Look what I found. For $599, they offer an LSD for almost any transaxle that would be used in a Fiero. Check out: http://www.drivetrain.com/ At the left bar scroll down until you can click on the link to "Positraction GM FWD Automatic"
"The EP Limited Slip Differential (EP-LSD) for your GM Front wheel drive vehicle applications. This a clutch-type, pre-loaded limited slip differential that applies power to both drive wheels all the time. It is still a full-functioning differential, not a "locker" or spool, so it is totally street driveable. The EP-LSD used two sintered-bronze clutches, CNC-machined hardened-steel pre-load plates, and custom pre-load spring rates to provide unequaled front-wheel-drive traction. Transmissions include: TH125, TH125C, 3T40, 440T4, 4T60, 4T60E, 4T65E, 4T65E-HD, 4T40E, 4T45E, 4T80E, Getrag 282. The EP-LSD is available for all General Motors front wheel drive cars, vans, and SUV's..."
Thanks to dozol for the reference to this site.
------------------ FierOmar
[This message has been edited by FierOmar (edited 01-20-2007).]
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10:57 AM
PFF
System Bot
sspeedstreet Member
Posts: 2306 From: Santa Maria, CA Registered: Dec 2002
I remember reading that the limited slip setup for a FWD is very different from a RWD setup. Something about how much slip it allows should be different in FWD as compared to a RWD setup. Hopefully someone with more info will chime in.
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04:08 PM
FierOmar Member
Posts: 1646 From: Glendale, California, USA Registered: Dec 2001
Originally posted by Formula88: I remember reading that the limited slip setup for a FWD is very different from a RWD setup. Something about how much slip it allows should be different in FWD as compared to a RWD setup. Hopefully someone with more info will chime in.
Well... while some rear drive vehicles will use a locked rear end, I doubt that you would find too many FWD cars using that system. Otherwise, I don't see any particular disadvantage to an LSD system.
------------------ FierOmar
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04:53 PM
TennT Member
Posts: 1523 From: Humboldt, Tenn Registered: Nov 2002
Originally posted by FierOmar: Well... while some rear drive vehicles will use a locked rear end, I doubt that you would find too many FWD cars using that system. Otherwise, I don't see any particular disadvantage to an LSD system.
I think you missed what Formula88 was saying. I had never really thought about it, untill Fomula88 brought it up.
In a turning situation, the front wheels, are rolling at a different speed, compared to each other. In the same turn, the rear wheels are also rolling at a different speed, compared to each other. The ratio in the difference, is not the same front to rear. For instance in a left hand turn, the right front wheel, is rolling further then the left front. The right rear wheel is rolling further then the left rear. Now right off hand, I'm not sure which is rolling further, the right rear, or the left front, but in a sharp enough left turn, the left rear wheel will be more a pivot, not rolling much at all, where as the left front will still be rolling quite a ways. So try to picture, sharp left turn, both front tire still rolling quite a ways, one rear wheel turning a lot mor then the other. Am I sounding way off base here. Hope someelse gets it, and can maybe explain it better. I know what I'm trying to say, but starting to confuse myself! I agree with the LSD being an advantage, but if one was designed to slip a certain amount, and was constantly trying to be forced to slip another amount, I could see a potential problem. My guess would be, if they are designed different, the front wheel drive LSD would "Lock up" later then a rear wheel drive unit.
Kevin
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12:43 AM
TennT Member
Posts: 1523 From: Humboldt, Tenn Registered: Nov 2002
The tighter the radius, the greater the difference in rotation between tires. Think of a very long axle and the distance the outside has to turn compared to the inside. The rear track of an 88GT is 60.1 (or I'll say 60 for simplicity): Inside tire will be on a 5 foot tighter radius than outside.
On a tight radius, there is a LARGE difference between the two radii. If a 5 foot turn were possible, the inside wheel would turn at 50% of the outer. On a larger radius, say 30 feet, they are about 85% of each other. At 40, they are about 89% (100% being equal). So the tighter the turn, the more the LSD will engage. I wouldn't think the wheel track would matter so much as the radius of the turn and unless you are turning very tight, an LSD set up for a FWD wouldn't matter if it were used in the rear. Percentage wise, there isn't that much difference and there isn't that fine of adjustment in the LSD.
[This message has been edited by TennT (edited 01-21-2007).]
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04:24 AM
TennT Member
Posts: 1523 From: Humboldt, Tenn Registered: Nov 2002
I wonder how it will act on the steering on FWD. On a loose surface in a tight curve, would it tend to make the vehicle "plow" more? Make steering stiffer when decreasing the turn radius (tighter turn)? In a very tight turn, there may be alot of scrubbing going on.
[This message has been edited by TennT (edited 01-21-2007).]
Originally posted by TennT: I wonder how it will act on the steering on FWD. On a loose surface in a tight curve, would it tend to make the vehicle "plow" more? Make steering stiffer when decreasing the turn radius (tighter turn)? In a very tight turn, there may be alot of scrubbing going on.
I race a Neon equipped with a Quaiffe in the NASA series. Even though this is a relatively low powered car, I can definitely feel the transfer of power from one side to the other in the turns, but it has no perceptible effect on the steering. And BTW, I have disabled the power steering by looping the PS lines.
------------------ FierOmar
[This message has been edited by FierOmar (edited 01-21-2007).]
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10:53 AM
PFF
System Bot
FierOmar Member
Posts: 1646 From: Glendale, California, USA Registered: Dec 2001
Originally posted by Lambo nut: I agree with the LSD being an advantage, but if one was designed to slip a certain amount, and was constantly trying to be forced to slip another amount, I could see a potential problem. My guess would be, if they are designed different, the front wheel drive LSD would "Lock up" later then a rear wheel drive unit.
Well. there may even be a question of whether there is an advantage. According to one Lotus engineer, it may depend on the situation (e.g. autocross vs. road coarse), and addidg the LSD did change the steering somewhat. For those that don't recall, the Lotus Elise uses a Toyota engine/trans; same as the Celica GTS. See: http://www.sandsmuseum.com/...misc/nick/index.html
"The Elise was always designed from the outset to work without an LSD. We have recently started to offer an LSD as an option on the Toyota engined cars, primarily in response to market demand from the Autocross enthusists in the USA, who need one to be competitive when accelerating away at full throttle from very slow, tight corners in first or second gear.
In this type of competition they do not tend to run high speed (100mph +) corners and therefore the increase in understeer on this type of corner which you get with an LSD is of little negative consequence to them and they therefore are better off with an LSD.
In our experience an Elise or Exige equipped with an LSD is at a disadvantage to one without an LSD on a typical European race track. On top of that the LSD bluntens the steering feel and repsonse of the car which we don't like.
If you want an LSD then by all means fit one, but please understand that there are negative as well as positive effects. In the instance you describe, instead of spinning the inside wheel as you accelerate away at full throttle (which can be easily fixed by modulating the throttle! Very Happy ) a car with a 2:1 LSD like the obne we supply will provide twice the torque to the outside wheel as it does to the inside one. This will increase the slip angle of the outside wheel and the car will tend to oversteer heavily on corner exit, requiring a reduction in throttle if you are not to spin.... It isn't much quicker, honest."
So, it adding understeer increases understeer, it seems to me that it would be possible to make some other adjustments to dial in mor oversteer. BBW, notice that he said "it isn't MUCH quicker" (emphasis added).
I had also read somewhere else that the Lotus Elise had been designed to run without an LSD.
------------------ FierOmar
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11:25 AM
TennT Member
Posts: 1523 From: Humboldt, Tenn Registered: Nov 2002
Don't get the wrong idea. On the Neon the transfer of power allows the car to pull out of a corner where it would otherwise bog down. So long as it is allowed by the rules, I will continue to run one.
With respect to whether the LSD would or would not be feneficial in a Fiero application remember that the Elise was originally designed without an LSD. And remember, the Elise is very sensitive to any change. Here are a couple more comments found at the site listed above:
"11. He stated that they have acheived a suspension in which the suspension roll center and the mass roll center are in the same spot, and that is great for handling. Change springs, shocks, or tires and that dynamic will be altered significantly.
12. Suspension settings are virtually unalterable. But he said why would you want to. The car is perfect the way that it is.
13. If you change the ride height for the LSS cars, you will need to do an alignment. And not just any alignment. The car needs to have its chassis sitting on blocks of specified height while adjustments are made. I take this to be nearly full squat achieved by adding weights to the car. Procedures will be in the dealer's service manual. The car ride height will be adjustable -5mm, +10 mm."
By comparison, the Fiero's suspension settings can be altered significantly. Thus, it would seem that any understeer that may result from adding the LSD (assuming that it has the same effect on a Fiero) could be dialed out.
------------------ FierOmar
[This message has been edited by FierOmar (edited 01-21-2007).]
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12:14 PM
2002z28ssconv Member
Posts: 1436 From: Orlando, FL Registered: Jun 2005
I thought they told me it was $500 last year straight from Engineered Performance. BTW - Engineered Performance is probably what the EP stands for there. You have to send them your diff, they convert it and send it back to you.
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12:57 PM
FierOmar Member
Posts: 1646 From: Glendale, California, USA Registered: Dec 2001
I thought they told me it was $500 last year straight from Engineered Performance. BTW - Engineered Performance is probably what the EP stands for there. You have to send them your diff, they convert it and send it back to you.
I think you are correct regarding the actual manufacturer being Engineered Performance. However, when I checked their site, I did not see a price. Since the LSD is preloaded, I don't know why they would need to install it. Also, I don't know whether the Las Vegas company requires in house installation.
Phantom grip is a good stop gap solution if you have no other choice. The downside is they apply force to the case to provide the limited slip.
All diffs have their side effects. An open diff would be best in a perfect world where the car never looses traction to the inside wheel. This is because an open diff always provides the same torque to both wheels. So when one wheel goes into a zero torque condition the opposite wheel does too. Or, if in a slipping situation like the exit of a tight turn and torque generated drops off on the inside wheel so does the outside wheel A torsen type will take the lower torque between the two wheels and multiply it by its design factor an pass it to the wheel with the lower torque. Its down side is again if a wheel is in a zero torque condition no torque gets pass to the other wheel (0x any number is 0) Clutch type lsds vary on how fast and how much lock they go into. The down sides here are wear, and engagement speed. Wear is because the clutch plates are a wear item. The engagement speed needs to be set by spring tension and changes as the clutches wear.
