[N420i]

I just OBD tuned my 420i about a month ago and I'm loving the results. It ended up putting out 272hp and around 470nm. The car's decently quick on the street but I wanna take it to a trackday at the end of the month.

Powertrain wise the car is completely stock, so stock downpipe.

Despite being seriously detuned from the factory, I'm slightly concerned that flogging the heck out of an engine pushing out nearly 100nm more nm than stock might throw a rod or kill the turbo or sth along those lines.

I just talked to the tuners who did the ECU flash and they told me that the torque is not cause for concern, that the problem lies in the exhaust temps reached with the stock downpipe... However my reasoning is that being essentially the same enigne as the 30i, and sharing the whole exhaust system, this shouldn't be TOO much of a problem. After all, I'm gonna go on street tires and I can't afford to fully trash them, so I'm not gonna go full out.

Have any of you guys tracked B48s? Were there any problems I should be concerned about? Should I just stop worrying about it?

[rjd_F30]

I did a road course event in my N20 and multiple trips to the drag strip in various forms of modification. The road course event was on all stock hardware, just a tune like you. The car did absolutely fine, and I'd be even more confident in your B48 than my 70k mile N20. Modern cars are pretty much good to go for track events right of the showroom floor, so you have nothing to worry about assuming your car is in good working order. Of course some hardware modifications will be able to improve on your car's track performance, but she'll be fine on stock hardware. Just be sure to let it get fully warmed up before being aggressive and take the cool down lap seriously. Good luck and be safe

[Clemy]

Originally Posted by N420i

I just OBD tuned my 420i about a month ago and I'm loving the results. It ended up putting out 272hp and around 470nm. The car's decently quick on the street but I wanna take it to a trackday at the end of the month.

Powertrain wise the car is completely stock, so stock downpipe.

Despite being seriously detuned from the factory, I'm slightly concerned that flogging the heck out of an engine pushing out nearly 100nm more nm than stock might throw a rod or kill the turbo or sth along those lines.

I just talked to the tuners who did the ECU flash and they told me that the torque is not cause for concern, that the problem lies in the exhaust temps reached with the stock downpipe... However my reasoning is that being essentially the same enigne as the 30i, and sharing the whole exhaust system, this shouldn't be TOO much of a problem. After all, I'm gonna go on street tires and I can't afford to fully trash them, so I'm not gonna go full out.

Have any of you guys tracked B48s? Were there any problems I should be concerned about? Should I just stop worrying about it?

What boost psi did they flash your ecu too?

[N420i]

Originally Posted by Clemy

What boost psi did they flash your ecu too?

I havne't been able to do some proper logs but it seems to be maxing out at around 19.5 psi.

[RMMAGA]

interesting you got 270 running 19 psi, pretty good

do you have any logs form the dyno run? on my stage 2 tune they run it pretty rich like 11.5 AFR and they did pull timing back a fair bit form stock as well form 15 to about 10 deg

most likely detonation best way for killing our engine as it is 11:1 compression vs 10.2 for the 30i models, therefore make sure you have good fuel, the only think really holding us back is the higher compression which means we need to be extra careful with fuel

personally I would put in race fuel if your going to track it, or maybe get meth, as the high load for long period is higher risk for detonation as everything will get much hotter

[N420i]

Originally Posted by RMMAGA

interesting you got 270 running 19 psi, pretty good

do you have any logs form the dyno run? on my stage 2 tune they run it pretty rich like 11.5 AFR and they did pull timing back a fair bit form stock as well form 15 to about 10 deg

most likely detonation best way for killing our engine as it is 11:1 compression vs 10.2 for the 30i models, therefore make sure you have good fuel, the only think really holding us back is the higher compression which means we need to be extra careful with fuel

personally I would put in race fuel if your going to track it, or maybe get meth, as the high load for long period is higher risk for detonation as everything will get much hotter

No logs from the dyno run, just the dyno run. The shop that did the tune probably has them, but tuning shops in general are super secretive so I don't have access to them.

I'll try to do a decent 1500-7500 RPM pull in third and log everything and see how much timing is getting pulled.

When I went to get it done they asked me what kind of fuel I usually run and I said 95 octane (so 91 RON for those in 'murica) and paradoxically when I filled up with 98 a couple of tanks after the tune the car just seemed to run rougher than with 95... Weird...

But yeah 11:1 compression is definately holding us back. I've considered swapping out the pistons, it's really not that big of a job since it only involves dropping the oil pan and the pistons themselves aren't really very expensive parts even straight from BMW... Rods and crank is exactly the same between the 20s and 30s so pistons and rings should be everything that's needed... Perhaps a couple of hour's work...

edit: Actually no, scrap that. I thought the whole rod+piston could come out of the bottom but just realized that's impossible... So the whole head has to come off...

edit2: It might not actually be necessary to lower compression... After all the B58 is 11:1 as well and people are already getting crazy numbers out of it with bigger turbos. BigBoost is at 613whp on a 240i...

[RMMAGA]

yes B58 is actually closest thing to our 20i B48

FYI: I am currently running 22 psi flash with meth with about 10 deg peak timing with AFR between 11 and 12 at WOT, and so far so good. The thing is a beast for the money.

FYI: Do not try to run 22 PSI on this motor without a proper flash tune, I ran 22 psi a year ago, with piggy back (no flash out yet), ran 15 deg peak timing and 14.5 AFR, with meth as well. I can with high confidence say that is over the limit of what the piston can handle without serious detonation. 19-20 PSI was great, but 22 was not...

[N420i]

I tracked the thing yesterday and it held up like a champ.
Man did I have FUN with it.
It was raining on and off and the track was wet but not soaked all the time. This is a decent-sized track (Jarama, Madrid) and the gearing that seemed way too long for the street fit this track like a GLOVE.
The little B48, while admittedly not being the most exciting thing to drive, pulled like a beast and didn't miss a single beat. I'm sure the cold ambient temperature helped. But all in all it was great.

Temperatures never went above 103º for water and 115º for oil, which you imperial folks can translate through google or just take my word its well, well within normal.
Apparently I can't access the exhaust temp sensors, but the cat sensor temps were at around 850ºC, which is high, but not worrying.

Doing pulls in 3d, it's holding around 6º of timing at 6300 RPM and holding the AFR at around 12.5 under full throtle. Still slightly leaner than I would like, but the HECK of a lot better than the 14.7AFR I was getting with the JB4 I had on there for a while.

Very happy with the thing. IT's probably gonna stay like this for a while, since the next step towards Stage2 and 300bhp is DP+exhaust and that's way beyond my budget at the moment. And I need a new set of tires, too...

[Ray-India]

What maps and tuner are you using?

[N420i]

BR-Performance Stage 1
272hp and 427nm of torque.

There's a full exhaust including de-cat DP and intake in the future, and we should then be able to take it to Stage2, close to or over 300hp. I'm not sure how comfortable I am with pushing torque any higher on stock rods and pistons.

[N420i]

Originally Posted by RMMAGA

yes B58 is actually closest thing to our 20i B48

FYI: I am currently running 22 psi flash with meth with about 10 deg peak timing with AFR between 11 and 12 at WOT, and so far so good. The thing is a beast for the money.

FYI: Do not try to run 22 PSI on this motor without a proper flash tune, I ran 22 psi a year ago, with piggy back (no flash out yet), ran 15 deg peak timing and 14.5 AFR, with meth as well. I can with high confidence say that is over the limit of what the piston can handle without serious detonation. 19-20 PSI was great, but 22 was not...

Who's doing the tune and what mods are you running? At least DP besides the meth, surely?

Power&Torque figures?