Please go easy on me, I am a new comer to the diesel game, and still green when it comes to my Mercedes. I have had the 300SDL for almost two years(Sunday car till now but considering it as a daily driver), and the 300d 4 months(the current daily driver but have it for sale due to too many cars). I prefer the SDL due to it's size, luxury, look, and performance over the 300d but enjoy the 300d for what it is.

My questions are:
1) Can simple things be done to diesels like exhaust, intake, chip, injectors to improve mpg and/or performance like a gas car?

2) what are the things that are the most popular for performance and bang for the buck? & what brands or where to get them?

3)Totally subjective but, what do you recommend to get some noticable performance gains??

4) Can I do performance mods and not kill my mpg?

Thank you for your time!!
Hip

__________________

2006 Jetta TDI DSG 320k miles
1997 Ford F150 325k miles 4.2L V6 "Work Truck"
2008 Tundra 225k miles 5.7L
1982 240D.....sold
1984 300D...Totaled OUCH!
1985 300D Turbo 222k miles "Dos" sold to 79Mercy
1986 300SDL 98K miles "The Beater"....sold
1987 190E 2.3 16v Euro spec 115K miles....sold

Welcome.

First step: get everything up to spec. Valves adjusted, injectors cleaned and pop tested. Timing set to spec. Chain stretch checked (and corrected if necessary - by replacing it or installing an offset cam key). Clean the banjo bolt and line from the intake to the ALDA. New fuel filters. Maybe even run a Diesel Purge to make sure things are cleaned out.

Then, once all is up to factory spec, or as close as you can reasonably get it, you can install an EGT guage and boost guage. Once you have these two essential guages, you can start making mods to increase power.

First I'd install a boost pressure controller (if needed) to get the boost back up to 12 PSI (factory spec) or maybe a couple of PSI higher, but you don't want to push it up higher than about 14 PSI.

Then you can also adjust the ALDA and a few other IP settings to get a little more fuel to go along with the additional boost (do a search, there are lots of posts about adjustments you can do). Performance injectors are always another option, though not exactly a cheap one. You can also remove the muffler and/or resonator, though it will make it a little louder. Upsizing the exhaust from the turbo back can't hurt - up to about 3" (anything bigger would be a waste).

Most of these things should have negligable effect on mpg. The biggest determinant of your mpg is driving style and conditions. A heavy right foot and stop and go driving are the mpg killers with these cars.

If bottom end acceleration is what you're after, and you don't mind sacrificing a little mpg to get it, you can change the rear end to one with a higher numerical ratio (like a 3.67 out of a 240D). You probably have a 3.08, or possibly a 2.88 in there now.

Some people attempt to build a more free-flowing less restrictive intake, but the jury is out on that one. Some say the stock cold-air setup is about as good as it is going to get unless you compromise filtration. I've always thought that all the twists and turns of the stock intake setup can't be the least restrictive of all possibilities.

I've wanted to try a really BIG open-element cannister-style filter mounted behind the passenger headlight, and isolated from the underhood engine heat by a partition. Then connect it to the turbo inlet with a smooth gradual-curved intake pipe. Seems to me that would have to make for better intake flow. At least then the airstream wouldn't have to make two 180* turns between the air cleaner inlet and the turbo inlet. Again, the jury is still out on that one.

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Rcounts,
Thank you for the reply! EGT gauge, Is this exhaust gas temp? Where do I get these and where do I mount them?
I'm in the process of bring the 300SDL up to current maintenance specs. This use to be my Sunday car but think I'm gonna start driving it more.

A boost pressure controller? Where can i acquire that?

I also read somewhere that there was a guy putting a intercooler on his turbo. Is this a good idea? He said he was trying to increase his mpg. I love my big ole Hooptie and am still shocked it gets 30mpg compaired to my 300d's 23mpg. The SDL is the one I would like to keep so I'm leaning toward improvements on it.

__________________

2006 Jetta TDI DSG 320k miles
1997 Ford F150 325k miles 4.2L V6 "Work Truck"
2008 Tundra 225k miles 5.7L
1982 240D.....sold
1984 300D...Totaled OUCH!
1985 300D Turbo 222k miles "Dos" sold to 79Mercy
1986 300SDL 98K miles "The Beater"....sold
1987 190E 2.3 16v Euro spec 115K miles....sold

rcounts i had the exact same idea bout intake. i think that's what i'm gona do

This is an old post but maybe people still read it. There are some nice patient answers to this newbie. The SDL is fine. I had an 87 and it got up an ran. He mentions 23 mpg with his slow 300D. That can be brought to over 30 with the usual tips:checking IP timing, chain stretch, injector nozzles with balancing, air filter, turbo checks with all the associated fixes like banjo and alda, valve adjustment. My 85 300 D was fine but got 23-25. After putting in a new chain,reman turbo,bosio nozzles, IP timing and the other stuff I mentioned it has more poop and always gets 29-30 on the hiway. Best is 32.3 at a steady 55 on a long trip. Diesel will use fuel in proportion to the work required and 30 mpg with the sedan is doable.

This is an old post but maybe people still read it. There are some nice patient answers to this newbie. The SDL is fine. I had an 87 and it got up an ran. He mentions 23 mpg with his slow 300D. That can be brought to over 30 with the usual tips:checking IP timing, chain stretch, injector nozzles with balancing, air filter, turbo checks with all the associated fixes like banjo and alda, valve adjustment. My 85 300 D was fine but got 23-25. After putting in a new chain,reman turbo,bosio nozzles, IP timing and the other stuff I mentioned it has more poop and always gets 29-30 on the hiway. Best is 32.3 at a steady 55 on a long trip. Diesel will use fuel in proportion to the work required and 30 mpg with the sedan is doable.BTW my engine has 280K miles.

Very interesting pieces of advice that of yours.

Do you think these are usefull for a naturally aspirated diesel?

Is there ant way to feedback the guagues info to inyection?

Be easy on me too, please.

Tks.

OldBeaver

No it really does not apply other than the get it running as close to factory specs as possible part. If you have a NA diesel, adding more fuel without the more air to burn does nothing as far as more power. You must add more air AND more fuel to get more power.

In my experience an NA will benefit more from optimization of intake and exhaust than a turbo will - for the exact reason that Brian stated. On the turbo, it will compensate (mostly) for the inefficiencies. Without the turbo to compensate inefficiencies cost you more.

On my first diesel, an NA F250 pickup, I built a custom Y-pipe to a 3" exhaust system (replacing a 2.25" system and the crappiest flowing y-pipe design in automotive history), and installed a straight through muffler.

Then I added a dual intake ram-air setup. After installing an EGT guage I started dialing up the fuel a step at a time until the EGTs started getting out of hand - at which point I dialed it back a step.

I picked up over 15 ponies (calculated HP based on vehicle weight and timed 0-60mph runs vs. stock rating). Not a huge improvement, but almost a 10% increase in HP, and the cost was under $250 - including the EGT guage...

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

more fuel(myna pump), more boost to compensate for more fuel, and cool the boost.


to get any power out of these cars you need to spend a lot of money. The SDL has very good performance for its size and weight. I say get it up to spec and its good. Next time we have a gtg I will let you drive my SDL since hatty made sure it was in tip top shape. I am keeping up with it as well.

Well, unless you're talking about a Cali car with a trap-ox, there isn't a catalytic converter (or anything like it) to remove. There is a resonator ahead of the muffler. Numerous people have reported noticeable performance increases by removing both the resonator AND the muffler. I personally have not done this yet - have you 82-300TD? I've heard others say the stock muffler is a straight-through design, but I've heard just as many people say that it isn't, so I don't think you can say that all of them are.

At any rate. a diesel will perform at its max potential with NO exhaust installed whatsoever. Therefore the closer you can get to that (while still remaining civilized about it) the better. Therefore the most wide-open exhaust you can install will help with performance. I intend to upsize mine to 3" pipe all the way from the turbo flange back. It may not yield a huge performance increase, but it sure can't hurt.

I'm not talking about restriction from the filter. I'm talking about the air having to make a 90* turn (downwards) into the opening in the bottom of the air cleaner, followed by another immediate 90* turn (towards the front of the car) coming out of the bottom of the air cleaner, followed by a 180* turn through the U-tube (from moving towards the front of the car to moving towards the back of the car) before entering the turbo inlet. Air has mass, and twisting and turning through that labarynth to get from the inlet pipe above the headlight to the turbo inlet can't result in the best possible flow.

I'm also NOT talking about a small cone filter exposed to hot underhood air. Read what I said again. I am talking about a LARGE cannister filter - like around 8" in diameter and 10" long. I am also talking about installing a partition between the inner wheel well arch and the radiator support - to effectively isolate the entire area behind the headlight all the way from the radiator support to the wheel well. This would form a large cold-air "box" that is isolated from the rest of the engine compartment. The cannister filter would be installed inside this box effectively making it a large cold-air intake chamber.

The only opening through the partition would be a hole where the intake tube between the cannister filter and the turbo inlet passes through the partition panel.

With the size and style of filter I'm considering, the filter area will be in the neighborhood of 250 square inches - not even counting the pleats in the filter media (8 x pi x 10). This is pretty much exactly the same area as the stock filter (13 x pi x 6), but with an intake path that is a single smooth, gradual 90* curve - instead of all the sharp twists and turns of the stock intake path.

And no, I don't have a $50k flow bench to test it on, but it is logical that the straighter intake path would be a benefit, all other things being equal.

Seems like it would be worth trying to me.

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

I'm not grasping your benefits from a less restrictive intake, unless you've got insufficient air at maximum boost levels.

If you're at 15 psi and you see black smoke............now you've got an argument for a less restrictive intake.

But, I'd make a wager that you're not at 15 psi with excessive fuel.........yet.

You're an engineer and you aren't "grasping" one of the fundamentals of fluid dynamics?

Any restriction on the turbo inlet produces a partial vacuum. The turbo can easily compensate for this, by increasing the pressure ratio and RPM. This can only be done by increasing the work done by the exhaust, which increases exhaust backpressure and increases engine pumping losses.

Just because you don't see black smoke doesn't mean your engine is running at maximum efficiency.

Agreed.

However, the question is the amount of the loss and the end result to the engine. If the intake causes a partial vacuum of........say........1" Hg........is it worth the effort to completely redesign the intake to eliminate it? The turbo compensates for the loss of air with slightly more boost and a bit of additional temperature as a result.

If you're looking for maximum performance, sure..........knock yourself out........but, you haven't done any intake modifications.........in favor of a different turbo with significant boost at lower rpm's. If it was that beneficial, you would have already done it.

Nobody is saying you'll get significant hp out of it, we are simply saying that there is a benefit.

When a person is looking to maximize efficiency or squeeze out every last 1/2hp, small details like filter ducting are noteworthy items to look at.