The factory piping is rubber in the Gen Coupes and I see that Injen makes a piping kit that supposedly adds 9hp / 11lbs alone. So does switching from rubber pipes to metal really make that big of a difference?

 

Yes.

 

No, that's not what makes the difference. The difference is the new improved pathway and diameter. The difference in material could improve friction, but that would be very miniscule. Not 11hp worth. I wouldn't even count on 2hp.

It could affect throttle response to a small degree due to flexing, but again, very small gains.

 

The material is what makes the difference. Metal pipes don't expand. The expansion of the rubber hoses costs a few HP due to lag. The more piping there is, the bigger the improvement. The lower in the rev range you hit peak boost, the more power you'll make. The two first power mods we do to any GTR are intakes and hard pipes.

 

That's what I said...

 

The difference in material has nothing to due with improving friction and the main gains are not from diameter and routing since most hard pipe kits are the same diameter and follow the same routing. It's clear from you post that you're suggesting the lack of "flexing" provides a small increase in throttle response, but minimal HP gains. That's just incorrect. That's where almost all of the gains come from. Hard pipes on a GTR result in peak boost being made 1200rpm sooner. That's where the gains are. Yes, we're talking about a Gen, but the concept is the same.

 

Nope, this is not a GTR. And as such, they have different reasons as to their gains by replacing the piping. The factory Genesis piping has tighter radius bends and multiple connections with different diameters coming together. Replacing all the tight radii, connections, and "stepping" of the pipes, with a single smooth piece is where THIS particular car gets the gains.



Even still, 9hp is being optimistic.