Sam@TDi

Extending the wheel base by 20mm would lower the DI. The MX5 is from memory very close to 1.00 as it sits without driver but with a 75kg driver the DI will shoot up to around 1.10 so adding the wheelbase will edge you slightly back towards 1.00 ... If i take an average car weight with a DI of 1.00 thanks to it's wheelbase then added 20mm to the wheelbase the resulting DI would edge down to 0.97

Good series of questions Regarding the manipulation of the corner weights purely by adjusting the static geometry, I've never measured the effects but I would expect them to be negligible. Changing the wheel base by adjusting the static geometry is more likely to be useful as a tuning technique, however normally speaking a movement of 5mm or more would be necessary to produce a measurable change in the handling. Now spring rates, there's more to a spring rate than just keeping the chassis off of the floor. In simple terms the car is made up of two major sections - an unsprung mass and a sprung mass, both normally are in motion. The springs and the dampers form the primary link between these two masses and control the way forces that are present in one mass are passed onto the other. The science of Harmonics plays a massive part in calculating the correct spring rates and it's easy to get this part very wrong. I personally wouldn't specifically modify spring or damping rates in reaction to an imbalanced chassis, especially not across an axle. But as far as I'm concerned it's perfectly logical to set the ride heights so that the chassis is even when loaded in the way that it will eventually be used. This ensures not only accurate static geometry but also even progression of kinematic geometry, this in-turn makes the chassis more predictable and easier to both drive and tune.

One of the problems with the field of chassis dynamics is that it's often not clear what people actually mean by the terms they are using so it's always prudent to ask them to explain what they mean. If we assume that they use the term pre-load in the same way I do then it's the amount of positive compression exerted on the spring whilst the suspension unit is unloaded (ie off the car) .... for instance Tein recommend that you pre-load all of their coilovers by 5mm when you initially fit them, if you then wanted to you would adjust from there.

I agree Tony, please don't get me wrong I think your absolutely barking up the right tree here

I think that Kaspar was pointing out that the toe in on bump characteristic from my bump steer mod is doing the same thing as positive ackermann, basically producing an artificially high amount of slip angle on the out side front wheel. The main reason that the F1 cars employ positive Ackerman is because they have zero body roll (in order for the aero to work) and therefore can't take advantage of the kinematic geometry changes that body roll can bring with it.

I want to know what the hell that foldaway chair's made of

Way ahead of you

Hey Kaspar how the devil are you? picture's look superb mate. Looks like you've got the hang of gliding that Z33 around

Only just seen this thread, that D1SCO plate belongs to a good friend of our family called Jan, she's the financial director of the company that owns Dukes night club in Chelmsford and Bonds night club in Southend. It's on a Porsche now but used to be on a Land rover Discovery which was doubly apt

Yep we're actually agreeing here I think, you say that your saturating the rear axle first.... which is the stiffer on your car by the sounds of it.

Yep I would advise you do just that, KW are a good company and their kits are properly researched, the advised settings will most likely be a great starting point.

The answer to this is a resounding yes, but do bare in mind that even a set of adjustable dampers for an EVO for instance will need different damping response curves and different damping rate ranges to an adjustable damper designed for an M5

Hi Tony & All, my first post here... I have Koni "yellow" adjustable dampers on the front of my bmw, and Bilstein Sports on the rear, so I might be entitled to an opinion on this one. The Konis are great, and I run them on just a hair (16th of a turn) more than full soft for daily driving. They are still very firm and much harder than stock, but not uncomfortable. The Bilsteins are harder still, actually a bit too stiff for the roads, but do their job well. I chose the koni/bilstein combination with the theory that you want stiffer in the rear so as not to introduce understeer in what was a perfectly neutral handling car, and then could balance it by adjusting the fronts. I'm hoping to buy myself some adjustable rear konis for xmas... So if I were to go on a track day, or to the Nurburgring maybe, one of these days when the car and me are ready (I don't want to trash it yet), I can crank up those konis and have all of the benefit of sport dampers, but still be able to live with it day to day. Adjustable is good I would agree with tdi's remark that I am probably not qualified for any more than a "soft to firm" kind of setting, and given the chance and a perfect bit of tarmac would probably run full firm in the rear and softer in the front. Hi, interesting that you've found running the rear harder reduces push. Thats a pretty graphic illustration of how the true mechanisms behind chassis dynamics can be quite unintuitive and how tricky it can be to remain un-subjective as a driver. pbsdesign I can guarantee you that at the grip limit the stiffer of the two axles will saturate it's tires, drop grip and slide first. But right up until that point the stiffer axle will be the more responsive. Everything gets reversed at the grip limit.

I moved my track rod end pick up point 35mm, does that count

Well if we ignore that there is no easy way of quantifying actual damping forces for the moment and just look at the basic principals... The main aim of a vehicle suspension is to eliminate vertical force variations, unfortunately because we live in the real world all we can really do is limit the load force variations. Another main role of the suspension system is to communicate forces from the road wheel to the chassis these include the obvious and desirable tractive forces, lateral acceleration forces and braking forces... often other less desirable forces are accidentally transmitted like acoustic harmonics for instance. These two base roles are contradictory in their demands because for us to eliminate vertical force variations it must be possible for the road wheel to retreat away from any surface deformation with zero resistance. But this would mean having zero wheel inertia, zero spring rate, zero damping and infinite suspension travel. On the other hand for the job of transmitting forces from the wheel to the chassis we ideally want our suspension to be absolutely rigid and inflexible. It is this basic and fundamental contradiction that underlays all vehicle suspension development during which we try to find a "perfect" middle ground of suspension compliance and suspension rigidity... Damping is a significant part of this compromise.

Yep your correct on both counts, good spot on the 14.7 When I talk about thermal management please don't think I mean engine temperature. What I was getting at was the influence that rich afr's have on controlling the combustion process through it's initial slow burn phase. Which as you correctly point out is crucial to controlling the combustion speed and therefore keeping detonation at bay.

Ok this is a massive subject, in the Motorsport and OEM world right now damper development is an absolute hot bed of innovation and development. To answer the question simply, if you've got no information to work yet with just place all the adjusters in the middle and hope like hell the damper manufacturer new what they were doing when they developed these things, that is of course assuming the company involved did any development To explain why I give such a lame answer..... The biggest problem that most novices face when trying to understand dampers (shock absorbers) is that there are very few hard and fast rules and even fewer accurate mathematical formula. All we can say for sure about any given damper is that it'll give you some forces at some speeds (thats shaft speeds, not road speed) The force inside a damper is re-active, that is to say to acts against an opposing force, normally the force is generated by using oil or gas trapped in a chamber and slowing allowing it to bleed away. These systems are sensitive to two main variables Shaft speed Tempreture Most dampers have a fixed relationship between compression and re-bound damping and all that is really adjustable by the end user is volume of the overall damping. I personally prefer these dampers for after market use but only as long as the compression/rebound damping relationship is correct out of the box and that is all down to the manufacturer carrying out sufficient pre-production development. Some dampers have separate adjustment for compression and rebound allowing you as the end user to define the relationship between the two damper modes. Think very carefully before using this type of damper. Are you qualified to adjust this damper? do you have the foggiest what your doing?... Manufacturers love supplying this type of damper because it means they don't have to develop the unit, so in reality that means DON'T USE THE MIDDLE OF THE DIAL THEORY! There are also 3 and 4ways dampers now available on the market, it will take me pages to explain these properly but suffice to say once set up they are excellent, and the main difference from a normal damper is that you have split damping rates for low and high shaft speeds. Like I said at the top this subject is huge and is changing everyday, everyone in the industry seems to have there own idea's as to how damping should be done. hope this helps a bit at least

Tony that is brilliant, a really good succinct list of definitions. Bit like a geometry dictionary. I followed you whilst reading this but I can imagine that to some who perhaps don't have an in depth knowledge of the terminology involved they might struggle to understand the meaning and context of some of these terms. What could really bring this to list to life in the future might be some nice clear diagrams, combined with these descriptions that could be excellent.

Here you go Adjustable rear toe control arms, IS200

Sorry Tony I hadn't seen this, I'd say your right in criticizing the data it doesn't look correct to me. I can't see anything too wrong with that set-up... maybe the customer regularly drives up lorry ruts?

Ok cool, well the rev up on your engine will never be as sharp as the Gallardo for a number of reasons. Static compression ratio is much lower on the 3s-gte and the engine relies on elevated intake manifold pressures to recover from and over come this deficit, but being a turbocharged set-up it's unlikely you'll make any meaningful manifold pressure whilst quickly revving the car. Turbo cars traditionally are fitted with heavier flywheels than their N/A counterparts because of the lack of low engine speed torque The Gallardo engine is physically a much larger unit and so will be simply able to apply more torque to the crankshaft at low engine speed. Because the Gallardo engine has 10cylinders each firing once per cycle the supply of torque to the crankshaft is far smoother and more continuous than a 4 cylinder engine, this reduces the need for a flywheel with much inertia which in effect enables the engine to maintain a low speed idle with a light flywheel If you use an overly light flywheel on your 3s-gte the idle will need to be high in order to be stable and the low speed operation whilst drive is engaged will feel quite week, and then as more throttle is applied the corresponding torque rise might feel more abrupt or "jerky" hope that helps

The Toda Racing flywheel for the 3S-GTE is 0.46 of the inertia of the standard, weighing in at just 4.5kg Ultimately it's worth remembering that engines have flywheels for a reason and reducing the flywheels effect more than is necessary can be counter productive. What problem are you trying to solve? or what characteristic are you trying to improve?

That looks like an aggressive hone, the only reason you would do that deliberately would be if you wanted reduce running in time i.e a racing engine that might only have the matter of a few laps in order for it to bed in.

To put it into the simplest terms engine management calibration is either correct or incorrect. An ECU containing a general factory calibration meant for a naturally aspirated engine will be totally Incorrect for any engine with is running with elevated intake manifold pressure (boost) The ability to control the calibration accurately is absolutely vital! infact it's so important that many racers and performance enthusiast's spend big money on increasingly complicated systems.

That is actually a good point, LSD effect across the axle is extremely desirable in high grip situations but only to a point, if that useful threshold is exceeded then the LSD can quickly become the enemy of grip causing an axle to break away. Violent and extreme 1.5way or 2way LSD settings are often employed in drifting to help deliberately agitate the rear axle, it's important to realize that this was never the original intended use of the LSD though, when set up correctly they increase stability not harm it.