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Discussion Starter · #1 · (Edited)
Just upgraded my 5.7 Hemi to 6.4, brand new engine.

My GC Overland 2012, 9 years old and 220,000 Klms. (Old 5.7 taken as fitting charge.)

Simple swap, needed a new air intake tube, and one sensor extended.

Used old Altenator and Air con pump.

Also Exhaust flange was too big, so put my old 5.7 headers back on.

Runs like a dream, can feel the extra power, but still running in.

236273
 

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JEEP
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What was the total cost?
 

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Discussion Starter · #3 ·

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2018 Grand Cherokee Trailhawk
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Thanks for the post, Nigel. I've been juggling the cost/benefit of supercharging the 5.7 vs swapping in a 6.4, and depending on what you can get the 6.4 for, it sure seems to have a good bang for the buck. How is it a month later?
 

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Discussion Starter · #7 ·
Thanks for the post, Nigel. I've been juggling the cost/benefit of supercharging the 5.7 vs swapping in a 6.4, and depending on what you can get the 6.4 for, it sure seems to have a good bang for the buck. How is it a month later?
It’s been great, had a full remap and dyno tune, 300bhp at rear wheels, as I am using the 5.7 ecu, they had to do a full re map, it had many other codes, including the 6.1, but not the 6.4., but they did a great job, running a bit hot, so they are going to tweak it a bit to cut the fan in a bit earlier. A bit thirstier then the 5.7 around town, but good on a long run. I need to stop gunning it and take the grin off my face.
 
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It’s been great, had a full remap and dyno tune, 300bhp at rear wheels, as I am using the 5.7 ecu, they had to do a full re map, it had many other codes, including the 6.1, but not the 6.4., but they did a great job, running a bit hot, so they are going to tweak it a bit to cut the fan in a bit earlier. A bit thirstier then the 5.7 around town, but good on a long run. I need to stop gunning it and take the grin off my face.
Did you try to use the 6.4L PCM? Just curious if it can be dropped into the wiring harness and work, as in the wiring corresponds and the circuits line up. The increasing locking down of the electronics does make it even more difficult to swap a PCM that was never originally intended for your specific VIN#.

The 6.4L has a longer stroke, which makes for some big differences in engine management. I'd guess a 5.7L PCM would be close enough the engine would run OK, you just wouldn't get the full potential out of the 6.4L. The tuning with them building new fuel and spark maps would fix that and give you the best performance, basically changing the 5.7L PCM into the proper PCM for your engine.
 

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Discussion Starter · #9 ·
Did you try to use the 6.4L PCM? Just curious if it can be dropped into the wiring harness and work, as in the wiring corresponds and the circuits line up. The increasing locking down of the electronics does make it even more difficult to swap a PCM that was never originally intended for your specific VIN#.

The 6.4L has a longer stroke, which makes for some big differences in engine management. I'd guess a 5.7L PCM would be close enough the engine would run OK, you just wouldn't get the full potential out of the 6.4L. The tuning with them building new fuel and spark maps would fix that and give you the best performance, basically changing the 5.7L PCM into the proper PCM for your engine.
The new engine, did not come with an ecu, so all had to be re mapped.
 

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Did you try to use the 6.4L PCM? Just curious if it can be dropped into the wiring harness and work, as in the wiring corresponds and the circuits line up. The increasing locking down of the electronics does make it even more difficult to swap a PCM that was never originally intended for your specific VIN#.

The 6.4L has a longer stroke, which makes for some big differences in engine management. I'd guess a 5.7L PCM would be close enough the engine would run OK, you just wouldn't get the full potential out of the 6.4L. The tuning with them building new fuel and spark maps would fix that and give you the best performance, basically changing the 5.7L PCM into the proper PCM for your engine.
Hardware-wise, the 5.7 and 6.4 PCMs are identical. Only the calibration is different. A 5.7 calibration may limp a 6.4 along, but I doubt it would run happily given stuff like different sized fuel injectors, different MAP, etc. I'm sure there would be a bunch of module errors due to the VIN mismatch and possibly key/security issues. Making a calibration that works as good as OEM would be pretty easy with HPTuners or something, just need the stock 6.4 one to start with.
 
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Since the 6.4 and 5.7 are the identical PCM, its rather simple, if you used HP tuners you simply get a stock 6.4 read and transfer all the changes over, AlfaOBD for reprogramming the other modules (BCM) if needed
What I think I'm hearing is;
Why buy a new 6.4L PCM and have the dealer to try to enable it and get the immobilizer and security working, when the tools you likely need anyway, can just take your 5.7L PCM and turn it into a 6.4L PCM and keep the security data for immobilizer, etc and not have to visit the dealer.
 
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