42 into 34 does go

hotstuff

hotstuff

A2OC Donor
I have undertaken what is perhaps the most ambitious mod on humpy to date.
Most wil be aware that I bought a high spec smashed TDi to transplant some it's goodies into our two A2's. Lots of the toys have been moved, seats, DD dash, DIS were the easyest. The smashed car also came with a 42 litre fuel tank! So, wanting a larger range, I researched the possibility of replacing humpy's 34 litre tank with the 42 litre unit. Although the site does have some info on the various tank sizes, it appears that this mod has not been attempted in the UK before. Not being able to access (or understand) the German forum, I went for it, well, alone.

This is not a "How To" guide, but rather what is involved should someone else undertake such a project. As things stand at the moment, the car is still on axle stands but I am confident that all the issues have been resolved, and, weather permitting, the mod should be complete this coming week-end. I have posted some pics below to show the differences in the two fuel tanks and support bracket.

blue skies
tony

Tank 34l a.JPGTank 34l b.JPGTank 42l a.JPGTank 42l b.JPGTank Brackets.JPG
 
Hmmm, interesting, this is something I'd like to do one day. Are you going to run into the reversed fuel-level-sender issue, or is your current dash compatible with the new one? (Although I guess if you have moved the DIS across, it should match the 42L tank).

My wishlist is:

* DIS
* 42L tank
* Underbody aerodynamics
* Matching the 3L cars on fuel consumption :)


hotstuff said:
... Not being able to access (or understand) the German forum, I went for it, well, alone.
...
Click to expand...

Thanks to Brett tweaking the forum settings, you can now use Google Translate on both the forum & also the wiki.
 
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Hi Mike
Well, I hit the reverse issue on the fuel gauge when I transplanted the DIS from the same vehicle into mine. For some months now, I have a fuel gauge that I have fooled into working by fitting a resistor, and been filling at every 350 miles max. I have suffered the indignation of running out of fuel once though. Although I was always going to fit the larger tank, the fuel gauge issue will now be addressed with its compatible sender in the fuel tank.
As to the German Forum, despite having registered, it will not allow me to log in?

blue skies
tony

PS Mike, parcel come through OK?
 
hotstuff said:
Hi Mike
... Although I was always going to fit the larger tank, the fuel gauge issue will now be addressed with its compatible sender in the fuel tank.
Click to expand...

That sounds like the way to go... get the DIS & the tank from the same car. Good tip.

As to the German Forum, despite having registered, it will not allow me to log in?
Click to expand...

You can't login / post when using google translate, but you can browse the forum OK. What I do is to have a window for google translate, and another window logged in directly to the site where I can post. If I post, I put in both my original english & the google-translated german version.

PS Mike, parcel come through OK?
Click to expand...

The card came today - I will need to pick up the parcel from the delivery office tomorrow morning :)
 
let me know your German Forum username and I will check it. You should have a confirmation email from us; you need to click the link before you can log in.

- Bret
 
bretti_kivi said:
let me know your German Forum username and I will check it. You should have a confirmation email from us; you need to click the link before you can log in.

- Bret
Click to expand...

Thanks Brett

I'm off to bed now but I'll PM you tomorrow.

blue skies
tony
 
Hi Tony, a couple of questions -
I understand the exhaust is different - is it just a case of bolting on the later model back box.
Assuming the tanks are a similar depth, is it possible just to swap the fuel level float unit assy

Cheers Spike
 
Next episode then ...
To do the fuel tank conversion you have to remove and strip a substantial part of the rear of the car. The car is on a level firm surface and supported on axle stands at a good enough height to allow me to work underneath at about the middle of the car - handbrake area. It's a good idea to make sure there is precious little fuel in the tank which makes the tank not only lighter but you have less surge to contend with! Before everything else - disconnect the battery, remove the rear wheels and rear wheel arch liners.

After that comes the rear axle. I have removed the rear axle once previously so this step was pretty straightforward. I needed an extra pair of hands because not only is it heavy, but awkward. The axle is only attatched at the lower shock absorber bolt and throught the saddle mounting just ahead of the rear wheels. Although easier, don't be tempted to remove the saddle mount as the rear wheel geometry will be out of alignment. I supported the axle on our plastic, glass recycling boxes whilst I removed the rear springs. Good opportunity at this stage to inspect the top and bottom spring pads and to perhaps upgrade springs ;). The handbrake cable is disconnected from what I can best describe as a "cage". This part is located between the fuel tank and the underbody, quite high-up, and connects the hand brake lever cable to the cable that runs to the rear drums. I'll take a pic tomorrow and post that too. There is a large spacer that fits between the axle bush and the saddle mount - make a note of its orientation for re-assembly. So, till now, no headaches and all going smoothly. He says ...

Next bit is the exhaust. In answer to your question Spike, the rear silencers are the same and are normally replaced by cutting the exhaust just behind the rear axle. The exhaust on the A2's is a single run from manifold to rear tip. The fundamental difference between the exhausts for the 34 and 42 litre tank vehicles is how the exhaust routes around the tank area. The 34 l has a more gentle curve in that area whereas the 42 l version has almost a right angle bend. I got home too late today for pics, but I'll do that tomorrow and post. I cut the exhaust in the centre tunnel area and I will fit the part from the salvaged car to humpy. This is an interim measure, when the car is on the road again, the entire exhaust will be removed, de-catted and the Sebring sports box that I bought off Adrian will be fitted. Looking forward to that burble!

At this point the tank is fully exposed and removal can commence. First however all the heat shields have to be removed - and what a mess! The amount and extent of corrosion is depressing. I managed to save only a few of the studs that are tacked to the floor pan to secure these shields. And it's here that I realised more differences. The heat shields on the 34 and 42 litre cars are different, not only that, but the studs to secure them are also placed differently! Start of the headaches! The fuel tank is easy to remove, open the "hatch" behind the driver seat, remove the sender wiring plug and un-clip the two fuel hoses. They are colour coded but good practice to mark them anyway, or take a picture. The fuel tank flap is removed easily, then I removed all bolts leaving the tank strap for last. Once the last two bolts are removed, I lowered the tank on a trolley jack. The main feed to the fuel filter is clipped into the fuel tank, so lower carefully making sure nothing is dragged or put under and stress. The tank is very light, but any fuel (remember the surge?) left does make it wobble alot.

So, everything is now out and the fun part can commence. But, I'm off for a shower and dinner. Tune in again tomorrow for more!

blue skies
tony
 
Sorry for the delay in the next bit of this mod - just flat out at present with year-end revisions and exams.
I'm going to take advantage of the better weather today to try to catch up on some work on humpy.
Below is a picture of the hand brake cable connector that I called a "cage". I'm not sure of it's correct name but most motor manufactures use basically the same thing. The picture is off a brake training rig we have at college for the students. The cables are simply put through the open centre section and pulled in opposite directions and clicked into place. It is here that you would seperate the hand brake cable if you change either of the two cables going to the rear brakes or the handbrake cable from the cabin, and don't forget a dab of grease to prevent corrosion.

blue skies
tony

Brake Cable Connector.JPG
 
I know those connectors well, Tony. I spent last weekend under my car replacing the hand brake cables and also replaced the pivoted T-section when I had my centre console out. With all the heat shielding in place, they're tricky to access and very tricky to get undone after 10 years!

Tom
 
I'll be interested to hear how you solve the mounting lug sarga for the heat shielding. I have a similar problem, some of my shielding is torn and needs replacing, but I darent do it as all the nuts are corroded onto the mounting lugs and Im scared of breaking them

John
 
This is becoming a problem for many members, myself included. I'd like to fit the exhaust tunnel cover (part of the aero mods), but I can't as I've barely got any lugs left. I've had a few ideas as to how to combat the problem, but am yet to make any physical progress.
 
Mike (Skipton01) had to use a few cable ties in place of 3 missing bolts to attach my exhaust tunnel cover (i.e., tying the cover & the heat shield togther), but that was when the heat shield was in place. I'm not sure whether that's an option to connect the heat shield itself.
 
So, seeing that you guys have pre-empted me, I'll show you how I went about sorting the stud issue on humpy. I have two problems to contend with, some of the studs have snapped off due to corrosion, and others are not in the correct location to accept the new heat shields for the larger fuel tank. I also had to remove a couple of studs.

To remove them is easy - dremmel with a cutting disc and then grind the remaining stub away. Where I had to provide for a new fixing, I lined up the heat shield and marked the floor pan. I then drilled a hole, starting from 2mm and gradually increased it to 10mm. Some epoxy sealant and a riv-nut crimped into the hole completes the repair. Obviously, primer before and after the sealant. Audi use the same process to secure the Webasto pump to the right side floor pan and indeed many other components. The riv-nut is a captive nut that is fixed in a similar process to a rivet, it just needs it's own tool of course.

All it now needs is a stainless steel 8mm bolt and washer and, hotstuff's your uncle! :)

Below is a pic of the cut stud, circled and the new riv-nut in position.

blue skies
tony

Heat Shield Fixing.JPG
 
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In previous posts where members have expressed an interest to upgrade fuel tanks, the issue of the exhaust layout is often a discussion point. The exhaust system must be changed to accomodate the larger fuel tank - there is no getting away with it.

I took some pics of the two exhaust layouts for a comparative. You will note that the 34l version has a more flowing run as opposed to the angular curves of the 42l version. I cut the exhaust in the center tunnel and then used a connector to bring the old front section and doner rear section to make a whole. The mountings are all the same. This was perhaps the easiest of the challenges. The exhaust will soon be modified even further.

blue skies
tony

Exhaust 34l.JPGExhaust 42l.JPG
 
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Just a quick update on the fuel tanks. The 42l unit has the same anchor points as the 34l with the exception of an additional mounting on the left side as shown in the pic below. Apart from the size and section profile, the tanks have the same filler necks and depth. The fuel accumulator is identical, the only difference being the fuel level sender which is clipped into the accumulator. On another post I described the issue I have with a fuel gauge that has beeen fooled into working because it reads the level of fuel in a different manner. This issue will now be resolved and my retro fitted DIS will also compute the distance to empty correctly :).

I took the opportunity to remove the fuel accumulator to strip it down and clean it. It was full of a black gunge that blocked some of the sieve holes - brake cleaner did the trick. The fuel tank itself was also washed out with petrol. I also had to fit a new stud to the tank - the heat shields attach to the tank as well.

@Spike, the fuel accumulators from the two tanks are the same in every way, they have a spring loaded base that can accomodate various depth fuel tanks.

I refitted the accumulator with a new seal and cleaned the outside of the tank - it looks like new now. It was now time to present the tank for a trial fitting - and - oh my! My intention was to retain the fuel filter, humpy has the older canister type, but when it came to fitting the tank - the filter assembly was in the way - in fact, the circled anchor point in the pic uses one of the filters' bracket locations. What a shock - the filtration system would now have to be replaced! OK, I said, lets get on with it, removed the old filter assembly and tried my dry run again. Well, more issues ... due to the 34l's smaller size, the fuel lines from the filter assembly curve into the space required to accomodate the larger capacity 42l tank. So, out it came again, I used some plastic tubing, inserted it into the metal fuel lines and proceeded to bend them out of the way so I could get the tank in. The tubing is used to prevent kinks in the metal fuel lines.


Do you think it worked now? No! humpy is fitted with the Webasto heater, and on the right rear floor pan lives the dosing pump that delivers fuel to the front - that would have to be moved too! I've posted a pic of its location - remember the corrosion I mentioned - I had a thought to replace it - until I saw the price :eek:! Easy to remove, fuel line, plug and two bolts. Now the tank could be fitted, and it went in like a charm!

More tomorrow

blue skies
tony

Tank 42l tab.jpgWebasto Pump.JPG
 
Hi Tony
Thanks for the update on the exhaust and fuel level sender unit.
There has been some discussion about compatibility with old and new instrument clusters and the way the different level sensors work but it looks like you can just swap the level sensor assy to suit the cluster.

Cheers Spike
 
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