Cleaning up 2.5 TDI AFB exhaust

[IndiaRed]

I have recently converted my 2001 Audi A4 b5 Avant Quattro 1.8T into a 2.5 TDI with the AFB v6. These are not available in the US - hence the conversion. I currently have the stock exhaust system with the two catalytic convertors. The cats were mostly blocked up so I cut the pipe and cleaned them as best I could (not sure if they are actually still working). The exhaust is quite smelly and sooty. I would like to clean the exhaust up.

My question is what aftermarket exhaust components can be retrofitted to this car/engine? There is not a lot of room under the car for cans. Maybe replace the center muffler?

I found one aftermarket combination diesel catalytic converter and DPF made by HJS (part number 93 11 2004). The image of the downpipe looks correct. I am not sure if the can will fit.

http://www.hjs-motorsport.de

I am also thinking of adding a methanoll/water injection setup to cool the gases and thereby reduce NOx emmissions. An Adblue systems looks to be a bit more complex with the tank, injector, and controls.

Other thoughts / ideas?

Thanks,
Sven

 

[adamss24]

That looks like a FWD exhaust/ catalyst, it won't fit the Quattro...

 

[IndiaRed]

That looks like a FWD exhaust/ catalyst, it won't fit the Quattro...

Thanks for catching that. I believe you are correct. The manufacturer did not distinguish between the AWD and FWD manual transmissions.

Do you think the b6 pre-cats (that attach directly to the turbo) would fit? The space looks a bit tight, but I can't imagine the firewall / trans. tunnel is that different on the b6. I could try that along with some replacement main cats. (from IMASAF). BM catalysts in the UK make some aftermarket cats. I may be able to splice them in.

Would deleting the center muffler increase the exhaust sound much?

 

[adamss24]

If you're using the b5 v6 Quattro exhaust then the pre-cat in your picture won't fit as well ! The b5 Quattro uses a slightly different setup with a cast iron link pipe after turbocharger. What do you want just another set of cats ? Used are ok ? I have 2x V6 tdi Quattro b5 , on one i want to building a 3" exhaust fr turbo back. I will have to delete The CATs... To make room for the larger bore pipe...

 

[IndiaRed]

Thanks, I do have one set of spare cats. with downpipe - although somewhat clogged at the front of the cats. (seen through a boroscope). Cleaning suggestions? On the set on the car I ended up cutting the pipe open to clean, although I suspect I may have ruined the cats trying out various solvents....

If one removes the cast iron elbow from the turbo charger on the b5 will the pre-cat physically fit in the space? It looks tight between the vacuum pump and turbo mount where the coolant hoses attach. If it did fit I would then shorten the b5 downpipe and reposition the flange to mate with the pre-cat.

 

[adamss24]

The angle on the downpipe is very, very different and the b5 vacuum pump is also different so the b6/c5 precat won't fit the b5... I would try power washing the cats with hot water and forget about them...

 

[IndiaRed]

The angle on the downpipe is very, very different and the b5 vacuum pump is also different so the b6/c5 precat won't fit the b5... I would try power washing the cats with hot water and forget about them...

Update - I was able to make the precat work on the b5. I had to deform the vacuum pump heat shield about 3 mm to keep it from touching the cat. Other than that there were no clearance issues. It was not too difficult. See post #27 at this link for photos/description.

http://forums.tdiclub.com/showthread.php?t=443296&page=2

 

[IndiaRed]

Part 2 - 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/product...r-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.

 

[adamss24]

You will do better by removing the cats altogether, i run a hybrid turbo on my daily allroad at about 240 Bhp and a full 3" exhaust system with 2 small backboxes, sounds nice and throaty on full throttle and quiet on cruising... The AFB engine needs updating with a better turbo and slightly larger nozzles which will wake up the engine and bring it into the 21st century ! In stock form 150 Bhp is rather mediocre especially as you can get a 1.9 tdi golf from factory with 20% better fuel economy !!!

 

[adamss24]

You will do better by removing all restriction on the exhaust path, the AFB power output is rather mediocre when you can get a pd150 golf with same power from factory and 20-30% better fuel economy !
I run a dual 3" turbo back exhaust on my daily driver (audi allroad tdi) at 240 Bhp and it sounds nice and throaty on a full throttle and quiet on a motorway drive ! What the AFB needs is better turbo and larger nozzles and it will bring it in the 21st century ! One of my hybrids with larger allroad injectors, full decat exhaust system and a 3 plunger pump will give you over 250 Bhp which will be a decent power to weight match for the 4 wheel drive system !

 

[IndiaRed]

I have done some power enhancements. Installed the Bosio PP683 injectors set to around 180 bhp and had the ECU tuned to work with the larger injectors. Car runs nicely. Would using one of your hybrid turbos be beneficial with my current setup? or would I also need to retune the ECU? I had it dyno'd yesterday. 141 whp and 275 ft/lbs. Assuming a 20% AWD drivetrain loss that puts that equates to about 176 bhp.

The attached torque curve seems a bit spikey. Is the rapid drop off after the 2,200 rpm peak indicative of any problems?
Thanks,

 

[adamss24]

Ok, so that's wheel power not crank ! It seems fine as i expect the bosio PP683 to flow 240 Bhp max... The dyno plot is a bit weird as i am expecting a smooth climb all the way to 4000 rpm's however your turbo control is a bit off and creates the power spike you see ...

With one of my hybrids you should see a mid range kick and a bit more top end, it should also pick up a couple of hundred rpm's quicker especially as the exhaust is free flowing... I have a 2004 audi allroad that i am playing with now, i will post a power printout next week : hybrid turbo, bosio race 683, 4 bar map sensor, alloy boost pipes, solid intercooler, etc. It's as fast as a golf R so i reckon about 300-310 Bhp and it did 160 Mph ! EGT were stable at 800 C max !!!

 

[just20409]

hi adams's i am struggling to contact you at moment...as i i have said in earlier i have just bought a 2004 a4 2.5tdi avant quattro which i am looking to tune/decat and would love your input

kind regards J