Why does this car have so much speed - PeachParts Mercedes-Benz Forum

JackG · #1 10-31-2013, 12:42 PM

I just helped a friend find and buy his first SD.When we took it out
for a test drive I was floored.I have had 7 of these 5cyl diesels and
never had anything close to the power this one did. It is an 84 CA/FL
car and even with the ac on it was incredible. The car has just under
300k and all records.A very well maintained car I might add.Previous
owner said his mechanic also commented on the acceleration on this
car. Any ideas on where to look for "why" in has this power.Everything
appears to be stock.

JamesDean · #2 10-31-2013, 12:59 PM

ALDA shimmed? Wastegate adjusted? Different differential?

eatont9999 · #3 10-31-2013, 01:25 PM

The champagne colored 300SD that I most recently bought seems to have a lot more power than my grey 300SD. The transmission shifts a lot smoother and seems to hold the gears better. The champagne car has 241K miles on it, new injectors, IP timing is lined up with the witness marks and a recent valve adjustment. The grey car has the same work done but it has almost 400K miles, the IP timing has been messed with, the ALDA is turned up a little and the transmission has a broken bowden cable and likely needs a shift kit or worse.

pwjeep · #4 10-31-2013, 02:16 PM

A manual transmission will work wonders on the car. I get pushed back in my seat in each gear. No vacuum issues with leaks and no automatic transmission sapping engine power!

A modification like this is not easy. But it will put a S*** eatin' grin on your face when you drive it! If all else is well with the car, I think a manual transmission 85 300D turbo will rival a 16 valve W201.

Zacharias · #5 10-31-2013, 03:19 PM

Quote:

Originally Posted by JackG

I have had 7 of these 5cyl diesels and
never had anything close to the power this one did.

Is the 'tamper-proof' rubber plug still over the screw in the ALDA?

Most of these cars were delivered new with the boost set under factory spec, and factory spec is relatively conservative to begin with. This from a former Mercedes dealer mechanic (on a previous discussion list) who worked on these cars when they were being delivered new.

The 300d I have now is like you describe your friend's new acquisition. The person who sold it to me -- who was given it in an estate -- took it twice to the dealer to have them set up the boost to spec. The difference is nothing short of startling. I feel like I could pull a small strip mall off a standing start with this thing

.

JimFreeh · #6 10-31-2013, 03:41 PM

As mentioned, pump timing, cam timing, and IP timing.

Also, get the linkage set up just right and you'll be surprised at what a difference that makes.

I had a pristine 83 300D that the PO had tweaked all the above, and it was a (relative) rocket. Immediate power, no delay and very smooth. One of the nicest 5 cyl turbos I ever drove.

I did all this to our 87 300TD and it responded well to the efforts, was quite the tiger compared to when I bought it.

Be conservative on the ALDA adjustment, if the other stuff isn't spot on, all you get is lots of smoke...... neither of the above smoked excessively when floored.

Jim

pawoSD · #7 10-31-2013, 04:46 PM

Quote:

Originally Posted by pwjeep

A manual transmission will work wonders on the car. I get pushed back in my seat in each gear. No vacuum issues with leaks and no automatic transmission sapping engine power!

A modification like this is not easy. But it will put a S*** eatin' grin on your face when you drive it! If all else is well with the car, I think a manual transmission 85 300D turbo will rival a 16 valve W201.

You think the manual is fast until you drive one with a 2500rpm torque converter.

My 300SD has alda maxxed, bosio injector nozzles, 2.5" straight pipe, timing is spot on (newer chain), and I paired it to a 1985 300D transmission + 2500 stall torque converter and I still have the stock 3.07 diff. Standing start to 70mph acceleration is awesome! Its almost as quick to 30mph as my 420sel is!

eatont9999 · #8 10-31-2013, 04:52 PM

Quote:

Originally Posted by pawoSD

You think the manual is fast until you drive one with a 2500rpm torque converter.

My 300SD has alda maxxed, bosio injector nozzles, 2.5" straight pipe, timing is spot on (newer chain), and I paired it to a 1985 300D transmission + 2500 stall torque converter and I still have the stock 3.07 diff. Standing start to 70mph acceleration is awesome! Its almost as quick to 30mph as my 420sel is!

Did you buy a TC with a lower stall speed or is that standard in a 300D? I think a lower stall speed would be helpful for harnessing more power.

pawoSD · #9 10-31-2013, 05:04 PM

Quote:

Originally Posted by eatont9999

Did you buy a TC with a lower stall speed or is that standard in a 300D? I think a lower stall speed would be helpful for harnessing more power.

The '85s have a 2500rpm stall speed vs 1600rpm for the prior ones. It allows the engine to hit 2500rpm right off the line and thus you can maintain full engine torque the entire time when accelerating as it will never drop below 2500rpm even when shifting as long as your are on the throttle enough. Makes a huge difference. You get less power with the lower stall speed as it keeps the engine stuck at a lower rpm and output. It almost feels like a hydro drive on a tractor the way it shifts/works.

otto huber · #10 11-01-2013, 03:58 AM

I recently replaced the engine in my 300SD with a much stronger one that supposedly had well over 240K on it. My old engine had 217K on it, burned a quart of oil every 1700 miles and had a lot of blowby. My "new" engine has hardly any blowby and in 3000 miles so far, it hasn't even burned 1/2 a quart. I'm guessing that the peppy car you drove just had really good compression, as well as some of the tweaks mentioned on other posts. Linkage setting is also really important. The turbo on my engine kicks in before the pedal is even 1/4 of the way to the floor. I've driven a few 617s that required the pedal to be almost 3/4 to the floor before the turbo really kicked in.

It's really nice when you can drive one of these old diesels without too much pedal travel. My right foot used to get really tired while driving a 240D.

Brian Carlton · #11 11-01-2013, 08:42 AM

Quote:

Originally Posted by JackG

I just helped a friend find and buy his first SD.When we took it out
for a test drive I was floored.I have had 7 of these 5cyl diesels and
never had anything close to the power this one did. It is an 84 CA/FL
car and even with the ac on it was incredible. The car has just under
300k and all records.A very well maintained car I might add.Previous
owner said his mechanic also commented on the acceleration on this
car. Any ideas on where to look for "why" in has this power.Everything
appears to be stock.

What is the 0-60 time for this vehicle?

The situation could simply be that you're driving a vehicle that is maintained to original specs.............all prior vehicles were not.

vstech · #12 11-01-2013, 09:52 AM

+1

the 0-60 time in my 82 SD was around 9.5 seconds... and it'd routinely break loose the tires (I just cannot call it burning out) on corners and in wet weather...
I even started a thread on it, everyone calling it impossible and such...

turned out, my SD had a 3.46 diff in it, with the stock speedo... so yes it accelerated very nicely... had amazing off the line power, and drove very fast... but it was actually only doing 0-49ish mph in 9.5 seconds...

GregMN · #13 11-01-2013, 10:39 AM

I think the real question is: Why are all 7 of your cars so slow ?

eatont9999 · #14 11-01-2013, 01:00 PM

The compression in the (faster) champagne car is 420-450PSI.

The compression in the grey car is 320-350PSI.

My guess is that past owners did not change the oil as much in the grey car. Most oil change places charge a premium for Diesel vehicles. I have seen them advertise costs upwards of $100. It would be logical to assume the cost would be a reason the average owner would defer the maintenance.

pawoSD · #15 11-01-2013, 01:51 PM

I have never tested the compression on my engine but it has a lot of blowby (always has) and still starts fine in the extreme cold and will spin out in the rain if I am not careful.

I would peg my 0-60 within the 11-12 second range. I've never really officially tested it. I can confirm my 420sel is in the 8 second range

Helps when an engine and trans have 50k since a full rebuild.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode