I must admit I have never understood manifold pressure. I have been working on that. The lack of power at lower RPM is understood.

RPM X torque = HP. So, the engine has poor torque due to short stroke. There goes half of your multiplier. Tuning needs to be a bit closer to ideal. The best way to remove HP is a poor exhaust system.

Look at the care in the designs of dirt bike exhaust systems. A typical turbo exhaust manifold is a poor design for a normally aspirated engine.

And until the boost is up to overcome that poor design and add the recovered power to the intake, you just have a NA engine with a bad exhaust design. 

So the first engine saw 44" HG when it failed. That would be 21.5 pounds of boost. Over 20 pounds you need to be right on the tune.

Well rich of peak EGT to fuel cool and lower charge temperature.

Timing 2 degrees below best power. Good size intercooler and a quick waste gate. That was on the way to being a drag racing engine before adding the known problems.

When the boost is low or there is none, then you can use more ignition advance.  Once you can limit boost to say 4 to 6 pounds or 8" to 16"HG with a waste gate you can be close to 18 degrees. Same as a NA engine. When the boost is up to maximum then you need to retard a bit. On long closed throttle runs you can be up to 35 degrees.

This because you have few pounds of air, and nearly no fuel flow. So, very low compression. All this takes a long time to burn the idle mix.

The RX-8s do this.

How is this? One pound of boost is the same as 2.04" HG. Or, 14.7 pounds at sea level times 2.04 =29.98" HG. At any throttle setting,

local barometer showing on the manifold pressure gage suggests a well designed intake system and a free flowing air filter. The Manifold pressure gage is measuring vacuum in the intake system. The gage is connected between the butterfly and the engine or turbo inlet.

The boost gage measures pressures above local barometric in either pounds of boost or inches of Mercury or both and is connected between the turbo and the engine. It is measuring pressure in the inlet runner. 

Is that correct?

Add timing marks to your starter ring gear. Divide the number of teeth by 360 to get degrees per tooth. Clean and paint a green tooth at TDC.

Turn the engine backwards and paint a tooth or valley between teeth another color for 15 degrees. Paint a red tooth at 20 degrees, and so-on. Write the code on the engine beside the pointer you have constructed. OK for tractor aircraft. Not so much fun for pushers where the prop is pulling at your loose clothing.

Lynn E. Hanover

If your ignition timing measurement was accurate at 3000 rpm and 16" mp,  it's way too retarded.  What did you set the static timing to?   Remember that that has nothing to do with actual ignition timing.  It's just a reference point for the computer.

 

Tracy