when and where will you water test

That would be my preference. Parallel twins with an actuator exhaust gate. We’ve had some great results in a boat with that setup.

Shame you couldn't have done a parallel setup also it would have been great to see the difference in the torque curve on the dyno between the two.

Do you know if industrial have ever done any back to back test between the two setups.

We reduced the time to plane off on a 70’ sporty from 30ish seconds to around 5. Merritt complained that people were flying off the back of the flybridge and asked us to dial it down a bit.

An early contender for post of the year. :drink:

We are doing compound turbos instead of doing twin turbos that are in parallel with a bypass valve because we are wanting higher boost pressure along with the quicker spool up time.

Most turbos are designed around having an efficiency range in the 30-40 psi range. If we did parallel twins we could not really run a higher boost, just the ability to spool quicker and have lower exhaust temp at high rpm. But we are wanting a higher hp and the most fuel efficiency we can get. By having the turbos compounded we can run each turbo in its designed boost range and end up with 70-80 lbs of boost to be able to make more total hp and the same hp with less fuel.

They have tried two or three small turbos and two or three big turbos already, trying to get the best spool up and lowest egt's. Next week there going to try a lot smaller high pressure turbo and a bigger atmosphere charger. There are millions of options of wheel size, ratio combinations, and that goes up by exponent using a compound turbo so they are making drastic changes to narrow down the range they need to look in. And we are not doing the "hey this is what everyone does" mentality. We are trying things that may not work but would not know till we try. Right now they are in the 81 1.15 small charger and 93 1.35 large charger range. Making around 65 PSI at 3800 rpm at 1200 hp and 1200 egt. I want to run a smaller little charger to have the boost gauge move with the throttle. Something like a 63-67 mm It will make the boat more usable when throttling in the rough water.

Here is video of it running on the dyno, the intake tube will be different when its in the boat. The dyno uses a different bellhousing and starter location so the intercooler has to be turned around. In the boat the intake tube will run around the back side of the engine.

If you are looking for boost in that range I would agree compound is the way to go as each charger will give you an efficient compression ratio of around 2-1.
The smaller charger should help low down torque especially if you decide to go with the overdrive gearbox.

How did you get on with the drive ratio, boat seemed to be performing well enough with the 1-1 setup are you still thinking of overdrive?
I would imagine with 1200hp at 3800 rpm and 1-1 ratio you are going to run out of prop options unless you do so, are custom props an option with huge pitch? only down side a big pitch prop isn't as efficient as a smaller prop running higher rpms and the larger pitch prop will certainly need vent tubes to get her on plane.

I'm a little surprised that at 3800rpm your egt are that high with that large of turbo's(respectively) What's the temp drop across the water to air intercooler? Turbo's seem close to what I would suggest, and your nuts on, on keeping a smaller charger for quick spool then gating around it for high rpm and boost.

funny I thought 1200 was on the low side considering that is WOT. making that much HP. I'm no expert just my initial impression.