Re: atts vs. limited slip

Allright well this question might sound stupid to a lot of people but i've heard some things knocking the ATTS, and want to hear what you all think. First of all, whats the difference between the ATTS and a limited slip differential? Second, ever heard of doing something like switching lanes (lets say to the left) then quickly to the right again, and have the atts still pull left? It was a comment in a review I read.

nuro

From what I understand...the two have nothing to do with one another. A limited slip is for accelerating from a stop. If you drop the clutch at 4,000 without a limited slip you are going to sit there roasting your tires. However, if you have a limited slip, it will allow for more traction on the side that is spinning. I.E an all wheel drive sport utility. When an all wheel drive vehicle is stuck in mudd and rear wheels are spinning without any traction, the front wheels will start to pull, allowing the back wheels to grab. I know that this example is different from a limited slip because we only have front wheel drive, but you get the general point of a limited slip (to allow for more traction when the front tires are spinning, which in turn produces better times when racing). ATTS on the other hand is an automatic torque transfering system which when cornering at high speeds can come in very valuable. It works by putting more power to the wheels on the out side of the turn. For example, if you are making a hard left turn, it will allow for more power to the right side of the car, which will help you hang in the corners a little longer. I have also heard that if you push the ATTS enough, it will break lose into oversteer, which is different from us that have the BASE model. Hope this helps. Also, I certainly am no expert on this, but from what I have picked up from people, this is how these things work.

 

A limited slip differential makes quite a bit of difference in the way a car handles turns.

A limited slip basically does was its name implies, it limits the slip between the two drive wheels. There are two ways to do this, gears or friction (clutch) packs. With gears, you have the option of using a Torsen type of gear arrangment (ala Quaife) or using a viscous fluid to limit the amount of slip. A clutch pack produces friction when there is slip between the two drive wheels, thus it limits the amount of slip. The tighter the clutch packs, the less slip that is allowed.

Now, with gear type LSDs, the general concensus is that Torsen is the way to go. Viscous LSDs are hardly found in high performance applications. Another benefit to the Torsen style LSD is that it is torque biasing. It will actually transfer MORE torque to the outer wheel when turning, very similar to ATTS, however it's completely passive. The problem with Torsen diffs is that one wheel always has to be loaded. If one wheel lifts off the ground, the LSD effect is lost, and the diff acts like an open diff. A Torsen diff will act during acceleration. A viscous diff usually works during acceleration and deceleration.

A clutch pack LSD literally ties the two drive wheels together with friction plates. The amount of friction determines the amount of lockup. The main benefit to clutch pack LSDs is that they work no matter what the load is on the drive wheels. However, this can be a big problem when the traction differences are quite great on a FWD car, as this causes tremendous torque steer. Another disadvantage is that the clutch packs have to be rebuilt when they wear. A gear type LSD almost NEVER has to be rebuilt.

Another problem with a clutch pack LSD is that it can cause quite a bit of understeer in a FWD car if it is a 2 way LSD; i.e. the LSD action occurs during acceleration and deceleration. The understeer effect is less in a RWD, although it is still there. To combat this problem, a 1 way clutch pack LSD can be used. It only locks up during acceleration, and acts as an open diff during deceration. A 1.5 way LSD is a blend of the two.

In the debate between clutch and Torsen LSDs, you will find lots of opinions. For FWD cars that are used for track racing, the concensus is that a Torsen diff works best (hence the popularity of the Quaife for FWD cars). For rear, it's almost a toss up, but usually racers prefer the Torsen type LSD. For drag racing, most will agree that the clutch pack is best, IF the clutch pack can handle the power.

In terms of adjustability the clutch pack wins hands down, as it can be adjusted with different friction plates, and different amounts of preload. This, however, requires one to rebuild the diff to make any changes.

If you want to know more about ATTS, do a search, I have written a ton of stuff about ATTS, and I even wrote a very technical post describing how ATTS works.

One interesting thing about ATTS (as I understand it) is that the the gear biasing (or difference in gear ratios) is fixed at +/- 15%. I haven't quite figured out what this does to the torque biasing, but it appears that the active torque biasing is not variable like most people think. In light of this fact, I would prefer a Torsen over the ATTS setup any day.

 

No one else has anything to add?

 

A limited slip differential makes quite a bit of difference in the way a car handles turns.

A limited slip basically does was its name implies, it limits the slip between the two drive wheels. There are two ways to do this, gears or friction (clutch) packs. With gears, you have the option of using a Torsen type of gear arrangment (ala Quaife) or using a viscous fluid to limit the amount of slip. A clutch pack produces friction when there is slip between the two drive wheels, thus it limits the amount of slip. The tighter the clutch packs, the less slip that is allowed.

Now, with gear type LSDs, the general concensus is that Torsen is the way to go. Viscous LSDs are hardly found in high performance applications. Another benefit to the Torsen style LSD is that it is torque biasing. It will actually transfer MORE torque to the outer wheel when turning, very similar to ATTS, however it's completely passive. The problem with Torsen diffs is that one wheel always has to be loaded. If one wheel lifts off the ground, the LSD effect is lost, and the diff acts like an open diff. A Torsen diff will act during acceleration. A viscous diff usually works during acceleration and deceleration.

A clutch pack LSD literally ties the two drive wheels together with friction plates. The amount of friction determines the amount of lockup. The main benefit to clutch pack LSDs is that they work no matter what the load is on the drive wheels. However, this can be a big problem when the traction differences are quite great on a FWD car, as this causes tremendous torque steer. Another disadvantage is that the clutch packs have to be rebuilt when they wear. A gear type LSD almost NEVER has to be rebuilt.

Another problem with a clutch pack LSD is that it can cause quite a bit of understeer in a FWD car if it is a 2 way LSD; i.e. the LSD action occurs during acceleration and deceleration. The understeer effect is less in a RWD, although it is still there. To combat this problem, a 1 way clutch pack LSD can be used. It only locks up during acceleration, and acts as an open diff during deceration. A 1.5 way LSD is a blend of the two.

In the debate between clutch and Torsen LSDs, you will find lots of opinions. For FWD cars that are used for track racing, the concensus is that a Torsen diff works best (hence the popularity of the Quaife for FWD cars). For rear, it's almost a toss up, but usually racers prefer the Torsen type LSD. For drag racing, most will agree that the clutch pack is best, IF the clutch pack can handle the power.

In terms of adjustability the clutch pack wins hands down, as it can be adjusted with different friction plates, and different amounts of preload. This, however, requires one to rebuild the diff to make any changes.

If you want to know more about ATTS, do a search, I have written a ton of stuff about ATTS, and I even wrote a very technical post describing how ATTS works.

One interesting thing about ATTS is that the torque biasing is FIXED at 15%. It is NOT variable like most people think. In light of this fact, I would prefer a Torsen over the ATTS setup any day.

You obviously know just a "little" bit more about this stuff than I do. Wow, maybe you should write for a magazine in the technical column. Nice work.

 

It's just stuff I picked up from reading magazines, technical articles, talking to racers, and forums like this!

 

It's just stuff I picked up from reading magazines, technical articles, talking to racers, and forums like this!

He's just a car geek.

 

No one else has anything to add?

You took the words right out of my mouth... way to go. :laugh:

 

One interesting thing about ATTS is that the torque biasing is FIXED at 15%. It is NOT variable like most people think. In light of this fact, I would prefer a Torsen over the ATTS setup any day.

By this statement do you mean that the ATTS system is either putting 15% more power or no power to the outer wheel (i.e. All or nothing)?

 

Nevermind, I did a search and found out that you stated that the ATTS is either on or off.

 

The search function is a wonderful thing. It's also explained in great detail in the Helm's manual.

 

No one else has anything to add?

Damn! I was about to explain it to himbut uhh... you said what I was gonna say..... yah thats it.

 

No one else has anything to add?

Well, you covered all the bases this time man.... Just nothing to add at this time...

 

yet again 71dsp ends the discussion with everything u really need to know ehhehe.

and who didnt vote for him in the "election day" thread?
http://www.preludeonline.com/showthread.php?s=&threadid=41671

 

Hmm... Now that you're starting to state your ideas on the ATTS unit as FACT, I'm going to have to read up on it.

Honda does claim up to 80% torque transfer in their literature. I can't believe that they would openly lie about something like that.

I'm not an engineer, but in the previous thread you state that it will increase speed to one wheel by 15%. Does a 15% increase in speed to one wheel translate to 15% increase in torque?

 

I would have voted for Malken myself since he is the one that provides this site for us!!!!

 

Hmm... Now that you're starting to state your ideas on the ATTS unit as FACT, I'm going to have to read up on it.

Honda does claim up to 80% torque transfer in their literature. I can't believe that they would openly lie about something like that.

I'm not an engineer, but in the previous thread you state that it will increase speed to one wheel by 15%. Does a 15% increase in speed to one wheel translate to 15% increase in torque?

Well, the torque transferred could be up to 80%. The thing that needs to be thought about is that the diff is not locked. The output is just geared so that the left wheel is driven at a gear ratio that is 15% higher or lower (depending on the direction that you are turning). The diff is still open.

I should have said it differently in my first post, instead of saying that the torque biasing is fixed at 15%, I should have said that the gear biasing (or difference in gear ratios) is fixed at +/- 15%. I will edit my original post to fix that.

 

Hmm... Now that you're starting to state your ideas on the ATTS unit as FACT, I'm going to have to read up on it.

Okay, just for you, I added the disclaimer that it's the way that ATTS works as I understand it.

Read up on it, and let me know if you agree or not.

 

billy is hehe

 

Seriously when you first wrote all that, I read about half of it, then lost interest. The extent of the knowledge I'm looking for on ATTS is how do I get rid of it.

I have some vacation coming up over the holidays. My engine is apart again. I'll take some pictures of the ATTS unit and read through your explanations and see what I can from the Helms. If I can somehow get it to do something useful, like help with launches or something it would be better than nothing.

 

Wow, I even got a mention in that voting thread. I think you would have gotten more votes, Billy if you helped people choose what rims and body kit match their car more often.

 

From what I know, ATTS won't help with launches or anything because it doesn't limit wheelspin. It still relies on the fact that both wheels are firmly planted on the surface that you're driving on. There was some debate as to whether or not the differential in the SH was an LSD, but I seriously doubt it. I believe that it's an open differential. If you have it apart, take a look at the diff as well and see if you can tell. I suppose there is another way to tell. When you do a burn out, is it a one wheel wonder?

As for you losing interest, I don't know what to tell you. What can I say, I am long winded! Figure out ATTS and let us know how you think it works, then we can compare notes.

 

Wow, I even got a mention in that voting thread. I think you would have gotten more votes, Billy if you helped people choose what rims and body kit match their car more often.

Of course. Then again, I might have gotten more votes if I didn't piss people off so much.

 

If course. Then again, I might have gotten more votes if I didn't piss people off so much.

Ws that a retorical question?

 

From what I know, ATTS won't help with launches or anything because it doesn't limit wheelspin.

Mmy ATTS just sits like a dead lump behind my block so it really doesn't do anything. What I was really thinking of was trying to get some type of simple controller made up that would sence wheel spin using the wheel speed sensor and drop torque from the spinning wheel.

It seems like a very simple thing to make up. When I was looking at the ATTS controller wiring diagrams, I seem to remember that the left/right torque control was done through variable voltage to two wires. I haven't looked at it in a while, though.

 

Okay, just for you, I added the disclaimer that it's the way that ATTS works as I understand it.

Speaking of which, whatever happened with that dude that said he knew about ATTS more than you did, the same guy that also said that he had a Type S h22? Did he ever respond back to your emails?