and hopefully next time im back, ill have this thing running
Hi guys,
Would it cause any problems if i slowed down the water pump on the car a tad? Basically i have two pulleys which fit on the crank (they were both on
there but one drove the PAS pump).
I only need one pulley (will drive both water pump and alternator)
To get a good size trigger wheel it would be better if i used the PAS pulley, but this is smaller than the normal water pump pulley. (water pump
pulley is about 150mm diameter whereas the smaller one is about 120mm)
Will this cause any problems in the future?
Cheers
Mikkel
Might actually be beneficial for cooling at high RPM.
And might cause problems when stuck in traffic due to too low coolant flow. It all depends largely on rad, fan, shrouding etc. I'd just try it and see what happens.
well i thought that, but then i thought that i wont have a heater matrix , and the rads closer and smaller, so there wont be as much water to push around so it might counteract the effects of slowing it down?
it could cause cavitation
Fairly standard practice on race cars. We did it on our racing TR's with no ill effects.
As long as you have a sufficiently efficient cooling fan there shouldn't be a problem.
You're not slowing it down that much anyway.
Geoff.
sweet, cheers guys, will definatly do that then, will get the trigger wheel ordered now im home,
and hopefully next time im back, ill have this thing running
quote:
Originally posted by DRC INDY 7
it could cause cavitation
It's less likely to suffer cavitation!!
me possibly being stupid...
whats cavitation?
It's when you eat too many sweeties and your teeth go bad.
quote:
Originally posted by Miks15
me possibly being stupid...
whats cavitation?
so by slowing it down it wont increase the chances then,
I think im just going to try with the new pulley and hope it works (cant see any reason it wont, especially not after whats been said)
Cavitation is when the demand of the pump exceeds the available supply, the pump will draw a vacuum and gas will be drawn out of the liquid. At the
discharge side of the pump the the bubbles of gas implode causing metal erosion.
That' my understanding anyway.
Davie
quote:
Originally posted by daviep
Cavitation is when the demand of the pump exceeds the available supply, the pump will draw a vacuum and gas will be drawn out of the liquid. At the discharge side of the pump the the bubbles of gas implode causing metal erosion.
That' my understanding anyway.
Davie
Fluid Dynamics;
"Discharge cavitation occurs when the pump discharge pressure is extremely high, normally occurring in a pump that is running at less than 10% of
its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow
out the discharge. As the liquid flows around the impeller, it must pass through the small clearance between the impeller and the pump housing at
extremely high velocity. This velocity causes a vacuum to develop at the housing wall (similar to what occurs in a venturi), which turns the liquid
into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump housing. In addition,
due to the high pressure conditions, premature failure of the pump's mechanical seal and bearings can be expected. Under extreme conditions, this
can break the impeller shaft."
quote:
Originally posted by daviep
Cavitation is when the demand of the pump exceeds the available supply, the pump will draw a vacuum and gas will be drawn out of the liquid. At the discharge side of the pump the the bubbles of gas implode causing metal erosion.
That' my understanding anyway.
Davie
Just one thought.
According to the Graham Bell book on 4-stroke tuning. One of the things that stops localised boiling is the pressure of the water (we knew that). He
claims that the water pressure from the water pump is the dominant source of pressure (in the block) I can't remember what pressures he claims.
He does know his stuff, but his book is a bit v8 centric.
Slowing the pump would decrease the pressure and hence could lead to localised boiling (and hot spots).
I guess it must depend on the engine. Loads of people run bike engines with electric Davies Craig pumps, that are variable speed, so on those engines
it can't matter.
Also the book is talking about engines that have been tuned to the last possible bhp, so this is probably not relevant.
Just a thought,
Matt
quote:
Originally posted by matt_gsxr
Just one thought.
According to the Graham Bell book on 4-stroke tuning. One of the things that stops localised boiling is the pressure of the water (we knew that). He claims that the water pressure from the water pump is the dominant source of pressure (in the block) I can't remember what pressures he claims. He does know his stuff, but his book is a bit v8 centric.
Slowing the pump would decrease the pressure and hence could lead to localised boiling (and hot spots).
I guess it must depend on the engine. Loads of people run bike engines with electric Davies Craig pumps, that are variable speed, so on those engines it can't matter.
Also the book is talking about engines that have been tuned to the last possible bhp, so this is probably not relevant.
Just a thought,
Matt
quote:
Originally posted by matt_gsxrAccording to the Graham Bell book on 4-stroke tuning. One of the things that stops localised boiling is the pressure of the water (we knew that). He claims that the water pressure from the water pump is the dominant source of pressure (in the block) I can't remember what pressures he claims. He does know his stuff, but his book is a bit v8 centric.
I was only quoting, and will quote further:
Four-Stroke Performance Tuning
A.G.Bell 3rd Edition
p.433-4
"
Water pump considerations
However, when water pump speed increases to the peak efficiency speed of 4-6krpm it is not the radiator cap that stops boiling but water pressure
created by the water pump. Even many race engine tuners do not seem to understand that regardless of the radiator cap pressure a water pump spinning
at maximum efficiency rpm will produce a pressure head of around 30-40psi in the engine block and head when water flow out of the head is limited by
thermostat or restrictor plate. This pressure packs coolant around the top of the cylinders and around combustion chambers to carry away combustion
heat and stop an insulating blanket of gas bubbles forming in these areas."
If you want to read the rest then buy the book!
He also goes on to say that he does under-drive the pumps sometimes, although this is all relative to the "maximum efficiency zone of
4-6krpm" I doubt you know that for your pump.
I like the book, I can't say his physics is up to scratch. For example in the introduction he says:
"Take the laws of gravity or the day/night cycle as the earth rotates around the sun."*
Which didn't inspire confidence. But he is good at citing evidence of doing things which I like.
Matt
*Obviously the earth rotates on its own axis causing the day night cycle. Rotation around the sun takes a year!
quote:
Originally posted by matt_gsxr
I was only quoting, and will quote further:
Four-Stroke Performance Tuning
A.G.Bell 3rd Edition
p.433-4
"
Water pump considerations
However, when water pump speed increases to the peak efficiency speed of 4-6krpm it is not the radiator cap that stops boiling but water pressure created by the water pump. Even many race engine tuners do not seem to understand that regardless of the radiator cap pressure a water pump spinning at maximum efficiency rpm will produce a pressure head of around 30-40psi in the engine block and head when water flow out of the head is limited by thermostat or restrictor plate. This pressure packs coolant around the top of the cylinders and around combustion chambers to carry away combustion heat and stop an insulating blanket of gas bubbles forming in these areas."
If you want to read the rest then buy the book!
He also goes on to say that he does under-drive the pumps sometimes, although this is all relative to the "maximum efficiency zone of 4-6krpm" I doubt you know that for your pump.
I like the book, I can't say his physics is up to scratch. For example in the introduction he says:
"Take the laws of gravity or the day/night cycle as the earth rotates around the sun."*
Which didn't inspire confidence. But he is good at citing evidence of doing things which I like.
Matt
*Obviously the earth rotates on its own axis causing the day night cycle. Rotation around the sun takes a year!
Of course you could always bin the pump and use an electric item to feed via a fanimold into the core plug holes! Lots of advantages if you have the
time and engineering skills!
quote:
Originally posted by britishtrident
Absolute Balderdash
40 psi from car water pump --- had me rolling about the floor.