Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Midnight on October 28, 2002, 09:10:09 PM
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After reading all the posts about engine toggle and gliding, I decided to do some testing of my own. The results show that there is no turn advantage gained by toggling engine on and off, or leaving it off. Gliding time is not effected by engine on or off, only by engine RPM.
http://webpages.charter.net/davidlj/zips/flighttest.zip
There are two films attached in the zip. All testing done in P-51D, 50% fuel load at test start.
1. glidetest.ahf
2. turntest.ahf
Glide Test Results - Test parameters
Start at 6000 feet ASL, 250 MPH TAS
Engage Auto-pilot level
End at 2000 feet ASL
1. 3000 RPM, NO ENGINE: Glide time 1:54.34
2. Min RPM, NO ENGINE: Glide time 4:03.17
3. 3000 RPM, IDLE Glide time 1.54.16
4. Min RPM, IDLE Glide time 4:10.25
(I attribute the extra glide time on the last test to slightly less fuel weight in the tanks)
Basically, it seems that regardless of engine running or not, the glide time is only effected by the RPMs.
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Turn Test Results - Test parameters
Start at 250 TAS
Bank Right 90 degrees
Execute best turn 360 degrees
Level the wings
1. 3000 RPM, WEP: Turn time 22 seconds, exit turn at 200 MPH
2. 3000 RPM, NO ENGINE: Turn time 21 seconds, exit turn at 200 MPH
3. 3000 RPM, TOGGLE ENGINE: Turn time 21 seconds, exit turn at 200 MPH
4. 3000 RPM WEP: Turn time 18.5 seconds, exit turn at 200 MPH
(The last turn test was started approximately 3000 feet ASL, as compared to the first test which started at 6000 feet ASL. The difference in altitude may have contributed to the performance difference)
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HiTech I also found a bug while doing this test:
Bug report: With throttle postion set to full, toggle on WEP. Shut down engine. Even with engine shut down, the temperature will rise to elevated WEP temperatures once the engine is actually restarted.
Test parameter to duplicate:
1. Plane on runway
2. Start Engine, runat idle
3. Let temp rise to normal (75C)
4. Throttle to Full and Engage WEP
5. Shut down Engine (leave Throttle at maximum position)
6. Wait 5 minutes
(During the wait, you will see the engine temperature rising even though the engine is turned off.
Once the engine is restarted, it goes to 120C like it would if the engine had actually been running at WEP rather than being turned off.
http://webpages.charter.net/davidlj/zips/enginewep.zip
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what do they call that where you take a suger pill but you get better any way through the power of your mind? A supository?
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Originally posted by Pongo
what do they call that where you take a suger pill but you get better any way through the power of your mind? A supository?
It's called a Placebo.
As to the rise in temperature after shutdown: It seems that HTC modeled normal heat-soaking. All water cooled engines get hotter after shut down, because the coolant sits in the hot block and heads without being circulated. It should cool down quickly though after restart. If not, then it's a bug. Try it with an air- cooled engine and see if does it too. It should not, as high-speed airflow over a radial engine after shutdown brings cylinderhead temps down rapidly.
My regards,
Widewing
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What possible use could this have in a sim?? It's probably just a glitch. For example, the Ju-88 has no WEP, but if you hit the WEP button your engines will begin to overheat.
ra
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a water cooled engine that has been shut down hot will continue to rise in temp because the water is not circulated. When the engine is started it should cool rapidly as the water pump circulates the cooler radiator water thru the block.
lazs
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It's a bug.
It has nothing to do with heat soaking
If you shut the engine down and WEP is not on, it cools off, it doesn't keep heating up.
If you shut the engine down and WEP is on (throttle left at 100% and WEP toggled on) then the engine temperature increases.
It's a minor bug, but not the main topic of this post.
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Originally posted by ra
<<>>
What possible use could this have in a sim?? It's probably just a glitch. For example, the Ju-88 has no WEP, but if you hit the WEP button your engines will begin to overheat.
ra
Because IT IS a sim.
Ju 88 engines always run hot during climbout. No one in the real world climbs out at full military power. There simply is not enough airflow to keep the engines within operating temperature limits. For this reason, when climbing, cowl flaps and cooler doors are always open.
That WEP bug may be genuine, but it's no big issue. If HTC modeled everything, a lot of guys would be killing engines by exceeding temp limits on climbout. As it is, they have elected to minimize the complexity of engine operation, not having cowl flaps, oil cooler or radiator doors to set and adjust.
Some aircraft, such as the P-51 and later models of the P-38 had automated systems that controlled cooler (and intercoolers) and radiator doors. Most did not. Ever see a takeoff checklist for a vintage warbird? It's nothing like HTC where you simply start the engine and firewall the throttle. Little details like getting temps up into operating limits, mag checks, prop governor checks and the like are not included here. Personally, I would like to see them modeled, as it would provide a great deal of "real feel". Yet, the effect on game play would be substantial and many would find it a giant pain in the neck.
Here's an example of what is involved in getting a P-40B off of the ground:
2. Ensure that the total weight and distribution of the load are in accordance with the weight sheet summary and ascertain that the aeroplane is in all other respects fit for flight.
PRELIMINARIES
3. Before starting the engine, check the following:
(i) That the ignition switches are OFF;
(ii) That undercarriage, tail wheel, and flap selectors are in NEUTRAL;
(iii) That constant speed toggle switch on control panel is ON; i.e., in "Automatic Control".
(iv) That wheel brakes are ON
(v) Switch on main battery switch and check undercarriage, tail wheel and flap indicator
(vi) Turn on fuel and check fuel tanks for contents
(vii) Check controls for free movement.
STARTING ENGINE AND WARMING UP
Note: For main engine details see Handbooks and paragraph 27 of these Notes.
4. (i) If engine has been standing, turn over by hand.
(ii) Turn carburetor air to "COLD", radiator shutters to "SHUT".
(iii) C.P. control to 2800 r.p.m.
(iv) Throttle to give approximately 800 r.p.m.
(v) Mixture control to idle cut-off. (See note)
(vi) Wobble pump to 4 lbs. pressure.
(vii) Prime engine with two to four strokes
(viii) Mixture control to FULL RICH
(ix) Switch ON
(x) Push heel on starter pedal to energize starter.
(xi) When starter has reached sufficient speed, push down toe of starter pedal to engage.
Note:- Do not increase fuel pressure above 4 lbs. with the mixture control out of the idle cut-out position. If necessary, prime the engine to keep it from stalling, as pumping the throttle does not prime the engine.
TESTING ENGINE AND INSTALLATION
5. (i) Warm up at 800 to 1000 r.p.m.
(ii) Minimum oil temperature before running up over 40°C. - Maximum 85°C.
(iii) Oil pressure - 60 to 80 lbs.
(iv) Radiator temperature for running up - 80°C.
(v) Whilst warming up the engine, check the operation of the flaps.
(vi) Set propeller switch to "manual selective".
(vii) Check the functioning of the engine and magnetos at 2200 r.p.m. and 26 in. Hg. (65 Cm.Hg.)
Note:- Care must be taken to see that the tail does not lift when 1800 r.p.m. is exceeded, and it is advisable to have somebody holding this down whilst running up.
(viii) Reset propeller switch to "automatic" position and check C.P. controls.
TAXIING
6. Owing to the steerable tail wheel, brakes are not necessary in normal circumstances. The view ahead is average and the machine is readily controllable.
If the engine is kept ticking over for any period of time, it should be cleared by being run up against the brakes prior to take-off.
ACTIONS PRIOR TO TAKE-OFF
7. Prior to actual take-off, check the following points by means of some suitable reminder, such as "T" - "M" - "P" "FLAPS" - "RADIATOR"
(i) "T" - trimming tab controls for rudder and elevator should both be in neutral as shown by the marks on the indicators.
(ii) "M" - mixture control should be at full rich.
Note:- It should be at auto-rich if aeroplane is above 3500 feet.
(iii) "P" - constant speed control should be set to give 3000 revs, and check that toggle switch is in the UP (automatic) position.
(iv) "FLAPS" - may be used up to 20° for take-off if required, although the advantage of so doing is very small. See paragraph 1 (iii).
(v) "RADIATOR" - position for this will be dependent on the outside air temperature.
TAKE-OFF
8. The aircraft is very easy to take-off and shows scarcely any inclination to swing, although a little right rudder may be needed. As the Allison engine has a particularly quick pick-up, the opening of the throttle must be done slowly and care must be taken to ensure that the specified maximum manifold pressure of 41 in. Hg (104 Cm.Hg. on French instruments) is not exceeded. See para. 27 for full engine take-off limitations.
ACTIONS AFTER TAKE-OFF
9. (i) Once clear of the ground, raise the undercarriage and tail wheel by pressing the release knob on the end of the undercarriage selector lever, bringing the lever up to the undercarriage "UP" position, and pressing the thumb operating switch on the top of the control column. [DF: Erik says that on the AVG Tomahawks the button on top of the stick was replaced by a toggle below the pistol grip.] This operation is rather slow and whilst the undercarriage is going up -
(ii) reduce the boost pressure to 35 in. Hg. and reduce revs to 2600, and
(iii) maintain a flying speed of approximately 140 m.p.h.
(iv) When the indicator shows that the undercarriage and tail wheel are finally up, check that they are locked into position by operating the emergency hand pump, and if it is solid then the undercarriage and tail wheel are full retracted. Return undercarriage selector lever to neutral position, and
(v) If lowered, raise the flaps by selecting the "Up" position on the flap selector lever, and press the thumb operating switch on the control column. When the flaps are up return the lever to neutral.
(vi) Set mixture control to automatic rich.
Not simple at all is it?
My regards,
Widewing
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way to much time on your hands dude woa:D
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Midnight,
Thanks for doing the obvious testing. :cool:
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Originally posted by krazyhorse
way to much time on your hands dude woa:D
Cut and paste, takes only a minute.
My regards,
Widewing
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Originally posted by lazs2
a water cooled engine that has been shut down hot will continue to rise in temp because the water is not circulated. When the engine is started it should cool rapidly as the water pump circulates the cooler radiator water thru the block.
lazs
Unless you have a couple hundred mph of air blowing through the radiator.
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And then you have what? A cool radiator? :rolleyes:
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Originally posted by Creamo
And then you have what? A cool radiator? :rolleyes:
Exactly, without the waterpump turning, no coolant is circulated.
I used to have a Renault R5 years ago. The fan switch sending unit was installed in the head and was wired directly to power. So, whenever you shut off the engine, within two minutes the fan would begin running. This produced a cool radiator, but that engine was still heat-soaking.
My regards,
Widewing
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1. 3000 RPM, WEP: Turn time 22 seconds, exit turn at 200 MPH
2. 3000 RPM, NO ENGINE: Turn time 21 seconds, exit turn at 200 MPH
3. 3000 RPM, TOGGLE ENGINE: Turn time 21 seconds, exit turn at 200 MPH
4. 3000 RPM WEP: Turn time 18.5 seconds, exit turn at 200 MPH
How can a turned off engine sustain 3000 rpm by windmilling alone?? :eek:
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Originally posted by Creamo
And then you have what? A cool radiator? :rolleyes:
Thermosyphoning will reduce heat soak effects. (http://www.geocities.com/MotorCity/Downs/3837/thermosy.html)
Add in a couple hundred mph breeze and I bet you could keep the motor nice and cool.
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As long as you believe it I guess.
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Originally posted by Midnight
1. 3000 RPM, NO ENGINE: Glide time 1:54.34
2. Min RPM, NO ENGINE: Glide time 4:03.17
3. 3000 RPM, IDLE Glide time 1.54.16
4. Min RPM, IDLE Glide time 4:10.25
Is this thing on,.. testing, testing
Ehem.
I TOLD YOU SO !
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Originally posted by Creamo
As long as you believe it I guess.
No need to believe in it - the turbo cooler in my car works on this principle, so I get to experience it every day.
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My car does not run hot, yet no coolant flows through a radiator, no water pump ever turns and no coolant sits in the block or heads when it has been shut off. It also does not get hotter after shut down, instead it actually cools off very quickly. Oh yea.... there are many aircraft engines that operate exactly like it!
Fang
JG26
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Midnight for doing real research.
good job, interesting find.
eskimo
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Originally posted by funkedup
No need to believe in it - the turbo cooler in my car works on this principle, so I get to experience it every day.
This is an air to air intercooler, not an air to fluid radiator. Any heat transfer via the coolant would likely not keep pace with normal heat radiation cooling thru the total area of the engine block and heads. Irrespective, the engine temp will rise on shutdown as any simple temperature gauge will indicate.
Most high end racing vehicles use a separate, quick disconnect type cooling system to force coolant through the block and heads to prevent any warpage and seal deterioration associated with heat soaking. As soon as the engine is shut down, the external system is connected.
My regards,
Widewing
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Originally posted by Widewing
This is an air to air intercooler, not an air to fluid radiator.
No it's not. There is a coolant loop for the turbo itself, plus an air to air intercooler. The coolant loop is designed so that it will thermosyphon after the car is shut down. I'll try to find an online diagram for you, it's a pretty cool system.
And I never suggested a parked car would not undergo some heat soak. But thermosyphoning can reduce it significantly if you have some forced cooling or a 200 mph breeze.
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Pretty much accepted terms are intracooled and aftercooled. Most Medium and Heavy duty trucks use both. With the purpose of cooling the air out of the turbocharger ie: denser air before entering the cylinders. One using engine coolant, the other a radiator mounted side by side or in front of the coolant radiator.
Nothing to do with engine cooling.
So to in conclusion.
It makes hot air not.....
Have a couple plugged into this board :D
Wide have you seen the Roaring Glory tape on the P40 ?? The difference in start sequences with that and the rest of the Warbirds really shows how "dated" it was even then. Good tape. Actually I like all the Roaring Glory tapes. The ones with Jeff Ethell are really the best.
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Originally posted by poopster
Pretty much accepted terms are intracooled and aftercooled. Most Medium and Heavy duty trucks use both. With the purpose of cooling the air out of the turbocharger ie: denser air before entering the cylinders. One using engine coolant, the other a radiator mounted side by side or in front of the coolant radiator.
Nothing to do with engine cooling.
Poop, not on my car. There is coolant supply and return to the turbo body, for the purpose of cooling the bearings and oil in the turbo.
The only charge cooling on my car is an air-to-air heat exchanger between the compressor outlet and the throttle body.
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Exactly, without the waterpump turning, no coolant is circulated.
@BEGIN(sarcasm)
And this is why all of the US nuclear submarines suffer meltdowns when running their reactors at low power with the coolant pumps turned off.
Oh, wait -- that's standard practice for low-speed silent running. I guess that pressure differential between the hot and cold side of the reactor and condenser are enough to keep the circulation going.
@END(sarcasm)
Seriously, though, a liquid cooling system will get some cooling effect from both the pressure-generated circulation and from heat transmission through the working fluid. However, for most automobile and aircraft engines, the fundamental limits of design (ships don't normally have weight or size as a major consideration), the amount of cooling from passive heat transfer, so you will get a heat spike when the cooling system shuts down.
In point of fact, though, the heat spike is bogus. Think about it for a moment; at a constant temperature, the engine is producing X amount of waste heat, and the cooling system is dissipating the same amount of waste heat. You shut the engine off, and it's no longer producing waste heat; it's not going to get any hotter, it's just going to cool down. The coolant, however, which during operation has to be at a lower temperature than the engine in order for it to be able to remove the waste heat from the engine, will become hotter, as it absorbs heat from the engine but isn't being pumped to the radiator to dissipate that heat.
The reason that the 'engine' temperature rises when you turn off the engine is that it's not the engine temperature you are seeing; it's the coolant temperature.
A liquid-cooled engine relies on the coolant remaining a liquid; this is why a coolant leak is such an urgent problem. As the temperature of the coolant goes up, more of it boils, creating increased pressure in the coolant system, which raises the boiling point of the coolant, keeping it from boiling. When the pressure exceeds the system tolerance (the spring holding the pressure vent valve on the radiator in a car gets forced open) or the system is punctured, the loss of pressure causes part of the coolant to flash-boil. Steam, because it is much less dense, has a much more limited ability to cool the engine, and the temperature rises much more quickly, until it reaches a point at which the engine is damaged and fails.
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Originally posted by poopster
Wide have you seen the Roaring Glory tape on the P40 ?? The difference in start sequences with that and the rest of the Warbirds really shows how "dated" it was even then. Good tape. Actually I like all the Roaring Glory tapes. The ones with Jeff Ethell are really the best.
I haven't seen that tape, but would certainly enjoy doing so.
I have experience with the R-2800, R-2600 and R-1820 engines.
R-2800s require careful use of the primer or it simply won't light off, or you can get backfires and stack fires. Takes some practice to get proficient at it.
The R-2600 is somewhat less finicky.
Of the three, the R-1820 is the easiest to get started (steady prime) and reliable like brick and mortar.
I suspect that Funkedup has a Subaru WRX. The purpose of the water-cooled turbo is to prevent coking of the bearings after a hot shutdown. In the early days of car turbo installations, it was always a good idea to idle the engine for a few minutes to cool down the turbo prior to shutdown. God knows, I've replaced a few when the bearings went, which always destroys the turbo oil seals. Then the turbo becomes little more than an oil pump. I own a 2002 WRX wagon. My previous turbo cars included a 1980 Buick Regal T-type, a 1982 Renault Fuego Turbo, a 1985 Nissan 300ZX Turbo and my favorite road terror, a 1986 Shelby GLH-S. Later, I replaced the 2.2 liter, intercooled 175 HP GLH-S motor with the 2.5 liter, 217 HP engine from a wrecked Shelby CRX. 0-60 in about 5.2 seconds, 152 mph clothed in a Dodge 4 dr. Omni body. A genuine sleeper. Tremendous torque steer though. You develop forearms like Popeye.
Back when the GLH-S was introduced to the press, it was raced against a race prepared 1965 Shelby GT-350 at Willow Springs raceway. The dang 4 banger Omni on steroids turned significantly faster lap times than the 350 hp GT-350. And, that was with just 175 hp. With 217 hp on tap, my little black monster was a whole lot quicker. However, the GLH-S was unreliable in the extreme. Even as delivered it suffered from blown head gaskets and failed fuel pumps. When we did the engine swap, it had already been assigned weekend duty only. The engine swap was a nightmare. But that's another story.
My regards,
Widewing
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Originally posted by Widewing
As to the rise in temperature after shutdown: It seems that HTC modeled normal heat-soaking. All water cooled engines get hotter after shut down, because the coolant sits in the hot block and heads without being circulated.
My regards,
Widewing
Isn't that just the coolant getting hotter because it's no longer moving?
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Er.. um..
How can a turned off engine sustain 3000 rpm by windmilling alone??
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anyone care to explain it for the laymen? :o
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Widewing, that GLH sounds awesome! Did it have an open diff? Must have been a handful.
I didn't know you had a WRX too. I love mine, just hope it doesn't explode.
I couldn't find a diagram for the turbo cooling arrangement though. I guess I'll have to order the shop manuals.
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Originally posted by Kweassa
Er.. um..
How can a turned off engine sustain 3000 rpm by windmilling alone??
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anyone care to explain it for the laymen? :o
250 mph breeze will turn a windmill pretty darn fast. Unless the blades are feathered, there is more than enough power in the "wind" to keep that thing turning.
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The point is that all those people who were whining about a gamey advantage had not actually tested it out to see if it actually was an advantage.
I haven't decided if that is funnier than the people who were actually turning off their engines in a fight with the belief that it was helping them deccelerate .
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Turn, yes. But at 3000rpm?
250 mph wind has enough power to turn a propeller on a stopped engine as fast as when the engine would be running at full military power?? :eek: ?