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  #1  
Old 05-26-2016, 11:33 PM
Hellcat94's Avatar
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OM617 Pump Timing 24 vs 26 vs 28

The pump on my OM617 is set to 26 right now, I know 24 is the stock. It seems to idle faster now, I adjusted it slower via the length of the throttle linkage. My startups shake more and there is even a lil sputter but as soon as the car gets down the block it becomes a calm, striding W123. Its faster and still smokeless.. but should I have kept it at 24? Can someone tell me the differences? Am I burning more fuel & am I stressing out my engine? Or the opposite?
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  #2  
Old 05-27-2016, 12:36 AM
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as you inject fuel sooner, the cylinders will see higher combustion pressures and its certainly possible the engine will run 'rougher'. Likely, it is the imperfections in fuel delivery, valves, and compression between cylinders that causes this.

make sure the linkage is not restricting the IP rack lever from coming to complete rest on the idle set pin. whenever you move the pump, you must readjust the linkage.


Running at advanced timing will not damage engine. (certainly, there is a limit) But it does increase the forces seen on the crank and bearings etc.


Best course of action is to have completed all maintenance items and ensure a healthy fuel supply and injection system before setting the injection timing. A smoother running engine will deal with advanced timing much better.
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  #3  
Old 05-27-2016, 01:32 AM
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How old is the timing chain? Often advancing the pump makes up for the wear in the chain, so I wouldn't panic over 2 degrees.
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  #4  
Old 05-27-2016, 06:54 PM
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Advancing the drip timing will start hurting idle quality. Stay with 24 BTDC if you run stock turbo pressures of 12 psi.

If your running 15 psi and better you need to RETARD the i/p timing especially with no inter cooler.

Advanced i/p timing puts more heat into the piston crown and whilst the 617 has piston crown oil squirters, they can only do so much.

The i/p drive sprocket has a built in advance mechanism, so all rpm timing is affected.




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  #5  
Old 05-28-2016, 11:23 PM
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So Ive purged the fuel system, changed all the filters, put in 5 new injectors w/monark nozzles and fresh heatshields, and given it a crisp valve adjustment. My timing chain has no stretch, also glow plugs are new and my collar nuts are torque'd right. Am I missing something ? I got fresh belts, the rack damper is all the way in & oil is recent. It seems as soon as the car gets to the above the 60's in heat it smoothes out completely and idles right, i know its not my egr, is there a guide to linkage tuning? I feel like I get improper fuel amounts for cold cylinders, which causes my rough startup kinda like how a cold transmission shifts different but once it warms up the combustion is correct. Compression is grand by the way.
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  #6  
Old 05-29-2016, 11:44 PM
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What is the regular idle RPM for a 300d?
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  #7  
Old 05-30-2016, 01:03 AM
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Quote:
Originally Posted by Hellcat94 View Post
What is the regular idle RPM for a 300d?
800rpm +/- 50. Some pumps are not happy any lower but up to 950rpm is okay.

If you find the idle too high in drive...dragging you along without firm brake application or violent bump into reverse, lower it by all means.

Ran mine at 650 rpm in N for some time, although pump was fully overhauled to the tune of $1800.00. ( Required new elements ! )

The damper may need later spring to reduce the rump rump idle, you'll just have to screw it in and out until you find the sweet spot. ...but that should have been taken care of in the rebuild.

Don't turn the idle screw up too high or the engine will run away. ......make sure the STOP lever is operational before messing with the idle screw.

For other i/p tuning, there are excellent posts here about fuel metering adjustments....although yours shouldn't need it, unless your i/p builder recommends any. Did you have it rebuilt or larger elements ?





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  #8  
Old 06-12-2016, 05:11 PM
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Ok so my RPM is just under 800 and it feels real nice, I got all the throttle related linkage in appropriate ranges and I found the source for the shaky startups! After I put my pump timing to 26, my linkage was improperly set at the old 24 lengths and my engine was racing and the speeding engine at idle upset me so I adjusted my rack damper by threading it all the way in to what I believed would be as smooth as it could get, seeing as it calmed the engine. What I didn't realize that night was that I pushed it in too far and overshot the smoothness g-spot.. I was plagued by shaky startups and rough wakeup idle.. not to mention my engine had gone from one quick twist-with-the-key start to a full key twist-and-hold to get the engine on. I did more research and I realized my fault, I backed out the rack damper maybe 1 or 2mm and the startups are golden! Just like when I bought her and first changed out her glowplugs. The idle is keen now and I really like the in between 24 and 26 pump timing of 25, because 25 gives more than 24 and doesn't have the hotrod feel of 26. If anything I learned the importance of proper rack spacing, throttle linkage length and healthy yet calculated experimentation!
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  #9  
Old 06-12-2016, 06:10 PM
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Quote:
Originally Posted by Hellcat94 View Post
............... so I adjusted my rack damper by threading it all the way in to what I believed would be as smooth as it could get, seeing as it calmed the engine. What I didn't realize that night was that I pushed it in too far and overshot the smoothness g-spot.. I was plagued by shaky startups and rough wake up idle........................
Now...had you explained this in the first place, we could have got to the resolution of your problem a lot sooner.



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  #10  
Old 06-14-2016, 06:38 PM
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In my opinion (which may vary for your car) I like to set timing by advancing until it knocks at full load, and then retarding the timing just a bit from there so it does not knock.

This way you're getting the most power, and are just under the threshold for damage.

In my opinion, 24* is the setting for easy starts, "enough" power, and smooth running. If you want to go faster you will need to advance it.
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  #11  
Old 06-14-2016, 07:59 PM
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Quote:
Originally Posted by Hellcat94 View Post
After I put my pump timing to 26, my linkage was improperly set at the old 24 lengths and my engine was racing and the speeding engine at idle upset me so I adjusted my rack damper by threading it all the way in to what I believed would be as smooth as it could get, seeing as it calmed the engine.

post #2

may 26th.

warned you.
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  #12  
Old 08-15-2016, 03:09 PM
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[QUOTE=FromTheLongLongAgo;3627052]That is false.[UNQUOTE]


About slightly retarding i/p timing is not false..this is true for a street engine. ( It reduces piston heat and bearing hammering. Along with longer life of the engine and sealing components.



Not so...here's a quote from Bruce at Pittsburgh Power :

"Now for horsepower: Engine timing, you must retard
the timing as the horsepower
increases. Lower the compression ratio, increase in
jector flow, increase fuel
pressure, retard the timing and increase the manifo
ld pressure. That is the
formula for increased horsepower and must always be
followed. Now here's the
problem. A lot of owner-operators that do their own
mechanical work are not
taking the time to retard the timing. They are doin
g everything else correctly
except the timing. I realize that it's a lot of ext
ra work when doing an in
chassis rebuild. However, it's the most critical pa
rt of the horsepower formula
for engine life. With stock timing the engine will
be extremely responsive and
great for drag racing. However, piston life will be
greatly reduced. Retard the
timing for piston life!





[ QUOTE.] 950 RPM is too high. At 1000rpm the governor loses the ability to control idle speed and the engine will accelerate on its own up to the maximum no-load speed of 4900-5200rpm.[UNQUOTE]

[QUOTE]If the idle speed is set at 950rpm with the engine cold, it WILL increase above 1000rpm when hot. [UNQUOTE.]

Idle is ALWAYS set with engine at operating temperature. So your 'cold idle' is irrelevant.....



Your nit picking parts of statements does you no favours.


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  #13  
Old 08-29-2016, 07:54 PM
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I think this is the tread on advancing the timing.

DR Bert IP adjustment thread
Question for Doktor Bert

Normal timing is 24 degrees before top dead center plus or minus 1 degree. So up to 25 degrees is still a stock setting.

I tried 27 degrees before top dead center with farily now rebuilt Injectors with Monark Nozzles in them and at idle it nailed a little and when cold there was slightly visable smoke.
I did not like that so I retarded the timing till it went away.

However, once I stepped on the Accelerator pedal at 27 degrees it did seem to have more pep.

Later I re-timed using the timing locking pin so it is back to stock.
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  #14  
Old 09-14-2016, 06:18 PM
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wow someone spent $1800 to rebuild a stock IP and didn't buy a superpump instead? Crazy that ...
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