My rant about mods..
Senior Member
Joined: Nov 1999
Posts: 525
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From: Bryan, Texas
And when the engine is not running neither is the oil flow, meaning that the crank and rods and pistons are not "floating"... so yes, that vacuum has no effect on an engine not running. But it WILL have a better effect on a running engine... probably not much tho...
The effort to rotate the engine drops significantly when it's running... else there is NO way we could get enough efficiency to push a 4000 # truck.
"Vacuum"... and BTW... "Damn"...
Unless you are restricting the flow of water.... then... "Dam"
The effort to rotate the engine drops significantly when it's running... else there is NO way we could get enough efficiency to push a 4000 # truck.
"Vacuum"... and BTW... "Damn"...
Unless you are restricting the flow of water.... then... "Dam"
Member
Joined: Oct 2002
Posts: 63
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From: Connecticut
The point i am trying to make is the actual vacuum is not sucking or pulling the piston upwards, it is clearing the way fo the piston to come up more easily. The vacuum is in no way strong enough to actually pull on a piston with any measurable amount.
In other words,if a dust buster has enough vacuum to pull out the spent gasses, a monster shop vac isn't gonna help you any because its not pulling the piston up, its evacuating spent gasses.
In other words,if a dust buster has enough vacuum to pull out the spent gasses, a monster shop vac isn't gonna help you any because its not pulling the piston up, its evacuating spent gasses.
Last edited by GN1270; Oct 25, 2002 at 07:45 PM.
Member
Joined: Oct 2002
Posts: 63
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From: Connecticut
Dam was a typo i still spelled vacuum wrong after all that
Look at how bad this damn keyboard is. Itskips letters, spaces etc, an it only des it when i typeon message boards. I'm not gonn alter this. Anyone else have tis problem??? Except for vacuum, i know how to spell I haveto go back and do quick spell checksever time. Sometimes it works with no problems and sometimes it just plain sucks!! Now its working fine. After 10 months of it,i'm starting to get usd to it.
i still spelled vacuum wrong after all that Look at how bad this damn keyboard is. Itskips letters, spaces etc, an it only des it when i typeon message boards. I'm not gonn alter this. Anyone else have tis problem??? Except for vacuum, i know how to spell
I haveto go back and do quick spell checksever time. Sometimes it works with no problems and sometimes it just plain sucks!! Now its working fine. After 10 months of it,i'm starting to get usd to it.
Senior Member
Joined: Jun 2000
Posts: 919
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From: At the Gas Pump!
MM&FF also got a bunch of HP when they bolted the bassini on the Fridge...I think they just want to sell parts. That being said, the Cobras' exhaust were so restrictive the engines were running hot....this may be an example of taking any one part of the setup to the extreme.
GN1270, have you got an early start on the weekend, huuummmm, perhaps a few beers?
GN1270, have you got an early start on the weekend, huuummmm, perhaps a few beers?
Senior Member
Joined: Dec 2000
Posts: 1,514
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From: Auburn Wa
Gawd you guys are killin me with this vacuum crap.
If an exhaust system is lucky enough to be designed right and IF the cam and everything else is right, the exhaust will make enough vacuum to help jump start the intake flow. On a race engine that is tuned properly the exhaust out flow will help draw in the intake flow.....you know why? Cause both valves are open at the same time. It is called overlap and is a very usefull tool in a RACE engine. It doesn't even apply to lightings cause the lightning motor is so short cammed it doesn't have any overlap to speak of.
Pulling the piston up with vacuum.....were the hell did that come from.
One more thing.....Vacuum pumps on race engines are only there to keep the oil out of the combustion chambers. They work in conjunction with very low tentsion ring sets. The lack of ring tension is what really makes the power. A vacuum pump will also keep oil out of the valve guides so you have to be careful with them.
If you think that a vacuum pump works by pulling pistons down....well For every piston the goes down in and engine another one is going up. It is self cancelling.
Dale
If an exhaust system is lucky enough to be designed right and IF the cam and everything else is right, the exhaust will make enough vacuum to help jump start the intake flow. On a race engine that is tuned properly the exhaust out flow will help draw in the intake flow.....you know why? Cause both valves are open at the same time. It is called overlap and is a very usefull tool in a RACE engine. It doesn't even apply to lightings cause the lightning motor is so short cammed it doesn't have any overlap to speak of.
Pulling the piston up with vacuum.....were the hell did that come from.
One more thing.....Vacuum pumps on race engines are only there to keep the oil out of the combustion chambers. They work in conjunction with very low tentsion ring sets. The lack of ring tension is what really makes the power. A vacuum pump will also keep oil out of the valve guides so you have to be careful with them.
If you think that a vacuum pump works by pulling pistons down....well
For every piston the goes down in and engine another one is going up. It is self cancelling.Dale
Senior Member
Joined: May 2001
Posts: 1,030
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From: Fl/Tenn
Bad as L, you're right about the vac pump issue. This is why I bought mine:
Benefits of the Reher-Morrison Vacuum Pump Kit:
· Lowers crankcase pressure to minimize windage
· Improves ring seal for more power
· Allows use of low-tension piston rings for less friction
· Reduces blow-by, intake charge contamination and detonation
· Reduces oil leaks for lower maintenance and improved safety
Taken from my engine builders web site.
www.rehermorrison.com
Hmm, I wonder if I could put a street type pump on the L?
Benefits of the Reher-Morrison Vacuum Pump Kit:
· Lowers crankcase pressure to minimize windage
· Improves ring seal for more power
· Allows use of low-tension piston rings for less friction
· Reduces blow-by, intake charge contamination and detonation
· Reduces oil leaks for lower maintenance and improved safety
Taken from my engine builders web site.
www.rehermorrison.com
Hmm, I wonder if I could put a street type pump on the L?
Senior Member
Joined: Dec 2000
Posts: 1,514
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From: Auburn Wa
RS
I already have mine set up that way. I run the stock PCV setup with a .060 restriction in the tube going from the drivers side valve cover to the MAF boot.
It puts a nice little vacuum on the crankcase, I actually may have a little to much vacuum on it right now. Sometimes the the air being pulled in thru the dipstick tube makes a little noise.
But it works great......try it.
Dale
I already have mine set up that way. I run the stock PCV setup with a .060 restriction in the tube going from the drivers side valve cover to the MAF boot.
It puts a nice little vacuum on the crankcase, I actually may have a little to much vacuum on it right now. Sometimes the the air being pulled in thru the dipstick tube makes a little noise.
But it works great......try it.
Dale
Junior Member
Joined: Jul 2003
Posts: 3
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Someone posted a link to this thread on Modularfords.com.
It is interesting that a similar thread was going over there simultaneously.
It seems that the guys from KB passed on to a forum member that LT's, and even headwork and cams were of limited value with the KB blower.
Anyway the thread is here:
http://www.modularfords.com/forums/s...&threadid=3619
Following is the text of my post related to this thread. It is from the second page over there. Note how similar it is to the first post in this thread:
Interesting?
JT
It is interesting that a similar thread was going over there simultaneously.
It seems that the guys from KB passed on to a forum member that LT's, and even headwork and cams were of limited value with the KB blower.
Anyway the thread is here:
http://www.modularfords.com/forums/s...&threadid=3619
Following is the text of my post related to this thread. It is from the second page over there. Note how similar it is to the first post in this thread:
Originally posted by JT
Ok, I have a theory. As some of you may know, I am an electrical engineer that works primarily as a mechanical engineer in hydraulics and pneumatics. Working with hydraulics and pneumatics, I am very familiar with pumps and their characteristics. Both the Eaton and the KB are air pumps. The KB is may be better characterized a compressor. Both are commonly referred to as "positive displacement".
A positive displacement , or fixed displacement pump, pumps a given volume based on it's speed and inlet conditions. The outlet pressure has a very small effect on the volume of whatever a particular fixed displacement pump is pumping, be it air, hydraulic fluid, etc. The pumps that I am most familiar with, that are similar in design to the Eaton and KB, typically have a volumetric efficiency change of a few percent when going from low pressure, say 100 psi to high pressure, like 3000 psi.
Now the blowers we are talking about, especially the Eaton appear to me to be definatly more "leaky". Especially the Eaton with the roots design being prone to reversion. By that I mean, a few psi of outlet pressure should make at least some change in volumetric efficiency. So headers, I would guess, in theory should make some difference, since they should unplug the oulet of the engine, which I would think would lower the pressure at the inlet for a given flow. Why this doesn't seem to show up as significant power, I don't know.
The KB, is a screw compressor. The screw compressors I am familiar with used in drilling and mining applications, are happy to run at, and are very efficient up to 300-500 PSI. This leads me to believe that the KB volumetric efficiency doesn't change much over the range of a couple of psi.
Which to me means, if there is a little more pressure in the intake tract through unported heads, or past valves that aren't as open as they would be with a bigger cam, or due to slightly more pressure on the exhaust side due to the factory log manifolds, it doesn't matter. That compressor will move the volume of air based on the speed it is turning and it's displacement. The same, or close to the same amount of air makes it to the combustion chamber, and the result is the same power output.
I do see some potential gain because a blower running at a lower outlet pressure needs less power to turn. I guess, at least according to the KB guys, that amount of power isn't real noticeable.
Ok, I have a theory. As some of you may know, I am an electrical engineer that works primarily as a mechanical engineer in hydraulics and pneumatics. Working with hydraulics and pneumatics, I am very familiar with pumps and their characteristics. Both the Eaton and the KB are air pumps. The KB is may be better characterized a compressor. Both are commonly referred to as "positive displacement".
A positive displacement , or fixed displacement pump, pumps a given volume based on it's speed and inlet conditions. The outlet pressure has a very small effect on the volume of whatever a particular fixed displacement pump is pumping, be it air, hydraulic fluid, etc. The pumps that I am most familiar with, that are similar in design to the Eaton and KB, typically have a volumetric efficiency change of a few percent when going from low pressure, say 100 psi to high pressure, like 3000 psi.
Now the blowers we are talking about, especially the Eaton appear to me to be definatly more "leaky". Especially the Eaton with the roots design being prone to reversion. By that I mean, a few psi of outlet pressure should make at least some change in volumetric efficiency. So headers, I would guess, in theory should make some difference, since they should unplug the oulet of the engine, which I would think would lower the pressure at the inlet for a given flow. Why this doesn't seem to show up as significant power, I don't know.
The KB, is a screw compressor. The screw compressors I am familiar with used in drilling and mining applications, are happy to run at, and are very efficient up to 300-500 PSI. This leads me to believe that the KB volumetric efficiency doesn't change much over the range of a couple of psi.
Which to me means, if there is a little more pressure in the intake tract through unported heads, or past valves that aren't as open as they would be with a bigger cam, or due to slightly more pressure on the exhaust side due to the factory log manifolds, it doesn't matter. That compressor will move the volume of air based on the speed it is turning and it's displacement. The same, or close to the same amount of air makes it to the combustion chamber, and the result is the same power output.
I do see some potential gain because a blower running at a lower outlet pressure needs less power to turn. I guess, at least according to the KB guys, that amount of power isn't real noticeable.
JT
Last edited by jtfx6552; Jul 17, 2003 at 09:48 PM.
Senior Member
Joined: Mar 2001
Posts: 150
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From: Westminster, Md USA
It is relatively simple. A presurized intake removes the need for a finely tuned intake. It guaranties a high volumetric efficeincy. In a normally asperated engine the intake and exhaust play a big part in the picture. If the intake and exhaust do not work in harmony with the intake manifold, valves, cam, heads, exhaust etc then you do not get cylinder fill and clean burn and exhaust scavanging and therefore low efficiency and low power. With a supercharger and turbo the intake and to a big degree the exhaust do not matter much. if the cylinder is full of a charge you only need to burn it completely (without detonation) and get rid of it (exhaust) to make big power. The only downside to a supercharger is heat and the power needed to spin it must be overcome. I know this is somewhat simplified, but it is late and I have done this quickly off of the top of my head. I used to deal with this quite a bit when I built a few turbo bikes in from 79 to 82.
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Joined: Aug 2001
Posts: 1,248
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From: Northern VA
God I loved re-reading this thread... 
Found it in the archives, and still learned something new (or at least put back in my head what already fell out)
Does anyone else (or the same parties) have anything else they'd like to add to this discussion, now that we have another year's worth of experience (and more data points w/ LT's, etc) under our collective belts?
Found it in the archives, and still learned something new (or at least put back in my head what already fell out)Does anyone else (or the same parties) have anything else they'd like to add to this discussion, now that we have another year's worth of experience (and more data points w/ LT's, etc) under our collective belts?
