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My sensible fast road S15

sibbers

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I was going to post this in the welcome thread, but it seemed like after 3 months that might be milking it a bit.

Anyway, after focusing on tasteful handling mods and renewing aging parts to make the car feel modern again I thought I'd see what happens with a headlight restoration kit. Turns out, this was a great idea!

Also running in my Nismo 1.5 way which just keeps getting better and better. Very polite with preload setting at 'low' and no noise what so ever (some skipping on tight corners as its runs in, but this has nearly faded)... Loving ownership of an S body so much right now.
 

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sibbers

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Spec list...

  • HSD Monopro's with 5/4kg spring rates (still have 7kg springs)
  • Whiteline Anti Roll Bars front & rear
  • Subframe refitted with Whiteline urethane bushings pressed in
  • Rota Grids (17x9 ET25) with 235/45/17 Goodyear F1s & 245/45/17 Hankook V12 Evo
  • Arches professionally rolled to suit wheels and tyres (no flare)
  • Nismo Combination Meter (speedo)
  • Retrimmed Leather Steering Wheel
  • Nissan Connect LCN1 from Nissan Qashqai / Juke with GPS and MP3 / Aux playback (looks OEM)
  • Full exhaust 3" system from turbo elbow, decatted with large silencers and HKS Silent Hi Power backbox (custom and very quiet during idle and cruising)
  • New genuine Nissan gearstick leather gaitor and Nismo knob
  • DEFI boost gauge in OEM location using original wiring (with new DEFI sensor)
  • Gizzmo EBC (brilliant thing)
  • HKS metal intake pipe (bigger diameter)
  • Apexi Induction Kit with extension
  • All new turbo gaskets, locking nuts, braided feeds etc.
  • Nismo 1.5 way GT Pro LSD (street setting, rather than circuit or drift)
  • Added new very low mileage S15 seats
  • Nissan Qashqai Stereo and GPS for OEM+ look

I think that's it. Could probably do with some rear traction arms and I still want to replace the dash but I'm pretty much there.
 
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sibbers

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Nismo GT Pro 1.5 way L.S.D review...

Thought I'd share my findings as part of my experience, looking for a diff, was working out what it would be like to live with, would it really provide the predictability I so desired over the helical/torsen unit and if I were to buy second hand (or new) then what did I need to look out for. Lots of talk of pumpkins and half shafts without actually seeing what's what resulted in a fair bit of confusion so I'll try and clear some of that up for sake of those on a similar quest searching for info in time to come.

What's the benefit..?

Mainly predictability. Knowing how your car delivers power to your rear wheels is one thing, but when it behaves as expected in a predictable way you will drive with a lot more confidence and this results in a much more enjoyable drive, providing this behaviour outweighs the drawbacks of having a clutch diff. Aside from this, with a decent LSD your car will be truly 2 wheel drive - most other diffs, be they open, viscous or torsen will only provide power to one wheel, or if both then with more power going to one wheel than the other - this results in lost energy if your wheel spins and if not then you have a car that pushes from one side (making swapping ends a thing). I also wanted to be reassured that a clutch diff wasn't solely for the benefit of drifters - it's not, although during the break in period you might wonder if that's true.

What are the drawbacks..?

Maintenance - you will need to do oil changes like you would with the engine. Changing the diff oil is a bit of a pain, but most diff oil (such as Motual 75-140w Fully Synth gear oil - used for the Nismo unit) has a tube you can jam into the filler hole and you can squeeze it right in. As you need less than 2 litres, you can afford to waste some. The alternative is use a hosepipe (don't bother trying) or a pump. Noise - Some diffs can make some clocking noises and make your car sound broken. In the case of this Nismo unit, it makes no noise and appears to operate completely silently but Kaaz and Cusco units may be different, or perhaps with different gear oil it would make some noise. Not sure. Drivability - On tight turns your inside wheel grips until eventually something gives, normally this means the inside wheel will hop up in the air and until it does this it will push back on the suspension which makes the car bounce a bit. The stiffer your car the less of a drivability problem this will be. During run in (the first 1000 miles) medium speed corners will cause the diff to lock without the inside wheel bouncing, so you will feel all the suspension jostling to give up the energy generated but this goes away. Your car will be prone to understeer under power, however you can drive through this and once you do you will find there is quite a lot of extra grip. Life of unit - it won't last a lifetime like the helical will.

What's wrong with the standard helical LSD..?

For me, its unpredictable whenever conditions are less than ideal meaning lost confidence during high speed cornering or acceleration (or both). The helical is very good as a daily driver with little throttle interference over the steering of the car, but when cornering, because so much power will be delivered the one wheel there is a push form the rear that causes turn in which can result in snap overseer - fine in the dry or when the road is smooth etc, but in the wet, on bumpy roads, when there are drains, diesel or you car lifts a wheel you can end up losing power, or experiencing undesired turn in and then experiencing a tank slapper. Open diffs do this a lot, but they are consistent in their slightly nervous behaviour, helical diffs are much better except for that time they surprise you.

What do I need to know to ensure a clutch diff fits my car..?

Assuming you have an S15, you either have a spec S or spec R. This means you need the standard housing that your current diff is within because it has a speed sensor in it, unlike the other R200 type diffs i can think of. Certainly S13 and S14's anyway. A Nismo unit is supplied with the half shafts that you need so the internal pumpkin (the main bit in the middle) doesn't really matter - you just need to make sure it has 6 bolts where it connects to the drive shafts that power the rear wheels. Kaaz units (AFAIK) are specific to the half shafts you already have so make sure they fit. The easiest thing to do would be buy a second hand S15 diff complete in it's housing and swap it with yours... This is what most people do so they go very quick and you need to consider the final drive ratio of the crown gear - for us, that's 3.69 which you should retain (if you understand you want to change this, then you don't need this guide). If you want to buy the internal parts (which is how it works when buying new) you can re-use the crown gear (and bolts) but fitting it should be done by someone with the right tools as backlash needs measuring (how well the gears mesh together) and potentially adjusting with shims (meaning you should have some before fitting) as well as pressing in bearings and doing up bolts very tight.

What's it like..?

My diff has an adjustable preload setting which is set to soft (60/80/100%) as that is the advice for street/circuit driving... 80% is for circuit/drift and 100% is pure drift, and probably behaves like a welded diff under acceleration. If you wanted to drift though, you'd probably be better off with a 2 way (so you can clutch in and have it open up) or go with a welded diff (cheap, but clutch doesn't get you out of trouble - you are always committed. Very predicatble though, so not as scary as it might sound - just crap for driving slowly).

Pretty good so far, and improving all the time. I think buying a second hand one would probably be excellent as you wouldn't need to run it in. Running it in consists of driving slowly round bends and trying to make sure you give equal consideration to each direction. Running in the diff stops the inside wheel from skipping on the inside wheel during tight corners or under heavy throttle. I followed the Kaaz break in procedure which meant going to Sainsbury's (with the wife in the car) and driving slowly round in figures on eight, accelerating on the straights then clutching during the turns. I did it at night, but car parks are filled with weirdos and stoners at that time so they were all watching me get dizzy either wondering what hell was wrong with me or getting paranoid that I was some kind of trick/bait :wack: Did this for about 30 minutes and decided to head home, spending the rest of the break in period doing what nismo advise which is normal driving in twisty roads so I avoided motorways for the next 300 miles or so.

So now the car skips on tight turns which probably looks a bit weird to some people, but tbh I haven't seen anyone actually noticing it yet, and during driving the car really pushes forward including during cornering. It does result in a crap load more grip and as it's running in (I've done 850 miles now and had an oil change after about 600) its becoming more and more normal feeling in that it doesn't skip on tight corners as much and doesn't bounce the car either. Clearly its allowing more slip before it locks. When it first went on, at this preload setting I'd say it got about half a turn of the outside wheel before it would start to lock - now it's a decent amount and although it's very noticable, its totally fine for a daily driver with perhaps maintenance being the main thing that should put you off. And cost. the thing to be aware of here is it takes a long time to run in, but after 1000 miles I think I'm done.

During spirited driving it absolutely makes things more predictable. In the wet I feel loads safer. After the careful running in period that you tend to do with an expensive thing you care for, I decided I wanted to know what it was like when getting it sideways and to be honest its exactly how you'd imagine. It locks up and does nothing more than that, so while i was pleased it was no more than I had hoped for. If it didn't do this I would have been disappointed. Feels like a welder. However, the bit I've really enjoyed is the bit that doesn't feel like a welder, which is coming off and on throttle and getting a predictable turn in so you can switch directions quickly if sliding or, more fun for me, just driving near the limit of my ability - like a go kart, when trying to get round a corner as quick as I can, the back grips and grip and grip, then as you increase your speed and the limit of traction start be overcome, the back shifts out and you determine this with more or less throttle... kinda like early learning center drifting. Or racing :)

Its a wonderful wonderful upgrade, and although at first I thought it was only for some as it wears in I'm beginning to wonder if someone like my wife would even notice it's there. It's that polite. I'm keeping the helical unit for now, but I may decide to sell it on as if I ever do sell the car I'm not sure anyone else would be opposed to it at all. Unless they had experience of a much more aggressive clutch diff... but after a drive I think they'd be cool.

I've posted without really reading this back but I'll update it if I think of other things I've neglected to mention or learn as the diff breaks in. Hope it's helpful and please point out any glaring errors or useless bits! Be aware this is not for people who have clutch diffs as much as those who are a bit frustrated by the helical unit.
 
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Awesome write up! Running it in sounds fun...lol!
Been considering a new diff a couple of times, these sound interesting.
 

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Cheers! I'll give it a read and fix errors and maybe add picsto try and make it a bit more useful. Breaking it in at first was a real chore. At diary I thought I had to do donuts, but couldn't find anywhere but enough to do that and remain socially acceptable so I went home and left it for another day. Lucky really because I could have ended up doing the opposite of what you're meant to. That said, the last couple of hundred miles have been great fun. And accelerating in first and second is waaaaay faster with the extra grip. Big cheesy grins for me :D
 

tooley

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1.5 way diff is perfect for a fast road car.

I run an OS Giken 2 way in my competition car. It was used when i had my car as a daily too and was great but it would also lock up on hard braking which was not the best haha! escpecially when the outside lane on the motoway gets a group slam on the go! ive stopped sidways a number of times haha.

1.5 way wont do that :)

Car is looking good!
 

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Cheers, and I totally agree now I've experienced it in a car I use every day. I was a little nervous after doing a bit of reading elsewhere though - there were loads of snippets of info, and comments in forums that made me wonder if maybe I was about to modify my car too far, which is what I did to my first S13. Turns out it's totally better :)

That OS giken sounds like fun - straight in for the best one. Good work :)
 
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S15AK

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I've got the GT pro 2 way diff in mine, and its been spot on even as a daily drive or on track :)
 
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Brilliant read mate thanks for that, really considering getting one myself as the helical has given me a few odd moments!
 
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1.5 way ,along with uprated arb , is one of the best street handling mods you can do. Love how you are settin about this 15 dude! Great work so far
 

sibbers

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1.5 way ,along with uprated arb , is one of the best street handling mods you can do. Love how you are settin about this 15 dude! Great work so far
Slow to reply, but yeah this thing is just the best car ever. Been having so much fun and the diff has really settled in. Drove to Belgium and then down to Donzy in France (right in the middle) from my house in west London and I only used 1 and a 1/4 tanks of fuel!!! Crazy.

Handling is so good and inspires so much confidence. I have so much grip I can just belt it everywhere, and now that I've done a bunch of work to it to tidy it up and get it suited for our UK roads the only thing it can't do is beat the really fast cars on the motorway now. That said, I've been keeping up and even getting past my mate's Noble GTO M12 which makes 425bhp and is basically a proper racing car.

This is thing is a beast. Can't believe more people don't have these, but I'm well glad. I get thumbs up all the time and when the wife's driving people go nuts. A girl in an S15! Haha. Well funny.
 

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Well, I'm no longer the owner of this beast. Got her to such a nice state where she was perfect for the roads. Diff was easily the best mod, and power-wise she was close to standard but in the end the gearbox self destructed under moderate power. No abuse to speak of, just a weakness resulting in 3rd/4th becoming next to useless followed by crunchy grinding. I've cut my losses and passed it on to someone who's done loads of work on her already and has a very high standard so it won't end up being bodge wagon covered which I'm pleased about. OS Giken 5 speed due to go on, should be absolutely brilliant. Also, knowing the new owner it will be making 400hp+ before long.

Heartbroken!
 
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