I don't see it ever happening. But I'd like to see it... What turbos did you have in mind?

 

Boost = fuel = no mpg. Come back to planet earth.

 

If you want big block tq down low with a stock long block your going to want to do a roots blower setup .

Here's an old dyno pull on mine .


Remember also that the ecoboost has ( correct me if I wrong) electronically controlled VVT turbos .

A twin turbo 4.8 would be awesome. Don't get me wrong , but if you want low end grunt I don't think it's the correct way to go for that . They like to be revved and like said while in boost your mpg goes to hell .

I would start off with a 6.0 instead .

 

I like these kinds of projects...ones that require some real thought. I bet it could be done. But you'd either need a pretty exotic, unconventional turbo setup or a blower. Not to mention a dyno that will bring the RPMs down to 2000 to be able to get a reading on that number. I also might run a high pressure spring in a high volume oil pump to protect the bearings at that low of an RPM.

 

I was gonna say why not do a 6.0 aswell, that would be more toquey, but I guess your fuel economy would go out the window....

Let me go take a picture of my dyno sheets and you can look at them

And a supercahrger is gonna make more torque faster than a turbo like mentioned

 

After driving around a little bit I've figured out a couple of things. At 70mph I'm turning 2300-2400rpm which means I'd be driving around in boost all the time. Bad for mpg's. Shore it wouldn't be much but with the small turbo's giving it any gas at all would be instant spooling.

Second I'd like to have this motor live 150k miles. So I do not want to go over 10lbs of boost.

I know mileage isn't going to be great and I'm fine with that. When empty it gets 13 now so I'd like to see up around 17 maybe to make me happy. May only get 15-16. Won't be driven every day so that's not to big of a problem.

I'm thinking of using factory 300zx turbo's or maybe a small upgrade to factory 300zx turbos. T25 I think. I know my old z full spooled about 3000rpm's. Liters per cylinder is grater in the z so I don't think the extra cylinder of the 4.8 with completely screw me.

 

I think if I hit peak(500lbs) of tq in between 3000-3500 I should be happy. The torque Will ramp up fast. If my internals hold it should ok. The short stoke of the 4.8 should help in that aspect.

 

The stock 454 is rated at 410ft lbs at 3200. Anyone think that's possible with a twin turbo 4.8l?

 

Yes if you can hit full boost early, but unless the 4.8 is built up some it will be really tough. Let's say you make 200ft/lbs at 3200 in stock form. Using boost only in an ideal world you would need roughly 1 atmosphere of boost or about 15lbs. An ideal Cam is going to be tough to spec for this build, because you can't afford to lose bottom end. Add some compression by milling the heads. Getting ported heads will only help a little bit down low. The isky triple12 will be very close to what you need. I am guessing you can make about 250tq at 3200rpm NA. So if you can make 10lbs very early you can make around 410@3200.

 

I figure a short duration high lift cam would do it. Gasket match and smooth the intake and exhaust ports. Other than that it will be stock.