I’ve just started to restore an ‘86 international prime mover with a 692 tta Detroit it is 2 stroke has a blower 2 turbos and aftercooler all for about 375 horsepower.i think half of them would be lame but with straight pipes sound amazing

Sounds great.  How do the blower and turbos link together?
Phil R.

It’s a v6 a turbo on each bank through the aftercooler and into the blower. I wonder if the turbos were plumbed in series wether that would achieve more boost and bigger injectors ?

Not an easy one to answer.  With the turbos in series there would certainly be more boost, on paper, but the actual flow of air would be half, again on paper.  With only half the flow the turbos would be inclined to run faster. Because there will only be half what should be delivered you may not get much boost pressure at all.  With such a can of worms we should go fishing instead.
Phil R.

 I'd  guess the turbos would only boost to about 8PSI on a two stroke Detroit, but that would still give about a 50% power increase.
The blower on a Detroit is just that a blower, not a supercharger. It blows the new air in and new air pushes out the burnt exhaust through the exhaust valves in the head.

I watch this guy on Youtube, he's restoring a trawler with a Detroit in it. Here he's explaining how a Two Stroke Detroit works.

[video]Xa2x5vrie-o[/video] 

Modern engines!!  Too many variables.    Try this lot?.

When water pumps are connected in series the pressure increases. When in parallel the flow increases. Should be the same with air in turbos 

Great tales from the engine room Phil, Thanks.

Fire in the engine I liked the most, I can just imagine the fire bell going off at 2:53am and holding on to a bit of wood for an hour.

Damian K wrote:
Except that air is a compressible fluid and water an incompressible fluid.

Damian is partly right.  
                                             The engine has two turbos.  Each turbo produces half of the air required to run at full power from the atmosphere.  If we connect the turbos in series each turbo is moving the same half flow.  We have lost half of our available air.  The blower is capable of pumping the full amount of air the engine can use.  However with series connection only half of the required air will be available.  The blower will effectively starve for air and there will be little or no boost pressure.   The engine will perform as if it has  badly blocked air filters.
                                                However all is not lost, if you can find a couple of turbos with twice the capacity of the existing ones, and then assume you have the exhaust gas to drive them, it could be a whole new ball game. 
                                                Meanwhile,  our worms are getting fatter and there is a big old Cod just  waiting for us.
Phil R.