Urq project

[diesel des]

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

There is a track day next month so hope to find out how it behaves then. Obviously on the road this car is somewhat limited. I have to say I can't feel much going on on overrun, maybe if you didn't rev match while down shifting things could get interesting.

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[diesel des]

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.

An interesting alternative rear diff could be a Nissan skyline unit as some are 4.111:1 and have loads of LSD options. Obviously need custom brackets and shafts etc but definitely an option.

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[diesel des]

Something like this https://rover.ebay.com/rover/0/0/0?m...2F263041415530

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[david1980]

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

Completely off topic but do you think the v8 torsion would fit in a fwd box?

[diesel des]

I think some have fitted it to the front after some custom machine work. It's not the strongest of diffs, so depending on usage you might be better with a drop in quaife ATB diff.

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[S2central.net]

An interesting alternative rear diff could be a Nissan skyline unit as some are 4.111:1 and have loads of LSD options. Obviously need custom brackets and shafts etc but definitely an option.

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Wash your mouth out ;-)

[diesel des]

Wash your mouth out ;-)

Yep, but you just can't ignore the availability of the overnight parts from Japan... Lol. I by the time you have made the adaptions to fit another non direct fit differential you could of payed for a bolt in upgrade for the s2/7a diff and once the stock Audi spider gears are out of the equation they have been proven to hold big power even during drag racing. If it ain't broke don't fix it.

Anyhow car is booked back in on the rolling road tomorrow so we will see what it does.

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[diesel des]

And what it did was melt down. I have no compression on 3, 4 and 5 cylinders and poor compression on cylinder 2 at 4 bar and over 10 bar on cylinder 1. Basically the map I had on it and have been blasting about on was pinging at 4 k rpm. I couldn't hear it on the road, but on the rollers with my det cans it was very clear. It made 568bhp on the first run. I removed timing and added fuel but it wasn't lean, about lambda 0.8, but the ping got worse on each run. Then it went off a cylinder, and 3 plugs had melted. I replace the plugs and straight away it wasn't right, still misfiring and pinging. So I quit there and tested compression. Then got a tow truck home. Maybe third engine build lucky?

The rpm scale is wrong on the graph btw. I looked in with a bore scope and I can see pits on the pistons that had damaged plugs. I can't really see the bores very well or the head. Anyhow it's a engine out and strip down job.

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[Tom_]

Sorry to hear that Des I hope that car will be running soon and with a less money effort

[Error404]

Bummer Des
Is your timing drifting? IIRC you said you checked the static timing and it was out so you advanced it? Just wondering if you have a drifting crank position trigger.

Anyway, hopefully just fried pistons/rings and the rest is fine. Sure you will be back up and running soon. Have a beer now

[diesel des]

Thanks guys. Static timing was off just due to the exact position of the pin on the flywheel and the sensor position on the TDI block. It was just the offset that needed adjusted in vems to ensure zero was tdc. The timing then sat rock solid on the timing light. The map I had been using looked fairly conservative, but perhaps the engine breaths better than I thought so timing was too advanced in the mid range it would appear. It was based on my vems map from the stroker in my urs4 with a smaller turbo and cast manifold and stock cams. Anyhow I will open it tomorrow and see what mess is in there.

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[Rikki Kitto]

Gutted for you fella hope it's not too drastic

[S2central.net]

Gutted for you fella hope it's not too drastic

Ditto that - very annoying indeed Des. Time for some beers I reckon. Lesson learned and move on I suppose when you have the mindset to rebuild it.

[simons2]

That's pants

[diesel des]

Not good.

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