Improviz

I repeat: would you like to run against one, with video this time?

Chappy

^^LSD definitely helps....2 to 3 tenths is my understanding

Deuuuce

Only if traction is a problem. Most street cars won't lose traction at 5mph.

I stated street cars on street tires. I should have stated rear wheel drive street cars on street tires. Excess tire spin with front wheel drive is expected and an LSD is mandatory.

A properly launched rear drive street car on street tires does not need an LSD. SRT-8s, 335is and a host of other cars are prime examples. An open diff will lay down twin strips of rubber just like an LSD.

An LSD comes into play in drag racing for several reasons. Evenly warming up the tires and transferring power when slippage occurs due to excess power.

HOWEVER it is DESIRABLE because it can help salvage a "bad" launch due to one wheel slipping.

By the way, the new McLaren MP4-12C does NOT have an LSD, which is even more desirable on the racetrack than the dragstrip. My article about here: http://www.examiner.com/x-5826-San-J...McLaren-MP412C

Jons95c36amg

You are such thick headed. Ive done many 5 rolls without traction issues only when the tires are not worn and warmer temps. So it means when I hook its less lbs that has an advantage. For an example a LS2 400hp GTO which has 395ft trq but is over 3700lbs. Ive run them plenty of times from a slow roll they get walked instantly because of the lbs. Why is this so hard to understand?

Jons95c36amg

I know for a fact that LCD helps when coming out of a turn.

Improviz

I repeat, again: would you like to run against an E90, with video this time?

You know, the one you said you beat because you "drafted" him?

Improviz

Um, you know, it's funny to watch you dodge. We ARE talking about a car where traction is a problem, not "most cars".

It also helps the ET, and you're spinning like a top. Does physics work differently for FWD cars than for RWD? No. In either case, you're talking about a sudden jold of torque to two driven wheels, which results in spin. A limited slip diff helps to alleviate this, regardless of drive configuration, and Eaton's material show this: by no means do the organizations they list use exclusively FWD cars, nor do they use exclusively non "street" cars.

Quaife explicitly states on their website that: 1) LSDs help standing start acceleration, and 2) it is beneficial to both FWD and RWD cars. They do say that it benefits FWD cars *more*, but that it is still beneficial to RWD cars:

Here's a documented example of a RWD car, on street tires, that picked up three tenths simply by adding LSD. Interesting that this is the same amount that the FWD car picked up, given that you seem to maintain that only FWD cars can benefit from LSDs.
http://www.modified.com/projectcars/...t_3/index.html
They picked up three tenths in the 1/4 after they added the LSD to this ***RWD*** vehicle.

So there you have it: I've presented data from two vehicles, one FWD, the other RWD, where each vehicle picked up three tenths after the addition of an LSD.

Now, how about you do the opposite: you maintain that LSD does not help a car's 60' or 1/4 mile times. I just gave you an example where it plainly did, being the only modification that was performed on a car that suddenly picked up three tenths.

So show me some data that demonstrates otherwise. "It's true because I say it is" really isn't much of an argument; I could say "Deuuuce, I know it's true that lead can be turned into gold, it's called alchemy", but saying it's so doesn't make it so.

Show some data. Give a documented example of a high-powered street vehicle, on street tires, which was tested both with and without LSD where there was no performance gain with the LSD.

Otherwise, this is really quite pointless, as if it isn't already.

Chappy

I'd love to run you Jon...at a track, on video.

DarrenCT

Now, Jon, bone stock is 400/400, but who's counting, huh? (just like RWP is really more like ~300~ on yours, stock) Step up and race Chappy, he has actually proven results.....


BTW, be sure to film your next LS2 GTO kill.... i def wanna see how bad you *walk* them......

Deuuuce

I'm not dodging anything. Name some cars with warm tires, warm surface where a 5mph roll-on is traction limited?

You quoted data from a source that doesn't know a powerslide CAN be initiated and controlled WITHOUT an LSD. And arguably IS more predictable.

Then they use an example of a bad run on bald tires to a better run because it was EASIER with the LSD. While they claim an open diff with 274hp is "useless" Obviously if properly driven with that trap speed, open diff or LSD, a low 13 or even high/mid 12 was possible. That's not data, that's traction management on bald tires. And no disclosure of 60ft times. How laughable.

I already gave you REAL WORLD examples of cars with open diffs that crack off 1.9 60fts ON STREET TIRES and a few times 1.8s running 12s with OVER 400rwhp. SRT-8s and 335is.

If you knew more about drag racing, you'd know that it's ALL in the 60ft and an LSD does NOT give you .3 in the 60ft NOR does it give you .3 in the ET unless one tire loses traction.

In fact, SRT ENGINEERS stated that an LSD can actually slightly DECREASE ETs due to the constant shifting of the power delivery between axles.

With that being said, LSD IS more desirable but as long as there is traction, it doesn't magically give you a better ET. If a tire slips DURING the run, absolutely, LSD all the way. Even if both tires break loose briefly because of a shift into the next gear, the open diff will still apply power to both axles.

Jons95c36amg

The argument here is about the 5roll and who has the advantage. The heavier Clk55 or the lighter Clk55 when both hook up. Like I said anything can happen in Mexico.

Jons95c36amg

Boy I wish I had video for all my runs. Chappys best run was a 13.3@109 way back when his Clk55 had very low miles. I think I had more then double his mileage when I did the 13.1. AMG motors get stronger as the miles build.

Jons95c36amg

Well you know me W208 Clk55s are so rare around here. I saw the same 2 Clk55s in the last 10yrs.

Improviz

Yes you are. I provided two examples of two cars, which, once equipped with LSD, got 0.3 second improvements in their 1/4 mile times.

I present evidence that drag racers use then, and you dodge by some idiotic argument about "street cars on street tires", as though the physics of launching a street car on street tires is somehow different than the physics of launching any other car, and ignoring the fact that the NHRA and other organizations I listed are NOT exclusively populated by slick-bearing, top-fuel dragsters and funny cars, but by hobbyists who actually race street cars, with street tires, and who feel it's beneficial to add limited slip diffs to their cars.

I'm well aware that the 60' time is what makes or breaks a run. But you haven't shown a single documented piece of evidence that demonstrates an LSD does NOT help 60' times, which is what you've been arguing.

Now, as I said: if you've got some DATA, i.e. you can provide some documentation showing that it DOESN'T improve 60' times, then please present it. I've already presented it for two cars where it did, only to have you engage in spin and relentless hair-splitting, and it's getting tiresome.

Because you can claim to be The Ultimate Authority on Drag Racing all you like, but from where I sit you're just a blowhard who's trying to blow smoke up people's *****. Do some reading about the operation of an open diff and get back to me.

Until you provide documentation backing up some of your claims, this discussion is over. I have no interest in assertions without evidence to back them up.

Improviz

No, the argument here is whether or not your claim of a 4.6 second 5-60 is accurate, and my point is that if you can hit a 4.5 second 0-60, then you should be able to duplicate the supposed 130+ mph win you scored against an E46 M3, which has 70 more horsepower than your car.

The reason you won't agree to show up and run one is obvious: because you know that the numbers show it's a significantly faster car, and you'd get your clock cleaned.

Which, along with other dubious kill stories, is why anyone with a brain knows that you're all talk, and that a pretty good portion of what you claim can be taken with a shaker full of salt.

Deuuuce

A front wheel drive example (stating the obvious) and the other I already blasted as being invalid because it improved a horrible run to a simply bad one. It's like arguing LSD is better on wet surfaces. No kidding.

Of course an LSD is beneficial I already stated that. And any case there is single tire slippage, which can occur in drag racing, it's beneficial.

But an IDENTICAL car equipped with an LSD vs. an open diff with adequate traction will NOT have a better 60ft or ET. Equip SRT-8s and 335is with LSDs and they will NOT lower the 60fts or ETs.

In fact, add slicks or DRs and it still holds true. Drag racers use them for consistency, mechanical reliability. Having more power applied to the tire not losing traction as well as warming up the tires equally are other reasons.

From how stuff works, "*The Torsen (from Torque Sensing) works as an open differential when the amount of torque going to each wheel is equal. As soon as one wheel starts to lose traction, the difference in torque causes the gears in the Torsen differential to bind together."

In other words, when there isn't uneven slippage, an LSD does NOTHING. A brief loss of traction (like a 2-3 shift), if the traction is virtually equal, again, both tires will spin anyway.

skratch77

Just like to add that I have huge traction issues with my E55 right now,over the summer a friend with a k4 or k3 car and lsd was cutting 1.7s all day and my pos open diff was spinning just the right wheel at the track.My best 60ft was a 1.9 on brand new drag radials.

My car at this point is useless on the street they way it sits,I put down 575ftlb to the ground from like 2k on and then added an 82mm tb and its getting a custom tune soon,the car has no freaking tracktion,period.Im driving it on drs as reg tires.

its prolly putting about 620-630 ftlbs to THE GROUND NOW lol,I can spin in second gear at 40mph with ease duceee,theres no street tire that can hold up.Also my next mod is an LSD because all it does at the track is one wheel peel and then wheel hop.

went from 12.4 stock to 12.8 modded but gained like 8mph in my trap(that was before the tb lol)

Id love to give you a ride at 5mph and leave a 100 yard patch on the ground for ya lol.

those little 335s arnt making 700ftlb of torque under 3k where you try and get the car launched.

here is one run with 560ftlb,Im looking for the 575 run,this was a box tune.should be over 620 and 520 with the bigger tb and custom tune(again this will be dyno'd asap and isnt done yet)but people are getting 520whp with my mods minus the 82mmtb

Deuuuce

Impressive car and it all sounds spot-on to me. I'm guessing the tire that was spinning is the same one that wasn't getting warmed up in the water box because of even loading of the power?

As far as running DRs as street tires, don't they need low air pressure and warmed up to be effective? Otherwise not much of traction aid, correct?

A pullied E55 will light up the tires at a 5mph roll while holding 1st gear? I definitely find it believable, but what other car could do that?

Improviz

So you keep saying, but opinions don't count. Prove it. Provide a documented example, because otherwise you've got nothing but empty assertions. You can throw rocks at the previous examples all you like, but the fact remains that in both examples, the vehicles DID lower their 60' AND their ETs.

And you're saying that since FWD cars have more traction issues at launch, then an LSD will help them more. Well gee, aren't we discussing cars here that have traction issues at launch? So you're arguing that an LSD helps some cars that have traction issues at launch, but not others??

Do you realize how ridiculous you sound? Stop twisting, dude,

Guess the strips those guys tested those cars at and got improved results must've had lots of "uneven traction" issues. Seriously, how can you guarantee that the traction will always be 100% equal, and that both wheels will break loose at exactly the same time?? I live on Earth, where are you, in Utopia?? Get serious. That you would make such a preposterous statement shows a complete ignorance of the physics involved in launching a vehicle, particularly a drag racing vehicle which will typically have a solid rear axle.

The thing is this: an open diff will sends the most torque to the wheel with the least traction. In extreme cases, i.e. when one wheel is on ice and the other is dry, the wheel on the ice will spin, and the wheel on the dry will not. In a perfect hypothetical world like you're describing, neither rear tire will break loose first, both will break loose in perfect unison, and lo and behold, all will be perfect, well, and good.

Except we're talking real world, not hypothetical. And there is NEVER any guarantee that both wheels will have the same traction (in fact, the left side of the vehicle will be 5% more heavily loaded than the right by virtue of the fact that the driver is sitting on that side), or that one won't break loose first and screw things up.

Further, unless the vehicle in question has an IRS, you'll get reduced loading on one rear tire from the frame twist induced by the torque loading on the rear axle. Which will result on an uneven loading on each rear tire. Which increases the likelihood that the more lightly loaded tire will break loose. Which reduces, demonstratably via physics, the tractive force available to propel the vehicle forward, by a marked amount.

Which is why you want an LSD on there.

Which is why they're so widely used by drag racers: because they increase the tractive force, NOT solely to do tire-warming burnouts as you allege. This is why their manufacturers can claim, accurately, that they increase traction. Because they do, and the physics show it.

And if you'd like to see a derivation of the forces involved, and how an LSD-equipped vehicle WILL (not can, WILL) generate roughly 10% more tractive force than one without, then you can start with the following article on Hot Rod magazine, which, unlike you, actually supports its assertions with facts and physics, not ignorant assertions.
http://www.hotrod.com/techarticles/chassis/chassis_tuning_tire_traction/index.html

You will note that he derives the tractive force for a limited-slip, and non-limited-slip equipped vehicle which is in all other aspects identical. And you also note that the physics shows that the vehicle with the LSD generates on average roughly 10% greater tractive force than without the LSD.

THAT'S why they use them. NOT for burnouts, but because they increase the tractive force. A 10% difference will have a HUGE difference on 60' time, AND on ET.

Stop wasting my time.

Improviz

Uh, no, dummy, it's because the vehicle doesn't have an LSD. Geez, you'll twist like a pretzel before you admit you're wrong. He already told you that the other guy was there with a similar setup *and* an LSD was cutting 1.7 sec. 60' times, and didn't say a DAMN THING about any water box issues, or loading, or any of the other conjecture in which you'd care to engage to avoid admitting you're wrong.

Jons95c36amg

Improviz now has 3 guys(me,clk550,deuuce) on his case. Geez

Jons95c36amg

Are you that dense? Ok answer this question. The C&D mag that did the 4.5sec and 4.6sec 5-60 ran the 1/4 in 13.1@109. My car also did 13.1 meaning it falls in the same category. So your saying my 300lbs lighter car with the same trq is slower in a 5roll!? When traction isnt a issue? How dumb can you be?

M-bENZ

lol

Andy

Deuuuce

You're incorrect on multiple points.

The flaw in the article and the LSD equation is that axle twist and lift occurs in an LSD car, whether it's a SRA or IRS. Wheel hop is a common result.

Additionally, it is documented the amount of force applied to the ground doesn't change in either type of differential in a straight line. Vehicle weight shifts occur in both cars. Assuming the formula for the LSD is correct for a moment, that "10% advantage" is meaningless if there is no slippage nor does it translate to a quicker ET.

The adhesion coefficient may not be identical, but how the tires react with the applied force means they react the same many times. Otherwise an Open Diff car could NOT drag race.

I'm not the only one who knows this.

From the Miata.net forum: http://forum.miata.net/vb/showthread.php?t=309481

http://www.angelfire.com/my/fastcar/diffey.html

No reduction:
http://www.ppi-ats.com/LSD/LSD_basics.html

In no article anywhere does it state the power is applied more efficiently without slippage, no manufacturer states acceleration times improve and in no where is it stated mileage or power to the ground is increased.

Argument also implies the 60ft would drop simply with the addition of the LSD, doesn't happen either despite a flawed example of a what, a 2.5 vs. a 2.3 60f. I.E. both runs sucked.

An ideal launch at the dragstrip has minimal to no slippage. The extensive use in drag racing with high horsepower cars and driveline shock eventually migrates to a Spool type LSD which is essentially a locked differential. Which does not transfer power back and forth and is for extreme power conditions. Again, the fact that Open Diff cars are able to drag race in itself points out how consistent traction can be on at the dragstrip.

The sheer power of many cars requires an LSD due to the POTENTIAL for slippage.

'09 SRT-8s with LSDs are not any quicker than pre-09s with open diffs.

An open diff car, if both tires break loose, 50% power is still supplied to each side unless an appreciable amount resistance occurs.

The Successful Race Car Driver: A Career Development Handbook, "Many Indy Race Engineers use an Open Differential....because it wastes less power".

Other sources:
"In dry conditions, when there is plenty of traction, the amount of torque applied to the wheels is limited by the engine and gearing" and,

"So basically in drag racing terms a limited slip differential is only helpful when traction is an issue. If your tires are good and you setup is solid, you should be able to launch the car without much wheel spin, thus negating the need for a LSD. But if your power becomes to much and launching the car easily causes wheel spin, a LSD is a helpful way to control the spinning tire and apply the power more efficiently to the ground."

Open diff with slightly more hp on the dyno with an incorrect conclusion:
http://www.importtuner.com/features/...ial/index.html
Spinning to much while moving forward reduces the trap speed by effectively running out of track.

Bottom line, a properly launched car doesn't "need" an LSD and the consistency in traction occurs every day on dragstrips across the country in Open Diff cars. It isn't ideal, but it works.

skratch77

I had a custom lsd built for my m3 with 3 clutch packs and 40% lock up,are you trying to tell me I didnt get better traction off the line?It sure as heck felt like it put down power alot better lol

My next mod in my e55 is a lsd,these cars are not mazdas.with the amount of torque we make an lsd is almost 100% manditory