03-07-02, 01:23 PM
If you did have a Saab V6 and you wanted to twin turbo it, could you put a smaller turbo like a mitsu which spools up faster on one side and a T4 on the other side for when the RPMs get higher? Or do they have to be the same turbo size?
I'm pretty sure there's been staged turbo charging on production cars, can't remember what though. Sounds like a very hefty job though.
03-07-02, 05:02 PM
The good thing about it though is once the first smaller one has kicked in it will take almost no time for the huge turbo to kick in and then yer off.
Yes some of the Subarus use that system (e.g. the Legacy RSK B4) - a smaller turbo to get it going and then a larger one cuts in. Sounds good in theory, although there are those who say "twin turbos twin trouble". Lord knows how difficult it would be to add to a Saab V6...
03-07-02, 05:43 PM
A twin turbo mod on a 9000 V6 does appeal to me, I've heard that the V6 has a pretty crowded engine bay. So finding somewhere to fit the buggers would be a problem.
I always thought that twin-turbos on V6's were a symmetrical setup, i.e. a turbo on each manifold off the Vee. Combining a smaller and larger turbo in one system would be Bi-turbo(?). Am I a wrong?
03-07-02, 05:57 PM
Twin turbo is just one turbo coming off each exhaust manifold and in a V6 there are two of them. You could in theory twin turbo a 4 cyl but it wouldn't be worth it because it would take forever and a day for the backpressure to spool up the turbos if you only have two of the piston's exhaust going into them.
04-07-02, 04:09 AM
Small twin turbos in a V6 is the way to go IMO. Sequential turbocharging has been used of course, but it's just so much of a hassle. And when people tune their twin turbo production cars, almost without exception, they replace the sequential configuration with a single turbo or two equally sized, full-time turbos. This is the case with many 300 ZXs ans other cars.
It's much simpler to get the characteristics you like with a basic, simple configuration.
And, if you use twin turbos in a 3-litre V6, you can think it as two turbos each sized for a 1.5 litre engine. This means you can use small units, and spool-up will be quick enough.
There's one pretty cool Saab 96 in Finland, BTW; Ford V6 and twin Garrett T03 turbos... :smile: Should be quick enough.
04-07-02, 05:56 PM
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>Lord knows how difficult it would be to add to a Saab V6...</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
Yep, it would probably require some body shell remodelling and removing any non-essential parts such as screen wash bottles and AC compressors.
To have 3 cylinders running into a large and 3 cylinders running into a small turbo would be a problem.
Now imagine you are drivin along and at 2200 RPM your small turbo comes on boost, without blocking off your second turbo outlet all your compressed air will be blown back in the reverse direction through the second turbo. (this is assuming that your second turbo is large enough to not be spinning very hard- or at all at these RPM.
So your not gettin any boost.
Assuming the above scenario is not in place (by blocking larger turbo's outlet before it makes boost or by appropriate sizing- very close)
Now as you hit 4000rpm your second turbo comes on boost as your engine starts passing massive amounts of air the smaller turbo on one bank of cylinders starts to produce a lot of restriction and back pressure to those 3 cylinders.
As exhaust is not being cleared properly your 3 cylinder will receive less fuel and air than the other 3. causing a inbalance in power production across cylinders and most likely causeing one bank to run richer/leaner than the other...
Those well read in motoring literature will realise that the sequential systems used in cars such Supra's, RX7's or Subaru B4's collect all exhaust gas together and then distribute it to the turbo's. This allows them to shut a flap and stop one turbo from receiving exhaust until the other has boosted up. then the flap is opened and both receive exhaust and make boost.
To overcome the air being pushed back through the unused turbo's compressor by the other, a oneway valve style system is employed...
THese systems work well in theory and offer a nice spread of torque but are the source of many reliability problems in these cars.
Sorry for the long post, but i hope i have delivered my opinion that the suggested style setup is not a wise idea....