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

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.

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.