Choked inlet manifold on ML270

w124tony

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I dont think the shunt wiring is wrong, i get no error for the transducer being electricly disconnected like "transducer open circuit" so that part of the circuit must be correct. that just leaves the 470 ohm resistor and the diode connected between wire 5 of the MAF signal to transducer return and i have confirmed the continuity on these wires. Looking at some of the other treads the consensus seems to be hollowing out the cat is not very detrimental. Also realize possibility i may have some air leak after the MAF sensor causing problems. Going to spend the weekend looking at this so will let you know how i get on. Cheers
 

lpgautogas

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Nice post...Thank you very much!!......
smileyhappy.ico
 
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oigle

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Report on EGR disconnection effects

THIS IS A DUPLICATION OF MY POST ON THE THREAD ON EGR REMOVAL

Have finally got my driving licence back after the boys in blue decided I needed a holiday from driving – points loss.
Have now left on another longish caravan trip through southern New South Wales – probably about 8 weeks all up.
This is now giving me my first real opportunity to evaluate the performance of the ML270 since I disconnected the EGR. Thought it was time someone gave a definitive report on the effects of EGR removal from the system, apart from the obvious - prevention of the gunk buildup and associated problems.
I have now done about 1500km on this trip and am more than happy with the result. Comments are as follows:-
1. Turbo spools up more readily – whistles more noticeably on light throttle when cold. Boost seems to come in earlier.
2. The auto tranny took quite a while to re-train itself. It was hanging on to higher gears longer than I wanted it to. Perhaps the apparent extra available torque at lower revs seemed to “tell” the auto to hang on to the gear. I started using the tip shift to change at the points I wanted and it seemed to learn as it is now changing down seamlessly at the right points. The trip has involved quite a bit of hill climbing as I am following the “Great Dividing Range” down through the state. Altitude variances of around 800 metres (2500ft) makes for lots of hill climbing.
3. There is an apparent improvement of around 5% in economy compared to previous trips but I can’t be too sure on that point as I have not done a proper comparison on the same roads. The tankful I used prior to my leaving home was a definite 5% improvement tho’. That was in normal surburban use without towing. I am keeping a log of the entire trip. I used to average 8kpl towing previously so will see where the averages come out at the end of this one. So far, about 8.5kpl.
4. There is a very noticeable improvement in the power delivery from the motor. No hesitation anywhere, hot or cold, and a steady stream of torque everywhere. There appears to be more power/torque available too, but cannot state that categorically as I have no figures – just seat of the pants. The motor “sound” has changed in some areas of the rev range and sounds a bit like a v8 petrol when working hard.
Only downside is the extra time taken for warmup of engine. Quite significant. Hopefully will be better in summer.
Will give a followup report at end of trip. Would like to hear from other members as to their experience since doing the shunt.
 

dieselman

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2. The auto tranny took quite a while to re-train itself. It was hanging on to higher gears longer than I wanted it to. Perhaps the apparent extra available torque at lower revs seemed to “tell” the auto to hang on to the gear. I started using the tip shift to change at the points I wanted and it seemed to learn as it is now changing down seamlessly at the right points. The trip has involved quite a bit of hill climbing as I am following the “Great Dividing Range” down through the state. Altitude variances of around 800 metres (2500ft) makes for lots of hill climbing.
Why was the autobox holding higher ratios a problem. It was doing this due to the MAF reporting greater airflow for longer so there being greater available torque. This is one reason for the additional economy.
Wasn't there enough torque for driving under power again?
 

Alex Crow

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hopefully the maf values as seen by the ecu are roughly similar to before the mods - this is the idea of the 'shunt' is it not.
 

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It is, but I was thinking that at the point the EGR is open but not fully the MAF may be seeing greater airflow, thus the ECU may inject more fuel.

The other option is simply that the undiluted air creates a more forceful combustion so accelerates the crank more quickly, thus the ECU calculates more torque, or simply less fuel is used to create the pressure.
 

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It is, but I was thinking that at the point the EGR is open but not fully the MAF may be seeing greater airflow, thus the ECU may inject more fuel.

the shunt should still modify the maf voltage in all transient egr operation conditions. i think your second guess is correct, the car is making more power on given maf and fuel quantity values.
 

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the shunt should still modify the maf voltage in all transient egr operation conditions. i think your second guess is correct, the car is making more power on given maf and fuel quantity values.
Just shows how what a bad idea EGR is.
 
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Why was the autobox holding higher ratios a problem. It was doing this due to the MAF reporting greater airflow for longer so there being greater available torque. This is one reason for the additional economy.
Wasn't there enough torque for driving under power again?

When towing, particularly up hills, it is good to have the motor working in its best operating range, which I find to be from about 2200rpm upwards. The extra torque was allowing it to drop down to 2000 and starting to lose impetus. When it changed down, it also left the engine at lower revs as a result. Once learned, it worked well again and changed as I liked it.
Re extra torque, my take on this is that all the exhaust gas now goes through the turbo vanes and spins the turbo up earlier and faster. This produces earlier boost and, along with a denser cooler air intake, produces quite a noticeable amount of extra urge. Once working hard on heavy throttle, there is no difference but the transition period is much better.
 

dieselman

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When towing, particularly up hills, it is good to have the motor working in its best operating range, which I find to be from about 2200rpm upwards. The extra torque was allowing it to drop down to 2000 and starting to lose impetus.
Is the MAF definitely good as this engine should develop maximum torque at 2,000rpm, so that should be a good point for towing.
 
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Is the MAF definitely good as this engine should develop maximum torque at 2,000rpm, so that should be a good point for towing.

No real reason to doubt the MAF although it has done over 100000km now. Motor runs very well albeit with a chipped ecu. It would tow well at 2000 and does so on the flat country but the torque drops off sharply if you get much under that and I like to have a bit in reserve when towing 1600kg.- just to keep impetus up the hills. Once you lose speed, it is hard to get it back under those circumstances. In normal driving I am quite happy at 1800 - 2000.
 
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oigle

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Followup after trip

Home again after 7000km in 8 weeks, often over very mountainous terrain. No mechanical issues with ML. Van broke a spring set (6 leaves) on the potholed roads after the very heavy rains we have had recently. Put 2 new sets in as I figured springs only last just so many bends before metal fatigue sets in - van is 13 years old and has traveled in excess of 120,000km.

Back to ML. No probs with shunt. Engine temp stayed good when towing, around 85 to 95, except when on long downhill runs, where it fell to around 75. Seems I need a new thermostat.... Economy averaged out at 8.216k/litre or 23.25mpg. Considering the terrain, I think that was quite good. Traveled at 100kph where possible.

Think I can now definitely state that the shunt creates no issues apart from the slow warmup. From past trips comparisons, I feel the economy has improved but not by a lot. Maybe 5%. Hard to say as this trip involved much more mountainous country.

Engine harshness has gotten worse again and it bumps somewhere occasionally on startup so seems I once again need new engine mounts. They sure are not long lasting items. At least they aren't too exxy and are easy enough to do.

Where are the other members who have done this shunt - haven't seen any reports at all....
 

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i can vouch for 2x shunts, both on W210 320cdi, and both working fine. still waiting for mpg feedback, and will report back with it.
 

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I've still not done the shunt yet, but I have done the thermostat, in preparation. Takes 8 minutes to reach 85 now best case - that is going basically straight onto the motorway. Warmup around town can take 15 mins. Its much better than it was, and once it gets to 85 it stays there.

Before it would flap around all over the place but never over 80 and often dropping back into the 70s. Will probably do the shunt during the xmas break.
 

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I have done the shunt but have not noticed any increase in MPG :(
 

w124tony

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Hi, Just wanted to follow up on my post from a couple of months ago when i was having problems trying to install the shunt. the reason for the problem i was having was the wrong maf sensor was installed. installed a proper pierburg sensor and all has been well since then.
 

w124tony

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I am wondering if anyone has experianced improved mpg after carrying out the egr shunt mod?
 
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I am wondering if anyone has experianced improved mpg after carrying out the egr shunt mod?

Definitely a YES with "around town" driving. On open road work, with fairly constant boost, no obvious improvement.
 

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