Notax compact update

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Re: Notax compact update

Postby is-si » Wed Mar 11, 2015 8:52 am

Notax, I'm glad this working out now and you're getting some mileage in 8)
As I understand it, you would build a diff using an E28 housing that would bolt in your beam and connect to the shafts you have.
You have always maintained that you like motorway speeds for one of your rallies but with 8K of revs I'd be gearing for acceleration - If you don't the escorts will. I suspect that a motorsport CWP beginning with 5 should do the trick.
Dear do this rallying :lol:
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Re: Notax compact update

Postby M3 Compact » Wed Mar 11, 2015 10:43 pm

Totally agree John. :arrow:

With 8K revs, a 1:1 top gear with a 5.1:1 210mm CWP is surely the WTG for Chris?

Not sure about 8K revs with those S50s tho....
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Re: Notax compact update

Postby notax » Thu Mar 12, 2015 12:38 am

is-si wrote:Notax, I'm glad this working out now and you're getting some mileage in 8)
As I understand it, you would build a diff using an E28 housing that would bolt in your beam and connect to the shafts you have.
You have always maintained that you like motorway speeds for one of your rallies but with 8K of revs I'd be gearing for acceleration - If you don't the escorts will. I suspect that a motorsport CWP beginning with 5 should do the trick.
Dear do this rallying :lol:


Yes, it is damn expensive - I think I'm down about £20k so far in 2015 :shock: I really need to reign in the expense, the paddleshift shouldn't cost much more to sort and should significantly reduce wear on the gearbox and the potential for driver error...

I could do with testing what speeds the car is actually achieving - I may take it out with a satnav to check, but the fact is that first really is too long to be ideal. It will be interesting to see whether I use 6th at the next event, if not then yet another diff rebuild seems sensible. I now have 3 good 188mm diffs , two freshly built and one brand new, so reluctant to go for yet another one. Would you use a standard 210mm or go Gripper or whatever? I have a gripper diff in one of the 188mm, should this be stronger than a standard 188mm? Maybe that could be a half way house if I can buy a 5.1 CWP?
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Re: Notax compact update

Postby notax » Thu Mar 12, 2015 12:40 am

M3 Compact wrote:Totally agree John. :arrow:

With 8K revs, a 1:1 top gear with a 5.1:1 210mm CWP is surely the WTG for Chris?

Not sure about 8K revs with those S50s tho....


See above, maybe the way forward...

What do you think an S50 should rev to? Mine has steel rods, ARP bolts and toughened (but not steel) crank? I thought 8k was being reasonably cautious! Mine have only let go in the past when I haven't used ARP bolts...

The gear ratios I'm using are:

Constant 1.042
1st 2.381
2nd 1.954
3rd 1.620
4th 1.354
5th 1.136
6th 1.000

Drenth's spreadsheet predicts 1st gear top speed at 8k as:

57mph with 4.45
50mph with 5.1

6th gear top speed:

137mph with 4.45
119mph with 5.1

Bit confused as actual speeds with 4.45 seem to be first 50mph and 6th 129mph...
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Re: Notax compact update

Postby M3 Compact » Thu Mar 12, 2015 10:11 am

That's a long first gear and those other ratios are very close.
Did Drenth use a dyno plot to calculate the most appropriate ratios? I'd expect an S50 to have a wide enough power band to haul it through fractionally less focused ratios from a slightly shorter 1st gear.

Hope your trailer has an electric winch! :mrgreen:

Didn't realise you had fancy rods etc, Chris. Whoever built it is likely to know far more than I do about such things, I always tend to err on the side of caution with all rally related mechanicals.

Assuming 640mm tyre diameter Drenth's numbers look about right with the 4.45:1.
How are you measuring the speed? (Rolling Road?)
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Re: Notax compact update

Postby notax » Fri Mar 13, 2015 5:44 pm

Hi, yes the gears are very closely spaced - with a 4.45 they quote the following max in each gear:

1st 57mph
2nd 70
3rd 84
4th 101
5th 121
6th 137mph

It seems Drenth don't offer that many ratios strangely. In Europe the tarmac cars are all limited to 115mph by the regs apparently so would inevitably have a lower top speed in first, but I agree the ratios don't seem ideal for me. Hopefully the clutch will survive (it is brand new, custom made and deliberately over specified by me) I think it would be good for 4-500bhp so hopefully the long first won't kill it - so long as I don't try and spin it off the line in the dry with sticky tyres....

The engine builder seems happy with me taking it to 8k revs and to be fair the engine coped with this with no issues - until I ran it crazy hot last year when the auxiliary belt snapped due to a very unlucky stone getting in between it and a pulley. I realised it was cooking but not that the water pump had stopped working. Doh! This was the reason the engine needed a full rebuild with new pistons etc and part of the reason for my ongoing mega expense (although that rebuild isn't included in this years expenditure...)

The top speed of 129mph is what the car reached on the rolling road at 8k revs in top. Using a phone app it reaches around 50mph in first, but I will try it with a Tomtom which seems pretty accurate to get another measure.
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Re: Notax compact update

Postby M3 Compact » Fri Mar 13, 2015 9:15 pm

In your shoes I'd be chucking a 5.1:1ish 210mm diff in it, Chris.
I think you'll be able to use the Z3M shafts with a 210mm, possibly using M3 Evo output flanges?
If you can't because of a wider overall diff/shaft lengths situation, you might even be able to use M3 shafts with appropriate bearings? :idea:

It might be kinder on the clutch to just light the tyres up off the line and let their rubber organise the slipping to gripping?

Deffo invest in an electric trailer winch if you haven't already got one tho. :wink:
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Re: Notax compact update

Postby notax » Sat Mar 14, 2015 12:22 am

Thanks, I'll discuss the diff options with Woody (my mechanic). As I've got three 188mm diffs (2 x 4.1 and 1x 4.45) it would be handy if the 210mm diff would be interchangeable...

I did find some motorsport 5.1 CWPs for a 210mm somewhere a while ago but they were damn pricey. Will see if I can track down an E34 diff - is this the only model which ran the correct 210mm one do you know?

Fortunately car seems ok putting it on the ramp, no smoke billowing from clutch yet :lol:

Interesting idea re lighting the tyres up... dropping the clutch at about 4k didn't do it (with soft slicks in the dry) and Woody (and I) are worried I might bust a shaft if I try with any more commitment....
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Re: Notax compact update

Postby gartrac » Sat Mar 14, 2015 4:02 am

210 diff in a Compact

Pro's
Very strong
Your Z3M drive shafts will fit
Diff will bolt into Compact rear beam

Con's
Correct case is becoming very rare, not E34
Weight, you'll give yourself a hernia picking it up
Prop shaft will need to be shorter
Rear cross member will need modifying, diff fouls on it
Rear mounting will need modifying, as far as I'm aware there is no rear cover available with a single or twin ears like the 188
Standard slipper only has 2 clutch plates, 1 each side
Crown wheel and Pinion expensive 5.1 is Motorsport ratio £950.00
http://www.ebay.co.uk/itm/231497401070?_trksid=p2060353.m1438.l2648&ssPageName=STRK%3AMEBIDX%3AIT

Certainly not what I would call interchangeable but as already stated with your revs and BHP it really is the only reliable solution

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Re: Notax compact update

Postby notax » Sat Mar 14, 2015 9:04 am

Peter, thanks for your comprehensive post. Do you know which car the 210mm diff does originate from if not the E34? The Automac ad seems to suggest that they offer a 5.1 which will fit an E46 LSD - I can't imagine that would fit though...? Ironically I've only just shortened my prop to fit the Drenth...

I've just checked on line and it appears the E34 M5 does use a 210mm diff, no idea if there is one with a better casing for my car though?

http://www.ebay.co.uk/itm/Bmw-E34-M5-3- ... 3aa4e29b7c

The E36 and E46 M3 seem to use 210mm too. Although my car now has the full Z3M back end, it is proving tricky to get new shafts from BMW at the moment (locally at least) I wonder whether I'd have been better off biting the bullet and fitting the whole rear floor from an E36 M3 - a lot of work but then the correct diff would have fitted together with easier to obtain uprated shafts etc.... Having said that, the current 188mm diffs have only let go after shafts have failed so maybe they'll last longer now that the shafts seem ok.. . Now uprated to Z3M (and now that I've given up with coil overs) the back end does now seem reliable. Touch wood.
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Re: Notax compact update

Postby gartrac » Sat Mar 14, 2015 2:28 pm

Notax answers in the order you asked them

210 diff you need comes from
E24 M635CSi Coupe
E28 M5 Sedan

Not easy to find and the E28 must be M5 not 535

Looks like this
https://drive.google.com/file/d/0B78_j3 ... sp=sharing

The way to recognize the correct diff is it must have the 4 mounting holes on the top plus the side flanges have 8 bolts the 188 has 6

One other gotcha is the diff carrier in the E28 diff uses smaller diameter crown wheel bolts than the later diffs not insurmountable but still a small problem

Z3M shafts, make me an offer you could have spare wishbones as well
I also have another rear axle identical with shafts less the diff
http://www.ebay.co.uk/itm/181687438045?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

I don't think fitting the rear floor from an E36 M3 is an option it would be easier to use the E46 Compact shell which again isn't really an option, it would mean starting again plus I prefer the appearance of the E36 and as far as I know there isn't a comparable body kit available for the E46

The problem with the 188 diff was described perfectly by M3 Compact, if you change to a 5.1 ratio it will inevitably become unreliable due to the size of the pinion. as the ratio gets lower, sounds wrong I know but a 5.1 is lower than a 4.45 the pinion gets smaller and weaker

Anything else you want to know just ask

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Re: Notax compact update

Postby mef » Sat Mar 14, 2015 7:01 pm

My diff is 3.80 from the E90 M3 but with the Tractive dropgears it comes out equivalent to a 4.6:1 FD. I'm also running on 650mm diameter tyres. I tend to use leass than 8K though, maybe 7750, (also on steel rods with ARP bolts)

my Tractive gear ratios are:
1st 2.58
2nd 1.81
3rd 1.44
4th 1.238
5th 1.08
6th 0.96
drop gears 1.2:1 (20/24)

FD 3.80:1

I have never actually checked out the top speed but there seems to be plenty!

Martin
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Re: Notax compact update

Postby mef » Sun Mar 15, 2015 7:21 pm

I gave my car a test run today and found that it's geared for 17mph/1000rpm in 6th
which equates to 131mph @ 7750 in 6th. My X Dash speedo is within 1 mph of the iphone GPS speedo app.

Shoud be enough!

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Re: Notax compact update

Postby notax » Fri Mar 27, 2015 12:24 am

Very pleased to be able to report that Woody has managed to fit my custom made paddle shift system - and it works :D Thanks to Martin (mef) for his help during the development. I'll try and take some pics this weekend when at a rally in Ipswich to show you the installation. Road tested it today, and after reducing the amount of throttle the blipper is using, it works brilliantly. It will even flatshift from second to 6th. Out of interest the GPS was showing 103mph when it changed into 6th at 7750 revs, so it does seem 6th is about right, just a shame first is so long. I'm again going to take it easy off the line this time if its grippy... will lose some time but prefer to try and respect the transmission at this stage.

The noise of the air valves in the car adds to the experience, but I don't find them too loud - even when not wearing a lid. Having said that, the car is crazy loud inside anyway! Few more tweeks needed ideally, including programming it to stop me being able to over rev on downshifts by preventing a gear change - if this is possible with the DTA software..?

I'm intending to again take it steady at Woodbridge - particularly over the car's nemesis as there is a jump there. Fingers crossed. I'm going to try and dip the clutch as we land to take the strain off the drive train - or even better, avoid getting any air at all if I can...
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Re: Notax compact update

Postby mef » Fri Mar 27, 2015 12:35 am

Great progress Chris!

I fitted my air valves on the underside of the tunnel just above the output flange so the noise of the exhaust air from them is not too objectionable although you're certainly aware of it!

I'm not sure about the
Downshifts, mine works perfectly without a blipper valve so you're on your own with experimenting with the Dta software settings!

Cheers,

Martin
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