Quote:
Originally Posted by RockBit
Thanks for the comments. My calculations show at 75 mph, I should be at:
2,197 rpm for 3.54
2,054 rpm for 3.31
Most of the highways in Texas have 75 mph limits, which means everyone drives at about 80. I wanted to be able to drive on the highway without ear plugs.
I told Brent the engine will be mostly used below 4,500 (city cruising) so he is aiming it toward low and mid range torque. I'm confident he will hit the target.
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I think I would give this some more thought. Basically, until Interstate speed you are going to essentially have a 4-speed transmission IMO. I think the 3.31 rear is OK with the 2.87 first gear but there will be a big drop from 4th to 5th which is nice when cruising along on an interstate, but it's not what you normally want in a high performance car where you want a useable and fairly equal spread of gear ratios. I have a similar situation in my 3.31 2012 GT Mustang with 6th gear. The drop between 5th and 6th is so large that I can barely use it around town - I have to be going at least 45 mph on level ground, 50 to 55 if any hills at all. Depending on the characteristics of your engine you may have to be moving a lot faster than that. It's not so much that huge torque and a light car can't be propelled along by a .64 5th gear, but as Patrick said, depending on the cam, the engine may not feel too happy about it. But it's your car and you know how you want to drive it.
Sounds like a nice car. Keep us posted on it's progress.
I guess I should add that at 75 mph the need for ear plugs is probably more driven by wind noise than exhaust noise.