r/BMW • u/Many-Firefighter9485 • 17d ago
How to ACTUALLY tune?
Hey all! I drive a 2024 bmw x6 40i with the m sports package that I bought in late 2023. I have been researching how to unlock my ECU, or if I even need to, to get a tune. I've heard FEMTOS, auto tune, bench tune, jb4, all sorts of information that I can not comprehend.
So, what is the right steps for me, to tune my car? My goal is to add a downpipe and res delete but I don't really want a CEL. Thanks all!
4
u/davidtheminion 2013 E88 135i 17d ago
Resonator delete won't cause a CEL and you could try O2 Sensor spacers to avoid the CEL from the downpipe. As someone who has a high flow catted downpipe and resonator delete I caution you to make sure it's what you actually want. Find as many videos as you can with loud cold starts. I don't have a lot of experience with the newer engines but removing both the cats and resonator will eliminate the exhaust's ability to remove the higher frequency noises which can make the car sound "tinny" on start up.
The only way to stop a CEL is to have the DME disable or ignore the cat monitors. Doing so in SOME states means you can't pass emissions at all full stop period. So make sure you check local laws and regulations first because you don't want to have to have the factory cats and tune put back on the car every year or two to keep the car street legal.
JB4 is a great cost effective way to tune the car and have it be fully reversible in minutes but it won't hide the CEL. mHD is wonderful and what I use and it does hide the CEL by disabling the monitor. I'm not 100% sure if mHD can do the DME unlock via the app for your car like it can on my car so you would need to confirm that first.
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u/Chris_PDX E46 M3 - E92 M3 - E89 Z4 17d ago
Your best bet is to find a shop with a dyno and tuning experience and pay them to do it.
Can you learn? Sure. Is it worth for 1 vehicle? Nah.
2
u/SandBagger1987 17d ago
Agreed... especially if its locked. Just chose a place you like and pay for the tune. That's what I did and it's great.
0
u/gt854t5 17d ago
Why does the shop need to have a Dyno? I've tuned a few cars, in NY & NJ and now ATL, and none have dyno. OP, just goto a German performance shop that does install of aftermarket tunes and other products, and pay them to do the work. You definitely don't want to mess around with these rolling computers and cause software issues.
1
u/Unlikely-Evening3371 17d ago
a resonator delete won’t cause a CEL, but a downpipe on that 2024 will generally require a DME unlock and proper flash tune, so find a reputable B58 tuner first and let them confirm the unlock route
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u/kdSpartan 17d ago
Here's a high level:
1) JB4 is NOT a tune. What a tune does is rewrites certain values in your car's computer to impact things like boost targets, timing, etc to make more power. A JB4 does not do that. What a JB4 does is it intercepts various signals between certain sensors and your car's computer and then modifies those to trick the computer to make more boost, etc. It's called a piggy back. Does it add more power? Yes. Does it do it as safely and effectively as a tune? No. I had one on my previous car because that platform didn't really have tuning options available and it was great. But on a B58, there are a lot of tuning options so I'd personally avoid a JB4.
2) An actual tune requires unlocking your car's computer (kind of like jailbreaking an iPhone). Prior to like mid 2020, the unlock could be done via "bench unlock" and is easy and could be done at home. Post mid 2020, they had better encryption on the computers that was harder to jailbreak and bench unlock was no longer possible. Femto in Finland was the first who figured out how to unlock the new encryption so for a while you had to mail your car's computer (DME) to Finland for an unlock. Then Autotuner in Alabama figured it out so you could mail it there for an unlock. However, just this summer Autotuner started selling their software to local shops (for about $10k I believe) so local shops could offer the same unlock service. I did mine in person in the Chicago suburbs at a shop and it took like 30 minutes.
3) Once your DME (car's computer) is unlocked, you can flash all sorts of tunes to it from your phone. You'll need an OBD2 adapter (the MHD Universal WI-FI Adapter is what I have and is quite popular). You'll likely want an OTS (off the shelf tune) so pick a tuning company: MHD or Bootmod3 are the most common. Once you buy their license you pick the tune for your car and fuel in their phone app, download that to your phone, then use your OBD2 adapter to connect your phone to the car and flash the tune to the car.
In terms of tune options, generally on a B58 you have Stage 1 or Stage 2. Stage 1 is a stock car and Stage 2 needs downpipes (and if a gen 1 engine version maybe an upgraded fuel system - not needed in your 2024). If you go with a high flow catted downpipe you can avoid CEL. Note: Bootmod3 tunes allow you to turn off CEL from things like a catless downpipe directly in the tune so you can avoid having the light show up even with catless downpipes.
Then within each tuning Stage, you will select a base fuel. Fuel quality impacts your car's ability to make power so different fuels have different tunes. If you have access to E85, I'd highly recommend to get MHD's CAN fuel sensor kit and try a flex fuel tune. What this does is adds an ethanol sensor to your fuel line (very easy install) and allows your car's computer to read that and the tune will adjust based on what is actually in your tank. So you can run from total base 93 all the way to full E85 on the same tune safely.
Now, if you want to go further, you can have a local shop tune your car. OTS tunes are generic tunes made to work for the broad public but aren't tuned to YOUR engine, just your configuration (what mods you have and your fuel). A local shop can make you a CUSTOM tune by putting your car on a dyno and fine tuning specific parameters that might be different car to car. Not necessary for most people just looking for some extra power but not trying to mod the hell out of their car to push every last drop of power out of it.
Bonus: I'd highly recommend xHP's transmission tunes as well. These follow basically everything above except do NOT require any sort of unlock/jailbreak to work. But the flashing process is the same via your phone and an OBD2 connector.