GPL Driving guide

Steve Blankenship wrote:

> "Dave Henrie" > wrote in message
> . 97.136...
>
>>Graham > wrote in :
>>
>>
>>>Later you will probably want to open the differential more to get more
>>>car rotation this takes more practice to balance, but lets the car steer
>>>more easily.
>>>
>>
>> How does someone 'open' the differential? Do you use larger numbers?
>>a bigger gap between the two? Or do you try to reduce the difference?
>>
>>Many folks see terms like this, and just have no idea what you are talking
>>about and how to implement it.
>>
>>Thanks for your advice
>>
>
>
> Not who you asked, but since I'm in here... ;-)
>
> Opening the diffs is achieved through lower numbers, both for the
> accel/coast side ramp angles and the clutch plates. A 30/30-1 setup is as
> open as you can get going through the stock menu, while 85/85-6 is the
> opposite extreme. Higher numbers for the ramp angles will stabilize the car
> under the condition the ramp angle applies to, either acceleration or
> coasting/braking, and the clutch plates control the max locking force under
> either condition.
>
> Early on, everyone ran ramp angles around 85/30 or 85/45 since they were
> easier to handle under power, but now the reverse (or almost) is the norm.
> Which is as it should be; in interviews way back when, even DK noted that
> everyone was running the diffs backwards. The high power-side ramp angles
> help to keep the car pointed straight when you get on the gas, but tend to
> induce high-speed understeer. The only way around that is to overdrive it
> and drift the car around at high slip angles. Which causes a lot of
> frictional drag, raising laptimes. The move to open accel-side ramp angles
> is imho one of the main reasons laptimes continued to drop in GPL. The
> aliens had pretty much gotten all they could out of the old-school setups
> and needed a way to kill the high-speed push.
>
> Of course the cars are considerably more of a handful on the gas with say a
> 45-degree accel-side ramp angle, so many who try them go back since they
> have a rough time staying on track. The cars are extremely
> throttle-steerable with the low angles and some, particularly the Lotus,
> tend to be a bit much. The cars with softer power and longer wheelbases are
> easier to live with at low ramp angles. So people just need to experiment
> and find a compromise that works for them. Coast-side angles will generally
> be higher if you're running the power side open, since they help stabilize
> the car under braking. They started out lower so you could bring the nose
> in by backing off the throttle mid-corner. Clutch plates can be looked at
> as a finer adjustment after you get the ramp angles you like, lower numbers
> will allow more slippage and let the car turn easier, while higher ones will
> make the car want to stay straight.
>
> I used to think this was all very complex until I got a look at the diff
> menu for RBR. You need a freakin' Cray to work that one out. Gpl has
> GPLRE, but RBR has a 3rd party setup utility just for the diffs!
>
> Cheers,
>
> SB
>
Like I said someone will come and tear it apart. The most obious
difference here is that Steve says:

> Opening the diffs is achieved through lower numbers

however this conflicts with the information on

http://www.geocities.com/n_heusink/setupguide/guide.htm

which states:

"In the car setup menu you can select a differential from 30/30 to 85/85
with small steps between these extremes. The first number is the ON gas
value, and the second number is the OFF gas value. A smaller number
means a bigger force (more lock) and a bigger number means a smaller
force (less lock)"

Apart from that Steve certainly sounds like he knows more (than me)
about the driving part of it.

Graham

"Graham" > wrote in message
...
> Like I said someone will come and tear it apart. The most obious
> difference here is that Steve says:
>
> > Opening the diffs is achieved through lower numbers
>
> however this conflicts with the information on
>
> http://www.geocities.com/n_heusink/setupguide/guide.htm
>
> which states:
>
> "In the car setup menu you can select a differential from 30/30 to 85/85
> with small steps between these extremes. The first number is the ON gas
> value, and the second number is the OFF gas value. A smaller number
> means a bigger force (more lock) and a bigger number means a smaller
> force (less lock)"
>
> Apart from that Steve certainly sounds like he knows more (than me)
> about the driving part of it.
>
> Graham
>

And you would be correct - stop being nice, man - just tell me I'm full of
it! ;-) That's what I get for assuming my remembrance of GPL diff lore was
still intact. Been too long!

Suppose I was thinking more of effect than cause, which was my undoing.
Fished around in my favorites and dug this up - a great pictorial guide
explaining how the ramps work in Salisbury diffs.
http://icpcitation.com/variloc_theory.htm

Back to my cave now; or better yet back to the Lotus this evening to relearn
how to drive it! Warning - VROC won't be safe this weekend...

I don't start messing with diff settings until after I get the right
balance in the chassis itself, typically if it will turn in like I want
it to, and that it never fades out understeering but has a slight
oversteer so that you can save it when loosing traction. I hate it when
my diff prevents me from driving the car the way I want.

To do this, I always start out with a completely open diff (85/85/1),
and work my way up (or down in this case). If I want a more stable
(understeering) exit, I lower the first figure. If I want more stability
during braking, I lower the next. If you go too far, the car will turn
in very sluggishly. Monaco and Nürburgring will always demand x/85 since
you're turning in all the time.

The most common diff setting for me is around the 45/60 mark. At
Silverstone I want lower figures, and will go 30/45 depending on chassis.

Your preffered diff settings will vary with setup style and driving
style, so it is very difficult to suggest any setting because there are
so many other variables in the equation. Empiri is the only way, as with
many other aspects of life.

---A---

On 03.06.2005 15:27, Graham wrote:
> Dave Henrie wrote:
>
>> Graham > wrote in :
>>
>>
>>> Later you will probably want to open the differential more to get
>>> more car rotation this takes more practice to balance, but lets the
>>> car steer more easily.
>>>
>>
>>
>> How does someone 'open' the differential? Do you use larger numbers?
>> a bigger gap between the two? Or do you try to reduce the difference?
>>
>> Many folks see terms like this, and just have no idea what you are
>> talking about and how to implement it.
>>
>> Thanks for your advice
>>
>> dave henrie
>
>
> As I understand it the differential ramp angle figures xx/xx refer to
> the "tendency to lock the differential" with power on/without power on,
> which I look at as being during whether or not you use the accelerator
> so even more simplified the first figure is out of a corner and the
> second going into a corner. There are much better and more technical
> explanations on the net. The further I get into it the more likely I
> will be talking rubbish but here goes.
>
> Put into the context of my post:
>
> Most setups that are based on the differentials in the default setups
> have figures like 85/30/4 85/45/4 and so on.
>
> The smaller the angle the quicker the differential locks so 85 locks
> slower than 30. So in a 85/30/x setup the differential locks quicker on
> power off than on power on and so it locks on braking helping to keep
> you straight and turn entry causing understeer and opens more when you
> apply throttle allowing you to be more careless with the throttle, but
> less than maximum acceleration. The final figure is clutches and I will
> not discuss them here except to say that the tendency is to see more
> clutches as increasing the tendency to lock, but with less effect than
> decreasing the angle. Clutches affect both sides.
>
> These 85/30/x or 85/45/x (x typically between 3 and 6) setups are useful
> for beginners to learn early turn in, understeering onto the apex,
> without spinning however this type of setup has come under critism as
> unhistorical and encouraging "bad habits"
>
> "Intermediate" style setups are of the type 60/60/x (x typically 1 or 2)
> These setups turn more easily, lock up much less on power off somewhat
> more on power off. When you go over from 85/30/4 to 60/60/1 you tend to
> oversteer into the corners until you get used to it.
>
> From what I have seen expert setups venture into the 45/85/x style
> reversing the tendencies from the default setups. In other words the
> differential will have very little tendency to lock on braking and turn
> in be open in the corner and lock when you get on the accelerator.
>
> I have gone way beyond my incompetency level but this is my attempt at
> understanding what I have read on the subject and relating it to my own
> humble attempts at driving GPL cars.
>
> More expert opinions can be found at:
>
> Niels Heusinkveld setup guide (with useful table combining rampangles
> and clutches).
>
> http://www.geocities.com/n_heusink/setupguide/guide.htm
>
> Nunnini's GPL Foolishness site
>
> http://website.lineone.net/~richardn/Differential.html
>
> Paul Jacksons setup site
>
> http://www.gpladdicts.speedgeezers.c...etupguide.html
>
> regards
> Graham
>

"Asgeir Nesoen" > wrote in message
...
> I don't start messing with diff settings until after I get the right
> balance in the chassis itself

Changing the diff has a big effect on the way the car behaves, the chassis
setting can all be tuned more accurately.

imo set the big stuff first so the car is set up in the right ballpark, then
fine tune it to taste with the other stuff. If you start with an open diff
you'll get the chassis working fine /with an open diff/, then when you
change the diff you'll end up having to tweak the chassis anyway ;-)

Use the diff to make it fast (for you), use the chassis to make it
driveable.

Malc.

On Thu, 02 Jun 2005 10:31:39 -0400, Jeff Vincent
> wrote:

>On Wed, 01 Jun 2005 22:53:05 GMT, "Jiyang Chen" > wrote:
>
>>I think I know what you're talking about. I have a Thrustmaster Nascar
>>Charger (non usb) that twitches a lot even if I don't apply steering input.
>>I'll look into getting something else. Thanks for the post.
>>
>
> CompUSA has the Logitech Momo Racing Force Feedback wheel for $80US
>(minus a $30 rebate) through June 4. A good wheel for a good price...
>
>http://www.compusa.com/products/prod...96053&pfp=cat3


I agree. The Momo is a great deal and a good starter wheel.

B