Electric waterpump project
Turbo Mini Forums

Oh my god we've created a monster

How much power is the fanbelt capable of taking without slipping?

I wouldve thought a few bhp max, somewhere there must be some charts to verify this.

to transmit 20bhp worth of losses from the fan and water pump through this belt to the crankshaft sounds a big ask??

or am i completely off the mark here?

Edited by mw3 on 28th Oct, 2013.

Matt W

20 hp would be a big ask, doable with a polly vee belt though.

Fuck me.... this is really going ott now

I seriously doubt it!

Have to say, whether i think it worthwhile or not, this is one of the first serious tech discussions in a while.....keep it up guys

I removed my plastic fan on my boggo 998 and fitted a pacet electric fan. It performed great. Much quicker warm up and kept the temps just where I wanted them. This was on a side mount rad. I deffinatley noticed a pick up in power. Only slight but noticeable.

On the matter of the electric pump, The only real advantage I can see is that it can be run after the engine has been switched off allowing less chance of thermal shock etc. On an A-series I cant see this as much as a problem but id fit one if I were doing a K-series conversion.

to bring a bit of fun in the convo i love this animation to play with flow :)

http://mitchellscience.com/bernoulli_principle_animation

Some heat balance calculations:



A couple of assumptions, firstly the U value. Numerous websites give different values. 700 seems about right. Secondly, I've assumed that the area of the radiator is the water side. If I include the fins then the Delta T would be better.

I've taken the cooling load from the engine at 22kW which is what my simulations say would be required to sustain 100hp. That's enough to cruise at well over 100mph, so is probably as much as you would get in a steady state condition.

I've not allowed for any heat loss from the engine/gearbox surface. There would be some depending on engine bay temps.

The water flow from the calcs is quite low and the power to pump that around the engine would be less than 1hp! These results are in line with other calcs I've found on the net.

The mechanical water pump is no doubt shifting far more than is required at high rpm. It would be sized for a worst case condition and pumps too much under all other conditions.

However, I'm starting to think that the load from the mechanical water pump is more drive losses than actual pumping power, particularly with an old pump with too tight a fan belt.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Nice Work Paul S.
As allways you look a Little deaper. Not just assuming everything. Great.

Now if i read this right, You say that the Water pump, pumps 39 liter per minute. At what engine speed does it have that capasity ?

If i have more toys than you when i die, I WIN

No, I'm saying that the engine needs 39 litres/minute to maintain a steady temperature.

The next part of this is to dissect a pump and derive its performance characteristics.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

interesting stuff,

so...... who's going to rig up a pulley in a 500w power drill and see if it'll turn a water pump to 6k?

and then measure the presure diferential across the pump....

Ok. Sorry, i misunderstood it then.

If i have more toys than you when i die, I WIN

Im my field of experience, Delta T on heat exchangers for chilled water is normally designed around 6 degrees and hot water around 10 degrees, though there are applications that differ from that, in the main those figures are common.

Edited by paul wiginton on 29th Oct, 2013.

I seriously doubt it!

The water pump will be turning faster than the engine speed - the pump pulley is smaller than the crankshaft pulley. Does that affect the calcualtions ?

Similarly, when the pulley size was changed, the fan must have moved less air at tickover.

Metric is for people who can't do fractions.

The calculation is purely an attempt to establish the water flow requirements of the engine. The pump and fan do not come into it at all.

I've calculated the likely temperature drop across the radiator from the heat load and surface area. I've then calculated the water flow from the same heat load and temperature rise in the engine.

Now we have an idea of the water flow rate, we can look at the best way to do it. What Evoderby has done is spot on for a remote mounted pump, but are there any other ways of reducing the pump load on the engine???

EDIT: If we can establish the performance of the standard mechanical pump, then it should be possible to pin down the potential power saving. Just need to cut up a pump to measure the impeller.

Also, I must point out, the calculation makes certain assumptions and assumes linear heat transfer across the rad, hence, the figures should only be considered accurate to within +/- 25% ish. I'm working on improving the numbers.

Edited by Paul S on 30th Oct, 2013.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul, I'm afraid there is a slight flaw in your calculations....took me a bit of a while to find it!

Roughly 1/3 of the energy contained within the FUEL has to be dissipated through the cooling system, not 1/3 of CRANK HP. Again this is just a rough guide / rule of thumb which says that of the energy contained within fuel about 20-25% leads to crank HP, 1/3 is lost through the exhaust in the form of heat, another 1/3 is lost -or managed if you will- through the cooling system. The rest is friction/pumping loss.

The 22Kw in your calculations should be at least tripled if not quadrupled. Also see this graph from an automotive engineering handbook that I have extended a bit past 5500RPM.



At higher revs Q can be 110% or 120% of crank power.

Cheers

On 29th Oct, 2013 Paul S said:
Some heat balance calculations:



A couple of assumptions, firstly the U value. Numerous websites give different values. 700 seems about right. Secondly, I've assumed that the area of the radiator is the water side. If I include the fins then the Delta T would be better.

I've taken the cooling load from the engine at 22kW which is what my simulations say would be required to sustain 100hp. That's enough to cruise at well over 100mph, so is probably as much as you would get in a steady state condition.

I've not allowed for any heat loss from the engine/gearbox surface. There would be some depending on engine bay temps.

The water flow from the calcs is quite low and the power to pump that around the engine would be less than 1hp! These results are in line with other calcs I've found on the net.

The mechanical water pump is no doubt shifting far more than is required at high rpm. It would be sized for a worst case condition and pumps too much under all other conditions.

However, I'm starting to think that the load from the mechanical water pump is more drive losses than actual pumping power, particularly with an old pump with too tight a fan belt.

Edited by Evoderby on 30th Oct, 2013.

I agree that 22Kw does seem a bit light given the "rule of thumb" guidance.

However, the data comes from the simulation of a turbocharged 998. So there is a lot of energy used to drive the turbocharger that is not included in the "rule of thumb".

Also the data comes from a simulation performed by OEM software that costs £600 a month for the license to use.

If you wish to work to the antiquated "rule of thumb", then triple the heat load. Simples.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Surely the energy used to drive the turbo is scavenged from the waste heat going out of the exhaust and won't affect the amount of heat absorbed by the cooling system ?

The turbo can't draw extra heat out of the block.

Metric is for people who can't do fractions.

Well aren't our engines antiquated either?

I have to say I'm genuinely intrigued by the outcome of your simulation program, the graph I posted is a bit more than just a rule of thumb. Slide 6 and 7 of the following link also shows around a 1:1 relationship between crank kW and Cooling heat load:

http://web.mit.edu/2.61/www/Lecture%20note...at%20transf.pdf

If turbocharging is indeed the 'missing link' here that dictates a 1:1/3 relationship something very interesting would happen in real life. Imagine a NA engine producing 100kW = 100 kW Q , now we slap on a turbo and have it produce 150kW....turbocharged Q should now be 50kW.

So according to the algorithms used in the sim software by upping the power with 150% the coolant load gets reduced by 200%......?? This seems highly unlikely unless I'm missing something very crucial here.

Wow this is a good conversation, and while its been a few years since ive done thermodynamics I cant get out of my head that we would be overlooking the effects of turbulent and laminar flow. It may well be that we are well above the velocities in all aspects of the engine to encourage a high reynolds number and as such good turbulent flow. But if one was to start slowing the pump down to save on HP and slowing flow through could laminar flow occur which would again effect the heat transfer or in simple terms reduce the cooling effect of the coolant and as such require a higher flow through the engine?

I have to admit that I would have to lean toward the fact that any power gains would simply be in the efficiency of the system where losses from the belt etc are no more. Its also possible that the impellor design in the electric pump is far superior and refined than the cheap rough casted effort in the standard pumps.

Quite probable that im talking crap though!

Come on, you can always find something on the internet to prove an argument:



The amount of energy required to drive the turbo is significant. All exhaust gas exits the cylinder at twice boost pressure, as a general rule, although only a proportion of it goes through the turbine, the rest through the wastegate.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Of course, if I'm wrong and the coolant heat load equals engine output, then a 20 USGpm pump is nowhere near big enough, yet they state that it can handle 250hp :)

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I have to say thats all clever stuff - goes way over my head. Looking forward to see if the theory matches Evoderby's practical findings and then also whether it matches mine, Gav's and Chris's findings

I seriously doubt it!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."