6-Speed Gearbox

MikeMarsUK said:
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Regarding the selector, the final step in the instructions is modifying the selector (by trimming the end of one of the bolts by 1cm). I presume that will give the gear lever more freedom to move at the right-hand edge.
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Vince is definately the right person to talk to regarding 6-gear conversions, he has previously worked for a company which was producing 6-gear conversion kits some years ago. He is concerned about the 'internal fork (aka shift rail)' which looks like it would be tricky (or impossible) to modify without removing the gearbox. So I have emailed EuroTuning for clarification on this point.
 
A few more additional details...

It is possible to specify a 6th gear other than the one mentioned in the description. The following have been mentioned:

* 0.74 - Usually for 1.8T
* 0.65 - the normal one used for TDIs
* 0.59 - Usually for T4 vans ... very much an 'overdrive' gear. Plausible.
* 0.52 - Usually for T5 vans ... crikey. More like 'hyperdrive' rather than an 'overdrive'... I dunno if this would be at all practical.

People who have already changed their 5th gear might find that 0.62 and 0.59 are too close together, someone on the TDIClub forum is therefore going for a 0.71 for 5th, and 0.59 for 6th as follows:

EuroTuning said:
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Passat_19TDI_CTN_071_059_en.png
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Does anyone think a 0.52 would be usable & reliable? It'd be a massive jump between the standard 0.75 5th gear and 6th. Would the clutch survive with it?
 
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Hi Mike,

There are currently 3 choices of longer 5th: 0.681, 0.659 and 0.622.

The vast majority of people with a modded 5th gear have chosen 0.659, though DJ190 has the shorter 0.681 set and Mike Skipton uses the longer 0.622 set.
Skipton's car is significantly more powerful/torquey than our remapped 75s, so can get away with driving the longest of the gear sets, but I imagine we could struggle to get up motorway hills unless we were breaking the speed limit. I'd certainly talk kindly to Mike about a demonstration of his 0.622 ratio before I made any choices.
To my mind, the 0.59 cog for the T4 is probably a bit too long. Is it possible to use the ratios we use for modding the 5th gear if we supply them? Personally, if I was to do this mod, I'd like standard 5th and 0.622 (like Skipton) if the remapped AMF engine is capable of driving it.

Be aware that, if the gear set is too long, the drastic ratio between engine revs and road speed confuses the ECU, meaning cruise cannot be engaged. The 0.622 ratio is within the ECU's limits and so works just fine, but 0.59 may be to the wrong side of that limits, meaning no cruise in 6th gear. :(

Cheers,

Tom
 
This graph helps to visualise things nicely:

A2TDiRatios.gif


At the moment, my own car (TDI75 with 0.659) goes red, red, red, red, black.
Mike Skipton's TDI90 goes blue, blue, blue, blue, yellow. Notice that the 0.681 ratio which DJ190 has is only fractionally longer than the standard 5th gear in the TDI90.

If I was to have a 6-speed box, I think red, red, red, red, red, yellow would be ideal, as the increase in gradient between each gear and the next is perfect. I suppose if a remapped AMF is able to drive 0.59 without cruise issues, then it would be worth considering, but I imagine it'd be too long for my usual 60-65mph cruising speed. Sadly, the square-relationship between speed and drag cannot be overcome with longer cogs. I wouldn't want to find that I had to drive faster than I'd ideally like to be able to make use of the 6th gear.

Tom
 
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I think that's the other big unknown factor really - the rev drops are great, but if it gets to the point where your normal cruising speed means the revs drop below peak torque, it'll mean that any acceleration around that point will be excessively labourious for the engine, so will harm MPG, or as you say, you'll end up having to drive faster in order for the engine to be comfortable at cruising speed!

What do the torque curves for standard remapped 75s (and 90s) look like?

I have the same set up as Timmus with my longer 5th, and the remapped 75. It's quite interesting that the 90 gear ratios are slightly longer the whole way through the box though...

timmus said:
I suppose if a remapped AMF is able to drive 0.59 without cruise issues, then it would be worth considering, but I imagine it'd be too long for my usual 60-65mph cruising speed. Sadly, the square-relationship between speed and drag cannot be overcome with longer cogs. I wouldn't want to find that I had to drive faster than I'd ideally like to be able to make use of the 6th gear.

Tom
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I'm driving to Northern Italy in September (Savona) I am considering a diversion to Czechoslovakia to get this six-speed gearbox fitted .... what is this discussion about Vince being able to do this mod? I thought that it needed a special gearbox casing to accomodate the 6th gear? I feel that having the original 5th would help my lane cruising, here (I like to get into top as soon as possible) Then the 0.622 ratio would be just dandy for all those Continental trips that I do .... (although I do get onto the A55 quite soon from my property, and because traffic is fairly light (it IS North Wales! LOL), I am soon into 5th, anyway!
 
A good look at the torque curves would certainly help. Having Mike Skipton's torque curve as a reference would also be very usefull.
Given that I don't have any great difficulties managing the gap between 4th and 0.659 5th, as my car stands at the moment, I feel that upgrading to a 6-speed box could only be justified if I got both the convenience of the standard 5th gear back again as well as an increase in length of my top gear. Hence why I feel that standard 5th + 0.622 6th would be the ideal.

As Dan will know, 63mph with the 0.659 5th requires almost exactly 2000rpm, as can also be seen on the graph above. Upgrading to the 0.622 would bring the revs down to about 1850 at 63mph. Is the AMF engine torquey enough at that rotational rate? It is indeed the big unknown.

Tom
 
DJ 190 said:
....what is this discussion about Vince being able to do this mod? I thought that it needed a special gearbox casing to accomodate the 6th gear?
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The idea here is that the add-on box is bought from EuroTuning and then fitted in the UK. Vince knows gearboxes, hence why his name has been mentioned.
 
timmus said:
The idea here is that the add-on box is bought from EuroTuning and then fitted in the UK. Vince knows gearboxes, hence why his name has been mentioned.
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Yeah exactly so. EuroTuning sell the whole kit, everything needed. Vince is really the perfect person to fit it given his previous experience.

There are two big unknowns ... firstly is how is this 'keyhole surgery' method of replacing the gear shift rail carried out, since it is not described anywhere (the instructions show the box being disassembled).

The second is how the car will behave with a super-long gear as above. I do have a torque/hp chart for mine somewhere, but I can't find it right now. Wasn't there a thread on the forum somewhere, where people were posting their charts (I can't find that either)?
 
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This chart shows the two alternatives - the standard 0.65, and the 0.59 overdrive. He hasn't got the wheel circumference right so the speeds aren't accurate.

EuroTuning said:
AudiA2_14TDI_EWQ.png
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So at 80mph, a drop of either 400 or 600 rpm.



Riverlad's chart shows that the torque peak is at 2200 rpm.

With the 0.59 gear, at 60mph (1750 rpm) there is 50hp available, rising quickly up to 2200rpm (70), and then gently increasing after that. 50hp is fine for cruising along steadily (I think the car needs around 20hp for 60mph), or going up gentle hills, but it would probably need to change down to 5th for steeper hills or acceleration.

At 80mph (2400 or so) there is plenty of torque & hp available, but it would probably still be a good idea to change down to 5th for acceleration in order to reduce the strain on the clutch.

There is the potential cruise control issue - although personally, while I use cruise daily, it is only in a 50mph average speed camera zone, and I don't use it in normal driving.

With the 0.65 option, it is exactly the same as many of the 5th gears already on the forum, but with the original 0.75 still available (so a narrow gap between 5th and 6th).


The 0.62 is not available from EuroTuning.


Interestingly enough I was talking to a Ecomotive (Seat) driver yesterday & he said the standard gearing is around 1600-ish rpm for 60mph!! He was having problems with the DPF regeneration (not entirely surprising).
 
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MikeMarsUK said:
So at 80mph, a drop of either 400 or 800 rpm.
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Surely more like 400 or 650...?

MikeMarsUK said:
The 0.62 is not available from EuroTuning.
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I wonder is this something that Vince could fit instead, or whether EuroTuning would be willing to fit it if we supplied it?
To my mind, the 0.59 is just too long, whether or not cruise still works. At 60mph, you'd be doing 1700revs, which I don't think is enough for that ratio to be hassle-free.
Mike, it seems to me that your eco-driving techniques extend to motorway driving, so slowing down and changing down to go up hills might not bother you. I love getting good fuel economy figures, hence my 60mph motorway cruising speed, but I just want to be able to engage top gear, set cruise, sit back and listen to music. On a 4 hour drive, I don't want to have my thoughts ruled by fuel economy. I invariably average 70+mpg on motorway runs anyway, so sacrificing the comfort and convenience of 'engage-and-set' for the sake of a few extra mpgs just isn't worth it for me.
The 0.622 ratio is known to work with cruise and is probably shorter enough to lift the revs closer to peak torque, meaning 'engage-and-set' would still be an option.

Tom
 
Don't forget that tyres (circumference) can also have an effect of down-gearing the car
My winters are about 5% larger and drop revs by almost 200rpm at *70-ish (cough cough)

Obviously this affects all gears equally.
Just though I would add my 2p

J
 
timmus said:
Surely more like 400 or 650...?
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Yeah, that was a typo I didn't spot for a while (at 2048x1536 resolution there isn't much difference between a 6 and an 8!)

timmus said:
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I wonder is this something that Vince could fit instead, or whether EuroTuning would be willing to fit it if we supplied it? ...
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Someone did ask EuroTuning about 0.62 but it didn't sound like ET were interested in doing it. I don't know whether ET are using standard splines or not. (Perhaps if there is someone who knows gearboxes well, they could look at the installation photos to see whether it looks standard or nonstandard).

Based on 35mph/1000rpm I *think* that the Polo Bluemotion uses this 0.59 ratio (or an equivalent ratio given the final drive).
 
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5th is very long on a bm, fine once you get used to it,
anything from 40 up the way is fine and thats with a TDI 80

it trounces the tdi90 I got with its mpg, you get 60 without trying,75 on a run and running solo on a run your upto 88 on a steady 60-65 run ( perth to Inverness )
so some hills in there too.
The only advantage of the Bm is 3rd,4th and 5th are all longer legged so not much of a long reach into 5th.:cool:
 
chubbybrown said:
5th is very long on a bm, fine once you get used to it,
anything from 40 up the way is fine and thats with a TDI 80
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That sounds quite promising for the same gearing on a remapped TDi.


For me, the 0.59 is sounding quite good - for other people, the changing down on hills & cruise control will probably be more of an issue.


Of course, people have to keep in mind that this has a ridiculously long break-even point (well over 100k miles based on the BSFC chart, and that's assuming that the gearbox doesn't need to be disassembled).
 
Been watching and reading all these 5th replacement/ additional 6th gear threads recently with great intrigue.


chubbybrown said:
The only advantage of the Bm is 3rd,4th and 5th are all longer legged so not much of a long reach into 5th.:cool:
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What's the score on lowering the final drive?
 
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