Ahvenisto lap comparison – 3 times NA Mazda MX-5

THE TRACK

I’ve spent most of my track time in Ahvenisto Racing Circuit. It is by far the most demanding race circuit in Finland. It’s technical, it’s beautiful and it’s legendary. And perhaps it’s world famous already since Captain Slow visited it with Mika Häkkinen – a Formula1 double world champion. http://www.youtube.com/watch?v=2bmqdnx5R1U

Ahvenisto Racing Circuit is built in late 1960’s and that makes it a bit different. It’s like Norschleife’s little brother. Most of the time it’s either uphill or downhill and there are no real runoff areas. Difference between the lowest and highest point is 30 meters (100 feet). It’s pretty much for a track that is roughly 3 km long. No picture can communicate track’s true profile. Incar videos give a hint but this track is something one must experience personally.

Enough with the praise. Here is some data extracted from this video  http://www.youtube.com/watch?v=Ft3Cx6fHrhI&feature=youtu.be. Here is some basic steering, throttle and brake input data to tell its own story about track’s profile.

Lap time (dry weather): 1´38 s

Steering wheel straight forward: 22% of the time

Wide open throttle: 43%

Foot on brake: 17%

Throttle partially open: 40%

Longest time throttle is continuously 100% open (including gear changes): 17 s

THREE CARS, THREE LAPS

Next follows a brief analysis of three laps done by three different MX-5s. They are in many ways similar but at the same time totally different. I will call them Silver, Red and Green. They all are from early -90’s with B6ZE engine.

Red’s specs:

- About 120 crank hp, completely stock engine with silenced decat pipe, 7200 rpm rev limiter

- 4.1 final drive with torsen type-2 differential

- BC Racing BR coilover suspension, Energy Suspension poly urethane bushing, stock stabilizers

- Track spec wheel alignment

- Yokohama Advan AD08 tyres, 205/50/15

- No roll cage or roll bar, P5 frame rails
- Lap time 1:39.5

Silver’s specs:

- About 130 crank hp with intake and exhaust mods, 7200 rpm rev limiter

- 4.3 final drive with Kaaz 1.5way L.S.D

- Tein SuperStreet coilover suspension, full set of poly urethane bushing, stiffer front stabilizer (22 mm diam.)

- Track spec wheel alignment

- Toyo Proxes R888 tyres, 195/50/15

- Full roll cage, interior strip down to compensate cage’s extra weight, plus no air-con and power steering.
- Lap time 1:38.5

Green’s specs:

- About 160 crank hp, 8300 rpm rev limiter.

- 4.3 final drive with Kaaz 1.5way L.S.D

- Koni Sportskit suspension, stock bushing, H&R stabilizers front and rear

- Track spec wheel alignment

- Yokohama Advan AD08 tyres, 205/50/15

- 6 point roll bar
- Lap time 1:37.5

Colors painted on the track illustrate gears: light green is 2^nd, yellow is 3^rd and orange is 4^th. Numbers in the boxes are “gear”/”revs” and speed below (in kph).

Okay, what does this tell then? First take a look at the gear changes. Red changes gear 6 times per lap because of the wider total gear ratio (4.1:1 differential and large tyres). Silver must change gear 10 times per lap (shorter overall gear ratio). Compared to Silver, Green’s total gear ratio is similar but Green benefits from higher rev limiter set to 8300 rpm - hence 6 changes per lap for Green. Silver’s extra two up and down changes both come in bad places. The first is before turn 3 where all the concentration should be aimed on upcoming left turn heading uphill. The second is between 8 and 9, on an uphill, not the best place to shift up either.

Next take a look at the table with cornering speeds. It’s interesting to notice that all three have almost identical cornering speeds in 5 turns out of 11. Track is very technical from turn 6 to 10 and the trick is to keep up the momentum. It’s basically one big complex of turns where clean driving and good handling is rewarded.  In paper Silver should have highest apex speeds as it is equipped with a set of R888’s.

After turn 10 it’s flat out for a while. Keep the throttle floored through turn 11 and get your top speed measured before going on brake and diving into turn 1! This half of the track from turn 10 to turn 6 holds all the straights - or not so curvy parts. High powered cars gain some ground here but are usually caught between turns 3 and 5 if drivers aren’t familiar with the track. Turn 11’s apex speeds show Silver’s more favorable gear ratio and power over Red’s.

Technicality of the track, the effect of gearing and apex speeds were three most important things I wanted to highlight here. Power isn’t everything in Ahvenisto and skillful driving is a key to success. Please continue checking the graphs by yourself – there is plenty of more to be found!