Please help me understand this behavior

[suponji84]

Hello,

As English isn't my first language, and I may lack the vocabulary to do some proper research about this issue, please forgive me if it has already been discussed previously.

I would like to understand a specific behavior that some cars have. So far, I have witnessed it in 4 cars :

• Subaru BRZ Sti Sport 18
• Silvia Q's S13 88
• Porsche 911 Turbo (930) 81
• Honda Integra (I forgot which version, sorry)

I added minor parts. Adjustable suspension, Fully Customizable Computer, Semi-Racing muffler, for example. It doesn't seem to be too much, but very quickly, something happens. In fast corners, the front part of the cars goes on the inside way more easily than normally, completely breaking the balance and making the car impossible to control. It also tends to happen when exiting a corner and re-accelerating.

Picture a line, on which the car is going. The back part of the car doesn't move from the line, but the front part of the car is moving way too much inside the line. It feels like the car is suddenly able to turn way more than it should, if it makes sense. It doesn't feel like what I think is "normal oversteer", when the back of the car gets away from the line, but the front stays on it. Maybe I'm not understanding it correctly.

The fact that it happens with such a variety of cars (FR, RR and FF) makes me think it could be some sort of unintended behavior or even a bug. Maybe I'm wrong and it's a common issue that people have been able to fix before.

If this makes sense to you, and you would like to educate myself, please let me know about your opinion. Thank you in advance for your help!

 

[eran0004]

What do you do in these high speed corners, do you lift or go full throttle? Does it also happen without the suspension upgrade?

 

[suponji84]

Thank you for your reply!

So I was testing on Grand Valley Highway 1. When you start a time trial session, you're right at the exit of the chicane before the two turns leading to the tunnel that leads to the main straight. Also, think about the series of fast turns right after the first chicane. To be honest, it seems to happen regardless of what I'm doing. If I brake a bit before a fast turn, and then re-accelerates for example. If I just lift the throttle and turn without re-accelerating. If I take it full throttle. I didn't notice a pattern when I was testing. I will test again later today and I will try to focus more on these details to see if I notice something that I didn't notice before.

If the car hasn't been upgraded at all, it doesn't happen. I haven't tried to remove the suspension upgrade while keeping a bit of extra power so I will also test this later today.

By the way, does it make sense to you? Is there a word that could be used to describe this behavior?

Once again, thank you for your help.

EDIT: I would like to add one thing. This behavior only happens when I add parts to a car. It never happens with a fully stock street car, a racing car, a professionally tuned car, etc.

 

[bread82]

This sounds very much like it is caused by the suspension settings. It is unlikely that a mild power increase from the computer and exhaust could alter the handling this much. Have you adjusted the suspension settings or just installed the fully customisable suspension and used it with the preset settings?

If you have used the preset values:

The custom suspension usually has large camber angles, 3 degrees in the cars I've seen. Whereas the stock camber on many road cars is 0.5-1.5 degrees. This might be causing you the problem as increased front camber will make the car's turn in very responsive and sharp. Also increased rear camber can cause issues especially when braking and turning, or using the accelerator. I'd recommend adjusting the camber on the upgraded suspension back to what it was with the standard suspension.

The other default settings on the custom suspension (lower ride height, stiffer springs) should be OK.

Go for a test drive and see how the car feels with default camber. 🍻

 

[vonMarshall]

I had this on a couple of the cars you mentioned and on my Alfa 155.

I rectified it by raising the front setting. I think I had it too low and under braking, as the nose dips down, the body would rub on the tire, particularly on the inside one if I was turning, and then tug it around.

Priano’s tune for the 930 is a gem!

 

[suponji84]

@bread82 & @vonMarshall thank you for your replies as well. I apologize that I wasn't able to follow up yesterday as I was a bit busy. I will check everything you're talking about and will also try to provide a small video of my issue if it makes it easier to understand. Thank you!

 

[suponji84]

Ok, I had time to do some tests after work today.

First of all, I would like to thank you once again for your replies. @eran0004 and @bread82 you were both right about the suspension. It seems to be the culprit.

I first compared with and without the suspension upgrade as suggested and I could already notice a big difference. With the Height-Adjustable Sports Suspension, the car immediately became unstable as initially described. If I kept the stock suspension, the problem was almost nonexistent - of course, if I pushed the car a lot, it would still be here, but it would take a lot more to push it to the limit. I tried adjusting camber settings, but I couldn't notice a difference. The thing that made a big difference was increasing the body height a little bit.

If I wanted to keep the preset values for the Height-Adjustable Sports Suspension, I was also able to make the car more stable by decreasing downforce in the front, and increasing it in the back. It seems that I need to find a balance in terms of grip. Maybe the car has "too much grip" and wants to turn too much. Maybe I'm completely wrong. What do I know, I'm like a monkey with a toolbox and I have no idea what I'm doing.

Either way, I think I'm slowly getting there. At least it was a step in the right direction and I was able to fix this issue a little bit. Once again, thank you all for your help!

 

[bread82]

Very interesting, and glad you solved the issue. Out of interest, what tyres were you using?

 

[suponji84]

Thank you!

I was using Sports Hard tyres for all the cars I tested.

If you're interested, I can tell you a bit more about this idea. The plan is to create some interesting cars that I can use with a friend when we're racing together. Normally, we use street cars or professionally tuned cars. We want to use iconic cars or just cars we generally like. I'm inspired by professionally tuned cars to create a "punchier" version of a car. I'd like to add some parts from the Club Sports and Semi Racing section, so the car becomes realistically faster within reason. The car needs to be enjoyable to drive but also not glued to the road so it still needs to be slightly challenging to handle.

 

[bigmull]

It also can be the LSD settings,the braking value can really effect the car in the corners as if there was something stopping it turn,I generally have mine set around 17 ish and acceration to the low 50s which tends to push the front round in the corners. It is worth mentioning that some liveries need you to have quite high ride settings to avoid the body impeding on the tyres. I always use the same rim size and settings on my cars,wide offset,wide width and 15 inch or less,it might be wishful thinking but I think the tyres wear better than low profile tires as there’s more mass to absorb heat with the chunky tires.