g day i have a datto 1000 that im about to fit a turbo from the vg30det nissan v6 it does not look too much bigger than my currant turbo but it is a roller bearing ceramic unit do you rekon it will be too big? im thinkin of running 2 plus bar?

I think the turbine blades will say by-by at about 1 bar. They dont like any more than 0.9 bar boost.

i was thinking that the exhaust loading on a 1500 would be half as much as a 3000 at the same boost and revs? or is it somthing else that makes these tarbins fail?

The problem is that the method they use to bond the ceramic exhaust wheel to the shaft fails at anything more than about 12 psi, sending the exhaust wheel down the exhaust.
It has nothing to do with the exhaust being produced by the engine, but more the speed that the turbo is allowed to boost to.

so the turbo has got to spin at the same speed to produce say 10 psi on a 1500 as it does on a 3000 or even a 5000 at 10 psi?

By rights yes as at the same RPM of the turbo it's gonna produce the same air flow which in essence creates boost. Depends on the size if the piping to I think
Cheers
Damo

Some thing for a bit of debate for the turbophiles. Pick the holes in these comments.: -

The speed the turbine spins at for a given engine speed is determined by -

1. Volume of exhaust gas flowing into the turbine.
(More gas from bigger engine = more turbine speed). 1500cc engine will produce approximately half the gas from a 3000 cc engine at the same engine speed.

2. A/R ratio of the turbine housing.

The higher the A/R ratio number, the slower the exhaust gas speed but the less back pressure the engine has to work against. (Off boost response improves.) Smaller engines use lower A/R ratios to increase gas speeds at lower Rpm.

3. Turbine blade trim

(coarser trims accellerate the turbine quicker at lower Rpm, but create back pressure at higher gas volumes) Smaller engines usually use coarser trim blades to get speeds up at lower rpm.

4. Pressure of the exhaust gas.

(More pressure = more turbine speed up to a point). Increased gas pressure can be obtained by changes to exhaust cam profile. Opening exhaust valve earlier allows higher gas pressure, but reduces energy input to crank shaft. Trade offs abound.

5. Compressor wheel diameter ratio's trims.

(Larger wheel trim ratio's give greater flow at lower engine speeds). They also require greater amounts of energy to make the same amount of boost pressure that a smaller diameter wheel will, even though they have greater flow. On smaller engines, smaller compessor wheel diameter ratios allow the engine to make higher boost pressures with reduced flow, without creating excess exhaust back pressure.

6 Compressor housing A/R

The A/R of the compressor housing helps determine the amount of air that the compressor can produce without losing efficiency. The larger the A/R ratio, the more flow for a set turbine speed and pressure. Smaller engines use smaller housing ratios. This allows higher boost pressures with reduced flow rates.


With a VG30 turbo on an A15 it will take twice the normal amount of engine speed to produce the gas flow to get the compressor on boost. The A15 also uses half the air of the 3000 cc as delivered by the compressor. This means, the ratio of boost pressure to exhaust back pressure remains the same on both engines. (It just means the whole compressor map is moved up to twice the engine speed of the VG30T engine)

If the turbo came on boost at 2000 on the VG30,I'm tipping it will come on boost at approximately 4000 rpm on the A15.

It will probably go like hell at higher engine speeds but I think it will be a bit soft at speeds below 4000 rpm though.

I did put my A14 garret to3 (from saab 900) and it has been really good.
I

Hey Finn what HP are you getting out of your setup?????

I'm interested in what HP people are getting out of their turbo setups
Cheers
Damo