Urq project

[fish]

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[diesel des]

I have the engine and gearbox out of my urs4 at the moment getting it ready for a ring trip, eg turbo upgrade from efr 6758 to 7163, clutch rebuild after it got some oil on it, breather system re design, baffled sump fitted and timing belt job. So the urq has had to take a back seat. It will be a few weeks until I get back to it.

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[diesel des]

Bit of an update. I found the base settings in my ECu had the spark timing 6 degrees retarded so this seems to be the cause of the power being down. Now I have reset vems power is definitely up. Way up. I need to get back to a rolling road to fine tune but it's going the right way.

[diesel des]

As a result of the increase in power the stock rear diff exploded. So I got a stock 7a diff and had it sent to jpr at Silverstone. He is building it up with a gripper plate LSD. I haven't driven a quattro with a plate LSD so it will be interesting to see how it goes.

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[diesel des]

Stock diff removed. It seems like there was a second hole hid behind the rear mount. The spider gears are totally gone. They fell out in pieces.

Anyhow new diff fitted with the gripper LSD. I tested the car over a road where it would of spun up a rear wheel round some tight low speed bends. Not an issue now, as the car wants to power oversteer. Plan is to get back to the rolling road this Friday for some fine tuning.

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[S2central.net]

Wow - thats some dramatic failure... I had never heard of that aftermarket part though - good find if it is up to the mighty level of torque that you have.

Are you also running LSD in the front ?

[diesel des]

Gripper have been making plate LSD for years. Handy they are made in the UK and good to deal with. I know of a few rally men that run them in escorts etc. No I'm running a stock open front diff in the 03a gearbox and it has the fancy rear biased center diff.

What's your plans for diffs and gearboxes in the s2 paul?

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[S2central.net]

I am swayed towards RS4 (0A3) main gearbox due to its higher strength and the rear biased centre is nice. I think there is a wavetrac ATB front diff available for that. For the rear I was wondering if the RS4 rear diff could be made fit - its still open of course but would be beefier that the S2 item - never looked at one to see how much difficulty required to make one fit. The gripper item is a new option for me. If you can't easily break one then its going to be tough enough for the rest of us ;-)

[S2central.net]

I also haven't put a moments thought to any propshaft modifications for the RS4 'box - apparently its been done before in an S2 so thats always good.

[Error404]

ABY shaft needs shortening 28mm. I’ve posted all the info on the forum before, plus my conversion kit is available to order

Good work on grenading that diff Des, was that a hard launch or just general abuse from shed loads of torque?
Interested in how you get on with the plated diff Des. I’m sure it will transform the drive, certainly the rear Torsen does. Be good to get your feedback on road manners. Did they suggest the ramp angles / preload settings I’d have you specced them?

[diesel des]

ABY shaft needs shortening 28mm. I’ve posted all the info on the forum before, plus my conversion kit is available to order

Good work on grenading that diff Des, was that a hard launch or just general abuse from shed loads of torque?
Interested in how you get on with the plated diff Des. I’m sure it will transform the drive, certainly the rear Torsen does. Be good to get your feedback on road manners. Did they suggest the ramp angles / preload settings I’d have you specced them?

The diff exploded when demonstrating a launch with my dad in the car. I really should of had the diff locked I suppose. The LSD is setup as 40 deg acceleration 60 degrees overrun ramps with 120nm preload. It's what they suggested when I told them the car would lift a rear wheel in tight bends and was used mostly for track day with some on road blasts. I put about 80 mile on the car today over some very twisty roads. Paul you will know what I mean when I say spelga damm.. The diff really makes the car want to power oversteer out of bends even in third in the dry. I like it. I don't notice the overrun ramp on the diff at the moment to be honest. It never just lit up 1 rear wheel like it used too. It lights up both and floats out of a bend nicely. The rate it puts speed up is simply nuts.

Disadvantages just seem to be some noise when doing tight turns on tarmac, not bad but noticeable. Nothing like the noise and vibration you get when turning with the stock diff locked. I'm going to stick some temperature indicators on the caseing of the diff and gearbox to record peak temperature. After the days driving I could hold my hand on it but only just, so about 60 degrees. I'm running a full synthetic 75/90 in it. After a track day it's likely to be much hotter.

I do have a prop shaft type vibration that I need to look at. I need to get my dad to drive the car on the ramp and hold a steady 60-70 while I look around. Might need to realign the center bearing or adjust the length of the spacer I use to make the urs4 shaft work.

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[S2central.net]

The LSD is setup as 40 deg acceleration 60 degrees overrun ramps with 120nm preload.

I wish I understood that - betting I am not alone there !

Spelga would be a fun test route alright.

[S2central.net]

On the question of heat - I found this OE bolt on heat-sink for the rear end of RS6 almost randomly - could be worth cloning if you see hairy temperatures on track.

https://audi.7zap.com/en/rdw/audi+rs.../5/500-500010/

I was trying to see if other beefy 37/9 rear diffs existed that might be easier to source than OE B2/B3/B4 style - whether they can be easily accommodated on a B2/B3/B4 subframe is another matter, but that kind of fabrication for custom bracketry is easier than sourcing increasingly rare B2/3/4 rear ends.

Seems like things like the B7 RS4 run such an open diff and would be capable of high torque levels. There are ATB & LSD upgrades available on them too. Seems like they have no locking mechanism either (unlike the B2/3/4 generation) as there is external electronic involvement with EDL trickery by way of ABS controller momentarily braking the slippiest wheel so that torque can transfer to the other side.

[S2central.net]

Like this one - there is actually a C5 RS6 rear diff on Ebay.ie right now - it is 37/9 but the mount points look different to me compared to B2/3/4

[Error404]

The diff exploded when demonstrating a launch with my dad in the car. I really should of had the diff locked I suppose. The LSD is setup as 40 deg acceleration 60 degrees overrun ramps with 120nm preload.

Interested in how you get on with it, seems quite aggressive on the overrun side but I’ve no experience other than theory on the setup. Given the weight distribution I expected to be more like 40/75 or 40/90 so it acts fairly open on the brakes. I’m Sure those guys know what they are doing though
If I grenade my rear Torsen I think I will try a plated diff as I like the idea of the adjustability. Keep us posted