Exige - the Diff debate

[nerobi]

A lsd would help to the exige,wouldn't it?

 

 

Edited December 14, 2016 by nerobi

[The Pits]

It already has:

CBC (corner brake control)

DTC (drag torque control)

EBD (electronic brake distribution)

TCS (traction control system)

ESC (electronic stability control)

EDL (electronic differential lock)

So the Exige is far from the old fashioned notion of an open diff that certain less informed quarters of the internet will have you believe. In 3.5 years I haven't missed a mechanical diff much at all, certainly not worth the understeer penalty for me. No hindrance to having fun on wet track days either. But Matt Becker did say that the V6 was right on the edge of needing a mechanical diff so it will be interesting to see where Lotus go for higher power versions. The chargecooled Evoras have them already and, I might say, without any understeer penalty.

Then again the McLaren P1 doesn't have a mechanical locking diff either, none of the McLarens do, but sure we've discussed this quite a few times already.

[NW76]

I am not sure if a mech. Diff will really make the car a lot better to drive on track ... in theorie yes, but the EDL is pretty good already imho ... its not a cheap upgrade anyway ...

For drifting purposes it would certainly help but the Exige is not a drift Weapon for me anyway ?

[Arun_D]

Silky, Mr P. Silky.

I was quite envious watching the 3-Eleven Silverstone videos over the weekend and was longing to get back out onto a wet trackday to practice limit control in the car. My first trackday in the Cup was just that, and I definitely found the limits that day (and went over them a couple of time too, which is all part of the process). If the venue offers enough space and the track is quiet, then I think such days should be seen as an opportunity for the confident, rather than languish in the pits all day, praying for a break in the clouds.

I found sensing the limit (and the subsequent catching) quite difficult in the Exige, so in a way the car provides a real challenge if this is a skill you want to learn. Mid-engined, short wheelbase is never going to make you an instant drift-hero compared to front-engined RWD. This is one thing I love about these cars (and it was same with my S2), in that it requires patience and concentration to extract performance, in-turn developing your skillset behind the wheel. In contrast, when I had my R26.R, I almost found it dull in the way you could take it by the scruff, take liberties with it and it always flattered you. Lapped like nothing else, mind. My mk2 Focus RS was a brute and required real finesse to lap tidily, but ultimately was more fun and rewarding than the better regarded French track hatch. 

An LSD may help with predictability for tail-out antics, but the negatives in this application have also been well versed. For an OEM it's amost a no-brainer now modern ABS/ESP controllers from the likes of Bosch can be packed to the rafters with individual wheel braking based features that work off your familiar wheel speed sensors, a steering wheel position sensor and very very clever little gyroscope. The effectiveness of it's implementation is of course down to how it's all calibrated but the benefits to the 95th percentile user are clear vs simply chucking a torque biasing diff in. 

[Seriouslylotus]

8 hours ago, The Pits said:

It already has:

 

EDL (electronic differential lock)

So the Exige is far from the old fashioned notion of an open diff that certain less informed quarters of the internet will have you believe. In 3.5 years I haven't missed a mechanical diff much at all, certainly not worth the understeer penalty for me. No hindrance to having fun on wet track days either. But Matt Becker did say that the V6 was right on the edge of needing a mechanical diff so it will be interesting to see where Lotus go for higher power versions. The chargecooled Evoras have them already and, I might say, without any understeer penalty.

 

Hmmm

The EDL is not an electronic diff. Its electronically controlled brake actuation which stops the wheel with no grip spinning (hence why these cars eat rear pads when the traction control is left on)

Very few cars actually have a locking diff (they are very aggressive in operation and not road friendly)

The other two types of LSD are the torque biasing ones like the Torsen and ATB quaife, and the plate type diffs.

The Evora 400 uses the torque biasing diff and these are not aggressive at all (Ford use them in the fwd Focus RS etc etc)

With regards to additional understeer, That's one of the nice points about the ATB type diffs they are reasonably good at not upsetting the cars balance too much.

I ran a proper plate diff in my S2 and would have one in my V6 cup in an instant. Any changes in balance are very very easy to dial out. I have found that the torque put out by the fantastic V6 engine we have in our great cars can very very easily break traction on the inside rear wheel (easy to drive around but an LSD would make such a difference IMHO). Some will say leave the electronics switched on, sadly I find them intrusive....Not say they don't work, I just don't like the feeling they give when they are working.

1 hour ago, Arun_D said:

 

 

An LSD may help with predictability for tail-out antics, but the negatives in this application have also been well versed. For an OEM it's amost a no-brainer now modern ABS/ESP controllers from the likes of Bosch can be packed to the rafters with individual wheel braking based features that work off your familiar wheel speed sensors, a steering wheel position sensor and very very clever little gyroscope. The effectiveness of it's implementation is of course down to how it's all calibrated but the benefits to the 95th percentile user are clear vs simply chucking a torque biasing diff in. 

Arun, as I typed earlier, the Lotus electronics are very good on the road, on track they do become tiresome for me so I now , in the dry always have them switched off. The car behaves very very well but just occasionally a torque biasing LSD would make the package, for me, perfect.

Please don't think im trying to be inflammatory, its just I have different experience with my own car than some of you guys

Edited December 14, 2016 by Seriouslylotus

[Jokke Vlo]

Yes for me the LSD wasn't an upgrade in driving pleasure. NOT at all !

[Arun_D]

@SeriouslylotusDave, not to worry, my personal preference would be the same as yours if mechanically speccing a Cup car myself. I was merely applying some reasoning to their logic in appeasing the 'average' enthusiast's requirements with a brake based system, as we're seeing more and more with performance road cars.  I too very much dislike the feeling of the inside wheel chirping and as you've mentioned, a torque biasing differential is a nice and benign way of helping that, whilst avoiding the drawbacks of the fully locking type. Let's not forget Lotus saw fit to ditch the open diff for the Cup 260s in favour of a torque biasing as standard.

[The Pits]

Using the rear brakes does the same job as a diff as far as physics is concerned and no-one seems to complain about how McLarens handle using much the same principles. I never claimed the Exige had an electronic diff as in an electronically controlled mechanical differential like Jaguar, BMW use only that Lotus call their system EDL, it stands for Electronic Differential Lock and that's from the owners manual.

An ATB diff won't stop the inside wheel from spinning up in all circumstances which is what most of the internet experts claim they want. So I don't think an ATB is the be all and end all either. All this stuff is just regurgitated from car mags and people like Chris Harris going on about LSDs. What they never tell you is that the benefits of LSDs apply more to heavier, wider cars and less to smaller, lighter, narrower cars. Chris Harris and his mates spend more time driving the former and have to smoke tyres for a living so I believe this is where most of this is coming from. Yet now we have half the internet banging on about LSDs, brake pads, geo and understeer without ever actually looking at how they are driving! 

Smaller, narrower, lighter cars have smaller radius paths of travel and distribute their weight better (left to right) during cornering which means the inside wheel torque is less likely to take most of the power, they are inherently less likely to spin up the rear wheels. In a small, mid-engined car with great traction like the Exige this again becomes far better contained than in something like a Honda S2000. In addition, the outside wheel torque is less likely to cause understeer so the benefits of an lsd are reduced compared to on a wide, heavy car whereas the added weight and drivetrain loss remains the same.

More to the point, in quite a few years of Elise and Exige ownership I have honestly never be troubled by the inside rear spinning up and there's nothing I feel I can't do with the car because it doesn't have a mechanical LSD. It can and will drift and oversteer all day long if required. If I honestly felt I could improve the car's handling with an LSD I'd be happy to have one fitted. I'd love to try one with an LSD fitted to see what the real world benefits are. I doubt there are any at all on the road and only very occasional benefits on the track in certain conditions and that's if it has been set up properly which is another whole issue.

I have also said from the beginning that Matt Becker acknowledged that the V6 Exige was close to the point of needing a diff, also that Lotus had fitted a diff to the Evora and I will go with Lotus on this over any internet expert. I have nothing against diffs, I have one on my race Caterham - an even smaller, lighter, narrower car but that really did have an issue spinning up the inside rear coming out of slow corners and that was with an LSD. I fitted a much more heavy duty and expensive Titan diff and it fixed it without much understeer penalty. It was mainly on tight, 2nd gear left handers and mine is RHD so I sit on the right. Being 95kg I bet it would be better in LHD but again, putting the engine closer to the driven wheels is a better solution. Again, I'm very happy with the Exige as it is, still bone stock, still doing everything I want it to do and more.

Dave if you would 'have one in my V6 Cup an instant' why haven't you done it already out of interest?

[Seriouslylotus]

4 hours ago, The Pits said:

 

Dave if you would 'have one in my V6 Cup an instant' why haven't you done it already out of interest?

I tried and better tried to get Lotus to install a 400 gearbox during build.

The only reason I don't have a diff is purely cost. (In time and money). If ever the box is coming out, for any reason it will go back in with a plate diff. I do hope the 'internet expert' isn't aimed at me?

I am merely trying to  balance some of the other expert opinions that are being posted

Edited December 15, 2016 by Seriouslylotus

[MartynB]

Plate rather than ATB? An interesting choice. Having used both on a Caterham (very different beast, but with less natural understeer) I'd be erring on the ATB side for this application. I'd be interested to know why you'd err the other way

[GFWilliams]

4 hours ago, The Pits said:

no-one seems to complain about how McLarens handle using much the same principles

Yes they did. A lot. When the 12C first came out that was one of the biggest complaints about the car. They have no managed to sort the software to act like an LSD.

As someone who likes to slide a car about, I find the lack of an LSD very frustrating in the Exige. None of the electronic modes help you in this respect, they just cut power which is the last thing you want in this situation. Turn everything off and one wheel will spin, hence why I need a new rear right tyre.

[Seriouslylotus]

21 minutes ago, MartynB said:

Plate rather than ATB? An interesting choice. Having used both on a Caterham (very different beast, but with less natural understeer) I'd be erring on the ATB side for this application. I'd be interested to know why you'd err the other way

Being ex race driver I tend to ride the kerbs a bit!!!! An ATB only works when both tyres have contact with the road. I don't like the idea of a wheel spinning up and then suddenly having drive when the wheel touches down. Shock loads like that can kill gearboxes and drive shafts. If my car was purely road use the a diff isn't needed IMHO, or at most an ATB. (i.e. Like the Evora 400)

I also ran a plate diff in my S2 with a sequential,  zero issues and no understeer (once set up correctly)

A plate diff may be to much, however the Cup R with sequential uses a plate diff to great effect.........

Please don't take my opinions as being expert, either engineering or driving.  I just do things they way I think they should be done

Edited December 15, 2016 by Seriouslylotus

[MartynB]

Good answer 

I suspected the "ex racer" => "kerbs" angle. I think when we had the ATB, I was even less likely to take liberties on the rumble than I am now, and while I've become a little more aggressive with "track coverage", I'm still nowhere near racer level.

I did find the ATB to be buttery smooth, though I don't feel the Titan LSD we have now is too binary, which certainly was my worry when we had to change.

[alias23]

This whole LSD debate is great... I just want to do donuts lol

[The Pits]

No Dave, 'internet experts' was not aimed at you but rather the seemingly large number of people with questionable driving ability who continually slate the Exige's handling and place more faith in back street tuners than the people who engineered the car.

However I'm the only one questioning whether the Exige needs a diff instead of just going along with the general Pistonheads/what Chris Harris said/seloc hearsay. So it looks like your comment about balancing the 'tripe' others have posted was aimed at me which I don't much appreciate. If you think the Exige's handling is not up to your required standard and prefer it with a diff that's all well and good but don't pass it off as the absolute truth and dismiss anyone else's point of view as tripe. 

My bone stock Exige remains the best handling road car I've ever owned and by some way. That's just my experience, I have no agenda other than to share my honest experience. I genuinely can't relate to the big understeer story, nor the gearbox being crap or the need for an LSD or different geo or brake pads (and so on and so forth). I could pretend I do just for an easy life but I only come on here to share my honest experience. But sure, some random bloke on seloc said the car is complete crap so I guess it must be right!? Negative stuff is always easier to believe I guess.

If someone can tell me what they can do with their LSD equipped Exige that I can't do in mine, I'd be all ears.

[Crouchy]

Id just like to add that i have no idea what difference i diff makes in reality and therefore have no opinion either way

[The Pits]

7 hours ago, GFWilliams said:

Yes they did. A lot. When the 12C first came out that was one of the biggest complaints about the car. They have no managed to sort the software to act like an LSD.

As someone who likes to slide a car about, I find the lack of an LSD very frustrating in the Exige. None of the electronic modes help you in this respect, they just cut power which is the last thing you want in this situation. Turn everything off and one wheel will spin, hence why I need a new rear right tyre.

George I used the present tense in all fairness and I think the issues with the 12C were bigger than just the e-diff software. Regardless, McLaren have since proven that you can get a supercar to work without a mechanical diff. Even to Chris Harris's satisfaction. I've never driven one sadly so will have to take his word for it until I do.

The race mode in DPM doesn't 'just cut the power' either there's a whole in-depth article on it here. Not sure if your car has it but it's a very cutting-edge system even now. 'Sport' mode is a bit crude I grant you but 'Race' is very smooth and subtle. I don't think anyone has topped it yet.

[MartynB]

Seems fair to me Jonny. Having the Caterham in the same Garage as the Exige means that I can have both the low and high tech solutions and enjoy the differences. I'm in no hurry to change anything. Well, apart from the oil once I've finally had enough time to put 1K on the clock.

[The Pits]

It's ok, upgraditis is a big part of Lotus ownership for many, there's nothing wrong with that or tailoring the car to suit your taste that's every owners right, but I think it's taking it too far to start slating the standard car which has become the fashionable thing to do.

I hope at least that it's clear to anyone interested in this debate that it isn't as simple as chucking an LSD on and everything is sorted. Things like diffs are also set up to personal taste, there is no black and white answer it's a more complex area than I think some people realise. Look at F1 drivers, there is no one set-up that suits everyone. Some find other their team-mates sets-ups undriveable and they have diffs that can be adjusted several times a lap! I don't think an LSD is the magic bullet for the Exige but I have nothing against them, I wouldn't want to race my Caterham without a Titan diff, so maybe there is a diff that would work well in an Exige, I'm not for one minute ruling that out. The issue is the time and expense of finding one that works and how you get it working with all the other systems on the car. I take the view that the car works really well without a diff so it's messing around at great expense for potentially little gain along with the risk that you could actually make the car worse!

Dave clearly knows what he wants and has the time, skills and experience to get achieve that. The rest of us have to put a lot of faith in people who are fitting it.

I've found over six seconds around Goodwood just by chipping away with the help of free driver instruction. It's probably nearer 10 seconds since my first trackday there. I'd love to see a diff that could offer that sort of gain! Better still, I know there's more to come from the car because I've been over a second faster while sat in the passenger seat! I know it's a bit of a boring approach compared to writing a big cheque to Komotec but my plan is to leave upgrading the car until I feel I've got the most out of it as standard. Still a way to go yet. I did it the other way around with the Caterham, just kept upgrading the car to go faster and kept same old slow-ass driving style. I'd be lapping faster now if I'd worked harder at getting more out of it when it was standard. I'll wager Tom's learned more about extracting speed from a Caterham in one season of Academy racing than I ever did in 10 years of trackdays in a high powered 7. I know, I know 

[NW76]

Jonny, you are a wise man - very well put ...

I did exactly the same before I did any upgrades to my car when I started doing track days ... book coaching sessions and tune my driving style ... I set a goal of chipping away 10s on my home track before going the upgrade route ... and I do not regret having done that ... learning was much easier with the standard car that it is now ... 

 

 

[C8RKH]

Nowhere near the same performance league as you guys and the V6 but I'm heartened by the approach and advice here by you guys ( @The Pits and @NW76 ).

I've recently bought a fairly stock VX220, a nice clean and well sorted car to use on the track mostly and the only "mods" I am looking at are decent wheels & tyres, improved new track rod end/tie thingies (as they can break on the track..) and stuff like a harness bar etc.  So yes it will be modded, but not really modded for more power - reliability yes, power no.  My approach is very much going to be along the "coaching" route at track days and through 1-2-1 training to ensure that I become the the best driver I can be first and lose the bad habits etc (but not the vices, the vices are what make life so great!).  The power can come later.

It's a bit like deciding you want to learn to play the violin and going out and splashing a huge wedge by buying a Stradivarius to practice on! Surely you learn to play well first, then "upgrade" to the power of the Stradivarius.

[alias23]

2 hours ago, NW76 said:

before I did any upgrades to my car when I started doing track days ... book coaching sessions and tune my driving style ... I set a goal of chipping away 10s on my home track before going the upgrade route ... 

I had read that previously... It was a cool idea and nice target - reward. Out of interest how did you know what time to target? Had a Lotus Cup event happened at your track and you took times from those competing and made an educated judgement of what 'good' would look like as a time?

[NW76]

My coach helped me set the target - I asked him what a pretty good amateur driver should be able to achieve on that track with my car after he drove it.

And the target was within 2 seconds of what he does there in a 911 GT3.

 

 

 

[GFWilliams]

On 12/15/2016 at 21:18, The Pits said:

George I used the present tense in all fairness and I think the issues with the 12C were bigger than just the e-diff software. Regardless, McLaren have since proven that you can get a supercar to work without a mechanical diff. Even to Chris Harris's satisfaction. I've never driven one sadly so will have to take his word for it until I do.

The race mode in DPM doesn't 'just cut the power' either there's a whole in-depth article on it here. Not sure if your car has it but it's a very cutting-edge system even now. 'Sport' mode is a bit crude I grant you but 'Race' is very smooth and subtle. I don't think anyone has topped it yet.

I drive in either race mode or with everything off in my car when I'm pressing on. DPM does cut power, I can very clearly feel it and don't need to read an article to tell me otherwise?  Maybe on track things are different, but on the road it just cuts you when the wheels are about to spin (in slippy conditions).

I drive a lot of more exotic cars with work and can say that Ferraris systems are superior to the Lotus (458 Speciale and 488, not so much 458 which I'd probably put on a par with the Exige).  I've driven these hard on both mountain roads and track so got to have a good feel. The side slip control in the new 488 is just incredible.

I haven't had as much seat time in the new McLarens so hard to draw a conclusion from personal experience, but from what I gather from speaking to owners, the 675LT has a very different calibration to the 12C and 650S before it. This is one of the big reasons it's getting great reviews and McLaren have managed to mimic the effect of a LSD using software. Lotus have done no such thing, I'd challenge you to powerslide in an Exige with the systems on. It's only possible with everything off which is when the diff acts as a totally open diff.

991 Porsche GT3RS is quite an intrusive system, not a big fan and it was more enjoyable with it off on track.

Of course, I own an Exige so have no reason to say anything negative about it, but the reality in my experience is that the systems on other cars are better. More fun to turn everything off anyway and of course I am probably a different kind of driver to most as I'm not that fussed about lap times and prefer to have fun with a bit of sideways fun which is why I take my Caterham on track.  ps. either your Exige is setup better than mine or your Caterham is worse, but IMO the Caterham handles miles better unless it's a fast corner where the lift of the Caterham has a negative effect.

[The Pits]

Challenge accepted. Perhaps you should have watched the DPM video first.

Yes you have to turn everything off to get the Exige sliding into angles that would probably not end well on the road, that is the whole point of any stability control system.

DPM doesn't just cut the power, in race mode it uses a feedback loop to vary the torque threshold depending on the grip available. Yes Ferrari are said to have very good electronics but very few systems even today can do what race mode does - being adaptive to different track surfaces, conditions and tyre compounds. It makes individual use of the brakes to act like a diff which is similar to the McLaren system too. But the idea of race mode is to minimise sliding for a neat, tidy fast lap. Sport mode allows more slip but is more crude in that it does 'just cut the power' with a nice big delay before the power comes back in with a big surge. This is more similar to your usual TC system, the only real differences being the amount of slip allowed and the point at which power is re-introduced. 

If you're into sliding your Exige about I'd say it's still in your interests to read the only in-depth article about DPM on the web that was written with the help of the guy who has been developing the system at the factory.

I'm not sure what you hope to gain by not reading up about your car but each to their own on that. But I don't think there are many people who haven't read the article who know how to get race mode working properly. I know I hadn't until the DPM day at Hethel and I'd done at least 10 track days with it on prior to that.