How to handle a front mid engined car?

[hedges88]

Hi All,

This is a weird one because it's very specific

I believe I'm fairly good at car control, unlike most petrol heads I prefer the tried and tested front engine front wheel drive layout. I enjoyed my previous Civic coupe very much with the double wishbone suspension all round. I had good tyres on the front and cheap ones on the rear and it was such a joy to provoke lift off oversteer that was easy to recover from. I could hustle that car with predictable and assured confidence.

Now I have a W169 A-Class, and what I'm asking would equally apply to a W245 B class I'm not entirely certain on driving technique to get the most out of the chassis. The engine lays almost completely flat under the car and is completely behind the front axle so it is truly a front mid engine front wheel drive car. Initial turn in and grip is phenomenal it's quite surprising, and the adaptive dampers firm up to improve the experience. It's then the rear end I find difficult to control. It's a parabolic rear axle so the rear wheels are not even joined straight together with an axle but. There is no rear anti roll bar.

After turn in you can't really lift off to bring the rear around because they just don't really break traction. It seems so far like you have to rely on the weight of the engine to keep traction on the front wheels when entering a corner at speed but if you misjudge it you just get a frightening amount of understeer.

Say you took a W169 or W245 to the Nurburgring or something, what would you do to get through the bends and quickly and safely as possible? Do you need grippy front tyres and then just rely on the weight of the engine under you and keep a bit of power on during cornering so as not to upset the balance of the car without breaking traction at the front?

[noumenon]

Sounds like you need to get yourself on a car limits day at north weald. It's been a while since I've been on one (and I'm not affiliated in any way), but Andy will have you rethink everything you knew about car control.

I bought an MX5 (Eunos) 1.6 mk1 to learn RWD. I made the 'mistake' of saying it was underpowered and didn't oversteer. Cue Andy and a mm or two of rear tyres turned into spoke in effortless low speed donuts.

[Agarange]

No rear anti roof bar means it likely to be a bit lively with lack of contact on one wheel during a turn. Quick changes in direction should more easily lead to a slide.

Over steer is easily provoked with a rapid change in direction and a bit of throttle. One does not need brute force from the engine to break traction. That course at North weald sounds good. I will ha e to look it up.

[snowandrocks]

I think the "frightening" amount of understeer is a deliberate feature of the chassis setup to prevent this even more frightening occurrence.

While I enjoy getting the most out of any car I drive, including my diesel Hilux, this does seem a bit of a strange car choice for someone who enjoys pushing a car to it's limits - still wondering if this is a wind up!

[noumenon]

snowandrocks said:

I think the "frightening" amount of understeer is a deliberate feature of the chassis setup to prevent this even more frightening occurrence.

While I enjoy getting the most out of any car I drive, including my diesel Hilux, this does seem a bit of a strange car choice for someone who enjoys pushing a car to it's limits - still wondering if this is a wind up!

Yes, that's the elk test and this really happens with some cars. I hadn't realised this was the car being talked about (W169). From memory they added a ton of understeer and redid the ESP to try to mitigate this.

[niva441]

No it was the early production W168 that failed the elk test, then lowered and stiffened with ESP to pass.

[noumenon]

niva441 said:

No it was the early production W168 that failed the elk test, then lowered and stiffened with ESP to pass.

Thanks. I should really have googled before replying. =)

[snowandrocks]

niva441 said:

No it was the early production W168 that failed the elk test, then lowered and stiffened with ESP to pass.

Although it was obviously the earlier model that failed, I'm pretty sure the later car shares the same sandwich construction and associated high centre of gravity so will be setup to safely understeer to avoid the risk of anything more dramatic.

[niva441]

Yes different rear suspension, but very much set up for understeer. As I recall you really would need to try hard to create anything else.

[wyson]

snowandrocks said:

this does seem a bit of a strange car choice for someone who enjoys pushing a car to it's limits - still wondering if this is a wind up!

I thought this as well. Like someone buying a MX 5 and asking how to put a roof rack on it because they want to shift furniture as part of a removals business.

Like others have mentioned, the car would need a geometry and ESP change to get rid of the understeer, then it’s likely to topple over in extreme manoeuvring. The foundations aren’t there.

OP, ditch the Mercedes, get a Fiesta or old Civic Type R or similar if you want a car that will entertain, lift off oversteer and move around beneath you.

Edited by wyson on Friday 26th November 06:57

[Furyblade_Lee]

What are you ultimately trying to achieve? A fast lap time, or oversteer in a FWD car?

[hedges88]

Furyblade_Lee said:

What are you ultimately trying to achieve? A fast lap time, or oversteer in a FWD car?

Neither. I used the inability to provoke lift off oversteer to highlight that the rear wheels really are just along for the ride. I did find out that higher powered versions do have a torsion bar at the rear which I wonder if it can be retrofitted.

Forget lap times, were talking about a small hatchback with 95PS. My question really was if you are driving a car with the weight of it's engine and transmission entirely behind the front axle, then what would be the best driving techniques or skills to make the most from that layout? If Shumaker had to use a car like that what would he do to get the best out of it? That's what I'm asking, in terms of layout and design how to get the best from it

It's initial turn in and weight transfer are excellent, it's 2mm shorter than a Ford KA and has a short wheelbase. The vehicle maybe tall and high but surely the weight of the engine and transmission below the floor makes it have a relatively low center of gravity!

Would it be best to enter a turn at speed having already thrown the weight of the vehicle into the corner then rely on engine braking!

This is a unique situation applying only to the W169 A class and W245 B class, the old W168 has a different rear suspension setup

[wyson]

It has a high centre of gravity. People sit high on top of the sandwich platform. I remember reading a 4 cylinder engine is about 100kg, even with just a 70kg driver, that is a significant counterweight perched high up.

And even Schumacher wouldn’t be able to make your car have an oversteer balance. I’ve watched videos where racing drivers drive regular cars, who then moan they won’t do want they want, just understeer, short of giving it a bung or using the handbrake, both dangerous behaviours on public roads. If the car isn’t set up right, your talent won’t make a difference. And because of the high crossover / SUV like centre of gravity, giving your car enough front end bite to make the rear step out will result in it tipping over ala elk test.

Give up op. The fundamentals for your car aren’t there.

Edited by wyson on Wednesday 29th December 14:05

[hedges88]

wyson said:

It has a high centre of gravity. People sit high on top of the sandwich platform. I remember reading a 4 cylinder engine is about 100kg, even with just a 70kg driver, that is a significant counterweight perched high up.

And even Schumacher wouldn’t be able to make your car have an oversteer balance. I’ve watched videos where racing drivers drive regular cars, who then moan they won’t do want they want, just understeer, short of giving it a bung or using the handbrake, both dangerous behaviours on public roads. If the car isn’t set up right, your talent won’t make a difference. And because of the high crossover / SUV like centre of gravity, giving your car enough front end bite to make the rear step out will result in it tipping over ala elk test.

Give up op. The fundamentals for your car aren’t there.

Edited by wyson on Wednesday 29th December 14:05

Again, I'm not looking for oversteer etc. I think people misunderstand what I'm asking. We all know how to drive front wheel drive cars, we know what to do with rear wheel drive cars etc. There's plenty of education and advice. My car is not a sports car, it's slow and quite frankly it's a granny grocery getter, im not talking necessarily about going racing but it's more a hypothetical question

Say my ESP system failed and I had to perform an emergency manoeuvre, what would one expect from a front mid engined car? I'm literally talking from a physics and driving dynamics point of view. Would it be liable to be difficult to control or more prone to sudden oversteer Vs a normal FWD car?

Edited by hedges88 on Wednesday 29th December 14:35

[thebraketester]

Drive the car… you’ll figure it out.

[wyson]

thebraketester said:

Drive the car… you’ll figure it out.

https://www.carlimits.com/

Take your car on a day like this and test it out with expert tuition.

Its really fun and a great thing to do with a new car, see how it behaves at the limits. You probably want the runway day to answer your question?

I bet it will only terminal understeer though. I remember reading the car mag reviews back in the day, as I briefly considered getting an A class. They all said the car understeered badly and had to be set up that way because they were fundamentally compromised by the sandwich platform and it put me off.

Edited by wyson on Wednesday 29th December 18:54

[biggbn]

I had a two door A class, absolutely brilliant little thing, always fancied the turbo version as an assuming sleeper

[hedges88]

biggbn said:

I had a two door A class, absolutely brilliant little thing, always fancied the turbo version as an assuming sleeper

Yeah it's sad because they dropped the A200T and the 3 doors when they facelifted the range, certainly in this market anyway not sure about other regions. Quite a lot of the A200T models are CVTs , the manuals are pretty rare.

They are amazing cars. Unbelievable space inside, probably the closest thing to a real life TARDIS.