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I know that these cars are built for cruising and longevity, not speed and performance, but I am just curious if anyone out there knows maybe how to squeeze a few more horsepower out of my 5-cylinder turbodiesel engine without breaking my engine or the bank.<br> <br> Also, if there's something in the way of suspension or wheels that I might be able to get to improve the old Benz's handling, that would also be appreciated. If not, I'm happy putting around, but it would be neat to give the old guy a little kick.<br> <br> Any responses would be much appreciated!<br> Happy Motoring!!<br> <br> -Jerrold<br> 1985 300D<br> 229,800 Miles<br> Dull paint<br> Less-than-perfect around the wheel wells<br> 14-second 0-60 time<br> Still a blast-and-a-half to drive!!
 

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I made two easy adjustments on my 81 300TD turbodiesel that turned the car into a rocket. The turbo performance is governed through a clear plastic tube (about 3 mm diameter) running from the back of the engine valve cover to a small cannister (looks like a 35 mm film cannister) near the brake booster on the firewall. This line can get plugged with oil at the end near the engine, which will reduce or eliminate the turbo boost. Remove the line (by removing the hollow bolt connecting it to the engine), clean it out and reattach it. The second adjustment is to the transmission - throttle linkage. On the turbodiesel, the speed at which the transmission shifts to higher gear is controlled by a cable linked to the throttle via a device sitting on top of the valve cover. In older cars, this cable can become stretched. Consequently, the car shifts at lower speeds to higher gears, robbing you of fast acceleration. The cable tension is adjusted with a white screw where the cable enters the linkage box. Simply turn the screw to remove slack from the cable when there is no throttle applied. You can make fine adjustments after a road test. These two changes made an incredible difference in performance for my car. If you haven't had the valves adjusted in the last 15 K miles, you should also have that done.<br>
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Hey, thanks for the tips, Bill!<br> <br> I'm going to check on those and see what I can do to squeeze a few more HP out of my old beast.<br> <br> I've been told that a 0-60 time of about 13 seconds isn't really that bad for an old 300D with 230,000 miles on it, but I still wonder if I could shave off a second or maybe even two by buying some aftermarket parts.<br> <br> I've been told that a K&N Air Filter might improve my speed a little. Any comments? Please reply.<br> <br> Thanks, and happy motoring!<br> <br> -Jerrold
 

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Jerrole,<br> <br> You don't need more horsepower, you just need to scrap the auto tranny and put in the 240D 4 speeed. You'll need the pedal assembly, shift knob mechanism, 300D flywheel and a driveshaft. If you decide you want to do this send me an email and we can talk on the phone. Believe me, I've done three of these conversions and am doing another one now and it'll be love at first shift. We're also working up an intercooler for the 300DT as well as a propane injection system. Resul should be about 200 HP. Check website www.dieselperformanceproducts.com .<br> Ben
 

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Ben,<br> in case you didn't get e-mail, I'm very intersted in the 300d auto to manual tranny swap. The propane injection system looks dangerous right now for my old girl (I don't have money to do major engine repairs for damage that might result) but I would be interested to know of details involving A) what a K&N air filter might do for my car, and B) what an intercooler would accomplish. I wonder how much I could expect to pay for a 300d manual flywheel, and where I might find one. I understand that 240d trannys usually go for about $1,000 in decent (but not new) shape. Tell me what you did for your last 3 projects, if you would be so kind. Also, I'd be interested to know if anyone else out there has done this tranny swap, and if they did anything differently.<br> <br> -Jerrold
 

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Discussion Starter #6
Jerrold,<br>
<br>
I can offer some e-opinions on some of this:<br>
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1- Propane injection systems seem to work fine on American truck diesels, but I don't know of anyone with a kit for any Mercedes. And you're right, they do have a significant risk factor.<br>
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2- K&N filters - forget it. Your car runs with an excess of air due to the turbo. Keep your stock filter clean, rotate it often, replace when dirty. A K&N will get you ZERO performance increase on a turbodiesel. Some folks claim the filtering isn't as good, either. Now on a gas engine, I think they do work... just not on turbodiesels.<br>
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3- Intercoolers - Again, save your money. I heard of a guy who went to great lengths, lots of time & $$$ to install one on a newer diesel (W140?), and actually LOST power. I wouldn't bother.<br>
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4- Manual tranny - Nice idea, but NOT cheap and NOT easy. Most folks get a European model (gray market) donor car with a non-turbo, and then swap a turbo engine in that chassis. It's easier than doing the tranny swap.<br>
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5- Sounds like you want performance. :) I'd say tweak what you have now. Make sure the turbo output is at top of spec (0.95 bar?), injectors are all perfect, brakes not dragging, wheel bearings adjusted properly, all rubber bushings in the car checked & replaced if necessary, tweak the ALDA perhaps, etc.<br>
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6- Better yet, save all that money and upgrade to a 1987 300D. These have the most power of any MB diesel except the 98-99 24-valve turbo OM606 engines. The '87 has 148hp and factory spec is 0-60 in 10.9 seconds. That's quick for an oil burner. :)<br>
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7- You should seriously consider signing up for the MBZ.org diesel email list. You will find a LOT of knowledgable folks over there... the URL is below. I recommend the digest version to keep the traffic manageable:
 

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I appreciate your post, Dave! I just have a few questions about what you said:<br> <br> One: What is this ALDA that you speak of tweaking, and how would I go about tweaking it?<br> <br> Two: How do I check to make sure my turbo output IS at .95 bar (top spec)? If it's not, how might I go about correcting it?<br> <br> Three: Does upgrading the 'breather tube' on the top of the air filter help? I heard a rumor that buying a newer plastic flat one will help a little over the old rubber hose-style one. Any truth to this?<br> <br> -Jerrold
 

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Hi Jerrold,<br> <br> 1- See my other post yesterday, at this URL. Plotos are at the other URL at the bottom of the page:<br> <br> http://forums.mbnz.org/forums/W123/vthread.asp?messid=641<br> <br> <br> 2- You need to get a pressre gauge that goes up to at least 15psi (~1 bar). Plumb it in the line to the ALDA with a 'T' fitting. Run the hose out the hood seam and through the driver's window. Go for a drive. At full load, in third gear, at ~4000rpm, you should see max boost. I *think* the spec for your car is the same as my 87's, which is 0.85-0.95 bar (roughly 13-14 psi.) As to how to adjust it, there's an article on the MBZ.org web site. Each turbo is different.<br> <br> 3- The top breather tube updat will only reduce oil leaks at the connection points. If yours isn't leaking, leave it alone. If it is, swapping to the new flat style should reduce or eliminate the leaks. There's no performance gain of any kind though...<br> <br> <br> Good luck! :)<br> <br> Dave M.
 

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Propane injection on Mercedes diesel is a bad idea because the aluminum head will get overheated and warped. It will start burning more oil, and you will wreck the rings.<br> <br> I have heard of propane injection for cold starts, I was going to try that, but I wouldnt do it for power. I would get a pyrometer and a turbo boost gage. VDO makes gages that you can get at napa. Once you know the factory exhaust temp and the boost, then dont go more than that if you try the propane because if its in mercedes tolerences it would seem reasonable, I might try it this summer when I ahve more time.<br> <br> I have a W123 Coupe 1983, and the fastest I have ever done 0-60 is 14 seconds at 1500 feet, I live at 7000 feet, so i do it in like 18 up here.<br> <br> The K& N filter barely helps at all. Intercooler would take about a grand to do.<br> <br> The 87 300D turbo is quite fast as said in previous posts, If you spool the turbo you can get it to about 11 seconds at sea level. (San Diego)<br> <br> Or just get a 99 E300 turbo diesel and dont worry about it. My friend has a honda accord with headers, etc. The 99 300 turbo tore up on him.<br> <br> Best of luck,<br> <br> Austin
 

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Discussion Starter #10
The flat hose upgrade is available various places. It does tidy up the engine bay a great deal! The MB part number is: 617 018 01 82. I've added it to both of my wagons and like it over the old three part hose.
 

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Jerrold,<br> 1. 240D trannys don't cost $1000.00. 2. there's a 240D not a mile from my house going for $125.00 with dead engine and good tranny, pedals, shift mechanism and linkage. Plus seats ddddash without cracks, etc.<br> 3. Tranny swap is a sanp as all auto components are modilar with the manual ones.<br> 4. 123 Heads are not aluminum but cast iron so warpping isn't likely.<br> 5. As I told you on another website, I've made three of these swaps and am awaiting two 5 speeds, overdrive trannys to put into two more 300DT.<br> 6. If you'll check out the spearco intercooler website, you'll find out several things about intercoolers, one of them is they lower the temperature in the engine by 120-150 F adding to durability, also increase power and mileage. Check it out.<br> Ben <br> <br>
 

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Re: Intercooling - anyone actually DONE this?

Ben,<br> <br> I understand intercooling normally makes a huge difference in power. However, I have only heard of one person who went through much trouble and expense to add one to his Mercdes turbo diesel (a W140, I think) and when he was all done, it made LESS power than stock!<br> <br> I'd LOVE to hear any and all stories about an Mercedes intercooler project that resulted in measurable power gains... anyone done this?<br> <br> <br> Regards,
 
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