Trying to get a little better grasp on understanding it based on some dyno sheets I've seen compared to crank HP claims.

To set the stage say I dyno my car completely stock and come up with about 240 RWHP. Stock engine at the crank puts out 287 so I can assume that there is a drivetrain loss of about 47 HP, give or take a few because of the dyno itself. No matter what mods I do to the motor to increase power this number should always be the same unless I start modding drivetrain components, correct?

Again, say I go with a F/I set-up and, hypothetically, the motor turns out 450HP (claimed) @ the crank yet my dyno reads 375 RWHP. Would it be safe to assume that I'm still lossing that 47HP due to drivetrain loss but the additional 28HP loss could be due to the change in the tune of the motor?

I understand the only way to really know is to do an engine dyno run and a chassis dyno run then compare the two. For all intents and purposes though does the above seem reasonable??

 

Drivetrain loss is a "percentage" of crank hp.

With a crank hp of ~287 and a loss of ~47 that equates to ~16% DT loss.

With a crank hp of 450 you would loose ~72hp (16%) to drivetrain loss and measure about ~378rwhp.

Also note the most efficient gear on a 6MT is 5th (1:1 ratio).