LT-4 GDI Two Stroke Engine Design
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FormerVendor
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LT-4 GDI Two Stroke Engine Design Hi ALL, the SUPERCHARGED LT-4 engine can be run as a TWO STROKE with Cam/Timing Set modification.
MY QUESTION is about the required change in Camshaft Timing of the Valve Events.
What would be better, to machine a Cam Sprocket with a 1:1 Ratio ?
What would be better, to machine a Dual Lobe Camshaft ?
Lance
MY QUESTION is about the required change in Camshaft Timing of the Valve Events.
What would be better, to machine a Cam Sprocket with a 1:1 Ratio ?
What would be better, to machine a Dual Lobe Camshaft ?
Lance
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1:1 ratio cam sprocket, both valves open at bottom of power stroke, relying on supercharger to "push" air/fuel in, and "push" exhaust out until halfway up the compression stroke. How close am I? 2-stroke engines can never be as efficient as 4-stroke, in my opinion.
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1:1 timing chain seems like the easier approach. It's going to need some serious valve spring to handle the cam spinning at double the usual speed, though.
Can you do this with the rotary valve heads that you mentioned in another thread a while back?
Can you do this with the rotary valve heads that you mentioned in another thread a while back?
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I actually think the rotary valves are the way to do it.
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FormerVendor
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LS 376 = 5.3 with Forger 4.1 Crankshaft Hi Tony, yes a great point AND you could install one of YOUR 4.1" Forged crankshafts.
So I ASK, do you have a GDI 5.3 as the engine base ?
Lance
So I ASK, do you have a GDI 5.3 as the engine base ?
Lance
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In the snowmobile world its pretty easy to get 180 hp from an 800 cc 2 cylinder engine. Its small and light weight.
Increasing the cylinder count (within reason) increases the HP/cc at the cost of physical size/weight. This is because of increased cylinder surface area/displacment. The added cylinder area gives you more room for ports.
Examples:
1700cc 4 cylinder 2 stroke with 4 44mm carbs, 2 expansion chambers, and a turbo that makes a hair over 700 hp at 25 lbs boost.
990cc triple 2 stroke with 3 44mm carbs, 1 expansion chamber, and a turbo that makes a hair over 400 hp at 25 lbs boost
1500 triple 2 stroke 3 52mm carbs, 3 expansion chambers, NA 340 HP
2 guys can lift not just the engine, but the entire machine its bolted in as well
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3200 RPM should keep the valvetrain demands in the realm of a 4-stroke, which is nice. I was picturing a regular camshaft spinning at double speed.
Can you really do this with turbos? I'm guessing that the 2-stroke idea depends on low exhaust gas backpressure and would really require a supercharger.
Either way I'd guess that the compressor requirements would be similar to a regular 4-stroke compressor - 2-stroke vs 4-stroke probably matters a lot less than lb/hr and psi.
But I wonder if the valve timing and VE would be close to 4-stroke... if it requires less duration than a 4-stroke you'd need higher manifold pressure. Unless the tuned-pipe exhaust makes up for that? So many variables...
Sounds like a fun experiment. Is this for the same air boat customer that you were talking about earlier?
Can you really do this with turbos? I'm guessing that the 2-stroke idea depends on low exhaust gas backpressure and would really require a supercharger.
Either way I'd guess that the compressor requirements would be similar to a regular 4-stroke compressor - 2-stroke vs 4-stroke probably matters a lot less than lb/hr and psi.
But I wonder if the valve timing and VE would be close to 4-stroke... if it requires less duration than a 4-stroke you'd need higher manifold pressure. Unless the tuned-pipe exhaust makes up for that? So many variables...
Sounds like a fun experiment. Is this for the same air boat customer that you were talking about earlier?
Last edited by NSFW; Jul 31, 2018 at 01:35 AM. Reason: typo
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Air Boat DD MAX RPM = 3200 Hi NSFW, YES correct a DD Air Boat Application , RPM Limitation, due to "sonic" propeller cavitation problems.
I have three Twin Turbo Pantera customers who run a Supercharger, YES it works fine. (BOTH TT and ROOTS SC)
This method (both TT/SC) is a COMMON bus engine, two stroke, in operation for MANY years, well proven.
OK, Cam timing with MAX Seat to Seat of 180* AND a C/L of 90* would be my first attempt.
Lance
I have three Twin Turbo Pantera customers who run a Supercharger, YES it works fine. (BOTH TT and ROOTS SC)
This method (both TT/SC) is a COMMON bus engine, two stroke, in operation for MANY years, well proven.
OK, Cam timing with MAX Seat to Seat of 180* AND a C/L of 90* would be my first attempt.
Lance
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Most 2-stroke bus engines were 8V71 Detroit Diesel that had a scavenge blower (not really a supercharger, but integral to 2-stroke operation) and mid ports in the cylinders for the intake air. You are correct. QUITE common!
Later models were also turbocharged (8V71T and 8V92T(A))
Later models were also turbocharged (8V71T and 8V92T(A))
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For an engine at WOT, what do you consider an efficient BSFC, and what is SUCK fuel for power output BSFC?. Imperial units prefered