WTF is Mule trying to say (poll)

[Danglerb]

I have no idea whatsoever what Mules point is.

[rhjames]

perhaps you should just ask......instead of commenting?

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[Mule]

Here's your answer, there is no way on God's green earth or any other planet, that the second atmosphere makes more hp than the first.

[Danglerb]

The farce of this is that why would anybody go to the time and expense of 1 bar of boost without also optimizing the engine for said boost.

I have a 91 Mustang, rated 220 flywheel, and more like 160 rwhp in stock trim. If I put a Kenne Bell blower on with 7 psi of boost and rwhp goes up to around 260 rwhp, maybe 275 depending on minor changes to the intake. Thats more than 50% at the rear wheels and I am using crank HP to spin the blower. The boost makes the crappy stock heads flow well enough that the HP peak is now a bit higher in rpm.

In real engines, that are not race optimized boost is NOT a linear effect on HP.

[Mule]

OK show me one example where the second atmosphere, or half, quarter or whatever makes more than the first (legitimate example) (on earth). Check with Corky Bell. Remember, the second atmosphere contains no more air than the first did.

[Herr-Kuhn]

Turbos rule the forced induction jungle and that is all that really matters.

[rhjames]

and here we go again......

I look at it this way:

when the engine is sitting still, that's normal every day 14 psi in the cylinder.

when the engine runs (on the "intake" stroke) that's negative pressure in the cylinder--- in other words, vacuum or suction.

when you strap on a blower (or turbo) and said device is operating on a 1:1 ratio, it still is negative pressure (on the intake stroke). this assumes that the blower's internal volume is the same as the volume of the cylinders it is feeding---most volumes are not the same, so there ends up being some addition to the actual volume of the air being fed into the cylinders, even if the blower is underdriven.

when you strap on a blower, and said device is operating on an overdrive ratio (or a turbo starts to spin up to overdriving the intake flow), it then becomes positive pressure, as long as it's over 14 psi.

This is why street cars with blowers rarely are seen to have more than a 10% overdrive, while Top Fuel cars are running around 50% overdrive. Of course, I would be remiss if I didn't include that street cars are running maybe 93 octane gas, while Top Fuel cars are running a 90% nitro methane/10% methanol mix.


I am no engineer, nor do I have a degree in physics, but that's just how I see the way this talk of atmospheric pressures and blowers, turbos, and such pans out......

This talk of one bar here, two bars there, is a little beyond my feeble mind, but if you want to talk pressure, a in pounds per square inch, that's something I can relate to.

Then again, what the hell do I know about boosting an engine?????


(If I get 43 psi on my turbo gauge in my big rig, and the pyrometer doesn't go beyond 1100 degrees on the cold side of the turbo, [that's around 1350 degrees in the combustions chamber...] I'm making nearly 780HP and over 2100 ftlbs of torque pulling over 260,000 gross pounds and doing one hell of a job getting it done......)

Short of all this, I'm probably wrong in my examples, but I do know that 43 psi makes some badass pulling power...

Feel free to pick this one totally apart for the fun of it-


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[Mule]

In an internal combustion engine, as most marriages, suction does not exist. Give that some thought.

Here, I'll go ahead & let the cat out of the bag. All engines are "forced induction." Without a compressor they are "forced" at 14.7 lbs or 1 atmosphere. When the valve opens the air is "forced" in under 14.7 lbs. This is why the second atmosphere can't make more power than the first (with proper tuning for both conditions). There are no mystical packing velocities, efficiency improvements or any other magical phenomenons that can cause this.

Physics is physics.

[Mule]

It's not semantics. If there was not atmospheric pressure, when the valve opened nothing would happen, suck as it might, nothing would happen. You absolutely feel pressure differential when you put your hand over the carb. But without atmosheric pressure it ain't suckin' nothin'. Forced induction is what engines run on.

Check with your local physics professor.

[Danglerb]

This discussion needs beer and a chalk board.

True, air flow is all push, nothing pulls, what you feel over the carb is the weight of the air in the column miles above it pushing down with little opposition.

My argument is that flow through the engine is not a linear function of pressure, or even of mass (pressure at constant temperature), and that power generation isn't a linear function of mass either.

Isn't it possible for boost to shift the peak HP up in rpm?

[Danglerb]

Originally posted by jimmyt123
Yes, but if this is a mere excercise in semantics, then it's a useless discussion. I understand about atmospheric pressure, but without the engine running, you wouldn't feel the push or pull of those psi, something which makes this issue even more useless.

Stupidly, I allowed myself to get sucked into this useless discussion, wasting time at the keyboard. Might as well go to the beach, have a burger and beer. If you want to see what I'm looking at rather than bogging down in mundane discussion, you can do a search for the web cam at Hennesey's in Hermosa Beach.

Actually you were pushed in.

Thinkin hard about Smokin Moe's on Main in HB, for some pig and swig.

I've got no idea if push, pull, blow, or suck has any real bearing beyond language on HP. I do know this is a picky ass argument that has so far avoided any of the picky ass details that do matter.

I hope I didn't waste my stupid question of the month on Speedtalk forum, but I asked there for some input since some of those guys run high pressure differential flow benches, but that turd hasn't finished its polishing yet.

[DanielDudley]

Normal atmosphere is in essence 0 PSI because it is the same everywhere, and yes, you can pump air as well as fluids.

Can an engine make more than double the HP at one bar ? Possibly, if you are flowing more air and fuel than double the NA amount. I believe this would be a lot easier to achieve with an inefficient engine with a restrictive exhaust, as a supercharger doesn't care about the scavenging effect of a good exhaust. It just fills regardless. Also, it can overcome a poor intake setup as well, which is severely limiting to a NA engine.

If you really want to blow your mind, consider a jet airplane motor. The tubine has to be spinning, to harness the explosion of air and fuel into thrust. It also uses this energy to power the turbine that harnesses the explosion. However, you cannot light a jet without first spinning the turbine to create that harnessing pressure, because one atmosphere won't cut it at a net pressure differential of zero.

When a NA engine fires a cylinder, yes it draws air into an ajacent cylinder, and yes atmospheric pressure helps to fill that void. At very high revs, a restriction will cause vaccume. A lack of restriction and a long intake runner will cause flow at velocity, and velocity causes the mass of air molecules to keep moving down the runner and actually pack the runner with a net positive pressure so that air will be forced into the cylinder as the valve opens, with a greater than atmospheric force. Scavenging momentum and draw in the exhaust can help lower the pressure in the cylinder, further enhancing cylinder filling. This is why so many high performance engines have overlap between the opening of the intake valve, and the closing of the exhaust, and why headers are so important in utilizing the pulse timing of the different cylinders to draw the exhaust from each other. As overlap is only really effective at high RPMs where velocity is a factor, Variable cam timing is used to eliminate overlap at low RPMs on some modern engines.

These things are much less important to a blown engine.

Also, consider that an engine can have low or high compression. Low compression does not really add any energy to a combustion explosion. Higher compression adds energy to the explosion in the form of heat and molecular velocity, which is very much the same thing when you quickly compress a gas. Forced induction raises compression, which also raises horsepower, about 4% for every point you raise compression. That is independent of the method by which you raise compression.

Just more stuff to think about.

[rhjames]

I thought I explained this stuff fairly well, but I'll try a different approach......


normally aspirated engines do not run on forced induction, but the vacuum action of the piston headed south on the intake stroke.

Forced induction would be superchargers or turbochargers, spinning their impellers to force the air into the cylinders.

to follow your example of atmospheric speak:

1st atmosphere is 14.7 psi----the same "pressure" that exists while the engine is sitting still (not running).

somewhere between 1st and 2nd there exists an idling engine, but the atmosphere is now negative atmospheres, because of the vacuum generated by the down stroke of the piston.

2nd atmosphere is where the engine is running with twice the pressure (29.4 psi). My Cummins diesel is now making about 525 hp.

you state that 2nd atmosphere does not/will not demonstrate any power improvements. wrong.

you are mistaken in this example, because if I shoved 29.4 psi into my truck (Cummins Signature 600) engine, you better believe it makes more power than at idle, a lot more power.....

similarly, at 3 atmospheres (roughly 44.1 psi) the same diesel engine will be making approximately 785 hp.


semantics aside, these are the performance figures of fact relating to pressure per square inch of turbocharged boost.


turbocharging/supercharging a gas engine is relatively the same as it relates to this discussion.

it's all about pressurizing the cylinder while on the intake stroke. packing more fuel and air into the cylinder than is normally sucked in by the intake stroke of the piston. in other words, artificially creating a higher compression ratio by forcing more air into the cylinders.

in a normally aspirated engine, air is not "forced" into the cylinder, it is sucked (vacuum) in by the downward stroke of the piston. there is no forcing of the air into the cylinder by some force on the back side of said volume of air going into the intake ports......

on the intake stroke, a NA engine always has negative atmosphere (vacuum). turbo/super charged engines have the same negative atmosphere at idle, but when the rpm is increased, the atmosphere (s) are increased due to the "pressurization" of the intake port/stroke (because the impellers are now spinning at a higher rpm allowing the charging device to overcome the negative pressures created by the intake stroke.)

it is rare that super/turbo charged engines do not have negative atmosphere (vacuum) at idle. I can not think of any that would not.....maybe top fuel motors, but that's another subject-----they are running near 50% overdrive on the blower these days.

High compression ratio engines do make more power (until you reach the point of detonation) because you are squeezing the fuel/air mixture into a smaller space before ignition. (as opposed to low compression ratio engines)

the principle is the same for turbo/super charging. you are forcing more fuel and air into the cylinder by these devices.

static (sitting still) compression ratio for my diesel is about 10:1. once you crank it up and the turbo starts feeding the cylinders, this ratio goes to near 22:1.

at atmosphere 1 (sitting still-not running), it makes zero power. at atmosphere 2 (idling, un-boosted) it makes about 100 hp. at atmosphere 3-4, it makes significantly more power....say as much as 800hp on the high end of things.


I suggest you go to your physics teacher and relay these figures to him and get his thoughts.......


If he still tells you we don't know what the hell we're talking about, tell him to take a trip over to his local diesel shop and see for himself.


this has become excessively long and there will be further arguments made by all, but this a common sense way to explain what's actually happening in a charged environment.....Enjoy----


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[Mule]

And your point is??????

[Danglerb]

Originally posted by Mule
And your point is??????

See thread title, I haven't changed my vote.

Everyone in this thread clearly has at least a basic understanding on how a motor works and what makes power.

Mule keeps saying pressure, but I think he understands its actually the mass of air flowing through the engine, not just the input pressure unless other factors like temperature are kept constant.

I don't believe its exact, but I suspect its "close", to say 14.7 psi of boost will make no more than twice the NA HP, but I can think of half a dozen points that should be clarified, like is this RWHP, Flywheel, or whatever the name is for HP without any parasitic losses. RWHP is after driveline losses that are RPM related, not HP, so in an extreme case where the engine is only slightly more powerful than the driveline losses doubling "base" HP will more than double the RWHP.

Thermodynamics of combustion aren't simple and linear either, but I don't know em.

*** now engaging popcorn mode ***

[T_MaX]

I have played with turbo’s a little and found that sometimes there is no ease explanation for some results found when applying more or less boost after doing a modification.
I remember once when I was trying out different Intercoolers, I found that I had to tailor my boost at different RPM’s and pipe diameters to optimize for each one (IC).

Turbo projects are supposed to be fun, lets keep it that way

[Herr-Kuhn]

I think you should all stop by this weekend and help me finish the sewer pipe system for the 32VTT

[Fabio421]

Danglerb, I find it amusing how you are trying to get ebveryone to pile up on Mule. You were the one getting picked on over at Rennlist and were forced out. I'm sure you didn't like it too much. Why would you do the same to someone else?

I think that most people here fully understand the point that Mule is trying to make. I think he may have alterior motives or he may not. Its hard to tell. His basic point is how you can make more than twice the power by keeping EVERYTHING the same except the boost pressure which would double. This means that the fuel ratio would be the same, the dyno, the weather, exhaust, etc. He's bringing up a good point that most would rather ignore because they either have a vested business interest in doing so, or do not understand the subject well enough to answer intelligently. This is not a stab at the turbo builders, the SC guys have been embelishing their results for a few years now. I guess I am off on a tangent so I will stop. My point is this, quit picking on people Danglerb. And while I'm at it, rjhames needs to lay off of Dangler too. This pelican board doesn't have enough people posting to have the luxury of feuds.

[Danglerb]

My intention was to engage not exclude, and get Mule to really lay out what he is trying to say. If it boils down to all you boost guys fudge your numbers, well I'm still glad we aren't talking politics, and we are all in the same religion, Porsche 928's.

Maybe its a fine point, but I wasn't forced off rennlist. I asked JohnD for a refund of my membership fee and was immediately banned. Prior to that I was planning on a new "fresh start" acct using my real name, and RandyV told me that was a "good idea". I think its a bit petty of them, but maybe over time they will lighten up and remove the ban. Its certainly a PITA trying to read the threads without being able to see the images.

Back on topic, most people aren't doing "science" here. Methods and apparatus are rarely revealed, and testing is not precise. Thats just the nature of the beast. I have a 91 Mustang, and there is no public consensus on which headers are best or how much HP they add after 20 years of competition and magazine testing.

OTOH if we didn't have anything to discuss it would take a lot of the fun out of drinking.

[m21sniper]

Originally posted by Danglerb
I have no idea whatsoever what Mules point is.

In a 100% efficient system 1 bar of boost is the equivelant to doubling displacement, so yes...it is the same as doubling HP.

In reality, no street legal system gets much beyond 90% total system efficiency.

The reason a forced induction setup MAY create more HP per % of boost at say 30psi as it might at 20psi is a matter of intended system efficiency at a given RPM range and boost level. However, even in a 100% efficient system, 1 bar of boost will produce EXACTLY twice as much HP as a 100% VE NA motor in motors of identical displacement.

There are many factors at play here.

Also, it is entirely possible to achieve positive boost on a naturally aspirated engine in an intended operating range.

One example would be a "Tunnel Ram" dual quad intake.