2 Way a virgin's experience

[Magpie]

It all started with a comment about inside wheel unloading at QR on the sprint circuit. From this a chain of events Automotive Plus installed a 2 way diff into the MX5. This was NOT on the list of things to do in 2016, rather the plan was to make minimal changes and work on the driver. It should be noted before this my plan was working and times reflected this, finished 9th fastest in round 1 of QR Street Sprints, something never done before.

With the words of Captain Ramius echoing in my head "It reminds me of the heady days of Sputnik and Yuri Gagarin when the world trembled at the sound of our rockets. Now they will tremble again - at the sound of our silence. The order is: engage the silent drive" I approached the weekend at Morgan Park with all the confidence that every parent has that their child will grow up to be a doctor, astronaut or another Mother Teresa. How wrong I was....

After the first run on the Saturday I found out that a smoke screen maybe good for hiding from the enemy, but BAD on a race track. No need to go into the rest of the details they are public knowledge Anyway, made it back to the track for 2 runs on Layout E.

OMG, the car sucked BAD understeer everywhere, brake points all screwed up, nothing felt right. This was similar to attending Lakeside with an aggressive alignment that the car had never been set up with, very scary to drive! I persisted with the handling and just made it worse. In the end Saturday finished, car loaded onto the trailer, confidence shattered, ego destroyed and my sanity questioned.

After dinner with good company, where I was surprised to find a person that used more sarcasm than me, had a sleep ready for Sunday.

Arrived, unloaded the car and went about normal track things, checking oil/water/leaks and tyre pressures. Notice that the tyres were higher than their normal cold pressure. Adjusted accordingly, added 6 clicks to the front dampers.

Time to hit the track, damm that 2 way makes some chatter driving it slow is not fun... Took a completely different approach than on Saturday, went easy out and 'felt' what the car wanted to do. Came in adjusted pressures based on comments from SDT. Rinse repeat another 3 times.

Then onto Layout E. First session went at it like a bull in a china shop (mythbusters debunked) and the Saturday issues came back. Next session changed to early braking, no trail breaking get everything done in a straight line, nail the apex and then 100% throttle. OMG this is fun, only change was a PSI in the tyres and the drivers thinking. Everything started to fall into place, no fast laps yet, but so much more confidence. The big spin at T2 the exception.

Slug_dub jumped in for a few passenger laps at lunchtime and, like others, commented that I brake a lot earlier than he does, further I enter the corner slower BUT at the apex my exit speed is a lot faster.

After lunch started to push a little more, still everything in a straight line, BUT braking later (getting used to the VERY HIGH initial bite of the W6.5's). Even got to the point where could enter T1 in 4th and get the gear change to 3rd in before T2 (the cause of the big spin before lunch).

Whilst not setting the world on fire with my times, over 1 sec was chopped off my previous PB on Layout E. Looking at the logs I was never exceeding 1g of braking/cornering so this alone shows that a lot more time can be found!

What have I learnt about a 2 way from my first experience?
1. Can make any part of the corner understeer
2. Requires a high level of skill in trail/threshold braking to get the most out of it due to the inherent understeer the 2 way causes.
3. Under deceleration the car has a tendency to go straight ahead as the rear wheels resist the change in direction
4. Car resists turning under brakes
5. In a corner when the arse end starts to rotate turn the wheels where you want to go and nail it. This is not the fastest way around a corner but when you have stuffed up lap up makes for some fun

Final comment is from Keeley Motorsport who were out helping set up SDT's track cars, that was, a 1.5 way maybe more suitable.

Do I agree? Can't say as I'm still a 1.5 way virgin However, provided the brain is engaged I think the 2 way was a good move. Will find out on 10/04/16 at general practice and street sprints round 2

[hks_kansei]

from both reading and having dríven cars with LSDs this is pretty normal for LSDs of most forms, just that the clutch diffs are a lot more dramatic with it.

All I can really recommend is either seeing if you can have the diff setup as a 1.5 way (will allow some wheel slip under decel, helping turn in)
The only other option is driving style, where with a 2 way you can lightly accelerate during the corner to bring the diff into the middle zone where its not under decel forces, or accel forces (and thus, will unlock)



I noticed a little understeer in my car when the T2 was fitted, but only under power and frankly not that much. So the clutch diff (pretty much working like a welded diff during accel) would I imagine be a LOT more dramatic.

[Magpie]

I have now found that a torsen and clutch pack diff are polar opposites in the way they respond to driving style. I'm going to compare data over the weekend to see where the changes were and if there was an obvious change required.

I'll post some video of the Saturday afternoon.

[madjak]

My car used to have a 1.5 way clutch pack diff 1.6 diff before I upgraded / downgraded to a 1.8 torsen. I much prefer the 1.5 way clutch pack over a torsen as it suits my more aggressive style of driving. I find the torsen is better now that I've upgraded my suspension but it still makes the car feel soft under power. The clutch pack has a bite that the driver can feel, the torsen is more transparent.

With the clutch pack I found I could be on the power far earlier in the corner than the torsen, and also trail braking into corners was more stable, although I'm getting used to the torsen now. I could also skip kerbs without dropping drive. The negatives is that the car would understeer on any tight corner, but it just means you need to load and slip the rear a little to brake the bind in the diff.

A 2 way diff is far too aggressive for a track car and really only suits drifters who can throw the car into corners.

[Magpie]

The clutch pack has a bite that the driver can feel, the torsen is more transparent.

Agreed

With the clutch pack I found I could be on the power far earlier in the corner than the torsen,

Agreed

trail braking into corners was more stable

Need to work on this.

The negatives is that the car would understeer on any tight corner

AGREED

A 2 way diff is far too aggressive for a track car and really only suits drifters who can throw the car into corners.

Undecided

[Dan]

Takes a bit of getting used to, initially I throught my car was slower with my aggressively adjusted Cusco 1.5 but once my driving adapted to suit the diff things got better and faster

damm that 2 way makes some chatter driving it slow is not fun...

What oil are you running? The manufacturer's recommended stuff?

We had Castrol in mine at first which caused it to chatter/clunk like a demon at low speed.

Then I got some Cusco 80W-140 oil and put it in, no noise at all! You can still feel the diff at low speeds doing its thing but that's to be expected.

Sent from my SM-N9005 using Tapatalk

[pepejesus]

A 2 way diff is far too aggressive for a track car and really only suits drifters who can throw the car into corners.

Undecided

Have to agree with madjak, you're just going to understeer everywhere with a 2-way, then you'll spend time and money changing other things to try and band-aid this problem, making the car worse.

In my opinion in a low-powered light car like the MX5 it's all about maintaining corner speed. Slow in fast out is not the quickest way to drive these cars. Not saying this is not good general advice but in my opinion is not the fast way to drive an MX5. You make up more time coming into the corner than going out with a low power car like this.

If you watch videos from the really quick MX5/Miata drivers, especially those with stock power levels, you'll see they are really rotating the car on entry, usually while still on the brakes, not opposite lock type stuff but just so that you need to 'open' the steering a bit, then nailing the throttle right before the apex and maintaining the car's attitude through to corner exit. Big parabolic type lines, not squaring the corner type stuff. Watch Guran's vids for example - that is how you need to drive these cars quickly.

A 2-way diff will make this impossible. You want a 1.5 maybe even something close to a 1-way IMO. Or a Torsen...

But if you're doing the brake early in a straight line, late turn in, nail the throttle well before apex style of driving, then maybe it will work for you. It is just not the quick way IMO.

I do think you're crazy for changing the entire diff because of one corner on one lap at one track but as long as you're having fun...

[Magpie]

pepejesus I do crazy well. Only time will tell if it was a good idea. 2016 was not going to be making changes to the car and whilst the 'plan' has changed I'm trying to stay reasonably on course. No plans on spending money on band aids, the only planned change for 2016 was new coilovers.

There was no plan to change the diff because of just one corner. The feedback was to change line/driving style to eliminate the inside wheel unloading (on the one corner), this was the path I was going down. There have been other times when the limitation of a torsen had shown themselves but it was not change for change sake some thought did go into it.

By the time Sunday finished I was getting used to the way the car handled. More importantly I rectified some bad habits, especially not being at 100% throttle at the apex something I have struggled with. Slow in/fast out may not be the fastest, but as a stepping stone to brake less and later it is (at least to me) important.

Happy to be proven wrong, will find out on 10/04/16.

[bruce]

As you said, it would be a lot easier to work on the driver skills than throwing more money at the car. (All) cars are money pits.

[madjak]

I prefer fast in - fast out as the driving technique!

Magpie, if you can learn to drive the car fast with a 2-way diff you'll find that if you step down to a 1.5-way or any other diff for that matter the car handling will be much easier to control. It's not a bad way to bring up your driving skills and have to learn how to drive the car again. It will give you good depth as a driver.

I've never dríven a 2-way so maybe you can feedback on how the car drives when you get used to it. Maybe focus on some of the pluses of a 2-way... You should have excellent straight-line braking in the wet. The car will feel planted under any straight line braking and you might find you can wind the bias further rearward. I'm fairly sure long radius trail braking should be more controllable as the diff will want to hold the car straight, however I think there will be a certain traction point that once you pass it, the rear will want to step out on you. Finding that balance might be a bit tricky at first.

The key will be controlling the understeer when you're off the throttle and on tighter corners, and to do that I think you'll need to try to slide the car into the corner a little to break the grip the 2-way will have. This is where the "aggressive driver" style comes in as just turning in on a corner whilst off throttle will require more front traction that you can get to overcome the rear diff. So turn in will need to occur either when you're sliding the car a little or when you have the front loaded up under brakes.

Under power the diff is the same as a 1.5 way, so skipping kerbs, getting the car in the air and generally unsettled should be fine as any power will be immediately applied to the ground, unlike a torsen which takes some time to grip and transfer bias.

Most likely it will take a while to get used to so try and have fun. You might get a fair bit of practice catching the rear end of the car! If you can get your head around it, the 2-way should be quicker than a torsen if you can get the car to do the right thing.

[Magpie]

Happy to provide feedback as get used to the nuances of the 2 way.

This is from last year with SDT's instructor at the wheel (Torsen 2 and my weight penalty)


This is with the 2 way

[Ned Loh]

You may need to change set up to rebalance the car with 2 way? Springs sway bars?

Don't get on the power until you can stay on it. Braked too much/could have carried more speed?
Learn how to heel/toe

[Magpie]

Thanks Ned Loh.

[Magpie]

This was straight after the seals were replaced.



madjak looked at some of the data last night and in one section of the track I was faster (in general) than on the lap I posted. Surprise, the turn in was a bit earlier and more speed was carried to the apex, hence faster exit speeds.

Ned Loh, as stated I agree. In the past heel/toe was not working on the track for me (lack of skill). It is not a good idea to practice a skill badly, like left foot braking so it is on hold for the moment. I'm working on it, the same as braking too early. Will see how it tests in April and then tweak suspension/alignment if required. I make the BIG mistake of making too many changes at once before Morgan Park (diff, spring rates, ride height, rake). However wing angle and tyres were unchanged.

I think the 2 way is a positive, albeit the skill of the driver is lacking. Would have been great if Chris (SDT Instructor) was at Morgan Park as he has dríven my car through various stages of change over the past 3 years. Chris provides constructive criticism and does not hold back. Hopefully at the next Morgan Park day he can take it for a spin, without the weight penalty of me in the car.

Trying to keep this thread away from my lack of skill

[speed]

Mark, if you can drive or learn to drive better with the 2 way then you can drive any diff setup.

I think it was a ballsy choice and you WILL learn a lot from it.

Please keep this thread updated with your continued feedback.