Sam@TDi

Absolutely correct, in fact it's near impossible to model accurately even if you are privy to all the required information. It's for that reason that you'll find tyre testing rigs at all of the tyre manufacturers research bases, whats more tyre testing rigs are being carted about by all the top NASCAR, F1, ALMS teams etc. The chassis engineers simply test the tyres on a simulated appropriate surface and then map out the force responses in the form of an industry standard carpet graph, they map out the tyre as completely as possible, THEN they decide how best to exploit the tyre to achieve their goals. Working without accurate tyre data necessitates extensive real world experience (and/or data) with the tyre, or at least tyres of similar design and chemistry. If you find yourself with neither accurate tyre data or any real world experience with the tyre then you'll find you need a great deal of luck.

Sagitar that's spot on, as usual As Sagitar has eluded to, the chemical make up of the tyre is a huge variable determining the exact exchange mechanisms by which "grip" is generated, and without factoring it in whilst you're thinking you can't really work with this subject.

you'd be right in thinking that, it's impossible to change one aspect without influencing the rest to some degree

Ok I understand, the science related to this transient situation is just about as complex as chassis dynamics ever gets! The variables effecting the eventual perfect solution fall in to the fields of geometry, weight distribution, sprung vs unsprung mass ratio, force transfers pathways, roll centres, specific tyre dynamics, net roll resistance (springs plus arb's), low speed compression damping forces and chassis preload. In short the answer to the "to squat or not to squat" question is the motorsport holy grail, I've got my own opinions on the subject as have other chassis dynamisist's and the one thing we've got in common is that we've all come up with different conclusions

I'm not understanding "squat corner out" Tony can you describe what you mean?

No probs ..... but hey 11sec's to 100mph is serious stuff no matter which way you look at it

MR2 turbo's punch well above there weight off the line, in Japan they're often forced to race with the 4wd classes at the drag strip

http://www.youtube.com/watch?v=G5oFCpIW_ds

You would be correct

Yes you absolutely could but the level of heat energy involved would soon heat the ceramic and you'd be back to radiating heat, the simplest way to address the issue is to isolate the turbo and heavily lag sensitive components in the proximity. We use a special Goodrich lagging that is designed to protect wiring in foundry machines from molten metal strikes it cost's around £60per meter

Indeed welcome to WIM Personally I've found it extremely difficult to gain access to good quality scientific information on the subject of vehicle dynamics. I'm my opinion the academic land scape in this field is clogged with authors offering their opinions often passing them off as fact or worse still preaching as an expert based solely on their own trail and error experience without any real understanding of the true mechanisms at play. I would recommend that you cast a skeptical eye over as much material as possible, then perhaps mentally attempt to sort the wheat from the worryingly large amount of chaff. I've been lucky enough to work with some talented people in this area and I've certainly gleaned far more from my discussions with these people then from any of the books I've ever read on the subject.

Properly and completely

Wizard of Nos equipment works extremely well even if they don't look like the most flashy, direct port is ALWAYS better for even nitrous distribution than a single injector but it's around double the price for the hardware and almost four times the work to fit. I would recommend a single injector if you planning a power hike up to 50bhp, over 50bhp then it's worth thinking about direct port. I would also heavily recommend a bottle pressure gauge, fuel pressure gauge and if the budgets there a progressive controller.

Ok, Honda's vtec system uses completely different cam lobes pre and post the change over point, that is pretty unique and was actually patented by Honda for a long time. The intake cam advance and retard function that puts the "I" in "IVTEC" is a tuners dream, it can advance or retard the cam +/- 25deg so that's 50deg of overall swing! it can reposition the cam at a typical rate of 10deg per 10msec which is fantastically fast. Mapping the the H' B' and K' series Honda engines accurately is as you say very tricky but for reasons that go way beyond the control and subsequent dynamic influence of the cam shaft control systems, these engines are unique in many ways, personally I absolutely love working with them

I prefer regular compressed air and wd-40, and a good ultra high pressure PTFE joint to start with.

Well flowing across the cylinder heads that way around isn't all that new i've seen it on quite a few historic racing engines from the 50's and 60's but it does make alot of sense to mount the turbos inside the V, it ultimately will mean that the engine is much narrower and will give the suspension designers much more freedom to use long arms and therefore have better dynamics. Interesting to see petrol direct injection as well, but with the impending Euro 5 emissions regs I'm not surprised.

Perhaps someone should design one with variable length - a section a bit like a trombone slide maybe - and a linear motor so it could be adjusted while driving. Then you could make it play whatever note you liked . . . . . . . . A Happy New Year Sam. And a Happy new year to you Variable length exhaust runner designs have been around almost as long as the internal combustion engine. Often for road cars it's easier to tune the exhaust so that neither peak negative or positive harmonics are in the engines frequency range. Intake harmonics are even more important, variable length intakes runners are used to great effect in loads and loads of modern cars, probably best demonstrated in the Audi 4.2 V8 which boasts 80% of peak torque available from just 2000rpm. Thanks in no small part to it's 3stage variable length intake manifold design. Regarding the MX5 exhaust there is too little information here to make any kind of informed decision so it'll be a "suck it and see" I'm afraid

Well your barking up the right tree as the softer coils will need slightly more compression damping and slightly less rebound damping. But I wouldn't suggest you start just tweaking randomly hoping to pick up a difference because the feed back you'll get from most drivers won't be anywhere near reliable enough to use for this type of work. The only way to know for sure would be to remove the springs and have the spring rates accurately measured. Or perhaps just suggest to the customer that they purchase a better suspension kit, one with reliable coil springs and a mechanical ride height adjustment. Although to be frank I doubt your drivers will really notice anything particularly negative about the current suspension set-up. Unless their lap times are regularly consistent down to within couple of tenth's then I wouldn't worry to much about this level of accuracy.

Cool ok your right the Lotus Elise is very evenly balanced but still not perfect. So I'd guess the differences in the positions of the lower spring platform come from poor tolerances in the original spring strengths and the slight imbalances of the chassis. Yes this will effect the way the sprung and the un-sprung masses interact with one another and therefore it will effect the dynamic movement and subsequent weight transfer. Personally I don't like adjusting ride heights by adjusting springs pre-load (which is exactly what you were doing) I prefer to adjust it by mechanical means and leave the pre-load on my springs even all the way around the car unless otherwise called for by the set-up. All Penske, and most high end Ohlins and Tein coilover suspension units have separate adjustment for ride height independently of spring pre-load. And for a competition car, serious road/track application I would always suggest double checking that all of your coils are of the correct strength before you fit them and it's not a bad idea to monitor them throughout the season.

Ok I think to start with you need to be a bit more specific about the method used to "set the coils" .... are you setting the ride heights level on a car with uneven weight distribution?... or are you setting up a perfectly balanced car with poor quality coil springs that just happened to have all come out of the box with differing spring strengths?... or have you deliberately manipulated the ride heights to influence weight distribution at the contact patches?

I definitely haven't I just skimmed over the main chapters. The frustrating thing is that as I was trying to simply summarize these difficult subjects the natural tendency of the journalist was to ask what he thought were simple questions that in fact required in depth understanding of some complicated sub-subjects to explain properly, but we got there in the end. I think he filled up one and a half 90min audio tapes over a 4hr period He told me he'd send me the article to proof before it goes to print so it'll be interesting to see how it's written.

Hi guys sorry I've only just seen this thread. Ok firstly four stroke engines do not need or want any back pressure, at all, full stop. The best possible exhaust for a four stroke is a straight piece of pipe of the "correct length and diameter".... the reason that the length and diameter are so important is because it's actually the harmonic characteristic's of a four stroke exhaust are of the utmost importance. Arbitrarily removing boxes, changing pipe diameters will always have hit and miss results and I can count the people that I know of with the required knowledge to properly design an exhaust system on one hand. It's a bit of a black art (read- Complicated Science) I'm afraid

I think that's a sounds plan, the chassis dynamics rabbit hole certainly does go very deep

I think your getting very close to seeing the entire picture in the area of DI, Static and Kinematic Geometry. When your totally comfortable with these major first chapters we should then start discussing dynamic weight and force transfer

The DI being 1.00 is definitely desirable but don't do your self out of too much credit here as it's only a portion of the picture. The caster angle, static camber and toe will make a more immediate difference to the chassis than the DI.