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  #1  
Old 04-14-2019, 11:35 AM
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616 Rack limiter removal/tuning

Been poring over the archives for anything and everything
MW pump related, concerning om616 performance.

Seems like that was a forum phase that happened 6-8 years ago.
I have the google doc "Bosch M/MW pump theory" and have read about everything I could load onto my screen...

I'd love to know if any of the pioneers are still around?

Any of you 240D 616 drivers still rolling around with either your rack limiter removed, or otherwise dialed in?

This is an intimidating affair. I'd be grateful for guidance.
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Old 04-14-2019, 11:53 PM
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the removal can cause the injection duration to exceed the ability to burn the fuel dramatically increasing egt without any appreciable power gain. i would recommend around 2-3.5 turns in on the limiter max after that it wont help your power any just make for hotter egt's. all this is assuming you have a turbo or some other way of getting more air into the engine since 616's are basically maxed out stock as far as ability to burn more fuel. the 5.5mm elements are not good for any real power when i went to the 8mm M pump on my 617 it gained quite a lot even off boost from the shortened injection duration and timing.
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1985 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
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Old 04-15-2019, 11:34 AM
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Thanks for the advice.

No turbo (yet). I've read quite a few accounts from other 240 drivers who've only turned up the pump and still realized some gains. I have considered installing a wider intake manifold, however.

Did you also make an adjustment or recommend making an adjustment to Max Throttle Tension?
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Old 04-16-2019, 09:47 AM
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yes you should slightly increase the max throttle stop. be careful doing so as too much can cause the governor to bind up. also be sure to check the linkage is moving to the new limit.
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1985 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
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  #5  
Old 04-16-2019, 06:48 PM
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Quote:
Originally Posted by R-3350 View Post
yes you should slightly increase the max throttle stop. be careful doing so as too much can cause the governor to bind up. also be sure to check the linkage is moving to the new limit.
Is there anything I'm aiming for in particular? Or is it an arbitrary number of turns?
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Old 04-16-2019, 08:26 PM
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try .5 to 1 at first and maybe 2-3 max be prepared to block the intake in case it sticks the governor. it shouldn't need much to make it use the extra rack travel.
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1985 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
KD9AFT
A&P
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  #7  
Old 04-17-2019, 07:18 PM
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I really appreciate it.

Two further questions… When removing the back plate from the IP, should I expect a bunch of oil to drain? If so, must I replenish this oil or does it come from the engine after I bolt everything up.

And last, Is the throttle stop adjustment made from the outside of the pump? In other words, I don’t need to have the body open for this?
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Old 04-18-2019, 12:20 AM
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theres not too much oil in the pump and the mw is fed from an oil line off of the block by the timing gear hump (the M pumps feed from a hole in the shaft the drives the pump). that being said there may be around a pint or less in there so put something under the car before pulling the cover. also helps to lightly coat the cover in a sealant before reinstalling i like the permatex aerobic sealant since it doesn't grab as hard as rtv but stops oil well. this will make your life easier when you pull it again in the future (you will since once you start getting a bit more power out of it it gets addictive). as for the stops move the linkage and look to see what it hits at either extreme of travel. it should be relatively easy to adjust the stops but again be careful doing so as it can lead to real issues if it binds the governor. i like to have a square of plywood or something similar that will fit over the intake on hand when firing up engines i have tinkered with the pump on just in case.
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1985 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
KD9AFT
A&P
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  #9  
Old 04-19-2019, 10:40 AM
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Quote:
Originally Posted by R-3350 View Post
theres not too much oil in the pump and the mw is fed from an oil line off of the block by the timing gear hump (the M pumps feed from a hole in the shaft the drives the pump). that being said there may be around a pint or less in there so put something under the car before pulling the cover. also helps to lightly coat the cover in a sealant before reinstalling i like the permatex aerobic sealant since it doesn't grab as hard as rtv but stops oil well. this will make your life easier when you pull it again in the future (you will since once you start getting a bit more power out of it it gets addictive). as for the stops move the linkage and look to see what it hits at either extreme of travel. it should be relatively easy to adjust the stops but again be careful doing so as it can lead to real issues if it binds the governor. i like to have a square of plywood or something similar that will fit over the intake on hand when firing up engines i have tinkered with the pump on just in case.
Excellent points, thank you!
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