300SDL Accelerator - Page 2 - PeachParts Mercedes-Benz Forum

PaulH · #1 05-12-2003, 11:35 PM

I bought the car new in 1987. But, it stayed in the garage, used only on trips , because I always had a company car. Last spring I retired from corp. and just got a local job. I was going to get another (smaller) car. However, cars don't get better with age like wine, so I decided to use it. So, now I have a big car for safety and it gets 25 mpg around town. Also, I have gotten use to the stiff fuel pedal. Let me know if you find a "weaker" spring.

PaulH · #2 05-12-2003, 11:46 PM

I have not tried an ALDA adjustment because I think that the car is over all damned fast , especially for a diesel. If I mash the pedal, I'll get some black smoke, anyway. And I don't want to screw up my fuel economy.

rivermasternc · #3 05-13-2003, 09:11 AM

PaulH:

Greetings Annapolis! I trust your fair city is doing well. It has been a couple of years since I've been there. Please do me a favor. Go pick some crabs at Jimmy Cantler's for me.

Regarding ALDA adjustment. The ALDA will not increase the overall speed of the car. Loosening the resistance in the spring simply allows the pump to supply more fuel earlier in the boost curve. If done properly, there should really only be a noticeabe change in the dirveability of the car in the engine speed ranges before the turbo really gets winding.

The best test to see if the ADLA has been backed off too far is to run the car in 3rd gear at 4,000 rpm looking for smoke. If no smoke, you are OK. Incremental adjustments in the 90 or 180 degree range are a good way to approach this.

Again, all the linkages and alda system components need to be in good working order FIRST.

Happy motoring!

-Scott

Tom Sweeney · #4 05-13-2003, 10:07 AM

P E H
I agree with your comparisons of the SD and SDL accelerations. I do not detect any significant difference in the amount of pressure needed to depress the accelerator, but there is a definite difference in the response of both at similar positions. My SD is quicker on initial acceleration where the SDL after 2500 rpm really starts to pull. I drive both of them regularly. I just accepted it as the way they were designed, perhaps they have different rear gear ratios, the SD gets about 5% better fuel economy.
Tom
82 SD
86SDL

bhatt · #5 05-13-2003, 11:34 AM

Now that I've found some people discussing differences between SD and SDL's...

I had an '83 SD that I could get to chirp the rear tires when it shifted into 2nd gear. My SDL doesn't do this.. I've never been able to make the rear wheels spin at all since I've bought it. The SDL has more HP compared to the SD and doesn't weigh a lot more..

I've checked the line going into the ALDA and it's clear. Should I be able to chirp the rear tires in my SDL or do I have a performance deficiency somewhere? The car is really moves over 2500-3000 RPM or so, but is a total dog below that when compared to an SD.. very little low end power compared to an SD.

Neal

PaulH · #6 05-13-2003, 02:30 PM

I'll wait till it's warmer to go to Cantler's- probably by boat!

gsxr · #7 05-13-2003, 04:09 PM

Rivermaster is right. PEH and Lance both have what sound like classic cases of low fuel delivery off idle. Check all the stuff he mentioned first, before you touch the ALDA. Make sure your EGR and ARV are both killed. Then mess with the ALDA. Note that on a 603 engine it's a real pain to access, I leave the intake manifold in place and remove the ALDA from the IP (it unscrews easily). Some engine may need to have the rear 3 metal injection lines removed for clearance, which is a pain. If there's no improvement in power, turn the ALDA back to where it was or you will lose MPG.

My one 603 engine absolutely leaps off the line with the slightest press on the pedal. I mean to the point that I have to be careful pulling out on wet roads, even with 205/55/16 tires. It just lights them up. My other 603 is softer off idle but not weak at all, I plan to fiddle with the ALDA on that one too & see if I can make it as snappy as the first car is. Both get 30-32mpg and run excellent otherwise.

But anyway you should not have to suffer through low power off idle. That is NOT a "normal" diesel trait, as most people will tell you. Problem is, you don't know what normal is until you drive a "good" car as a reference point!

One tip is that you should not feel the boost "kick in". If you do, that's not right. The power should come on strong off idle, BEFORE the boost starts, and then seamlessly start pulling harder as the boost rises. Cars that are dogs until 2500-2800 and then "take off" need more fuel off idle. The proper fix is an IP calibration but the easy fix is to play with the ALDA. And finally the 603 should be MUCH more powerful at ANY RPM range than a 617 of any year. If not, something is wrong!

Good luck,

#8 05-14-2003, 06:42 PM

Very interesting thread.

P.E.H. , I've noticed a rather slow acceleration response in my SDL too and have chalked it up to a heavy vehicle, low hp, and highway gearing. My 0-60 is decent (about 12 secs) but I almost always give it 90% throttle off the line (once it's warmed up) and experience no grey smoke unless I go 100% throttle. The only way I can "light-up" the tires is if I'm going around a sharp turn and floor it - when it's wet!

Sounds like I have a few items to check too.

gsxr · #9 05-14-2003, 06:54 PM

If your 0-60 time is 12 seconds, you have one VERY quick SDL. That's equal or faster to factory spec. Make sure you time it with a stopwatch, and use a GPS to confirm your speedo is accurate. Either way it sounds like you have a "good one" there...

TX76513 · #10 05-14-2003, 06:58 PM

Problem is, you don't know what normal is until you drive a "good" car as a reference point!
--------------------------
Excellent statement and holds truth for a lot of things. To me my SDL is doggy off the line (not like the 5 cyl 300d) tech says ok - To me the SDL shifts rougher than 300d Tech says ok. Guess I need to drive a SDL that's "tuned in" so that I can benchmark where mine is.