Any improvements with larger exhaust on 617 diesels? - Page 2 - PeachParts Mercedes-Benz Forum

190D22 · #16 03-08-2003, 12:25 PM

I dont know, my car was pretty loud when I had a hole in the exhaust. The front pipe broke before the first muffler. The car sounded like an old trashy chevy or something... it was bad! Even at idle it was loud. I found that 1000-2000 rpm range was the loudest, at least the most resonant!

rwthomas1 · #17 03-08-2003, 08:15 PM

Larry,
Don't worry about me taking you as being combative. I don't. I greatly enjoy these discussions as I find I do learn a lot and maybe they educate others as well? I am man enough to admit when I am wrong and I am always interested in hearing someone else ideas and opinions on a topic like this because it will either reinforce what I already know or it will help to educate me and change my mind. That said yes the truck exhaust was EXTREMELY poorly designed. They were squashed at the factory during the engine install because they didn't clear obstructions. Ford had the same issues and benefits from bigger/better pipes as well. Dodge/Cummins does a much better job, their exhaust flows very well and only the totally power-hungry mess with it. Additionally there was an "air restrictor snorkle" in the fender on the intake system for my truck. GM had a 6.5liter turbodiesel breathing through two 1 1/2" holes!! This was done to silence intake noise to keep the Federales happy. Admittedly my truck started out as a poorly designed system. Much of that has changed with modifications and aftermarket parts. Regarding the technical aspects of a diesel only taking in air on the intake stroke I am well aware of that. Restricting the intake or exhaust on a turbodiesel will affect power output. If the engine has to work to pull in air its a pumping loss. I realize the turbo seems to negate this but not really. The turbo will compensate to some degree but the backpressure between the turbo and the engine will increase as the turbo works harder to overcome the restriction. Same thing happens when you plug up the exhaust. Power goes away as the pressure post-turbo starts to approach pre-turbo levels not to mention the heat loading that this will cause. I am not saying that the MB has any of these problems in its stock form. I was merely suggesting that it might be interesting to see how much backpressure a MB exhaust system really creates. I have similar views on the intake tract. A vacuum gauge plumbed a few inches in front of the turbo would be a great indicator of how efficient the intake system is. One would have to admit the intake tract of the turbo motor is fairly torturous.... With that nice tight 180* turn right out of the turbo? All I am suggesting is that it may be worth taking a look at. Curiousity alone makes it worthwhile. RT

#18 03-09-2003, 12:45 PM

I owned a 300 series Case diesel tractor that the muffler pulled straight up and off, no connectors. It was the only way to open the "hood". We had a barn that when we were filling with tobacco this tractor could not drive through unless you pulled the muffler off. With no muffler and even under a pretty good load it was not much louder than when it was on. A gas engine with no muffler you would have heard into the next county.

BoostnBenz · #19 03-09-2003, 01:50 PM

It seems many turbo vehicles have that silencer on it, on my Talon it was designed to silence the noise the turbo makes while sucking the air in. I've heard quite a few people say something like, something is wrong with your motor, why is it making that sound?!? Anyway, kind of ridiculous to lose power over something like that. What kind of mileage does your C2500 get btw?

I also would like to see how much vacuum there is on the intake of our cars. But I don't care for the idea of drilling a hole in my intake like that just to see. If I can think of a way to measure it without drilling or permantely changing something I will surely do it. If you have your 300D just gently idling, stick your hand by the snorkel and feel the suction, just imagine how much it is sucking at cruise speed or redline!! I think if there is a restriction in the intake it would be where the snorkel is, not really the bend. The bend is made of 4" rubber, while it does get quite oval, the intake pipe is what 2"? Then where the snorkel pulls the air in, it has even less cross sectional area than that. Maybe I'll look into this next time I'm under the hood of my 83.

Jeff M.

190D22 · #20 03-09-2003, 02:22 PM

People are stupid. Turbos sound so disctinct, if you don't know what it is, you look dumb when you ask! Same with the diesels, people ask me whats wrong with my call all the time, mostly of the opposite sex. I tell them nothing is wrong with it, and that my car is a very healthy sounding diesel. I love the sound of a turbo, thats the sound of power! I don't know why you would want to silence that... personally.

wagonboy · #21 03-09-2003, 02:27 PM

Same here, love the turbo sound, I would like to have the bov sound on my diesel, but I heard it is useless on an automatic.

BoostnBenz · #22 03-09-2003, 03:16 PM

They aren't very important on autos for sure, they still serve some purpose though. Letting off the gas to shift on manuals puts them to good use, but the rare time you boost up and instantly let off the gas on a auto.... However a BOV on our diesels would be 100% useless.

Yea turbos do sound cool, I can't really hear the turbos in my 300s though. Then again I don't really drive WOT very much either. No doubt they are boosting frequently, but I can't hear them over the motor.

Jeff M.

rwthomas1 · #23 03-09-2003, 11:33 PM

BoostnBenz,
The C2500 gets 19.7mpg at 75mph unloaded. Towing 6-8K, averaging 65mph 11-13mpg but I am usually pulling something with HUGE wind drag. Something heavy but sleek like a V-nosed enclosed trailer likely would get a couple of mpg better.

BOV's or blow-off valves don't work on diesels. A blow-off valve dumps boost when a throttle valve is suddenly closed. This keeps the turbo from stalling/heat loading, it stays spooled up so that boost is available quickly when the throttle is quickly opened again. Since diesels don't have a "throttle" it would simply have no function at all. RT

Fredmburgess · #24 03-13-2003, 12:50 AM

I think the point is that you have to do things in concert. My buddy's Dodge Ram/Cummins B6 has turned into a fire breathing monster because of a combination of upgrades.

1. Larger diameter exhaust pipes all the way to the back.
2. New, larger, free flow airbox.
3. New control chip to increase fuel input.
4. New boost controller to allow increased boost.

I haven't done the airbox/pipes on my 300D t, but I did increase the boost and fuel delivery with great results.

There's always more until the big bang!

william rogers · #25 03-13-2003, 01:14 AM

I got to agree with Larry I read a very interesting long article about a company that soups up semi engines and nearly doubles hp on some of them. They make massive complicated changes in the fuel dilevery system plus larger turbos bigger exaust and a long list of other changes.I will try and refind the article and post the URL . I love the idea of a jake brake on my SD and 240 would sure bring a smile from the log truck drivers out here.......
William Rogers........