128i mods on a 125i

[Mucbosh]

Two days ago, I got my first sporty car, a 2013 125i and I'm already in love with it. But I'm keen to unlock the potential (aka, the noise) which I know the car has. I intend to keep it N/A, so I've been doing a bit of research/drooling on ITB's and other intake systems (not looking to buy now, but will in future) but I can't find many 125i specific parts, its usually 128i+. I know that the 125i and 128i have the same engine, so is it right to assume that 128i parts are compatible with the 125i? Wanted to double check before I potentially spend a lot of money on something which may not fit.

[desertman123]

They're all the same

[Mucbosh]

Thanks!

[FredrikM]

No they are not the same, one big difference is that the 125i has the same intake manifold as the 130i. But the map does not open the disa valves as much as in the 130i map and because of this we only get 218 HP instead of 265. The US version (128i) does not have the disa valve intake, so to get an US spec car to gain hp the intake needs to be replaced. This is not the case for the 125i where all is needed is a remap. I have done it and i highly recommend it.

In many cases there are also a difference between the catalytic converters on US/Euro spec. cars which i most cases means that there are different exhausts for the different markets.

According to Real OEM there are only one option for exhaust manifold for the 128i (2013/01)
Part nr. 18407646692 for cyl. 1-3 and 18407646693 for cal 4-6 ULEV 2

But for the Euro version (125i) there are two versions listed.
Part nr. 18407646692 for cyl. 1-3 and 18407646693 for cyl 4-6 ULEV2
Part nr. 18407563735 for cal. 1-3 and 8407646697 for cyl 4-6 EU 4

ULEV 2 is a California Air Resources Board thing and does not comply to Europe, so i do believe that our engines has the EU 4 versions, i'm not 100% sure though so please check this before buying any exhaust parts from the US.

Also the first part of the exhaust has different part numbers.
18307560015 US spec.
18307560013 Euro spec.

All this and past experiences comparing the euro/us versions of the E46 330i makes me believe that it is the same case with the e82 125i/128i versions.

My advice is, do a very thorough examination of the difference between the US/EU version of any part that you are thinking about buying.

This site is a very good tool for checking part numbers.
Real OEM

[Mucbosh]

FredrikM Okay noted, fortunately I live in Australia so it should match the euro spec and have the disa valves.

I did about 5 minutes of research and had a poke around my engine bay to make sure, and took these two photos. I believe those are the disa valves? And yeah, I'll definitely get it mapped at some point! I know its simple, but is it expensive?

One other question, I ultimately want to get an ITB setup on the car. I've found a bunch of kits for M52's, M50's and whatnot, but none for the N52. Are they available for it?

[carscatscoffee15]

Very few.. i think there's one company that makes a slightly larger bore TB but the gains are negligible. The TB in the vehicle is a failsafe for valvetronic.

Also if you do cat delete, super sprint pipe. Sounds nice and isn't very expensive.

Keep the expensive parts just in case you sell/get tired of it.

[WrathOTM]

Yep you have DISA valves and so long as it's an N52 engine, a tune to 130i spec should be doable. And it's free.
I think it's Dinan with the TB. Not sure if it is worth the $500 price tag.

On the noise front, get a REVMOTORING intake plenum that gets rid of the factory silencer. And also get rid of the charcoal filter too if so equipped.
And then do a cowl delete too, really lets you hear all the noises emanating from the engine bay.
Also don't forget to override the factory exhaust silencer in whatever manner you choose.

[Suprgnat]

Originally Posted by carscatscoffee15

i think there's one company that makes a slightly larger bore TB but the gains are negligible.

Originally Posted by WrathOTM

I think it's Dinan with the TB. Not sure if it is worth the $500 price tag.

Only one I ever found was Westcoastriots, but their website's dead now. Think it happened recently.

[FredrikM]

Originally Posted by Mucbosh

And yeah, I'll definitely get it mapped at some point! I know its simple, but is it expensive?

I don't think it is expensive, not for a in my case 54 HP increase. I paid 3.000 SEK for my remap, that's about 425 AUD.

[MOD.Works]

Originally Posted by FredrikM

I don't think it is expensive, not for a in my case 54 HP increase. I paid 3.000 SEK for my remap, that's about 425 AUD.

What do you mean the 125i map doesn't open the Disa valve as much as the 130i map? As you wrote earlier.

Disa valve is either open or closed. There is no situation where it is only slightly open or half open.

[Mucbosh]

Originally Posted by Suprgnat

Only one I ever found was Westcoastriots, but their website's dead now. Think it happened recently.

aww

Although, its probably not a good idea to get rid of the stock plenum with the DiSA valves.

[Mucbosh]

Originally Posted by FredrikM

I don't think it is expensive, not for a in my case 54 HP increase. I paid 3.000 SEK for my remap, that's about 425 AUD.

Okay, that's not much for a pretty big gain. Although I'll probably wait until an intake is fitted to get the tune. I work for Porsche now (sacrilege, I know) where a former BMW technician has pointed me to a K&N air filter and simple silicon pipe between the airbox and throttlebody. He said that this is a cost effective way to increase power and noise. I can do the filter myself, and I think I'll get the tune done at the linked shop, but the reviews seem a little too positive... think they're trustworthy?
https://www.zadtec.net/

[Blau]

Do you have the Euro style air box? If so, take the top off of it. It'll sound great. Some ppl will tell you it affects bottom end. They're wrong, at least in my experience. I've never met anyone who actually had it who says that, just Internet folks.

I put the top back on mine after I did the Berk Race exhaust (it's a fancy muffler delete) because it was just a bit too loud to daily.

I've done exhaust, intake, SAP delete, Burger Power box and a bunch of bushings and suspension. Of all the things I've done, the bushings and suspension have made the most noticeable difference. Bilstein coilovers really woke the handling up so the power confidence increase came a little more naturally. This means I'm happier to give it the beans while turning into corners.

I'd like a real tune, but the power box was $100 and the car feels great. Someday when the tune folks drop their prices I'll get one. I still think $700-$1000 for off the shelf tunes that have been around for 10 years is too much money.

[Mucbosh]

Originally Posted by WeShallCallHerBlau

Do you have the Euro style air box? If so, take the top off of it. It'll sound great. Some ppl will tell you it affects bottom end. They're wrong, at least in my experience. I've never met anyone who actually had it who says that, just Internet folks.

I put the top back on mine after I did the Berk Race exhaust (it's a fancy muffler delete) because it was just a bit too loud to daily.

I've done exhaust, intake, SAP delete, Burger Power box and a bunch of bushings and suspension. Of all the things I've done, the bushings and suspension have made the most noticeable difference. Bilstein coilovers really woke the handling up so the power confidence increase came a little more naturally. This means I'm happier to give it the beans while turning into corners.

I'd like a real tune, but the power box was $100 and the car feels great. Someday when the tune folks drop their prices I'll get one. I still think $700-$1000 for off the shelf tunes that have been around for 10 years is too much money.

Well, the problem with that is that you lose the ram air affect and you're not getting the cool pre-radiator air anymore. I know it probably doesn't make that much of a difference, but modifying your car in a way that makes it slower just feels wrong. There's gotta be another way.

[Blau]

Originally Posted by Mucbosh

Well, the problem with that is that you lose the ram air affect and you're not getting the cool pre-radiator air anymore. I know it probably doesn't make that much of a difference, but modifying your car in a way that makes it slower just feels wrong. There's gotta be another way.

You don't lose any of that at all. The Euro air box keeps all of the duct work. Did you remove it? The intake plastics pre-airbox are all the same.

Edit: the above statement refers to the Euro box with the top on. I put mine back on after I did the exhaust. That being said, there is no Dyno evidence that shows running it with the top off decreases performance. My personal butt Dyno didn't notice a difference either. I don't care to Dyno it just to find out though as it was a bit too loud anyway.

Definitely worth the 8 minutes it takes to remove the top and feel for yourself.

I absolutely agree that you shouldn't modify your car in a way to that makes it slower. Best of luck man!

[moebiuz]

I do not recommend taking the lid off the euro airbox. I did it on my 130i and in city driving it was ok, nice sound and all that. But if you plan to take a long ride or track day it. the car will not respond as it should. Happened to me on a long journey, floored the throttle pedal and it felt like it got stuck at certain rpm, after a few seconds it started to raise, but very slowly, I freaked out when I felt this and remembered that I had my lid off. I put it back and never ever happened to me again. If you want to gain nice induct sound, you have to get the BMW Performance air intake, but it's hard to find one.

Also yes, you can get the 130i pretty easy on your 125i.

[Blau]

Originally Posted by moebiuz

I do not recommend taking the lid off the euro airbox. I did it on my 130i and in city driving it was ok, nice sound and all that. But if you plan to take a long ride or track day it. the car will not respond as it should. Happened to me on a long journey, floored the throttle pedal and it felt like it got stuck at certain rpm, after a few seconds it started to raise, but very slowly, I freaked out when I felt this and remembered that I had my lid off. I put it back and never ever happened to me again. If you want to gain nice induct sound, you have to get the BMW Performance air intake, but it's hard to find one.

Also yes, you can get the 130i pretty easy on your 125i.

Bruh... That's ridiculous.

Go look at the intake options for the n54/ n55. Most have an open design where air is being fed in through the plastic intake ducts at the front of the car/ grill. All that plastic takes air from outside the cabin and dumps it right into the air filter. And the n54/55 cars get WAY hotter than the n51/52.

I'll never understand the forum hate on this. I'll also never understand the straight up misinformation that forum ppl collectively decide is truth with zero evidence or Dyno results.

YMMV of course. I admittedly put mine back on due to the loudness factor, but I ran it all summer long with zero issues. The guy stating it made his throttle stick or take longer or whatever is telling a story that makes zero mechanical sense. Zero.