Boost is fairly simple to understand - it is related to pumped flow rate measured in CFM - volume - not very accurate, and Mass - weight, as related to air density, which is highly accurate.

If air was sold at a world-standard rate of $15.00 per cubic foot - $1.00 per pound of atmospheric pressure - the guy buying air in the Sahara would really be getting ripped off compared to the guy buying air in Antartica.

The Antartican's air-can would have a lot more air in it for his 15 bucks.

1cuft of summer air weighs less than 1cuft of winter air.
Hot air expands, becomes thinner, less dense - lighter.
Cold air contracts, becomes thicker, more dense - heavier.
Air pressurized greater than atmospheric pressure becomes more dense.

Flow rate measured in Cubic Feet per Minute CFM can be very inaccurate because of that physical law(s).
You can prove this with a simple, but dangerous, experiment -

First - tell the significant other there's a 50%off sale down at (fill in the local emporium, here).
This will remove most of the danger.

Take a clean, empty one-gallon metal can - paint thinner, gasoline, etc. - with a good sealable cap, outside and fill it with atmosphere.

Be very careful, here, to immediately cap the can off when filled, so as not to cause any ecological spills.
We don't want any of this stuff on the ground, or the carpet\flooring in your house, right?

Now, while 'the other' is gone shopping, place the filled can into the freezer for a period of time commensurate with accomplishing the experiment, and allowing for observation, summation, and removal of all evidence before the 'return'.

When you hear the audible 'carump!' from inside the freezer, the experiment is mature, whereupon removal and observation of the can will reveal the somewhat mis-shapen, distorted can walls, caused by the cold-contracted air within.

Had you placed the can on a super-accurate digital scale at the start of the experiment, placing the can on the scale at this time would have shown the reduction in volume did not reduce the weight by volume.

Don't believe it?

Here's a pop quiz -
Which weighs more - a pound of lead or a pound of feathers?

Ok, looking over you guys shoulders, I see a number of you immediately circled 'pound of lead'.

So, since this is an 'all pass - none fail' curriculum, I'll restate the question -

Which has more volume?
And no, I'm not talking how much noise it makes when it hits the floor.

How much space or area - volume - does it occupy on your bench?

One (1.0) pound of lead is about the size of a golf ball.

I'm passing out boxes of four distinct sizes. Don't open them - just observe the relative dimensions, and the weight of each.
You can pass them around for weight-to-volume comparison.

I filled the boxes on an electronic digital scale, so the tare is accurate, to within a gnat's a(nkle)ss.

You guys with the two cubic foot boxes have exactly one pound of feathers inside.

You guys with the one cubic foot boxes have exactly one pound of feathers inside.

You guys with the six cubic inch boxes also have exactly one pound of feathers inside.

And whoever has the two cubic inch golf ball sized 1lb box - whatever you do, DO NOT UNTIE THE KNOT in that 60lb fishing line!

The 1lb of feathers was poured into 2cuft box till it was full.

Took a little pressure to get 1lb of feathers in the 1cuft box.

Required more pressure for the 1/2cuft box, much, much more for the 2cuin box.

Boost is taking that large original volume of air and putting it into smaller boxes, which can then be multiply stacked into that original volume.

We get the same volume, but much more weight.

And oxygen, folks, has definite weight per unit volume of air.

Which is why racers, aircraft, ships, locomotives, etc, use weight to calculate fuel consumption and air flow required to make power.

You won't hear an airline pilot pull up to the pump and ask for "a hunnerd gallons in that back tank, and check the pressure on that middle tire - it feels mushy".

Nope - he signs for a 15,000lb load of fuel, which he factors in with x-number of pounds of air, needed to make such-and-such thousands of pounds of thrust, all required to get his plane to Cleveland.

What's the relevence, you say?

Your ~400cuin 6.5L Diesel V8 engine is design-limited to 3500rpm - it pumps air at ~400 cubic feet per minute at 3000rpm, all day long.

(As an aside - a Buick 3.8L granny motor pumps nearly identical flow rate, at ~400cfm.)

That's 3000rpm, and that's ~400cfm, and that is ALL it will ever pump at 3000rpm.

You can add Slick-Stuff, STP, Water-Wetter, teflon oil, cetane-booster, owl snot, whatever, but it can only displace - pump - 400cfm at that rpm - written in stone.

Smokey, Grumpy, Cale, Richard - cain't help ya, folks.

Snake, Big Daddy, Connie - guys that get all dressed up to drive 1320 feet - no help, here.

Put a turbocharger on it - still only pumps ~400cfm.

You could install the turbocharger off the TITANIC - with a skajillion cfm capability - on this motor, and that huge turbocharger will only output 400cfm into this motor.

Fortunately for us, if we could power the turbine on that monster with the low-volume exhaust output of the 6.5L, that large cfm capability could be used to make power.

How?

If the flow rate output of the compressor - turbocharger - exceeds the flow rate thru-put of the target device - the 6.5L turbomotor - that excess flowrate input will stack up in the engine intake tract as pressure.

And pressure makes little boxes outta big boxes.

If one big box of air can burn one tablespoon of fuel, then that same box full of 10 little boxes of air can burn 10 tablespoons of Diesel fuel.

See - it's the weight we're concerned with, not the size.

400cfm at 1psi vs 400cfm at 10psi - more flowed weight at same flowed volume.

That's my story and I'm stickin' to it...............



Oh, yeah - the Buick granny motor? It's cranking 6000rpm to make ~400cfm.

Only three ways to make more power, folks -

Increase engine displacement at same rpm - bore and\or stroke

Increase rpm - 6.5L makes ~400cfm at 3000rpm, Buick 3.8L makes same at 6000rpm
6.5L would make ~800cfm at 6000rpm

Increase input pressure - Baro flows x-lbs\minute, 3x-baro flows 3x-lbs\min
Simplest. Easiest.

What's more - we already got it!

More Power to ya,folks........

Simple terms for idiots like me. Thank you.

Who is Tom?

Snake, Big Daddy, & Connie.... 1320 ft.

Where is all this back-pressure you're always talking about.

How inefficient is my GM8? Define Inefficiency.

Natural Aspiration is so much easier.

Thanks again Wilson. Er... JD

Thanks Billman - I had a quarter of 5000ft in mind - I have to round off to make the numbers work.

And, as you know - that back-pressure is between the valve and the turbine.
Don't plumb and gage it - it'll scare you - 22psi at 8psi Boost, and climbing.

Another slip of the (?)mind - had something on about Tom Petty and the Heartbreakers, today - sorta confused him with Richard Petty and the Pole breakers.......eeep!

All corrected, now.

Are you talking Mr. Wilson, next door to Dennis the menace?;)

Billman,

Who is Tom?

Snake, Big Daddy, & Connie.... 1320 ft.

That would be Drag Raccers.. Don The Snake Prudhomme, Tom The Mongoose MCEwen, Don Garlits, and Connie Calletta... the Were some of the Fastest NHRA drivers back in there day.. hence the 1320... it a 1/4 in feet

Pete

"Hidy-Ho Neighbor!"

Ask TD...

Ah hem, here we go again. . .:D 400 CFM is correct, in displacement. That is displacement, at a given rpm. 400 CFM could be referred to as the "box." How much air ya jam in de box, well, that's when ye ole boost gauge goes up.

We go throught the same thing with refrigeration compressors. They will give you a given CFH. Cubic Feet per Hour. It is a fixed number, given a fixed RPM that it's operating at for that hour. Now, the next set of numbers that comes in conjuction with the rating of that compressor is the mass flow rate. That gives you how much refrigerant is moving throught that compressor in that given hour. Change the suction pressure and the head pressure, your mass flow rate changed drasticly. Now, just transmogrify that little ditty over to de 6.5 "compressor" and you get the idea.

Yes, you are very right, 400 cfm no matter what, in displacement. Change the pressures coming into the engine, then your "mass flow" will change as well, resulting in the different numbers of "pounds" of air wieght wise. That's why when the turbo goes on holiday, your smilage drops off the face of the earth. Less mass flow through your "compressor" Less air. Know what I mean jelly bean?:)

Yep - considering that 400cfm is only at 3000rpm.

What about 690rpm?

1750rpm? 2250rpm. 2570rpm.

All good numbers at idle and street speeds.

Always 400cuin displacement, but the flow rate - cfm - changes with crank rpm and piston speed, and loading, as does the Mass requirement.

Dynamics is a hard thing to pin down, don't it?;)

So... lets talk about increasing that pressure on a 6.5L with a PS turbo, IC and lowering compression to 20:1, increasing the valve duration by ~15* intake and exhaust toward the overlap with a new cam. Wouldn't holding the valve open longer on the intake and having a larger compressor and condensor on the airpump(6.5L) increase the wieght of O2 burned per sec not to mention the O2 that is pushed through the CC during overlap?

No - because fuel is directly injected, not 'flowed' in as part of the air charge.

Kick up the fuel rate, the Boost pressure goes up accordingly, under load.

Overlap is a considerable factor in direct injection, where the combustion chamber is in the piston crown - allows Boost pressure to blow the cylinder clean of previous combustion event left-overs, such that each air charge is fresh, un-diluted.
More power from total burn.

Don't work so well in idi engines. The a\m cam availability is limited, usually with only increased lift by grinding the base circumference, specifically for the n\a engines.

Pressurized engines are not quite so finikey (now, why doesn't that word look right?) about intake flow - it is exhaust flow - valve to turbine - that could stand some improvement.

Keep in mind - 6.5 is a low-rpm engine, with low exhaust energy.

Takes a third-degree black-belt twinkle-toes prima-donna to balance low exhaust energy with quck spool-up for low-rpm power - driveability, turbo-lag, upper low-rpm power.

Other than that - yeah, go ahead and experiment, see what you come up with on the P\S turbo.

Hmmm..... perhaps I should add propane injection automatically above 7 psi boost via pressure switch relay & LPG solenoid plumbed to 100 gal bed tank. I realize the DS-4 is maxing out at 275hp and can use some help on delivering more fuel. The stock grind on the cam has 50* between when the exhaust closes and the intake opens. With propane in the mix would it not benefit from increased duration on I/E considering it's taken in from the valving not injected? Wouldn't an increase in overlap duration help cool the exhaust/intake valves and CC and possibly increase the O2 content of the exhaust for emissions testing purposes? Would it make a difference if I lowered the compression with the .10" over head gaskets?

Boost is fairly simple to understand - it is related to pumped flow rate measured in CFM - volume - not very accurate, and Mass - weight, as related to air density, which is highly accurate.

If air was sold at a world-standard rate of $15.00 per cubic foot - $1.00 per pound of atmospheric pressure - the guy buying air in the Sahara would really be getting ripped off compared to the guy buying air in Antartica.

The Antartican's air-can would have a lot more air in it for his 15 bucks.

1cuft of summer air weighs less than 1cuft of winter air.
Hot air expands, becomes thinner, less dense - lighter.
Cold air contracts, becomes thicker, more dense - heavier.
Air pressurized greater than atmospheric pressure becomes more dense.

Flow rate measured in Cubic Feet per Minute CFM can be very inaccurate because of that physical law(s).
You can prove this with a simple, but dangerous, experiment -

First - tell the significant other there's a 50%off sale down at (fill in the local emporium, here).
This will remove most of the danger.

Take a clean, empty one-gallon metal can - paint thinner, gasoline, etc. - with a good sealable cap, outside and fill it with atmosphere.

Be very careful, here, to immediately cap the can off when filled, so as not to cause any ecological spills.
We don't want any of this stuff on the ground, or the carpet\flooring in your house, right?

Now, while 'the other' is gone shopping, place the filled can into the freezer for a period of time commensurate with accomplishing the experiment, and allowing for observation, summation, and removal of all evidence before the 'return'.

When you hear the audible 'carump!' from inside the freezer, the experiment is mature, whereupon removal and observation of the can will reveal the somewhat mis-shapen, distorted can walls, caused by the cold-contracted air within.

Had you placed the can on a super-accurate digital scale at the start of the experiment, placing the can on the scale at this time would have shown the reduction in volume did not reduce the weight by volume.

Don't believe it?

Here's a pop quiz -
Which weighs more - a pound of lead or a pound of feathers?

Ok, looking over you guys shoulders, I see a number of you immediately circled 'pound of lead'.

So, since this is an 'all pass - none fail' curriculum, I'll restate the question -

Which has more volume?
And no, I'm not talking how much noise it makes when it hits the floor.

How much space or area - volume - does it occupy on your bench?

One (1.0) pound of lead is about the size of a golf ball.

I'm passing out boxes of four distinct sizes. Don't open them - just observe the relative dimensions, and the weight of each.
You can pass them around for weight-to-volume comparison.

I filled the boxes on an electronic digital scale, so the tare is accurate, to within a gnat's a(nkle)ss.

You guys with the two cubic foot boxes have exactly one pound of feathers inside.

You guys with the one cubic foot boxes have exactly one pound of feathers inside.

You guys with the six cubic inch boxes also have exactly one pound of feathers inside.

And whoever has the two cubic inch golf ball sized 1lb box - whatever you do, DO NOT UNTIE THE KNOT in that 60lb fishing line!

The 1lb of feathers was poured into 2cuft box till it was full.

Took a little pressure to get 1lb of feathers in the 1cuft box.

Required more pressure for the 1/2cuft box, much, much more for the 2cuin box.

Boost is taking that large original volume of air and putting it into smaller boxes, which can then be multiply stacked into that original volume.

We get the same volume, but much more weight.

And oxygen, folks, has definite weight per unit volume of air.

Which is why racers, aircraft, ships, locomotives, etc, use weight to calculate fuel consumption and air flow required to make power.

You won't hear an airline pilot pull up to the pump and ask for "a hunnerd gallons in that back tank, and check the pressure on that middle tire - it feels mushy".

Nope - he signs for a 15,000lb load of fuel, which he factors in with x-number of pounds of air, needed to make such-and-such thousands of pounds of thrust, all required to get his plane to Cleveland.

What's the relevence, you say?

Your ~400cuin 6.5L Diesel V8 engine is design-limited to 3500rpm - it pumps air at ~400 cubic feet per minute at 3000rpm, all day long.

(As an aside - a Buick 3.8L granny motor pumps nearly identical flow rate, at ~400cfm.)

That's 3000rpm, and that's ~400cfm, and that is ALL it will ever pump at 3000rpm.

You can add Slick-Stuff, STP, Water-Wetter, teflon oil, cetane-booster, owl snot, whatever, but it can only displace - pump - 400cfm at that rpm - written in stone.

Smokey, Grumpy, Cale, Richard - cain't help ya, folks.

Snake, Big Daddy, Connie - guys that get all dressed up to drive 1320 feet - no help, here.

Put a turbocharger on it - still only pumps ~400cfm.

You could install the turbocharger off the TITANIC - with a skajillion cfm capability - on this motor, and that huge turbocharger will only output 400cfm into this motor.

Fortunately for us, if we could power the turbine on that monster with the low-volume exhaust output of the 6.5L, that large cfm capability could be used to make power.

How?

If the flow rate output of the compressor - turbocharger - exceeds the flow rate thru-put of the target device - the 6.5L turbomotor - that excess flowrate input will stack up in the engine intake tract as pressure.

And pressure makes little boxes outta big boxes.

If one big box of air can burn one tablespoon of fuel, then that same box full of 10 little boxes of air can burn 10 tablespoons of Diesel fuel.

See - it's the weight we're concerned with, not the size.

400cfm at 1psi vs 400cfm at 10psi - more flowed weight at same flowed volume.

That's my story and I'm stickin' to it...............



Oh, yeah - the Buick granny motor? It's cranking 6000rpm to make ~400cfm.

Only three ways to make more power, folks -

Increase engine displacement at same rpm - bore and\or stroke

Increase rpm - 6.5L makes ~400cfm at 3000rpm, Buick 3.8L makes same at 6000rpm
6.5L would make ~800cfm at 6000rpm

Increase input pressure - Baro flows x-lbs\minute, 3x-baro flows 3x-lbs\min
Simplest. Easiest.

What's more - we already got it!

More Power to ya,folks........I wll give you something to think about. The formula for CFM also takes into account the specific density of air. So a true CFM is referenced at sea level pressure or 14.7 psi.

SCFM or CFM = 14.7 PSI/ 68F/ 36% RH.

So if any of the above change CFM will change as well.

You might check the difference in SCFM and ACFM........

I think we are getting down to the heart of the matter here. Displacement doesn't equal CFM per se. Displacement is a measurement of volume, whereas the CFM gets a little bit fuzzy. 400 CFM is it, but what you can jam into that 400 cfm is what counts. Cubic foot of what? Air at 14.7 psia, or at 29.4 psia? It's still a cubic foot, just what's in that cubic foot, know what I mean?

"See - it's the weight we're concerned with, not the size"............