VW Touareg TDI, Audi Q7 3.0L TDI engine technical details and FAQ

back to 1000q: VW Touareg TDI buying guide

Introduction

The VW Touareg TDI and Audi Q7 TDI use the same 3.0L TDI engine, model name "CATA".  It's a V6, common rail injection single turbo diesel engine.  Here are some FAQ and technical details on the V6 TDI engine.

If there is a 2011 or 2012 Audi A4 TDI confirmed for the US or Canada, this engine is the obvious choice since it's already set up for the body and Audi quattro (VW 4motion).  No other engine offers this combination of power and excellent fuel economy for mid size-large vehicles.  In the VW Touareg or Audi Q7 TDI SUV it gives more torque than the Touareg's gas V8 (at a much lower engine RPM) with the economy of a V6 midsize sedan.

Since it's a modern common rail diesel, it's quiet running, easy to start, and smoke free.  The emissions treatment system makes it emissions legal in all 50 states.  The Touareg or Audi Q7 qualified for a $1150 federal income tax credit which is now expired.  See 1000q: tax credit and TDI for details.  Power in the Touareg and Q7 are rated at 225 hp and 406 lb-ft of torque at only 1,750 rpm.  EPA rating in the Touareg is 17 city/25 highway, significantly more than the V6 or V8 gas engine Touareg.

Some of the technology on the CATA 3.0L TDI engine is common rail fuel injection which uses extremely rapid piezoelectric (like the vibrating sonicare toothbrush head) injections of fuel at about 29,000 psi!  To compare, the average gasoline engine injects fuel at about 60 psi.  The turbo is a VNT variable nozzle turbo.  Please see 1000q: TDI turbocharging FAQ for more videos, descriptions of VNT, and general turbo information.  The big difference is that it appears the VNT actuator on the CATA engine is driven by an electric motor instead of a spring/vacuum.  The new common rail TDI also use 4 valves/cylinder.

Some differences with the smaller TDI engines are an emphasis on performance.  The 3.0L V6 engine has 50% more displacement than the 2.0L engines in the smaller VW and Audi TDI.  For larger or heavier cars, it could be the perfect engine because it combines performance and fuel economy.  The CATA engine weighs about 490 lbs and compression is 17:1.  The V angle is 90o and the crank pins are 30o offset for even firing.  It also uses twin intercooling to cool the larger air requirements vs. the single intercooler on smaller engines.  The smaller engines do get much better fuel economy but they're also mounted in much smaller and lighter cars.  Each cylinder head has its own common rail.

The 8 speed transmission equipped with this engine for 2011 and later models is designed to handle up to 627 lb-ft of torque so it should be responsive to power upgrades like a chip or tune.

The basic layout of the engine is a longitudinal with a single turbo between the rear of the cylinder head V.  Here's a video showing how the engine is built.  The laser honing process leaves a smoother and harder surface on the vermicular cast iron surface than traditional honing.  They spin the engine instead of the laser because it's probably easier to spin the engine than the laser.

The new engine for 2010

European Audi Q7 for 2010 get a completely new engine for 2010.  This engine is only in European Audi Q7 and to the best of my knowledge, hasn't come to North America yet.  (Thanks for the tip, TDV6)!  The engine is 55 lighter (down to 425 lbs) and uses 2 instead of 4 timing chains.  Using vermicular graphite cast iron crankcase let them cut 17 lbs from the crankcase and cylinder walls, traditionally one of the strongest components in a diesel engine.  6 lbs was cut from the cylinder heads and 4 lbs from the crankshaft.  They also changed some hardware and water cooling lines from steel to aluminum.

The engine itself was plate honed, meaning they used a tension plate to ensure that the mechanical honing was straight.  The UV laser honing smoothes and hardens the cylinder walls for lower friction as well.  These two measures reduced tangential forces by 35%, according to an Audi press release.

Some innovative features on this engine are the new design of intake manifold flaps which increase air swirl during low engine speeds and the turbo shaft bearings were changed to lower friction.  The crankcase and cylinder head also have their own cooling circuits which bypass the crankcase and oil cooler for fastest possible engine warm up and even shuts off during low load to increases fuel economy and reduce emissions.

All engines come with start/stop but this feature has never been equipped on North American engines despite being on their European equivalents.

What is clean diesel?

Diesels are cleaner because of the combination of cleaner fuel and newer technology.  The emissions treatments were not usable in North America due to lower quality diesel fuel until the switch to ultra low sulfur diesel (ULSD).  While the law requires this by Dec 2010, all refineries switched over a while time ago.  This is why some retail fuel stations still don't have the USLD sticker on the pump.  The current emissions systems would fail if the were used with the older low sulfur diesel fuel.  They still sell low sulfur fuel in Mexico so be careful if you travel south of the border (or south-south of the border if you're from Canada).

Emissions are treated in an oxidation catalyst (catalytic converter), then a particulate filter (DPF), then a DeNOx catalyst with Adblue fluid.  The Adblue fluid lasts up to 10,000 miles in the VW Touareg TDI and up to 10-15,000 miles in the Audi Q7 TDI.  The Touareg has a 4.5 gallon (16.9L) tank and the Audi Q7 has a 6 gallon (23 liter) Adblue tank.  The Touareg adblue reservoir is under the spare tire.  In the Audi Q7, the filler cap is located next to the fuel filler cap and can't be removed by hand to help avoid misfueling and the 2 tanks are somewhere under the car.  You can use the lug bolt wrench to loosen the cap.

1500 miles before the Adblue runs dry, the car will give a warning.  If you continue to ignore the warnings and run it dry, the car will not start!  This is because without the urea injection, the car will not meet emissions.  While the engine won't shut down by itself, it won't restart after you shut it off.  Below left is a .pdf  from Audi describing some aspects of the Adblue system on their Q7 TDI.  Click the thumbnail to view the .pdf file.  See 1000q: DPF - Adblue FAQ for details on how this system works.  Below is a quick summary video.

Here is a video showing how the adblue system works.

Here is another video showing the overall emissions system.

Timing chain replacement on CATA V6 TDI engine

The timing chain drives the camshafts, oil pump, and balance shaft.  The first chain connects the crankshaft to the intake camshafts on each head.  The second and third chains connect the intake camshafts to the exhaust camshafts.  The fourth chain connects the crankshaft to the oil pump and balance shaft.  You can see some of the components in this cutaway illustration.

This basic 3.0L TDI engine has been used in Europe for a while but North America has never had any 3.0L VW or Audi TDI engine (the 3.0L CATA engine is specific to North America) so one can only guess about long term reliability.  VW/Audi aren't known for reliable timing chains but my complaint isn't about chain lifetime or reliability because it's not known at this time.  My complaint is that if it does need replacement, it will be extremely expensive to replace.

The newer TDI engine on European Audi Q7 for 2010 switched over to a simpler 2 chain system.  Since it's a completely different engine, it's not possible to swap your chain drive.

Some older gasoline V6, V8 Audi and VR6 VW engines used a similar chain system and needed chain service as low as 100,000 miles.  This is very low for the average timing chain.  There is no specified replacement interval for the chain because it's considered a lifetime component.  The problem is that 150,000 miles is generally considered a normal lifetime for a car and part of the economics of buying a TDI is that the engine should easily last 200,000 miles and beyond with normal maintenance.  There are many TDI owners who have gotten 300-400,000 miles on original engines and normal maintenance.  While the rest of the engine should last a long time, if the timing chain does need service, it would be considered major maintenance.

Servicing the CATA 3.0L TDI engine's timing chain requires removing a number of components to pull the engine/transmission out of the car and tear down the back of the engine.  I estimate that labor, parts, and tax will cost up to $7000 vs. $1000 to replace a timing belt (even at the dealer)!  Timing belts are designed to be easily serviceable and are not considered lifetime components.  Belts normally work like new until they suddenly fail so replacement is considered normal maintenance.

As a rough estimate, the labor to replace the chain is over 30 hours.  Assuming average dealership rates and sales tax, it will be about $4000 in labor.  As an rough estimate, the parts cost of the core parts (not including the sprockets, bolts, gaskets, fluids, hardware, etc.), is over $1000.  Below is a list of just the chains and tensioners.  If you include sprocket replacement and the other misc parts, the total parts cost is about $1900.  And that is internet wholesale pricing-  with tax and dealer markup, I'm sure parts will be at least $2400.

chain tensioner - 059109467e- $40
plastic chain guide track - 079109510f - $50
plastic chain guide track - 057109469g - $40
plastic chain guide track - 057109469h - $40
timing chain - 059109229j - $100
chain tensioner - 059109507c - $80
timing chain - 06e109465aq - $95
chain tensioner - 057109218k - $150
timing chain - 059109229k - $95
chain tensioner - 057109217j - $95
chain tensioner - 057109510a - $25
timing chain - 059109229m - $95
plastic chain guide track - 057109513b - $30

The V10 TDI engine sold in the US spec Touareg TDI V10 used timing gears which have longer life and lower noise compared to a chain.  It probably would have been quieter and more reliable to have a gear drive vs. a chain but the CATA engine isn't designed for it.  Most V engines with overhead cams don't use gears because it's too long of a distance from the crankshaft to the camshaft.  This longer distance is probably why a chain or belt is used on the CATA TDI engine.

Compared to hybrids, Toyota defines a Prius battery lifespan as 180,000 miles and US states with CA emissions warranty it for 10 years.  The difference is that Toyota has a good reputation for reliable hybrid batteries and battery prices are going down.  Audi and VW's reputation with chains isn't as good and labor prices to pull an engine out to replace a chain aren't going down anytime soon.  In any case, if your car needs a new chain and you like the car I'd hold onto it because it's still cheaper than buying another similar car.  Hopefully VW's chain is more reliable on this engine due to a longer history in Europe. 

 

Do you have a comment about this Audi TDI or VW TDI engine?  Please post in the TDI forum.