PDA

View Full Version : Dallara LSD seting


lander
14-08-09, 12:54
Hallo
Can you help me?
I crashed my dallara F394 in high speed corner because i get slide of back.
My LSD wasnt set well. I use 60/80 ramps and 6 faces. And I think that it is absolutly wrong for hillclimbing. I am going to use only 2 faces. Will it be OK? Or how you have set your LSD in Hewland?

Thank you
Best Regards
Filip Zelensky

lander
16-08-09, 09:52
Nobody can help me? :-(
Filip

jo white
16-08-09, 11:38
Maybe its not your diff and possibly a suspension/damper/spring or tyre issue

lander
16-08-09, 11:53
In back I had 800 springs and Koni dampers, Tyres Dunlop 280/570/13

yobdab
16-08-09, 14:50
Filip

60/80 ramps with 6 faces is exactly what we use on a circuit car. Maybe the preload needs adjusting, should be about 15 ft/lbs. Also 800 lbs springs on the rear is normal for circuits.

So maybe for the hills it is all wrong. Most guys in the UK will change to a cam and pawl type dif and probably run 300 lb (ish) springs on the rear.


Nick.

lander
16-08-09, 15:28
Dallara F394 has standart for circuit 600 front and 1000 back. I am using 550 front 800 back.

In June there was one guy with F393 and he use 500 in front and 800 in back for hillclimbing. But he wasnt able to tell me what setting of LSD he use.

There was set the preload as described in Hewland manual, but during race it was less. Is it problem? But I think that 6 faces for high speed corners was too much lock.

Few ways how to solve my problem (because I think that it is problem only of LSD), in slow corners, high speed straights dallara was working good:

1) 60/80 ramps 2 faces
2) 80/80 ramps ? faces
3) another type of LSD, which someone has good experience in hillclimbing.

Filip

Radical
16-08-09, 17:06
I know you are concentrating on the LSD,but generally for hillclimbs (in the UK) most people run much softer springs with the appropriate damping especially to help in the slow corners.

lander
16-08-09, 17:12
I get setup of springs 600 in front and 900 in back from Swiss 2003 hillclimb champion which won with F394, so I am using litle softer (550/800) springs than him. And I really didnt feel problem in slow speed corners but in high speed corners!

jo white
16-08-09, 19:56
Play with the anti rollbars if fitted or disconnect rear and soften front

lander
16-08-09, 20:33
In rear I have removed anti roll bars. In front I have set monodamper to <<>><<>> , which is 404 kg/mm and 5 nothechs (0,5mm). I tested also 3 nothechs and then go to 4 and finish with 5 and I feel dallara in middle speed corners on middle throttle well and well.

Lander

yobdab
17-08-09, 06:39
In rear I have removed anti roll bars. In front I have set monodamper to <<>><<>> , which is 404 kg/mm and 5 nothechs (0,5mm). I tested also 3 nothechs and then go to 4 and finish with 5 and I feel dallara in middle speed corners on middle throttle well and well.

Lander

Remember that until the pre load of 5 notches is overcome the roll is actually double the setting so 808 kg, after the pre load is exceeded it drops to 404 kg. The pre load setting is used to adjust this transition. If we were running at (())(()) then I would set the pre load higher, maybe 15. It could be that you are experiencing the transition when you should not be. Light or no RARB is good.

lander
17-08-09, 07:48
What mean RARB?

SteveSlowboy
17-08-09, 08:08
Rear anti roll bar

yobdab
17-08-09, 08:08
How about Rear Anti Roll Bar.

lander
17-08-09, 10:24
I removed it for hillclimbing.

lander
17-08-09, 13:17
I am now looking at manual for F394 and in my setting, it has max deflection 2,08mm and max notheches what is possible to set is 14!

Filip

yobdab
17-08-09, 13:44
I am now looking at manual for F394 and in my setting, it has max deflection 2,08mm and max notheches what is possible to set is 14!

Filip

I am 6000 miles away from my manuals at present and made a guess of 15. Call it 14 then.

lander
17-08-09, 13:54
Really 14? It is 1,4mm so only there is space for 0.68mm of movement to the side!

Filip

lander
18-08-09, 20:17
Anybody else has idea about setting of monodamper and LSD for hillclimbing.

image
18-08-09, 20:40
How's your rear wheel alignment --- I once had a bit of accidental toe out on the rear and it was very tail happy :D

K

lander
18-08-09, 21:20
About rear aligment. I had around 2 degree camber and toe in 1mm on each wheel, so together 2mm toe in, so correct setting I think. And if there will be problem, I will find it in slow corners and in high speed straights.

image
18-08-09, 22:48
I can see how your LSD might contribute to understeer by being too fierce and pushing the front wheels on, but it's harder to see it making your car oversteer and spin out --- classically to reduce oversteer you'd go for lowering the rear ride height, reducing the rear tyre pressures, increasing front/reducing rear ARB or stickier compound on the front than rears --- if, as it appears, your geometry is all ok and you're not getting some odd strain induced change in rear wheel alignment when the car's being pushed hard.

(That's about the limit of my knowledge right there :D)

Good Luck

K

lander
19-08-09, 10:05
The ride height of front was 25mm , of back 45mm. I think that optimal for hillclimbing. Tyre presure was around 1,3 bar, I am using Dunlop slicks in back 280/570/13, used on F3 race cars in hillclimbing very often here in Czech republic.

I think that happened this. I am coming to high speed corner on throtle, turn left and still on throttle, because I am using 60/80 ramps and 6 faces, it is 25 percent lock and my rear wheels are locked on that throttle together, so they are rotate the same speed. When I am in corner and turning. Inner (left) rear wheel lost grip becuase it is rotate faster than what is "speed" of road. When I lost grip, the only right rear wheel wasnt able to hold back of my formula on that throttle and also lost grip and my back going to right and totaly lost control.

So there is two problems. How much lock of LSD for high speed corners when you want to be on throttle. That corners is possible to drive on full throttle for the fastest E1 race cars. Other problem is what correct setting of monodamper. When I have no roll bar in back, the monodamper is the only the thing which help to distribute weight in corners between left and right side.

Sorry for my english. I hope that everyone understand what i mean.

Filip

Rob Stevens
19-08-09, 19:15
Hmmmm

we can't have 25mm ride height!

Rob

yobdab
19-08-09, 20:11
Filip

I cannot find my 394 manual and I have been on the Dallara intranet but they do not seem to have that year for download.

However I do have 398, 300, 302, 304 and they all give for (())(()) 571kg/mm minimum pre load 8 notches, maximum 17 notches.

Repeating myself, I know but do remember preload notches do not vary the roll stiffness but rather alter the point at which it halves.

When it does go over the preload and drops by half it is quite dramatic. You would use it on slow/medium speed corners to sharpen the turn in to the apex. A very stiff roll with trail braking to the apex will get the best turn in and then as the power is applied if you have got the notches right the roll will halve.

The other thing to remember with a Dallara is you can get away with no RARB becaues the whole car is so stiff that the front rocker assy effectively controls the roll of the whole car.

That is why what would be assumed as normal eg front stiffer more understeer is not always the case with these cars because the front bar is also controlling the rear.

You are saying that you have had trouble in high speed corners. What speed are we talking about? Unless the front is very stiff then no RARB will cause a problem say at a corner like Copse at Silverstone which if you are brave is 140mph 5th gear corner. With your set up I imagine you would experience high speed roll oversteer at a corner like that.

lander
20-08-09, 09:28
You can find dallara manuals on my homepage

http://lander.tuning.cz/

in section Dallara tech

Filip

lander
20-08-09, 09:36
The speed was around 130 kmh ( 82mph) full throttle on 3rd gear, when it happened, but the same problem I had also at some other corners at around 100mph at 5 gear.

Yeah. I understand what you mean. The monodamper can control roll of whole formula, also of back, and it doesnt matter that there is no RARB.
I calculated from manual for F394 (you can download from my website, if you have other manuals, please let me know, I will upload it to my website) that the preload from each side is little over 500 kg when you have set ((()))((( and setting what Dallara say. So when I have setting (())(()) so than I need 12 notches to have the same preload 500kg on each side.

About LSD , yesterda we installed it to another Dallara F394 (this is with new Honda mugen engine, crashed dallara was Fiat) and we are going to use 60/80 ramps and only 2 faces.

Thank you sooo much for your help. Here in Czech republic, nobody is able to help me, for everybody the setting is top secret.

Filip