Water Pump Functionality - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 08-14-2012, 11:02 AM
64Joker's Avatar
64Joker
 
Last photo:
Join Date: Mar 2005
Location: Nor Cal.
Posts: 263
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Water Pump Functionality

Hypothetically, if the thermostat does not open until 185 degrees, and the water pump works continuously prior to the thermostat opening,what prevents the water in the radiator to flow out and empty into the engine prior to the engine warming up?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 08-14-2012, 11:09 AM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls/Suncrest, WA
Posts: 5,259
Wiki Edits: 9

Thanks: 106
Thanked 133 Times in 124 Posts
The radiator inlet is blocked by the thermostat being closed. It's a closed system, no air, so nothing is being replaced or moving in or out of the radiator.
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 08-14-2012, 01:48 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,925
Wiki Edits: 0

Thanks: 4
Thanked 475 Times in 406 Posts
Quote:
Originally Posted by 64Joker View Post
Hypothetically, if the thermostat does not open until 185 degrees, and the water pump works continuously prior to the thermostat opening,what prevents the water in the radiator to flow out and empty into the engine prior to the engine warming up?
The bypass routes coolant around the thermostat but not through the radiator. This allows the coolant to circulate around and around inside the block and heads warming the coolant while leveling the internal metal temperatures much faster than if it always went through the radiator. It also prevents dead heading the pump.

Everybody's engine does this in some manner of design. Chevrolet's system routes from the return passages at the front of the intake to the heater core if not equipped with air-conditioning and through a 3 way valve that shunts coolant around the heater core when the AC is on so it doesn't have to cool the heated heater core. The return is from either the heater core for non AC models or the three way valve if it has AC to the suction side of the pump. The return is classically into a fitting on the top of the pump that feeds to the impeller inlet but there some other arrangements where the return hose feeds into the pump inlet side of the radiator tank or into a tee of the pump inlet hose. Everybody uses some configuration of a system similar to this. Some isolate the heater circuit from the bypass running the bypass hose directly from the intake return sourced behind the thermostat into the pump, Ford and Chrysler are examples of this arrangement.

The purpose besides providing faster cabin heat on cold days is to prevent hot spots from forming inside the engine and eliminate pump cavitation before general circulation starts with opening the thermostat. Hot spots mostly form around the exhaust seats and spark plugs; the metal immediately around these parts can become so hot they boil the coolant while everything else is cold. When this happens the hot metal tries to expand with the increasing temperature but is trapped by the colder metal surrounding the hot area, this can and does lead to cracking the casting. Keeping a circulation prevents the formation of local hot spots while the general warming of the circulating coolant tends to level the temperature throughout the castings so hot spots aren't trapped when surrounded by the cooler metal further away from the concentrated heat source.

In terms of cavitation; when the pump is dead headed, it beats the coolant into froth. Bubbles do not offer any cooling to hot engine parts, they only block flow and encourage further localized overheating. Additionally, the froth within the impeller beats on it shock loading the pump shaft, its bearings and seal all of which reduces the life span of these components.

There are those who argue that the constant flow of hot coolant into the mainstream after the thermostat opens contributes to overheating. The engineers that designed this system took that into account. Actually the LT1/4, the LS engine series and most other current production engines not to mention those of heavy trucks and equipment have for many years if not decades used a two part thermostat to feed hot coolant from the engine into cold coolant from the radiator to develop a tightly controlled temperature within the engine for best power and maximum efficiency. The modern Mustang V6 couldn't get to 300 horsepower and 30 miles to the gallon with many tricks this being one of them. I would suggest that overheating problems are better solved with not under diving the pump on street engines, and using a clean and properly sized radiator along with adequate fans and shroud to pull air over the entire core surface.

For straight up competition engines the thermostat is often eliminated as it can become a potential failure item that will take you out of the race. So a simple restrictor is often used to manage the full power operating temperature, which usually proves to be more than necessary cooling at slower speeds. This also eliminates the external plumbing of the bypass system without incurring the problems of no circulation as would happen with no bypass and having a thermostat that is closed when the engine is cold. The restrictor will cause the engine to be slow in initially warming up and the temp will tend over a wide range between idle and screaming around the track. This is less of a problem for racers as they are in the engine for maintenance a lot and the big time racers are using after-market castings which whether iron or aluminum are much more robust than is OEM production hardware.

Bogie
Reply With Quote Quick reply to this message
The Following User Says Thank You to oldbogie For This Useful Post:
cobalt327 (08-15-2012)
  #4 (permalink)  
Old 08-14-2012, 03:54 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,901
Wiki Edits: 0

Thanks: 3
Thanked 65 Times in 58 Posts
Bogie I always love your replies, they are like reading a short book. You take your time to go indepth so people understand better. Very good!!!!!
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 08-14-2012, 03:56 PM
bigdog7373's Avatar
Of course it's fast
 
Last photo:
Join Date: May 2010
Location: florida
Posts: 2,673
Wiki Edits: 0

Thanks: 13
Thanked 49 Times in 49 Posts
Bogie always has the best answers
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 08-14-2012, 07:11 PM
bondo's Avatar
Member
 
Last photo:
Join Date: Nov 2002
Location: Chaumont Bay N.Y.
Posts: 960
Wiki Edits: 0

Thanks: 7
Thanked 15 Times in 15 Posts
Quote:
Originally Posted by bigdog7373 View Post
Bogie always has the best answers
Ayuh,.... I'll say,.... Even when Bogie is talkin' 'bout, what I know about,...

I learn something....
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 08-14-2012, 07:27 PM
bigdog7373's Avatar
Of course it's fast
 
Last photo:
Join Date: May 2010
Location: florida
Posts: 2,673
Wiki Edits: 0

Thanks: 13
Thanked 49 Times in 49 Posts
Quote:
Originally Posted by bondo View Post
Ayuh,.... I'll say,.... Even when Bogie is talkin' 'bout, what I know about,...

I learn something....
Exactly. I always read his posts start to end. Learn something new every time!
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 08-15-2012, 08:51 AM
64Joker's Avatar
64Joker
 
Last photo:
Join Date: Mar 2005
Location: Nor Cal.
Posts: 263
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
"Not under diving the pump"

Quote:
Originally Posted by oldbogie View Post
I would suggest that overheating problems are better solved with not under diving the pump on street engines, and using a clean and properly sized radiator along with adequate fans and shroud to pull air over the entire core surface.
Bogie
What does "Not under diving the pump" mean?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 08-15-2012, 09:29 AM
bigdog7373's Avatar
Of course it's fast
 
Last photo:
Join Date: May 2010
Location: florida
Posts: 2,673
Wiki Edits: 0

Thanks: 13
Thanked 49 Times in 49 Posts
Quote:
Originally Posted by 64Joker View Post
What does "Not under diving the pump" mean?
Pump spins at least the speed of the crank
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 08-15-2012, 10:55 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,925
Wiki Edits: 0

Thanks: 4
Thanked 475 Times in 406 Posts
Quote:
Originally Posted by 64Joker View Post
What does "Not under diving the pump" mean?
Under-driving in place of under-diving, seems the spell checker looks at incorrect spellings but doesn't fix the wrong word I used for the one I was thinking. I hate that in an otherwise smart machine.

Under-drive pulleys are used with competition engines to reduce the power extraction the pump takes from the crankshaft. The power curve on the pump is such that power used is a geometric function of RPM (goes up in powers like doubling the RPM squares, or quads the power extracted) so at 6500 RPM you can be looking at 15 to 20 horses just to spin the pump. Additionally the pump output, while not growing quite so much as the power extraction, does start to output more coolant through the system than is needed at high RPMs to keep the engine temp stable. So without a thermostat or suitably sized restrictor it over cools the engine in addition to taking a lot of power from the crankshaft.

Taking these two events, it then becomes advantageous to slow the pump down which reduces the power extraction from the crank and does not force a situation where more coolant is being pumped than is necessary to maintain proper temperature. A win-win, how often do you see that?

This, however, does not work on the street in-so-far as moderate highway cruise speed and RPMs in the range of 2000-3000 are concerned. Under-drive pulleys will lead to insufficient cooling in these street settings, and like I said above, except at very high RPMs the power extraction of the pump is almost incidental. Of course one alternate solution is to use a high flow pump along with under-drive pulleys, but since very few aftermarket makers and sellers of these pumps provide numerical data compared to the OEM pump output and drive speeds, buying this stuff can lead you down a merry path of spending a lot of money to get unknown to incorrect results. Which is why for a street engine; I always recommend staying with what the factory puts on the engine unless you have numeric data, not making engineering decisions on advertising superlatives.

Bogie

P.S. Back in the good old days of NASCAR level stockcar racing when much of the equipment was in fact stock and modified for the peculiar needs of racing. It was common to control power extraction and coolant delivery of the pump at high RPMs by not only slowing it down with under-drive pulleys but, also, grinding the impeller blades down. Needless to say when a caution yellow or stop red flag came out these engine immediately puked coolant and overheated.
Reply With Quote Quick reply to this message

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Timing cover, water pump, fuel pump, etc HELP kingofny1997 Engine 3 06-07-2012 06:46 AM
SBC Long water pump or short water pump? johnnnz Engine 28 08-21-2011 01:20 PM
short water pump vs long water pump Studedean Engine 9 07-20-2011 03:38 PM
SBC short water pump vs long water pump and other questions Jag Daddy Engine 9 04-02-2004 09:29 AM
power steering from long water pump to short water pump kellyem Suspension - Brakes - Steering 7 02-22-2004 07:22 PM


All times are GMT -6. The time now is 03:44 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.