FM2 Ford Focus SVT, Mazda(Miata) Roadster and Toyota MR-S[D400]

[Choccy]

Ooh...I'll have to give the miata a look.  My D-class miata is posted in my garage, but it's more of a mongoose.  I was able to shave a few seconds with an SM, though (PI393, I think).

I made some minor adjustments to the Mazda (Miata) Roadster tune to enhance stability.

Rear camber, front and rear ARB and rebound damping fine tuned to keep the rear in check(until you want to step it out), keep lateral weight transfer balanced front to rear and make turn entry, exit and transitions more precise.

I remember reading a recent post on FM.net by one of those IFRC(sp?) members. Basically, he claimed you couldn't negotiate turns at speed in FM2 without aerodynamic aids.

Fallacy.

I took the revised Miata tune out for two laps of Free Run last night. Best lap time was 08:56.855, placing 1705th. The always full tank of gas made itself felt. But I think there's still a faster time to be extracted.

[Choccy]

It may or may not help worth a darn, but here's a summary of my driving techniques. Nothing groundbreaking:

1- Brake in a straight line before turn entry.

2- Select the appropriate gear before the turn in point.

3- Do not "last minute" the turn. Be deliberate to exploit early and late apex points.

4- Do not change gear mid-turn( at least wait until you pass the apex ).

5- Minimize steering inputs and modulate the throttle to rotate the car through the turn. You scrub speed and bog the engine if you exceed the slip angles in low power cars.

6- Short shift, i.e., 4th to 2nd without the tranny stopping on 3rd while the clutch is still disengaged, to exploit engine braking.

7- Use "heel and toe" techniques where possible. I avoid using brakes in isolation. Maintain throttle and at the same time, apply brake to bleed off speed while sustaining engine rpm. Combined with #6 above, you can enter and exit turns with minimal loss of speed.

I'm curious how much faster these cars can navigate The Ring if we ignore the PI and swap the stock tires for sport or slicks leaving the rest of the tune the same. Worth a try later.

[fndrbndr]

I was getting some uneven tire temps, about 12 degrees hotter on the inside, so I got rid of a little camber.  I'm thinking of further reducing front camber and using a little caster to even things out.  Also, I upped the diff to my "standard" 35/25, which made the car more stable, but increased the turning radius more than I had hoped.  Also, I did switch to a race diff, and might go to race tranny as well.  BTW, real-world ratios work like a dream in Forza, if you're worried about tuning the race tranny.  The Miata ratios are 3.136, 1.888, 1.330, 1, 0.814, with a final drive of 3.65. I'm getting these from Gearcalc.  SCCA's spec miata rulebook gives the same ratios, but rounded to the second decimal, with a final drive of 4.1 or 4.3  I'd recommend 4.3 with the amount of power this build puts down, which is actually quite a bit for a naturally aspirated miata. 

You might want to check out my Spec Miata build (link below).  It's sport tires, stock power, and either sport weight, all based on SCCA rulebook, landing at 393.  I'll shoot you a FR next time I'm on (wed-fri is pretty hectic for me), and thenif you want, I can send you one of these.  I have a few extra.  SM runs very stiff front springs by default, in the 700 lb range IIRC, but the car has a very short wheelbase, so it's not the understeering pig you might think.
http://forza-tuning.net/index.php/topic,890.0.html

[Choccy]

I was getting some uneven tire temps, about 12 degrees hotter on the inside, so I got rid of a little camber.  I'm thinking of further reducing front camber and using a little caster to even things out.  Also, I upped the diff to my "standard" 35/25, which made the car more stable, but increased the turning radius more than I had hoped.  Also, I did switch to a race diff, and might go to race tranny as well.  BTW, real-world ratios work like a dream in Forza, if you're worried about tuning the race tranny.  The Miata ratios are 3.136, 1.888, 1.330, 1, 0.814, with a final drive of 3.65. I'm getting these from Gearcalc.  SCCA's spec miata rulebook gives the same ratios, but rounded to the second decimal, with a final drive of 4.1 or 4.3  I'd recommend 4.3 with the amount of power this build puts down, which is actually quite a bit for a naturally aspirated miata. 

You might want to check out my Spec Miata build (link below).  It's sport tires, stock power, and either sport weight, all based on SCCA rulebook, landing at 393.  I'll shoot you a FR next time I'm on (wed-fri is pretty hectic for me), and thenif you want, I can send you one of these.  I have a few extra.  SM runs very stiff front springs by default, in the 700 lb range IIRC, but the car has a very short wheelbase, so it's not the understeering pig you might think.
http://forza-tuning.net/index.php/topic,890.0.html

Thanks for this fndrbndr! I'll definitely check out the Spec Miata setup.

The irony of your last comments take me back to last year with my spring rate theory and calculations on FM.net.

Personally, I prefer stiffer springs(with adjustments to avoid excess rigidity) that match the car's weight distribution. At certain venues, and as it's commonplace in actual motorsport, I found handling benefitted from softening the spring rate from calculated values for venues with more uneven surfaces and using additional stiffness for near featureless tracks. I consider spring rate largely dependent on the car's weight and the application. How stable do you need the car to be at attack pace. Do you have room to let the car run out or do you need it to be tightly controlled, like The Ring.

The Miata setup I submitted here has softer springs than I'm typically comfortable with. The car has a slight "float" feeling that can make me second-guess the car and that's no good when you're moving at ten-tenths. But the 08:56.nnn time I extracted was with the setup as listed right now.

All told, I'd take an additional 50 to 100 lbs-ft increased spring rate front and rear to lock the car down.

I appreciate the detailed feedback and the information regarding transmisison ratios. I remember reading one FM.net member's thread on calculating ratios with earnest. That fellow put a lot of effort into his analysis.

After I'm done with the D-class MR2, I'll bump up to B-class and perhaps revisit the Miata to see how much or how little the tune needs to change to accomodate the higher speeds.