Can anyone give me any information and advice on what settings i should go for on a plate LSD (ramp angle and preload). The car is FWD and when running full boost will have 500bhp. Not bothered how it drives day to day as its no longer that sort of car.

 

Power wouldn't necessarily come into the equation for ramp angle selection, I would assume its a track car?

on a track car i'd go 60'/90' ramp angles...

 

500bhp and front wheel drive that will be very interesting to drive

 

Thats part of the problem at the moment, which he is blaming the quaiffe ATB he has at the moment for causing, rather than blaming the 400bhp or so he already has, lol

 

Mark attributed some of the interesting handling characteristics to be down to the atb diff thats in it.

 

and the rest of the problem down too the fucking massive hp

 

Rick, I would stay well clear of a plate LSD if I was you, Turbo-Gav ran a Quaife in his with 400hp and it was no problem keeping it in a straight line.

He drove Bux's Corsa which has identical power but a plate type lsd and he said it was hardwork.

Basically whatever your problem is a plate lsd wont improve it at all IMO

IMO that much torque and a plate lsd is not the way forward, I think their more suited a to NA applications in fwd really unless it is a all out drag car then maybe it would be suitable.

Have you got your geometry done yet ? the red nova is having it done now as it drives as you desribe and I know from using a ATB on several cars thats not what is at fault

 

the only way a 500bhp fwd car will not suffer from torque steer is to drive it in reverse

 

 

With 500hp the geometry is going to need to be perfect before you start looking elsewhere on the car for reasons for instant ditchfinding on boost

 

with that much power through the steered wheels it will make it's own geometry as the shell twists

 

Thats fair enough but as the geometry hasn't beeen set yet iirc I can't honestly see how you can blame a LSD or anything else for the troubles.

I'm currently trying to run in a 230hp xe nova at the moment and although the geomerty "looked" ok it drives so bad I've sent it in to have it done as we speak before I do ay more running in miles.

Fook knows what it must be like with that much torque but it cant honestly be anymore powerfull (currently) than my mates old one on gas and that literally was straight as I die which tells me something is wrong.

 

hi Ian ,
i think it would be great if you could explain your thinking behind those ramps , especially the quick drop off from the 90 Degree "out " .
it should also be said that different circuits require vastly different diff settings for Fast/slow corner entry /exits and that a compromise setting tends to be the same "in " as it is "out " .
Cheers
tony

 

very odd with 400 bhp and alot of TQ because of the nitrous mine used to have no problem accelerating in a straight line and was not hard work at all.

so tis all down to the set-up imo

 

Tony,

Obviously pal I dont have the experience you have with circuits, I based my selection on it being high powered vehicle, on tarmac and FWD, having the diff actuated severely (eg 30/30) would IMO promote poor control into a corner and understeer out of the corner, nearly free coming in (90' off power) would give you adequate control until the apex then smooth delivery (60' on power) out….on the rear of mine I run a 30/30 for gravel and 45/90 for tar......

Ian

 

i wouldnt have a clue how to guess the ramp angles

 

I don't know if it helps but quickest circut racers that are FWD run plated diffs and lots of preload on them. But the quickest motorsport FWD car I know has about 300-320bhp

 

the lower the 1st number is how much of a climb the bevel gear in the diff has to make before it reaches a point of 'lock' as we will call it. so if the ramp angle is 30deg then it will be able to climb the 30 deg slope with ease at any slight speed differance between the wheels that diff is placed. so even at moderate power under cornering with a 30deg ramp the diff will try to ramp up to promote 'lock' thus resulting in over steer once locked.
a larger ramp angle 60deg would allow more progressive ramp up before locking the wheels together.
inbetween all this you also have pre-load set on the diff, this will add to the pressure on the bevel gear so that ressistance is given between the plates allowing the diff to 'slip' before we start to ramp up.

the 2nd number i.e 90deg, is the ramp down angle, so you under full chat, cornering the diff locks, you understeer into oblivioin because your grip has reduced (surface change or what ever) then you lift off the power progressivley, a large number here will allow the diff to unlock very quickly giving you back you preloaded diff rate of progressive slip.
a lower number here will not let the diff ramp down untill you have completely dropped power as the length of the ramp being a lower number is also a longer area to ramp down

hope this makes sense ?

Ian, you would just turn the fookin dial job done

 

I will leave the ATB in for now then and setup the camber, caster and toe better and work from there.

 

the quickest circuit racers run combination diffs , plated and Viscous units that work together ! At 300-340 bhp the super tourers have massive grip and loads of turn in but im used to seeing much lower ramp angles, in particular the "out "angle as a larger drop means the diff acts very quickly and not progressively , thats why i asked Ians thinking , thanks for the answer chap .

 

Tony Ryan the problem is I get to talk to the drivers more then engineers and they always tel bullshit "I have 90% locked diff in my Clio". What the hell does that mean?

 

Tony,

The out angle, is 60' not 90....it would be 90 in, on the de-acceleration. 60' on accelleration out of the corner.....the diff would exhibit light locking under power on and totally free or "Open" under power off...the reason i'd choose this would be for a less experienced driver on tar, to make the car reasonably safe, i'd agree, that with a more experienced race driver the ramp angles would reduce as he/she would be pushing the car further.....

I dont think the guy who asked the question is an hardened racer and if he is I do apologise.....30/30 ramp angles in any car would make the diff very aggressive....

Ian

p.s. thanks mark for the more detailed explanation, put more elequently than I could ever have written....