I completely agree, however you are talking about drag (amount of energy loss per unit time), not inertia (resistance to acceleration due to mass). While there would be an increased electrical load present due to the water pump running, this has very little to do with how much energy it takes the engine to change speeds and more to do with how much energy it takes to keep the engine spinning at a constant speed.

The reason I say better throttle response is because you could completely remove the water pump from the pulley system, thereby reducing the engine's rotating mass and consequently provide better throttle response. A beefier alternator would be required which would likely impose additional rotating mass, but should not be equivalent to the amount of rotating mass eliminated.

*Edit* But I also completely agree that in theory, this all sounds nice. In practice, things can be quite different.

I'm not so sure this is true. Essentially the only fast failure mode for a MWP is the drive belt breaking - which also fails the alternator and lights up the normal dash display. MWP slow failures are generally preceeded by squeaking, or leaks around the bearing seal. An EWP could also have a bearing failure, but additionally, a motor failure, controller failure, or failure of one of the sensors used to adjust pump rotation. All of these could easily result in limited flow but still have current going through the motor power wire. Certainly, if there is no power to the motor with the engine running, it's easy to trigger a warning light. Not having proper flow isn't so easy to monitor. Adding an overtemp warning is also rather easy, but won't always save you. Why? Without flow, temps on the inlet or outlet of the engine may show normal while the engine is cooking. (One might argue that a thermostat problem in a MWP system could do the same thing, but thermostats always have a little burp hole, so as long as the MWP is at least partially functioning, there is always some flow even with the thermostat fully closed). Probably the sensor at the OBDII location will show rise in the no-flow condition, but then one has to get that signal out and into your interlock system; Tee-ing off the port won't work very well either, because it pulls the sensor out of the coolant flow stream.

Another part of it is that the ewp is running a constant speed based on the temp of the engine, not the rpm of the engine, so reving the engine would not have a direct effect on the ewp rpm. the electrical draw from the ewp would be more constant, thus not having as big of an effect on the electrical demand as some might think and could be accounted for.

But like a fan controller on a computer motherboard, you could get pump rpm data and then with a couple of temp sensors work out "expected" rpms at various temps and be able to set up a warning system. basically, if temps are rising, the controller keeps boosting ewp rpms until temps pass a certain fail point then it throws the warning light/engine limp mode or whatever. also, if the pump is failing (i.e bearing failing), the draw (amps? ohms?) on the electrical system would be greater than expected for a given rpm and that could be seen also.

Picking nits perhaps, but with the belt off sometime, grab the waterpump pulley and see how fast you can twist it back and forth, then do the same with the alternator pulley. There is very little rotational inertia in the water pump by comparison. Going to a bigger alternator will add much more rotational inertia to the system than removing the MWP will take away. The pulley/shaft/impeller might weigh a pound or so, an alternator armature weighs 10x that, plus that mass is located much further from the rotational axis. Don't forget too, that if you increase the rotational speed of the EWP, you are also fighting the rotational inertia of the impeller/shaft/motor - which again will be more than the equivalent MWP. Acceleration (of the car) comes from the power in excess of what's needed to maintain constant velocity motion. Drag in any form, takes always from that excess power, no matter where it comes from. I agree that there are several potential advantages of an EWP, but not that there is much to be gained by elimination of that represented by the MWP. (Unless, like for drag racers, the pump is shut off entirely for the duration of the acceleration run).

Very true. My thinking is that most of the sensors used to control the flow rate of the pump would be sensors that are already in place. For example, use the air intake temperature sensor for ambient temperature, use the throttle position sensor to perform the engine load calculation, use the RPM sensor for engine speed, etc. A failure of any of these already-present sensors would have significant impacts on either the ability to drive or overall operation of the motor and therefore are worth checking for errors.

However, I agree that there are a variety of ways in which a system like this could fail and it is impossible to account for them all. Therefore, a temperature sensor close enough to the core engine components such that it would be heated in a no-flow situation would be a requirement.

Given that, I don't think it's impossible. Years ago people had a similar debate with electric power steering, yet here we are.

True, but I think a properly implemented EWP system relies on more than engine temperature to calculate coolant flow. Take warmup - the engine is cold, so if the flow was based on temperature, there would be little to no flow. However, this isn't what you want. Higher flow during warmup could help to spread the heat from the combustion side of the rotor housing to the intake side, providing a more even warmup process. And likewise, if the engine is at operating temperature, the flow would need to be much different if the ambient temperature is 40 degrees compared to 100 degrees.

And like HiFlite999 said, it is much easier to proactively cool an engine as it produces excess heat rather than cool it off after. For a short burst up to 9k, the thermal mass of the engine along with moderate cooling could somewhat handle the temperature spike in an effort to provide peak power to the wheels, but spending any significant time in the upper RPM range under load would necessitate higher coolant flow. Doing this before the engine begins to warm substantially would help reduce thermal runaway.

But the MWP and the alternator have different load/RPM functions, and therefore comparing their relative loads at low speed isn't significant. Try turning both at 3,000 RPM and the story is much different.

*Edit* But I see your point here. I guess it really depends on the final implementation, but my hope is that the marginal increase in inertia from the larger alternator would be less than the reduction from having the entire pump assembly, pulley, etc on the engine directly.

great discussion.
No truer words have ever been said than "The devil is in the details". Totally agree with that.

With the EWP's that are on the market now---no alternator upgrade is required due to sole addition of the ewp.
To simplify the arguement--just look at the dyno results of before / after installations in recip engine cars?
Wouldnt it be nice if the ewp controller could be individually set?
If things continue to progress as I anticipate (God laughs) then this spring I intend to more seriously pursue this idea.
Throwing all therum asside---this just makes a lot of common sense.
Who knows---it may end up being a supplimental pump for low rpm and shut off use?
OD

My next question is about the thermostat. To my understanding, the only reason the thermostat is there is because there is no other ability to control the flow of the coolant with a MWP. However, given an EWP, it seems like a conventional thermostat would reduce the functionality of the EWP. Two ideas come to mind from this.

The first is to operate without a thermostat. In this case the EWP would pump at the desired rate of coolant flow through the radiator. This slightly reduces the complexity of the cooling system but imparts a critical disadvantage. That disadvantage is that during warmup, there would be very little to no coolant flow. This is bad because it eliminates the possibility of using the coolant to help to evenly heat the exhaust and intake sides of the rotor housing, and reduces or eliminates the possibility of using the coolant to warm the throttle body and cabin until the engine is completely warm.

So my preferred option would be to use an electric thermostat. In this case the pump can run at high speeds during warmup to aid in evenly heating the rotor housings while not running the coolant through the radiator. This would aid in engine warmup significantly. Also, I've noticed during highway cruising in cold weather, my engine cannot always maintain full temperature, likely due to coolant passing through the radiator and being excessively cooled. An electric thermostat would prevent this and aid the engine in maintaining a proper temperature in a variety of ambient conditions.

However, an electric thermostat gives another piece to fail.

Thoughts?

electronic thermostat as in computer controlled? I would want to add a manual override to control it myself when on the track. This would allow me to warm up the engine faster.

believe it or not there are ewp with a built in bypass for warm up!

Believe it or not...all this discussion about regulation of EWP speed etc seems a bit overkill :)

What in hells name would you want to electrically regulate it for.....the thermostat does an amazing job of keeping the engine at a steady temperatre .....if it is closed you circulate the coolant in the block...if it is open it goes to the rad ;) The more circulation through the block the less chance of fluctations in temperature between the hot and cooler side

Having an electrical pump is complex enough.....

because sometimes you want the thermostat to stay closed a little bit longer, like to rapidly warm up a car for the track.

i really dont like the bypass in this engine--i dont believe that the thermostat is fully sealing it Dan. Now with pressureless coolant (evans) --then yes it probably would.
Whether or not a small leak makes any real difference, I am thinking it could. Most of the time probably not--but during those border line times--yes?

I once modified a thermostat housing, back in the day before we had the 180 mazmart thermostat, to be able to use a barrel sleeve 180F thermostat. I had to permanently closed the by pass to use that thermostat. Now I dont know for sure which one affected the cooling more, but I actually had difficulty in getting the engine up to proper temps--period. remember now I do have a secondary radiator set up. It was a big enough difference that I have to remove it.
Dan--you are the only one I know that has and is running the ewp. Can I ask what makes it so "technical" ? A true ?, trying to learn.

I'm not sure why the bypass needs to seal that well Denny.....if it leaks too much it will cause slightly slower warmup..but these engines aren't exactly slow in that deparment anyway.

As for the tecnical part..nothing too technical...the pump does add some complexity and a bit of an electrical draw....but in the grand scheme of things it isn't that much of a draw....I think the pump I have draws 5 amps or something when it is running...not a big deal really.
I have replaced the cooling fans with a larger unit that draws less current than the stock twin fans..so in my case it balances out anyway.

My logic for the pump is this....more circulation through the block will always equate to more even temperatures in the system....as long as the flow isn't too much that there isn't strange eddies from the flow. The engine will warm up the same if the bypass seals effectively enough to limit the flow through the rad when it is closed. With the double pass radiator I have..the extra flow will allow lots of time in the radiator to allow heat transfer

The biggest thing I am trying to correct with this is the inability to cool the system at slow speeds...and cool down time in the pits after a session.....it really makes a huge difference when the fans are running and the coolant is circulating with the motor off....I used to see the temperature in the pits climb way over what I was comfortable with..even with no load on the engine.

What coolant do you use? Evans?

I have used both standard EG and currently am using NPGR

I will see if it is worth the cost and hassle this year :)

Thanks Dan---cooling in the pit is something the folks in this area do by using those big floor drying fans--but the engines are OFF.

I don't think it is overkill, and here is why.

Let's say your coolant is at operating temperature and therefore the thermostat is partly open. The car is driving at highway speeds and therefore there is a constant flow of air over the radiator. Let's say that the system will balance if the ambient temperature is 70 degrees - that is, the amount of heat being released by the engine and the amount of heat be dispersed to the air by the radiator are equal. In this case, the engine maintains its operating temperature.

Now let's have everything be equal, except that now it's 20 degrees out. The thermostat has no concern of what the ambient temperature is, so it opens like usual. But since the air passing over the radiator is cooler now, more heat is dispersed to the air by the radiator than the engine is producing. Because of this, the engine temperature falls, potentially below the ideal operating temperature.

With the current setup, there is no way around this. A MWP/thermostat system is not able to control the engine temperature independent of the ambient temperature at high speeds. That is to say, if driving at highway speeds and the ambient temperature drops 20 degrees, that will be reflected by a drop (not necessarily the same amount, but a drop still) in the engine temperature.

This is an everyday example (assuming you live in a cooler climate) of why this idea is useful.

Last time I checked the thermostat openned and closed with temperature changes .........so when the temp drops it closes till the temp raises and it opens again. I did live in a climate where -40 wasn't unusual...and there we had to block off the rad with cardboard to get thing to warm up.

but with electronic systems you wouldn't have to. you could just run it closed.

that somewhat is one of my points also? Thanks for posting. I think the ewp (thanks for posting the link Team, people use that controller with different pumps too not just the davis one) can be made more sensitive to changing coolant temps?
Here is my thinking. The thermostat acts as a restrictor. That is the only way it can control the coolant's temperature. The MWP doesnt care. Its going to pump reguardless. Now what happens to coolant that is being squeezed through a restrictor? Yall get my thinking? Whether it is going through a by pass or not it doesnt matter. The coolant is not going to have a smooth flow. There is going to be a lot of turbulance. Now compound that with any possible air in the system, bubbles from steam etc? Not good IMHO.
Now evans helps some with that as it is a pressureless coolant BUT the turbulance will still be there?
Now I do realize that breaking up the coolants boundry layor can be a real good thing, but doesnt that depend on how that is done and where is is being done?

The ewp with sensor control and possibily evans just makes too much sense too me.

Again, I think it may make more sense for excellant temp control for street use rather than track?
Please also notice that the fans are under direct control from the emp controller, not from the pcm. So on an over run situation, when you shut it down, the fans can be made to continue to run too.
Add the S2 model fans and it would be one hell of a package?

Something else to think about? With the EWP and no thermostat--how about reverse cooling?
Am I crazy? Hope so, crazy folks seem to have a lot of fun:)
Reverse cooling has never been done in the rotory engine that I know off.
Why cool the exhaust ports before the combustion area?
Thinking is -- cool the hot spots in the engine 1st--right?
Now is the combustion side hotter than the exhaust side in our engine? I think it is the exhaust side?
Where does the renasis engine seem to have the most problem?
Apex seals?
Corner seals?
Side seals?
Well cooling the exhaust area 1st would benefit the corner and the side seals more? I think the apex seals can take a little more heat better than the side seals?

Cooling the exhaust side really doesnt saturate the coolant much at all. I have measured temps from the coolant before and after it passes through the exhaust area and it is only about a 20F difference. With reverse cooling I think that the cooler coolant would scrub more heat than it does now?
Does the rear rotor run hotter than the front one? Most people would say yes. Reverse cooling would take care of that. Well would that just make the front rotor hotter than the rear? I am not sure, but I do know that the front rotor has more airflow exposure which may help some?
Do yall see where I am trying to go with all of this?
PS --I did get out a little this w/e. I went to home depo!
OD

That is pretty cool.

You don't want to heat the intake portion because that would heat the air/fuel mixture. You want the mixture as cold as you can get it, colder air means more oxygen which means more power. I would rather the intake receive the coldest coolant first, and keep more horsepower.