aerodynamics

[kevtherev]

Ive checked and the packer is there already

you could fit a thicker one...

[Fin]

Or double up

[boxer]

I'll see what we can do.

[ricicles]

My camper used to be appalling on a motorway, it would wander around all over the show! I had the tracking checked and adjusted on a fancy do dah with tv screens to show it was correct after that it drove the same, a year or so later I was at mid Norfolk motor co and Paul did the tracking properly, when it had been done by sts they had not centered the steering and adjusted it on one control arm because the other was seized solid. The difference was incredible. I have since added Polly bushes to the steering rack and that gives a better feel to the steering, also worth checking the dampers, if they need replacing that will have an effect on the steering. Ps if you buy new dampers I would not recommend avo ones just because I have to send mine back every year for new seals, according to the guys at avo they stick when left parked for a while so prob not ideal for a camper that is not used on a daily basis.

[faggie]

i had problems to with avo shocks and springs they did not seem very good quality, springs sagging and dampers leaking in the end i replaced with h/r springs and bilstein dampers loads better quality and ride

[HarryMann]

Seems these graphs might be relevant to this subject Ian, amazing what's in the Wiki





Derivation of the nominal drag curves used above, from various engjne power and speed sources



Could say a lot more on this subject of course a lot of previous and relevant discussion is in the Archive already

[silverbullet]

when it had been done by sts they had not centered the steering and adjusted it on one control arm because the other was seized solid. The difference was incredible.

Having the track rod arms set to different lengths wouldn't help at all. Found the very same on one of mine, no excuse for it as they both loosened off easily. The difference was more than a few mm too...

Clive, I didn't start this discussion! Will delve into the Wiki at an opportune moment

PS the power vs speed graph looks bang on, as the 2.6 SA would officially just do the ton with 130 bhp available @ 5k rpm

I suspect that the most interesting thing for folks is how drag increases over the 50-60-70 mph increments and what that means for fuel consumption.

PS While I think of it, vaguely on-topic, I had a flick through our 2002 KS valves/heads catalogue and found this VW petrol engine curiosity:

DG, DJ, MV i.e. all later wbx, inlet ~40mm, exh ~33mm. Stems 8 and 9mm respectively.

ADY inline 4, valve sizes exactly the same but with 8mm stems for both, 7mm later on...

(DJ made 112 bhp @ 4800, 160 Nm @ 2800. 10.5:1 + digipants. mid-20's mpg in a ~1500 kg 7-seater. Only the Carat was heavier at 1730kg)

(ADY 115 bhp / 85 kw @ 5000 but 170 Nm @ 2400. 10.3:1 + SIMOS sequential. High 30's mpg in a much heavier 1800 kg 7-seater.)

I have got 38-39 mpg out of our Sharan keeping it 60-65 on the m.way so clearly aerodynamics/smaller frontal area count for a fair bit, along with full lambda engine control and sensible 195/65/15 tyres. But it does also have an engine undertray extending back from the 60mm deep front spoiler, small door mirrors, hidden wipers... i.e it all adds up.

PPS What are the purpose of those mudflap-sized deflectors that can be seen on some cars, a short distance in front of the rear wheels? SAAB 900's first had them IIRC, I have seen them on Disco 2's and some newer soft-roaders too.

[HarryMann]

... but you are trying your best to keep it on track Ian

[Fin]

Those graphs would explain why, even with 248bhp under my foot I can only squeeze 120 out of mine then..
The air resistance at that speed (on the graph, must be a vertical line upwards)

Think I saw something on it during the Veyron stuff on Top Gear, saying they needed almost double the power to make it go only a little faster can't remember the actual figures
http://www.topgear.com/uk/videos/veyron ... esNumber=9" onclick="window.open(this.href);return false;

[Fin]

I got that wrong -
It needs 270bhp to do 155mph, then it needs another 730bhp to do 100mph on top of that

I know it's not in the league of our pottering about - but it does explain why mine just kinda stops....
as does the big 5 sportline I've got

[Fin]

So by that reconing - I'd need a good 300bhp to make it rev out on the current gearbox, that's good for (in theory) 144mph

[RacerADS]

PPS What are the purpose of those mudflap-sized deflectors that can be seen on some cars, a short distance in front of the rear wheels? SAAB 900's first had them IIRC, I have seen them on Disco 2's and some newer soft-roaders too.

I asked that very same question to a guy on an MR2 forum who put them on his endurance racer.

Apparently they stop vague high speed handling by disrupting the airflow around the wheel.

[faggie]

peter williams claims he has seen 156 mph in his with his old engine

[HarryMann]

Like I say, it's basically a square law, so if you want it extrapolating to 156 mph, just ask.
Who is Peter Williams, should we know him and how much power is at his wheels?

[HarryMann]

Front corner cascades on trucks. ..

We had a discussion on those on here years ago. Geoff (crazy diamond) & others assured us they were indeed originally fitted to keep the side windows clean.
Since then I suggested that they have been adopted more widely to reduce cross-wind drag and increase c-w stability as well.