Drop in 550 engine to GL450
Thread Starter
Junior Member
Joined: May 2021
Posts: 24
Likes: 3
2008 GL450
Drop in 550 engine to GL450
Ok, I've read on several forums that the 4.6/4.7 and 5.5 M273s are interchangeable with the original car's ECU - wiring harness does not require any modifications.
I'm planning to replace my '07 with a used engine. I'm seeing that the 4.7s are actually running premiums of similarly aged (and lower mileage) 5.5 M273s. For example a W221 S550 engine with approx 100K is about 30-50% chepaer than a 150K GL450 4.7. I presume this is because of the rarity/lower supply.
Would anything need to be changed? Has anyone done this? What about injectors, programming on ECU (can it be done offline in DAS?)
If there are links of a previous project in the forum, I could not find it - any help would be appreciated.
I'm planning to replace my '07 with a used engine. I'm seeing that the 4.7s are actually running premiums of similarly aged (and lower mileage) 5.5 M273s. For example a W221 S550 engine with approx 100K is about 30-50% chepaer than a 150K GL450 4.7. I presume this is because of the rarity/lower supply.
Would anything need to be changed? Has anyone done this? What about injectors, programming on ECU (can it be done offline in DAS?)
If there are links of a previous project in the forum, I could not find it - any help would be appreciated.
Thread Starter
Junior Member
Joined: May 2021
Posts: 24
Likes: 3
2008 GL450
in my mind, I’m not clear how the existing fuel system could adapt. If the o2 sensors got a lean condition, it could adapt pulse time up to about 20% before it triggered an MIL. Given that the displacement is about 20% larger. It seems that the 5.5 should have larger orifices on the injectors to handle the increased demand, but I checked rock auto and the gl450 and gl550 share injectors. I guess that it must all be controlled by the ecu. Just I’m not clear if the existing map will be able to adjust without modification.
anyone know?
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,755
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From: Emmett, ID, USA
2007 GL450
Thanks and good points. I’m fully expecting that exhaust headers, oil pan and pickup tube, and engine mount brackets will need to be transferred over. I wonder if people have only been speaking theoretically or if there was actually precedent of someone else doing this that had actually gone through it. I’m particularly interested how the ecu adapts to the larger displacement and if any modifications are needed. That would probably make me not attempt.
in my mind, I’m not clear how the existing fuel system could adapt. If the o2 sensors got a lean condition, it could adapt pulse time up to about 20% before it triggered an MIL. Given that the displacement is about 20% larger. It seems that the 5.5 should have larger orifices on the injectors to handle the increased demand, but I checked rock auto and the gl450 and gl550 share injectors. I guess that it must all be controlled by the ecu. Just I’m not clear if the existing map will be able to adjust without modification.
anyone know?
in my mind, I’m not clear how the existing fuel system could adapt. If the o2 sensors got a lean condition, it could adapt pulse time up to about 20% before it triggered an MIL. Given that the displacement is about 20% larger. It seems that the 5.5 should have larger orifices on the injectors to handle the increased demand, but I checked rock auto and the gl450 and gl550 share injectors. I guess that it must all be controlled by the ecu. Just I’m not clear if the existing map will be able to adjust without modification.
anyone know?
The +/- adjustment you are talking about is MAF vs. sensor, not sensor versus calculated using displacement and throttle position, etc.
Possibly the system compares throttle position, rpm, air pressure, temperature to check whether the MAF is operational. That check would be affected by the motor size, but the 450 and 550 are not all that different in size.
