I previously had a thread about K24 gearing, and people thought I was an idiot for wanting to be able to drive at highway speeds without revving the engine to 4k rpm. I've got a B18C5 in one car, and a stock D15Z1 in the other car. Everyone I've talked to has told me to just keep the B18 instead of swapping to a K24, since I really only want to see around 400 hp max. The advice has been to swap in an LS 5th gear and final drive to achieve good highway gearing in my ITR motor and trans. I used one of the recommended gear calculator websites to see what this would look like, and even the LS 5th and final still puts 5th gear at 80 mph at 3400 RPM versus my D15 in 5th gear at 80 mph at 2600 RPM. That's a big difference, and I don't want to drive for days on end at almost 3500 RPM. Is it possible to gear my B18 to get better highway gearing than this? If not, would I have better luck in gearing options by switching to a K24 motor? Somebody suggested the '06 - '11 Si transmission for it's taller 6th gear, but the final drive is shorter, resulting in only a marginal difference compared to my current setup with the B18 ITR tranny. I'm hesitant to start building any engine until I know that I can get the right gearing for it, and I know that what I've got in the car now is definitely not going to work for me.

edit: here is a link to the gear calculator site with the info I put in comparing the ITR transmission with LS 5th and final to my stock VX. You can see that even with those mods, the B18 5th gear falls in between my VX's 3rd and 4th gears, it's not even remotely close to what I'm aiming for.

http://www.teammfactory.com/calculat...400/5400/1/0/2

 

You can't use an LS FD in an ITR. Without lean burn, lower RPM is not better for fuel economy. Higher RPM = less throttle needed to maintain speed = less fuel consumed.

The VX is a lean burn engine designed to run optimally at a low RPM. Comparing it to anything that isn't lean burn is pointless.