Briggs vanguard conversions

Discussion in 'Firewall Forward / Props / Fuel system' started by Hephaestus, May 12, 2019.

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  1. Oct 15, 2019 #1241

    TiPi

    TiPi

    TiPi

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    This is no different than any other engine hanging on a fixed pitch prop. My Rotax 912 ULS is pitched for about 5,250 - 5,300 static, will run 5,300-5,350 in slow climb (65kts) and get to 5,650 WOT at sea level. Redline is 5,800. So I don't have a 100hp engine anymore☹️
     
  2. Oct 15, 2019 #1242

    Hephaestus

    Hephaestus

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    Well here's where mine stands.

    I'll see what the builder says about YouTube hosting the video of it's first dyno run.

    38hp at 3800rpm, 46lbft at 2600. Running 3psi of boost. 10minute run on the dyno static load, 3800rpm - required ~250cfm per head to maintain 280° CHT.

    Now, porting work, connecting rods, high volume oil pump, new custom cam and installing a proper oil feed for the turbo.

    Hopefully next run early December.
     
  3. Oct 15, 2019 #1243

    pictsidhe

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    280F?
    What does it weigh? What is on it for that weight? Bathroom scales will do just fine.
     
  4. Oct 15, 2019 #1244

    pictsidhe

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    Whoah, hang on, 52 ftlb, from 627cc? With 3psi boost and no porting?
     
  5. Oct 15, 2019 #1245

    Vigilant1

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    Commercial dyno? Supervised by the guy who did the mods?:cool:

    The PSRUs do let em spin fast and still turn a decent size prop.
     
  6. Oct 15, 2019 #1246

    Hephaestus

    Hephaestus

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    That's what his computer says, it's a lot lower than I'd have expected too.

    Of course now you can begin the argument as to whether his Dyno is accurate. To me it's a relative # same with the HP. Since I don't think any department of weights and measures actually verifies data.

    The torque peak was way below where the calculators said it should be too.
     
  7. Oct 15, 2019 #1247

    pictsidhe

    pictsidhe

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    If that 500cfm is dissipating the entire heat of the engine, it would have a delta of around 120C.
    I am more than a little sceptical of the dyno.
     
  8. Oct 15, 2019 #1248

    Hephaestus

    Hephaestus

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    No clue, not even in the discussions right now. Reliability first, power second then we move on to weights.
     
  9. Oct 15, 2019 #1249

    pictsidhe

    pictsidhe

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    Lower? It seems awfully optimistic to me. Allowing for the boost, it's still a 28% increase in torque over standard.
     
  10. Oct 15, 2019 #1250

    poormansairforce

    poormansairforce

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    How? According to the info the torque peak is being registered at 3800 at 52 ft lbs as mentioned.....something is wrong?
     
  11. Oct 15, 2019 #1251

    Hephaestus

    Hephaestus

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    He is a true bayou redneck who builds motors for a living (mostly swamp/airboats). So yes it's his own personal dyno and when it comes back we can do club props.

    Mods at this point really don't exist other than intake and exhaust manifolds.
     
  12. Oct 15, 2019 #1252

    Hephaestus

    Hephaestus

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    Where'd the 52 come from?
     
  13. Oct 15, 2019 #1253

    pictsidhe

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    with 3psi boost (~20% over NA) and no other mods, he has somehow boosted torque by 56% over the stock torque at 3600rpm.

    Sorry, seen claims like this far too many times...
     
  14. Oct 15, 2019 #1254

    pictsidhe

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    38hp at 3800rpm
     
  15. Oct 15, 2019 #1255

    poormansairforce

    poormansairforce

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    Thats what 38 hp at 3800 rpm calculate out to so 46 is not the peak.
     
  16. Oct 15, 2019 #1256

    Hephaestus

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    I'll have to ask. I make no claims of being an engine building guru.
     
  17. Oct 15, 2019 #1257

    mcrae0104

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    I have been reading through old issues of Experimenter lately more than I've been keeping tabs on HBA.com, but how could the following article not make me think of this thread? Perhaps not much has changed in the intervening 71 years...

    image.png image.png
     
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  18. Oct 15, 2019 #1258

    BBerson

    BBerson

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    So if your engine is rated at 100hp at 5800 rpm, and you only get 5650rpm at wide open throttle in level cruise, then you have a cruise prop and you never see 100hp in normal flight.
    The important number for the airplane designer to know (using this engine) is what hp is available for climb at 5350 rpm. The 100hp at 5800 rpm is not relavent.
    Now if you install an extreme climb prop then you can cruise at 100hp with 5800rpm.
     
  19. Oct 15, 2019 #1259

    pictsidhe

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    28hp at 3800rpm with 3 psi boost would be about right.
     
  20. Oct 15, 2019 #1260

    TiPi

    TiPi

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    These numbers are plausible:
    The original engine has a ve of 70% and a torque of 43.5Nm.
    Going to 100% ve is already an increase to 62Nm
    Add the 3psi boost (+20% ve) takes the torque to 74Nm (54.5lbf.ft)
    Torque on a turbo engine will increase with rpm as the turbo kicks in so "peak torque @ 2,600 rpm" is not peak, seems to have ben recorded at that rpm as this is the default "peak torque rpm" for industrial engines.
     

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