Activa quirk?

Toby_HDi · Unread post by **Toby_HDi** » 24 Feb 2010, 17:36

Just wondering if any of you fellow Activa owners have noticed this or if it's just my driving.

Coming off a roundabout or turning into another road, and applying power quite firmly I seem to get the inside wheel spinning up.

What causes this or is it just me not feeding the power in progressively enough?

Xaccers · Unread post by **Xaccers** » 24 Feb 2010, 17:40

floor it hard enough and they'll wheelspin in 3rd, sometimes even 4th

XantiaMan · Unread post by **XantiaMan** » 24 Feb 2010, 17:54

I would expect it in 2nd, and sometimes 3rd, but if your getting it in 4th your tyres must be s**t, i cannot remember getting 4th gear spin in brisk driving. Its quite normal for a torquey engine and fwd chassis to do as one of the tyres has less contact than the other as weight gets pushed against the outside tyre.

Toby_HDi · Unread post by **Toby_HDi** » 24 Feb 2010, 18:04

Hadn't thought of tyres.

They are all getting close to needing replacement. Not only that, there is a mismatch on there at the moment so will be replacing with matched W rated tyres.

Suppose an LSD would help too

XantiaMan · Unread post by **XantiaMan** » 24 Feb 2010, 18:06

Toby_HDi wrote:Hadn't thought of tyres.

They are all getting close to needing replacement. Not only that, there is a mismatch on there at the moment so will be replacing with matched W rated tyres.

Suppose an LSD would help too

Yes, definatly an LSD would help, but tbh torque steer isnt too bad thanks to the 'equal' length driveshafts. New tyres will make a massive difference. I remember when my old Nokian tyres were close to the limit and it was a nightmare to drive in the wet, 3rd gear wheelspin no problem in a straight line.

Toby_HDi · Unread post by **Toby_HDi** » 24 Feb 2010, 18:17

I wondered why there was a lack of torque steer with it.

The Alfa used to torque steer like crazy if you gave it the beans and caught it wrong.

Unread post by **Dommo** » 24 Feb 2010, 18:19

The open diff is a big cause of spinning up the inside wheel, open diffs are daft when it comes to driving quickly as they send all the power to the wheel with least grip. An open diff is more a safety thing really, makes driving a bit more foolproof.

Koukku · Unread post by **Koukku** » 23 Mar 2010, 06:12

I've never driven an FWD with LSD diff, but from what I hear it can be a bit twitchy... but I'd still put one in my Activa if such a thing was available for the ML5T box. 225mm wide trackday tyres help a lot, but wheelspin out of corners is still a big problem in 2nd gear.

ACTIVE8 · Unread post by **ACTIVE8** » 28 Mar 2010, 10:34

Koukku wrote:I've never driven an FWD with LSD diff, but from what I hear it can be a bit twitchy... but I'd still put one in my Activa if such a thing was available for the ML5T box. 225mm wide trackday tyres help a lot, but wheelspin out of corners is still a big problem in 2nd gear.

Yes, but unlike us, you have a V6 Activa!

citrov6 · Unread post by **citrov6** » 28 Mar 2010, 10:55

XantiaMan wrote:I would expect it in 2nd, and sometimes 3rd, but if your getting it in 4th your tyres must be s**t, i cannot remember getting 4th gear spin in brisk driving. Its quite normal for a torquey engine and fwd chassis to do as one of the tyres has less contact than the other as weight gets pushed against the outside tyre.

thats one area I thought the activa was significantly different?

XantiaMan · Unread post by **XantiaMan** » 28 Mar 2010, 18:10

citrov6 wrote:
XantiaMan wrote:I would expect it in 2nd, and sometimes 3rd, but if your getting it in 4th your tyres must be s**t, i cannot remember getting 4th gear spin in brisk driving. Its quite normal for a torquey engine and fwd chassis to do as one of the tyres has less contact than the other as weight gets pushed against the outside tyre.
thats one area I thought the activa was significantly different?

The weight of the car has to go somewhere, going fast round a right hand corner will load up the NS tyres more than the OS, so you will still get wheelspin.

Bear in mind that the CT does have a reasonable amount of torque and isnt far off the V6 (171lb ft CT, 197 lb ft V6). It also produces its torque lower down the rev range, its worse when they are tweaked and easily producing more than 200lb ft. I would expect the smoother power delivery of the V6 makes it harder to get sudden wheelspin, where as a tweaked turbocharged car the power comes all at once.

citrov6 · Unread post by **citrov6** » 31 Mar 2010, 04:00

v6 auto's never spin unless the tyres are cold, I think the weight of the v6 puts a lot of downward force on them to. It is far smoother than a 4 cylinder doesn't really give it the opportunity to lose traction like that, and on every gear change it retards the ignition, can't imagine how long the box's would last otherwise.

He must be taking those corners hard to unsettle an activa like that, there should be in theory anyway minimal weight shifting. Nice to know 10-15 years on activas are still being enjoyed like that though

Koukku · Unread post by **Koukku** » 31 Mar 2010, 06:50

I would think that the automatic smooths things quite a bit. And it's true that the V6 delivers the power in a more civilized manner than a tweaked TCT. But the V6 does have a little kick around 3500rpm, and mine currently produces 270Nm (~200lb ft) @2000rpm and goes up from there...

The Activa system does not actually affect the amount of weight transfer, it is affected by the weight and center of gravity of the car. Suspension can only control the speed of the weight transfer (apart from suspension height which of course affects CoG). Stiffer suspension means faster weight transfer, which means more precise handling and faster steering response; the car changes direction faster and gives the driver a better control of the car. And that's what an Activa does while cornering.

In a "normal" steel sprung car the same effect can only be achieved with a very, very stiff suspension.

And of course there is the added Activa bonus of all four tyres being flat on the ground at all times, which gives optimal grip while cornering. But still the inside wheel is way less loaded, and thus prone to spin...

citrov6 · Unread post by **citrov6** » 31 Mar 2010, 21:18

Steel sprung cars are rubbish, the worst part is that resistance of the material it doesn't respond accurately to bumps and starts an uncomfortable oscillation.

Well in theory if there was such a car that wouldn't tilt at all in cornering you would not get weight transfer. Like bikers lean into corners they use weight transfer. Perhaps the road camber change of that round about was particularly bad, I don't know how the activa adjusts for that. All I know is it stops it leaning, which could just be the height of the body relative the wheels?

The v6 does give a kick when it starts using all 24 valves, auto is particularly noticeable if you get to use 3rd gear at all.

Koukku · Unread post by **Koukku** » 01 Apr 2010, 08:00

citrov6 wrote: Well in theory if there was such a car that wouldn't tilt at all in cornering you would not get weight transfer.

Nope. You could replace springs/shocks with solid iron bars, get zero tilt, and still you would get weight transfer. It would be instant though. Springs always delay the effect.

More on the subject:
http://www.miata.net/sport/Physics/

The v6 does give a kick when it starts using all 24 valves, auto is particularly noticeable if you get to use 3rd gear at all.

All valves are used at all times, there's no variable valve timing in the ES9J4. The kick is probably the result of the two chamber intake manifold. It acts a bit like a variable length intake manifold, but without any moving parts.