Project Letty – AMF 1.4TDI Weight reduction, balance improvement/simplification.

dieselfan

A2OC Donor
1. Introduction of Letty
She is a LHD silver low spec 2003 model sold new in Germany 2002. Imported to Norway in 2005 by second owner. Letty had done almost 200' km when we bought her in 2010, not very well maintained but affordable. She was used as my second (solotrip) commuter and had passed 400' km when the servo, head gasket and AC compressor broke down same month and Letty was parked in 2018.

Letty is special for me, all the km we have had together and my personal commitment to not throw usable things into the bin just because I would like a new one... led to that it is natural for me to get her back on the road, in a reliable condition, ready to do a lot of km together with me...again

2. The objektive
And why is weight so important for me? Well... let's that be said very early in this project, weight and “drive-ability” are the main drivers and key words are: Weight-to-power, balance, simplification and consumption

A2 was never intended to be a race car, it was never intended to be a autobahn locomotive or a drift car. My intention is not to try to transverse Letty into something she never can become.

I would just like to help her a little to “dance on lighter feet’s”
(to be a bit more precise; 8.5kg to the hp....)

3. Balance
The weight of the car is important, though one must bear in mind that the “balance”, the actual weight on the front axle compared to the rear axle is a huge factor when it comes to whether I will be pleased with the handling or not... A2 1.4TDI's are to my opinion “nose heavy” and one of my major drivers for Project Letty is to bring this factor closer to 50/50

4. How to loose weight ?

4.1 Remove parts
The intention is to strip off some of the components that are defect and actually not “needed” for my use of Letty. Some parts will be stripped solely to reduce weight.
  • Webasto unit with brackets, hoses and fuel lines
  • Air conditioning system with piping and houses
  • Rear silencer
  • Doble deck
  • Rollo
  • Rear bumper steel brackets and transverse bar
  • Stereo and speakers will gain 3 kg (added Dec28 - adviced by @carbore ?)
  • Oil filler and assy (added Dec28 - adviced by @carbore ? )
4.2 Replace items - will be replaced with lighter options:
  • Downpipe 60mm in stainless steel (will be designed and produced by author)
  • Rear exhaust system (will be designed and produced by author)
  • Servo steering system replaced with manual steering from A2 1.2TDI
  • Rims will be replaced with lighter options
  • AC and alternator bracket replaced with solely alternator bracket
  • 80Ah battery replaced with 55 Ah (since AC, Webasto and servo are removed there are no need for 140Ah alternator and 80Ah battery)
  • 140A Alternator will be replaced with 75A

4.3 Make items
The are also parts that are considered to make lighter versions of to achieve the goal of reducing the weight with 100kg...:All the listed parts do also reduce unsprung weight which again have a very positive contribution to handling and stopping distance

  • Front axle brake calipers (aluminium/magnesium alloy) 4 kg gained
  • Front axle wheel bearing hub (titanium)
  • Drive shafts (titanium)
  • Brake disks centre sections (aluminium/magnesium alloy)
  • Suspension strut top mounts (added Dec29 - adviced by @carbore ? )

4.4 Items to be added (items that are added to achieve a non standard function even if it will add weight...)
  • Towbar (is heavy and work against the weight loss, though very positive wrt balance. Towbar weight is equal to rear crash bar.
  • FIA master key for battery isolation. (added Dec29 - adviced by @carbore ? )

Weight kg​
Power hp​
W/P​
AMF 75hp​
990​
75​
13.20​
ATL 90hp​
1030​
90​
11.44​
AMF 105hp*​
990​
105​
9.43​
AMF LW 105hp**​
890
105
8.48
ANY 61hp​
855​
61​
14.02​
*- modified ECU
**- weight reduced with 100 kg and modified ECU

5. Simplification
Based on a couple of assumptions, it is my opinion that by replacing the electro hydraulic servoassisted steering system/steering rack, with a manual manual steering rack I will reduce the risk of failure and that I would be able to repair the car my selves over night...
Same philosophy for removing AC system and reducing the size of the alternator

6. Aerodynamic Improvements (added Dec28 - adviced by @A2Dreamer )
I will study the aerodynamic details that is mounted to the 1.2TDI and implement on Letty. Proposals for further details will be very welcome since my ovn experience on this topic is very limited...

Would you like to contribute?
  • Do you have proposals for how one can save weight ?
  • Do you have arguments for why I should do different than planned ?
  • Alternative technical solutions ?
  • Improve balance ?
Please do not hesitate to share ?

Content will be updated accordingly, new chapters might be added and corrections will be done to Post #1

(I had window seat with a very nice view at school so I never managed to learn proper English so please correct typos, misspellings, grammar and terminology issues so this thread can be possible to understand for all and so everyone can participate to, I will be happy for every correction) ???
Cheers
dieselfan
 
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Hey dieselfan,

Really looking forward to what I'm sure will be a brilliant thread. Like you, I absolutely hate to throw anything away that can be repaired, reused or repurposed. Also Like you, I have had similar ideas around weight reduction.

Lighter wheels are a must (why on earth try to build a light car then put heavy wheels on it...!). For a dedicated solo car, I would certainly remove the rear seats, and possibly the front passenger seat. I'm very impressed that you're building your own exhaust system and looking at titanium parts, that's dedication!!

Lowering the car and aerodynamic modifications may also get some fuel economy benefit but it's perhaps a bit difficult to retain the original looks of the car.

Improving the balance may be harder still, I imagine that a lot of the weight reduction will be behind the engine bulkhead, further increasing the nose heavy feeling.

I wish you luck and look forward to updates.

Kind regards,

Pete
 
Weight reduction vs. F/R balance - it's two factors that are more like agains each other in this car. Replacing the battery with smaller one, you lose weight but make a balance worse. Remove the seats, same. AC removal, smaller alternator, non powered steering rack + pump removal yep, thats definitely option that works both ways at once. Also I would recommend removal of most of the unnecessary things in the front and maybe replacing some of them with carbon fibre compisite. With carbon fibre there is a question about gains, because bonnet is aluminium and front fenders are made of plastic. But all the heat/noise shielding can be removed and replaced with „gold nasa“ tape. I would definitely suggest take a look at the 3L specific aero parts as it will reduce drag.

I am really surprised with Mg brake calipers and Ti parts as those are pretty expensive upgrades...
 
Hey dieselfan,

Really looking forward to what I'm sure will be a brilliant thread. Like you, I absolutely hate to throw anything away that can be repaired, reused or repurposed. Also Like you, I have had similar ideas around weight reduction.

Lighter wheels are a must (why on earth try to build a light car then put heavy wheels on it...!). For a dedicated solo car, I would certainly remove the rear seats, and possibly the front passenger seat. I'm very impressed that you're building your own exhaust system and looking at titanium parts, that's dedication!!

Lowering the car and aerodynamic modifications may also get some fuel economy benefit but it's perhaps a bit difficult to retain the original looks of the car.

Improving the balance may be harder still, I imagine that a lot of the weight reduction will be behind the engine bulkhead, further increasing the nose heavy feeling.

I wish you luck and look forward to updates.

Kind regards,

Pete

Hi Pete,
Thanks a lot for your positive and valuable replay ?
Sounds like we could be talking for hours without running out of topics.... ;)

I will definitively adopt your advice and add the aerodynamic modification to the build plan. ?
Cheers
dieselfan
 
Interesting project:

I think @BigBang hit the nail on the head re several issues, but my thoughts are. As I mentioned re your comment in the 2021 thread one of the challenges is that the A2 was built to be light so a lot of the obvious stuff people do to lighten cars for motorsport has been done by Audi at the time of design.

Battery:
Id go for a motorsport "gel" battery like Varley or Odesey. I run a Red Top 25 in my Elise which is 1n 1800 petrol and that has no issues cranking. These have better CCA than lead acid and are about half the size. You can also mound then flat or upright. https://www.demon-tweeks.com/varley...VBO3tCh1VTwQEEAQYASABEgIiGPD_BwE&gclsrc=aw.ds

As said that will take weight out the read though.

Sound Material:
Good call, factory stuff can be heavy so the motorsport stuff can be more efficient, but its still not light https://www.demon-tweeks.com/uk/cool-it-acoustical-and-heat-control-mat-245853/

Aircon and Heater:
No issues there, if you can make a billet alloy one that would be great.

Rear crash structure:
I wouldn't do that one, I left the side crash bars in my Elise doors. I suppose you could hole saw it a bit without losing too much crash structure.

Brake stuff:
If you can machine that then well done, obviously you need a lot of skill and confidence for something as critical as that. As with much of this if you can find any motorsport stuff then its probably a good option (did anyone race Polos anywhere?)

Random ideas:
Replace stereo/speakers with smaller phone based stuff maybe a removable/detacable amp/speaker combo.
Maybe some of the windows could be replaced with perspex.
Oil filler head and tube, remove and bung
Washer filler, remove and bung
Seats, replace with racing seats (not super comy though) and if you can go with a fixed mechanism they are lighter than factory sliders.

Im in the middle of replacing some coolant parts so ill have a look around for ideas when im next on mine.
 
Weight reduction vs. F/R balance - it's two factors that are more like against each other in this car. Replacing the battery with smaller one, you lose weight but make a balance worse. Remove the seats, same. AC removal, smaller alternator, non powered steering rack + pump removal yep, thats definitely option that works both ways at once. Also I would recommend removal of most of the unnecessary things in the front and maybe replacing some of them with carbon fibre composite. With carbon fibre there is a question about gains, because bonnet is aluminium and front fenders are made of plastic. But all the heat/noise shielding can be removed and replaced with „gold nasa“ tape. I would definitely suggest take a look at the 3L specific aero parts as it will reduce drag.

I am really surprised with Mg brake calipers and Ti parts as those are pretty expensive upgrades...
Hi @BigBang
Thanks a lot for your positive and valuable replay ?
Fully agree to the challenge wrt that a lot of the planned weight reduction will work against the wanted balance improvement. That is also way I have looked into several titanium/alu/mg parts at the front end of the car.

You comment that these titanium/alu/mg are quite expensive upgrades. Yes, if I had to buy them. My situation is that I have a lathe in my garage, and I am educated as a toolmaker and have luckily some access to cheap pieces of titanium/alu/mg. So for me it's more a matter of time. My job disappeared with the first lock down so time is much easier than money right now....

Carbon fibre composite is very interesting but at this stage I will have to wait a little until I find some that can co-operate with me. No doubt that I would really like to make a new carbon front ....

Please, can you detail out which parts you recommend to remove?

Cheers
dieselfan
 
My weight cutting advice would be not to over indulge over Christmas and avoid the Christmas pudding but of course it might be a little late for that now ??
Hi @A2Z and thank you for the contribution to the weight reduction advice :D I am 1.9m long and have last years reduced weight 11kg down to 80kg and can manage 2-3 more but then I am at a stage when I pre fare to make titanium replacement parts.... ;) compared to stop eating ?
Cheers
dieselfan
 
Interesting project:

I think @BigBang hit the nail on the head re several issues, but my thoughts are. As I mentioned re your comment in the 2021 thread one of the challenges is that the A2 was built to be light so a lot of the obvious stuff people do to lighten cars for motorsport has been done by Audi at the time of design.

Brake stuff:
If you can machine that then well done, obviously you need a lot of skill and confidence for something as critical as that. As with much of this if you can find any motorsport stuff then its probably a good option (did anyone race Polos anywhere?)

Random ideas:
Replace stereo/speakers with smaller phone based stuff maybe a removable/detachable amp/speaker combo.
Maybe some of the windows could be replaced with perspex.
Oil filler head and tube, remove and bung
Washer filler, remove and bung
Seats, replace with racing seats (not super comfy though) and if you can go with a fixed mechanism they are lighter than factory sliders.

Im in the middle of replacing some coolant parts so ill have a look around for ideas when im next on mine.
Hi @carbore
Thanks a lot for your positive and valuable input ?
Battery and heat resistant cloth are both new brands to me and very useful.

? 10+ for the comments relates to the safety aspect of the project. Rear crashbar will be replaced with TuV approved towbar weighing less than the original crashbar ... for the brakeparts, I fully agree that to mess with them is NOT good and I would not have done it unless I had access to FMECA calculations and state of the art material testing equipment.

Random ideas:
Stereo - brilliant, now added to my list, 3 kg gained ?
Windows - cannot use PMMA (perspex) nor PC, due to norwegian MoT rules. Front window from A2 1.2TDI 3L is a possibility as it is 50% of the standard weight...
Oil filler assy and dipstick - already stripped and replaced with Polo solution
Washer assy - Tank, assy and motor removed and replaced with Audi A6 4F2 plastic bag located beside battery, will improve balance ? Thanks?
Seats - there you really got me to think.... will probably fail MoT though very attempting.... 30 years ago I had great fun competing in several boat race classes and then I made ultra light epoxy seats, direct cast of my butt... so should fit no other... :D
Cheers
dieselfan
 
For me that has closed the oil inlet, this one is interesting. Could you elaborate or perhaps share a photo?

Oil filler assy and dipstick - already stripped and replaced with Polo solution

Edit: out of curiosity, have you replaced the oil pump chain tensioner on any of your longrunners?
 
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For me that has closed the oil inlet, this one is interesting. Could you elaborate or perhaps share a photo?

Oil filler assy and dipstick - already stripped and replaced with Polo solution

Edit: out of curiosity, have you replaced the oil pump chain tensioner on any of your longrunners?
Hi Ole,
Shall send you a picture of the Polo solution I will use for Letty as soon as I am back home from Nissedal.
Both AMFs were bought at 190' km ish and I have run them until above 400. None of them have had any sign of rattling...
Though, Ms's BHC 2005 started to rattle at 205'km, luckily not increased over the last 10' so I will hopefully look into the issue when Letty has passed the MoT.
Cheers
dieselfan
 
Thanks for the follow up @dieselfan based on that other comments you obviously have a lot of technicall background so im very interested in what you get up to including ".........unless I had access to FMECA calculations and state of the art material testing equipment"

My machining experience is limited to watching "This old Tony" but I did buy and restore a dead Hobbymat Lathe/Mill a year back and managed to make a jack adapter for my Discovery 3.

Cant wait to see what you get up to.
 
Random ideas:
Stereo - brilliant, now added to my list, 3 kg gained ?

Looks like you might be ok for the Christmas pudding after all ??
 
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See you already have a plan for the front brake discs. Are you deleting ventilated discs and going for solid, single thickness discs with the custom alloy bells.

On the discs, trim the outer dia to match the pads. As an example, Audi do this on some RS models and reduced disc O/D from 345mm to 340mm.

Not sure if it's applicable to the A2 but they often match drive shaft torsional stiffness (different dias / hollow / solid) to compensate for different shaft lengths. Something to watch when making your own parts if you want to minimise torque steer

If you can find the data, tyres from different manufacturers can vary in weight, probably in the region of 0.7 kg for an A2 size tyre

If not already fitted, alloy rear drum brake cylinders are an option

Cheers Spike
 
See you already have a plan for the front brake discs. Are you deleting ventilated discs and going for solid, single thickness discs with the custom alloy bells.

On the discs, trim the outer dia to match the pads. As an example, Audi do this on some RS models and reduced disc O/D from 345mm to 340mm.

Not sure if it's applicable to the A2 but they often match drive shaft torsional stiffness (different dias / hollow / solid) to compensate for different shaft lengths. Something to watch when making your own parts if you want to minimise torque steer

If you can find the data, tyres from different manufacturers can vary in weight, probably in the region of 0.7 kg for an A2 size tyre

If not already fitted, alloy rear drum brake cylinders are an option

Cheers Spike
Brilliant @spike ?
Your disk ideas are amazing.
Of all the unsprung weight at the front axle I have considered the disks to be easiest to tailor made with the equipment I have at hand. My head is filled with ideas and I am for the moment checking technical datas to try to find out which route to go.
  • Alu/mg hub with carbon disk mounted floated
  • Alu/mg hub with modified (remove all other than the area pads are in contact with) solid disk mounted floated
  • As above but with 30% of the surface drilled
  • Use the lighted solid disk I can find with approx 280mm diameter and drill out 40% of the surface
Very useful info related to drive shafts? I will use approx 48mm Ti tubulars and might solve the issue you highlight by using different wall thickness.

Tyres & rims - I have been reading "wheel treads" most of the day.... to try to find the lightest 15 inch rims with approx 6" width. When you say that there is a potential of 0.7kg per tire I better understand that I should pay more attention to tires too....:oops:

Rear brakes: I have alu sylinders fitted to Letty now. (quite corroded due to the salty roads and the moister that sets in the brake dust)
I have considered to change to disks at the rear end too due to that I am not very pleased with the combination of disks at front and drums at the rear. When I brake on a straight road it is almost ok but I can feel that front disks starts to brake much earlier than the drums at the rear. If I manage to reduce the weight with 100kg, this will be much worse. When I brake hard into a curve it is even worse until I reach full pedal pressure or the ABS starts to interfere ....
Is there anyone with disk brakes on the rear axle that can share their experience?

Cheers
dieselfan
 
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Brilliant @Menno, very valuable information ?
To reduce unsprung weight with 1kg per rim sounds like a miracle .... and well worth the 90 euro.
I do not have a CNC millingmachine that is spot on for this job my selves but will check around.

What do these A3 rims weigh and what are the dimensions ?

Cheers
dieselfan
 
Brilliant @Menno, very valuable information ?
To reduce unsprung weight with 1kg per rim sounds like a miracle .... and well worth the 90 euro.
I do not have a CNC millingmachine that is spot on for this job my selves but will check around.

What do these A3 rims weigh and what are the dimensions ?

Cheers
dieselfan


5,7kg original..... In the link more info.
 
Seats - there you really got me to think.... will probably fail MoT though very attempting.... 30 years ago I had great fun competing in several boat race classes and then I made ultra light epoxy seats, direct cast of my butt... so should fit no other... :D

If you've not already done it, I would remove the rear seats, parcel shelf and false floor in the boot. I took these out for the summer and there's a lot of weight in them:

Rear seats, nearly 16kg each:

IMG_20200520_151810988.jpg


False boot floor, nearly 5kg

IMG_20200520_152006730.jpg


Parcel shelf, just over 3kg:

IMG_20200520_151939906.jpg


Together they are the best part of 40kg, with the advantage that they are easily removed/reinstalled.
 

5,7kg original..... In the link more info.

Brilliant @Menno ?

So with this new info it seems clear to me that I have paid too little attention to rims and tyres where one can gain "several Kg" while I have considered to earn 0,01 Kg on buying wheel bolts of titanium..... Luckily, I have been guided in the right direction ?

@Menno 's rim recommendation: Audi A3 "pepperpot" 8L0 601 025 E 6J x 15H2 ET38 5 x 100 5.7 Kg possible to machine down to 4.7Kg

Do anyone know even lighter 15" rims or are these the ultimate one can buy used for decent money ? (up to 400£ a set ish?)

Cheers
dieselfan
 
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