Changing the Emira's Weight Distribution

[sbproducer]

Preface:

The V6 stock weight distribution is 39 Front and 61 Rear (this doesn't include the fat ass driver). If a car is super front or rear heavy, you can imagine this can present a challenge with handling characteristics. Theoretically, a 50/50 weight distribution is sought after for better handling dynamics so the fatter you are the better in terms of cornering in an Emira, but not acceleration. Basically, if you are fat, the Emira handles better, if you are skinny, the Emira accelerates better. But, there is another dynamic that plays a role. In a rear-wheel vehicle, the more weight you have over the rear wheels, the better the traction and acceleration, since there is more force pushing the rear wheels down. So, there is a case for arguing that you want a little rear bias when it comes to weight distribution. It's not just a simple go for 50/50.

Google AI Summary:

Corvette weight distribution varies by generation, but a 40/60 rear-biased split is characteristic of the mid-engine C8, while earlier generations like the C7 (front-engine) had a near 50/50 split (often measured at 49.4% front, 50.6% rear), and the C6 aimed for a perfect 50/50 balance. The C8's mid-engine design allows for superior traction and acceleration by placing more weight over the rear wheels.

Thoughts:

Is there a good target weight distribution for the Emira? Should we even be trying to move the needle towards 50/50?

After I finally get a chance to install some of the parts I have, I'll be losing close to 100 lbs. rear. Couple that with my fat ass getting in the car... and the needles moving left for sure. I always thought this was a good thing because the Emira is definitely back-heavy.. I can feel it.. but maybe the 39/61 isn't as bad as we think.

 

[jp129]

Static weight distribution is only one factor. While it does contribute to chassis handling and balance it does not dictate it. My suggestion is drive the car at pace and assess what it is about the chassis handling or balance you don't like.

Does it understeer or oversteer? At what phase of the corner is it exhibiting this? What are your inputs when this is happening? Slow or fast corners or all the same? Etc etc

From there you can address elements like spring rates, damping, sway bars, geometry, track width/tires, and aero to tune the balance to your preference.

I believe those tools are easier to tune and adjust then changing static weight balance, especially as a street car. Race cars have more flexibility in what you can move around to achieve a weight balance.

In the end, it's all a compromise. You just tune the setup to be good at certain things/preferences and less sucky for the rest.

 

[CarGuy11]

This helps reduce rear bias.

 

[MiamiBlue]

I don't like how the car pushes wide when accelerating through a corner. I don't think it's actual understeer (I'm not aware of any tyre grip lost, and you have the effect at lower speeds), but you can feel the turning circle get bigger. If you then come off the power the nose comes back in and tightens the turn.

Is this a result of the weight distribution or something else?

 

[jp129]

That's weight transfer, normal vehicle dynamics - physics.

Overimplication - as you accelerate, you transfer the weight/load to the rear. As you lift, you transfer weight/load to the front. Static weight distribution influences the magnitude of change, but does not dictate the effect.

 

[Ft.S]

Preface:

Theoretically, a 50/50 weight distribution is sought after for better handling dynamics so the fatter you are the better in terms of cornering in an Emira, but not acceleration. ... It's not just a simple go for 50/50.

Thoughts:

Is there a good target weight distribution for the Emira? Should we even be trying to move the needle towards 50/50?

In my opinion and experience, 50/50 distribution represents the best all around compromise for static weight. This is to mean that no matter what you do, how you drive or where you drive, the chassis does not favor one situation over the other.

Weight bias towards the front or rear moves that compromise in a way that the driver can exploit in some situations. Front-bias is very difficult to drive, especially if it is a front-wheel driven vehicle. Mid- or rear-bias is far more easier to drive and exploit.

Generally, mid-engine cars have a weight distribution of ~45F/55R. This gives the driver the advantage shifting weight on the front axle under braking without overloading the tires, while doing the opposite during acceleration to the rear axle. In each case shifting the weight where it is needed when it is needed. Of course, the same is valid in a 50/50 vehicle, but the disadvantage is that too much weight would shift towards the front axle during braking, and corner entry, while not enough weight would shift to the rear axle during accelerations.

Keep in mind that we can generate more than 3 times the negative Gs under braking than positive Gs under accelerations. This means more weight can be shifted on to the front axle under braking that onto the rear axle under acceleration. Consequently, a rear weight biased vehicle should have an advantage just standing still.

The weight distribution of Emira is perfect in my opinion. Under maximum braking the car's weight distribution might be 55 or 60% on the front axle, while still keeping 45-40% weight on the rear axle, hence near optimum dynamic weight distribution. Moreover, the driver can manage that distribution solely based on the brake pressure with a pedal.

If you look at a BMW M3, for example, its static weight distribution is 52f/48r. You might think that is near ideal. The G8x series M cars are amazing under braking, in spite of their total weight. However, they not only rely nearly on just front axle for braking, but also significantly lack traction under acceleration and have difficulty putting all the power their engine produces, particularly during corner exits and even with their tricked-out 4WD and eDiff.

I collected expanded amount of data from the vehicles I drove for over 15 years on track, including BMWs, mid-engine and rear-engine cars. I kept analyzing and analyzing so many things to improve my driving; I am just over-analytical. At the end, I came to three conclusions: (1) Rear weight bias is good, mid-engine bias is best for great drivers, (2) every driver has their preferences and beliefs about weight distribution on what is best for them (rear-bias suits me the best), and (3) I will never be a great driver.

So, I would suggest instead of trying to change the weight distribution of the Emira, see if you can unlock some of its hidden gems as a driver. I am personally looking forward to doing so once I finish the break-in and get on a track.

Respectfully,
Ft.S

 

[CarGuy11]

Here’s my comparison of C7 and Emira weight distribution.

 

[me73]

There's not much point in trying to change the car's weight distribution to a significant degree. The significant parts from a mass perspective are where they are and you can't really change them with little tweaks.

If the weight distribution is a significant issue for you, you're best off buying a different car. The 45/55 of the Boxster/Cayman is the most evenly distributed rear-mid engined cars I'm aware of. Of course now those are only available used... They are a very easy car to drive fast. There are SO many front-mid engined cars with a 50/50 balance from the past to choose from. I've had a few and found them generally very easy to drive fast and forgiving.

However, I've found that there's a lot to enjoy in leaning to drive the Elise and now Emira effectively. You have to pay closer attention to when you brake, turn and accelerate to make the car behave smoothly. It takes more skill, and to me, that's the point.

 

[jp129]

This is to mean that no matter what you do, how you drive or where you drive, the chassis does not favor one situation over the other.

While I agree with the points you are making and especially the point about addressing chassis behavior via driver input first, I have to respectfully disagree with the statement that whatever you do/drive/where you drive it doesn't favor one axle over the other.

My racecar is an S2000 that is purpose built and has a 50/50 weight distribution. How I tune the chassis has a drastic effect to its axle balance. On certain tracks or conditions I have to change the front end balance or I get loads of understeer at the limit or vice versa. So I change setups for certain tracks or have adjustable sway bars to tune with.

So while I agree static weight distribution influences chassis balance, there are many other factors that contribute to your overall chassis balance. Yes, ideally striving for 50/50 is a good strategy, but there are other tools to influence balance outside of static weight dist.

Spring rates, damping, sway bar, geometry, track width, tire, and aero. All have a significant impact on chassis balance.

My S2000 race car on the scales in competition trim & driver (130lbs)

This is my Emira V6 manual on the scales:
Fuel full tank with driver (130lbs)

Just my experience and 2cents as well.

 

[NorCalEmira]

A mid engined car offers the best compromise across a range of handling dynamics scenarios when a car is in motion. That's why we see it used so extensively in supercars and of course, in Formula one where the only objective is to maximize performance at any cost and there is no concept of building a platform to a price point.

A mid engined care positions it's engine ahead of the rear axle and while the actual weight distribution can vary, it's distinguished from a rear engined car like a 911 which positions much of its engine weight behind the rear axle. Even the 911 has started to shift more weight forward in more recent generations.

A 40/60 front to rear weight distribution is common for mid engined cars and you'll find that spec or close to it across many of the best handling cars ever manufactured such as the first and second generation NSX and a number of McLaren models as you can see in the chart below.

 

[Ft.S]

@jp129 I am with you, mostly, on what you wrote. And you are giving a perfect example of how to manipulate weight distribution for racing purposes. The statement of mine you quoted was about 50/50 static distribution specifically. As soon as you change that the results will be different as you are eloquently pointing out.

The only part that I disagree with you, and that is not about the fundamentals, is that 50/50 distribution is ideal. I do not believe so, it is the most compromised setup IMHO. However, this statement is very dependent on the driver, and as a driver, I am at my best when the distribution favors the rear by a significant margin. I cannot explain why as I do not know, I just drive better with such configuration.

Many years ago, a friend of mine asked me to drive his S2000. I thought the car was a maniac and I just could not control it. He consistently drove the car to winning many races, as I think you can relate as well. Somehow, my butt is favoring a rear-biased car.

Cheers.

 

[bshads]

The things you should be worried about regarding weight for performance are:
1. reducing static weight for low speed corners
2. balancing how the springs hold it for consistency
3. adding dynamic weight (aero) for high speed corners
Lots of options to achieve the above.

Note that the Emira has the same static weight balance as the current GT3RS, which is the most planted car that I've ever driven on a circuit. Even moreso than my proper GT4 racecar.

50/50 matters if you are trying to maximize mid corner on a car with the same F/R tires at the point between braking and accelerating. Once you start staggering tire sizes, it's no longer the optimal balance as you'll lose grip on the narrower tires first, meaning less front steering at mid-corner, meaning more understeering. Generally that's not very desireable for performance.

 

[NorCalEmira]

@jp129 I am with you, mostly, on what you wrote. And you are giving a perfect example of how to manipulate weight distribution for racing purposes. The statement of mine you quoted was about 50/50 static distribution specifically. As soon as you change that the results will be different as you are eloquently pointing out.

The only part that I disagree with you, and that is not about the fundamentals, is that 50/50 distribution is ideal. I do not believe so, it is the most compromised setup IMHO. However, this statement is very dependent on the driver, and as a driver, I am at my best when the distribution favors the rear by a significant margin. I cannot explain why as I do not know, I just drive better with such configuration.

Many years ago, a friend of mine asked me to drive his S2000. I thought the car was a maniac and I just could not control it. He consistently drove the car to winning many races, as I think you can relate as well. Somehow, my butt is favoring a rear-biased car.

Cheers.

If a 50/50 weight distribution and front engine placement were advantageous, we'd be seeing that configuration in Formula one and we don't.

If you want to improve weight distribution on the Emira, just sit in the drivers seat adding 200 pounds or so forward of the rear axle and consider a lightweight battery. If you want to change handling dynamics, look at spring rates, anti-roll bar stiffness front to rear and adding well designed aero but don't worry about the weight distribution of the Emira.

The Emira is in good company...In addition to the list I shared previously, here are other highly regarded sports cars with a 42% front, 58% and the list goes on:

1992-1998 McLaren F1 road car.
1995 Ferrari F50
2019 McLaren GT - (42.5/57.5)

 

[geoffbland]

If a 50/50 weight distribution and front engine placement were advantageous, we'd be seeing that configuration in Formula one and we don't.

To be fair, there are rules in F1 meaning that cars can't be 50/50 balanced. However, the current 44/56% +/- F1 weight-distribution rules were chosen to be what was considered by the drivers at the time to be the ideal balance for a mid/rear engineered race car.

https://www.fia.com/sites/default/f...echnical_regulations_issue_8_-_2024-06-24.pdf

 

[jp129]

@jp129 I am with you, mostly, on what you wrote. And you are giving a perfect example of how to manipulate weight distribution for racing purposes. The statement of mine you quoted was about 50/50 static distribution specifically. As soon as you change that the results will be different as you are eloquently pointing out.

The only part that I disagree with you, and that is not about the fundamentals, is that 50/50 distribution is ideal. I do not believe so, it is the most compromised setup IMHO. However, this statement is very dependent on the driver, and as a driver, I am at my best when the distribution favors the rear by a significant margin. I cannot explain why as I do not know, I just drive better with such configuration.

Many years ago, a friend of mine asked me to drive his S2000. I thought the car was a maniac and I just could not control it. He consistently drove the car to winning many races, as I think you can relate as well. Somehow, my butt is favoring a rear-biased car.

Cheers.

That's very fair.

I don't think I should have used the word "ideal strategy." I'm with you on that as it certainly has its disadvantages and it isn't something to strictly strive for.

I havent had enough time in the Emira on track to have trending data to compare and it's HOT AF on TX right now, but I'm really looking fwd to lots of seat time.