[kosmokratur]

This question might put my ignorance on display, but what sort of "torque limiters" are tuned out? I'm guessing these arent strictly mechanical. Is there some sort of software map that limits the amount of engine torque the transmission will accept? If so, wouldn't removing this result in a risk to reliability/durability? Please school me!

[M550bernina]

Originally Posted by kosmokratur

This question might put my ignorance on display, but what sort of "torque limiters" are tuned out? I'm guessing these arent strictly mechanical. Is there some sort of software map that limits the amount of engine torque the transmission will accept? If so, wouldn't removing this result in a risk to reliability/durability? Please school me!

The torque limiters aren't mechanical, it's software related in your ECU and your TCU.

The torque limiters can be removed by an ecu tune. The torque limiters can also be removed from your xhp tcu tune.

Each gear has a limit from BMW on how much torque output. An ECU or TCU tune can remove them for better driving experience (faster car).

Example: when I first had my car tuned and I was running data logs and my car was killing power at 6,000 RPM in a certain gear. The tuner had to raise the torque limiter so I could bring it up to 6500 RPM. Note: I said raise the torque limiter versus remove the torque limiter.

On xhp if you use drag mode it literally removes all torque limiters. And if you're making big power that can be a problem.

[lanlilan]

Originally Posted by WretchedRefuse

Well this thread hasn't seen a lot of action lately so I thought I'd post a quick update. Earlier this week I reached out to xHP and asked about my weak 0-30 time. They suggested a few tweaks:

1. Stage 3 tune.
2. Custom launch control with Torque +36 and Scale 15%.
3. Torque reduction for upshifts: -10% for 1-2 and 2-3 shifts.

Wow, 3.26 0-60 is fast!

Do you think XHP stage 3 is where you'll stay for now, as a daily tune?

[WretchedRefuse]

Originally Posted by lanlilan

Wow, 3.26 0-60 is fast!

Do you think XHP stage 3 is where you'll stay for now, as a daily tune?

I see that xHP just released v1.1 of the Stage 1, 2, and 3 tunes on 16-May. The official notes say, "Improved Launch Control for high-power vehicles (>700 hp)" so in theory it won't matter for me. But it will certainly be enough to tempt me to re-flash Stage 3 and have another go. I'd really like to see if the new version helps to fix the reduction in power I'm seeing right after launch. If it does, I should be able to get down to the 3.1 second range.

To answer your question, I reverted to Stage 2 since it's a little smoother in Comfort/D and Sport/D which is where I spend most of my time. But Stage 3 is completely fine too with its slightly more noticeable shifts.

[choppedliver]

Originally Posted by WretchedRefuse

To answer your question, I reverted to Stage 2 since it's a little smoother in Comfort/D and Sport/D which is where I spend most of my time. But Stage 3 is completely fine too with its slightly more noticeable shifts.

Interesting. I haven’t noticed any difference in D with stage 3 from stage 2. I will test it out. I’m still on stage 3.

[WretchedRefuse]

Originally Posted by choppedliver

Interesting. I haven’t noticed any difference in D with stage 3 from stage 2. I will test it out. I’m still on stage 3.

Hi choppedliver I flashed Stage 3 v1.1 a few days ago and honestly now I can't tell the difference in Comfort/D. The Stage 3 tune says that it has adjusted shiftmaps in Comfort/D, but I also have Fuel Saver on so maybe that has no effect. Or perhaps before I was in Sport/D or some other mode where I felt that. So I might as well keep it at Stage 3 unless I see a reason to move back. Unfortunately I haven't had an opportunity to try launching with v1.1 yet but will post results here when I do.

[choppedliver]

Originally Posted by WretchedRefuse

Hi choppedliver I flashed Stage 3 v1.1 a few days ago and honestly now I can't tell the difference in Comfort/D. The Stage 3 tune says that it has adjusted shiftmaps in Comfort/D, but I also have Fuel Saver on so maybe that has no effect. Or perhaps before I was in Sport/D or some other mode where I felt that. So I might as well keep it at Stage 3 unless I see a reason to move back. Unfortunately I haven't had an opportunity to try launching with v1.1 yet but will post results here when I do.

Thanks for letting me know.

I’ll flash 1.1 today and off to the drag strip Wednesday night. Hoping the cold air and XHP will drop a few tenths. We will see.

[WretchedRefuse]

I had a chance to do a couple of launches with Stage 3 v1.1 and there was basically no difference from v1.0. Like before, it launches very strong, then bogs, then recovers at about 30 mph and keeps going strong to 60. It's almost like my wheels are spinning, but I don't hear any squealing, leave any skid marks, or make a cloud of tire smoke.

I get the same result whether using custom launch control (+40/+25) or DSC off. The only item of note is that my times were about 0.2 seconds slower than last time when I had some octane booster in the tank. I wonder if that makes a difference with this engine?

[choppedliver]

Originally Posted by WretchedRefuse

I had a chance to do a couple of launches with Stage 3 v1.1 and there was basically no difference from v1.0. Like before, it launches very strong, then bogs, then recovers at about 30 mph and keeps going strong to 60. It's almost like my wheels are spinning, but I don't hear any squealing, leave any skid marks, or make a cloud of tire smoke.

Sounds like a normal launch to me. If you look at videos you can see the front wheels spin, bog and then the car recovers.

Like in this video - https://www.youtube.com/shorts/1UeEu9clip0

I will test launch control tonight but also keen to test (which I didn't last time) is walk the car off the line at around 2200rpm. It won't launch as hard but shouldn't bog. Which will be faster I don't know.

On a prepped strip I expect it will bog if I launch it.

[choppedliver]

Went to the drag strip last night and did 5 runs.

Using xHP stage 3 OTS. Car is stock with BMC filters and resonator delete.

Best run of the night was the first run. I was the 4th car to go while the strip was clean. It was 11.52@122mph. This is the fastest run I've ever done and it was done brake boosting to 2200 and then launching.

It went downhill from there. 11.63@121 was the worst, and the rest were 11.6, 11.62 etc. The car is very consistent.

I tried 2nd gear manual and the launch was too soft, but it spun too much with launch control.

Why did it go downhill? Mainly because it was diesel night and the sooties were tearing up the track spinning their wheels and not laying down any rubber so even though it got colder the track got worse.

Also my front tyres need replacing so perhaps that isn't helping. I did a launch on the street on the way home it spun so bad. Mind you it was 7 degrees.

There was a guy with a 2023 M5 Comp there and he ran 11.6@126 four times as he was spinning all 4 wheels. Finally got an 11.52@126 near the end. I was a bit surprised at his mph given the M5 comps have 100 more horsepower.

I've now dropped back to xHP stage 1 as I don't need all the violence and limited benefit of stage 2 or 3 in a stock car. When tuned I will try again.

I have some gopro footage to upload but no dragy as it kept giving me a stupid error in video mode that was fine when I tried again this morning. WTF!

Dragy reckoned I was slower (11.56) than the drag strip timing which is odd.

Next time I'll go when it's not diesel night. OMG! Shitty sounds, fumes everywhere and crappy blowoff valves. No EPA testing. My car is filthy from the muck.Also racing 18-22second cars is not that much fun. I think my car was in the top 10 fastest cars out of over 100 cars. Not that hard on diesel night.

Now to wait for warranty to expire in November and then tune the car. 10s here we come!

[WretchedRefuse]

Originally Posted by choppedliver

Went to the drag strip last night and did 5 runs. ...

It's very interesting that your Dragy chart from 0-100 looks almost the same as mine, despite the fact that your wheels are spinning too much and mine don't spin at all. Just curious, what tires are you using? I'm on Michelin PS4S summer performance tires that are in good shape with about 10,000 km on them. I think that your temperatures are also colder than mine now, which probably plays a part as well.

[jason526]

So I'm wondering what the XHP would do if I'm already running 3.1 0-60 and 11.1 quarter with the JB4 on Map 1?

[WretchedRefuse]

I believe there are others on this forum with that exact setup but they haven't posted any results since installing xHP.

[choppedliver]

Originally Posted by WretchedRefuse

It's very interesting that your Dragy chart from 0-100 looks almost the same as mine, despite the fact that your wheels are spinning too much and mine don't spin at all. Just curious, what tires are you using? I'm on Michelin PS4S summer performance tires that are in good shape with about 10,000 km on them. I think that your temperatures are also colder than mine now, which probably plays a part as well.

PS4S, 25000kms. They need replacing but the car still has enough grip so I'm pushing them as far as I can. There is no rego inspection as the car is under 3 years old so I don't have to rush.

Will replace with Conti Sport Contact 7s as tyrereviews.com tested them and they are the lightest and fastest tyre in wet and dry. 8% faster in the wet compare to PS4s.

[choppedliver]

Originally Posted by jason526

So I'm wondering what the XHP would do if I'm already running 3.1 0-60 and 11.1 quarter with the JB4 on Map 1?

As xHP removes torque limiters it will help. I think boosted8 had problems with the transmission pulling torque in 2nd (IIRC). I think he was running a higher map though.

[choppedliver]

Video of the 11.52 run.

2200rpm - no launch control.

[jason526]

any more updates on XHP results?

[M550bernina]

Well I've been messing with the xhp settings but I don't know how relative my information is to others as im modified.

For me I have not gotten anywhere with settings. I tried setting up launch control and lowered my launch torque and also my gear torque; brakes just can't hold the car.

So now my settings are launch in second gear. I dropped my second gear torque from 1200 nm to 800 nm. And I increased my line bump.

I have to break boost, but can only do that up to 3,000 RPM before the brakes can't hold in second gear.

This is my best run so far.

Temperature was 70° - elevation was 761 - DA was 1668.

If anybody's wondering why I'm not atop The draggy leaderboard is because the track that I go to is in the middle of nowhere with low satellite. When the draggy does work it's always about 3 to 4 10's off the track times. I do have a 60 to 130 at 6.85 on the draggy leaderboard though.

[choppedliver]

Solid result and the fastest M550i to date I think?

What mods are you running?

[M550bernina]

Originally Posted by choppedliver

Solid result and the fastest M550i to date I think?

What mods are you running?

- Custom E50 tune
- Vrsf catless downpipes.
- Snow performance stage 4 meth injection running 100% methanol.
- xhp
- Front mount intakes.
- Armytrix exhaust.
- Michelin PS4s tires on 668M heavy wheels.
- Uniden R7 to help me from going to jail.

[WretchedRefuse]

M550bernina that's amazing!! What year is your M550i? Wondering whether you have the N63TU2 or N63TU3 engine.

[M550bernina]

Originally Posted by WretchedRefuse

M550bernina that's amazing!! What year is your M550i? Wondering whether you have the N63TU2 or N63TU3 engine.

I have a 2021 M550 with N63tu3.