Mr. Sir

It may sound like a counter intuitive idea, but so did pressure ratio the first time I heard about it. I've addressed the problem of the turbo being out of its efficiency range. Out of my 3 previous posts, you only addressed the 2nd one, which had almost nothing to say.

So I know with a restrictive pipe, the cross sectional area for air to flow is smaller, but considering the air has jumped from 10psi to 40, a similar amount of air (in compressed form) will be moving into the 6.2 as the 4.8. Point 1 to disprove.

The math in the previous post:
Turbo sees W exhaust backpressure and X psi, therefore it moves Y volume of air.
Engine gets Y volume of air, combustion occurs at T cylinder pressure, and it produces W exhaust backpressure.

Turbo sees (1.5W-.5W) exhaust backpressure and (0.5X)x2 psi, therefore it moves Y volume of air.
Engine gets Y volume of air, combustion occurs at T cylinder pressure, and it produces W exhaust backpressure.

Point 2 to disprove.

If you can explain how having more exhaust NA will generate less boost, maybe it'll make sense how less hp is obtainable (though a wastegate will fix this, so you'll have to shoot down wastegate function as well). Also if you can explain how similar restriction (psi) between the 2 engines will favor the 4.8 (or the base of this statement; how does the 4.8, with similar restriction as the 6.2, get a greater volume of air. Given: tubulence is similar, the restriction is before the intake manifold on the 6.2, and the restriction is in the cylinders of the 4.8); I'd like to know.

Point 3 to disprove.

I previously tried to argue that the 6.2 would have less intake restriction (only 10 psi), and would therefore have greater airflow. To which it was responded that even though more air COULD flow to the 6.2 than the 4.8, the pressure ratio would cause inneficiency. Now, having brought efficiency up, and having similar amounts of air moving through the engine, how could it NOT produce the same power as the 4.8.

Point 4 to disprove, and it's virtually the same as point 1.

To disprove them: tell me how a turbo, operating at a constant 150k rpm, and seeing 40 psi, will NOT move a similar mass of air to the respective engines. (can't use airflow as an excuse now, cause if it moves less air, and is operating at a constant rpm, it will unavoidably see greater psi.)

427

iTrader: (3)

Jim,
Use a gun. If you chew up glass from lightbulbs you will die slow and painful, it will be like reading this thread.....

Kurt

Nexus9

I'm not sure that the "volume" of air produced by the turbocharger is the measure of it's effectiveness. The key to turbocharging and supercharging is to pressurize the intake manifold. Consider:
POWER is the rate at which we can move a certain mass a certain distance.
Power, in an internal combustion engine, is BMEPxRPM (Brake Mean Effective Pressure times Revolutions Per Minute).
If true, then why would horsepower roll OFF after a certain rpm? Increasing RPM should continue to increase power until the engine blows up. The reason is that at higher rpm, the valves are snapping open and closed so fast that air, at atmospheric pressure of about 15 psi, can't get past the valve in such a short period. By pressurizing the manifold, we push much more air/fuel mix past a quickly opening/closing intake valve, such that we increase the BMEP at higher rpm simply because the cylinder is being filled much more effectively. This is why we regulate turbo/supercharger "boost" in psi, not rpm or volume.
Make sense?

Mr. Sir

...this could account for some loss of hp. Not all, pressure ratios still have a lot to do with it, but it's good info. I still stand by similar air volume = similar power, but taking this into account, there is power to be gained by having greater pressure at the valves (since it's a more efficient use of psi).

qqwqeqwrqwqtq

Truer words have never been spoken. Appreciate the good advice

gregrob

iTrader: (8)

Lol!!

qqwqeqwrqwqtq

Mr Sir, I'm not going to dignify your "points" with a detailed response because everything you posted is absolute nonsense.

Everything your imagination has conjured up amounts to something even more ambitious than perpetual motion and is in direct conflict with reality.

Mr. Sir

So... you're done? Anyone else want to pick up where he left off? I always hate it when someone says they're to good to talk to you. You haven't really disproven anything I've said, just constantly said it's nonsense.

So can ANYONE tell me how a turbo, operating at a constant 150k rpm, and seeing 40 psi, will NOT move a similar mass of air to each respective engine (the 4.8 and the 6.2. You can't use lack of airflow as an excuse, because if it moves less air, and is operating at a constant rpm, it will unavoidably see greater psi). And if a similar mass of air is forced into each engine, HOW will the 6.2 make less hp (disregarding that the air in the 4.8 will have greater initial velocity due to psi, since it's unlikely this property accounts for the only difference in power. If this was the case, then pressure ratios would be rendered irrelevant, which really is impossible. Chances are it's a small portion of the lost power).

I see no problems with these trains of thought, and nobody's ever disproven them in the real world, so, if you... if anybody can, go ahead.

topend

Mr. Sir the problem with your point about the turbo operating at 150k rpm making the same power on a 4.8 and 6.2. Is that a turbo is not a positive
displacement pump. A turbo operating at 150k rpm does not guarantee X amount of power.

qqwqeqwrqwqtq

Did you happen to read post #81? It disproves everything you've said.

If you can't understand that restricting/closing the throttle lowers airflow/output/boost/turbo shaft speed, there's not much else to say.

Mr. Sir

But a turbo operating at 150k rpm, and with 40psi of non turbulent restriction, does guarantee a similar mass of air to be moved, which in effect guarantees X amount of power.

Yeah, and I remember this part quite well:
"Logically, you cannot increase airflow/horsepower/efficiency by introducing a restriction."

I tried arguing this earlier. I said the 6.2 had less restriction, and so would produce more power. Everyone else said pressure ratio. So this is the combination of the 2; 40psi at the turbo = similar mass of air for the engine, regardless of what size it is. I've covered airflow (air mass), I've covered horsepower, I've covered efficiency. So what's wrong about anything I've said. In specific. The only thing different between the 2 engines is displacement and intake pipe diameter (to emulate lower displacement).

Here's a good way to disprove this; would a small diameter pipe on a 4.8, one with an absolute pressure value of 40 psi at 150k rpm on the turbo, restrict power? since the pipe is capable of generating 40 psi at 150k rpm, it doesn't matter what it's feeding into, so long as it whatever it is wouldn't restrict flow more than 40 psi, even with a large diameter pipe. So overall system pressure is still 40 psi; 40 at the turbo, 40 at the valves.

What would pressure be in the pipe in a closed enviroment, considering it generates 40 psi in an open one?

also can a turbo, spinning 150k rpm, with 40 psi of restriction, generate different amounts of air mass?

I've tried to disprove my theory, but always arrive at dead ends. So if your enlightened self could break down why it won't work, I'll stop talking.

Sarg

iTrader: (6)

Play with matchbot by Borg Warner. It will show all kinds of different outcomes and you can test your theories in a virtual environment.

Orr89rocz

iTrader: (13)

Locked speed, the compressor wheel will just generate one mass flow given the same inlet gas conditions. So it takes in a quantity of atmospheric air and compresses it to 40 psi discharge at 150K rpm, thats what it will do no matter what. How the engine uses that air is a different story. Not all motors will make same hp with a given amount of air flow. Some of the top motors are getting 2.4-2.5 hp per cfm with a great designed intake tract and valve events. Not so great design may only see 2.0. It varies.

\
Air velocities in the port at pressure dont change compared to atmospheric ports. Only at very low valve lifts theres a chance of higher velocity due to greater charge density on inertia ramming but for the most part, increased charge density doesnt mean more velocity.

qqwqeqwrqwqtq

I've certainly attempted to do so and it's going nowhere.

Again, a turbo engine operates in closed loop, when you close/restrict the throttle you eliminate airflow through the engine which eliminates the energy required to drive the turbine. One effects the other. You are assuming that when you restrict the induction side, the turbocharger will somehow power itself and maintain the same shaft speed when actually it will slow down when you close the throttle.

If what you said was possible, every time you lifted off the throttle the turbo would somehow self propel itself and produce massive amounts of pressure in front of the throttle blade.

I've also already addressed realistic pressure drops and efficiency.

Another example.

An engine with an efficient intercooler/cold side and a 40psi wastegate spring. .5psi drop across the cold side/tb has 39.5psi pressure available at the intake valves for the engine to consume. Assuming ideal turbo sizing for max HP, 40.5psi exhaust backpressure.

Same engine with an inefficient cold side or inlet restriction as you describe. same turbo, same 40psi wastegate spring, 10psi pressure drop across the cold side. Now the turbo is still creating 40psi but 10psi is lost across the cold side so their is 30psi pressure available at the intake valves for the engine to consume and now their is also 50psi exhaust backpressure.

You think that because in both cases the turbo is producing 40psi that they are both flowing the same amount of air through the engine?

Sorry if you think I'm acting "too good' for you but I can only repeat the same thing so many times before I have to accept it's an exercise in futility.

Mr. Sir

Well, I did more reading last night, and it seems my theories were foiled since the added exhaust pressure drained more power than the added psi was worth. Perhaps you should've put more emphasis on the complexities of pressure ratios, since it's what ultimately disproved the theory.
...So I'll stop talking now.

05HD

Are you seriously trying to say that if you drop the intercooler pipes down to say an inch in diameter that a 6.2 liter engine will make the same power as a 4.8 with properly sized pipes?

I will put it up one more time. Turbos make torque, not horsepower. If you strap a little turbo on a big engine, it will spool up real early and make the torque at low RPMs then quickly choke. Since hp= (torque x RPM)/5252 and we all know 3rd grade math, the lower RPM you make the torque, the less power it will make. Pure and simple. We shouldn't have to be eating lightbulbs over this.

427

iTrader: (3)

Like a moth to a light! Me 2, I kept coming back!!!
You are very even tempered.....

Kurt

Mr. Sir

Oh good, a new argument.

hp is a measure of air mass (coupled with efficiency). So if two engines are fed the same amount of air, and use it at a similar level of efficiency, they will generate a similar amount of power, regardless of rpm (having 700 hp worth of air at only 2000 rpm would produce a huge amount of torque. But having 700hp worth of air at 2000 rpm is highly unlikely). The previous argument was about getting a similar air mass into the engine, because if you could without significant parasitic loss, you could generate similar peak numbers with a larger engine, and have quite a bit more under the curve. Unfortunately, the exhaust pressure would increase, turbo rpm would decrease, and your target air mass wouldn't be reached even with 40 psi at the compressor wheel, so I'm no longer trying to prove that theory.

I almost agree with you, and I do agree with your real world examples (kinda hard not to).

Turbos make torque, not horsepower... I suppose that's one way to look at it (an incorrect way, since your 3rd grade math proves that it makes both), but if you put that small turbo on a small engine, it'll make big power if you spin it high enough. So yes, VE goes up with a turbo, and VE is directly related to torque. But torque is directly related to horsepower, so I'll have to disagree with you here.

Oh, and I didn't learn multiplication or division until 5th grade. Schools these days.

05HD

No it isn't. Horsepower is torque x RPM / 5252

pwrtrip75

iTrader: (8)

Didnt think this concept was that hard to grasp. This is simple physics.