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Help with Engine.

  1. Aug 25, 2009 #1
    Dear Sirs;

    I have an engine design project that I am working on. Once I have calculated the mass of the moving parts, i.e., piston, crankshaft. etc., I need to find the equations and the related information to be able to calculate the power necessary to drive it. Can anybody direct me to a Website that can help. Please. :cool:

    Life, Health, Prosperity,
    HotepMichael
     
  2. jcsd
  3. Aug 25, 2009 #2
    Can you give us some more information about the project, such as what type is it (personal, academic, etc)?

    What are the aims?
    What type of engine is it?

    Also do you just want to rotate the engine components or acutally drive something off it? By the way working out exactly how much torque/power is needed is very complicated as it depends on more than just the reciprocating and rotating masses. You'll need all sorts of crap like cams, how many valves, how stiff are the springs etc, not even getting on to ancillaries.
     
    Last edited: Aug 25, 2009
  4. Aug 26, 2009 #3

    Ranger Mike

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    see the folowing posts ..i think these are in mechanical engineering forum..lot of background things to consider!

    Engine size/type (ie. 2L inline-4) and fuel consumption

    Horsepower - Please help - Confused! posted 14 Feb 2009

    Volumetric Effeciency
     
  5. Aug 26, 2009 #4

    Danger

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    Welcome to PF, Hotepmichael.
    To start with, I'm not a 'Sir'; I'm a Danger. I'm 'Sir' only to people that I don't like.
    Secondly, your question (the part that I quoted) confuses me somewhat. An engine is supposed to provide power, not absorb it. Do you mean what sort of starter you would need to fire it up? As Chris mentioned, there are dozens of factors that determine that. Valve spring tension, reciprocating mass, compression... they all matter. For instance, I had to have a custom 3.5 hp starter built for my Roadrunner because any normal one fused its windings. That's 446 ci with 12.5:1 compression ratio, which has to work at -45° C on an engine with power steering (the pump adds to the resistance of the thing to turn over). I have a 690 amp tractor battery in the trunk, paralleled with a 350 amp automotive battery up front, and the sucker would drain them both if it didn't fire up within 2 minutes of cranking. My wife's minivan, on the other hand, has a battery that would barely power a flashlight, and I can crank the damned thing for 15 minutes to get it started in the cold.
     
  6. Aug 26, 2009 #5

    Ranger Mike

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    Danger..I sold my 1968 Roadrunner to buy the formula car..was 400 CID block and stroked 440 crank..493 CID..12 to one Arias pistons, .610 Dynamics cam, roller rockers, hemi oil pan of course, 850 CFM Holley carb, hooker comp headers into 3 inch exhaust, B&M trick torque flite , 3000 rpm stall converter, 3.91 gears in new sure grip differentail..new hemi 7 leaf springs and the good pinion snubber, 8 inch cragars on the rear , 6 inch on the front, just about all the trick stuff..at least 575 HP if not more..what a torking mill...i thought there was something good about you!!
    mopars ferever!!
     
  7. Aug 26, 2009 #6

    Danger

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    Damn straight!
    Mine is a wee bit weird; it's literally the only one of it's kind ever built (as of when I bought it). It's a '72 GTX model. The original owner (I bought it in '75) worked at the Chrysler plant in Windsor. He followed the car down the line and put every nut and bolt in the thing himself. It came out of the factory with stuff that wasn't available on production models. For instance, Roadrunners came with bucket seats. He had a kid that he wanted to be able to sit up front with him and his wife, so he put in a split bench front seat that was made for a Polara station wagon. It also had Hurst air shocks, with the air tits screwed into the bottom of the rear bumper. (I replaced them with Striders set to 'extra firm'.) Normally, that model would have the regular rally wheels. Mine has them up front, with 8" Tiger Paws, but the rears are slotted chrome-reverse with 10" Goodyears. (Still have the original wheels on it, but I swapped the tires for equal size all-season radials.) He bent the interior sheet metal of the rear fender wells up for tire clearance. The badging is in the wrong places.
    What struck me most was the power of the thing. According to the VIN, it has the high-perf 440 (mid-way between the regular and the 6-pack models) which was factory rated at 290 hp. This thing was putting out more like 400. The factory redline was 5,500 rpm; the valves floated at 6,500, so I shifted at 6,400. I'd go into 2nd gear at 65 mph, third at 85, and 4th at 115—and 4th is a .73:1 overdrive.
    The weirdest thing showed up when we took it apart. As a fellow Mopar man, you probably know that 440's don't like to oil the #4 rod bearing very well. When I was on vacation in the Ottawa valley one year, that fact made itself known in a spectacular fashion. The bearing spun out, the piston collapsed, and it took the bore with it. My cousin, who I was staying with, had a friend who was an excellent mechanic, so I took the car to him. He talked me through what he planned to do, and I agreed with him. It started with a .030 overbore. We then inserted the 'race-only' 12:1 aluminum TRW pistons (they use a 1 16th inch ring rather than the standard 1 8th). The normal ring gap is .032; we set mine at .008, so it's almost a total seal. Moreover, we mounted the pistons backwards; ie: those meant for the left bank went on the right and vice versa. That reversed the wrist pin offset, and essentially eliminated friction on the stroke. It naturally induced significant piston slap at the top and bottom, so the thing sounds like a coffee can full of rocks, but it was good for about an extra 35 hp and boosted the compression to 12.5:1. The rings on those pistons are rated for about 10 passes on a 1/4 mile strip, but I put 35,000 miles on them with no problem. Now for the weird part: when we took it apart, we were startled to find that it had 6 10:1 pistons and 2 8:1's. It also had 6 4-barrel rods and 2 6-pack ones. The off-size pistons were not connected to the off-size rods. About 10 years ago, I figured that it was Bruno's way of balancing the motor. As I said, it ran like a turbine at 6,400 rpm.
    I have since added a Moroso deep sump pan, an Edelbrock CH4B 'Performer' manifold with a 750 double-pumper, Blackjack headers, a home-made methanol injector, a Hayes disk and throwout bearing with an 1,100 lb McCloud pressure plate and, unfortunately, a totally inappropriate cam. Going to switch that up to either a Street Hemi grind or a Mini-Express.
    I haven't driven the thing in over 25 years, but it was putting out about 650 hp then. Can't wait to see what it does with a new cam and maybe a nitrous kit. :biggrin:
    As to the gearing, it is an A833 four gear with a 3:23 Dana 60.
     
    Last edited: Aug 26, 2009
  8. Aug 26, 2009 #7

    Ranger Mike

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    you are correct about the oiling problem. we cured this by running an aeroquip external oil feed line to the front of the oil gallery..seems tthe oil under pressure does not want tomake the 90 degree turn to properly oil that lifter/bank when the mill is spun up to hi revs..the oil pumping from the feed line in the other direction counters this..also blocking off the oil passages to the valve train wil keep more oil downstairs and prevent a lot of oil drianin back to the pan. oil is like taffy and that is why Mopars have windage trays to eliminate this,,adds 10 HP too...good show on reversing the pistons..more hp but a little noisy..
     
  9. Aug 26, 2009 #8

    Danger

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    Very cool idea about the oiling. I'll incorporate that when I get her running again. (If I get her running again. It's going to cost over $50,000 to put her back on the street, and I'm on Social Assistance (Welfare, to Yanks).)
    That is, of course, if I can't manage to put together the new engine that I designed for her. I'm figuring about 2,000 hp if it works properly. The first step is a titanium frame.
     
    Last edited: Aug 26, 2009
  10. Aug 28, 2009 #9
    I thank all of you for the reply. The engine will be a single cylinder reciprocating engine. There will be 2 flywheels, one on each end of the crank. This engine will spin at 3600rpm's.
    I haven't completed the designs for the piston, crank, connecting rod, and flywheels as I write this thread. If I had the mass of all the moving parts and knowing the rpm's, is it possible to calculate how much energy is necessary to move/rotate them at 3600 rpm's:uhh:?
    What other information is necessary for these calculations?:confused:
     
  11. Aug 28, 2009 #10

    Danger

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    I'm afraid that I still don't understand the question. It obviously doesn't refer to a starter, as I originally surmised, since they take the engine only to lower than idle speed.
    Do you perhaps mean how much gasoline/air mixture that you will need to ingest to reach the desired rpm's? If so, much more information is required.
     
  12. Aug 31, 2009 #11

    brewnog

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    No, you can't predict that just given component masses. The FMEP is characterised by breathing, friction, and pumping losses, and has little to do with component mass.

    Fuel consumption at idle is a tricky thing to predict (it's not even easy to measure). If you have a predictive model for engine power vs specific fuel consumption, you can draw a Willans line and predict what the fuel consumption would be at idle, but it doesn't sound like you've got this far.

    You do understand though, that the energy input will need to be much greater than that needed just to "spin at 3600rpm" if you want to extract any useful work out of the machine?
     
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