Technical Uno Turbo fitted with Saab turbo, why only 0.4 bar?

[scona]

hi all.after some advice.put garrett t25 turbo witch came off saab 9000 2.3 lpt,the turbo was rebuild by midland turbo with no problems,ive fitted it ti my mrk 2 uno turbo.but boost is low,about 0.4,my old garrett t2 boosted to 0.7,but was leaking a lot oil and was cracked,any idieas what it could be,thnks

 

[alexGS]

I have renamed your thread from 'uno turbo' in the hope that you might get more replies

I don't know a lot about turbos but my first thought as an answer to your question is that the turbo might be mis-matched to the engine?... sorry... perhaps the turbine is not suited to the exhaust gas flow from an engine that's little over half the size of the one the turbine was designed for?

Then again, boost pressure isn't everything - if it generates good volume at low engine speeds, that can be a useful help for torque, and that was Saab's thinking with the 'low pressure' turbo that you have. So I'm not convinced that having 'only' 0.4 bar is necessarily a problem. What was the boost pressure in the Saab installation? Bear in mind the FIAT installation is limited to 0.6bar if I remember correctly, and it is obviously still effective at that pressure. Why not give it a little while to see how it performs in all conditions... and measure your fuel economy, too...

-Alex

 

[scona]

I have renamed your thread from 'uno turbo' in the hope that you might get more replies

I don't know a lot about turbos but my first thought as an answer to your question is that the turbo might be mis-matched to the engine?... sorry... perhaps the turbine is not suited to the exhaust gas flow from an engine that's little over half the size of the one the turbine was designed for?

Then again, boost pressure isn't everything - if it generates good volume at low engine speeds, that can be a useful help for torque, and that was Saab's thinking with the 'low pressure' turbo that you have. So I'm not convinced that having 'only' 0.4 bar is necessarily a problem. What was the boost pressure in the Saab installation? Bear in mind the FIAT installation is limited to 0.6bar if I remember correctly, and it is obviously still effective at that pressure. Why not give it a little while to see how it performs in all conditions... and measure your fuel economy, too...

-Alex

hi,thnks for that,i spoke to midland turbo and he told me to adjust actuator quater of turn back,said some thing about saabs vacum on saabs which is controlled by ecu,thts why low boost,also been told to put my actuator off my garrett t2 if its same length and it will boost more,i was told by fitting t25 i would get betta boost ect.

 

[gtirx2]

Normally you would preload the actulator by around half a hole.
As in the hole in the end of the aculator rod should be half a hole offset from the peg on the wastegate flap and you pull the actulator rod over the peg to preload it and hold the wastegate shut.

 

[scona]

Normally you would preload the actulator by around half a hole.
As in the hole in the end of the aculator rod should be half a hole offset from the peg on the wastegate flap and you pull the actulator rod over the peg to preload it and hold the wastegate shut.

oh,i didnt know that. thnks

 

[scona]

ive adjusted wastegate bar to as far as it goes and its lot better.but boost gauge is only going quater way up,can you get a upgraded actuator at all?surely by putting on garrett t25 i should be getting more boost than the t2

 

[lewey]

I'm not a turbo guru or anything, but using a turbo designed for a car with 1 litre more displacement than yours might not be the best. As Alex points out, you may not be generating enough volume and velocity of exhaust gas to make the "large" turbine move at sufficient speed to generate the boost you want. This is why people generally use hybrid turbos when using T25 fitments. With my fairly modest hybrid T25, I didn't get full boost until 4000RPM. Without the small turbine, blade mods and very efficient internals, it is conceivable that it would never get there.


Having said that...
You may be leaking boost somewhere. The fact that you are overcoming the actuator says you must be making decent boost at the turbo? What should the turbo be putting out pressure-wise in the SAAB with the standard actuator? It sounds like you are getting this?

 

[turbo1.9]

Hello, the Saab turbo TB25 from stock only boost at 0,4bar people fit them in his 1.4 Uno Turbos, and raise the boost until 1,2 bar (disconnect the security boost switch at left of intake manifold), they fit Croma 240cc injectors, and they have 170HP with stock cam.At idle richer mixture....
More than 1,2 bar is no good for the turbo.
Full boost can be around 4800-5000 rpm.

Regards....