Thread: 300 TDi Torque/Power Curves

Originally Posted by uninformed

there is a 3.0 common rail version??? whats that in?

Have no idea but it used to be on their website, think it might've been a 3 valve OHC version but the block architecture looked like a Tdi !

Originally Posted by Dougal

Maybe if you spun a hiclone really fast it could help.

Pretty much any T28 turbo will work to compound the 300tdi. But the bigger exhaust housing the better. Set them for ~10psi and wind the original turbo wastegate in a bit. Should give you a solid 20psi by ~1800rpm in all conditions and even at high altitudes should provide 20psi by 2000rpm.
Can be wound up to over 30psi. But that would be asking for trouble unless you have a lot of supporting modifications.

The turbo I have used for my recent calcs is a bastard T25 with an odd turbine. It's close to useless for more performnace in the original application but close to perfect for this one.
Hopefully I'll get a chance to try it one day. I now have a 300tdi to play with.

Either setup will trump a VNT turbo for performance at all operating points. Not to mention reliability and cost.

What is the difference between our turbo and a T28?

Specifically, will a T28 come on boost sooner? If so is that how the benefit is achieved?

Originally Posted by kreecha

What is the difference between our turbo and a T28?

Specifically, will a T28 come on boost sooner? If so is that how the benefit is achieved?

Not replacing the current turbo with a T28. Adding a T28 to the current turbo. One feeds boost into the other.

T28 is roughly two sizes bigger than the original.

Originally Posted by Dougal

Not replacing the current turbo with a T28. Adding a T28 to the current turbo. One feeds boost into the other.

T28 is roughly two sizes bigger than the original.

So if its bigger and it is supplied cooling exhaust gases from our standard turbo, what process takes place to achieve superior performance (more boost in lower rev range) to a VNT?

Originally Posted by kreecha

So if its bigger and it is supplied cooling exhaust gases from our standard turbo, what process takes place to achieve superior performance (more boost in lower rev range) to a VNT?

Wider operating range and higher boost possible across the entire operating range. They also look after themselves better, no complicated control and vane position feedback required. Mechanically they are a lot more reliable and more efficient.
Many production diesel cars and trucks have dropped VNT for compound turbocharging.

It works by feeding your existing turbo some boost, which your existing turbo compounds into higher boost pressures. This creates more exhaust gas which drives both turbines harder. The result is a lot more boost sooner than you get with either turbo individually.

Ok so if I try to rearrange your words;
If our turbo is "out of its map" at 14psi boost and the T28 feeds the our turbo then because the supply air is higher than atmospheric pressure our turbo is back "in its map"?

Or using bogus numbers....
At 1600rpm our turbo makes 6psi.
If we use a T28 to feed it, at 1600rpm we might make 10psi.

Originally Posted by kreecha

Ok so if I try to rearrange your words;
If our turbo is "out of its map" at 14psi boost and the T28 feeds the our turbo then because the supply air is higher than atmospheric pressure our turbo is back "in its map"?

It gets complex pretty quick. Turbo maps run on pressure ratios, multiples of the inlet pressure.
6psi from 14.5psi atmospheric is a PR of ~1.4.
If you feed the turbo 3psi (plus atmospheric) and it's still giving a PR of 1.4 then you've got ~10psi.

But. That 3 psi extra is also driving more exhaust flow so the small turbo can do a little better again.

Originally Posted by kreecha

Or using bogus numbers....
At 1600rpm our turbo makes 6psi.
If we use a T28 to feed it, at 1600rpm we might make 10psi.

Or possibly 15.

I went through trying to reverse engineer the 300tdi original turbo and I got ~5.5psi at 1500rpm.
By increasing the fuel I think ~7psi is all you're going to get.
Compounded with a T28 I got ~14.7psi and not many more rpm to hit ~20psi. This combination has no problem doing 30psi, but that would be silly.
I got the same ~14.7psi compounded with my mystery turbo, but the higher rpm is much better with much reduced exhaust manifold pressures.