Juicy technical tidbits

TDIMeister

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The last month has been a very busy one for me as I attended several automotive conferences.

In one, I heard VW present technical details on the new 2.0L common-rail 16V TDI. But probably the highlight for me was sitting front-row-center in an audience at the Professional Motorsport World Expo in Cologne, Germany two weeks ago and having the opportunity to personally ask questions of Dr. Ulrich Baretzky, architect of Audi's LeMans R10 TDI program.

Among my questions, I asked him about Audi's choice of selecting a 5.5L V12 layout for the R10 TDI when a V10 or even V8 would have offered clear advantages in terms of packaging, weight and parasitic losses. I inquired if the 2009 ACO rule change mandating closed-cockpit cars will mean a ground-up redesign of the R10, or an evolutionary revision of the current cars. I asked him to comment on his oft-quoted apparent displeasure with IMSA for penalizing the R10 among other cars in the ALMS field (incidently, he was seated on the same table next to me with members of the Penske-Porsche team, and made a joking comment to be careful with his words in front of his new Porsche owners...). Other questions raised in the invitation-only Q&A luncheon included subjects such as Biofuel use in motorsport; technology transfers between motorsports and production cars; and smoke emission BEFORE the DPF (very, very interesting answer).

Although technical details were not disclosed, my own research revealed a few things... calculating from publically disclosed information, I estimate the Audi R10 engine (and presumably the Peugeot LeMans Diesel engine) is running an exceptionally low compression ratio, certainly under 16:1 and probably even as low as 14:1. The turbocharger compressor can be seen (I stuck my nose in every nook of the displayed engine at the Shell stand) as a GT37 (note to the turbo-swap guys), and the engine makes power to at least 6000 RPM... Cam timing is not very much different from a street TDI, but I feel vindicated in the cam design I made some years ago as being in the right direction.

By the way, if anyone is so inclined, you can go directly to the Bosch Motorsport website and buy every component practically off the shelf similar to the very pieces that went into the R10 engine, and build yourself a common-rail system WITH a Bosch Motronic MS15.2 Diesel ECU to drive piezo injectors (EUR 9,875!!) and swap it into a VE TDI....... You have the money, I can do it for you..... :D
 

GoFaster

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COOL ... One thing to keep in mind is that this being a race engine, it does not have to deal with cold starts at -30 C, which opens up the possibility of lower compression ratio. And it doesn't matter how long the glow plug delay is, although I'm sure they're using fast-heat ceramic glow plugs like the current PD's.
 

bmwvw

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Thats some cool info for us TDI guys and gals for sure. Just curious, what is the limiting factor for rpm vs power on a diesel engine? Is it fuel or cyl pressures, hense the low compression on the R10?
 

mojogoes

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Quote.........
BMW was a pioneer of turbo-diesel power in Touring Cars, winning the 1998 Nurburgring 24 Hour classic outright with a (2.0 litre, 3-Series) 320d. This year privateer Rick Kerry has made a low-key entry into the British Touring Car Championship with a 120d Diesel 2000 car supplied by BMW Motorsport. Currently a 3.5 litre BMW 135dBD is a leading force in Germany’s ‘Long Distance Touring Car Championship’. Ageratec, a Portuguese biodiesel producer is a backer of this car, likewise supplied by BMW Motorsport. Biodiesel is the focus of Scott Racing in the UK, which earlier this year received a grant of £62,000 from national government via regional agency One NorthEast. That grant was specifically for Scott Racing in conjunction with Durham University to develop a biodiesel-fuelled car for the British Touring Car Championship. Currently the project partners are working on a 320d that has the latest E90 turbo-diesel engine. The aim is to have a full Diesel 2000-specification car running in the 2008 BTCC. Scott Racing’s Ian Dixon tells us that this project is independent of BMW Motorsport and is not tied to a specific biodiesel producer. At present potential fuels are being evaluated at Durham University. The aim is not to find the one with the highest cetane number but to find a clean-burning fuel with consistency of supply. For example, Dixon says that fuel from rape seed oil can vary from batch to batch since different seeds provide different characteristics. Dixon is

confident that the right biofuel will provide a cleaner burn than regular fossil fuel, which should permit the engine to rev higher.
 

TdiRacing

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TdiMeister:

We may have been at the same show on Koln.

Here is a pic of the Diesel ECU:


Pics of the LEmans Engine on display in the Shell Booth



 

GoFaster

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bmwvw said:
Thats some cool info for us TDI guys and gals for sure. Just curious, what is the limiting factor for rpm vs power on a diesel engine? Is it fuel or cyl pressures, hense the low compression on the R10?
Traditionally the problem limiting revs has been one of ignition delay. There is a window of opportunity as the piston approaches top-dead-centre for the fuel to mix with the air, ignite, and burn adequately to make power rather than smoke. If that window of opportunity passes too quickly you get either delayed combustion (meaning high exhaust temperature and lots of smoke), or insufficient air/fuel mixing due to not enough time (meaning high exhaust temperature and lots of smoke), or ultimately a complete misfire.

Indirect-injection engines have been able to rev a little higher because they have much more violent air/fuel mixing, but they have power limitations for other reasons.

Presumably the common-rail system can somewhat overcome the limitations of standard mechanical injection systems. For example, you can somewhat overcome ignition delay by injecting the fuel earlier. But a mechanical injection system can only inject the entire shot of fuel earlier. If you inject the whole shot of fuel before TDC, for example, and it all burns at once when the mixture reaches ignition temperature, cylinder pressure goes through the roof. But common-rail systems can play games like injecting a little fuel first, letting that ignite to raise the temperature in the cylinder, then injecting the rest. Or they can play with injection pressure and the duration (in milliseconds) of the injection cycle independently of revs. Cannot do that with either P-D or distributor-pump systems.

Cylinder pressure is a limitation on torque rather than revs. Lowering the compression ratio allows more boost pressure to be used.

The more advanced diesels use four valves per cylinder. This allows better breathing at higher revs while still allowing mild cam timing to be used for driveability and cold starting.
 

TDIMeister

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Very nice that you asked. :) Dr. Baretzky said that the base engine was developed for essentially zero visible smoke raw emissions, even before the DPF. The DPF was there only as a failsafe. He stated that it would be an embarassment in this league of motorsport that the pride of Audi and the hope of Diesels in motorsport went around the track smoking under any circumstance. I was very impressed by that answer and my respect jumped 100-fold. :)

The fuel-spec is DIN/EN 590, basically the same as the Shell V-Power you can buy in Europe. I even have the spec sheet. Which makes the power, emissions and RPM achievements all the more impressive. I've calculated that the R10 would have to run at a lambda of about 1.2 at full-power. Street TDIs would hit the smoke limit at higher lambda values but the R10 makes none on nothing particularly special for fuel. Impressive.

Now when someone here figures out a way to make almost 120HP/L smoke-free on a street TDI, then he'll earn respect. :)
 

TDIMeister

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TdiRacing said:
TdiMeister:

We may have been at the same show on Koln.
Yup, that's exactly the one! On which day were you there, and with whom? I was there only on the last day, when the luncheon with Dr. Baretzky was held and the Motorsport Engines of the Year awards were to be handed out at the closing of the show. You guys were so close to me and didn't let me know you were in the neighbourhood?? :(
 

Rub87

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TDIMeister said:
Now when someone here figures out a way to make almost 120HP/L smoke-free on a street TDI, then he'll earn respect. :)
Someone should be able to get his hands on a 2.0TDI wich Seat sport uses in the WTCC.. there doing 280hp out of a 2.0l also smoke free.. I wonder what turbo they're using..

(seat won in Monza both races, one race in germany.. )

It's the first season they drive the tdi, and Yvan Müller is in the second place overall..
 

TdiRacing

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I saw a demo of a TDI pushing 225hp with a DPF installed and they put a white towel over the exhaust outlet and after a pull it was still white!

Now that is so nice. The filter I want is 1100Euro(has precat and DPF) in one unit. Designed for racing by HJS.
 

TDIMeister

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TdiRacing said:
I saw a demo of a TDI pushing 225hp with a DPF installed and they put a white towel over the exhaust outlet and after a pull it was still white!
Was the demonstration done while the engine was idling, or going full-tilt on a dyno? Makes a big difference, but with a properly operating DPF it shouldn't make a difference anyway.

Speaking of DPFs, I had a Skoda Octavia TDI rental car recently. Just for giggles I stuck my finger in the tailpipe on the car with 25k km, and my finger was perfectly clean!!! Amazing!
 

TDIMeister

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What I wanted to get at with this thread (and the other one I resurrected about compression ratio), is the paradigm in clean high-po Diesels featuring much lower compression ratios than today's stock TDIs; piston bowls that don't completely eliminate the lip (the so-called omega bowl), much wider but not deeper in shape; highest possible injection pressures; and more injector holes, although not too big; long-runner intake manifolds; and cam/head work. Much of this paradigm was already disclosed by a few people for some time. Essentially stock bottom-end (parts bin) 1.9 VEs can be pushing 260 HP and 280+HP on PDs with all parts that are readily available, but I've been reading lately threads where people are not anywhere near that level yet seeking 5% mods like sleeving blocks to accept big-bore pistons and welded stroker cranks that blow budgets out of the water. :confused: :rolleyes:
 

Passenger Performance

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TDIMeister said:
What I wanted to get at with this thread (and the other one I resurrected about compression ratio), is the paradigm in clean high-po Diesels featuring much lower compression ratios than today's stock TDIs; piston bowls that don't completely eliminate the lip (the so-called omega bowl), much wider but not deeper in shape; highest possible injection pressures; and more injector holes, although not too big; long-runner intake manifolds; and cam/head work. Much of this paradigm was already disclosed by a few people for some time. Essentially stock bottom-end (parts bin) 1.9 VEs can be pushing 260 HP and 280+HP on PDs with all parts that are readily available, but I've been reading lately threads where people are not anywhere near that level yet seeking 5% mods like sleeving blocks to accept big-bore pistons and welded stroker cranks that blow budgets out of the water. :confused: :rolleyes:
David, I don't know that I could agree with you more.
One thing to remember with the different bowl designs and lower compression is the need for higher injection pressures and better atomization to produce a quick and clean burn, even in lower temperatures. A lot of the industrial diesel engines I used to work on had compression ratios around 15:1, the bowl shape of the pistons was shallow, smooth, there was no sharp point in the middle like ALH tdi's nor was there much of a lip on the edge of the bowl.
 

TDIMeister

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I recall but can't find the tread anymore where Kerma teased us with Race nozzles with 7 or more holes (can't remember exactly how many). Put this into a PD and with the right supporting components and well-researched mods.... ear shot of a pretty easy 280 HP.
 

TDIMeister

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I recently found a paper authored by Mr. Baretzky on the development of the R10 TDI. It gives some pretty interesting technical insight on the decision-making process in Audi's selection of the maximum allowed displacement for the R10 being driven by ACO air restrictor rules, and also looking at the current state-of-the-art Diesel engine technology. It also rationalizes Audi's decision to go to a counter-intuitive V12 layout, when a V8 or V10 might have packaged better for the race car. I asked Mr. Baretzky personally this question, and his answer was quite enlightening, and not what comes first to mind on the subject. The paper repeats much of what he explained to me.

It's also interesting to read about the combustion development, etc. The stated 200 bar PCP; torque output of about 1100 Nm; and BMEP of 23 bar would suggest an astounding compression ratio as low as 14:1.
 
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devonutopia

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Hehe - A white towel put over my exhaust would soon be black, but my exhaust is "clean" by the standards I have seen. And I hope to be somewhere around 140 to 150hp per litre soon, with hopefully not much more than a cloudy haze coming out the exhaust on full boost.

Some good info above. :D
 

mojogoes

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TdiRacing said:
TdiMeister:

We may have been at the same show on Koln.

Here is a pic of the Diesel ECU:


Pics of the LEmans Engine on display in the Shell Booth



This is the said Bosch motorsport ecu that costs £15,000 and then add another £15,000 for the loom and parts to make it all work plus a few more hidden costs here and there............however there is a much cheaper equivalent from Volvo motorsport coming in at a measly 5000 euros plus another couple of thousand for loom and parts to get you started.
 

Rub87

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Looks like a pretty big undeep piston bowl in the movie.. they're alo putting pistons in without the rod :rolleyes:
 

mojogoes

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Rub87 said:
Looks like a pretty big undeep piston bowl in the movie.. they're alo putting pistons in without the rod :rolleyes:
Yes they use electromagnetic rods the same system that a train uses to hover above the tracks.
 

jackbombay

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TDIMeister said:
I recently found a paper... ...It also rationalizes Audi's decision to go to a counter-intuitive V12 layout, when a V8 or V10 might have packaged better for the race car.
The engine weight of the 10 cylinder engine is lower than the V12. The V8 engine, on the other hand, has a higher engine weight due to the structural reinforcement requirements. These come from the very high specific combustion forces per cylinder which result from the large bore size.
The answer.
 

TDIMeister

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Quote:
The engine weight of the 10 cylinder engine is lower than the V12. The V8 engine, on the other hand, has a higher engine weight due to the structural reinforcement requirements. These come from the very high specific combustion forces per cylinder which result from the large bore size.
jackbombay said:
The answer.
That answer was arrived upon somewhat self-fulfillingly. In the course of surveying the current state-of-the-art in Diesel engine technology, and researching the ACO rules to try to find the greatest technical advantage within the framework of the air-restrictor and other engine rules, Audi determined that it would be achieved using the largest displacement allowed by the rules.

This decision overuled other factors and kind-of drove them to the V12 layout. In other words it was sort of a preconceived conclusion. The combustion forces resulting from the large bore size was something I honestly didn't think of until Mr. Baretzky revealed it, but it makes perfect sense that 200 bar of peak pressure acting on a large piston area makes for very large forces.
However, this is not the only way to go. One could have decided on a somewhat smaller displacement (the air-restrictor size remains constant, but maximum boost pressure is increased). Then you could leverage benefits in smaller overall dimensions, reduced weight and lower friction by going to a smaller cylinder bore and count. I'm not saying this is the right- or only way of doing it, I'm just saying there's more than the one way Audi (and Peugeot) went.

To be sure, engine stresses would be greater and would require more engineering to deal with them. Mr. Baretzky did not shy away from admitting that Audi transferred series-production Diesel know-how in the development of the race engine, but Motorsport has usually done things in reverse order, bringing technological innovation at the race track and trickling-down to the OEM level. In Mr. Baretzky's defence, he stated that available development time was extremely short, and even a company like Audi is not without limits on budget.
 
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