Audi 2.5 TDI conversion into '01 A4Q Avant

I have learned a fair bit from reviewing other conversion posts on this forum. Here is another take on this conversion:
Audi A4 quattro Avant 2001 - 1.8T (AWM) 5 spd manual - converting to 2.5 TDI (AFB) 6 spd manual.
I started with the purchase two years ago of the 1.8T Avant 5 spd - high mileage engine and very nice condition body. The car was a good price.
There is quite a bit of work to do on the car before it is ready for the TDI engine to be dropped in. I first tackled the suspension and related under body stuff. Fortunately I have a lift in my garage to make this work much easier. The conversion required a different (v6) front support frame and dropping the rear frame for access to the fuel tank (replaced with TDI version). Given this work, I replaced all the suspension rubber, bushings and some other parts. Rebuilt calipers, wheel bearings, and all axles and powder coated all the metal pieces.
I found a used AFB v6 TDI motor that had been brought into the US. My source also provided a rebuilt 6 spd manual transmission and a few of the other necessary parts needed for the conversion (shifter assembly and instrument cluster). I have been able to find most of the other parts from the UK and Europe. It has taken a while to get everything together.

Most of the gasser stuff gets removed:
Fuel tank, fuel lines, fuel vapor/emission filter under spare tire well (along with all the piping/hoses), more stuff in the left rear wheel well, engine, engine wiring harness, battery cable to alternator, intercooler & bracket, AC lines to bulkhead, front clip, intercooler pipe under radiator, front subframe (if 1.8T), front axles, air filter box, and high pressure steering hose.

To prepare the engine bay I had to find some heat shields and sound insulation unique to the 2.5. They apparently have a black acoustic insulation on the two strut tops, and two pieces along the top and bottom of the firewall. I was able to order new parts, all but the left strut top (I got the very last firewall piece from a source in the UK). The metal heat shields are similar to v6 gasser models along the sides and rear corners (by the steering stuff). There is one shield on the tunnel that I have not been able to get (NLA). I will use some adhesive back heat/sound barrier here instead.

The intercooler supports are both unique to the v6. They rivet right in place to pre-existing holes. Bracket include bolts for AC dryer. Fuel lines and fuel filter bracket in place. I modified the bracket a bit by welding the N75 valve bracket to it - as the valve sits underneath the fuel hoses (as far I can tell).

Replaced gasser Quattro tank for TDI Quattro tank. What a piece of sculpture this is. Also removed all the vapor emission plumbing – a lot of stuff located all around the underside of the car. Replaced the hard fuel lines as they are different at both ends (tank and engine). Plus the TDI version has a stainless steel dual return pipe to aid fuel cooling.

I'd like to follow your thread but could you do one thing? Can you upload your images to the tdiclub picture server and then post the images in your thread? Instructions for how to do this is in my signature. tia

I have added photos to the picture server as you suggested. This looks like it will work better.

Lots of progress in the last few days. I had the engine stripped down to the block and have reassembled most of this weekend. I have done lots of prep and cleaning in the past month (as well as ordering additional parts I had not anticipated). All new gaskets, o-rings, hoses, etc. Unfortunately I missed taking a photo of the bare block. The photo below is already in progress on the buildup.



The only things left in place were the crank shaft and main bearings. Honed the cylinder walls and installed new rings on the pistons. The bores and pistons were still in good shape. Replaced the connecting rod bearings.

I started reassembly by replacing both crank shaft seals. The rear below.



The rear cover and seal in place.



Front flange exposed. Very complex metal gasket shape.



Front seal and cover in place.

Time to flip the engine upside down and work on buttoning up the bottom. Torqued down the new connecting rod bolts. The upper sump uses a sealant between the top and the block. So careful cleaning of these two surfaces was in order.

The upper sump and oil pump reinstalled and ready for the lower sump (which does use a real gasket). I coated both sides with K2.





Now the engine gets flipped over so I can work on all the top side stuff. Some pics of the bores and cylinder head gasket. I set the cams in the correct position before setting them on the block.







After the heads are torqued down comes the installation of the two center coolant pipes. The right side one needs to be installed before the oil filter housing is installed because it is sandwiched between the side of the head and the oil filter tower.

The four coolant pipes. I cleaned up the ends and installed new o-rings. I ended up sourcing some better condition used pipes from Germany and Austria. The ones on the engine where quite corroded.

IndiaRed said:

I have added photos to the picture server as you suggested. This looks like it will work better.

Click to expand...

Yes! much better thanks.

Top of engine assembly

Installed the oil filter housing next. Views of front and rear.





Following this the oil pipe from the base of the filter to the turbo gets put in. It is down low and would be extremely difficult to get to later. I replaced the crank case filter thinking it was the old style. It turns out it was already the new style. This is one of the later AFB's from 2000. At least that is what I determined from the parts and part numbers. ETKA is a very handy/necessary tool in all the research.

I had to set the engine down on a dolly so that I could remove the engine stand holder. It interferes with the installation of the turbo manifold at the very back of the engine.

Exhaust manifolds in place and the valve from the base of the turbo manifold to the front intake runner. Oil pipe is set in place as well as the intake manifolds. I didn't want to leave too many holes for things to fall into. The exhaust manifolds were next.



Lastly the turbo is set into place. Then the rear facing coolant pipes and small heat shield can be set into place.



Some of the dirty turbo parts from earlier. Cleaned and rebuilt the turbo.

More top of engine

I replaced the old fuel feed and return lines from the injection pump to the filter. The hoses were cracked.



The cam shafts were reground last year sometime. I had the valve seals and guides replaced and valves ground. The guides were in poor shape.



Vacuum pump at the rear of the head. Make sure this engages the correct groove at the rear of the cam. One of the grooves is off center so it is easy to figure out.



Injector. I had these rebuilt by KermaTDI. They replaced the nozzles with the Bosio PowerPlus 683's. They set these for 180 hp. The injectors have a new washer at the base of the injector hole and new o-ring.



The valve cover slips over the injectors. I cleaned the top of the head, set the new gaskets and a bit of sealant in the correct places. The fuel lines are loosely set into place. I need to finish the other side first since you need to install the lowest fuel line connections on the injection pump and work your way up.

The clutch & DMFW

This is currently a dilemma for me. The existing clutch pressure plate is rusty, although wet sanding with 320 grit seems to work to remove the rust. Some minor pitting remains.





My original intent was to use an uprated clutch. So I ordered what I thought was the correct one (for and RS4). Unfortunately it does not fit. I had the DMFW resurfaced. It has some rotational play 1/4", then a slight spring resistance for about 1/8" each way, then a metallic clunk, then a much harder spring resistance.



So what to do now? Opinions welcome. Specific part numbers?

Option 1: reuse the existing pressure plate and clutch disk (not much wear at 8 mm thick still)

Option 2: replace the existing pressure plate and disk with new stock units.

Option 3: replace with some uprated kit. Sachs racing performance kits from Europe?

My goal is to get the engine power up by around 20% above stock. Would this be stretching the stock clutch setup? I could not find any really useful info on the various TDI / Audi forums addressing the 2.5 clutch. Other than the DMFW is a weak point.

I take it this isn't your first time on a v6 tdi?

Very cool to watch this progress.

Yes, it is my first time with the v6 TDI, or any TDI for that matter. The engine part is fairly straight forward. The wiring is definitely more challenging. It is all modified, so we will see if I did it correctly in the next few weeks.

I decided to buy a new DMFW and stock clutch kit for now. I am not going for any crazy power upgrades, just a bit. I have read too many posts about failing DMFW's and the noise they can make as they rattle themselves apart. Mine had a metallic sounding clunk/click just prior to engaging the stiffer springs.

Last night I installed the TDI version of the clutch pedal spring. A bit of a PITA job getting it in. It is quite a bit beefier than the gas version. I am assuming it is to help offset the extra clutch plate clamping force?

Clutch

I decided to try a new stock clutch plate and clutch. I replaced the DMFW as well since the engine had fairly high mileage and it was a bit clunky when moved by hand. New parts below.



Bolted up.



Next, the transmission was moved in place and bolted up with all new bolts. This went in smoothly with both faces parallel before pushing together.


Added not quite 2 liters of Audi transmission oil.

I had to back off on installing the engine until I could get a spare injector to replace one that had a bend cap nut. It prevented the injector from seating in the injector hole. I found a spare injector and just swapped the end nuts. The nozzles had just been replaced by Kerma. The shining cap nut is the bent one.



The injector slot



The spring washer that holds the injector in place.



The valve cover slipped over the top of the injectors

The engine moves in

Finally this weekend I was able to get the engine/transmission installed in the car. It went in fairly easily. There is not much extra room though. I had to remove the fuel filter to give me a bit more wiggle room to get the engine mounts to align. The filter is back in.

The waiting engine bay.



The engine and transmission were mostly assembled on the dolly. I installed the wiring harness and (especially the stuff that sits atop the transmission).



The engine being lowered and rolled into place. I had a small jack under the rear of the transmission to help adjust the approach angle. I also used all four lift points to help balance the transmission better (and to spread the load). I ended up fabricating a couple of lift brackets.



And lastly the engine in place.

That is a clean engine compartment.

And very busy looking.

Nearing the finish

Most of the car is together now. Really just the bumper, coolant reservoir and some plastic covers to install. Oh, and getting the ECM to talk to the cluster....

Engine bay almost complete:



Front radiator and intercoolers. The 1.8T steering cooler bar is the wrong shape and is currently just tied into place while I wait for the AFB version.



Some close ups of the intercooler with their air guides in place.

Underbody views

The front end under the engine is quite busy with the AC pipes, suspension, intercooler hoses and exhaust. Not much extra room here, but it all fit and went together fairly smoothly.







A few shots of the exhaust. This is the used stock exhaust system (very heavy). I had to cut open the catalytic converters to clean them. They were 50%+ blocked. I used new pipe connectors and few new rubber hangers. Everything fit perfectly.

Very nice!!! Ive been contemplating a 2.5 swap, just not sure if I want to run something with little support stateside if I need parts or something. But I know how good those things sound... and the low end torque...!!!

Very Nice!

k-harley - The trickiest part is getting the engine (block & heads). Most everything else is available new from a few European sources and used on eBay.de or eBay.co.uk. I suspect most US based TDI shops should be able to figure out this engine. However, with all the new parts it is not cheap. My goal is to make this reliable for the next 10 years / 100k+ miles.

Started the engine up last week after finally getting the air bled out of the fuel lines. Runs like crap. Did the dynamic tuning check in VAG-Com and advanced the timing at bit on the belt sprocket for the injection pump. Won't rev above about 1,800 rpm and smokes big time. VAG-Com shows the 00550 - Start of Injection Regulation 17-10 Control difference - intermittent. Checked most of the other things that could cause this and have now purchased a rebuilt injection pump from Diesel Bob in the UK. Also, since I am this deep I have new intercoolers and a MAF coming as well.

So, while I am waiting for this I am wrapping up the wiring modifications. There is one wire that shows up on the AFB wiring diagram but is not in any of the wiring harnesses I have. It is wired on the chassis side of the plenum connector to the Airbag control unit. The gasser AWM had this in the engine harness. It is easy to add, BUT, I have no idea how to reference the diagram ECU pin numbers with the pin numbers on the three ECU connectors. The three connectors have pin numbers 1-24, 1-40, and 1-52. So, for example, the ECU has three pin #19's. I have been able to identify where all the wires in the harness connect in the ECU plugs, but there is no pattern that make sense for referencing between the ECU pins identified in the diagram with the physical pins in the three connectors.

So, where is pin 47 (Air Bag Control Unit J234) on the ECU?
Thanks to anyone who may know.

Update - Received the rebuilt injection pump from Diesel Bob in the UK. Two hours later the beast was installed. Engine runs much better and actually revs up like it should. DTC codes have gone. Still smokes too much. Waiting on some new intercoolers (one looks like it is leaking oil, so may also not be holding turbo pressure), and new MAF sensor. I drove it around the block for the first time - saw a few dirty looks from folks left in the smoke wake. It smokes less with the MAF disconnected (running with MAF default setting).

Update - I have about 200 miles on the setup. Running much better now. Still smells a bit too much of diesel in the exhaust. The engine also seems a bit loader than I expected. I currently have the ECU out for tuning to match up with the larger injector nozzles. Recent work/adjustments completed.

Replaced the intercoolers with new units.



The engine was making a hollow knocking sound that I traced to the hydraulic lifters. You could hear this with the air filter disconnected and feel it on one of the fuel lines to the injectors. Pulled the cams and replaced all the lifters and rockers. I should have done this with the engine rebuild. Noise is now gone and I have less smoke.






Turbo - I belatedly noticed that the top of the actuator housing was bashed in. This inhibited the range of motion of the actuator rod by 1/4". I replaced with a new unit and calibrated to start opening around 3-4 inHg and be fully open at 18 inHg.

I got my ECU back from the tuner. "Jetta ,97" on the forum did the tuning - very fast turnaround and fair price. Car runs great now. More power to go along with the larger injector nozzles. Now its time to put some miles on and fix the last few non-TDI items (radio/speakers, etc)...

http://forums.tdiclub.com/showthread.php?t=251621&highlight=marin

5,000 mile update

I have not posted in awhile. So far I have managed 5k fairly trouble free miles. Recently the old fan blade broke apart damaging the radiator and hood insulation. I just finished replacing these items.

The car is a bit stinky when running so I wanted to try and clean up the exhaust a bit. To that end I added the pre catalytic converter that was available on the engines after the AFB (I believe the b6 models had them). This was a matter of cutting off the pipe below the flex joint and fitting a new flex joint and mounting flange for the pre-cat. I had to make a custom flange to mate to the pre-cat flange out of stainless. The hole in the pre-cat is an inspection hole (welded in an 02 bung). That way I can check to see if the element is clogging up.







and finally the pre-cat in place as viewed from the top.



I did need to bend the vacuum pump heat shield a bit to clear the side of the cat.

Further exhaust cleanup

To improve the exhaust further I removed the center muffler (which weighs some 25 lbs) and replaced it with an aftermarket DPF. This filter does not require the computer generated regeneration, but does it passively when hot enough and run long enough at higher rpms - periodically. It is from HJS, a German company.

http://www.hjs-motorsport.de/products/motorsport/diesel-particular-filters.html

This involved cutting out the center muffler and inserting the DPF along with some new pipe and a support bracket. Note, I also added two small pipes that connect to the Audi pressure differential sensor that normally monitors how "plugged up" the filter is. I want to be able to monitor it to verify that it is actually working. The sound of the car running is no different after this swap (my biggest concern initially other than cost).

A side by side comparison of the old and new setup.





I still need to test using the clean white rag held at the tailpipe. Before it would definitely start showing the black soot (along with the soot layer on the back of the rear hatch).

Awesome. Thanks for the update. I like that you're building/modifying the car to suite your needs which in this case includes cleaning the exhaust up. You might be the first guy on this club to do such a thing. As you can guess it's much more typical to yank off all of these after treatment devices. Kudos on the top notch work.

Update. The car just turned 30k miles on the conversion. The exhaust on this car has always been a bit stinky. Last week I was driving when I heard a loud pop. The car then ran really rough with a loud acoustic thumping sound. You could really hear it from the intake area with the hood/bonnet up. Based on some research it seemed likely to be a rocker that came off or a bad cam lobe. So.... I pulled both valve covers and found that one intake rocker on the 1-3 bank was off and two intake rockers on the 4-6 side and one exhaust rocker on the 4-6 side. Some of the cam lobes show significant wear.

I can't believe that all four would have popped off at the same time. So perhaps my smelly exhaust, and not quite the power I was expecting, suggests that some of the rockers may have been off for a long time? Any thoughts?

I am a bit concerned about possibly having bent a valve in the moment when the rocker is coming off. When I turn the crank by hand I hear air escaping from the 4-6 bank.