Also changed the diff yesterday from the 3.92:1 to a 3:36:1 I got from a fellow locost builder. This should make the car much more usable with a theoretical top speed close to 140 MPH and improved intermediate gear speeds. Cruising should be more comfortable with 70 MPH being around 2800 RPM in top gear and it should do over 80 MPH in 3rd.
Here are the in-gear theoretical speeds at 5500 engine RPM before and after diff change:
|1st||3.321||29.3 MPH||34.2 MPH|
|2nd||2.087||46.5 MPH||54.3 MPH|
|3rd||1.396||69.6 MPH||81.2 MPH|
|4th||1.000||97.2 MPH||113.4 MPH|
|5th||0.833||116.7 MPH||136.2 MPH|
I've given the speeds at 5500 RPM but even with the standard hydraulic valve lifters, it is possible to run to 5800 RPM which pushes theoretical top speed beyond 140 MPH. However, the drag coefficient of the Lotus 7 type car was never great so I'm not sure how fast it will actually go. I'm pretty confident it will go beyond 120 MPH but I wouldn't like to say any more than that...