Well if a turbo is more efficient, air temp decreases as the turbo is in its efficiency range as I understand. The lil T3 can't put out 14psi without being just about off its compressor map.

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I kind of follow you, Craig, but I think the discussion should distinguish airflow from pressure. If I have a small turbo rated at 500 cfm at 15 psi and replace it with a big turbo rated at 1000 cfm at 15 psi then I expect the temperature to be compable at 15 psi. But I expect the big turbo to blow cooler air at 500 cfm whatever the associated pressure might be. Is this what you're saying?

Sixto
... stay tuned

All I was trying to say was that the compressed air temperature (at a given pressure) will be about the same regardless of the size of the turbo. If I compress 500 cfm to 15 psi with a small turbo, the temperature will be the same as if I compress 1000 cfm to 15 psi with a bigger turbo. If I use a big turbo to compress only 500 cfm to 15 psi (by spinning it slower), the air temperature should still be about the same. There will be some difference due to the efficiency of the turbo, but if they are well designed and matched to the engine, the temperatures should be close.

I'm not saying it doesn't affect engine performance for other reasons, but I don't believe you will automatically decrease the air temperature by just using a bigger turbo.

That may be true, but I don't thing the limitation of the turbo is due to the increase in inlet air temperature, I think it just can't deliver enough air at that pressure to keep up with the engine. I agree, a bigger turbo can gut you more power (if you have enough fuel delivery) but I don't believe the difference in air temperature is the reason.

Where do I get an '82 300D with a 617NA? Is it a euro?

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You and Sixto are saying the same thing.

If you use a small Garrett turbo and you need 17 psi to get your power, you'll get a certain air temperature........which may be so high that it's inefficient in the total package.

If you use a slightly larger turbo, you need only 14 psi to get the same amount of power..........for the same cfm. The air is cooler and the efficiency is higher.

when I said 200hp, that was crank HP and it is the limit of what the IP can supply. 140hp is a realistic number that most anyone would get without a myna IP and a few K$ in internal and external modifications.

With the money it takes to get over the IP's inherent limits, swapping an OM606 would be far cheaper in the long run.

Even if you get that 140hp, any STOCK W124 300D could still walk all over it.

Just to be clear........you are not getting 200 hp from the stock pump without a $1500. workup with new elements.

The "stock" pump is probably good to 150 hp without any modifications..............just a guess, of course.

I think you're right, it's all about capacity.

How did the c-111 II (D) make 190hp with a om617?

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From what I've seen, bigger turbo, intercooler, and straight pipe exhaust.

I believe the II was basicly an SD engine at it's limits. The III went way beyond that. The only issue is we don't know if that 190hp is at the crank or the wheels.

BMW solved that problem on one of their diesels by using a small turbo for getting you off the line and a bigger turbo to keep you going at that speed.
I forgot which beamer diesel this was but it couldnt keep up with a M5 gasser even with the better torque numbers as shown on a episode of top gear.

EDIT: here you go, http://youtube.com/watch?v=__HpspsvRVg

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Doesn't VW have an engine with a supercharger for low rpm handing off to a turbo for high rpm? It's a piddling little Polo or Lupo engine too, IIRC.

Sixto
... stay tuned

From http://www.automotive.eaton.com/about/pressrel/091405.html
Eaton Supercharger-Turbocharger Increases Fuel Efficiency on 2006 Volkswagen Golf GT

September 14, 2005

Back to Table of Contents

Eaton has partnered with Volkswagen to help produce the only production-ready combination supercharger and turbocharger system in a passenger car today, allowing VW to deliver an engine on the 2006 Golf GT that improves fuel efficiency by 20 percent.

Unveiled at the International Motor Show (IAA) in Frankfurt and dubbed the “twincharger” by VW, the system combines a half-size, Eaton Roots-type supercharger with a single-stage turbocharger on VW’s new TSI 1.4-liter gasoline engine, which replaces the FSI engine previously available on the Golf in Europe. The system boosts the four-cylinder engine to 168 horsepower and 177 lb-feet of torque at an impressive fuel consumption average of 39.2 mpg.

“This system really is a best-of-both-worlds scenario: two technologies carefully crafted into a system that helps Volkswagen answer European consumers’ demands for performance and fuel efficiency in one cost-effective package,” said Jeff Romig, vice president and general manager, Eaton Air Induction and Cylinder Head Systems.

By combining the performance-enhancing elements of supercharging and turbocharging, a customer realizes the benefits of both technologies. The belt-driven supercharger compressor provides high torque at low engine speeds. The turbocharger kicks in to provide added performance at higher rpms. When the turbo system reaches ideal speeds, the supercharger is declutched and an electronically controlled bypass valve directs air to the turbocharger, which delivers high-end power without the “lag” generally associated with turbocharging.

The combination system allows an automaker the option to provide a smaller displacement gasoline engine while improving performance, and reducing fuel consumption and emissions. The system is an evolution of Eaton’s long history of innovation in engine air management, primarily in supercharging. In addition to boosting performance, automakers are also using superchargers to assist with meeting fuel economy and emission requirements in gasoline engines. In Europe, forecasts show that 70% of gasoline engines will be equal to or less than the 2.0-liter size. These lower displacements will require boosting to maintain performance, drivability, and emissions compliance.

The new system will be supplied from Eaton’s facility in Tczew, Poland with production expected to ramp up in September. The 2006 Golf GT goes on sale this fall and Volkswagen will use a variation of the TSI engine in future European models including the Touran compact MPV.

Unless I missed it and somebody already mentioned this; the limiting factor for either the OM617 ir OM60X engines is the 5.5mm plunger and barrel sets (elements) in the pumps, not the amount of air entering the engines (turbo). The stock turbo already produces an overabundance of air for the stock pump. You could theoretically alter the torque curve a bit lower by adding a variable vane turbo, in an effort to improve 0-60mph times, but your peak hp/torque figures aren't going to be altered by upgrading the turbo alone.

More fuel => More Powah

More fuel & More Air => Even More Powah