I have a Mazda MX5 it is geared kind of low and to autox it basically You take off in 1st and shift and don't shift back to 1st more than once. I took my 02 MINI to autox it is geared much taller than the mazda and has a narrow power band(4k to6.5k). seems to not generate much speed in 2nd at low speed.so how much 1 to 2 shifting is neccessary on an average autox course?

 

Depends on the course and your particular gearing.

2002 MC with 5 speed transmission- likely start in 1st and shift to second by 4000 rpm then keep in that gear for the remainder of the course.

First gear too low to keep it the whole way, 2nd gear useful more in the mid to higher rpms so don't loose any speed, brake less or not at all and steer through the course by modulating a little on the throttle.

Downshifting could be used on really tight turns but would best be done with heel toe method to match engine rpms with the downshift or it will unsettle the car and result in a slower time or a bit of lag.

If the course is very tight and slower then your second gear should work OK. If the course is very fast and wide open then rev up as high as you can go on 2nd.

Using a 2003 MCS with 6 speeds there are some courses so tight in my area that I can run it in first gear only (up to 47 mph). No shifting.

 

Can you really reach 47 mph in first? I calculated a 37.2 mph top speed in first using the gear ratios for the '05/'06 gearset, OEM size tire, and 6800rpm (stock rev limit?). What are the first gear and final drive ratios for first on the earlier cars? Do you have a raised rev limiter?

 

Good to know I'm doing it the right way
Only been to one autox... my 2nd will be the end of this month.

 

There is a BIG difference between the 02-04 ratios and the 05-06. I can believe 47mph in 1st on an early car and 60 something in 2nd after autocrossing both (I never watched the speedo though so I can not attest to actual MPH). The 05-06 MC has much nicer gearing for autocrosses in the DC area.

 

I have a scan gauge II to hook up in my car using the OBDII port and I reset it before each autocross run. I look for peak mph and rpms. Then I know if I am bouncing off of the rev limiter too much and hitting the top speed I want.

I have a 2003 MCS with six speed and yes I can easily reach 47 mph in first gear if I work it. If you back off short of rev limit usually it peaks at 44 to 45 mph. If I decide I want to use first only I have to really commit and not be afraid to use high rpms during the run. If I hear the engine reving and staying too high for more than one to two full seconds then I have to use 2nd gear. In that case I often will see that max speed for the event is about 49 mph or sometimes a bit more.

2005 or later MCS with 6 speeds have much better gearing and I recommend second gear for autocross. Really a no brainer since first gear is short and second comes easily.

If I use second and hit a slow section then a down shift to first might not be smooth and I'd be loosing time. Staying in first the whole run allows me to slow a little and hit the power band fast- it's really making the most out of the peak torque in the 3500-6000 rpm range mostly 4500 to 5800 rpms.