200SX 5 spd, 1983
Posted 16 April 2018 - 08:59 AM
Posted 16 April 2018 - 06:48 PM
You should have an 11.8% over drive so if at 4,000 in 4th... 5th would drop 472 RPM to 3,528
Top speed in all vehicles is limited primarily by wind resistance. Keep in mind that as speed increases wind resistance increases 4 times for every doubling of speed. Four times not double. If it takes 30 hp to drive along at 50 MPH it will take 120 hp to drive at 100 MPH. To make power a gasoline engine needs to rev up. It will make more power at 4000 than it will at 3,500. If you reduce the engine speed too much it will go faster in 4th revved up than in 5th at lower revs. This is called being power limited. Over drives are not intended to be used to go faster, only reduce engine revs at cruising speeds. Nissan engineers probably did the math and selected an over drive that will work fairly well with your 620.
If you can keep up with traffic I would just leave it as is. It's only noise, and an L20B red line is 6,500 RPM so you won't hurt it. You might go to a lot of trouble to go slower. Spend some money on sound deadner.
- cruznude likes this