J666AYP
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| posted on 23/11/17 at 09:49 PM |
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Aftermarket ECU nightmare
Gents,
My brain has gone into meltdown. In a nutshell I cant use the mercedes ECU from the donor to run my project....
My problem is that mercedes in all their wisdom decided to put a electronic recirculation valve (think 2nd throttle body) on the inlet system. This
thing opens up when below a certain RPM to alow charged air back into the system. The question is can any aftermarket management systems support this
horrid thing?
As usual google has failed me, so can anyone shed some light on this for me?
TIA
Jay
[Edited on 23/11/17 by J666AYP]
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CosKev3
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| posted on 23/11/17 at 09:55 PM |
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So it's a recirculating dump valve basically?
If it is just use a aftermarket dump valve and leave that second TB disconnected?
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J666AYP
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| posted on 23/11/17 at 09:59 PM |
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Its like a dumpvalve but its progressive, not open or closed like the usual style dump valve.
I am propably wrong but the way I see it is that I need something that opens when there is a lack of boost, not too much.
Jay
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theduck
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| posted on 23/11/17 at 10:06 PM |
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Could you use a supercharged bmw mini bypass valve?
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big_wasa
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| posted on 23/11/17 at 10:06 PM |
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Do a search on here for a supercharged mx5. The guy is using the mini second tb I think ?
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mark chandler
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| posted on 23/11/17 at 10:21 PM |
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It's a rootes blower, when off throttle it just returns the high pressure see back to the low, on my DB7 this is controlled by vacumn with just
one throttle body after the air filter so before the blower itself.
Pretty sure merc blowers also have a clutch to engage the rotors like an a/c pump, my car is old so they spin all the time.
Anyway have a chat with Dale at Bailey performance as he can write code for megasquirt to look after this if required.
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J666AYP
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| posted on 23/11/17 at 10:33 PM |
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Gents,
This is the best way I can describe it....
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J666AYP
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| posted on 23/11/17 at 11:18 PM |
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Now im confused,
The few people out there who try to tune these things are doing this...
[IMG]http
://i1237.photobucket.com/albums/ff462/jayxr2zetec/72024d1138791596-modified-air-intake-slk230-26_1644273_1027200564004pm-600.jpg[/IMG]
They are venting the recirc valve back into the engine bay but not into a sealed airbox? so basicaly a turbo dump valve just without the turbo.
How can this be benificial in any way as all its doing is dumping charged air into the engine bay, kind of goes against the recirculation idea?
[Edited on 23/11/17 by J666AYP]
[Edited on 23/11/17 by J666AYP]
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mark chandler
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| posted on 23/11/17 at 11:50 PM |
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Okay, so this is just a bypass, rootes blowers displace air they do not pressurise it and take many horses to do so.
By passing the air back into the inlet on light throttle it just pumps around itself taking little power off the nose, when you apply throttle the
displaced air builds up into the engine.... And I know this sounds weird.
He's an analogy, jump on a child's roundabout, it takes a lot of effort to get it moving but once up to speed effort is reduced as you are
just keeping it spinning until you feel sick and fall off!
What Mercedes have done is popped the throttle body on the so inlet manifold down steam of the charger and have controlled passing the air back into
the inlet with electrical trickery, I expect it is done this way as you have a long air passage to the inlet (big intercooler).
I expect when people have stuck on a BOV its mangaged by vacumn between the throttle body and inlet, light throttle or shutting down this pulls the
bypass open, you really do not want this venting to air as it will use more fuel as the rotors are always trying to accelerate the air rather than
passing it in and out at the same speed.
You could just replace it with a BOV to open air or get a little more clever and have 2 throttle bodies, a new one in front of the charger
synchronised to the one you the manifold and take vacumn locally to it.
Or get simpler and just have 1 throttle body infront of the charger intake and keep the distance from the charger to inlet short.
Anyway a manual solution using vacumn can be your friend here.
[Edited on 24/11/17 by mark chandler]
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J666AYP
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| posted on 24/11/17 at 12:00 AM |
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Mark,
Thanks for taking the time to respond.
I think I understand a small part of what you have said lol.
So in theory I could just use a BOV and vent like a turbo? How would the vacumn work exactly? ould that have something to do with the tiny vac pipe on
a BOV?
Also could I route the vented gas from the BOV back into the inlet of the charger to help with boost drops between gears?
Jay
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coyoteboy
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| posted on 24/11/17 at 12:21 AM |
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This is the pinout for it - I have the same item and wondered how to drive it myself so I stripped it.
 
Eaton Supercharger Bypass
Seems PWM signal will drive it or you could get away with a straight 12V switch based on manifold pressure. If you hit the motor with 12V it pegs the
throttle open (maybe closed, I can't remember its rest state), if you PWM into it you can bias the motor against the internal spring to any
position.
Be aware that if you get this wrong and don't open it when you change gears you could potentially damage/break your main throttle and end up
WOT with no control.
I'm reasonably certain it's fail-safe (i.e. open when unpowered) but if you mess up the wiring it could have dire consequences so test it
a lot  .
[Edited on 24/11/17 by coyoteboy]
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Tazzzzman1
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| posted on 24/11/17 at 09:43 AM |
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Speak with Dave at Canems... Very knowledgeable on this type of application and very helpful. Probably has a good solution available.
Had a CANEMs ECU fitted on my supercharged MX5 using an SLK supercharger...worked a treat. I had 2 throttle bodies. I before charger and 1 after to
balance airflow/ boost control. Also used a mini dump valve
[Edited on 24/11/17 by Tazzzzman1]
[Edited on 24/11/17 by Tazzzzman1]
[Edited on 24/11/17 by Tazzzzman1]
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mark chandler
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| posted on 24/11/17 at 07:01 PM |
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quote:
Originally posted by J666AYP
Mark,
Thanks for taking the time to respond.
I think I understand a small part of what you have said lol.
So in theory I could just use a BOV and vent like a turbo? How would the vacumn work exactly? ould that have something to do with the tiny vac pipe on
a BOV?
Also could I route the vented gas from the BOV back into the inlet of the charger to help with boost drops between gears?
Jay
Okay, so you pull the vacumn out between your existing throttle bodies butterfly and inlet manifold, this operates the BOV which does not vent to air,
put it back into the inlet of the supercharger (like now), rotors are just passing air in and out at the same speed at low throttle, no boost.
When you floor it the vacumn drops away, air stops circulating within the charger and boost the engine.
If you do not circulate the air and just leave the BOV to atmosphere on light throttle you stealing power off the crank.
Regards Mark
[Edited on 24/11/17 by mark chandler]
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J666AYP
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| posted on 24/11/17 at 09:17 PM |
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Thanks gents,
On a unrelated note does anyone want to buy a mercedes engine?? lol 
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scudderfish
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| posted on 24/11/17 at 10:09 PM |
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Come on, don't fall at the first hurdle
If you don't have a love/hate relationship with the car then you're not trying hard enough
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mark chandler
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| posted on 24/11/17 at 10:21 PM |
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it's low compression lump built to take boost so bin the Eaton and strap on a big turbo
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froggy
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| posted on 25/11/17 at 12:55 AM |
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It’s electrically operated purely to react faster than a vac operated bypass . With the throttle after the charger the delay between going from boost
to vac will see the charger pumping against a shut door albeit only for a fraction of a second , the mx5 use twin throttles to get around it . I had
grief with a twin charged build wrecking the first supercharger with a small bypass and post charger throttle so added a second throttle plate pre
supercharger is solve it . That valve will open as soon as you start lifting the pedal and before there’s any vac behind the throttle .
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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