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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Jul-17-2018, 04:46:23 PM   #1
Apps
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Default DataLogged VANOS low pressure

I have an s54 swapped e39 that I daily. Since the swap I have been experiencing rough/irregular running below ~2500rpm and at idle. I have not had a VANOS check procedure run because I use Renovelo ByteLogger to datalog the major VANOS parameters from the DME.



Using datalogging I see that the exhaust and intake struggle to follow the target vanos positions below 3000rpm. Especially in a circumstance where I was crusing and then put the clutch in and coasted to a stop - i.e. rpm dropped to idle suddenly.







Intake is harder to say because it moves so little at low engine speeds that it's not clear. Additionally I get intake and exhaust position control DTC's...many for exhaust over a given time and few for intake - again related to the amount of movement on intake side at low rpm.

I should mention in the past 1500 miles I replaced all VANOS seals with Beisan parts, replaced oil pump disk with Beisan unit, replaced solenoid pack with Beisan unit, cleaned valve body per Beisan instruction, installed Beisan rattle kit, and of course timed the VANOS. The VANOS max and min angles confirm that the timing range is correct/adequate.

My theory is that the accumulator has begun to fail and thus the extra volume/pressure needed at low rpm is not available to make VANOS adjustments. Based on the position of the accumulator it makes sense that the VANOS oil pump is low output and only passed a certain rpm (~3000rpm) does it have the capacity to provide nominal pressure at needed flow rate for the VANOS actuation to function.

I'm writing this thread to see if anyone agrees with this concept before I go ahead and buy a new accumulator based on this hypothesis.

Thoughts?

Last edited by Apps; Wed, Jul-18-2018 at 11:48:20 AM.
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Old Tue, Jul-17-2018, 05:42:01 PM   #2
Obioban
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Default Re: DataLogged VANOS low pressure

I don't have any useful thoughts on the question at hand, but how is the s54 e39? Been thinking that might be the fate of my 530i......
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Old Tue, Jul-17-2018, 06:28:32 PM   #3
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Default Re: DataLogged VANOS low pressure

I'd be curious to see the improvement/ lack thereof after you change the accumulator... but I'd imagine VANOS under 3000 RPM falls into the "does it make that much of a difference"
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Old Wed, Jul-18-2018, 01:14:19 AM   #4
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Default Re: DataLogged VANOS low pressure

Obiodan - I'm enjoying it though there have been some CAN communication gremlins and mechanical obstacles to overcome (biggest is major machining of the oil pan...most frustrating the spacial constraints for the fuel regulator and filter without changing all of the fuel tank feed and return lines to m5 versions...)

Drewster - believe it or not the effect is substantial...at a minimum it makes you feel like a fool with low rpm gear changes because the motor stumbles as soon as the VANOS stops following the target - i.e. vanos control pressure has dropped
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Old Wed, Jul-18-2018, 01:34:12 AM   #5
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Default Re: DataLogged VANOS low pressure

Thinking out loud:

My feeling is this is pump/flow related based on the ability of the VANOS to precisely follow the target at higher RPM. If this was a piston or valve body leak I would have expected the lack of precision to remain even at higher rpm.

From that perspective it seems the only components are the regulating valve, accumulator and the pump itself. The pump is fairly simple and as long as the 4 rotary pistons are installed it "should" be hard to screw up.

If the regulating valve was set too low then again we would never build enough pressure to adjust...hence not affected greatly by rpm other than the point where the vent orifice is overwhelmed by supply flow.

Final the accumulator should be supplying flow for vanos movements when the pump cannot output the required flow...as is likely at low rpm.
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Old Wed, Jul-18-2018, 03:58:46 AM   #6
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Default Re: DataLogged VANOS low pressure

Quote:
Originally Posted by Apps View Post
Thinking out loud:

My feeling is this is pump/flow related based on the ability of the VANOS to precisely follow the target at higher RPM. If this was a piston or valve body leak I would have expected the lack of precision to remain even at higher rpm.

From that perspective it seems the only components are the regulating valve, accumulator and the pump itself. The pump is fairly simple and as long as the 4 rotary pistons are installed it "should" be hard to screw up.

If the regulating valve was set too low then again we would never build enough pressure to adjust...hence not affected greatly by rpm other than the point where the vent orifice is overwhelmed by supply flow.

Final the accumulator should be supplying flow for vanos movements when the pump cannot output the required flow...as is likely at low rpm.
Possibly the pressure is not keeping up. I have a used working accumulator if you want to try it, I know new they are like 3-400.

PM me.

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Discussing E46 M3 Market Sales Tracker: Please Report Your Purchase or Sale! in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)