Differential woes in GPL

I am having trouble with the rear end in my car setups. I swear the problems were not there until two weeks ago. Now when I go into a turn under deceleration my inside tire breaks contact. Many times this sends me into wild oversteer. I know it has to do the the ramp angles but, I've tried all of them and can't get rid of it. If my understanding is correct the higher the second number in the diff. the less of this effect I would see. Thanks, Bob PS. These set ups are in the Eagle. I went back to my Lotus but the same effect is in this car now. HELP

I've found that with higher ramp angles for deceleration (the second number in the differential setting), letting go of the gas will help turn the nose into a turn, creating some oversteer. I'll use an 85/60 setting for courses with long fast turns - it let's me use the throttle to help 'steer' the car. Brian

The more "decelleration turn" I want, the lower I make that second number- that is what I've independently found. And it can make the car virtually undrivable it you aren't prepared- it is one of the most sweeping single changes you can make. Esp. making the first value too small... like racing on ice! But my question... uh, what the hell are "ramp angles"?!? I seem to have them working for me, but I don't know what they are! I've assumed they somehow set the amount of difference allowed between two wheel's rotation. But an explanation would be nice... And while I'm asking... number of clutches... what good does that do me? and what is that other differential setting I can make? Please post here... thanks!

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>Brian >> .... Now when I go into a turn under deceleration my inside tire breaks >contact. >> ... If my understanding is correct the higher the second number in the >diff. >> the less of this effect I would see.

>>I've found that with higher ramp angles for deceleration (the second number >>in the differential setting), letting go of the gas will help turn the nose >>into a turn, creating some oversteer. I'll use an 85/60 setting for courses >>with long fast turns - it let's me use the throttle to help 'steer' the car. ... >But my question... uh, what the hell are "ramp angles"?!? I seem to >have them working for me, but I don't know what they are! I've assumed >they somehow set the amount of difference allowed between two wheel's >rotation. But an explanation would be nice... They determine how fast the clutches are activated (probably all analog business here; meaning they are not either on or off). The first angle is for acceleration, the 2nd angle for deceleration. The higher the angle value, the quicker the clutches are put to use. The more clutches, the sooner both wheels are locked together to avoid spinning just 1 tire (2 spinning tires is easier to control when the car wants to break out (?)). The diff ratio is a general ratio which applies to all gears. Sort of like a gear ratio extra factor. 10/31 is the largest (most handy on fast tracks; I mean lots of high speed tracks). Ruud van Gaal MarketGraph / MachTech: http://www.marketgraph.nl Art: http://www.marketgraph.nl/gallery

<...> Hmmm... I think I need to go back a bit here. "Clutch" to me means the mechanism that controls the conection between the engine and the drive-shaft- controled by the driver with the far-right foot pedal. But I may have missed the information boat here! Are we talking about friction devices somewhere further down the line (and not controlled by the driver's foot)? Thank you very much for the explanation. Turns out I might have needed more than I thought, though! :-)

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| |<...> | |>>But my question... uh, what the hell are "ramp angles"?!? I seem to |>>have them working for me, but I don't know what they are! I've assumed |>>they somehow set the amount of difference allowed between two wheel's |>>rotation. But an explanation would be nice... |> |>They determine how fast the clutches are activated (probably all |>analog business here; meaning they are not either on or off). |>The first angle is for acceleration, the 2nd angle for deceleration. |>The higher the angle value, the quicker the clutches are put to use. | |Hmmm... I think I need to go back a bit here. "Clutch" to me means the |mechanism that controls the conection between the engine and the |drive-shaft- controled by the driver with the far-right foot pedal. | |But I may have missed the information boat here! Are we talking about |friction devices somewhere further down the line (and not controlled |by the driver's foot)? | |>>And while I'm asking... number of clutches... what good does that do |>>me? and what is that other differential setting I can make? |> |>The more clutches, the sooner both wheels are locked together to avoid |>spinning just 1 tire (2 spinning tires is easier to control when the |>car wants to break out (?)). |> |>The diff ratio is a general ratio which applies to all gears. Sort of |>like a gear ratio extra factor. 10/31 is the largest (most handy on |>fast tracks; I mean lots of high speed tracks). | |Thank you very much for the explanation. Turns out I might have needed |more than I thought, though! :-)

What you are calling the clutch is simply the actuator pedal for the transmission clutch. The actual clutch is a large disc that presses against some pads that are the continuation of the drive line. (Yah, I know it's simplified) When the clutch pedal is depressed, the pads are released, allowing the spindle that sticks out of the back of the engine to spin without gear-induced drag. The differential clutch is essentially the same thing. On a regular car (the kind you use to get from point A to point B) there is NO differential clutch. They are expensive to build into a car, and if you are outraged by paying $75 for floor mats, think aboutthe extra coin you'd have to drop for a performance diff. Some vehicles DO have "posi-track" or some such, but they are much rarer than the open diffs. Drive your regular car into mud. Stop. Then apply the throttle. One wheel will break loose and all your energy goes into that spinning wheel. The other one doesn't budge. That's because there is NO clutch mechanism in your differential. Drive your Lotus into the mud. (Don't try to tell me you've never put it there!) Stop - preferably shiny side up. Apply the throttle. One wheel will break loose and start to spin, then the ramp angles in your diff will come into play. The higher your ramp angles on the "left" side of the setup page, the more quickly your clutch will start to bind the left wheel to the right one until both are locked together. Both rear wheels now have traction and poof! you're out of the mud. As soon as the torque applied to the rear wheels is lessened (say by the car popping onto the road and increasing in speed while the throttle remains constant) the right-hand ramp angle numbers take effect. These control how quickly the diff unspools and you have independent L & R wheels again. Try it in real life with your car and a (gullible) friend's car (IF he has a performance diff). If I'm wrong on any of this, I'm simply going to say it's April Fool's Day, and remain silent. Mikey Avetikus Racing

Thanks very much- you've cleared things up quite a bit. I'll leave your explanation intact below for the sake of others. On Thu, 1 Apr 1999 19:44:56 -0700, "Mike Rodriguez"

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>| >|<...> >| >|>>But my question... uh, what the hell are "ramp angles"?!? I seem to >|>>have them working for me, but I don't know what they are! I've assumed >|>>they somehow set the amount of difference allowed between two wheel's >|>>rotation. But an explanation would be nice... >|> >|>They determine how fast the clutches are activated (probably all >|>analog business here; meaning they are not either on or off). >|>The first angle is for acceleration, the 2nd angle for deceleration. >|>The higher the angle value, the quicker the clutches are put to use. >| >|Hmmm... I think I need to go back a bit here. "Clutch" to me means the >|mechanism that controls the conection between the engine and the >|drive-shaft- controled by the driver with the far-right foot pedal. >| >|But I may have missed the information boat here! Are we talking about >|friction devices somewhere further down the line (and not controlled >|by the driver's foot)? >| >|>>And while I'm asking... number of clutches... what good does that do >|>>me? and what is that other differential setting I can make? >|> >|>The more clutches, the sooner both wheels are locked together to avoid >|>spinning just 1 tire (2 spinning tires is easier to control when the >|>car wants to break out (?)). >|> >|>The diff ratio is a general ratio which applies to all gears. Sort of >|>like a gear ratio extra factor. 10/31 is the largest (most handy on >|>fast tracks; I mean lots of high speed tracks). >| >|Thank you very much for the explanation. Turns out I might have needed >|more than I thought, though! :-) >What you are calling the clutch is simply the actuator pedal for the >transmission clutch. The actual clutch is a large disc that presses against >some pads that are the continuation of the drive line. (Yah, I know it's >simplified) When the clutch pedal is depressed, the pads are released, >allowing the spindle that sticks out of the back of the engine to spin >without gear-induced drag. >The differential clutch is essentially the same thing. On a regular car (the >kind you use to get from point A to point B) there is NO differential >clutch. They are expensive to build into a car, and if you are outraged by >paying $75 for floor mats, think aboutthe extra coin you'd have to drop for >a performance diff. Some vehicles DO have "posi-track" or some such, but >they are much rarer than the open diffs. >Drive your regular car into mud. Stop. Then apply the throttle. One wheel >will break loose and all your energy goes into that spinning wheel. The >other one doesn't budge. That's because there is NO clutch mechanism in your >differential. >Drive your Lotus into the mud. (Don't try to tell me you've never put it >there!) Stop - preferably shiny side up. Apply the throttle. One wheel will >break loose and start to spin, then the ramp angles in your diff will come >into play. The higher your ramp angles on the "left" side of the setup page, >the more quickly your clutch will start to bind the left wheel to the right >one until both are locked together. Both rear wheels now have traction and >poof! you're out of the mud. As soon as the torque applied to the rear >wheels is lessened (say by the car popping onto the road and increasing in >speed while the throttle remains constant) the right-hand ramp angle numbers >take effect. These control how quickly the diff unspools and you have >independent L & R wheels again. >Try it in real life with your car and a (gullible) friend's car (IF he has a >performance diff). >If I'm wrong on any of this, I'm simply going to say it's April Fool's Day, >and remain silent. >Mikey >Avetikus Racing