A tuning experience

I’ve been practicing with turning cars for a little while but haven’t taken the time to really know what I’m doing. I have read several posts in here and finally decided to get serious about it. I plan to chronicle my experiences here and want to get feedback as I do it.

I started with the following.
Car: 1994 Mazda Miata no upgrades
Course: Indy Oval
No assists on except braking line

The first thing I decided to adjust was tire pressure. This is the only thing I can adjust with no upgrades. I looked at the tire temperature and the PSI. After 3 laps the temperature and pressure stabilized. I adjusted tire pressure to 28.5 and found the hot PSI was at 32.9. I then tried 29 PSI and found hot PSI was 33.4. These two settings gave very similar lap times with 29 PSI have lap times about 0.03 faster. I then tried tire pressures of 28 and 29.5 PSI. Both were slower than the other settings by about 0.1 seconds. This makes sense because the default 30 PSI was 0.2 seconds slower.

So, I gained about 0.2 seconds per lap with only tire pressure adjustments.

I learned one other thing. Since I have simulated damage, tire wear and fuel consumption on, the tires are wearing. Lap times became slower the more laps I did. The best laps were the 2nd to 5th. I also noticed that as the tires wore, the rear end began to slide out slightly passed the apex of the corners. I bought the adjustable suspension upgrade so I could make adjustments to the tire alignment and the springs. I decreased the front rebound and increased the rear bump. This helped with the over steer but created a new problem. The cars bounces a little. Going down the straights the car goes up and down slightly. It is annoying to look at but the car is faster. I’d rather find another solution.

I also made one small camber adjustment. I adjusted the rear camber slightly. I first increased the negative camber (more negative). The car ran slower. I then changed the camber to -0.4. The lap times improved slightly. I also lowered the ride height to the minimum. This reduced lap times by over 0.4 seconds.

I tried adding the street compound tires. Times improved but the slight over steer problem remained. The car was going around the corner faster but the rear end is still sliding out after the apex. I have gone back to the stock tires. I will probably change the tires later.

Here are my current ideas.
Change the wheels and put slightly wider tires on the rear.
Buy a rear anti roll bar and try adjusting it. Can you buy just one anti roll bar and adjust it? Does this even make sense?
Run the rear tire pressure at 29 PSI and the front tire pressure to 28.5.
Adjust the springs to balance the weight. I’m not sure what adjustments to make here. What is increased and what is decreased to move more weight to the rear?

Any other suggestions will be appreciated.

1 Like

as is it sounds like you need to continue to adjust the dampers as they control corner exit much more than the other things. Yes you can buy one roll bar, front or rear, but to be honest its almost not worth it to buy one and not the other unless there is a glaring problem with only one part of the car and everything else is perfect or pi restricts you from affording the second one, as is they are nearly free.

I did some more tuning last night. I only looked at tire pressure and tire compound. I test pressures of 30, 29, 28.5, and 28 PSI for both stock and street compound tires. Here are the results.

PSI Stock Street
30 1:15.924 1:15.602
29 1:15.656 1:15.639
28.5 1:15.687 1:15.333
28 1:15.658 1:15.343

The street compound at 29 PSI was the worse. This seems odd but I can easily explain it. The over steer problem I mention earlier is bad for this configuration. When the PSI is reduced to 28, the over steer problem disappears. I think this is occurring because the car is travelling slower.

Adding the street compound tires did improve lap times by 0.3 seconds. It added 7 to the performance index (PI). I’m unsure how good the improvement is for the PI cost. I’ll be watching that too.

More tuning and more unexpected results and some expected results.

After reading some more tuning information. I decided to try adding an antilock differential and kept the tire pressure at 28.5 PSI. I used the default setting of 75% acceleration and 75% deceleration (75/75). The results was horrible. The car was skidding in all the turns. The lap time was 1:15.779. I removed the antilock differential and looked at the default settings of the stock differential. They appear to be about 40/10. I reinstalled the antilock differential and set it to 40/10. The lap time was reduced to 1.15.644. The car drove a little nicer than it did without the antilock differential. I then changed the settings to 30/10 and got a time of 1.15.645. No change. I then changed the settings to 50/10. The car drove even nicer. The lap time was 1:15.534. I then changed the setting to 60/10. The car didn’t drive as well and the lap went up to 1:15.769. I then decided to try 45/10. The car felt similar to the 50/10 setting but the lap down went down to 1:15.484. I then lowered the tire pressure to 28 PSI. Then increased the lap time to 1:15.642 which is very close to the time for this tire pressure without the antilock differential. In summary.

Setting Time
30/10 1:15.645
40/10 1:15.644
45/10 1:15.484
50/10 1:15.534
75/75 1:15.779

This experience with the differential surprised me. I thought it was locking too quickly after the apex and that was causing the over steer in the second half of the turn. I am locking it earlier and the over steer has disappeared. Can someone explain that?

I added the adjustable suspension and have started looking at changes I can make because of that. I started by lowering the ride height. Here are the results for far.

Height Time
5.2 1:15.492
5.1 1:15.382
5.0 1:15.302

The default settings for the suspension didn’t change the lap times much. Once I started lowering the car, times improved. I expected that.

I am not sure what I am about to say is what your talking about but I have found that lowering the diff decell in relation to the acell makes the car more oversteery/ less understeery into a corner AND more understeery/less oversteery out of the corner.

I call it my Penut butter and toast tuning method.

I would of thought making the rear PSI lower than the front on a rear wheel drive car would make sense, like 28.5 front and 28 rear, the rear tyres are obviously the ones under stress as its a rear wheel drive car and will heat up faster, when the tires are warmed check your telemetry and they should be around the 32 -33 mark when running the car, this is the best PSI for grip apparently. Your anti roll bars transfer the cars weight through the car, on a rear wheel drive car you need to tighten the back end up, seen as the car is only light I would probably make it around 15 and move the front end down to around 9 if the care slides then adjust these slightly, I don’t know what other upgrades you have but the suspension is usually reduced by about 25%,ie if it reads 500lb reduce it to 375

Also ride hide needs to be reduced to a minimum as this gives better downforce, therefor the car sticks to the road better, I think it can effect top end speeds but you will never get there in the Miata :smiley:

If I can interject real quick,

While hunkering a car down low does in fact improve aero in reality, the real reason you want to lower a car is to lower its center of mass. That is where your real benefits are… A lower center of mass makes the car more stable in corners. (Think about rollover tests. Top heavy trucks and SUVs are easier to tip over because more of their weight is up high, while smaller cars that ride lower to the ground simply CANT roll over unless they hit something.)

Tip over a can a soup.
Now go try to tip over a can of tuna.

As for the aero benefits. That a has a lot more to do with closing the open space between the car and the ground to prevent air pressure building under the car. This is why high performance GT racecars all have body kits that extend the body straight down to the ground. Lowering a car can make that easier, but the car being lower really has no effect on aero at all.

Same with NASCAR and V8 supercars.

I appreciate everybody’s input. I will try a couple of things out based on the comments.

It was a long weekend of tuning and I found out a lot. I went through every adjustment I could make because of the suspension upgrade. There are a lot. Several of them interact with each other too.

I lowered the ride height to the minimum. The lap times got slower. It took me a little time to figure this out. I reset the ride height to 5.0 and times improved. I started listening to the car. (Turn of the music, it is a big help.) The car was bottoming out coming out of turn 1. There appears to be a bump there. Later I tried softening the springs. The car rides much smoother and is easier to turn but it started bottoming out again coming out of turn 1. I increased the ride height to 5.1. With the softer springs and increased ride height, I get slightly slower (~0.05 seconds) lap times, but a much smoother ride.

Caster and front camber are very related. This doesn’t surprise me but trying to adjust the two can be tricky. Toe is an another interesting adjustment. I found with slight toe in on the front the car goes around the corners much easier but lap times got slower. The car appears to be going slower on the straights.

Springs and suspension are tricky adjustments. Every time I adjust one it appears I have to adjust something else to compensate for it. I have a lot to figure out here.

I added the sport transmission next. I changed the final gear ratio. This reduced lap times a lot. I got lap times under 1:14. To do this I had to readjust camber and caster. Everything is tied together.

I then changed the wheels and tires. I put wheels of the same weight on the car and adjusted tire size. Doing this also required changing the camber. I found slightly wider rear tires helped handling at a small cost of lap times.

The next I did was add parts to improve performance. I have been adding one part, testing the car, adjusting the car’s settings, removing the part and adding a different part and repeating the process. I’ve gotten better at figure out what adjustments the car needs. In general adding parts with higher PI values, improves lap times more but some improve times more than others. I found upgrading the fuel injection system seems to give a larger lap time improvement that other things given the amount it adds to the PI. The problem I’m having with it is adjusting the car to handle to the performance increase. It looks like I may have to upgrade handling parts to accommodate the performance improvement.

1 Like

+5. Fantastic work there, JimB3. Very methodical and so far I agree with the direction that you have been taking.

+1. Been following this with interest. You do realise though that you will get to the end of this process and arrive at the ultimate realisation that it is all black magic! :wink:

1 Like

JimB3: Great trail of learnings! Thanks for the follow-through on your posts on this thread. This will certainly help rest of community, especially those coming onboard wanting to learn to build/tune on FM5.

1 Like

My bread & butter car in FM5 just so happens to be '94 Miata so I had keen interest in this project and could not help but also conduct my own trials.

I have tested the following builds:

  1. Completely stock, except 28/28 psi tire pressures
  2. #1 + race suspension, ARBs, and differential
  3. My current D400 build

The issue at Indy Oval is that the car is only using 30% of the tire grip available which means changes are not going to make much of a difference.

I have tested #2 at 25/25psi, 27/27psi, 28/28psi, 29/29psi, and 30/30psi until I was able to achieve minimum of 2 laps of +/- 0.010 second difference. All but 25/25psi delivered the same results.

#2 was also tested at 45%, 75% & 100% accel diff. Coincidentally, my D400 build had 45% accel differential . . . Getting back to the point, since this large oval would pretty much allow the differential to run open all the time (very large radius) the accel diff. setting should not matter and it did not. 100% setting resulted in slight push but the lap times were virtually identical.

The time difference you are seeing may be due to the fact that there are minute differences between the laps. I’ve found that the run can be made in 4th gear (above redline). This gives better acceleration coming out of corners than running it in 5th gear with sluggish acceleration (relatively speaking). Therefore using the sports gear with adjustable final gear certainly will improve the laptime.

Testing #1 was only slower by 0.100 seconds but it was clearly slower. The CoG certainly would be higher but the biggest difference was both the front/rear cambers were in the +ve in the corners.

The lesson I got out of this was that my spring rate was adequate but ARB could be stiffened + rear camber could be relaxed by 0.1 degree. Lastly, lowering the bump & increasing the rebound dampers really settled the car in the corner where there were bumps. Then I took the #3 D400 car to Nurburgring GP and the car felt so much stable through the corners. The car was able to go full throttle through the chicane and the car was sliding through the fast corners smoothly and predictably. Ended up gaining 0.5 second on my previous Rivals time.

JimB3, thank you for initiating this topic. Otherwise, I would not have had the incentives to make the improvements to my Miata. Goes to show that there is no end to tuning, it is a continuous improvement & refinement process.

Thanks for sharing as well GRD! BTW, so, were you using the initial settings from #3 (your original Miata tune) on #2? To then, adjust #3 again and then gain the 0.5sec at the Ring?

All NBRing changes were made AFTER the Indy Oval testing.

As a reference, the best stock power (with suspension set-up) lap time I was able to get was 1:14.962. Hold that throttle down but the steering also has to be turned in AND held in place without wavering to minimize scrubbing.

Entry to T1 = 122 mph
Exit at T2 = 117 mph
Entry to T3 = 122 mph
Exit at T4 = 117 mph

At no point on track should speed fall below 117 mph. This can all be done in 4th gear. The needle is well into redline but the engine does not top out at 122 mph. If 5th gear is used, the car loses torque therefore it takes longer time to get up to 122 mph.

BTW, the lower the tire pressure more compliant the ride and higher the tire pressure more responsive the handling becomes . . . I found 28/28 psi, as is the case on most cars, to be the sweet spot.

I thought I’d make a contribution to this thread, so here goes…

I’ve been setting up the shock absorbers for Yas-alt in the #1 Chevrolet Indycar for a race I’m competing in on Thursday. To do this, I followed the fairly popular idea in this sub-forum of putting the rebound quite stiff (around 9-13) and the bump quite soft (around 2-6). My rebound and bump settings were:

FRONT R: 9.0
REAR R: 12.0
FRONT B: 2.0
REAR B: 5.0

This was giving me low 1:44’s and the car felt stiff round most of the track and the throttle was very difficult to control. I tried small adjustments to my shock settings, but the car never really settled down and was struggling to break 1:44. After a day off, I came back with the idea of turning the shocks down all the way to 1.0, then turning the bump on the front and rear up by 1 for every lap until the car started to understeer. I did the same thing for the bump and ended up with these settings (which are totally different from before):

FRONT R: 2.5
REAR R: 2.5
FRONT B: 4.0
REAR B: 4.0

With these settings, I was able to hit 1:42’s and the car felt like it was absorbing into the corners and giving me a much smoother throttle response than before. I’m going to try this method out on some of my other tunes and see if this is an effective way of setting up shock absorbers.

Wow! I appreciate everyone’s comments. I’m trying to learn what all the adjustments do. I hope my experiences help other racers. I said I would chronicle by experiences and report on them. I have been tempted to try a different car or just to upgrade the Miata as much as I could and adjust it from there. That is not what I set out to do so I will not give in. Your responses are the support I need to carry on with my initial intent. My intent is to make the most consistently fastest 1994 Mazda Miata for the Indy oval limited to the D class.

WearyMick, I may reach my goal at Indy but there are other challenges.

I plan to continue chronicling my experiences by next tuning the Mazda Miata for the Alpine Festival circuit. This will occur after I finish tuning for the Indy Oval. Those experiences may be chronicled in another thread. I wanted to start with an easy track and the Indy Oval appeared to be the easiest to me. Hopefully any further tuning experiences will be quicker and won’t require as many posts.

I own a special thanks to PTG Baby Cow and GRD 4 3L. Your comments provided me with a great understanding of what is happening with the car.

After another round of tuning, I have found that the higher performance the car has, the more important tuning becomes. This has been most evident with the dampening settings. I have now tuned the car to drive like a dream with the street ignition. The improvement I get with the street ignition is almost the same as the street fuel system upgrade but only adds 6 to the PI instead of 8.

My earlier posts listed what settings I used. I have decided to go away from doing this because I want people to experience what the changes do. I will list what additions I have made and what I adjusted. When I have finished my adjustments, I will share the tuning. I encourage any feedback on my tuning.

Please let me know if you think I should continue to list what settings I am using and what my settings end up being.

I have not finished adding all possible performance upgrades individually. Once I have completed this, I will list my results. I hope to finish that by Friday. I looked at the logs I am keeping. I have already completed over 550 laps at Indy in the Miata. This means I have spent over 5 hours doing this. I have no complaints about this. I would say this is time well spent, but I think we all know better than that. However, I hope my experiences will reduce the need for others from doing the same thing.

On a related topic, has anyone owned a 1994 Mazda Miata? I just received a significant raise at work and might be able to afford one. Is it a good car? I am not too far from Laguna Seca. Do they have track days? I admit I would rather have the 2014 Lamborghini Aventador LP700-4. I would have to cash in my 401k and put a second mortgage on the house. It is tempting, but no. I willing to go through the same methodical testing of the Lamborghini if people are willing to contribute to the purchase. (Microsoft and Turn 10, I am kidding. I hope you understand that.)

JimB3, I would say you are going about this in the slowest way possible and that is a GREAT thing. You are going to bond with that car (if not already). 550 laps! I bet you’ll be able to feel any changes you make to that car because of the seat time. No tune is ever complete without extensive testing as far as I’m concerned.

If street ignition is better than the fuel system, I’ll have to give that a consideration/test!

Bernese is a very good choice for the next track to tackle as it is also a high speed track. Every suspension elements + brakes + differentials come into play for that one.

My recommendations:

  1. Spring/Wheel rate
  2. ARB (works with #1)
  3. Dampers
  4. Differential
  5. Camber (since 1~3 has great influence on this so there’s no point tackling this before them)
  6. Tire pressure (for final fine balance)

If the upgrade changes, this list needs to reviewed again (FM5 minutely changes the spring/wheel rate EVERY TIME the car’s weight changes = annoying)

I’ve done similar work on the Miata but at the Test Track - Airfield (thanks to certain Mini driving rival). This track is very unorthodox because of the inclusion of very high bumps (2 ups and 2 drops) and up/down ramps (enough to launch a car in the air). It also has 2 very large radius corners, a fast chicane, a sharp braking zone, a long 180 degree corner, and a long straight. I tell you, if the suspension is not ready for the job there, the track will let you know.

Here is a quick update. I am continuing to add one part at a time and see what happens. I keep getting surprised at what happens. Here is an example.

I added the street ignition. This added 6 to the PI. The lap times were reduced to 1:13.2. Later I tested what happened when the I added the street valves instead of the street ignition. The street values add 6 to the PI. The lap times for this addition were 1:13.3. The times listed are after some other small adjustments were made to minimize the lap time for the part added.

I looked at what was happening during the laps. I was reaching turns 1 and 3 with more speed with the ignition upgrade. I think this was because the car was accelerating a little quicker coming out of the corners. It appears the ignition helps acceleration more than the valves do. This is a little hard to tell on upgrade page. Both ignition and valve upgrades show the acceleration increasing by changing the acceleration rating green but the number is the same for both ignition and valve upgrades.

Another possibility is the car just handles better with the ignition upgrade. Therefore the car came out of the corner with more speed. Why this would happen, I have no idea. I just find the car goes around the corners better with the ignition upgrade.

The lap time for the ignition upgrade is 0.1 seconds quicker. You may wonder if I just had a perfect lap. I don’t believe this is the case. I do 10 laps when I do the testing. The 10 lap time with the ignition upgrade was about 2 seconds quicker than 10 laps with the valve upgrade. I ran faster more consistent laps with the ignition upgrade.

Just to make sure I understand the process you are using…when you upgrade one part, then, want to upgrade to another…do you take the car to it’s original stock configuration? If not, the game does do things differently depending on how you sequence the part additions.

Anyway, keep up the great work on this experience JimB3…I have been following the thread with keen interest.

p.s. I am sill learning how to better drive, yet, my controller “control” can easily be off by almost 0.5 sec or more at times. And I have to be consistent with the line I am using for a true measure of +/- gains.