Hi to all! I'm a new user, and first of all I want to thank everyone here for sharing a great deal of informations.

I have an offer to buy a W124 300TDT from a friend, so 603 turbo. I'm inclined to buy it, to make a Superturbo, probably the first and only in my country, Italy. My aim is about 400hp, street drivability, sleeper look, and not else. Now...what I need?

I was thinking:
1) a big turbo. Holset HX 40? My idea is to pump from 2.5 to 3 bar of pressure, and adjust the fueling accordly to avoid breakage, too high EGT, and black smoke. In a word, a whole lot of air, and only the necessary fuel. At what rpm it spools the HX 40?
2) w-a chargecooler. I plan to buy one rated up to 800 hp turbo petrol (supra etc). It should be enough.
3) uprated engine and oil coolers
4) uprated head gasket, or better ringed block
5) arp bolts
other than that, stock internals.

now my doubts:
6) I need a custom header, or a flange for Hx 40 on stock one could work?
7) injection pump from Myna Diesel? What do you think about PP Diesel, any experience?

Thats'all. I know it will be a loong job, and I'm still collecting info. So, any advice is very well welcomed.
Cheers

Hi Bobby,

I'm not a turbo expert but I will comment anyway jus to get you started:

You can get about 400-450 Nm through the standard automatic transmission,
but you are going to need more than that (600 Nm). You should get a
reinforced transmission (Siekkinen). Even 450 Nm requires tightening up
the adjustments, which you can do without removing the transmission.

1. The standard turbo pressure is 0.85 (91-) or 0.95 (-91). If you increase
this a lot you should check that the pressure in the exhaust manifold is
not increased too high. The risks include braking the connection rods or
melting something.

In order to keep the exhaust pressure low and to allow enough air
flow, you need a new exhaust pipe with large diameter and less air
flow resistance. A new exhaust manifold might be required.

You need also a free flow air filter.

2. I recommend a water-air IC, check what Frozenboost could offer.
People mostly use air-air, though.

3. If you have factory's towing hook on the rear and air conditioning,
you already have a separate transmission oil cooler under the right
front wing. Under the left wing there is a similar cooler for engine oil.
If you are missing either one, add it and a blower.

For that 400 hp power rating you are going to need a pump with 7 mm elements.
PPD is OK, Myna is suppousingly more advanced.

When calculating the required pressures and revolutions per minute,
keep the following in mind.

Power rating is obtained by multiplying torque with rpms. You need
more rpms than 4400, say 6000? Automatic transmission will not
allow a lot of rpms without changing to upper gear.

More torque is obtained by increasing the fuel injection. This is where
you need 7 mm elements.

More air is needed to burn the fuel. This is where you need IC, new
turbo, more pressure, exhaust pipe, etc.

Lets estimate... if you double the torque, you double the power.
This would take you to 300 hp. In order to get 400 hp, you need
33% more rpms. The modified pump increases the upper rpm limit and
delivers more fuel at upper rpm range. The standard pump gives
you reduced amount of fuel at 3400 (or some other rpm?) and up.

However, it looks like you should consider adjusting the gear box to allow
higher revolutions as well. Otherwise you can't get the power you need.

Look at the GT25 or so VNT series. You will want an EGT/EGP sensor. The Finns use fuel mapping as well.

it would be nice if someone would do a howto/shoppinglist in finnish too like JarkkoN wrote!

Believe or not, i haven't found one to this date.