Do diesel engines need back pressure Why

Engine always with silencer, 21 Nov 2010 3:32 pm

Surnamemessage-Trecker Dieter-



After-work screwdriver
80 posts

Hello
I made the exhaust myself on another tractor but without a silencer. Now someone told me an engine must always have a silencer because of back pressure. Otherwise the engine would break down, is that correct ??? Greeting
  + Matthes +


Ferguson freak
2848 posts

Hello Dieter?
No, that's not right! A four-stroke engine doesn't need back pressure, unlike a two-stroke engine.
It needs a certain amount of back pressure, but not because otherwise the engine will break down, but because otherwise there may be considerable "flushing losses"
can come. increased fuel consumption without increased performance.

Greetings + Matthes +
 mhf1976


Ferguson freak
1823 posts

Hello dieter hello matthes,

In two-stroke engines, the back pressure is also necessary when idling in order to achieve enough back pressure for sufficient compression. Otherwise a two-stroke engine will only run smoothly with a very high idle.

Basically, the back pressure from the muffler "hampers" the higher turning of the engine from a certain speed. That's why there used to be exhaust flaps on cars that were installed in front of the silencer. But have been banned since 1948 (or so) because of the volume.

Problems with your tractor are only likely to arise with the traffic regulations because of the volume. This should not harm the engine.

Greeting,
MHF
 TobiasMF35


Professional
201 posts

Hello....

So without a silencer you always have a loss of power ..........

The best example are the so-called sport rear mufflers on cars or motorcycles ...

It has been proven that they often have a loss of power in contrast to the original dampers because they generate less back pressure ...

The 4-stroke gasoline engine as well as the 2-stroke gasoline engine and the diesel engine need a certain amount of recoil or counter pressure.

That's how we learned it in vocational school ...



greetings from Upper Franconia ..

Tobias

MF 35 built in 1963 SNM

Does not work - does not exist and everything that is mechanical will be broken
 + Matthes +


Ferguson freak
2848 posts

Hello, tobias,
yes, of course, but these are high-revving engines well beyond 6000 rpm. Gas change times are correspondingly short.
With the best will in the world, I can't imagine that you can feel that on a tractor diesel at 2000rpm.

Greetings + Matthes +
 TobiasMF35


Professional
201 posts

Hi Matthes.

I once had a 1.9 TDI and the exhaust was torn off after the diesel catalytic converter ...

what can I say ... you noticed that over the whole speed range ... and it only turned up to 5000 rpm.

And I've already had experience with my MF 35.
Then I tore off the exhaust pipe, directly under the oil pan and driving home with a full trailer was a catastrophe because you had noticed the loss of power ...
That's why I converted it to a chimney ...


Greetings from Upper Franconia

Tobias

MF 35 built in 1963 SNM

Does not work - does not exist and everything that is mechanical will be broken


Changed by TobiasMF35 on November 22, 2010 8:13 PM
 MF35X



Ferguson freak
1038 posts

Hello Matthes,

You are right. I've been driving my 35 without a silencer for five years. That means from the exhaust manifold a pipe to the rear of the hitch.
The sound is great. And there is no noticeable loss of performance. Endless power as we are used to at MF.
But I have to say that I always prefer the 65 with a silencer for longer distances. Don't want to go deaf.
 + Matthes +


Ferguson freak
2848 posts

Hello, tobias,
I can well imagine that with the TDI. But couldn't it be that currents, turbochargers and boost pressure control / electronics are responsible for this? Even at the risk of repeating myself: I can't imagine it with the tractor diesel The Perkins AD3.152 with 45 HP is built into my 135er. After a new "pot" from the vastness of the I-Net I still have
Bought an original at MF. Result = zero. There can't be much in terms of dynamic pressure. He yells his 45 horses in your ears, to my mind. I'm a bit older, but I have no disco hearing damage.
Could it be that you didn’t step on the gas so bravely because of the background noise?
Where should then with an electronics-less,
valve-controlled, direct-injection diesels suffer a loss of power when his
Garbage (exhaust gas) doesn't get rid of properly?
I'm looking forward to a professional discussion.

Kind regards + Matthes +
 schmieeed



Professional
196 posts

I can imagine that with the TDI, because the lambda value then no longer fits and the combustion does not run optimally, but such problems cannot arise without regulated combustion.
 mhf1976


Ferguson freak
1823 posts

Hello,

I can only agree with that. From my experience with the TDI engine from Audi, I can confirm that when it comes to measured values, they are really sensitive ... boost pressure, injection quantity, all possible temperatures ... the control unit quickly adjusts what is not should or throttles to emergency operation. There is plenty of material to read on the I-Net.
The motors cannot, however, be compared with the old mechanically controlled motors.
@ Tobias.
It's true what they told you in vocational school. With the back pressure and the intake negative pressure, the performance of the engine is regulated in some areas. But as a compromise always at the expense of other areas.
Racing cars turn very quickly and therefore need less back pressure. Otherwise at some point the pressure would be so high that the engine cannot turn any higher.
On the other hand, the "noise comfort" and the idling speed of the racing engine are very unfortunate ...

In the narrow speed range of the Standard or Perkins Diesel and with the huge flywheel, this should hardly be noticeable.

Why this had such a strong impact on your tractor is not clear to me at the moment.
What do you attribute that to?
Was the loss of power felt more at high or low speeds?

greeting,
MHF

 TobiasMF35


Professional
201 posts

Hi

@ Matthes

may well be that I no longer gave full throttle due to the higher noise level
I have a reaction, because I always drive by hearing and feeling ..

@ mhf
Slowly I think that it was only apparently an impression with less power on my MF 35, because I am always more careful and careful when something is out of the norm, or something is defective and then I drive soaaaaanz carefully into the home garage ... .

Let me teach you better, or am capable of learning and like to learn if I'm wrong ...


greetings from Upper Franconia
Tobias

MF 35 built in 1963 SNM

Does not work - does not exist and everything that is mechanical will be broken
 TobiasMF35


Professional
201 posts

So...

have the topic with me in our workshop today
Colleagues and the master discussed.

The end of the discussion was then that it does not matter with an old tractor whether pipe,
Damper or nothing comes after the manifold ..

so again something learned ..

with greetings from Upper Franconia

Tobias

MF 35 built in 1963 SNM

Does not work - does not exist and everything that is mechanical will be broken