GM LS3 Hot Cam

Discussion in 'Chevy' started by TXFlyGuy, Oct 8, 2016.

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  1. Feb 11, 2017 #41

    AdrianS

    AdrianS

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    I know some people who are into powerboat (ski) racing. An hour at WOT - the guys who build those engines know what they're doing.
     
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  2. Feb 11, 2017 #42

    TXFlyGuy

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    As another auto-conversion expert on this forum will tell you, the manufacturers all test their engines at WOT for many, many hours. The small block Chevy has been tested in the field for decades.
     
  3. Feb 11, 2017 #43

    Toobuilder

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    A couple of points:

    The HP readout of a dyno is subject to proper application of correction tables, and shops who are "tuning" your engine have a built in inclination to show how skilled they are at pulling HP out of your engine... Not saying this is happening here, but be aware that fudging dyno numbers is a very common thing - even with the customer standing right there. Youtube is full of cars known as "Dyno Queens": they post big numbers on the rollers but dont back it up when it counts - the dragstrip.

    Again, is the Vne number indicated, or true? Big difference.

    Also, pointing the nose down, going fast, and slapping the stick without flutter is a good thing, but hardly a "full" flutter survey. Do you know what altitude this testing was done? Once again, altitude makes a big difference.

    I'm also highly skeptical concerning the "spin proof" wing. If Titan has somehow stubled across the magic formula to achieve this, it would be a huge breakthrough that has alluded all the other light aircraft manufacturers thus far. It sounds more like marketing hype to me. Be careful not to buy into that hype as you fly the airplane.
     
    Last edited: Feb 11, 2017
  4. Feb 11, 2017 #44

    TXFlyGuy

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    Did not say spin-proof, only very reluctant to spin, or nearly spin-proof. Titan (Bill) contacted an aerodynamic specialist in the area of wing design about this, actually unhappy with the difficulty to make the Mustang spin. They were told that this is what everyone in the aviation world wants, and to be happy with what they have!

    One more thing, the PSRU is a the upgraded heavy duty unit from Autoflight, New Zealand. It is rated for more than twice the power output from our LS3. This gearbox is a prerequisite for our 96" propeller.
     
    Last edited: Feb 11, 2017
  5. Feb 11, 2017 #45

    pictsidhe

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    I wasn't doubting GM engines, just the tendency for dyno places to add in HP. Track cars rarely spend more than a few seconds at WOT, then slow for a corner. That isn't as hard on an engine as holding the throttle open. Ocean powerboats often don't need to slow, hence suggesting that use. If you cruise at 240, you should redo flutter testing, or get Titan to do it. Ideally at 336 mph, though it hard to argue against straight down speed...
     
  6. Feb 11, 2017 #46

    Toobuilder

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    Keep in mind that IAS is used as a structural limit, not flutter. IAS defines the load of the air on the airframe and stays fairly constant with the indicator since the pitot tube is a force measurement device. Flutter is influenced by local airspeed, not force. The trap this drives a pilot into comes into play on a high power letdown from altitude at the end of a cross country. If he's in smooth, clear air and is letting down near, but under Vne (which many of us do), he better not be looking at the IAS, because if he's still up in the teens, his TAS is FAR higher than indicated and he can be way into flutter territory without knowing it.

    In your case, if the airplane is capable of near Vne speeds in level flight at altitude as you say, you are going to be at a much higher TAS. Better make sure you KNOW the TAS flutter limit.
     
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  7. Feb 11, 2017 #47

    TXFlyGuy

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    The race shop in question is highly respected around the country. Their experience shows that a 5 to 10% gain over GM posted numbers is easy. But this is the first time they have run an engine with a "backwards" facing short stack exhaust. With 100LL, and proper ECU/spark/AFM programming, the 10-20% increase in power is what they are speculating. We will know soon enough.

    I routinely fly descent speeds within 10 knots of Vmo/Mmo. That is unless ATC has us slowed down, or the arrival has numerous speed restrictions.

    The flutter concern is fully appreciated, and will be explored in depth.
     
  8. Feb 11, 2017 #48

    TFF

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    I think what is funny any of your questions is you have already spent the money before the question is asked. They are great starter questions for brain storming, but once you have already done it, you have to tell us how it went. You have already payed a lot for the correct answer, when your plane is flying will be the proof. Most of the answers you get are not wrong, but you already spec the hardware; your answer is frozen out of how it would have been tackled as clean sheet which is what most answers your are getting are focussed on. We can only watch you give us the answers in this situation.
     
  9. Feb 11, 2017 #49

    TXFlyGuy

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    Not exactly. The propeller manufacturer has been given the engine data, plus the PSRU gear ratio. He has what he needs to design the 96" propeller to be efficient, and still look the part of the Hamilton-Standard propeller. Whirlwind Propeller is fully aware of the mission profile that we have.

    Yes, the prop & gearbox & engine are already bought and paid for. But the testing phase and programming of the ECU/engine has just now begun.

    The prop is being designed with all of the above being taken into consideration. Including the power output with the GM Hot Cam, plus the potential for a 5% to a 20% increase over stock LS3 480 numbers.

    This is all a clean sheet design going in, as we knew what we wanted. That goes back almost 5 years ago when I first contacted Titan. They then told me that:

    1. A new high speed wing was in the design stage.
    2. A V8 (327 cu. in.) was in the future.
    3. A large diameter 96" propeller would be offered.

    We are the launch customer for all of the above. Except the LS3 is a much better engine for the Mustang than the LC9 327.
     
  10. Feb 11, 2017 #50

    BJC

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    Tex:

    I really like your project, and I enjoy following your progress here at HBA. Experimental aviation needs people like you.

    Please investigate the new airplane's (longer, thinner wing) engine and propeller (possibly sources of different driving frequencies than previous airplanes) flutter margin verses the new, higher speeds. A ground vibration test and flutter analysis, followed by a flight test program, could well save the airplane.

    Wear, and know how to use, a good high speed parachute. We like your posting here.


    BJC
     
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  11. Feb 11, 2017 #51

    TXFlyGuy

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    Well, a parachute is not really an option. But a complete nomex flightsuit, including full under garments has been purchased. Next on the "to buy" list is a flight helmet.

    The Chief Test Pilot for Titan will do all of the testing. I will not even be in the Mustang until this is accomplished, and to every ones' satisfaction.

    I do appreciate your (everyone's) general interest in the project!
     
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  12. Feb 11, 2017 #52

    pictsidhe

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    That's exactly what us armchair experts wanted to hear. Kit manufacturer in the loop and flight testing it. I hope it all goes smoothly.
     
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  13. Feb 11, 2017 #53

    pictsidhe

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    Pffft, like you won't try the seat and controls out in the hangar...
     
  14. Feb 12, 2017 #54

    TXFlyGuy

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    Well...you knew what I meant. ;)
     
  15. Feb 12, 2017 #55

    lr27

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    Does the kit manufacturer have the equipment to check for resonances in the drive train? If I'm not mistaken, you can have a PSRU that can handle up to the rated power, but certain combinations of the prop's moment of inertia and structural properties with certain RPM's (and maybe airspeeds?) might still make for a problem at lesser power.
     
  16. Feb 12, 2017 #56

    TXFlyGuy

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    The final drive ratio was selected with this in consideration.
     
  17. Feb 12, 2017 #57

    AdrianS

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    True - I have been involved in OEM dyno testing myself, and seen what the engines go through.

    But in the aftermarket world, most engine builders who strap a pair of turbos to a v8 don't expect it to run WOT for more than a few minutes at a time, unlike the powerboat guys. That's the point I was making.
    A GM cam, hot or not, should have no effect on engine reliability, as they will have done the testing.
     
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  18. Feb 12, 2017 #58

    TXFlyGuy

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    And that is why we went with the GM cam.
     
  19. Apr 3, 2017 #59

    wsimpso1

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  20. Apr 3, 2017 #60

    Winginit

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    Ski, here are two graphs. Both are Chevy engines and share the same pattern for bolting a reduction drive in place. The LS utilizes one fewer bolt but basically its the same configuretion. TxFly furnished the first graph for his Mustang conversion. Its a 480 LS3 dyno graph. He stated that he planned to operate the engine at 3600 rpms. If you look at his graph it reflects appx 290 HP available at 3600 rpms and an output of 425 lbs/ft Torque. Now lets move up to a graph for a modified BIG BLOCK Chevy. If we look at the graph for the Big Block and hone in on where its producing an equivalent 290 HP, you can see that it is going to apply 550 lbs/ft of Torque. Now in both cases we have 290 HP being applied to the gear box, but we have a difference of 125 lbs/ft of Torque being absorbed. HP has always been the golden child when advertising things, so I guess that why people expect to hear specs defined that way.

    Tx 380 LS.jpg bbc-697.jpg
     
    Last edited: Apr 3, 2017
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