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The factory supercharger will be way way to much of a restriction trying to make 400hp and it will grenade itself spinning it to 10k rpm. 

 

Dont know why you want to use the oem supercharger but are willing to replace every other component in the engine to make it rev and hold together

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1 hour ago, locost_bryan said:

Isn't that how the TSI engines work?  1 litre triple with 170Nm of torque from 2000-3500rpm or 2 litre with 320Nm from 1500-4500rpm.

Yeah but sounds like half of them break stock. 

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If you plan on wringing the engine to 10K a sequential system will be far better as you'll drop a lot of the parasitic load of the supercharger, more so again if you run it off a clutch, and you won't need as much intercooling to keep the IATs in check. Copy the TSI system and you'll probably be 'right

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Tbh I see no way of achieving this while retaining the Miller cycle aspect. They're not geared towards power.

You also have to remember that the supercharger on a Miller engine isn't actually operating as a supercharger as such, but more like a scavenging pump similar to that on a two stroke Diesel. You'd really want to look into what the stock blower is actually capable of, coz I'm betting it's fuck all.

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Inertia forces on rods goes up with the square of speed so you need waaayyyyy stronger rods to get to 11,000 than say 6000rpm. (about 3.3x stronger rods)
Not counting throwing 30-40psi down its gullet to acheive those power goals.
Levels at which any knock will blow it to smithereens so need E85 or similar

Doubling the RPM is also problematic for gearing and makes you prone to falling out of powerband with a standard box. 
Dropping 4000+ rpm on shifts would be painful.
Each gear now runs to twice the vehicle speed too which you can bodge a bit with a final drive swap but doesnt solve the ratio issues.

Generally speaking I do like the small motor light car concept. 
But I'd probably start with a bike motor and forget about any notion of bottom end power.
BMW S1000RR motor in a real light car would be my pick.

In the south island some clever chaps built a Toyota MRS that's about 650kg with near 400hp at the wheels with a turbo hyabusa engine. 
It's bloody cool but also a completely epic engineering feat.

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@Roman

Yes, good point about the rods and pins but remember the DIG-T-R got 283 ft-lbs at 7.5k on the clock, possibly with a stock bottom. The three cylinder profile makes for  a short, stout crank and I will probably try using the stock bottom on first try. If the build survives the dyno I figure it'll run well enough. The S/C will start phasing out @4500 and be completely off @6000. I haven't decided on how to achieve this yet so any suggestions here will be valuable. In full load mode, I will probably be running E98 but I was hoping for a flex fuel build.

 

@Yowzer

I've done a few LS swaps but fell in love with the concept of big power and moderate torque from a tiny lightweight engine. The Miller cycle is ECU selectable and if I'm clever about it, I can find a use for it. It looks like the stock roots blower makes 6psi, that should be fine for any pairing layout with a T/C.

 

@Dudley

Would you link me to the 4K and cam parts you would use?

 

@kpr

At 10.5K, I can be happy with ~220ft-lbs. That seems like an acceptible load for this engine.

 

@00quattro00

I'm looking at building a bunch of these as a kit. The total weight is likely to be <70kilo so I can imagine owners of older Holdens, BMW's and Passats being interested in it, hence the 3000lb reference.

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I have a fiat x1/9 that I'm wanting to repower and have looked at all sorts of small and light weight engines like various bike engines and the 3cyl vw and Ford but end up at the same conclusion is that its just easier and cheaper to grab a 2.0 turbo engine and dsg box from a golf gti and use that as its not a race car so I am not chasing every bit of weight saving and getting a gearbox that's going to work was going to cost a small fortune as well. 

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@00quattro00

I don't know why you're assuming the gearing will need replacement. It depends upon which car it goes into. Keeping torque below 250ft-lbs saves having to upgrade the rear which I've had to do with LS swaps, this kit will be an overall better bang for the buck than anything out there if I can get it to work as planned.

 

@cletus

That was not a built from scratch engine but a bored out Nissan HR12xxx triple with a new head. Losing the S/C got that engine down to a remarkable 40kilo. That engine used battery power to make the low end instead of the S/C. My approach is more wholistic and lighter overall when you include the battery pack 8^)

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10 hours ago, gmaslin said:

 

@Dudley

Would you link me to the 4K and cam parts you would use?

 

 

I've got a 4K sitting here with a 7/8 race cam. Makes all the power and ruts like a tang. Revs to 13,000

You can have it for $4k.

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@ajg193

Post some close up photos and provide an honest use history.

 

@Honda Ass Dragger

You sound like you know more about the DIG-T-R than I do, so I guess it'll be a trifle for you to tell us what they changed on the stock engine. I don't know exactly what they did but your last post implies you could enlighten me 8^)

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I'd use a decent sized turbo and blow it into a cooler and then into the supercharger, I would also add a decent sized wastegate after cooler + before the s/c, that bypasses the s/c once enough boost is achieved (say 15 to 20psi) letting the turbo take over in the top range but still giving s/c down low torque and twin charged in the mid-range, hopefully the factory s/c has the normal clutch pulley you can turn off at mid revs, making it sequential, and of course i'd use e85, maybe water/meth but e85 would be easier IMO

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@drftnmaz

Thanks for your input. The turbo I was planning on using is the G2.5-550. Taking @Yowzers advice, an inline setup:

1. would start spooling the turbo at 2500rpm because of the increased exhaust pressure from the S/C AND

2. make the clutch off of the S/C at 5500rpm the exact point where the turbo kicks in.

Is there a way to feather the clutch off in the 5000-6000 rpm range? This would help the transition between the two chargers and flatten the torque curve?

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