Miata Mailing List: August 1994, Message #88



     


   From: Miq Millman 
Subject: Re: When to shift.....
   Date: Thu, 4 Aug 1994 04:42:59 -0400

Alice T. Liu says:
>         
> I take highway 9 every morning to work, from Felton to Santa Cruz.
> It *is* fun.  It's probably one of the tamer streches of the highway.
> But I'm a newbie - I had only about 5 hours worth of experience 
> driving stick before I got my Miata!  I'm sure I am not yet taking 
> full advantage of the road.  My shifting is much smoother now, but 
> I'm still unsure about when I should be down shifting, so if anyone 
> has any tips, send them my way.  For smooth shifting, for instance, 
> from 4th to 3rd, it seems I should be going 30 mph.  Any higher than 
> that and the rev sound gets higher and the car lurches a little.  


First off let me insert a caveat:  my miata is modified, puts out ~155 hp on
a dyno, the way I drive it gets about 22 mpg on a good tank, 14 at the track.
You may not want to drive your miata the way I drive mine.....but it sure is
a lot more fun....

My commute is about 23 miles of windy backroads with some pretty steep hills
as well.  (Now don't forward this to the OHP) speeds vary between 35 and 85
mph.  In my modified miata the powerband starts at about 4600 rpm; peak is at
5950 rpm.

shift to 2nd at about 30 mph  (rev limiter cuts in at 35 mph)
shift to 3rd at about 55 mph  (rev limiter cuts in at 58 mph)
shift to 4th at about 77 mph  (rev limiter cuts in at 83 mph)
shift to 5th when not accelerating. (or at 105, rev limiter cuts in at 110
mph but I've only done this on the race track....honest (btw, 5th maxes out
at 135 at rev limiter I hit that last weekend))

When I'm driving up a steep hill, or entering a series of turns that I want
power in, I keep the engine speeds up--about 5800 to 6300 rpms at a minimum.

There is a 4 mile stretch of road with lots of 25 and 30 mph markers on the
turns, I usually take the entire portion at between 60 and 65; in third gear.

There is a 2 mile stretch that is relatively straight with small rolling
hills, I usually take this section between 70 and 85 (depending on traffic);
in 4th or 5th, gotta get some better mileage sometimes.

On the highways I usually shift into 5th when I have merged with traffic,
depending on time of day and freeway this is anywhere from 55 to 75 mph.

So, as long as you match engine speeds and keep it out of the red, you should
be fine.  When power is concerned, more rpm's is better.

Gear	Ratio	    Good mph to down shift to at the new (and old) rpms
1st	3.14	    22 mph - ~4300 rpm (was at 2750 rpm)
2nd	1.89	    33 mph - ~4300 rpm (was at 2800 rpm)
3rd	1.33	    50 mph - ~4300 rpm (was at 3300 rpm)
4th	1.00	    75 mph - ~4900 rpm (was 4000, need the extra power at 
					this speed)
5th	0.81	    not applicable

So is this all clear as mud?

-- 
Miq Millman   mmillman@ptdcs2.intel.com	  503 642 6139   (Aloha site)
AL4-55  Intel, 5200 NE Elam Young Parkway, Hillsboro, OR 97124-6497
See also miq@teleport.com