Tuning Frustration, Very Aggravated. Help?

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1

Like a lot of others, i’m new to tuning and have gotten very aggravated because i’m messing the tune up more and more with each aspect of fine tuning certain problems. I apologize if this gets long winded, but there’s a lot i don’t understand. I mainly race A Class with a few cars for certain tracks. For the purpose of this post, I am going to use the '05 Lotus Elise, A Class build I have for the Road Atlanta tracks. Mainly the short course. Probably not the best choice, but I like the car and have driven it on these two layouts with downloaded tunes that either have excellent handling but poor speed or poor handling and excellent speed. I’m trying to balance that.

First, I use the Forza App to get a baseline tune. Even that is a little difficult as there is no explanation of a few things. But I seem to manage it fine. Once I have that tune and have written everything down, I make a tire pressure adjustment from 27 to usually 28 and then run about 5-7 laps just to see how the car handles on line, off line, etc. During laps 4-6, I will bring up the tire temp screen and watch it as I go. 99% of the time, off the base tune and after my own adjustments, the temps are all within a few decimal points.

IE: 190.2/190.2/191.3, But after my adjustments, the car handles like crap. But this tells me the Camber settings are fine (from what I’ve read). And the tire pressure is always in the very 31 to very low 32 marks.

I’ve read a lot of guides, but I haven’t come across a guide that explains the science of fine tuning. When to tune this, but not that. Why to tune this, rather than that, etc. I guess that’s why i mess my stuff up so bad!

Anyway, Here is the current set up I am running on the Elise.

Upgrades:
Exhaust: Sport
Camshafts: Street
Brakes: Race
Anti-Roll: Race
Chasis: Sport
Weight Reduction: Race
Transmission: Sport
Driveline: Race
Differential : Race
Tire Compound: Street
Aero: Both Adjustable
Ignition: Sport
Springs & Dampers: Race

Engine Swap: 1.6L I4 Turbo Rally

Car Info
PI: 700
Speed; 6.3
Handling: 5.7
Accel: 9
Braking: 5.7
Horsepower: 379
Weight: 1702/40
Speed: 170
Front Tire Size: 175/55/16
Rear Tire Size: 225/45/17
Rim Size: Stock
Torque: 294
Redline: 8200
Torque RPM: 5500

Baseline App Tune
Tires: 27/27
Camber: -1.8/-1.8
Toe: 0/-0.2
Caster: 6
Anti-roll: 19.8/13.2
Springs: 274/430
Ride Height: 5/4.6
Aero: 50/25
Rebound: 4.7/7.1
Bump: 3.3/5.1
Brakes: 54/85
Differential: 60/10

Without any tuning adjustments, the car seems to have a lot of understeer going into corners, thus causing me to slow down too much to correct it. The rear is also very loose and likes to slide around a lot. The first turn is fine, it’s every turn after that where the issues are. The last turn before the finish line is certain death with the tire wall, even if running the suggested “perfect line”.

So, now i begin making my tuning changes. To correct the understeer issue, i know I can adjust the ABR settings, the Rebound and Bump settings, Spring settings and in some cases, Differential settings. The question is, which one first and why that over the others?

It seems the more I adjust to compensate, parts might get better while others worse and in the end, after all the adjustments, I am right back to square one with the excessive sliding rear and massive understeer.

Currently, these are my settings on the car.

Tires: 28/28
Camber: -2.5/-1.5
Toe: 0/-0.2
Caster: 4.2
Anti-roll: 18.22/22.36
Springs: 274/430
Ride Height: 4.8/4.4
Aero: 75/200
Rebound: 4.3/6/9
Bump: 4.3/5/9
Brakes: 45/135
Differential: 60/10

I don’t get excessive body roll or lunging when breaking. Just a sliding rear, understeer and a massive straight line push when getting on the throttle coming out of a corner.

Idea’s, thoughts or help?

2

The problem is your car. Rear engine cars have a lot throttle off over-steer on entry and under-steer to snap over steer on exit. There is tuning tricks to help, but it’s more of driving style adjustment that will give you the most results.

I personal adjust my brakes more to the fronts and go up on my deccel to manage throttle off oversteer.

But rolling on and off throttle and brakes will help tremendously. Controlling the weight with inputs has much bigger impact with these cars.

I’m more of a driver than a tuner, but I hope this helps.

3

I’m looking for those tuning tricks. Out of the front engine, rear wheel drive cars i use, this is the only one so far with this issue. Even the viper i’ve tuned doesn’t do this. I understand it’s a lightweight car, but there has to a way to tune it. the question is, what to tune.

4

Last time I remember the lotus was a rear engin car.

5

This car neesds all the aero it can get. So max out aero front, this will also reduce understeer. Also slam down ride height. makes the car more stable. Your front rebound is way too low, you can almost double it, this will stabilize car under braking and acceleration. Your rear bump is too high, you can almost use half the value. High rear bump is one reason for on throttle oversteer. Also your ARBs are way too stiff for this lightweight car, you can run around half the amount.

Try these settings for example:

Tire Pressures 28.0 28.0
Camber -2.7 -2.1
Toe 0.0 0.0
Caster 5.0
ARBs 7.22 13.96
Spring Rates 290.9 415.3
Ride Height 4.6 4.2
Rebound 8.2 7.9
Bump 4.3 4.1
Brakes 48% 125%
Aero 100 200
Diff 68% 34%

You can reduce rear aero slightly if you want to reduce that little understeer.

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6

Another thing to consider for the on throttle understeer is the engine you are using. The rally engine reaches it’s HP peak early and drops quickly at higher rpms. That means with an already quirky car, your on throttle power could be excessive. That would mean you’d have to have an extremely light/deft touch with throttle control. Switching back to the stock engine or another option with a more linear power curve might help as the power would not peak right away, but build instead on your corner exit. That would give you progressive understeer instead of rapid understeer to snap oversteer. You would still need good throttle control, but it shouldn’t be as sudden. I also found that raising the caster to 5.5 really seamed to help with braking sensitivity.

I am generally a fan of low rpm power/torque, but have been tuning this car as well and ran into similar issues. It was so bad, I was losing traction just shifting gears at first, and that was at 500 PI. I am tuning for Sonoma with this car and came to different solutions than Fifty Inch, but don’t have access to check it right now. I am pretty happy with it, but am still 3 seconds off the top time for Sonoma, so it needs work. I am confident I can drop another second with this build with a better run though. I’ll post it when I get home.

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7

Build doesn’t add up. 1.6 only 3 restrictor has upgrades 373hp/435hp/497hp. The 3.7 with sport cams will net you 379hp/280ft and 692 build. Add sport ignition will get net you 391hp/288ft and 700 build.

I took your tune for a spin on YAS north. Ran a 114.3.
Brakes too much bais towards the front and way to low for me.
A lot more understeer everywhere than expected.
ANY oversteer came from improper driving inputs.

50 inches
113.6
Much more balanced tune.
I’m not sure if full aero was optimal for my test track.
Brake bias come slightly more to the front and I ran 140psi brake
Edit… I also noticed the backend is bottom out.
I think the build is flawed if build if there is a Cammed 3.7.
I went with 1.6 motor (435hp) and dropped the the tire compound with 50 inches setting and ran 112.2

8

thanks for the input’s.
Let me go back and look at the build itself then go back to the tuning.

9

Yeah he mixed up the 1.4 rally engine with the 3.7 motor. And also to forgot to mention the aero parts.

Other than that the build adds up to 700.