Hello all. I recently heard that flipping over the intake cover (on an intake system like my 84 300TD) increases airflow/power a little. Will this work? Thanks

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1984 300TD Turbo 156Kmi
"He who seeks knowledge begins with humbleness" - Buju Banton

The idea is to reduce the air restriction to the air intake without losing the function of the air cleaner/filter. For your car, I wouldn't do it at all. You need to keep your air cleaner closed up to keep the filter clean as possible, and because it isn't uncommon to get some engine oil into the air cleaner, which will make a big mess if it's open under your hood. Even if I wanted to, I couldn't do this anyway, because there's a engine venting tube that runs into the top of mine from the valve cover. If you want to reduce the "restricted" air flow, buy a K&N air filter and replace your old one with that. www.knfilters.com/default.htm

And just so I understand, do you have a wagon, or a sedan? Many people in the past have said that they have a TD, which is a diesel station wagon, when they were trying to say they have a Turbo Diesel (TD), which is a 300D

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Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

This is an old trick for gas engines that will increase flow slightly and thus increase power slightly, probably unnoticeably.

This will have virtually no effect on a diesel however.

A gas engines power is determined by flow. Remember that the fuel and air combine somewhere before the base of the intake valve. The engine is a pump, the more fuel/air you pump in, the more power you pump out. In a diesel the power is determined by the amount of FUEL that you inject into the cylinder. The turbo is there to pump more air in the cylinders in order to provide the additional combustion chamber cooling necessary when injecting more fuel.

As mentioned by longston, this trick makes it more difficult to keep the air filter clean. If it were a gas engine and you realized a gain from it, maybe it would be worth 2,000 mile filter changes, in the diesel, you would gain virtually nothing for this added expense and hassle.

Good luck,

Thanks for the clarification and info. Just FYI, I have a 300 TDTurbo wagon. I'll buy the K&N I guess.
I didn't know that the turbo on diesels was just to cool the combustion chamber air. I guess that's why they don't boost as much as a gas engine turbo. Learn something new everyday.

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1984 300TD Turbo 156Kmi
"He who seeks knowledge begins with humbleness" - Buju Banton

Can you post your results after trying a K & N? I have a 300TD Wagon (85) and its slower than a dog compared to my 300D-T. Will switch over to K & N filter if you have any luck. Thanks

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

Diesel Don,

I do not think changing the filter type can help your 85 300TD. If it is not a California model, something is not setting up right, such as, ALDA control, fuel timing, fuel filter, air filter, valve adjustment, wastegate, air filter oil return, etc.

David

Diesel don, I'll post up results when I get the K&N. Actually went today and picked one up, but got the wrong size (duh). When I return this one I'll let you know. Mine is also very slow. I don't know how much difference the K&N will make though given what LarryBible said about power being fuel driven and not so much air/fuel like a gas engine.

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1984 300TD Turbo 156Kmi
"He who seeks knowledge begins with humbleness" - Buju Banton

I will try again.

In a gas engine increasing flow increases horsepower.

In a diesel engine, increasing intake air flow has no effect on horsepower. Increasing fuel into the cylinder is how power is increased. You can only increase fuel flow into the cylinder to a certain point before damage can be done, unless you increase air flow to go with it.

All a K&N fliter will do is provide you with a filter that you don't have to replace. Don't expect a power gain of any kind from this modification on a diesel engine.

Have a great day,

The point Larry is making is that the gas car regulates power based on running a fuel air mixture that is controlled so that the spark ignites the mixture and the result is a controlled temperature with controlled emissions and controlled power. When you demand more power, more air and more fuel, in the prescribed mixture, are put into the combustion chamber and the mixture is ignited by the spark.

In a Diesel engine there is no spark, and the fuel/air mixture is ignited by the heat of compression. For this temperature to be predictable and high enough to ignite the Diesel fuel droplets that are injected into the combustion chamber at the instant of injection, the pressure in the cylinder has to be about the same throughout the rpm range. If there was a throttle on the air intake, this would not be the case. The initial conditions for each compression stroke would depend on the throttle position.

So, to ensure the conditions exist that are needed for combustion in a Diesel, there can not be a significant vacuum in the intake manifold, and whatever there is (and there is a pressure drop across the air filter and through the intake manifold, which varies with flow rate or engine rpm, but it is much less than across a throttling device and is accounted for in the engine/induction system integration) can not vary over the throttle position range. Power is controlled by the quantity of fuel injected, while the charge of air in the combustion chamber stays nearly the same.

A lower restriction intake system will make the consistency of the initial conditions for the compression stroke stay the same over a wider rpm range, but it is not likely this will produce a noticeable effect in a new car running as it was designed. And if the car's performance has degraded over time, unless there is a family of rodents or something that is living in the intake path, changing the intake configuration with a new filter is not likely to fix the problem as the car worked as designed with the existing system intact when it left the factory. If there is a family of rodents, or a bird's nest in the intake, removing it and leaving the existing intake configuration will do just fine restoring performance. Don't laugh about the birds and other wildlife taking refuge in the car's intake system if it has been sitting for a number of months or years. I have had this problem before and read of others who actually had acorn shells ingested into their engines after letting the car sit for a while.

So, I agree with Larry, if your car is suffering from degraded performance, a new air filter configuration will likely not solve the problem. By the way, my old 1975 240D had an oil bath air cleaner and I welcomed the change to filter elements. Cleaning that old thing was a significant chore, and it occupied a much larger volume under the hood.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

True pearls of wisdom from Jim and Larry, but if you want to speed up your turbocharged diesel, I believe there are some important air/fuel adjustments that can yield an appreciable power increase. How do I know? I did them, and while driving with the A/C on, it performs the way it used to with the A/C off. In other words, now with the A/C off, it performs ALMOST like a gasoline-powered car.

I adjusted the wastegate (a procedure not for the faint of heart), and tweaked the ALDA for fuel enrichment. Mind you, I monitored the boost levels to make sure I wasn't going to blow my engine (the switchover valve is indespensible), but I can now drive this car with a lot more confidence from a standing start. When I first got it, it couldn't get out of its own way...

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Matt
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1995 E300 Diesel (Die Blau Frau)

Than what you expected, but truly accurate, never-the-less! That was my original point, albeit not stated, that a diesel will not benefit from increased air flow as much as by accurate fuel metering.

Have the valves adjusted, get the rack and turbo adjustments done correctly, and see what your diesel can really do in the way of performance. Mine flat honks!

And study the differences between spark ignited, and compression igniton systems in internal combustion engines, so you will understand the principles involved...

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Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

Turbo to cool the cylinders???? Come on Larry. The turbo is there to push more air into the cylinders so there is more oxygen in the cylinders so more fuel can be burned to give more power. A turbo effectively increases the compression pressure (compression ratio always stays the same) which leads to more heat not cooling. That's one reason why the turbo Diesels have oil cooled pistons. ~~~~~~~~~~~PEH~~~~~~~~~~~~

P.E.,

We are saying a similar thing. The truckers used to be known for having their injection systems "turned up" to get more power. This was to the detriment of engine life and was usually done by a driver that did not own the truck. If you want to get more power without killing the engine, you have to be drawing more air into the cylinders to prevent excessive combustion chamber temperature.

You can increase power by increasing the amount of fuel injected WITHOUT adding additional air. The additional air from the turbo, or whatever, allows this added fuel to be burned at an acceptable air fuel ratio.

In a gasoline engine an excessive amount of air (lean condition) causes excessive combustion chamber temperature which burns valves, pistons, etc. Diesels operate in an opposite manner.

In your thinking about more air from turbo and more fuel from pump, you are not taking into consideration the fact that with the added air AND fuel you are adding more usable energy into the combustion chamber. In this correct scenario, this energy is dissipated as power rather than being wasted as heat. In the case of adding too much fuel with not enough air, you are making a condition that adds some power but a higher percentage of the energy is dissipated as heat.

In other words your statement that the turbo and additional fuel add more heat to the combustion chamber is not exactly correct. You are indeed adding more ENERGY to the chamber, but this energy is dissipated in the form of power, rather than wasted as heat.

Great discussion,

Larry,you and PEH should be on debate teams.I've been fixin on these things for nye on 30 years and have never given much thought to the purpose of the turbo.I'm noy an engineer;I just fix what's broke.Your point is well taken about the extra heat with too much fuel,but PEH has a strong point about the oil squirters not to mention the nitrated crank.As I'm sure you know a naturally aspirated engine squeezes air molecules into a tight space until friction brings the temp to about 900*F.Then fuel is injected.It seems a turbo would introduce more molecules and produce more friction and more heat,but then as you say,you also get more energy.It would be nice to have an engineer to explain the theory in layman's terms.Also as you say;great discussion|

Peter,
Auto Zentral Ltd.

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Auto Zentral Ltd.

The oil squirters and hardened crank are necessary because of increased horsepower, not EXCESSIVE combustion chamber heat. If the extra energy(combustible fuel/air) is added to the cylinder and combusted properly, the combustion process makes more power.

If the fuel and air are added in equal proportions, then the ratio of usable energy versus heat remains the same. So, yes this means more heat. If you did not add the air to the cylinder with the added fuel, this ratio will be wrong and EXCESSIVE heat will be the result.

I have spoken with a Masters degreed physicist that I work with about this and he says that I am correct.

Have a great day,