Improving Acceleration...
 

I'm trying to get more performance out of my 83 300sd. Notice I said performance and not horsepower. Increasing horsepower is great, but not at a loss of low end grunt. My main focus is Improving acceleration. I am happy with the performance above 40 mph, but getting to 40mph usually a time consuming task.

The biggest problem is my tranny starts in 2nd gear. Is there a cheap and easy way to get the tranny to start in 1st? ( without me shifting myself. ) I have heard about the valve body swap, but finding that 1st gear start valve body is like looking for a needle in a haystack.

Eliminating Lag , Quicker Spool is what I was mainly thinking. I was thinking a boost controller could help with spool up, what are your thoughts on this? and then a newer, modern turbo, that spools up much quicker, not necessarily bigger, just newer technology. I have been looking into the Holset turbos, the smaller ones, no bigger than the hx30.

Please disucuss..

I rebuilt a turbo(Garrett) with a .36AR turbine housing(tighter scroll- .48 AR is standard) that the rebuilder had sitting on the shelf in his spares room. The turbo spools about 200 rpm quicker. Another option would be ball bearings, if you can retrofit an older turbo with ball bearings. Boost controller? Just set the wastegate to crack at 12psi- I don't see how an external boost controller would help, but who knows. A really good rebuild would help spool very slightly I would think.
Have you tried the ALDA adjustment?

JATO? SPR?
best way to improve acceleration is to remove weight. higher gears help.
my 82 starts in first. perhaps looking for an 82 SD trans would help?
John

Are you hitting max fuel stop on the linkage? Have you checked IP timing? Have you pop tested and balanced the injectors? Try all these things first before trying anything else.

A properly running SD doesn't need anymore performance below the onset of boost. It should smartly accelerate at 2000 rpm and easily keep up with most traffic........unless they are racing you. If it doesn't do this, then the ALDA needs to be adjusted for more fuel..........the IP timing needs to be checked...........and the cam timing needs to be verified.

With regard to the second gear start, the SD will do this if the Bowden cable is too slack. Pop the socket off the ball and adjust the cable so that it just snaps onto the ball without any cable slack........in fact.........a bit of tension on the cable is preferable and will slightly delay the shifts.........resulting in the sense of additional performance by the driver.

ALDA last......

I think some of you guys might have misunderstood me. The 300sd is running very well. I had adjusted the ALDA, to the point where I get some black smoke out the tail pipe when the pedal is floored. Almost all the way, just a few turns back. All the vacuum lines had been cleaned as well as the banjo bolt. I have adjusted the bowden cable, the tranny shifts properly, but like I said, it starts in second gear, unless I push the kick down switch and then its only for a very little bit. If I manually shift the tranny, the acceleration is actually quite well. The 300sd drives just as well as other 300sd's I have driven, if not better than some.
What I want to improve is the off boost characteristics, especially since the tranny likes to shift early and the engine revs low. It takes some amount of time for the turbo to spool.
A boost controller could help spool the turbo quicker since it blocks boost pressure to the wastegate (actuator ) until a set point. lets say that we set it to 12psi, without the boost controller, the wastegate actuator will receive all boost pressure up to 12psi. What happens then is the wastegate slowly starts to open , thus reacing full boost later. but it all depends on the set up. Thats why I asked, maybe some people tried it before. Is it worth it? Thats also why I suggested a modern turbo that spools quicker.
And also any way to get the tranny to start in First gear?, Maybe even raise all the shift points?

VNT turbo (click the link in my signature), it will give your engine all the boost it can handle well below 2000rpm. When the stock turbo would just be starting to kick in, this thing is already at 13psi.

Asked and answered.......post #5.

Yes, I read that. and I replied that I have adjusted the bowden cable, it's tight. Tranny still starts in 2nd gear and shifts pretty early , for me, probably shifts late when compared to spec or other OM617s

If the tranny starts in second gear and shifts late........the Bowden cable has too much slack...........!!!

WARNING:this is just what ive done to my car, and only a recomendation for yourself!
cone air filter-less turbo lag, noticable
added boost-i increased the boost, deffinatley noticeable
ALDA tweak-noticeable
clean filters-always help
bowden cable- get your baby to shift the way u want it to

Witht these tweaks, i can now smoke tires, no lie. Its no rocket, but its definatley quicker.
The eversooften ITALIAN TUNEUP helps to...
-good luck

A boost controller only helps the end of boost, not the beginning.

Have you checked to see that your wastegate closes all the way and is not leaking a little before you get to full boost.

It helps throughout the range by blocking air to the wastegate until max boost. Without that air, the wastegate will stay closed longer than it otherwise would at the same boost pressures.

722.303 trans (yours!) is supposed to start in FIRST gear. There is no valve body "kit" for it. Adjust the trans; Bowden, vacuum, modulator. There's lots of info in the archives.

2nd gear start is only a gasser thing. Our diesels won't get across an intersection before the light changes without first gear start.

Resurrecting an old thread here. I wanted to say that I was wrong, the Tranny does in fact start in FIRST . I just thought that was second because it didn't feel like first gear and felt, well , more like second. Not enough take off at all.

So once again, how can we improve acceleration? Over the last few months I have worked on the car making sure everything is "tuned up" and it is, it's a very well running machine, but I just wish I had a little more "oomph" like another gear or something. The other thing is on the highway I feel like it revs high. So I think I want another tranny. a 5 speed or 6 speed. doesn't have to be a manual , could be an automatic. I just want a little more performance. Maybe a quicker spooling turbo.

I'm just trying to steer up some thoughts here.

You've got 123 hp at 4400 rpm. During normal operation, running 2000 to 3000 rpm, you've got between 45 hp and 95 hp. You're not ever going to get to a point where it can keep up with the 200 hp gassers. You can spend a fortune of money and possibly get another 25 hp. Then, you'll have a whopping 150 hp at 4400 rpm.

Still cannot beat a four cylinder Honda Accord.

If the performance isn't satisfactory after you have properly set cam timing, IP timing, and boost...........sell the vehicle and buy one with more horsepower.

BTW, the reason that it revs somewhat high on the highway is so that the engine provides you with sufficient horsepower for passing and for climbing hills.

Brian,
I am trying to conjure up some ideas to improve a great engine / vehicle. I am not selling this car. I want to intelligently / practically / "bang for buck" modify it.

I'm just looking for ideas here guys.

I have some ideas, like a modern quick spooling turbo with a big downpipe/exhaust.
Maybe a tranny swap. What other engines have the same bolt pattern as the 617?
Maybe a differential change. Maybe propane injection. I don't know I want to hear everyone's ideas and I want to discuss. I think there is some serious potential if you think about it?

Define "serious potential" and I'll provide you with the cost to achieve same..............then you'll reconsider your options.

try some nitrous:D

There isn't all that much modification potential in the 617 engine. It's just not designed for outrageous performance. It doesn't have a crossflow head and it only has 10 valves. Get an E300DT or a CDI if you want easy performance. Or if you like to tweak, get a 300SDL with a good 603 and start playing with the full load screw+pyrometer and maybe in intercooler. Anything can be done with the right amount of money, but the question of practicality arises.

Super performance on these engines does not come cheap. Everything you can easily do with stock components and easy mods have already been outlined.

Nitrous won't help much at all. Remember, diesels operate on the principle of excess air, so adding more oxygen (which is what really isn't going to do much unless you can provide the fuel to make use of it. Same goes with the boost...sure, you might be able to [dangerously] get 20psi out of your stock turbo, but all you'll be doing is drastically heating the intake charge and endangering stuff like your head gasket. Unless your IP is modded to provide more fuel (and that opens up the whole EGT can of worms), more air isn't going to do any good.

You could use nitrous to get up to speed, put the alda to full fuel, and then just add nitrous. instant oxygen more horsepower at low speeds, then you let off on the nitrous at high speeds. Basically the alda is crap just to make the engine burn abit cleaner. might save a very minute ammount of fuel in the long run. all it does, is when there is a low ammount of boost. the alda limits the ammount of fuel that can be injected. then when boost comes up, the alda allows more fuel to be provided.

this was the best explanation of Bowden cable adjustment I could find.

I am currently returning ~18 mpg... and I drive rather gently.

Besides a twitchy front end and a somewhat dragging front caliper, I cannot justify this terrible mileage.

-Engine has excellent compression
-trans is responsive but shifting improperly
-valves, timing and engine mechanicals are set.

Since the recent timing I did, I have not been able to set the linkages very well. (FSM sucks for '85 cali engines) Could they cause poor mileage to this degree? Could the trans Bowden cable cause this as well?