Flowrate of the Stock Water Pump?

[Bolarbag]

Thumbnail calc:


Assuming the pump was sized for a 320hp (240kW) engine, rejecting a typical 60% of its brake power to coolant, the water flow rate required to keep the temperature rise across the engine to 8degC would be 292litres per minute.


That's 17500litres per hour, or 3849 UK gallons per hour,

It dependes on whether the pump is sized for cooling at max power or at some other condition. Because engine driven pumps are slaves to the engien speed, its not uncommon to find that the pump design point is actually something like a high embient temperature trailer tow, or hill climb test rather than flat out on level ground. The rest of the pump capacity above this speed ends up being an uneccessary overhead. Don't forget that the faster you are going, the better cooling your get from the radiator, so you can drop the pump flow a bit.


Electric cooling of car engines is a minefield. You will find that brute-force cooling (by attempting to mimic the maximum flow available from the standard pump) drives you down the route of a huge pump. Systems designed from scratch to use electric cooling have clever water jackets with low backpressure (or very fast flow), electrically controlled thermostats, and other gizmos.


Its very likely that for your specific use you could get away with a much smaller pump, but sizing it will be difficult. For information, to do it properly you want thermocouples in the pump outlet (entry to engine), engine outlet and the radiator bottom hose. The difference between the pump outlet and the engine outlet will tell you the temp rise across the engine (which should stay below 8degC). The engine outlet should also stay below yout chosen max temp - 120degC or so). The difference between the pump inlet and the radiator bottom hose will give you an indication of how open the thermostat is. You may find that by replacing the thermostat with one that opens at a lower temperature, you can decrease the water pump size by increasing the flow through the radiator under fast cruise conditions. If you do this, then a good electric fan will probably also be required for boosting the cooling when the engine load is high but airflow through the rad is slower, or ambient temps are high, etc.


I know you can buy off the shelf kits to do this that imply a simple fix, but I assure you, once you start looking into the detail it gets very complicated very quickly! Good luck!

A Quote from Digsy a very knowledgeable design Engineer over on mkivsupra.net

So I currently have a 35gpm electric pump - 2100 U.S gallons per hour, or 1749 UK Gallons per hour pump - quite short of the oem spec using Digsy's Calculation

However there is a point were the oem spec pump becomes inefficient at high flow although not enough to cavitate as there has been no evidence that I've heard of in the last 4years, also at lower rpms the flow will not be as high as the electric constant flow pump, I have installed the pump to do away with as much parasitic drag and give me more cooling control especially trackside where I can have the pump flowing - even whilst the engine is off

My Car is far from BPU now - here is the spec
Engine Specifications:

OEM Engine Internals
GReddy Chrome Oil Filler Cap
GReddy Sandwich Plate
GReddy Oil Filter Relocation Kit
HKS Oil Cooler
TRD Oil Filter
TRD Engine Mounts
Aeromotive FPR
Unorthodox Racing Pulley Kit
Virtual Works Power Steering Relocation Kit

Turbocharger & Induction:

Garret GT35R
PHR Air Intake Kit
GReddy 3Row FMIC
HKS Racing BOV Type II
FULL RACE Gen 2 Manifold
2xTial 44mm wastegates
4" FULL RACE Downpipe/Midpipe

Fuel, Tuning & ECU:

Motec M600 EMS, with Wideband Lambda, Advanced Functions and Data logging
HKS EVC 6
HKS DLI
PHR Stage 1 Fuel System
PHR Oil Feed/Return
PHR Water Cooling Kit

Exhaust:

4" HKS Hyper Titanium Racing Exhaust

Cooling:

Fluidyne Radiator
GReddy 1.3Bar Rad Cap
Maziere Electric Water Pump
AAP Motorsport Electric Fans
TRD Thermostat
GReddy Upper Rad Pipe
Titan Motorsport Lower Pad Pipe

Drivetrain:

6Spd Manual
RPS Street 6 Puk Clutch
RPS Cyn-r-g Lightweight Flywheel

Weight Reduction & Transfer:

Shift Sports FRP Lightweight Hood
Seibon Carbon Fibre Doors
Seibon Carbon Fibre Fenders
Abflug Type 1 Nosecone
Completely Stripped, Battery Relocation, Air Con Removed, Water Pump Removed Radiator Overflow Tank Relocated, 5L Washer Bottle Removed,

Suspension, Wheels, Tires & Brakes:

HKS Hiper D Adjustable Coilover Suspension
TRD Sway Bars
Cusco 6 Point Rollcage
Cusco Front and Rear Strut Bars
Do-Luck Underfloor Bars
Do-Luck Cross Chasis Bar

Uprated Front Discs

Axis Milano 19" - Currently speccing wheels now - either 17's or 18's with as close to stock offset as pos - must be light!
GoodYear Eagle F1's
285/35/19 Rear 255/35/19 Front

Interior & ICE:

6 x Defi Bf's
AEM A/F Ratio Gauge
HKS EVC 6 Display
2 x Recaro Pole Positions (FIA Approved)
Recaro Fixed Side Mounts

Exterior:

OEM Skirts
OEM Rear Spats
De-Winged

It was 3years ago I'm sure I last posted a thread with you pwapnas, but for the life of me I cant remember what forum it was - could you pm me if you happen to remember also