Turbo conversion advice!!??

[Goldenb19]

Hi all im currently rebuilding a Vauxhall Signum 3.2 engine to swap with the 2.5 engine thats in my Vectra Supertouring V6 and iv started thinking about also adding the Low Blow Turbo setup from the saab 9-5 3.0 Turbo!?

The engines are all basically the same GM block but with bores and strokes so the saab turbo will all bolt staright on however iv had mixed oppinions on the compresion ratio of the 3.2!

the 3.2 ratio is 10.0:1 and the turbo runs at a low 3.6 psi aimed at low tourqe im planning on tuneing the engine for max bhp and should sit around 240bhp but the mods i make will sacrifice tourqe :/ hence my thinking of the saab turbo to make up for this!


all opinions welcome im just V6 N/A orientated and dont know much about turbos!!

[Scuffers]

10:1 is pretty low cr, so 3-4psi should be no problem at all, however, its also bigger all boost!

[Goldenb19]

hi thanks for your reply dont get the last bit?

[Spoof]

Think he means 'bugger'

[morgrp]

surely it would be easier to buy a whole 3.0 Saab unit and fit that if the blocks are the same? or are you at a stage where you are too committed with rebuilding the 3.2? Most Saabs cost about 58 pence these days so finding a cheap one should be easy

[morgrp]

I'd also be wary of internal components on non turbo engines - Whilst they are the essentially the same block, the internals could be vastly different. My experience is with Volvos and whilst non turbo and turbo models all share the same heads and blocks, the internal components vary massively from things like cam shafts and timing, to sodium cooled valves and additional oil squirters etc

[Goldenb19]

no thats why im asking questions now!! iv stripped down the 3.2 and bought a new oil pump thats all atm
the saab unit is lower compresion from what iv read but only 200bhp the 3.2 i can get to 240bhp

[Goldenb19]

morgrp said:

I'd also be wary of internal components on non turbo engines - Whilst they are the essentially the same block, the internals could be vastly different. My experience is with Volvos and whilst non turbo and turbo models all share the same heads and blocks, the internal components vary massively from things like cam shafts and timing, to sodium cooled valves and additional oil squirters etc

yea noted the internal diffrences are

the saab 3.0 is low compression has double wound valve springs on front bank and under piston oil squirters

the 3.2 however has sodium exhaust valves and a steel crank but no double springs or oil squirters

[Mave]

What power does a tuned saab engine make compared to your 240BHP target? Might find that the hot side of the turbo limits your airflow at higher power, so its probably worth checking how much power can be squeezed through it.

[ivaylo]

Correct me if I'm wrong but wasn't the Saab engine with asymmetrical turbocharging (front bank only) hence the low horsepower? The 54-degree GM V6 wasn't particularly suitable to turbocharging due to overheating cylinder 6 if I remember correctly. The 3.2 should be able to make 240-250bhp naturally aspirated.

[CraigyMc]

morgrp said:

I'd also be wary of internal components on non turbo engines - Whilst they are the essentially the same block, the internals could be vastly different. My experience is with Volvos and whilst non turbo and turbo models all share the same heads and blocks, the internal components vary massively from things like cam shafts and timing, to sodium cooled valves and additional oil squirters etc

This.

[Goldenb19]

ivaylo said:

Correct me if I'm wrong but wasn't the Saab engine with asymmetrical turbocharging (front bank only) hence the low horsepower? The 54-degree GM V6 wasn't particularly suitable to turbocharging due to overheating cylinder 6 if I remember correctly. The 3.2 should be able to make 240-250bhp naturally aspirated.

yes you are correct the turbo is run off the front bank only but the turbo is such a low blow I don't think itll be a problem tbh iv seen the germans turbo the 3.2 to 300bhp on std internals!! and yes the engine will make 240 without the turbo my aim is for more low down tourqe

[TheAngryDog]

I did a lot of looking into this several years ago.

The water jackets around number 6 cylinder are poor and not really suitable for turbo charging. There was a reason that the 3.0 in the Saab only made 200bhp.

Personally I'd not bother. If I was going to the trouble of this, I'd look at the 2.3 from the 9-5 Aero HOT. 230/250BHP straight from the bat and they can be tuned alot easier.

Or what about the 2.8 V6 turbo from the 9-3 / Vectra / Signum? Thats 230/250bhp as standard.

Edited by TheAngryDog on Friday 21st March 10:49