Mmmmmk, so I decided not to include a video with this review and I apologize in advance. Primarily because with all the editing I could do and careful attempt at presenting I couldn't quite get everything as I felt it needed to be.... My video camera's suck frankly and it's desperately time to upgrade. So after I get some better equipment a few proper cameras, I'll actually give you guys some decent footage. With that said, here's the review:
The Quaife Helical LSD. Before I can answer all the sideways going, rear end slapping, whiskey throttling questions, I have to answer some technical stuff.
Firstly, who the heck is Quaife and what the heck is a helical (hē-li-kəl) LSD?
Quaife Engineering: Quaife is a British company formed in 1965 and specializes in performance drivetrain products. These guys have designed and manufactured parts for everything from motorbikes to GT and Rally cars and briefly their own full road car . So they know their way around a rear end.. of a car
What is a helical LSD: To make a very long and slightly complicated explanation a short and still kinda complicated one, a helical LSD is just that. An LSD. The difference between this LSD and other LSD's, we'll say clutch type for this example, is that it's not always limiting wheel slip. A helical design only acts as an LSD when torque is being applied. So when coasting off throttle, the rear essentially becomes an open diff. Same for in a corner, coast and you now have an open diff. Why? Because without torque being applied the helical system has nothing to split so it kinda hangs out till it's time to work. However, once you apply the power, this thing will work overtime to make sure you've got a grin on your face.
What's it like for daily driving: It's very quiet and almost antisocial. Unless you make a habit of screaming around every bend to work and stomping it from every light you won't notice it very much. But before you stop reading and go back to deciding which winter setup to get, hear me out.
It was pouring like crazy a week or so ago and I decided to maintain speed while turning left through a green light. In a town where it rains three weeks out of the year ,at best, road grime and nil traction go hand in hand here when things get wet. So I totally drifted the crap out of that turn #LSD yo.... Mmmmm noo. I braked appropriately and kept going. Nothing happened. Not a thing.. The DSC light didn't even come on. Unlike other LSD's I've had in the past which ALWAYS want both wheels spinning equally, this LSD works only when and how it needs to. It doesn't fight your DSC system, it compliments it. So it's working even when you don't realize it and may never even notice it. And that's a good thing.
What about performance....*drifting*: Okay let's get this out of the way. If you want to drift every curve deeper than a Japanese anime teenager.. You want a different rear diff or just a different car. Most of your track day drift toys use a clutch diff.
Clutch diffs come in locked ratios and will always output at that ratio. Meaning they can swing the rear end out and keep it there. As I explained earlier, a helical diff does only what it needs to as much as it needs to. Meaning if you turn off your DSC and attempt to forcefully swing the back end out it will. But the diff will constantly modulate depending on the power you apply to it vs simply forcing a gated ratio to both wheels.
During a prolonged drift, the helical diff would send more and more power to the outside wheel until the inside becomes fully loaded and the outside spins freely. It would then act like an open diff. So if drifting is your hopeful lot in life with the E46, just swing for the locked diff. I'm not saying that the helical can't drift. But it's not what it is designed for.
For road course or Auto X you'd be hard pressed to fault it. The very design that makes it a lesser choice for drifting makes it the perfect choice for road course. A helical setup tends to be very neutral on both turn in and mid corner vs a locked set up and extremely grippy and predictable.
Okay but I don't drift: Weeeelll then, WELCOME!!... To your new rear end. Where this diff really shines is at your car's limit. Never before have I been able to push a car so much at it's limit and have it telegraph that limit to me so well without having to strap into a five point harness and knock the dust off my nomex and helmet. The disadvantage to a proper race car diff, read clutch, is that if you are inexperienced and you unknowingly push a car to it's limit, it'll make you meet your back end faster than you can blink. This diff is a different animal.
When I take the car to the limit with the DSC off I can feel it working. It allows you to correct your line and steer with the throttle while assuring you that it will let you know loooong before you step out of line. The speed at which I can enter a turn and carry though it is surprising. You can feel the power going where it's supposed to and know that it's not simply being wasted. On a road course, full track, or Auto X course the rear end feels sorted and capable. You can left foot brake and keep the power going with the car ready to blast out of the corner exit. When you come into a wide corner a little too hot and start to go wide, modulate the throttle a bit and the car works with you to step back in line instead of choking out one wheel while wildly spinning the other.
On a back road such as a mountain pass or anywhere things get twisty, the ZHP suddenly just makes sense. So it doesn't have a barely legal race engine and the stock gearing seems kinda long for some people. Drop it in third and imagine you're at Monaco or the Ring and rest assured that the car's rear end is actually using the power being sent to it. Sweepers and switchbacks suddenly become areas where you learn to get on the power a bit sooner and clip the apex a bit tighter.
I am in NO WAY advising you attempt to set a new time at your local twisty bit of road. But we all have our favorite roads where the speed limit allows us to have a bit of fun in the corners. And an LSD just adds to the experience.
Maintenance: Umm.. None.. Install it, use whatever fluids BMW or your specific manufacturer specifies, aaaaaand forget about it.
Reliability: This diff is one of the first things the previous owner had installed after he bought this car in Germany. A lil under 9 years and 90k miles later and it is still holding up with zero issues. It gets beaten at weekend track days and coddled to work on Mondays with nary an issue.
Quaife Customer Service: Having purchased the car with this diff installed I have no purchasing experience with them. However, their reviews are overall very good.
Summary: If you're making your ZHP a hardcore track day / weekend race toy go buy a proper clutch differential with a proper ratio to match your needs. If you just want to tighten up that back end for your daily driving and on your weekend track days or on the way home from work, I highly recommend the Helical setup. It won't break your wife's neck when it engages and won't try to kill you when you reach the limit. And at the same time, it compliments and enhances your daily drive. The car feels sorted and confident in it's actions and the same feelings flow to you as the driver as well.
If you have any doubts then PLEASE take your time, do some research and decide what it best for you. But with a few power mods and some time to learn the car, these things can be scary good fun.
Thanks for reading and have a good one guys.
*all vs examples for this review were for clutch type vs helical LSD. Torsen is roughly the same as a helical so the idea pretty much carries over. If for some reason you're unlucky enough to have a viscous LSD...well... I forgive you.*
Link to Quaife site. I am in NO WAY affiliated or sponsored by them..: http://www.quaifeamerica.com/whatever-homepage.html
*updated info*
On the US site there is a FAQ where they address that issue and their statement is as follows:
"I don't see an application listed for my vehicle, what can I do?
[I]Whether you are looking for an ATB Differential, close ratio gearkit, quick steering rack, or all of the above, we specialise in making limited productions on a custom basis. With many differential production runs of only 30 units, and gearkit productions of as few as 10 kits, Quaife can provide small companies and race teams with custom made driveline products built to their own, unique requirements. If you are an individual looking for one part, the first thing to do is to contact us! You may not be the only one looking. Many new applications have begun with a single phone call. After that, it would be a good idea to seek out fellow enthusiast owners that share an interest in your same vehicle. You may be able to gather enough people together to get a small production started.
Give us a call, you got nothing to lose . . . and performance to gain!"
:end quote.
Now on their UK site they still sell the E46 specific diff as well as offer a link to an endorsed BMW performance garage in the UK.
Quaife UK link: http://shop.quaife.co.uk/quaife-bmw-...46-330i-manual
Birds BMW performance: http://www.birdsauto.com/product-inf...-conversions-0
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