Need help boost drop
Thread Starter
Joined: Jan 2009
Posts: 1,106
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From: Lebanon
Cls63 & C32
Need help boost drop
I have the 55 s/c on my car, the car was running strong with boost increasing along the rpm till 1.5 bars(22psi) max boost fourth gear redline, i have no bypass tb or valve.
after i rebuilt my engine: changing pistons/rings, 82mm tb (273), water/meth kit, cleaning taking off the aluminums inside the sc inlet(plenum) to make it clear without obstacle inside it, polishing a little the rotor inside the sc, the al one to clean it. turning off and out the secondary air injection and egr valves.
after those the car runs good without fault codes but the boost was dropping at wot, sometimes it goes to 1.3 bars then decrease to 1.1 at higher rpm, sometimes decrease to 0.9bars and sometimes it go to 1.5 bars.
it mades me mad, i test air leak, sc clutch, another tb, everything is right, any ideas? i am thinking now the SC!!
after i rebuilt my engine: changing pistons/rings, 82mm tb (273), water/meth kit, cleaning taking off the aluminums inside the sc inlet(plenum) to make it clear without obstacle inside it, polishing a little the rotor inside the sc, the al one to clean it. turning off and out the secondary air injection and egr valves.
after those the car runs good without fault codes but the boost was dropping at wot, sometimes it goes to 1.3 bars then decrease to 1.1 at higher rpm, sometimes decrease to 0.9bars and sometimes it go to 1.5 bars.
it mades me mad, i test air leak, sc clutch, another tb, everything is right, any ideas? i am thinking now the SC!!
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1000Hp Diesel Trucks, 2019 E63s
I'm concerned with the polishing of the SC rotors. The rotors themselves shouldn't be messed with, what exactly did you polish? Hulk, I don't think he's bleeding boost with anything, it's harder on the SC but not necessary.
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A Merc
I heard that as well but if you are pumping 14psi and then just let off the pedal that boost has to go somewhere
I'm assuming he has a tune for a bov of some sort
And yes you are right don't touch those rotors
Some have ported the sc but got very little gains
I'm assuming he has a tune for a bov of some sort
And yes you are right don't touch those rotors
Some have ported the sc but got very little gains
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1000Hp Diesel Trucks, 2019 E63s
I agree, and that's why it's so hard on the SC.
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Super Member
Joined: Mar 2011
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
It's a C32 with a e55k sc. Shouldn't be too hard to get it to 20+psi with nearly half the displacement.
Robert, is the boost level consistent on the same day and weather conditions or does it vary? If it varies on the same day and weather I would also bet that there maybe some slip. Post up your logs and I'm sure a few eyes on them will maybe at least help you figure out what to look for.
Robert, is the boost level consistent on the same day and weather conditions or does it vary? If it varies on the same day and weather I would also bet that there maybe some slip. Post up your logs and I'm sure a few eyes on them will maybe at least help you figure out what to look for.
Thread Starter
Joined: Jan 2009
Posts: 1,106
Likes: 85
From: Lebanon
Cls63 & C32
no bypass, all 32k came from factory without bypass valve, the c32 has 14.5 psi stock without bypass and the SC is not turning off when you take off you foot, it turn off only when below 1000 rpm.
i think also the problem is here, i polished the aluminum rotor not the teflon one by the paper nb 2000/1200, i don't know how we call it but the same one that we do the painting with it.
there is no stress cause the main TB is before the SC not after like turbo's.
no belt slip
55k SC with V6 3.7L, stock pulleys 22psi.
yes i made it clear but why is that the problem, can you please explain more, does anyone did it?
i'll put a video later. yes it's like a slip but how do we know what's the cause.
there is no stress cause the main TB is before the SC not after like turbo's.
no belt slip
55k SC with V6 3.7L, stock pulleys 22psi.
It's a C32 with a e55k sc. Shouldn't be too hard to get it to 20+psi with nearly half the displacement.
Robert, is the boost level consistent on the same day and weather conditions or does it vary? If it varies on the same day and weather I would also bet that there maybe some slip. Post up your logs and I'm sure a few eyes on them will maybe at least help you figure out what to look for.
Robert, is the boost level consistent on the same day and weather conditions or does it vary? If it varies on the same day and weather I would also bet that there maybe some slip. Post up your logs and I'm sure a few eyes on them will maybe at least help you figure out what to look for.
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
Don't know if you noticed this but your spark advance is retarding at the same time. I would log throttle position and your map sensor if you have it since it looks to me like your hitting a torque limit and the throttle is backing off and coming back on. As it backs off boost is dropping. I'm surprised you are using torque as your logging software given the amount of customization you have done. Also, what type of fuel are you running since that seems like alot of spark advance for that type of boost. One other thing I would check is making sure your boost gauge matches your map sensor reading.
Thread Starter
Joined: Jan 2009
Posts: 1,106
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From: Lebanon
Cls63 & C32
Don't know if you noticed this but your spark advance is retarding at the same time. I would log throttle position and your map sensor if you have it since it looks to me like your hitting a torque limit and the throttle is backing off and coming back on. As it backs off boost is dropping. I'm surprised you are using torque as your logging software given the amount of customization you have done. Also, what type of fuel are you running since that seems like alot of spark advance for that type of boost. One other thing I would check is making sure your boost gauge matches your map sensor reading.
-I think the timing is advanced when boost is dropping leaking, like going part throttle, cause when the car was running good my timing was between 19-21 wot, plus i have a low static compression ratio 8.2
-I'll check tomorrow the throttle position and map sensor(you're mentioning voltage of map or reading boost from it?)
after that i'll swap the tb with the stock 74 and i'll check
- what do you recommend me for logging from obd?
i have 2 AFR gauge one for left bank and one for right bank, also i have a fuel pressure gauge and boost one.
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1000Hp Diesel Trucks, 2019 E63s
Don't forget, he doesn't have to spin it any faster to make all that boost is motor is a lot smaller. Smaller motor=more restriction=more boost with the same rotors speeds.
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From: Folsom, CA
2005 E55 AMG
time for a weistec 
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Joined: Mar 2011
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
thanks for your reply, good points to review.
-I think the timing is advanced when boost is dropping leaking, like going part throttle, cause when the car was running good my timing was between 19-21 wot, plus i have a low static compression ratio 8.2
-I'll check tomorrow the throttle position and map sensor(you're mentioning voltage of map or reading boost from it?)
after that i'll swap the tb with the stock 74 and i'll check
- what do you recommend me for logging from obd?
i have 2 AFR gauge one for left bank and one for right bank, also i have a fuel pressure gauge and boost one.
-I think the timing is advanced when boost is dropping leaking, like going part throttle, cause when the car was running good my timing was between 19-21 wot, plus i have a low static compression ratio 8.2
-I'll check tomorrow the throttle position and map sensor(you're mentioning voltage of map or reading boost from it?)
after that i'll swap the tb with the stock 74 and i'll check
- what do you recommend me for logging from obd?
i have 2 AFR gauge one for left bank and one for right bank, also i have a fuel pressure gauge and boost one.
What I have seen at least on the e55 is that there are two sets of torque limiters. One for the engine ecu and one for the tcu. I'm wondering if the tcu is now taking control of the throttle and backing it off. I think your rotors might be fine since if they were bad, they would leak all the time and you would never see the higher boost levels you see at certain points in your run. It looks to be tune/control related to me or some odd type of slip. Did you recently change throttle bodies since it sounds like you are going to try the 74.
Good luck...
Thread Starter
Joined: Jan 2009
Posts: 1,106
Likes: 85
From: Lebanon
Cls63 & C32
You need a way to see all of these parameters on the same graph so you can review afterwards. It's great that you have gauges, but right now your only option is to try and diagnose this real time since you don't have a log of map, timing, throttle position, mass air flow, IAT, and AFR. I use an innovate LM-2 but in hindsight I would have preferred a zeitronix. I believe eurocharged also has logging software now as well if your tune is from them. Any of these three will do the trick.
What I have seen at least on the e55 is that there are two sets of torque limiters. One for the engine ecu and one for the tcu. I'm wondering if the tcu is now taking control of the throttle and backing it off. I think your rotors might be fine since if they were bad, they would leak all the time and you would never see the higher boost levels you see at certain points in your run. It looks to be tune/control related to me or some odd type of slip. Did you recently change throttle bodies since it sounds like you are going to try the 74.
Good luck...
What I have seen at least on the e55 is that there are two sets of torque limiters. One for the engine ecu and one for the tcu. I'm wondering if the tcu is now taking control of the throttle and backing it off. I think your rotors might be fine since if they were bad, they would leak all the time and you would never see the higher boost levels you see at certain points in your run. It looks to be tune/control related to me or some odd type of slip. Did you recently change throttle bodies since it sounds like you are going to try the 74.
Good luck...
i don't think it's tune related cause before the built it was running good and with the same tune.
Thread Starter
Joined: Jan 2009
Posts: 1,106
Likes: 85
From: Lebanon
Cls63 & C32
Guys i changed the supercharged but with the same sc pulley as before, the slippage/boost drop is still didn't change, so the problem is not in the SC, i found that the sc pulley is bad and it is the one slipping on the clutch!!!!
my car has no bypass, please don't ask me how is this, all c32 does not have a bypass, the TB is BEFORE the SC not AFTER like turbo builts, so when you let off gas, the tb close and the sc build vacuum.
also the only time the clutch turn off is when the rpm goes below 1000 rpm, so when idle and rpm below 1000 the sc is not working, when rpm goes higher then 1000 the sc turn on.
So i don't trust pulley/clutch anymore specially with this high boost,
i made a clutchless sc pulley and installed it on the car today, the car runs wot very good no slippage, boost went up to 22psi,
but the problem now is that the sc is working at idle and below 1000 rpm and the car idle very bad, it cannot compensate for the extra air coming from the sc on.
i have no experience with bypass or blow off valves, so please i need help, if i installed a bypass/bov can i solve the problem, is there any electrical bypass that work with rpm(on below 1000 and off high then 1000) or anything else?
thanks.
edit: also a very bad sound is coming from the rotors inside the sc when it's on at idle, the sound go when rpm is upper then 900-1000.
my car has no bypass, please don't ask me how is this, all c32 does not have a bypass, the TB is BEFORE the SC not AFTER like turbo builts, so when you let off gas, the tb close and the sc build vacuum.
also the only time the clutch turn off is when the rpm goes below 1000 rpm, so when idle and rpm below 1000 the sc is not working, when rpm goes higher then 1000 the sc turn on.
So i don't trust pulley/clutch anymore specially with this high boost,
i made a clutchless sc pulley and installed it on the car today, the car runs wot very good no slippage, boost went up to 22psi,
but the problem now is that the sc is working at idle and below 1000 rpm and the car idle very bad, it cannot compensate for the extra air coming from the sc on.
i have no experience with bypass or blow off valves, so please i need help, if i installed a bypass/bov can i solve the problem, is there any electrical bypass that work with rpm(on below 1000 and off high then 1000) or anything else?
thanks.
edit: also a very bad sound is coming from the rotors inside the sc when it's on at idle, the sound go when rpm is upper then 900-1000.
Last edited by Robert AMG; Jul 10, 2013 at 05:48 PM.
MBWorld Fanatic!
Joined: May 2011
Posts: 1,109
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From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
You could have the idle tuned to make up for the extra air. Without a bypass or clutch you don't have any other way of fixing it. Otherwise add a manual/vacuum bypass valve and it'll close as soon as you start to build boost.
