[corriedw]

If you do not find any, the cheaper option will be to shorten yours. An engineering works will do this by fitting a slightly larger bush on the small end side and the remachine the bush 1 mm excentric. The new bush must be as small as possible, not to weaken the conrod.

Conrods break when the engine is over-reved, high pressure from turbos and high compression is not a problem. If you want to rev higher, fit ARP bolts to the con rod and in extreme go to aftermarket rods.

 

[corriedw]

Then you can tell everybody that you boost 1.5bar. The fact that you make the same power that you would have made at 0.8bar with oe cr apparently does not matter for some people. It is all about how high they can boost.

This was posted before:
The pressure in the combustion chamber before spark is very important for power:
Low comp engine (1)15 + (2)15 = 30 x (3)7.5 = 225 lb/inch sq
High comp engine (1)15 + (2)7.5 = 22.5 x (3)10 = 225 lb/inch sq

(1)normal air pressure (2)boost (3)compression ratio
1 bar = 15 lb/ inch sq

Figures are illustrative only. but in both cases you can make the same theoretical power as the static pressures are the same.
With the higher CR you will need knock sensors as detonation will be a problem, but the smaller turbo in the low pressure setup will work much quicker, to overcome lag. If you really want to look for max power, a larger turbo will get more air in at the top of the range due to the stronger momentum of the larger turbos bigger stream of air. The air is also cooler with a larger turbo(more effective but at the top of the range) but will have some lag.

Boosted high compression engines is perfect if it is direct injection engines. But the illustration is not entirely true for the new Guilietta as the engine do not get all the high manifold pressure in the cylinder due to small intake valve openings.

Modern management systems has knock sensors to compensate for detonation on non direct injection engines(TS + Busso) IF combustion chamber temperatures are low enough(low boost). The Q4 had a management on par with this and Alfa/Lancia still prefered 8:1 compression and 1 bar boost.

The Nord do not fall in the top catagories and no after market management has knock detection yet. In my engine I would run an 8:1 or even an 7.5:1 compression ratio. 8:1 is 1mm down 7.5:1 is 2mm down on the piston in your engine. Yes you will have some lag and you will have to boost higher for the same power. But power is my reference not boost pressure and your engine will last longer for the same power.

 

[corriedw]

On my TS engine I shortend the conrod 2mm, 1 mm on the small end bush and 1 mm on the big end like TN explained. This do not weaken conrod too much in any spot, but it become a bit expensive.