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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #1 ·
I’ve read various posts on Internet forums and some other information on the internet, but does anyone have a definitive answer on how the ECU controls the opening of the bypass valve? I’ve read it is done on throttle position and also it is completely shut after 3000 RPM but I can’t verify if any of this is correct. I would have thought it would make more sense to operate off MAP, for example when the throttle is closed the MAP would turn to vacuum and then the valve would open.

The reason I ask is my project is running an aftermarket ECU Haltech 2500 Elite and a Weistec Supercharger with fixed pulley which utilises the OEM bypass valve. If my ECU can operate it I need to establish under what conditions or even if it needs to be fitted at all and could be completely deleted. I have also read the early SL55 and the CLK DTM did not have a bypass valve but I assume these M113K engine still had a clutched pulley. Does this mean MB only fitted it as a safeguard for over high IAT’s potentially resulting in detonation and to improve fuel efficiency? Some other OEM vehicles like the Hellcat also have a bypass valve.

Cheers
 

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W211 E55
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The bypass valve shuts fully under full acceleration. With the same question in mind years ago, I pulled one apart and inserted a small magnet inside the flap gear. Then I glued a reed switch on the outside and set it to trigger when the valve was fully shut. A LED was temporarily set up to monitor the closing in real-time on the dash. The idea behind the BPV is to back off the torque for ESP, saving fuel whilst idling and when the inlet temps get a bit off the scale to help reduce power in conjunction with the SC clutch. See pics below...

Input device Automotive lighting Peripheral Audio equipment Computer hardware



Temperature Measuring instrument Gauge Machine Gas



Gauge Motor vehicle Measuring instrument Auto part Steering wheel



Telephone Telephony Gauge Corded phone Measuring instrument

Magnet added on the flap wheel...

Office equipment Eyelash Gas Machine Audio equipment
 

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1986 560SEC, 1988 300E, 1991 500SL
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127 Posts
Discussion Starter · #3 ·
The bypass valve shuts fully under full acceleration. With the same question in mind years ago, I pulled one apart and inserted a small magnet inside the flap gear. Then I glued a reed switch on the outside and set it to trigger when the valve was fully shut. A LED was temporarily set up to monitor the closing in real-time on the dash. The idea behind the BPV is to back off the torque for ESP, saving fuel whilst idling and when the inlet temps get a bit off the scale to help reduce power in conjunction with the SC clutch. See pics below...

View attachment 2747957


View attachment 2747958


View attachment 2747956


View attachment 2747959
Magnet added on the flap wheel...

View attachment 2747960
Thanks for the info Finny, as I have aftermarket ECU I’m trying to work out the best way to control it. Fuel consumption is certainly something I’m not worried about but heat soak is. Perhaps I could just get it to open under very low TPS say 25% so I can idle and coast, or have an electronic version of the LS style mechanical control where the flap fully closes as soon as positive MAP is achieved and then also with a 100% TPS close no matter what when you mash the pedal.
 

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W211 E55
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Thanks for the info Finny, as I have aftermarket ECU I’m trying to work out the best way to control it. Fuel consumption is certainly something I’m not worried about but heat soak is. Perhaps I could just get it to open under very low TPS say 25% so I can idle and coast, or have an electronic version of the LS style mechanical control where the flap fully closes as soon as positive MAP is achieved and then also with a 100% TPS close no matter what when you mash the pedal.
Keep it simple... The proven mechanical method will work fine. Way to much work setting up an additional TB with maps etc... Heat soak is managed by splitting the air to water circuit, 10ºc fan mod and adding a larger & thinner IC radiator. I recently swapped out the old Bosch brush pumps for 2 x AMG GT brushless pumps wired always on just to make sure that the inlet temps are always kept at a minimum.
 

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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #5 ·
Keep it simple... The proven mechanical method will work fine. Way to much work setting up an additional TB with maps etc... Heat soak is managed by splitting the air to water circuit, 10ºc fan mod and adding a larger & thinner IC radiator. I recently swapped out the old Bosch brush pumps for 2 x AMG GT brushless pumps wired always on just to make sure that the inlet temps are always kept at a minimum.
Finny, when you were testing the bypass valve did you happen to identify what all the pins are for on the electrical connector?
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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I’m also very curious how this can be set up to function as close to factory as possible with Haltech. I’m dropping an M113k and 6-speed in my 78 widebody C123 and would like it to be as well mannered and efficient as possible. From what I’ve been reading it sounds like it would be wired the same as the throttle body, and could be set up on a PWM circuit to open below 25% throttle or above a certain IAT. Or, for those of us running a clutched pulley, just have it open when the clutch is disengaged…?
 

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02 CL55 AMG Clone
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I believe the bypass is a 5 wire design

12v+
1-5V+ signal for throttle posifion
Ground
Canbus1
Canbus2

im not sure the canbus wires are useful for anything but calibration and position sensors for the throttle body (bypass valve)

I believe the throttle body to be controlled by a voltage between 1-5V but I’m just guessing, my worry is the bypass valve could burn itself out maybe if the position is set too crudely (overboard).

If it truly is controlled by a 5V signal, then I guess someone could test to see at what specific voltages the valve is opened or shut for reference

I am also in a similar position finishing installing a supercharger on a e500 4matic wagon. The bypass valve situation needs sorted to get the vehicle up and running again at least
 

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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #8 ·
I’m also very curious how this can be set up to function as close to factory as possible with Haltech. I’m dropping an M113k and 6-speed in my 78 widebody C123 and would like it to be as well mannered and efficient as possible. From what I’ve been reading it sounds like it would be wired the same as the throttle body, and could be set up on a PWM circuit to open below 25% throttle or above a certain IAT. Or, for those of us running a clutched pulley, just have it open when the clutch is disengaged…?
So the Haltech Elite which I have currently cannot control the bypass valve but they are releasing an update shortly so it will be able, this is what Haltech advised:

“The E2500 can only control one DBW throttle (two DBW motor wires to the one DC motor). Only the R5 can natively run dual DBW setups (4x half-bridge outputs, for the two DC motors).

The planned update will let you use other outputs to control a DC motor as a separate control system unrelated to the DBW throttle function; this is only a new thing as generic PID control systems can be quite tricky to implement. The DBW throttle function has its own hardware allocated for control and redundancy, so the generic function does work differently (using the main processor exclusively).”

If you are running the clutched pulley I would just block off the bypass valve and not worry about it.
 

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1986 560SEC, 1988 300E, 1991 500SL
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127 Posts
Discussion Starter · #9 ·
I believe the bypass is a 5 wire design

12v+
1-5V+ signal for throttle posifion
Ground
Canbus1
Canbus2

im not sure the canbus wires are useful for anything but calibration and position sensors for the throttle body (bypass valve)

I believe the throttle body to be controlled by a voltage between 1-5V but I’m just guessing, my worry is the bypass valve could burn itself out maybe if the position is set too crudely (overboard).

If it truly is controlled by a 5V signal, then I guess someone could test to see at what specific voltages the valve is opened or shut for reference

I am also in a similar position finishing installing a supercharger on a e500 4matic wagon. The bypass valve situation needs sorted to get the vehicle up and running again at least
I believe the bypass valve is the same as a DBW throttle body but it is sprung open not closed. It requires a + for the motor, a - for the motor, position switch +5V, position switch -, and then an output for the position switch. I don’t know however if it has only a single position switch or 2 for redundancy like a DBW throttle body.
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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It sounds like it would be pretty easy to rig up hot and ground to the motor and feed it 0.05 or 4.95v via the 5v DPO on the Haltech. It doesn’t need the full redundancy or even any resolution the way the actual throttle body does.
From what I’ve been reading, just blocking it off will be pulling air past the supercharger scrolls and create a lot of resistance and effectively choke the engine. I’d like the thing to breath as easy as possible so I can coax 25+mpg out of the thing on the highway.
 

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Discussion Starter · #11 ·
Ideally I just want to open the valve at 0 throttle to help stop some heat soak. This is of course completely dumbing the system down but fine for me, I’ll talk to Haltech again and see what options there are to just give the motor a trigger to fully close.
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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Please share what they say, I’m betting if they give you a solid way to do that, I can make it work for what I want too. Another idea would be to run it off an idle air control valve circuit… gotta think that through to see if it would actually work.
 

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02 CL55 AMG Clone
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Looks like I was right and wrong about some things

the bypass valve is a 6 wire design, not 5

but I was correct that the position is controlled through a voltage between 0-5volts.

bypass valve pin out I have interpreted so far
Pin 1 is to control the actuator motor high side
Pin 2 is a potentiometer power output low side for both sensors, should read 5V with ignition on
Pin 3 is a potentiometer power output for the high side for both sensors, should also read 5v
Pin 4 is a control signal for the low side of the actuator motor
pin 5 is the potentiometer 2 signal input, .3-.9 volts is with the bypass valve closed, the voltage is supposed to rise as the accel pedal is operated
Pin 6 is potentiometer 1 signal input, 4-4.6 volts while throttle is closed, this value is supposed to drop as the accel pedal is operated

I still need time to interpret this data, here’s my first guess at the ideal setup to control the bypass valve without the m113k ecu

pin 1 - needs 12v power (or maybe this is the ground)
Pin 2 - needs 5V power (does it need 5V constantly?)
Pin 3 - needs 5V power (does it need 5V constantly?)
Pin 4 - chassis ground? (Or maybe this is the 12v source)
Pin 5 - signal input, needs to be determined at what value between .3-.9 volts is closed position, this voltage should be ramped up to open the valve I believe
Pin 6 - signal input, needs to be determined at what value between 4-4.6v is closed position, this voltage should lower as the valve is opened I believe
 

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Discussion Starter · #14 ·
ctravis595 where are you getting your information from? I have found the below wiring diagram from a website with M113K kompressor information, the website is no longer up but it said it was the diagram for the bypass valve. Also below I have a pin diagram for the wiring on a Bosch DBW throttle body which has the same connector as the bypass valve.

Rectangle Line Slope Parallel Font
Font Parallel Technology Office equipment Input device
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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I’ve done some more digging and found someone on the megasquirt forums using a Mercedes bypass valve as a blow-off valve using one of these boards to control it. This is definitely the route I’d go if I were still using megasquirt for these swaps but I’m hoping Haltech gets back to you about a built in feature that can control a servo motor apart from the throttle body.
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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And it looks like Haltech offers something just for this use as of February for not much more money that’s considerably less work to install than the pololu.
 

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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #17 ·
The Haltech Nexus 5 is currently capable of controlling 2 DBW throttles, so it is capable of controlling the M113K DBW throttle and also the bypass valve. The Elite 2500 can currently only control a single DBW throttle. But they advised in 4 to 8 weeks a software update will be released that will allow the Elite 2500 to operate a second DBW throttle with the aid of the DCMD.
 

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78 Widebody C123 M113k/6-speed, 70 W108 m113/6-speed, 85 190E 2.3-16 Lotec, 87 S124 OM606/6-speed
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That's great news. I already have a Haltech 2500 on the shelf that I was going to install on my M113 W108 but when I found the widebody C123 I decided to leave the megasquirt on the W108 and save the Haltech for the that. Just ordered the DCMD, and it looks like the software is already available for controlling electronic waste gates and such. That should be enough functionality to run the bypass valve, it doesn't need the full control and resolution of the throttle body unless it's being used to boost management. Hopefully the heat here breaks soon and I can swap out the NA 5.4 for the m113k I finally picked up.
 

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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #19 ·
The add on's keep coming haha, I still need the dual wideband O2 control kit, fuel pressure sender and DCMD. Did Haltech advise you will only need a single HPI8 for the coils or are you running a different coil setup? I've heard conflicting reports of some people having to run twin HPI8's, basically a output for each spark plug but Haltech told me I should be able to split each HPI8 output to fir two sparks per cylinder.
 

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1986 560SEC, 1988 300E, 1991 500SL
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Discussion Starter · #20 ·
OK so I just spoke to Haltech and they advised the bypass valve can be simply opened or closed by applying 12V to the motor through a DPO. Their only concern is the longevity of the motor receiving full current. What I will do is get my 12V bench tester out and apply 12V to the motor and see how much current it draws to keep it closed. Then can make a call on this and also whether the 1A of the DPO is enough or if a relay is required. Setting wise that DPO can be configured as a Generic Output with 'state' signal type meaning it can utilise up to 3 different conditions to satisfy whether or not the valve is open or closed, this is limitless and could be a function of RPM, TPS, MAP pressure etc. I will revert with the bench test results.
 
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