Watkins Glen: Civic Vs Miata

Published: August 19, 2014

Here is a comparison between my best laps at Watkins Glen in Civic and in Miata.

Setup

Civic setup: front tires Toyo R888 225/45-15, rear tires Toyo RR 205/50-15.

Miata setup: Nitto NT-01 225/45-15 all around.

Graphs

Annotated speed plots:

For reference, clean speed plots are available here.

Speed and G plots:

Observations

Overall Grip Level

It looks like Miata has consistently more grip than Civic. The Civic lap happened last weekend, whereas the Miata lap dates a year ago. I have improved as a driver in the time passed, and thus I expect to be faster today in the same car than I was last year. While I had understeer issues in turn 7 in the Civic I felt that I was getting more out of the Civic in turns 1, bus stop and 10 at least, and seeing much lower minimum corner speeds in the Civic suggests to me that the car simply does not have Miata's grip.

The reason for this grip deficiency is not completely clear. One possibility is that R888 - especially by Sunday when I set the best lap in the Civic - were much slower than NT-01, even though NT-01 likely had a lot of heat cycles on them when the best Miata lap was set. Another possibility is Civic suspension geometry or setup, as only the inside half of the front tires really wore out suggesting that perhaps Civic was not able to utilize the entire tread width of its front tires.

Bus Stop

Both cars travel through the bus stop at similar speeds. The difference is Miata is staying off the first 3 curbs, using the final curb if necessary, whereas Civic is clobbering the entire first curb and uses some of the second and the third curbs. Civic does not use the final curb because cutting the third curb is sufficient to establish proper exit velocity vector.

Lateral G plots confirm this - Miata shows visibly more lateral Gs in the bus stop than the Civic.

Civic Gearing

With the smaller front tires, Civic actually runs out of revs in the top gear 1/3 into the back straight. From this data alone it's difficult to say whether running a 23" diameter tire would have been better overall, but given some time crunching numbers a conclusion can probably be made.

Civic Acceleration

Earlier at Lightning I concluded that Civic had a better power to weight ratio than Miata. This conclusion cannot be made from Watkins Glen data - Civic outaccelerates Miata below 80 mph (3rd gear in Civic) and above 105 mph (6th gear in Miata), but between 80 and 105 mph the cars appear tied. It is possible that power to weight ratios are in fact more similar than I thought, and acceleration differences have more to do with instantaneous gearing.

Civic Braking

I am pleased to see that Civic generally matches Miata under braking. Civic still has a soft brake pedal and Saturday and Sunday were spent on Wearever brake pads (Advance Auto Parts brand) rather than race brake pads. Still, Civic held its own under braking which was impressive.

Action Items

For the next event I ordered a set of 205/55-14 Nitto NT-01 to go on the Civic, as the R888 were completely worn out. I will experiment with different tires first to see if Civic can be made quicker in the turns.

Tagged: data analysis