Sam's build thread

[sambb]

Thanks Gary. That's the best run down of RWD handling I think I've ever read. Now I know that I didn't have a hope in hell of getting my Escort to handle all those years ago.
So the Nulon recommendation with the oil I just wanted to check that's applicable for something that is run on the street too ie is that an oil to be chucked in post break in or good to go straight away. My Kaaz is the Super Q version that has treated plates from the factory. Any reason the oil you suggested wouldn't work the same with those plates? I ask you because I know what Kaaz will say. And do you still need to run friction modifier if you run that oil or does its use become null and void.

[metalhead]

I have to say it confuses me too... I understand what you're saying, but why wouldn't you just use a one way clutch LSD so it is unlocked on corner entry and locked under power out of the corner, without having to worry about making the inside rear lift on corner entry and plant on exit? Is it purely a cost and/or durability issue? Seems like you're compromising contact patches to get the diff to work as intended?

[Sydneykid]

Thanks Gary. That's the best run down of RWD handling I think I've ever read. Now I know that I didn't have a hope in hell of getting my Escort to handle all those years ago.
So the Nulon recommendation with the oil I just wanted to check that's applicable for something that is run on the street too ie is that an oil to be chucked in post break in or good to go straight away. My Kaaz is the Super Q version that has treated plates from the factory. Any reason the oil you suggested wouldn't work the same with those plates? I ask you because I know what Kaaz will say. And do you still need to run friction modifier if you run that oil or does its use become null and void.

We run it straight out of the bottle. We sent the KAAZ LSD specs to Nulon via their chemical engineer for him to recommended the oil for us to use. He already had the spec of the transaxle (it's a close ratio gearset but uses OE syncros) so he selected the oil that best suited both.

Cheers
Gary

[Sydneykid]

I have to say it confuses me too... I understand what you're saying, but why wouldn't you just use a one way clutch LSD so it is unlocked on corner entry and locked under power out of the corner, without having to worry about making the inside rear lift on corner entry and plant on exit? Is it purely a cost and/or durability issue? Seems like you're compromising contact patches to get the diff to work as intended?

The problem with a one way is that they all have a delay between power application and locking, whereas, say, a 1.5 way already has some locking, hence much less delay in response. It's also pretty rare to have a simple transition from power off to power on, there is almost always some playing with the throttle. That means locking and unlocking of the diff which is unsettling for the car (and the driver), so we try and minimise any nervousness. To add to the diagonal weight transfer, almost all of my drivers use the ripple strips, a couple of them aggressively, so 2 wheeling is not unusual. Also with a 1.5 way it helps under braking to limit the inside rear wheel lock up.

A lot of drivers prefer a spool for those reasons, they are always locked, so they never inadvertently change the attitude of the car (by locking and unlocking). Plus it's impossible with a spool to lock just the inside rear wheel. It just means the suspension engineer has to work harder to get past the propensity for turn in understeer.

That's production based cars with lots of engineering and numerous modifications to turn them into a race car. But in the end they are still full of compromises. Unlike say the F3 which is a designed from scratch race car, not a lot of compromises with it. We run a 1.5 way viscous in it, the only viscous I have even had any success with, because the driver likes the gentle progression when compared to the clutch pack many others use. Making the driver comfortable to live on the limit is the most important part of my job.

Cheers
Gary

[sambb]

Alright so I can get my hands on a brand new 114mm ring gear and pinion: 61/18 , 3.389:1 final drive.
The stock ring gear and pinion is 62/17 , 3.647:1 final drive.

see: Stock gear ratios and final drive?

I was hoping I could get the same or higher final drive but this one that is available is lower, so I'll have to think on it. Looks like in that list (FD) there's a 70/19 3.684:1 which'd be ideal or maybe the 63/16 3.938:1.

A stock 205/45/16 is a 590mm di. The 215/50/15 I track are probably bigger than a street tyres 597mm di, so I'm already a bit lower there and don't want to add to that. Think i'll keep looking. Or maybe machining the existing 113mm is the go after all. thinking........

[Sydneykid]

Alright so I can get my hands on a brand new 114mm ring gear and pinion: 61/18 , 3.389:1 final drive.
The stock ring gear and pinion is 62/17 , 3.647:1 final drive.

see: Stock gear ratios and final drive?

I was hoping I could get the same or higher final drive but this one that is available is lower, so I'll have to think on it. Looks like in that list (FD) there's a 70/19 3.684:1 which'd be ideal or maybe the 63/16 3.938:1.

A stock 205/45/16 is a 590mm di. The 215/50/15 I track are probably bigger than a street tyres 597mm di, so I'm already a bit lower there and don't want to add to that. Think i'll keep looking. Or maybe machining the existing 113mm is the go after all. thinking........

As with most VW's the gear ratios are a pretty good compromise for road and track. The taller (lower numeric) diff ratio may help with excessive wheelspin in first and give a higher (theoretical) top speed. Other than that it gets very track specific, in fact corner specific. For example if you have corner that is taken at a nice rpm, so the upchange is not in the middle of the corner but at the exit, then going to a lower (numerical) diff ratio may well be not a good thing. Conversely if you have corner that is taken at a high rpm, so that the upchange is in the middle of the corner, then going to a lower (numerical) diff ratio may well be a very good thing.

In summary, if 1st gear wheelspin a problem then a (numerically) lower diff ratio maybe of benefit. That aside, with a torquey turbo car, decent gear ratios and a wide rpm band, I don't see an 8% taller diff ratio being an issue. Conversely if it's a dog of the line , first gear is too high a ratio, has a propensity to bog down then the taller diff ratio won't help.

FWIW I doubt that I would notice the 1.2% difference that a 597 mm tyre makes compared to a 590 mm tyre, even on the data log.

Cheers
Gary

[sambb]

Coming home last night I would do 50kmh at 5000rpm in 1st and 80kph at 5000rpm in 2nd. Ive always liked the spread off gears but the final drive has felt a tad too punchy for the torque delivery of the engine. I guess I figured that if I went to a higher ratio final drive that then 4th would become a gear I could actually use at say wakefield or south circuit but after having a proper think I'm starting to think the opposite. Its always been a case of 1st gear being ridiculously short having to really manage wheelspin and get it into 2nd in a flash at the hillclimbs. 2nd is the same kind of deal and then 3rd is long enough that it becomes a really flexible gear.eg across the top at Bathurst mountain straight hillclimb I didn't need 4th and 2nd was wheelsping galore coming out of the cutting, wakefield was all done in 3rd except for hairpin of course and I was starting to keep 3rd at the fishhook as I got my head around the flow of the track after a while. At Fairbairn though I only just needed 3rd across the top and at Ringwood would do the whole track in second. Yeah I've been going over it in my mind thinking that it would probably benefit the hillclimbs to go 3.4:1 as 1st would become a more effective gear and the torque in second can be used anywhere. I'd be in a better part of third for Bathurst, and at Wakefield/south circuit the car would still have the torque for 3rd to work great and it wouldn't really change much there. At least at Huntley I wouldn't be in two minds about needing to go back to 2nd or stay in third at the esses….2nd would be clear there.
If I ever did go to 225/45/16 say for bigger brakes, then that would jump up to 609mm plays 597mm of the 215/50/15 - surely I'd feel that in conjunction with the 3.4:1 wouldn't I? But yeah if keeping the 215/50/15 I think I'm coming around to the idea that a 3.4:1 would actually improve things.

[Sydneykid]

If you ever get to the 225/45/16 I'll have a supply of used ones for you, but they won't be 609 mm, probably closer to 600 mm

First gear ratio is pretty short, especially for a lightweight turbo car. Plus you have plenty of torque, that also has a wide rpm spread, so I think it should be OK. Maybe even better than what you have currently.


Cheers
Gary

[sambb]

Yep I'm thinking ill go with the 3.4:1. I'm struggling to think of where it could hurt me and Im only coming up with benefits. I dont think I ever intend on some massive turbo either. Gt2860 would be about the max I'd consider so I'll always have gobs of low down to drag me around, so I really dont think the ratio change will be an issue now. Also that'll mean a nice shiny brand new set of gears and bearings which is peace of mind too.

Gary since you run the Kaaz in the Civic, do you service them or can you suggest a diff tech who'd be good at deciding on the best plate arrangement in the diff once I get the plate kit organised?

[Sydneykid]

We have a diff guy, but KAAZ have manuals for their LSD's which explain the plate orientation required to achieve the various results. From memory it's in table form, pretty simple to follow. It's just like lego, determine what you want it to look (work) like and then follow the assembly instructions. No magic going on.

A how to video (like a pancake stack)
YouTube

KAAZ Differentials - Lock Adjustment Instruction Sheet - Co-ordSport

Great KAAZ LSD Kits - MDSpares Pty Ltd
There's a clutch size orientation guide in PDF form, just follow the link

Cheers
Gary