AEL into C5 chassis A6, mid-perf daily driver

ogsv

New member
Joined
Apr 25, 2017
Location
Norway
TDI
Audi A6 2,5 TDI
Hi all fellow TDI modders, tuners, geniuses, novices and all in-between.
I've been reading TDIclub for the last 15 years or so, ever since buying my first Audi A6 C4 2,5 TDI - the engine that I've been in love with ever since.
However, as my projects have all been gassers until now, this is my first post on this marvelous forum.
My last C4 TDI suffered a brutal death after a rather unpleasant encounter with a bus last summer, and even though I immediately got another one, I have to admit that 27 years after the introduction of the C4 chassis, it's starting to feel somewhat dated. That's what got me thinking about getting the AEL engine into another chassis. As cars are more expensive here in Norway than pretty much any other place in the world, my budget only allows for a C5 (1998-2004) A6, but I kind of like that chassis anyway...
So the current plan is:
  • Remove AEL engine from wrecked C4 - done!
  • Remove complete drivetrain from wrecked C4
  • Remove complete engine wiring harness from wrecked C4 (in case it should be needed)
  • Rebuild AEL engine
    • Remanufacture head - valves, guides, seals
    • Upgraded turbo - Holset HE221W or Garret GT2260v (unsure about going VNT...)
    • DSS Ultime2 nozzles
  • Source good & cheap A6 2,5 TDI V6 quattro
  • Mount AEL into C5 chassis
  • Enjoy another 400.000 km of problem-free motoring
I'm not looking for extreme performance, just a drivable 200+ hp and 400+ Nm.
Things I have yet to decide or figure out:
  • How to make the V6 ECU run the I5 AEL engine
  • Fit the 01E gearbox in the C5, or make the AEL fit the Tiptronic?
Yes, I know the Tiptronic is a PoS, but considering that my daily 340 km commute is 320 km at 120 km/h and 20 km of near-standstill congestion, I figure it might possibly survive?
Any and all feedback will be highly appreciated, and I hope I can make this thread entertaining in due time :)
 
Last edited:

ogsv

New member
Joined
Apr 25, 2017
Location
Norway
TDI
Audi A6 2,5 TDI
What's a thread without pics :)
The first

ABT Tuned (turbo, custom map, suspension)

The donor

The AEL in the workshop, ready for overhaul
 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
May I make a suggestion: As much as you love the AEL, your desire for 200 HP is modest and can be easily achieved with a 4-cylinder TDI. With an appropriate 6 speed 01E (e.g. GBB code), you will see a huge improvement in your fuel economy while enjoying your targeted power. I only suggest this in view of the length of your daily commute.

If you insist on an AEL swap into a C5, a couple of suggestions: I looked into this for a long time but while theoretically possible, I never found one example. But if anyone has successfully done it, it will be your Nordic friends in Finland. :)

Second, the ancient MSA ECU of the AEL does not effectively control a VNT turbocharger. Best that you here retain a wastegated turbo. Your countryman Petter Lønning can set you up with a Holset unit.

It has been said that the ECU can be reprogrammed to change the number of cylinders, but the V6 ECU may be impossible to adapt because that engine uses a VP44 pump with its own ECU instead of VP37. If the theory of reprogramming the cylinder count in the ECU works, you might use an ECU from an AFN TDI.
 

Frans

TDIClub Enthusiast, Vendor , w/Business number
Joined
Apr 25, 2011
Location
Netherlands
TDI
Golf MK2 TDI
This swap has been done before all though it's not super easy.

I would recommend to go for a manual quattro at the same time.


Few tips:

-Don't rebuild that AEL. These engines are build to outlast us all. Even with high hp ;-).

-Go with a manual gearbox

-fabricate some engine brackets to fit the AEL into the b5.

- You can use the ecu from a t4, 151 hp. That's a 5 cylinder and VNT. You can even use the turbo. With tune it will give you approx 170/180 without even changing the nozzles.
Changing the turbo to a slightly larger one, 2256 or so will get you over 200hp (combined with other nozzles)

-wiring will need some work to...
 

diffas

Veteran Member
Joined
Jun 25, 2008
Location
Finland
TDI
B5q A4 Avant 2.5TDi+, B7q A4 Avant 3.0TDi
Or just use v6 and remap it 200+ and get overall better performance.
 

ogsv

New member
Joined
Apr 25, 2017
Location
Norway
TDI
Audi A6 2,5 TDI
Wow, that's a lot of good feedback already :)
May I make a suggestion: As much as you love the AEL, your desire for 200 HP is modest and can be easily achieved with a 4-cylinder TDI. With an appropriate 6 speed 01E (e.g. GBB code), you will see a huge improvement in your fuel economy while enjoying your targeted power. I only suggest this in view of the length of your daily commute.
(...)
Second, the ancient MSA ECU of the AEL does not effectively control a VNT turbocharger. Best that you here retain a wastegated turbo. Your countryman Petter Lønning can set you up with a Holset unit.

It has been said that the ECU can be reprogrammed to change the number of cylinders, but the V6 ECU may be impossible to adapt because that engine uses a VP44 pump with its own ECU instead of VP37. If the theory of reprogramming the cylinder count in the ECU works, you might use an ECU from an AFN TDI.
Thanks for the feedback. I do realize that a slightly more modern 4-cyl would be able to get better fuel economy, but how much better, and how about reliability? We all know the I5's can exceed 500k km with nothing but oil and belt changes - is the (110 hp?) 4-cyl equally well-built? Then there's the sound...

It would be fairly easy to make a box that controls the VNT using the signal for the N75 as input, but if I can get good results without doing that, even better :)
This swap has been done before all though it's not super easy.

I would recommend to go for a manual quattro at the same time.

Few tips:

-Don't rebuild that AEL. These engines are build to outlast us all. Even with high hp ;-).

-Go with a manual gearbox

-fabricate some engine brackets to fit the AEL into the b5.

- You can use the ecu from a t4, 151 hp. That's a 5 cylinder and VNT. You can even use the turbo. With tune it will give you approx 170/180 without even changing the nozzles.
Changing the turbo to a slightly larger one, 2256 or so will get you over 200hp (combined with other nozzles)

-wiring will need some work to...
I'm not going to touch the bottom of the engine in any case, but you say it's not even worth cleaning and reseating the valves, and changig seals? Well, in that case, time and money saved :)
If I source an ECU from a T4, do I need the full harness from the T4 as well, or could I use the AKE/AKN (V6) harness as a base, or the AEL harness..?
More power is always a good thing, as long as it remains drivable and economic when I want it to :)
Or just use v6 and remap it 200+ and get overall better performance.
Thanks, but not ready to try my luck with a V6 in a 70k km-per-year daily driver. They give these cars away over here now, that's why I'm considering using one as a base for this project. An I4 TDI C5 is worth 4-5 times more.
EDIT: Just had a look at your project - damn that's a pretty impressive V6 build! You almost got me thinking there for a second... :D
 
Last edited:

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
Agree with Frans on the T4 ECU.

I myself fantasized about a 5-cylinder TDI in a C5 All-Road for a looonnnng time. But it is nevertheless a fantasy borne purely out of emotional attachment but making no financial or practical sense, especially for a daily driver. The more you modify anything, push performance envelopes and deviate from OEM engineering, the more you compromise reliability and are your own warranty.
 

adamss24

Veteran Member
Joined
Nov 2, 2005
Location
Great Britain
TDI
audi a4 2.5 tdi 98 quatrro 6speed
A proper built v6 tdi is better in any respect than the inline 5 cyl. 300Bhp is just a turbo and injector swap away and fuel economy increases as well. Once YOU get to know a v6 tdi is the rather easy to live with and the Achilles heels have dropped in prices over the years and are rather cheap to repair !
 
Top