Nurburgring diff ratio

[Andye]

Off to the Nurburgring in May and need to fit an LSD diff to my 318is anyway, so what ratio is best for track days etc? Engine is standard but coilovers and bigger brakes and poly bushed throughout.

Cheers Andy

[maxfield]

A 4.1 LSD would be ideal.

But just for the 'Ring I would use a 3.91.

[Demlotcrew]

The ring is a strange one, i feel different ratios are needed for different parts of the track so you need to cater for all the sections

I would not go to anything lower than 4.1 as you will struggle up the long straights and the 3.91 will be a bit sluggish to get out of the corners on some of the slower bends at the start.

Andrew

[Andyboy]

318iS VLN cars do 8.40 laps of the ring...........with standard power and a 4.1 diff.

[oldroydsr4]

^^^ In this months total bmw a 318is with standard power has recorded a 8.22 on trackday rubber and i believe the 318is in the VLN lap at approx 8.15 (converted for btg)

[hoshy]

318iS VLN cars do 8.40 laps of the ring...........with standard power and a 4.1 diff.

got the mag. notice half of it was written by you

Great article on the iS though. Stunning what can be done with local knowledge and a 4pot :p

[agreen]

^^^ In this months total bmw a 318is with standard power has recorded a 8.22 on trackday rubber and i believe the 318is in the VLN lap at approx 8.15 (converted for btg)

318is rightness

blumin brilliant little cars

[oldroydsr4]

Imagine what the same driver could do in a 325i

[agreen]

Imagine what the same driver could do in a 325i

crash lmao anyway better stop or it will ruin this thread

there must be a reason why he chose an "is" not a 325 but thats another thread another time

[oldroydsr4]

^^^^
Agreed not the time or place to go into this, we all know where this discussion will end.

But i think it is because the 318is is very competitve in its class in the VLN(maximium of 1800cc or something) and the 325i would be with some serious machinery and get mullered

Back to thread.

[hoshy]

About how long are the longest straights?

[Demlotcrew]

318iS VLN cars do 8.40 laps of the ring...........with standard power and a 4.1 diff.

So what a E30 M3 does the GP and northloop in 8.22 in stock form with a 3.25

[handpaper]

About how long are the longest straights?

For illustration , here's a video I made in July last year.
The longest 'straight' you'll get to drive on a public (Touristfahrten) day is between Bergwerk and Mutkurve (5:35-6:19), with the kink of Kesselchen in between. It's nowhere near dead straight, but itis flat-out, mainly due to an average 1-in-13 gradient that keeps my standard 325i down to an indicated 110 mph.
The section between Flugplatz and Schwedenkreuz (2:23-2:41) curves too, but slopes downhill, making it much faster - 125-130 indicated.
The fastest part of the circuit for lower-powered cars is Fuchsrohre (the Foxhole)(3:00-3:18 ). It isn't straight at all, anywhere, but you can thread a straight line down through the early curves and the compression at the bottom gives plenty of grip to help you through the left kink that's there as well. 140 is the most I've seen on the speedo through here - but TBH it's not somewhere you really have time to look at a speedo
The main straight is something you'll only get to drive on a track day that allows continuous lapping, or a race . It's 2 km of dead straight, but most things can take the kink at Tiergarten (0:35) flat, making it 2.5. Trouble is, it's largely uphill, too

So what a E30 M3 does the GP and northloop in 8.22 in stock form with a 3.25

Now that I'd like to see!

Here's Hans Stuck on a qualifying lap in the M3 GTR. Monster power, lots of downforce, sticky slicks and legendary talent gets around in 8:14.
Stock E30 M3 just 8 seconds behind that? I don't think so!

318iS VLN cars do 8.40 laps of the ring...........with standard power and a 4.1 diff.

Standard power is a bit misleading here; VLN regs allow 5% over/under standard - guess which way they err? Also, a VLN 318iS will also be built down to the V2 class minimum weight of 980 Kg!

Back on topic , I've driven the 'Ring with a 4.1 and 3.91 in my (chipped and dropped) 320i, and with a 3.73 in the totally standard 325i.
And it's really a case of swings and roundabouts
The Nordschleife was designed to test cars; it has a huge variety of corners from tight hairpins to flat sweepers and everything in between.
One way to do it is to pick a diff that lets you reach the limiter in 5th at the fastest part of the circuit; for my (currently) standard 325i, that's the 3.73 it's got at the moment (141 mph @ 6200 rpm). But if I raise the rev limit using MS or an ECU chip, to say, 7,000, a 4.1 would suit it better.
Alternatively, you could aim to minimise gearchanges, which would need a little trial and error. I worried a little about putting a 3.91 in to my 320i, thinking it would reduce acceleration. It did, but only in each gear, and also let me hang onto that gear for longer - a section (7:08-7:52) that previously needed a 3-4-3-4-3 change could now be strung together smoothly in 3rd.

[Andyboy]

About how long are the longest straights?

For illustration , here's a video I made in July last year.
The longest 'straight' you'll get to drive on a public (Touristfahrten) day is between Bergwerk and Mutkurve (5:35-6:19), with the kink of Kesselchen in between. It's nowhere near dead straight, but itis flat-out, mainly due to an average 1-in-13 gradient that keeps my standard 325i down to an indicated 110 mph.
The section between Flugplatz and Schwedenkreuz (2:23-2:41) curves too, but slopes downhill, making it much faster - 125-130 indicated.
The fastest part of the circuit for lower-powered cars is Fuchsrohre (the Foxhole)(3:00-3:18 ). It isn't straight at all, anywhere, but you can thread a straight line down through the early curves and the compression at the bottom gives plenty of grip to help you through the left kink that's there as well. 140 is the most I've seen on the speedo through here - but TBH it's not somewhere you really have time to look at a speedo
The main straight is something you'll only get to drive on a track day that allows continuous lapping, or a race . It's 2 km of dead straight, but most things can take the kink at Tiergarten (0:35) flat, making it 2.5. Trouble is, it's largely uphill, too

So what a E30 M3 does the GP and northloop in 8.22 in stock form with a 3.25

Now that I'd like to see!

Here's Hans Stuck on a qualifying lap in the M3 GTR. Monster power, lots of downforce, sticky slicks and legendary talent gets around in 8:14.
Stock E30 M3 just 8 seconds behind that? I don't think so!

318iS VLN cars do 8.40 laps of the ring...........with standard power and a 4.1 diff.

Standard power is a bit misleading here; VLN regs allow 5% over/under standard - guess which way they err? Also, a VLN 318iS will also be built down to the V2 class minimum weight of 980 Kg!

Back on topic , I've driven the 'Ring with a 4.1 and 3.91 in my (chipped and dropped) 320i, and with a 3.73 in the totally standard 325i.
And it's really a case of swings and roundabouts
The Nordschleife was designed to test cars; it has a huge variety of corners from tight hairpins to flat sweepers and everything in between.
One way to do it is to pick a diff that lets you reach the limiter in 5th at the fastest part of the circuit; for my (currently) standard 325i, that's the 3.73 it's got at the moment (141 mph @ 6200 rpm). But if I raise the rev limit using MS or an ECU chip, to say, 7,000, a 4.1 would suit it better.
Alternatively, you could aim to minimise gearchanges, which would need a little trial and error. I worried a little about putting a 3.91 in to my 320i, thinking it would reduce acceleration. It did, but only in each gear, and also let me hang onto that gear for longer - a section (7:08-7:52) that previously needed a 3-4-3-4-3 change could now be strung together smoothly in 3rd.

Thankyou for that fascinating insight

Ring Racing's VLN Compact Ti (1.8 litre) does BTG in 8.40-8.50 although I didn't get below 9.40 on a dry clear track but of course an absolutely committed driver in a race and on the edge will find 60 seconds. Their 325i Coupe is no faster. A good iS, 16v Astra or 16v Golf VLN car does it in @8.30. Light weight, decent driver and sticky rubber. A ride in Fabian's iS is something else - 1000 kilos fuelled up and it pulls 1.6g's on turns.

As for your 5% power argument - well, 5% over stock isn't much when you only have 140 odd to play with.

Nobody said anything about a STOCK E30 M3 being 8 secs slower than a GTR. I think you'll find some of the more modified examples are very, very fast but of course the law of diminishing returns applies.

Back to the differential ratio question. Either 4.1 or a 3.91 will be okay but a 3.91 will be much easier to find. As with all Ring newbies, the main thing is to go easy and learn the circuit first before any heroics, especially if the track is less than bone dry. Any accident involving a recovery truck and new barrier is £2000.

[UweM3]

I don't think a diff to rev out 5th is the important thing. If it puts you "between gears" on several bends you will loose time and fun espcially if you are a newbie.
Personally I don't think you can recomment THE diff ratio. Depends a little on driver and experience. I went shorter in the m3 because of the dreaded uphill section and first it seemed to be ok, but with getting more laps under my belt the ratio suddenly started to put me inbetween gears. Bends I could easily reach by revving out a gear on Friday, looked completly different on Sunday afternoon (running out of revs to reach breaking point)
I would go with a 3.91 first, better a little bit too long to start with. BTW I don't think 4.1 will make SUCH a difference. 3.73 to 4.1, yes but not much between 3.91 and 4.10. But I might be wrong here, I haven't driven a 318 with such a short diff.
My rule, keep your momentum


@handpaper, 140 down Foxhole! Wow, I want to drive behind you to see how that looks (if I can manage to follow you in the first place, I start shitting myself with 125!)

here a video from last year filmed from Jake and his a 320is I had a real struggle to get up Kesselchen and thought my car was going to blow up. It wasn't pulling at all and running VERY rich. Afterwards I discovered that I had forgotten to put the plug back on the airtemps sensor....(outch)
http://garage.s14power.com/data/502/8mi ... -Uwe-3.wmv

[northloop]

Handpaper.

I had the same issue you speak off when I changed the gearbox on my 205. I went from the standard 8v 205 to an Mi16 unit. I did it for no reason other than it was available after I blew the 8v up The resulting change was huge. Sections like Hatzenbach, Briedscheide, Brunchen where I would previously have held third I needed a short shift into 4th. This took ages to get used to and didnt feel right. A while later and a couple of sneakily timed laps show that I am back on the ball again and that overal things are as they were before. However using the Mi16 box means the engine is working much harder, using more revs more of the time. This can only be reducing the life of the engine. At the end of the day what racers use is often irrelevant to the likes of you and I. Unless we have an infinite budget of course.

The quickest E30 M3 I know of in the VLN is the pink one, there are vids of it knocking around. No idea of its combined circuit time

Not sure if this link still works or is indeed the right one, cant check it as i'm at work.
http://www.frankuhlig.de/index.php?name ... it&lid=159

[Demlotcrew]

Uwe i think thats 140 indicated there is no 320 that will reach 120mph and no 325i that will get anywhere near 140 on any part of the ring.

Handpaper this type of thread has been done to death, do a search and you will find all the data which shows the times/driver/car of the M3 i have used as an example.

Andrew

[Andye]

Wow, wasn't expecting this sort of reply, brilliant info and advice and the Stuck lap in the GTR is legendary!! I'd better check what dif is in it now then look out for a 3.9:1 LSD, any one got one??

Cheers Andy 07866256713

[jimcameron]

@handpaper, 140 down Foxhole! Wow, I want to drive behind you to see how that looks (if I can manage to follow you in the first place, I start shitting myself with 125!)

[cough]



147 thread clicky

Sorry, couldn't resist it. Planning this year's trips...

[handpaper]

Show-off
Yes, 140 was on the speedo, take off 3% for 50 profile tyres plus the 5 mph the speedo overreads and you get a more believable 130.
Hope to get a proper lap with you sometime this year, Jim

[UweM3]

Show-off
Yes, 140 was on the speedo, take off 3% for 50 profile tyres plus the 5 mph the speedo overreads and you get a more believable 130.
Hope to get a proper lap with you sometime this year, Jim

naughty naughy not to mention the 50 profile in the first place.

147! I think my surfival instincts would get seriously in the way
well, I will have to have a word with my shrink....

[northloop]

You still in third gear at the time Jim

[jimcameron]

Show-off
Yes, 140 was on the speedo, take off 3% for 50 profile tyres plus the 5 mph the speedo overreads and you get a more believable 130.
Hope to get a proper lap with you sometime this year, Jim

No problem, bit quicker than last time!