Why overadjusting or removing ALDA is a performance DECREASE. - PeachParts Mercedes-Benz Forum

winmutt · #1 04-12-2007, 10:30 AM

So I am hypothesizing here and please speak up if I am wrong....

Backing the ALDA all the way out or removing it is detrimental to your acceleration. Below full or half boost, etc, you are over fueling. Fuel takes up space in the cylinder (uncompressable), space that could be used by compressed air. With the ALDA properly adjusted you should see more acceleration as the AF ratio in the cylinder is higher than with it removed or backed all the way out. Not to mention the fact that you are just wasting fuel.

Thoughts?

rrgrassi · #2 04-12-2007, 10:35 AM

Are you trying to rattle Lance's cage?

obiwanrazzy · #3 04-12-2007, 10:48 AM

I don't know about backing out all the way or removing, but from experience I gained a *lot* from just backing it out a quarter turn. I've avoided doing more as I assume I'd loose too much fuel econ. Power is more than sufficient now in my case... Individual results may vary 'tho.

#4 04-12-2007, 10:57 AM

If I turn mine out "too far" the engine seems to over-fuel an I can feel it hesitate significantly when accelerating from an idle. Also, the smoke is ridiculous. The folks who gain from removing them completely (on a 617, at least) probably have IP "issues."

winmutt · #5 04-12-2007, 11:06 AM

I am willing to bet adjusting linkage will resolve what most people have been fixing with backing the ALDA out. Sure the inner spring wears, but I know in my case I should have done the linkage first. I posted this over at the super turbo forums for more input.

spark3542 · #6 04-12-2007, 11:11 AM

Quote:

Originally Posted by winmutt

I am willing to bet adjusting linkage will resolve what most people have been fixing with backing the ALDA out. Sure the inner spring wears, but I know in my case I should have done the linkage first.

To add a data point:

Alda is removed completely, mileage is documented at 26 running WVO/RUG on a combination of city/hwy, no hesitation on acceleration.

Alda has been off for the last 14k miles.

#7 04-12-2007, 11:12 AM

I agree, everything else should be adjusted correctly before messing with the ALDA. I have a new (reman) IP and I believe all the linkage is correct, but I still gained a little by adjusting the ALDA (slightly). I have decent power with negligible smoke and no feeling of over-fueling. It's very easy to over-do it.

winmutt · #8 04-12-2007, 11:22 AM

Quote:

Originally Posted by spark3542

To add a data point:

Alda is removed completely, mileage is documented at 26 running WVO/RUG on a combination of city/hwy, no hesitation on acceleration.

Alda has been off for the last 14k miles.

ALDA is really only going to affect city drving when it comes to economy. Thats all I really do. Also is your overboost solenoid removed?

babymog · #9 04-12-2007, 11:39 AM

My experience with diesels is that overfueling will increase power.

There is a point of diminishing returns, but going beyond the normal no-smoke point to where you get smoke will increase power.

With this increase of power comes: More fuel consumption, Higher EGT, More Smoke.

You will see high-performance diesels belching smoke, because the easiest and cheapest way to get more power is more fuel, it produces more heat which is more power. To do it properly you of course want more boost and an intercooler/aftercooler, the cooler air into the cylinder means higher density = more oxygen/heat/expansion/power.

Removing the Alda is IMO not necessary unless something is wrong with it.

The Alda/aneroid is there to prevent overfueling and therefore smoke on takeoff, simply put it is a way for a mechanical injection system to fuel the engine efficiently with little-no boost (idle & low RPM) and then compensate for the additional fuel necessary at higher boost. Since it is designed to LEAN the mixture without boost, its default is to fuel as if there were max. factory boost at all throttle settings, or in other words the absence of the ALDA will cause the IP to assume that there is max boost all of the time which will be a rich mixture at low boost. Heavily over-fueled off-boost can cause hesitation, lots of carbon, possibly ring fouling.

If you remove the aneroid so that you can control fuel completely with your foot, you can come off idle with such a shot of fuel that it will sputter.

Personally, I feel that a properly operating and adjusted ALDA is good. More off-boost power can be had by overfueling, which removal of the ALDA or over-adjustment of the ALDA can provide, but it should not affect the full-boost power/mixture.

WD8CDH · #10 04-12-2007, 12:16 PM

What a lot of people forget is that the ALDA is not a control, it is a LIMIT. If the "GO' pedel isn't pushed down to the point of overfueling on a properly adjusted ALDA, the ALDA does nothing so it should not effect part throttle cruising economy or power.

#11 04-12-2007, 12:24 PM

Quote:

Originally Posted by WD8CDH

What a lot of people forget is that the ALDA is not a control, it is a LIMIT. If the "GO' pedel isn't pushed down to the point of overfueling on a properly adjusted ALDA, the ALDA does nothing so it should not effect part throttle cruising economy or power.

Correct, it does nothing for "cruising economy or power." However, the ALDA setting does affect acceleration. If it's too lean the acceleration will be noticeably reduced. If it's too rich, even moderate peddle position will result in over-fueling (more smoke and possible hesitation). Removing this "limit" will make the car much less user friendly.

Brian Carlton · #12 04-12-2007, 12:42 PM

Quote:

Originally Posted by WD8CDH

What a lot of people forget is that the ALDA is not a control, it is a LIMIT. If the "GO' pedel isn't pushed down to the point of overfueling on a properly adjusted ALDA, the ALDA does nothing so it should not effect part throttle cruising economy or power.

This bears repeating.

The rack controls all.

Your right foot controls the rack.

If the ALDA is in place and functioning, the spring system prevents the IP from providing the full fuel that is demanded by your right foot, because there is insufficient air to use that fuel. The cylinders are then overfueled and black smoke will be the result. Performance will probably not suffer markedly unless the smoke is very severe.

If the ALDA is removed, you can achieve the exact same results by not mashing your right foot when the engine is off boost. Give it 50-60% fuel until the revs climb up above 2200. Then you can provide full fuel if necessary.

#13 04-12-2007, 12:58 PM

Quote:

Originally Posted by Brian Carlton

If the ALDA is removed, you can achieve the exact same results by not mashing your right foot when the engine is off boost. Give it 50-60% fuel until the revs climb up above 2200. Then you can provide full fuel if necessary.

I agree, but in practice this is very difficult on a 617. I've tried turning up the ALDA on mine and I need to restrict my foot movement VERY carefully to avoid smoke/hesitation (below 2000 rpm). As we've discussed, I think the 60x design is less sensitive to over-fueling.

Hatterasguy · #14 04-12-2007, 01:51 PM

I have had good results with an adjusted ALDA, I think removing it would be more trouble then its worth.

winmutt · #15 04-12-2007, 02:40 PM

Adjusting yes, backing all the way out on the other hand, not so good.

For ****s and giggles, where do you guys start seeing top boost in relation to what gear and RPM? I dont seem to get above 10 until way into 3k. According th the FSM I should see 11psi around 2000rpm. Still haven't done leak checks yet, althought the 2 missing bolts on the pre turbo exhaust flange are probably a sign that I am leaking all over the place.