Hey Pickless.... Explain this one...

[KaiserBill]

You never did actually refute my claim that CFM is far more important than Manifold Pressure.... So, I ask you this can you disprove these simple facts:

Let's say I have a turbo/super charger hell a monkey with large lungs pushing the following air into my intake under the following coniditions:

Manifold Pressure- 1.0 PSI gauge
Normal Volumetric flow at this rate is 400CFM
Air Temperature- 73F ambient outside
Let's say that charge entering the intake is 130 degrees after the intercooler.
One turbo is increasing this to 450CFM
and there other is increasing it to 475 CFM...

Why will my x turbo at 475CFM flow rate with increase the engines ability to produce mor epower at the same rpm or not when compared to the turbo y flowing 450CFM?

[UselessPickles]

Actually, I already did refute your claim. At least twice. The situation you propose is nonsense. I'll try one more time.

It is physically impossible for the same engine, at the same speed, and same manifold pressure, and same air temp, to consume air at a different CFM. If the engine cannot consume air at a different CFM, then it impossible for two different superchargers to supply air at different CFM given all else also being equal as you propose.

There also needs to be clarification of what you mean by CFM. CFM specifies the volume flow rate. That's missing a lot of crucial info. What matters is the mass flow rate, and that depends on the pressure and temperature of the air. So are we talking CFM of atmospheric air flowing into and through the the entire supercharger+engine system, or are we talking about the CFM of manifold air (at boosted pressure and temperature) being ingested by the engine? Let's not get hung up on answering this. I'm just pointing out that CFM by itself is ambiguous.

1) For the rest of this post, I will specify the context whenever I mention a volumetric flow rate to avoid ambiguity.

2) Let's also, for simplicity, assume that the engine is perfectly efficient at pumping air. Each cylinder displaces 0.6L of volume, so let's assume it consumes exactly 0.6L of air from the manifold with each complete cycle. This means that, whatever pressure/temperature the air is in the manifold, 0.6L of that air at that same pressure/temperature fills the cylinder.

3) For the sake of working with real numbers (and easy calculations), let's assume we are looking at the engine running at 2000 rpm.
So we've got 2000 / 2 complete cycles per minute of 6 cylinders consuming a total of 3.6L of air from the manifold with each complete cycle.
3.6 * 2000 / 2 = 3600 L/m of manifold pressure/temperature air being consumed by the engine.

4) For simplicity of calculations again, let's say that ambient pressure is 14.7 psi, and the superchargers in question are doubling the pressure, giving us 14.7 psi boost at 2000 rpm.

5) For simplicity of calculations yet again, lets assume no increase in temperature due to the compression. Your scenario assumes the same intake temp for both superchargers, anyway, so there's no difference in temperature to take into account between the two superchargers.

6) So... with this simplified hypothetical situation, I think you can agree that the engine is consuming 3600 L/m of intake manifold air. That intake manifold air is boosted to double atmospheric pressure, which means it converts to double the volumetric flow rate of air from the atmosphere: 7200 L/m. This means that 7200 L/m of ambient temperature atmospheric pressure air is flowing through the supercharger, being compressed down to half the size, double the pressure.

7) Now let's say that you insist that while supercharger A is flowing that 7200 L/m, supercharger B is actually flowing 10% more air, or 7920 L/m from the atmosphere. The engine is still only consuming 3600 L/m of manifold air. If we again, for simplicity, assume no temperature change during the compression, that means that manifold pressure MUST be 7920/3600 = 2.2 times atmospheric pressure. (2.2 * 14.7) - 14.7 = 17.6 psi boost, compared to supercharger A's 14.7 psi boost.



CONCLUSION: The only way to get a different flow rate on the same engine, same engine speed, same amount of boost, and same ambient atmospheric conditions, is to have a difference in compressor/intercooler efficiency or different flow efficiency of intake piping that leads to a different intake temperature, causing a difference in density in the intake manifold.


BUT WAIT! THERE'S MORE!

But how much of a difference could there be due to temperature? Let's revisit the original situation that sparked this debate: 2000 rpms, RIPP vs Prodigy. Same amount of boost, but RIPP claims about 40% gain in torque compared to essentially zero gain demonstrated by Prodigy at the same engine speed, same boost levels. You proposed that a difference in CFM is probably the explanation. For this to be true, RIPP would need to be flowing approximately 40% more air (assuming difference in tuning is not a major factor... which is what you are assuming by claiming that difference in CFM is the major factor).

I have just demonstrated that the only way the CFM could be different is due to differences in intake temp. Let's see if it's possible for RIPP to have intake temps low enough to explain a 40% gain in flow rate...

According to my data logs, intake temps are only about 5-10*F above ambient around full throttle at 2000 rpms. So let's say 70*F ambient temps, intake temps are 80*F. The absolute best case (but practically impossible) scenario is that RIPPs intake temps have no increase over ambient temperature.

So it comes down to how much more air by mass per volume (aka, density) is there in the intake manifold at the same pressure but only comparing a difference of temperature between 70*F and 80*F?

Density of air is inversely proportional to temperature. But not in Farenheit or Celsius. In Kelvin.

70*F = 294 K
80*F = 300 K

So the density of air in the the manifold for Prodigy in this example is proportional to (1 / 300)
The density of the hypothetical best-case-scenario RIPP in this example is proportional to (1 / 294)

Since the pressure is the same, we can proportionally compare those numbers. To find out how much more air by mass is flowing through for the RIPP in this example, divide the proportional density values (RIPP / Prodigy):

(1 / 294) / (1 / 300) = 300 / 294 = 1.02 -> only 2% more air by mass for RIPP.

Or you could also call it 2% more CMF in relation to atmosphere. So yes, technically you were correct in saying the CFM could be different, but it can't possibly be different enough to explain the supposed 40% discrepancy between RIPP and Prodigy gains at 2000 rpm.

[KaiserBill]

Pickless....

The answer is more hp. It is actually a real world example. It was the first engine I ever turbocharged ( I was 13 or 14 at the time)-- a B&G 2-Cyclinder 25- 30hp gas engine with a carburetor-- I found a small turbocharger in a junkyard after searching and searching bought it as pullout unit and slapped it on to this 25-30hp gas engine... If I remember correctly the turbo produced about 450 CFM at 1-2 PSI manifold pressure. Then, I ported and polished the head of this engine and got about another 25CFM of flow from that at the same 1-2PSI manifold pressure. At 3600rpm I dyno-tested and it created at first about about 35-45hp and then with the increase in flow from the heads it created about 47-57hp at 3600rpm roughly-- if I remember correctly. I later blew it up using a nitro-methanol fuel mix from Model Airplane Engines and set the make-shift waste-gate I developed to make 5-10psi-- I didn't get to test the HP before I blew it up in the initial testing phase.

So, I know for a fact that CFM increases even small ones can really pay off big dividends in power. This is why people port and polish heads. I can take two engines port and polish the heads to clean up air flow and see massive power gains from N/A Engine! The same is true for a forced induction engine.

[UselessPickles]

Your anecdotal evidence involving "if I remember correctly" numbers is not proof of anything.

Your wide range of before/after hp numbers (35-45 hp and 47-57 hp) means that your hp gains from the port/polish could range anywhere from 4% to 63%. Your claimed increase in CFM is 5.5%, so I would believe that your HP gains were close to the low end of the possible 4% - 63% range.

And, as usual, what the hell does any of this have to do with the topic at hand? I fully refuted your claim with logic, physics, example calculations, etc. You have not challenged any bit of my explanation at all. Your response is essentially, "Oh yeah? Well I did things to an engine one time and it made some amount of gain in power with a very wide range of error in measurements!"

It's OK to admit you don't fully understand something and learn from it. This isn't a competition. Likewise, if you can provide any logical explanation at all for your claim that two different superchargers on the same engine, same engine speed, same boost pressure, same intake temps, could be flowing DIFFERENT amounts of air, I will seriously research it and maybe learn something new myself. So far, you have provided nothing remotely logical.

[UselessPickles]

BTW, just as an example of how useless your reported numbers are...

You claimed 35 - 45 hp before port/polish. That's 40 hp +/- 12.5%. That is a HUGE margin of error.

To illustrate this better, let's use the same margin of error for my Jeep: 370 hp +/- 12.5% = 324 to 416 hp.

I also question the validity of your methodologies involved in modifying, tuning, and properly measuring both hp and cfm before/after the port/polish back when you were 13, as well as your ability to precisely recall those numbers now. Purely anecdotal.

[KaiserBill]

I'll admit this-- Procharger makes many superchargers all operating at 38psi maximum boost. However, depending on the size of the unit and design application the maximum CFM at 38 PSI ranges from 1525CFM to 2700CFM. Some of these units have identical dimensions. The answer to why they develop different flow rates has to do with efficiency based on impeller design and the A/R ratio. So, like I first told you there isn't a linear relationship between boost and CFM or Lbs/Min in a turbo or a Supercharger always when you compare different models of units. You really need to know more about the specific unit and what application it used for.

https://www.procharger.com/sites/def...Specs-RACE.jpg

So, there you go... You can choose to believe Procharger's chart or not. I'll trust in my extensive library of engine theory and design books...

But , hey, it was fun while it lasted!

[KaiserBill]

Well, I packed the engine up in a van-- and brought it to a dynameter place a few towns over and we tested it out on a real engine dyno. So, the power was tested properly. I built the flow bench myself using instructions I found in an old copy of Popular Mechanics from the late 1970's. Remember Microfiche in the public library and then I took out every book I could on engine and turbo design. Plus, I grew up with Engineers and Tool and Die Makers! I was only kid in I knew of in school that had a working metal shop in his garage and could use a mill and lathe at age 14. So, I got help from my grandfather and older brother but, I basically made the engine...

Obviously, my tools were not top of the line when it came to flow bench work. But, the point of the story is that when in doubt make your engine flow more air! An engine is just a big air-pump with a series of explosions inside of it. The more effectively it pumps air in and mixes it with fuel the more power you get! Forced Induction like anything else in engine design is about pushing more air into the engine. The more air you flow at any given manifold pressure be it 14.7psi or 200psi will determine how much horsepower you really gain.

There is a reason why a NRE racing engine of 427cid can make a 1000hp on 7-8psi of manifold pressure has to do with way it handles air flow.

On a side note about your math-- 3.6L of air might be what engine's total capacity is-- but that is only theoretical you're VVT engines usually never get more than 92-95% Volumetric Efficiency in naturally aspirated form and that usually at higher rpm-- at low rpms it drops a bit so you might be down to 89-90% maximum efficiency from idle to 3000rpm... Which means that it is a lot easier to push more air into cylinder with less pressure than at 95% efficiency where you need more pressure to see higher hp gains.

[UselessPickles]

I'll admit this-- Procharger makes many superchargers all operating at 38psi maximum boost. However, depending on the size of the unit and design application the maximum CFM at 38 PSI ranges from 1525CFM to 2700CFM. ... So, like I first told you there isn't a linear relationship between boost and CFM or Lbs/Min in a turbo or a Supercharger always when you compare different models of units. You really need to know more about the specific unit and what application it used for.

Again, hilariously irrelevant.

Did I ever claim that, in general (among all possible engine/supercharger combinations), there is a linear relationship between boost and CFM? No!

Did I ever claim that, in general (among all possible engine/supercharger combinations), different supercharger/turbo units cannot be capable of producing different CFM at the same boost level? No!

Does ANYTHING about my claim and explanation in my first reply to this thread depend on these ideas that you have falsely attributed to me? No!

The only thing you are showing me here is that there are different size superchargers that are capable (when tested by themselves) of flowing different amounts of air at the same boost pressure. And different engines are capable of consuming air at different CFM, and therefore need properly matched superchargers. And that more CFM generally yields more power, regardless of boost pressure. This is no surprise! I have never said anything opposite of this!

I only say that it's impossible for two different superchargers to produce DIFFERENT CFM on the SAME engine, at the SAME boost levels, and the SAME intake temps. I further demonstrated that a reasonable difference in intake temp would not significantly alter the CFM. You have offered zero evidence against this.

Stay focused on the context of the situation you proposed in the first post. Different sized engines using different sized superchargers with the same boost, producing different CFM and different HP.... this is all completely irrelevant to your proposed situation.

So, there you go... You can choose to believe Procharger's chart or not. I'll trust in my extensive library of engine theory and design books...

The funny thing is... many of the things you say are individually correct. Your engine theory and design books are not wrong. The problem is, as usual, context and relevance. You fail to recognize the context in which your statements are true, and in what contexts your statements are irrelevant.

The individual facts you know are correct in some context. You just don't fully understand the contexts/reasons behind the facts you know. Memorizing/regurgitating facts is not enough. You need to understand the theory/relationships/context behind the facts, and how to properly interpret/apply them.

On a side note about your math-- 3.6L of air might be what engine's total capacity is-- but that is only theoretical you're VVT engines usually never get more than 92-95% Volumetric Efficiency in naturally aspirated form and that usually at higher rpm-- at low rpms it drops a bit so you might be down to 89-90% maximum efficiency from idle to 3000rpm... Which means that it is a lot easier to push more air into cylinder with less pressure than at 95% efficiency where you need more pressure to see higher hp gains.

Again, context and relevance.

We're not discussing whether or not the relationship between boost and power gains is the same throughout the RPM range. We're not discussing whether there's a linear relationship between boost and power gains, or CFM.

The context was whether or not two different superchargers on the SAME engine, at the SAME engine speed, at the SAME boost levels, and SAME intake temperature could possibly flow DIFFERENT amounts of air. Since the engine is the same, and it is the engine itself that determines its VE, the VE becomes irrelevant in the comparison.

The only way to change the amount of air flowing through an engine is to modify the engine to change its efficiency, or boost the pressure of the air going into the engine. We are talking about two of the same STOCK engines, so they will have the same VE as each other.

Show me how how two of the same engine, with the same displacement and VE, at the same speed, with the same manifold pressure/temperature, could possibly consume air at DIFFERENT rates.

[KaiserBill]

Again, hilariously irrelevant.

Did I ever claim that, in general (among all possible engine/supercharger combinations), there is a linear relationship between boost and CFM? No!

Did I ever claim that, in general (among all possible engine/supercharger combinations), different supercharger/turbo units cannot be capable of producing different CFM at the same boost level? No!

Does ANYTHING about my claim and explanation in my first reply to this thread depend on these ideas that you have falsely attributed to me? No!

The only thing you are showing me here is that there are different size superchargers that are capable (when tested by themselves) of flowing different amounts of air at the same boost pressure. And different engines are capable of consuming air at different CFM, and therefore need properly matched superchargers. And that more CFM generally yields more power, regardless of boost pressure. This is no surprise! I have never said anything opposite of this!

I only say that it's impossible for two different superchargers to produce DIFFERENT CFM on the SAME engine, at the SAME boost levels, and the SAME intake temps. I further demonstrated that a reasonable difference in intake temp would not significantly alter the CFM. You have offered zero evidence against this.

Stay focused on the context of the situation you proposed in the first post. Different sized engines using different sized superchargers with the same boost, producing different CFM and different HP.... this is all completely irrelevant to your proposed situation.




The funny thing is... many of the things you say are individually correct. Your engine theory and design books are not wrong. The problem is, as usual, context and relevance. You fail to recognize the context in which your statements are true, and in what contexts your statements are irrelevant.

The individual facts you know are correct in some context. You just don't fully understand the contexts/reasons behind the facts you know. Memorizing/regurgitating facts is not enough. You need to understand the theory/relationships/context behind the facts, and how to properly interpret/apply them.




Again, context and relevance.

We're not discussing whether or not the relationship between boost and power gains is the same throughout the RPM range. We're not discussing whether there's a linear relationship between boost and power gains, or CFM.

The context was whether or not two different superchargers on the SAME engine, at the SAME engine speed, at the SAME boost levels, and SAME intake temperature could possibly flow DIFFERENT amounts of air. Since the engine is the same, and it is the engine itself that determines its VE, the VE becomes irrelevant in the comparison.

The only way to change the amount of air flowing through an engine is to modify the engine to change its efficiency, or boost the pressure of the air going into the engine. We are talking about two of the same STOCK engines, so they will have the same VE as each other.

Show me how how two of the same engine, with the same displacement and VE, at the same speed, with the same manifold pressure/temperature, could possibly consume air at DIFFERENT rates.

Whatever you want to believe. I'm tired of this!!! I'm outta here! Have fun.

[KaiserBill]

"Show me how how two of the same engine, with the same displacement and VE, at the same speed, with the same manifold pressure/temperature, could possibly consume air at DIFFERENT rates."

The problem with this statement is that you assume Volumetric Efficiency is constant-- It is not. If two engines have different turbos pushing air in at different volumes per minute the volumetric efficiency of each engine cannot be the same at any point.

I point this little fact out to you about 4 times.


Now, I'm really out...