My Results timing advanced to 28 degrees 617.952

[Diesel911]

I finally got around to Drip Timing my IP and decided to try the “Doktor Bert” suggested advancing of the timing to 28 degrees.

I was surprised to find that there is no degree marks between 25 and 30 degrees on my Crank Damper; making it somewhat of an educated guess that I ended up with 27-28 degrees.

(Note: Injectors rebuilt 1 year ago with Monark nozzles and no previous smoking issues.)

My Engine was not happy with this timing. There was some nailing at idle until the Engine was partially warmed up. There was also some wispy barely visible whiteish gray smoke that I did not have before I changed the timing. Otherwise the car ran fine. It did seem like it was slightly peppier.

Since I had marked where the where the IP started from and where it ended after I had advanced it I decided to split the difference and retard the IP ½ of the distance I had moved it.
After doing this the cold Engine nailing disappeared but there is still a slight trace of that whiteish gray smoke. This is where I decided to leave it.
Doktor Berts’s comment idle noise and proved true and it did feel a little more responsive: “The slight amount of advance definitely improves low rpm throttle response and overall smoothness of engine operation, although it does increase the noise of the combustion process slightly at idle.”

Hss thread; Camshaft & Injektor Pump Timing:
http://www.peachparts.com/shopforum/showthread.php?t=114055&highlight=advanced+timing

[Doktor Bert]

Diesel911,

When making IP timing changes, keep the following in mind; Unless your IP is brand new or recently re-calibrated, one cannot be assured that every IP will react the same to these changes. Additionally, the mechanical condition of your engine will affect overall performance too.

Keep in mind, as stated in my original thread, the important thing to keep in mind when advancing the camshaft timing is to advance injektor pump timing the same amount in camshaft degrees.

Your decision to pull back your IP timing based on how the engine reacted to the change was prudent.

No matter what you read, always, always, always believe your actual results...Robert

[barry123400]

Puts to rest the ideal that timing is not very critical on these engines. For running timing to be simular to drip timing I still feel the pressure in the base of the fuel pump might be important. From your post I think yours is probably good. Or even a little high.

Low pump feed pressure I think will retard actual running timing to some extent. Other problems might be generated as well. I only say might because not much is proven other than things seem to indicate this strongly.

On 616 engines especially I feel it is important to have this base pump pressure about correct or a little higher than recommended range at speed especially. The same for 617 engines although perhaps not quite so critical. In my mind it might be the source of the common number one rod bearing failure on far too many 616 engines.

This is unproven but based on much more fuel being fed to the number one cylinder than the other three when base pressure is non existant at speed for practical purposes.

Until proven otherwise I will not drive a 240d with low basic pump feed pressure. Again I am far from certain so just a precaution for a possible long shot . Too easy to rectify than to ignore. At worse your fuel milage should improve if corrected.

The 616 engine also seems too well engineered for this problem to be just mechanical design. Although other possibilities do exist.

The 617 has more power strokes somewhat mittigating the load on the number one rod bearing under low base pressure situations. The failure of the number one bearing is still there on 617s but at a much lesser frequency as a consequence of the additional power strokes per engine cycle I believe. This creates less stress on that number one bearing under simular overfuelling of the number one cylinder because of low injection pump base pressure.

Mercedes or bosh want this base pump pressure present at a reasonable rate. So much so they wanted it checked in these cars at dealerships when newer.

Anything from an obstructed tank screen, weak worn lift pump to plugged filters can and will lower the base pressure. I notice since this all started quite awhile ago our esteemed on site mechanic Hunter is rebuilding a whack of lift pumps now. I would like him to post his current views if possible.

It took me quite awhile to figure out how filter changes upped fuel milage. When I found the suspected reasons I then knew to change the filters just when the base injection pump pressure was starting to drop away.

Waiting for the fuel filters to give clear signs they need changing might damage engines. It is already common knowledge that fuel milage is comprimised by obstructed fuel filters. Comon logic stated it should be otherwise.

I can never see it as a problem to check your base fuel pump pressure before drip timing an engine. Especially if your fuel milage is generally lower than typical examples.

[jt20]

Thank you for voicing an Opinion on Doktor Berts simple, elegant, and effective modifications!

I am currently running @ 27* and avoiding turbo initiation since I drive mostly in a city. His recommendations gave much more responsive lower end power.

[barry123400]

You do not want to get too far ahead. The crank damper setup is not quite as rugged as some cars.

I spun a crank damper on a volkswagon by advancing the injection timing. There seems to be an increase in shock loading of the damper or what already exists is increased by advancing the timing.

So far by my observing other members efforts on 616 and 617 engines. Twenty six degrees drip advance has not resulted in any more harmonic balancer problems than normal. So it is reasonable to assume twenty six degrees is safe.

This component on these engines is a weak point in my opinion. It is very hard to determine accuracy of the drip timing in comparison to the running timing. It can be distorted by many things.

[barry123400]

I am currently running @ 27* and avoiding turbo initiation since I drive mostly in a city. His recommendations gave much more responsive lower end power.[/QUOTE]

You only have a possible twenty seven degrees if the injector base fuel pressure is in its proper range at idle and cruise conditions. If the pressure is sub standard the effective operating degrees of advance are possibly less.

If the injector springs are a little tired with age it would tend to advance the effective timing a little. Actual condition of the injector bores is another variable as well on older pumps. The pistons may have to travel further up their bores to reach pop pressure. If they have uneven wear timing to individual cylinders may vary a little. We have no reasonable reliable method to accuratly test for the real dynamic timing on the 616 and 617 setup.

If your 0-60 times accuratly done are about what they should be you then know you have to be close. If they are not what they should be we enter the situation with too many variables to establish the probable cause easily. The accuracy of the drip method tends to depend heavily on the condition of many things being in pretty good condition.

I have always tried to keep an open mind on methods we might use to accuratly check dynamic or running timing. So far no real luck. I even speculated to myself about using the tack pickup for a refference if it was universal fixed degree distance from top dead centre.

Fortunatly the timing advance mechanisim located in front of the injection pump does not seem to age. Or if it does to some extent it is an unknown. The operational advance of this timing wheel may not be optimum for todays fuels as the curve was originally designed for example. We just seem not to know much about this . A set of calibrated replacement springs may or may not improve things for example. Again just an unknown at present.

I have to wonder if the guys in northern europe have done much research. From the power levels they are extracting from these diesels you would have to think so in my opinion.

[Diesel911]

Originally Posted by Doktor Bert

Diesel911,

When making IP timing changes, keep the following in mind; Unless your IP is brand new or recently re-calibrated, one cannot be assured that every IP will react the same to these changes. Additionally, the mechanical condition of your engine will affect overall performance too.

Keep in mind, as stated in my original thread, the important thing to keep in mind when advancing the camshaft timing is to advance injektor pump timing the same amount in camshaft degrees.

Your decision to pull back your IP timing based on how the engine reacted to the change was prudent.

No matter what you read, always, always, always believe your actual results...Robert

Doktor Bert
I did not post the thread to criticize. I just recorded my experience.
Other variables:
My Engine has 200,000 miles on it.
The last time I drip timed a Mercedes was back in 1980.
When you aline the Camshaft Timing Marks I show about 2 degrees after Top Dead Center.

Another reason I posted was to hear from others who have also tried it.

[Diesel911]

Originally Posted by jt20

Thank you for voicing an Opinion on Doktor Berts simple, elegant, and effective modifications!

I am currently running @ 27* and avoiding turbo initiation since I drive mostly in a city. His recommendations gave much more responsive lower end power.

As I said it did seem to have a little more pep to it. However, I just did not like the little bit of nailing and barely visable smoke until it was somewhat warm. It was a personal preferance.

[barry123400]

I saw no critical response to Dr. Bert. I doubt he did either. On the contrary your post was quite helpful.

Overall the vast majority of threads and responding posts are very friendly on this forum. With good intent.

[Doktor Bert]

Originally Posted by Diesel911

As I said it did seem to have a little more pep to it. However, I just did not like the little bit of nailing and barely visable smoke until it was somewhat warm. It was a personal preferance.

Diesel,

I found nothing critical in your post. I only wish to remind everyone that like people, cars are unique and no two cars react in exactly the same way to a modification. To that end, you should always believe the results of your testing, regardless of what anyone tells you or what you may read in a magazine.

In your case, it was the proper course of action to retard the IP timing when your results indicated the engine was not happy with the adjustment.

Cheers...Robert

[Doktor Bert]

Originally Posted by barry123400

"You only have a possible twenty seven degrees if the injector base fuel pressure is in its proper range at idle and cruise conditions. If the pressure is sub standard the effective operating degrees of advance are possibly less..."

Interesting points....

In a hydraulic system (which is how the IP operates) I am not convinced that the supply pressure has that much to do with the high pressure side of the pump. However, a reduction in available volume could indeed create low, high pressure delivery.

Now if I recall Pascal's law, all points in a hydraulic system will always see the same pressure and two-stage pumps can produce high pressure with relatively low volumes of fluid. However, an injektion pump, at least on the high pressure (delivery side) is a single stage unit.

Now, one could easily prove or disprove this theory by adding a pressure gauge to the low pressure (supply) side of the IP and then watch the timing (electronically) while you modulate both supply pressure and volume.

experiment anyone???

Now, in the case of the GM 5.7 litre and 6.2 litre diesels, both using the Roosa-Master Rotary Injektion Pumps, they will produce the same delivery pressure regardless of the presence of a lift pump or even any degree of supply pressure. I have verified this on the test stand during calibration.

These IP's use a 6 to 7 psi supply from a mechanical fuel pump. The test stand will allow you to supply the correct inlet pressure via and electric pump, but you can also run the pump by sticking the suction hose in a bottle of fuel and either way, the delivery pressure doesn't change, so long as the high pressure side of the pump has an adequate supply of fuel, free of bubbles.

Now, I am not certain that an inline IP will react the same, but it would be worth experimenting with. I have a very good friend who owns a shop that calibrates these MBZ/Bosch inline IP's, so perhaps I will ask him this question today and see what his answer is.

Now, onto the rod bearing failures....

Based on my extensive experience in competition motorsports and engine building, I would like to point out a few things here. While this applies directly to competition engines, the principles are basically the same.

Let us assume that a given connecting rod bore is indeed round and that the crankshaft journal is also round. Let us further assume that the working clearance between bearing and journal is within acceptable limits, which is generally .001" for every 1.00" of journal diameter as a rule.

Let us further assume that this bearing/journal interface will receive a continuous flow of clean oil, with sufficient hot viscosity to maintain acceptable pressure, which is generally 10psi for every 1000 rpm of expected engine operation.

remember, oil flowing across the bearing is what cools it. That's why we open up the rod to crank journal side clearances in racing engines!!!!

If these factors are satisfied, the journal, in theory, would last until normal wear increased the clearances, oil pressure/volume (cooling) was reduced and wear increased. Eventually, pressure, film strength would be reduced until metal-to-metal contact occurs, which quickly destroys the bearing surfaces.

Notwithstanding normal wear, what destroys rod bearings??? One of the #1 killers of rod bearings in a competition engine is heat and detonation. Of course, we are speaking of a gasoline engine her, but let’s compare the two anyways.

High temperature and/or premature detonation of the fuel/air mixture creates very high combustion temperatures. Detonation also ‘hammers’ on the head of the piston with tremendous force. This force and heat quickly defeat the oil ‘cushion’ and allow metal-to-metal contact to take place between the bearing and journal.

In competition events, I have seen people experience continued rod bearing failures and try increasing oil pressure and/or viscosity, never realizing the problem is a too lean air/fuel mixture, detonation and high piston crown/exhaust temperatures. Some people I have spoken to simply found it inconceivable that heat could travel down the connecting rod and kill the bearings!!!

I have seen a Duetz Air Cooled Diesel seize a piston because of a clogged injektor deprived the piston of colling!!!! Keep in mind that in a direct injektion engine, this is a large part of the piston's cooling!!!

In a gasoline engine, detonation is destructive. However, in the 617 engine for example, the fuel is detonated on a regular basis; hence the more rugged construction required for diesel engine operation. The spray jets cool the piston crown, which not only saves the piston, but keeps the rod bearings cool!!!

But what mechanical pitfall could contribute to a rod bearing failure??? Now, let me use the Pontiac V8 as an example. The Pontiac V8, which I still build from time to time (along with other makes of V8’s) is a very rugged engine. However, they have a nasty reputation for #1 and #2 rod bearing failures. This was blamed on the cast steel rod for years, but the problem is much deeper than simple metallurgy.

On the Pontiac V8, the rod bearings are fed by oil feed from the main bearings, much like the MBZ engine and this is common to most all engines, except for some competition only variants, like the Ford 427 ‘Side oiler’ which used special oiling system.

Most engines use a main bearing with ½ of the surfaced grooved for improved oiling to the rod bearings. As the crank is spinning, the oil feed hole to the rods only lines up with the oil groove for a given number of degrees in the crankshafts’ rotation. In theory, although the pressure is always the same, there is a reduction in volume during this period of time that the oil feed isn’t aligned with the oil groove. If everything is right mechanically, then this isn’t a problem because the rod bearing is oiled during the compression stroke and early part of the exhaust stroke, where the bearing sees the greatest load.

The problem comes in when the main bearing bores are out of round, which is a very common problem on many engines that have years and years of service. When the bearing bore is egg-shaped, it reduces the volume of oil allowed to the rod bearings. I have found this condition present in every engine where a rod bearing failed, if no other aggravating conditions, as previously described, were present.

When I built my 617.120, the #1 main bearing bore was over .003” out of round and every bore, except the rear main bearing bore, needed to be align honed!!!!

The load on the spinning crankshaft is not constant. In fact, the crank actually turns in an arc, if you consider the degrees of rotation where it sees load. The reason a V-12 sounds like the spark plugs have been removed when it cranks is due to the closeness of the firing pulses in degrees of rotation. It is also why they run so smoothly.

The load on the crankshaft eventually forms the main bearing bores out of round. The condition is much worse if the engine is ever allowed to ‘knock’ from a bad bearing. This works on the perfectly round bearing bore like a jack hammer. The same is true for connecting rods. I resized all of my rods and had the block align honed prior to assembly, because there was so much out-of-roundness found during inspection.

In a running engine, we cannot check for this, but we should check for it during inspection and prior to reassembly following w rebuild.

For the running engine, clean oil, preferably one with a high ZDDP content, which protects the bearing/journal interfaces during cold starts/metal-to-metal contact, good quality oil filters and control of engine temperatures and RPM are sensible precursors to long engine life.

I hope you find this information helpful…Robert

[Doktor Bert]

I just got off the phone with my colleague at Advanced Diesel Systems in Fresno, CA. They are a authorized Bosch service center for injection pumps. John confirmed that if there is a steady supply of fuel to the injektion pump, without air bubbles, the supply (or lift pump) pressure has absolutely no effect on delivery pressure or timing.

This supports the information I received from Gus at Pacific Fuel Injection in San Francisco.

John continued to point out that the only way the timing could be affected was if there was air present in the system during the delivery cycle. John was also quick to point out that is is a loss of available volume (i.e., plugged filters, etc.) that contribute to a power loss.

Hope this information proves interesting...Robert

[Doktor Bert]

I still maintain that reducing lift pump volume, while electronically monitoring timing, would be worthy experiment, even though two Bosch service centers have told me lift pump pressure will not affect high pressure delivery in a properly functioning injektor pump...Robert

[Brian Carlton]

Originally Posted by Doktor Bert

John confirmed that if there is a steady supply of fuel to the injektion pump, without air bubbles, the supply (or lift pump) pressure has absolutely no effect on delivery pressure or timing.


Hope this information proves interesting...Robert

I'm not in agreement with the above.........or I don't understand it fully.

The elements in the IP must fill with fuel in a very short time interval. The rate of fill must be governed by the fuel pump pressure from the supply. At lower fuel pump pressure, the rate of fill must be reduced and the available power must be reduced.

There is definitely a lower limit whereby the fuel pressure will affect the power produced by the engine.

[winmutt]

Originally Posted by Doktor Bert

experiment anyone???

Yes. I never even considered using the tach signal as a method to measure timing but it is certainly with the right hardware. I have an arduino board which should certain be fast enough to measure timing with. Hopefully by the end of the summer I will have more time to tinker with this. As you can see in the link I want to use the GP's as a thermocouple. Using the tach sensor as a pick up to determine crank position is simply fantastic when combined with actual ignition in the cylinder.