seen it done on V8 drag cars), but, how about an electric motor (mount to stock air pump location?) with a small belt to power the pump?

May be something worth looking into for anyone who drives it on the road and doesn't mind doing a quick mod before seeing the track every now and again..

Again this isn't exactly for my purposes but for anyone else who may be seeking something of the like (eg - Snrub) :)

They are fine for street use and are used all the time on piston engines (not just drag cars).

I don’t see why it wouldn’t work, seeing as thought the 13b doesn’t flow any more coolant then a large piston motor.

The problem is finding one for your car. Current draw may be another issue if you are using the stock alt and have other elc. accessories.

An electric WP for my TA runs about $150. Typically the pumps are mounted on the stock water pump housing and either use the existing impeller or come with their own.

Hmm.. I would have Imagined it would just EAT the power if it was on all the time.. That and reliability for street use.. :scratch:

So your saying it's basically as I mentioned? an external motor that just spins the stock impeller? That's kinda neat.. :)

There is a company that already makes a replacement electric waterpump for the FD. I belive it was in a the Jegs catalog.

Should be easy to make an electric water pump. Find the flow capacity of the stock pump. Modify water pump housing with an inlet and outlet, and use short sections of hose to feed the pump inline which could be mounted on the fender well. The trick is finding the right pump. Summit Racing should have "generic" electric water pumps for this application.

Should be just as reliable as the stock water pump. Will draw more current, but as long as you don't have another huge electrical load like an e-fan you'll be fine.

Aaron do you have any numbers on amperage draw for water pumps? I'm at work, or else I'd be snooping around google for numbers. One that didn't have much draw and rated for lengthy use would be amazing. I haven't seen one yet though.

I was actualy thinking of taking an electric motor, fabbing a mount bracket, and pulley for both the pump and the electric motor, and mounting to the stock air pump location. This would be something more to do as temporary for a track day or racing day.

However I'm not overlooking Aarons suggestion. Infact I'm intrigued. :)

If I come up with anything, is anyone interested in stuff? I do fabrication at work.. If I can come up with some type of kit, weither it be my thought or Aaron's thought, anyone interested in it? I'm going to be doing this for myself just for fun. If this works out though I don't mind fabbing extra parts for anyone else who should be interested..

BTW - Upon closer inspection (duh) the stock water pump pulley can't get much bigger - it has barely any clearance from the main pulley as it is. If I were to make any type of modified pulley for the pump it would be for a belt system to match that of an electric motor..

^

They sell an electric water pump, made by meziere, but its design is sketchy at best. Installation would require refitting your BAC coolant feed line, your temp sensor, and your alternator. There is also no provision for a thermostat or a radiator cap, so on S4's, you need a different radiator.

How much of a problem is cavitation for you, honestly? With a fluidyne radiator, clean coolant passages, straight water with Redline WW, thermostat restrictor plates, and an otherwise stock cooling systems, our cars have no problems keeping cool when kept between 6000 and 8500 rpm at the track. We have installed clear braided hoses onto a car for a dyno run as well, and saw no cavitation at all up to 9500 rpm. I can't really see it being that much of an issue for anyone with a well-functioning cooling system.

Well it is always fun to think on new concepts, it is often more worthwhile to focus such energy on fields that require it.

You make a good point, yet take away any fun that could have been achieved. :p:

I still wanna try to fool around with something for a pump setup..

Turbo FC's and FD's do have cooling issues on a road-course.

I have a huge Griffin Rad, the largest E-fan that can fit, the 2nd small stock E-fan. I run 70/30 H20/Eg. My cooling system in in good shape. Problem is I also have a FMIC, huge turbo and I'm running 14 psi.

I was at the track with Snrub. My car was running at close to 221F (105C), which meant I didn't feel comfortable staying out for too many laps...

Although higher temps seem to be the norm for road racing, its still feasable to determine solutions. So I don't think Black13B's energy is wasted.

While your issue is definitely a cooling problem, what evidence do you have to support that it is from cavitation? You make a perfect example of energy that could be better spent; Black13B's efforts could easily be better focussed on working on better forms of ducting or a more efficient shorud for an electric fan.

For road course applications, due to the problems with cooling, it is usually best to run an intercooler that does not duct through the rad, such as a top mount intercooler, or an air/water system.

Whatever.

I was just giving the guy props for discussing a theory. Its not about evidence or whatever argument you want to start.

This forum is about information exchange. Right or wrong, its not a waste of energy...

As of now I'm already having a look around at electric motors (prices, reliability, speeds) and looking at machining pulleys.. Can't fab up any mounting brackets yet because it will depend on the electric motor size..

Main concern to think about - Along with this 'kit', I'll see if I can find a belt size and number (crossreferenced to other manufacturers) that will be used in replacement to fit over the alternator to the main pulley (sans water pump)

While I wait for any more input or ideas from you guys. :)

BTW - Regardless of if it's due to cavitation or not, I'm still doing the project as an experiment. Worth a try, right? If it improves temperatures, then.. well.. that's a good thing right? If not, then no big deal.. it's just for fun..

You have taken me out of context. I did not say it was a waste, merely it could be time better spent. I did not decline his reasons for asking, merely questioned how much of a problem this actually was. Hate to bring up cliche's, but, "If it ain't broke, don't fix it".

I recall a forum member used to have a belt-drive electric pump on his S5 TII, so it has been done. A search should provide more insight on it.

https://www.rx7club.com/forum/showth...ric+water+pump

Few months old.

On the contrary, I am going to be making brackets that mount it to the air pump loaction. No alternator or any other crap will have to be relocated.

My plan is for it to just bolt up, drop the belts, install a sans pump belt to the alt, and change the pump pulley.

Easily could be done within 30 minutes (stay focussed ;) ).

And pehaps a harness that lets you plug it in and unplug it easily.

More of a design for streetable guys who like to visit the track.

I just think it's worth a try to tinker with.. part of my own experimentation with the system. Should it work out, I can fabricate brackets and pulleys as a "kit" for others.

^

so the idea is to have an external electric drive for the stock waterpump, in order to prevent overspeeding the waterpump resulting in loss of flow due to cavitation, yes ?

I rather liked the original idea of improving on whatever is causing the cavitation at high pump speed.

mostly because I like the idea of increasing the flowrate through the engine, instead of decreasing it by restricting pump RPM.

polishing the impeller strikes me as a fine start, and reshaping the fins to help them smoothly slide through the water looks to be a good idea too.

where I see the problem is in the pressure drop happening because of the drag of the radiator and engine.

as in it looks like the pump is trying to pump more water than the rest of the system can flow resulting in a low pressure area at the pump suction causing cavitation.

a pressure relief bypass that opened to allow water to fill the low pressure area would prevent the cavitation at the expense of bypassing the engine, or the radiator, or both.

how about using the electric motor to run a bypass booster pump that would take a suction somewhere warm and dump it into the stock pump suction ?

sorry, I am not yet familiar enough with the 13b water circulation to visualise specific flowpaths.

hmmm, do cars with that deareation tank suffer from cavitation ? it seems like that system is similar to the bypass I first mentioned.

I just got the WP & housing from a gxl{?} and intend to do what I can to enhance flow through them.

Wow, I almost forgot about this entirely. I got the electric motor and everything! I had some concerns before I moved ahead with the project, and other pesonal issues came up and I have not had the time to get digging away at it.

I will soon though, I've got my FC in storage (which was a big hassle finding the proper place where I could work on it too). I'll be soon having alot of free time again, and all my tools, RX7, and RX7 spare parts (for tinkering ;) )are finally at the same place.

the alternator belt will be in the way
put the alternator at the air pump location
mount the electric motor where the alternator was

better hope you dont blow a fuse on the electric motor.. you can kiss that motor good-bye if it happens

No.

Custom pump pulley with sheaves moved ahead to mate with the mount design of the electric motor will keep the alternator belt away from the pump.

Air pump location is the easiest, since most guys are not running an air pump. So - you are saying with the alternator at the air pump location the belt wouldn't happen to go right through the impeller shaft? Think about it. Even if guys are running an air pump, air pump removal is quick and straightforeward. However I leave it up to them to decide what they would do with the lines going to the ACV.

There is going to be only one thing driven by the main pulley. The alternator. At least on the 2 sheaves closest to the front cover. Guys who run P/S or A/C is up to them, I propose something that will bolt up to even the guys running just the alternator and water pump. The stock location doesn't touch the water pump with a modified pulley. Also the stock location happens to be the easiest place the put the alternator. No hassle.

In the even that a fuse is blown or something happens, personally I would wire a check light circuit, so if a light comes on it means the water pump as stopped recieving power. Pretty easy to make with just a general relay. However that is myself. This kit I may come up with (I don't proclaim to be any type of business, this is just something personal that I don't mind making a few extras of) will not have a wiring setup included. I will leave that to each their own, the same way people have wired up electric fans. There is competent electricians here. If you don't know how you should wire the pump up, perhaps you shouldn't use an electric powered pump. Everyone knows when they are getting into it if they aren't doing it properly they are taking the risks associated. I'd much rather leave a positive and negative motor cable with stripped ends for anybody who want to come up with their own design. I really don't want to provide a diagram and then have people coming to me saying they blew something, wether it be the battery, ECU, or motor itself from faulty wiring.

I read in a post or something a while ago that the S5 waterpump worked better at higher RPMs before it started to cavitate. Can anyone confirm this?

I'm stating this without claims of any demonstrated cavitation with the RX-7 stock pumps.

There are direct solutions to reducing cavitation at the site of the impeller.

Water will rip apart when a portion of it is accelerated too quickly (let's search for a formula). When ripped, the vacuum formed evaporates some water. If the rip is momentary, it collapes and leaves a tiny gas-state water bubble. An impeller can rip enough water open that the displaced water slows enough that cavitation increases, so cavitation can increase and be sustained at a fixed RPM.

One way to reduce cavitation of a fluid is to reduce the impeller's rate of accelerating that fluid. This rate can be reduced with more impeller moment -- using more time to accelerate, reducing rip.

Another way to reduce cavitation is to fill potential cavities before formation. An impeller can be designed with subset vanes, in areas where the water is being accelerated and released the fastest, such as behind and near the trailing edge of each lead vane, common in turbocharging.

Ultra high total system pressure can reduce cavitation, but not so feasible.