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Do PSRU's increase engine HP X or so?

G

Garth

Member
Is a 150 HP rotary at say 6000 rpm actually putting 300 HP to the prop (by gear reduction) if it is reduced by a PSRU by more than a factor of some 2 to 1 (down to say 2600 or less rpm) over say a conventional 2600 rpm lyconie at 150 hp direct output, straight to the prop?

So then a plane with a 300 HP design limit means one must use a 150 HP high RPM engine if it is reduced by PSRU's? (To be based then on their actual gear reduction of course)

What say ye? :rolleyes:
 
no

you cant make power through gear reduction but you can multiply torque. power is the rate at which torque can be produced. IIRC. the given engine wouldnt be able to turn the prop at that speed where it produces the rated power therefore can not develop the power its capable of. you reduce its output through gear reduction to alow it to spin up into its power range where it can produce the power its rated for.
 
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No, doesn't work that way

Garth said:
Is a 150 HP rotary at say 6000 rpm actually putting 300 HP to the prop (by gear reduction) if it is reduced by a PSRU by more than a factor of some 2 to 1 (down to say 2600 or less rpm) over say a conventional 2600 rpm lyconie at 150 hp direct output, straight to the prop?

So then a plane with a 300 HP design limit means one must use a 150 HP high RPM engine if it is reduced by PSRU's? (To be based then on their actual gear reduction of course)

What say ye? :rolleyes:
Click to expand...

No. If you put 150 HP into a PSRU, you get no more than 150 HP out of it. In fact, you'll get slightly less due to the losses in the gearbox due to friction, oil viscosity, etc.

Power is torque x rpm. What a gearbox does is let you trade one for the other, but the product of the two won't change. So if you have a 2:1 gear ratio, it'll cut the speed in half and double the torque.

Hope this helps,
Martin
 
Thanks guys, but it is torque HP that drives the prop I am told not break HP, so if the torque HP of the engine is 150 THP, then a 2:1 PSRU yields 300 THP to the prop? (More or less)
 
Garth said:
Thanks guys, but it is torque HP that drives the prop I am told not break HP, so if the torque HP of the engine is 150 THP, then a 2:1 PSRU yields 300 THP to the prop? (More or less)
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Uh, torque horsepower? I think that is a new term on me.

Horsepower is a measure of power and torque is a measure of twisting force and RPM is a measure of rotational speed. Horsepower is what matters at the prop although a suitable RPM for the prop is important and that can be altered by gearing. Gearing can alter torque but can not increase horsepower, as has been stated.
 
Garth said:
Thanks guys, but it is torque HP that drives the prop I am told not break HP, so if the torque HP of the engine is 150 THP, then a 2:1 PSRU yields 300 THP to the prop? (More or less)
Click to expand...

Garth,

You asked a question, you got the answer! Are you going to disregard it?There is no such thing as a free lunch. HP is HP! 150 HP is a measure of work, whether it is turning a short prop direct drive or a long prop at half speed. If your contention was the case, we could make unlimited horsepower
through lower and lower gear reduction, but that is not the case.

For an easy explaination, look at the Eggenfellner engines. They have 2 to 1 reduction,
but are slower and display less climb rate. Performance is your only true measure of horsepower.
 
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Well I just do not understand then. I am told by very knowledgeable people in the past that it is torque HP that does the work. Break HP and torque HP are sometimes widely different on the same engine (Ford diesel with 320 break HP and 640 Torque HP) Which is why big trucks are so powerful, and of course gear reduction will increase power to the wheels of a car or truck, so why not to an aircraft prop? You say the PSRU (through gear reduction like gearing down for a hill in a big truck) increases the torque output, and if torque drives the prop???? Maybe I just need time to see it. Not used to the PSRU thing. All my planes have had direct drive Lyconies in them.
 
Bottom Line: You have to burn twice the fuel to get twice the horsepower. No free lunch. Repeat after me: "No Free Lunch."
Or: "TANSTAAFL"
 
I'm not sure that I can agree that horsepower is proportional to fuel burn. Wouldn't this only be true if both motors were equally efficient? I had a worn out old volks that use to suck down gas like a dragster, but probably only made about 25 horses.
 
Garth said:
You say the PSRU (through gear reduction like gearing down for a hill in a big truck) increases the torque output, and if torque drives the prop???? Maybe I just need time to see it. Not used to the PSRU thing. All my planes have had direct drive Lyconies in them.
Click to expand...

Garth
First the equation for HP:

HP = (TXN)/5252
T is torque in ftlb
N is RPM

Second, power in equals power out plus any loses.

Now to increase the torque you would decrease the RPM. Sense if you slow the engine down it will make less power, the only way to keep the power but increase the torque is to use a gear reduction. This could be a PSRU in a plane or the transfer case in my 4X4.

Now if you look at an engine like a Lycoming 320, it makes something like 300 ftlbs of torque at 2000 rpm. The engine was designed to make that kind of torque at a low engine speed. Auto engines don't make that kind of torque at 2000 rpm. In fact a similar output auto engine will only put out 150 ftlbs at 4000 rpm. Now this is where the gear reduction comes into play. If you take that car engine that makes 150 ftlbs of torque at 4000 rpm and put a 2 to 1 gear reduction on it, it will make 300 ftlbs or torque at 2000 rpm at the prop.

I hope that makes things clear.

Cam
 
Garth said:
Well I just do not understand then. I am told by very knowledgeable people in the past that it is torque HP that does the work. Break HP and torque HP are sometimes widely different on the same engine (Ford diesel with 320 break HP and 640 Torque HP) Which is why big trucks are so powerful, and of course gear reduction will increase power to the wheels of a car or truck, so why not to an aircraft prop? You say the PSRU (through gear reduction like gearing down for a hill in a big truck) increases the torque output, and if torque drives the prop???? Maybe I just need time to see it. Not used to the PSRU thing. All my planes have had direct drive Lyconies in them.
Click to expand...

You are mixing up the units. No such thing as "Torque HP". Horsepower is torque multiplied by RPM.

On your Ford diesel example, that is 320 brake horsepower (HP is a unit of power, which is the time rate of energy output), and 640 ft-lbs. of torque (a unit of force). It's not unusual for diesels to have a peak torque that is much higher than their rated HP, and yes, that is why they can pull large loads. In other words, with such high torque, they can put out a huge drawbar pull, if you like. But their top speed and acceleration will still be limited by the horsepower.

Flying the plane at "X" speed requires "Y" amount of energy per unit time = Y amount of power. No ifs, ands, or buts about it. No way to increase that with a gear drive.
 
Steve said "It ain't so".

Steve, on power on land based vehicles I know some. A 1940's 35 HP John Deer one lung farm tractor can pull a 4 bottom plow, be it at 3 MPH, by gear power, not engine power. You can take a very small engine and do big jobs through gear reduction in place of brute horsepower. Horse power will do more work faster, again using gears to get there, but can be amplified many times with gear reduction. A old D-8 cat also had just an 80 HP engine, but did huge amounts of work.

Perhaps its just the way you look at it I guess. I researched it now and find that HP is just a mathematical formula. Some variants of it though are performance based, like Dino results (true power output) and are very different from the "Rated" HP, so it is very complex. The issue here seems to be more one of the ability of a prop to preform and use the power generated. Reduction by the PSRU makes twice the torque, but at 1/2 the rpm so the prop can function, which even though the shaft has twice to "power" it is at 1/2 the speed so the gain is lost and the prop has so Little range of RPM and there fore effectiveness or efficiency. On a land vehicle however you would just keep up shifting until you reach the max performance output of the engine to the weight and speed of the vehicle, conversely down shifting to match the power needed to pull the load or climb the hill, thereby increasing the effective and usable "power" tremendously, even though the engine is at a fixed, and much smaller true power output.
 
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We can go back and forth all day on this, but the fact is that power cannot be increased (or decreased) through gearing. We all know that by shifting down, we can get our vehicles to climb steep hills or pull stumps, but this is the result of two things: First, the mechanical advantage of the lower gears increases torque. It's no different than using a long extension on a wrench. It doesn't increase the operators power, only the torque. Second, the engine is able to run at a higher RPM, closer to its peak power output. I'm a cyclist, and I can tell you without any hesitation that my maximum power output is a determined by my body only, and not what gear I am pedaling.
 
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I'll try it this way...

A horsepower is just a unit of power, like watts or ft-lbs/sec.

One HP is equal to 550 ft-lbs/sec. If you're pulling a 550 lb load at 1 ft/sec, it requires 1 HP of power.

if you're pulling a 1 lb load at 550 ft/sec, it also requires 1 HP of power.

A gearbox lets you pick which of those two you're doing...the formal engineering way to express that is that it matches the engine to the load.

But 1 HP is 1 HP. There's no such thing as "Torque HP."
 
Let me try to simplify.

This isn't anything new from what has been said above, but with skipping all the unit of conversion and math, this is what I understand.

If you have two engines A) makes 150 hp at 4000 rpm. B) makes 150 hp at 2000 rpm.

Ignoring the loss of due to gear reduction, if A drives a prop through a 2:1 gear, then both engines will pull your plane through the air the at the same speed.

Kent
 
Let's Dyno

The real problem here stems from the fact that none of the alternative builders will dyno their engines. We can hardly blame poor Garth for this misconception, because the alternative guys stay in business in part by perpetuating this gearing myth.

Twenty years ago, my Dad and I had this very same discussion regarding his beloved Pinto engine. He told me it would be the ideal aiplane engine if geared 2 to 1, as it would yield twice the horsepower! Nothing I could say would disabuse him of this fallacy, and he is both a mechanic and flight instructor! There is something very compelling about the perpetual motion myth, and this issue is definately an off-shoot of that arguement.

I would like to take this golden opportunity to restate my earlier offer to
fund a dyno run of any Eggenfellner engine. You provide the engine, and I will pay the dyno fee to find out what kind of brake horsepower these engines really produce.
 
Aha! Eggenfellner is to blame for the age-old confusion about hp and torque! What an evil genius he must be. I heard he also caused the split between K-Fed and Britney. Scoundrel! :cool:
 
Reason for GBs

HP is a function of rpm. The reason for gear boxes is to match the operating rpm to the HP curve of the engine.
 
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Let's DYNO!

DGlaeser said:
HP is a function of rpm. The reason for gear boxes is to allow the engine to match the operating rpm to the HP curve of the engine.
Click to expand...

Yes Dennis, in theory, that is correct. However, it doesn't explain the 20 mph speed hit the 4 cyl Sube installations are taking in the RV-9, or the 10-15mph deficit in the 6 cyls. Yes, cooling drag and reduction losses are present, but why won't the builders dyno???? Can we dyno yours??
 
We need to dyno both the Sube and the Lyco on the same dyno then install them in identical airframes and do a side by side. Then we have a valid experiment. You can no more assume a certain Lycoming with X exhaust, pistons and carb puts out the rated hp than pulling a number out of the hat for the Sube. The Lycoming may in fact put out more than factory rated hp in many experimental configurations.

Kent summed this topic up best with his post.
 
Garth,

Your "very knowledgeble" person was right. Torque is what matters, however torque is a measure of force * distance (ft*lb, N*m, whatever suits your fancy). Horsepower is not force * distance so therefore there is no such thing as torque horsepower. Your tractor example is nice, sure you could gear down an engine and have tons of torque, but the more you gear the slower it goes. Yes a "small" horsepower tractor can be geared for tons of pulling power but how fast does it go? There is nothing free. You could gear the prop down to 250rpm and have gobs of torque but that will not help you get very far.

Horsepower is a measure of work over time (force moved a distance over time). The equation Cam gave you, Horsepower = Torque * rpm / 5252 is fact. The torque gets doubled (we will assume no friction) and the speed cuts in half and you have the same amount of horsepower. In fact a dyno is measuring the torque, while knowing the rpm and calculating the horsepower. The dyno is not measuring the horsepower, you cannot directly do that, it too is calculating it.

Since there are frictional losses in the PSRU (anything mechanical has some amount of friction) then your question really should read, "How much do PSRU's decrease engine HP?" Sorry those are just the laws of physics at work.

Scott
 
rv6ejguy said:
We need to dyno both the Sube and the Lyco on the same dyno then install them in identical airframes and do a side by side. Then we have a valid experiment. You can no more assume a certain Lycoming with X exhaust, pistons and carb puts out the rated hp than pulling a number out of the hat for the Sube. The Lycoming may in fact put out more than factory rated hp in many experimental configurations.

Kent summed this topic up best with his post.
Click to expand...

No we don't! Lycoming dynos all their products. I'm sure we can get certified copies of their results. Let's be the first to dyno a Sube, Ross! You're just the right man for the job!
 
Dyno

Yukon said:
Yes Dennis, in theory, that is correct. However, it doesn't explain the 20 mph speed hit the 4 cyl Sube installations are taking in the RV-9, or the 10-15mph deficit in the 6 cyls. Yes, cooling drag and reduction losses are present, but why won't the builders dyno???? Can we dyno yours??
Click to expand...
You're crossing threads here. The question that started this had to do with the relation between gearing and HP. Now whether the output HP is what is desired is another question.
Dyno testing is involved and expensive, that's why it isn't done. If you know of a way it can be done without removing the engine from the airframe, let me know. Have you dyno'd your engine?
 
I gotta say this has been very interesting and a learning experience for sure. A lot to it and difficult to pull on but I get the power vs speed is the key. Anyway I will follow with great interest. I still think one ought to be able to tap the greater available torque power off the PSRU spindle by adding more pitch to the CS, as more power is at hand on the reduction unit to drive it?
 
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Not true. The geared down car engine is doing that just to try and equal what the ly-clone is capable of already without the regear. You need to stop looking at the redrive as a source for benefit. It is merely an unfortunate necessity to get an engine to operate the prop in the proper range for a prop to be efficient and at a point that the engine can make suitable power. You only get losses (friction and weight) in the redrive not gains.

Airplane engines are so good at what they do simply because they are huge displacement per cylinder and create gobs of power at propellor friendly low rpm and at a relative light weight. In order to get workable car engine solutions you are going to very small displacement motors (because of weight) and therefore they have to have lots of rpm to make any power and therefore need redrive. If only a duramax diesel weighed 200 pounds fully dressed and was smaller, then you may have a real nice auto conversion candidate.

Scott
 
This is true, but it won't help you.

Garth said:
I gotta say this has been very interesting and a learning experience for sure. A lot to it and difficult to pull on but I get the power vs speed is the key. Anyway I will follow with great interest. I still think one ought to be able to tap the greater available torque power off the PSRU spindle by adding more pitch to the CS, as more power is at hand on the reduction unit to drive it?
Click to expand...

The greater torque comes at a slower speed. You end up more slowly taking bigger bites of air with your prop. If you ignore efficiency effects, you will end up pushing that same amount of air behind you.

Another way to look at it. If your plane would normally be powered by a 300 hp lycoming running at 2700 rpm, you can't put a 150 hp lycoming in an add a 2:1 gear. You will end up with the same torque at the prop, but it will only be turning 1350 rpm. Only half that amount of air will be moving passed the prop now.

Kent
 
Well I believe that. The new Subaru ‘boxer’ turbo diesel or the new E320 BLUETEC of Mercedes and several others, plus more even better on the near horizon. Light weight, very powerful and don't need PSRU's (Just a big pocket book)
 
Missed that one somehow. Its a 6000 rpm 300 HP rotary reduced to 2700 rpm, same as the lyc, but now you can add more bite than the fixed rpm 300 HP Lyc can take?
 
kentb said:
The greater torque comes at a slower speed. You end up more slowly taking bigger bites of air with your prop. If you ignore efficiency effects, you will end up pushing that same amount of air behind you.

Another way to look at it. If your plane would normally be powered by a 300 hp lycoming running at 2700 rpm, you can't put a 150 hp lycoming in an add a 2:1 gear. You will end up with the same torque at the prop, but it will only be turning 1350 rpm. Only half that amount of air will be moving passed the prop now.

Kent
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No Kent, you would have DOUBLE the TORQUE, but HALF the RPM, hence the same horsepower.
 
Exactly, I just talked to my old A&P from Alaska and he thinks I am right. A 300 HP 6000 RPM engine, reduced over 2:1 to standard prop RPM's, would have a lot more torque from this gear reduction, so getting a prop to take advantage of it (3, 4 or 5 blade CS designed for the greater torque), and with pitch adjustments also (on a constant speed, or pitch change on a fixed prop either way) one should be able to tap the greater torque now available off of the shaft from the PSRU unit. I will comm MT on this. And as the torque is the same more or less to start with on the rotery or the Lyconies, this should bring a big improvenment to the proformance of an aircraft using a PSRU on a same HP motor.
 
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Yukon said:
No we don't! Lycoming dynos all their products. I'm sure we can get certified copies of their results. Let's be the first to dyno a Sube, Ross! You're just the right man for the job!
Click to expand...

Kinda like saying Subaru already dynos all their engines too. That is not the point of the exercise.

If you want science, use the scientific method. TAC did some dyno tests on some popular Lycomings with various exhaust systems including OE type mufflers and tuned aftermarket systems a few years back. Results- OE was generally way below rated hp, tuned stuff, slightly above. Something like 20hp difference.

If we assume anything we don't know as fact, the results are invalid. We always compare on the same dyno as these can vary considerably.

The results of the full test would certainly be interesting.:)
 
Garth said:
Exactly, I just talked to my old A&P from Alaska and he thinks I am right. A 300 HP 6000 RPM engine, reduced over 2:1 to standard prop RPM's, would have a lot more torque from this gear reduction, so getting a prop to take advantage of it (3, 4 or 5 blade CS designed for the greater torque), and with pitch adjustments also (on a constant speed, or pitch change on a fixed prop either way) one should be able to tap the greater torque now available off of the shaft from the PSRU unit. I will comm MT on this. And as the torque is the same more or less to start with on the rotery or the Lyconies, this should bring a big improvenment to the proformance of an aircraft using a PSRU on a same HP motor.
Click to expand...

A 300 HP, 6000 RPM engine, with a 2:1 reduction drive, puts the same torque into the prop as a 300 HP, 3000 RPM engine with direct drive.
 
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Garth said:
Exactly, I just talked to my old A&P from Alaska and he thinks I am right. A 300 HP 6000 RPM engine, reduced over 2:1 to standard prop RPM's, would have a lot more torque from this gear reduction, so getting a prop to take advantage of it (3, 4 or 5 blade CS designed for the greater torque), and with pitch adjustments also (on a constant speed, or pitch change on a fixed prop either way) one should be able to tap the greater torque now available off of the shaft from the PSRU unit. I will comm MT on this. And as the torque is the same more or less to start with on the rotery or the Lyconies, this should bring a big improvenment to the proformance of an aircraft using a PSRU on a same HP motor.
Click to expand...

Think about it....

Just going as far back as WWII; don't you think this great discovery you're referring too, would be caught by someone in the last 68 years?


Just think of two trucks climbing a hill with different horsepower engines, that match the examples in this thread.. The one that is geared down to make up for those teenie weenie pistons moving at a higher rpm, won't be climbing the hill any faster!

L.Adamson
 
oops, of course your right.

Yukon said:
No Kent, you would have DOUBLE the TORQUE, but HALF the RPM, hence the same horsepower.
Click to expand...

The more I try to simplify, the more likely I am to make a mistake.

OK Garth, your example:

300 hp at 6000 RPM. (prop won't like turning this fast).

2:1 reduction

300 hp at 3000 RPM (prop likes it better, you have downshifted to a lower gear and the prop can bite the air better).

2.2:1 reduction

300 hp at 2727 RPM (prop likes this even better, you have downshifted again, the slower prop can bite bigger chunks of air).

The more air you move passed you the better.

You have the same hp from the engine, the same fuel consumption.
The things to think about here are props don't run well at 6000 rpm.
The reduction gear will consume some of you power (HP).
The prop needs to be designed to be optimal at some RPM, even with a CS prop there are limits to the range of speed.

I hope I didn't screw something up again.

Kent
 
Garth said:
Exactly, I just talked to my old A&P from Alaska and he thinks I am right. A 300 HP 6000 RPM engine, reduced over 2:1 to standard prop RPM's, would have a lot more torque from this gear reduction, so getting a prop to take advantage of it (3, 4 or 5 blade CS designed for the greater torque), and with pitch adjustments also (on a constant speed, or pitch change on a fixed prop either way) one should be able to tap the greater torque now available off of the shaft from the PSRU unit. I will comm MT on this. And as the torque is the same more or less to start with on the rotery or the Lyconies, this should bring a big improvenment to the proformance of an aircraft using a PSRU on a same HP motor.
Click to expand...


OK Garth, I'm an A&P, and I used to live in Alaska, and you are still WRONG. But why don't you spend the next three years building an alternative power airplane only to find it's 20 mph slower than a direct drive version! Go for it!
 
Zero fuel burn!!

Garth said:
by gear power, not engine power. You can take a very small engine and do big jobs through gear reduction in place of brute horsepower.
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Cool! I'm shelving work on the one gallon per hour carb and starting development of the PSRU powered airplane. Just think, quiet, no emissions, and zero fuel burn. ;)

Smart alec mode off.

John Clark
RV8 N18U "Sunshine"
KSBA
 
rv6ejguy said:
Kinda like saying Subaru already dynos all their engines too. That is not the point of the exercise.

If you want science, use the scientific method. TAC did some dyno tests on some popular Lycomings with various exhaust systems including OE type mufflers and tuned aftermarket systems a few years back. Results- OE was generally way below rated hp, tuned stuff, slightly above. Something like 20hp difference.

If we assume anything we don't know as fact, the results are invalid. We always compare on the same dyno as these can vary considerably.

The results of the full test would certainly be interesting.:)
Click to expand...

Really weak point Ross, as we can be sure Subaru has dynoed, but we KNOW Egg has enthusiastically refused to do so. The PSRU is what is at issue here,
and nobody wants to dyno it. What does that tell you?

I'm ready and willing to cut a check for the dyno costs. Anyone? Anyone?
 
The conventional air-cooled aircraft (Lycoming) is simply the easiest, most reliable and still the most cost-efficient way to turn a prop on a small plane. Using a smaller, higher revving engine with gearing is another way, but getting more complex. Carry this to its conclusion, and think of a very small engine running at 35,000 rpm with gearing to turn the prop at 1600 rpm. Garrett turbo-prop.
 
Garth said:
unreal, your glasses are to thick blinding you guys.
Click to expand...
Ok, Garth, you've convinced me with your flawless logic. Those other idiots just don't understand simple physics.

When you install your 300 HP engine, that you made by gearing a 20 HP engine, on an airplane, just make sure not to turn downwind. That can obviously make you stall!
 
Garth said:
unreal, your glasses are to thick blinding you guys.
Click to expand...

Garth, a couple of things.

1. If you havent already done so, I suggest you read Doug's rules about posting. http://www.vansairforce.net/rules.htm

2. As much as you dont want to accept the advice given you, the PSRU will not give you any more HP. It will consume a small bit of HP, in the form of friction, and will deliver more torque, at a lower RPM to the output shaft, than a direct drive off the crank. This is Physics. Cold hard math.

TANSTAAFL.
 
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Mike S said:
2. As much as you dont want to accept the advice given you, the PSRU will not give you any more HP. It will consume a small bit of HP, in the form of friction, and will deliver more torque, at a lower RPM to the output shaft. This is Physics. Cold hard math.
Click to expand...

Just like electricity. Up the voltage & lower the amps. Or visa/versa, up the amps & lower the voltage. And then the transformers and power lines suffer a bit of loss in the form of heat.

But at the end of the day, you get no more energy than what you started with, and actually perhaps a bit less.
 
Garth said:
unreal, your glasses are to thick blinding you guys.
Click to expand...

20/20 vision here thanks.

I give up. I guess i'll throw away my Engineering degree and my Physics books and start listening to some A&P from Alaska that thinks you gain performance when adding friction.

I'll say it one more time, YOU WILL LOSE HP with a PSRU. Period. End of story. How much? That all depends on how much FRICTION it has. Opps sorry there I go believing that book again. :rolleyes:

Scott
 
Wow, what a train wreck!

Speaking to the original thread starting question, I think a Charles Babbage quote is appropriate:
"I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."

Speaking to some of Yukon's trolls, how about a Wolfgang Pauli quote:
"That's not even wrong."

To those who posted useful information, aren't you ashamed of yourselves for ruining what could have been a 100% perfectly surreal thread? :D
 
Yukon said:
Really weak point Ross, as we can be sure Subaru has dynoed, but we KNOW Egg has enthusiastically refused to do so. The PSRU is what is at issue here,
and nobody wants to dyno it. What does that tell you?

I'm ready and willing to cut a check for the dyno costs. Anyone? Anyone?
Click to expand...

It tells me that most people don't care what hp it makes, they care how it performs in the air. Jan has posted some flight data recently on the turbo RV10. It would seem to perform like it has about 190-200 hp which it can maintain to 18K or so. Slower than the 540 below 10K, faster above that.

The older EJ25s operated at 4900 rpm would seem to be making about 149 hp and about 129 at 4200 rpm (cruise) from the factory dyno curves. No way these will perform like an O-360 or even an O-320 for that matter- just as flight tests have confirmed. No mystery there and there will probably be a 4-5% loss through the Egg drive on top of this.

The 3.6L will be the new engine of choice soon. Quite a bit more torque in the most used rpm band 3750-5000 rpm compared to the 3L. 186hp at 4000 rpm now and a lower power peak rpm of 6000 (256 hp) before it reaches the redrive of course. Yes, you will lose power through a redrive.
 
why ?

not t jump threads here, but who cares at this point.....why would anyone want a timing belt on an airplane? esp turning at max rpm. im sure all of this has been said before but car engines are not built to stand up to max rpm for the duty cycles we demand from them. if so nascar engine builders would have a much easier job. and they use 10 times better parts than factory.
yet they scatter all the time. turning a factory built eng to those rpms really concerns me. especially watching the students in my class get new cars like the WRX, EVO's and SRT4s only to have them huffing smoke at low miles...i say they are dogging them but in reallity they are just driving them like we fly them. WFO :eek:if you want to run a car engine wouldnt you build it so you could develop the power at the crank that your application requires with out G/R to each his own i suspect. get a lyc and be done with it. oh yeah i would suspect at the rpms stated the psru eats around 20-40 hp.which depends on the lube used in it.
 
Ted Johns said:
To those who posted useful information, aren't you ashamed of yourselves for ruining what could have been a 100% perfectly surreal thread? :D
Click to expand...

Not at all. I will save a fortune when the time comes to buy the engine for my RV-7.

You see, my lawn tractor has a 14.5 HP Briggs & Stratton engine. When I couple that with a 10:1 PSRU, I will have a very low-cost 145 HP engine.

I recognize that this will be a somewhat underpowered RV-7, so I will install a set of bicycle pedals in the right seat. I will put my 8 year-old daughter in the seat -- she can generate an easy 0.1 HP. With a 100:1 gear ratio connected to her pedals , she should add another 10 HP or so.

Oh, I have to first put my daughter on a dyno. Can I run her lean of peak? You know, reduce the number of Cheerios/hour until her temperature peaks, and reduce it by a few more Cheerios?

I recognize, too, that some will object to installing a child, who is meant to power a bicycle, in an airplane. These critics, clearly opposed to the experimental nature of homebuilt airplanes, will insist that on a bicycle, my daughter only occasionally bursts to high power, whereas in an airplane she will be expected to generate high power for hours on end. What do they know?

If I had more children, I might not even need the Briggs & Stratton.
 
Deja vu.....eh

LOL,
This thread just confirms my thoughts and makes me think of my buddy's 4 cyl Egg RV 7........4800 RPM/7 GPH...34" M.P. and tadaaaah...162 MPH.:eek: But, it sounds like an Indy car coming by my hangar.

Lycosaurus yes...
 
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