pantera_efi

iTrader: (1)

Hi All, my customer Dave Hartz (Water Thunder) has a requirement for a 5.3 AL LS engine (low weight) AND LOW RPM for MAX HP. (3600 RPM)

The "ride" is an Air Boat, direct drive Propeller, E-95 Fuel (local E-98 + race gas) Race ONLY !

I have chosen Twin Turbos, G25-550's, my 4.1 Forged crank kit, Crower Cams camshaft of 212/219 .621"/.557" 102 CL

The Small Port 5.3 heads with S/S valves (BBB), Truck Intake, my coils.

Will this engine produce 800 HP at 3500 RPM ( MAP of 32 Psi.) ?

Would there be a better turbo choice ?

Lance

Game ova

Assuming its loaded good (I know nothing about boats), I would think it will make 800 with ease at 32psi with nearly any choice of turbo.

ddnspider

iTrader: (26)

Is there a reason you didn't start with a 6.0 liter block? Low RPM's and cubes would make turbo choice/spool/lowend better with such a low max RPM.

shainiac

Game ova

I remember hearing years ago that boats are hard on crankshafts, almost mandatory for them to have a forged unit in place. Not sure if that's just an old wives tale or not.

MY_2K_Z

iTrader: (1)

Ya 800hp at 3500 is a good way to fold some rods and push water. Why didn't he go with a BBC seems that would have been a much better platform for building a stump puller.

hellbents-10

The small turbos will be hard to tune also, see EGR. I agree 800hp @3600 might not work with factory sized components. The main rod overlap will not be good with all of that stroke and the heads will be on their way off the block hahahaha.

I agree with the BBC comment but what a weight difference!

JoeNova

The compressor map for those turbos doesn't look like they'll be happy at 800 HP.
Any experience with the 4.1 crank in an aluminum 5.3 block? Rigidity becomes an issue with rod/stroke ratio in aluminum blocks.

jimmyg

So if it's direct drive I assume the propeller has a max rpm of 3600? Can you pulley it so you can get more rpm out of engine?

JoeNova

Can he not go with a less aggressive prop and increase RPM?

pantera_efi

iTrader: (1)

Hi All, I now have the GT25-550 turbos (RH/LH) AND the Turbosmart Waste Gates 40mm.

Lance




.
The compressor Map at 3 Bar is 40 .lbs@78%

NSFW

So the engine needs to flow 80 lb/min at 3 bar / 43psi, at 3500 RPM.

80 pounds of air is 28,000 liters/minute at sea level, 9,333 at 3 bar.
​​​​​
5.3 liters at 3500 RPM is 9,975 liters / minute.

So then the question is whether the exhaust output will drive those turbos to where you need to be on the compressor map. Not sure how to do the math on that, but my Subaru has a slightly larger turbo (52 lb/min) making 2.5 bar at 4000 with 2.5L, and that turbo is a couple generations old, so I'm guessing it'll work.

Wait. One more question. Did I get the math right?

littlefield

pantera_efi

iTrader: (1)

Hi LF, YES a good point, yes we have a thrust bearing.

I want all to observe the size of the Turbine.

Lance

Dead Hook

Lance are these the mirror image turbos we spoke about?

pantera_efi

iTrader: (1)

Hi Hook, yes.

Lance

gametech

iTrader: (1)

I have to ask about the rpm constraints. Is this driving some sort of class spec variable pitch prop or something?

littlefield

tblentrprz

Why not build engine based on power requirement (depending on cubic inch = rpm range) and then gear for prop speed?

pantera_efi

iTrader: (1)

Hi TG, sure MOST Air Boats (LS powered) use a Gear Box (1 : 2 prop reduction) at a cost of $2000.00.
SURE the cost of a proper Twin Turbo with Turbosmart WG is about 2X that amount.
The Air Boat weight is 1000 .lbs with operator.
The Gear Box Weight is 100 .lbs OR 8% less weight with a DD. ( including the TT's)

Thus Dave, Water Thunder, has a good reason to create a DD Boat.

Lance