M125i 6 cylinder 1 series

M125i 6 cylinder 1 series

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Griff43V8

Original Poster:

90 posts

11 months

Wednesday 24th April
quotequote all
this car appears appealing, as I understand it is reliable and flash upgradeable to 128i power c. 275bhp with 30-40mpg on open roads.

I want a simple reliable good sounding compact with great mpg.

I understand there may however be various flavours of engine - black top / silver top, 3 stage inlet with double diss etc! - elec or hydro steering etc

I think I want to target the last of the hydro racks, c. 2010? - Do all UK 125is come silver top with triple stage inlet, if not advice plse

The exhaust doesnt sound great on youtube vids, std or modified - I assume the Cats are responsible as my old m125i sounded sweet and detailed.

As it must stay legal, presumably Sport Cat and alternative rear box is as far as u can go..at best - I have heard of M box, 135 etc - whats best? - Dont want loud, do want creamy detailed, NO bang / pop, just mellow burble.

Re inlet - as it has separate intake runners, presumably an airbox would emulate the n/a M3 6 cylinder? - Any affordable options? Dont want to increase cost of car by 30% just for an air filter box! - Happy with something sounding halfway between std and the old M3 (which was excessive in the one i tried)

Testers criticise ride as way too soft - I do want ride comfort, is the 125i M the way to go? - How do tyre specs compare - nothing too low thanks.

Does the 125iM come with the big bolster seats? Better sounding exhaust? -Same triple stage inlet and power?

Lastly, do they really average mid thirties overall and over 40mpg at 70 mph?

Thks


Mr Tidy

22,411 posts

128 months

Thursday 25th April
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I haven't had one, but they have the N52 engine which I think is great. I've had 2 in Z4s and 2 in 3 Series.

As I understand it the 125i only makes less power than the 130i because of the mapping, so a re-map should get it to around 265bhp like the 130i always had with no need for a different manifold. I think the manifold thing related to the later N53 engines that got fitted to E9* 3 Series, but was never put in the 1 Series.

From what I can make out my first Z4 had a black-top as it was built in October 2006, my second had a silver-top as it was built in August 2006 but there really was no difference in how they drove.

Anyway the E82 125i didn't go on sale until November 2007 so I expect they'll all be black-tops, and all have EPAS as that got introduced on 1 Series in the March 2007 facelift. I also had a 2007 facelift 123d and to be fair the EPAS on that was way better than on my Z4s, even though I still prefer the HPAS on my current E90!

If you want the M-Sport seats you probably need to look for a Sport model as they had them as standard, although some SEs may have had them as an option. Sport models will have M-Sport suspension too so lower and stiffer, but also 18" wheels so it's all a trade-off between handling and ride. My 123d was an SE "Sport Dynamic" so it had the M-Sport suspension and seats but only 17" wheels which struck a compromise that worked for me.

I'm not sure Cats are the issue on sound. The N52 sounded way better in my Z4s than in my 3 Series, so a back-box might be the way to go.

Fuel wise my Z4s averaged 32.3 and 34.2, my 3 Series 33.8 and 32.6 mpg during my ownership. But now I'm getting on a bit there is no commute in there, and I can avoid rush-hours!

Hope that is of some use anyway.



Griff43V8

Original Poster:

90 posts

11 months

Thursday 25th April
quotequote all
Thanks for helpful response - yes, on balance it seems the EPAS isnt heavily criticized over the HPAS

One thing I forgot to ask that is important....

Do they suffer from rusting, particularly underneath where I shall not be checking potential purchases (nrly 70 and dont bend too well lately!)

Also looking for advice from all for favoured rear silencers and inlet mods that arent too intrusive and are old style detailed, soft and melodic rather than modern hard, crack and pop!

Places for the 130i+ style ECU re-flash for over c.280 with silencer and inlet?

If cam changes arent prohibitively expensive, specialists who could provide a more 'cammy' ramp in performance?

DMF / lighter SMF - what sort of costs involved, with and without labour - Cheaper better solution when due?

thks

Mr Tidy

22,411 posts

128 months

Thursday 25th April
quotequote all
Griff43V8 said:
Thanks for helpful response - yes, on balance it seems the EPAS isnt heavily criticized over the HPAS

One thing I forgot to ask that is important....

Do they suffer from rusting, particularly underneath where I shall not be checking potential purchases (nrly 70 and dont bend too well lately!)

Also looking for advice from all for favoured rear silencers and inlet mods that arent too intrusive and are old style detailed, soft and melodic rather than modern hard, crack and pop!

Places for the 130i+ style ECU re-flash for over c.280 with silencer and inlet?

If cam changes arent prohibitively expensive, specialists who could provide a more 'cammy' ramp in performance?

DMF / lighter SMF - what sort of costs involved, with and without labour - Cheaper better solution when due?

thks
I don't think they are known to have rust issues, but my E87 was only 7 years old when I sold it!

Exhaust wise maybe firms like RPI could help. My Z4M has Powerflow back boxes and they sound great. I know AFE do an intake set up for Z4s so they might have something that would work on a 125i.

I have read a positive review on here for a 125i remap for Evolve - link here:- https://www.evolveautomotive.co.uk/products/evolve...

A cam change might get expensive as I'm pretty sure the cam-chain is on the back of the engine.

No idea about any flywheel changes, but I wouldn't be considering that until I needed a clutch!

If it's a manual and 1st to 2nd gear-change isn't great removing the Clutch Delay Valve should improve things.

Griff43V8

Original Poster:

90 posts

11 months

Thursday 25th April
quotequote all
yes, for sure , not Looking to change clutch / fly !

Thks for other info and shall check out link

smile

bodhi

10,543 posts

230 months

Friday 26th April
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I've had one for 10 years now and it's been a brilliant little car. A few answers off the top of my head:

- All 125is have the same engine and inlet manifold, meaning the 130i flash is all you need for 260 - 280 bhp depending upon who does it

- They all have electric steering - not full of feel but accurate and has a nice weight to it

- The ride is definitely not floaty on the M Sport - it can get quite jiggly and harsh until you take the run flats off. I went with Micheling PS5s and they are far more comfortable.

- 30+ MPG is only really possible on the open road, round town it's more like 25. Mine's currently averaging about 28.

- I find the normal exhaust fine - reasonably quiet around town but has an active exhaust flap which opens at 3000 rpm or at large throttle inputs. Sounds great in a tunnel and I've never needed more noise. When it's being dropped off from having work done I can tell when it's nearly home let's just say.

- All M Sports should have the heavily bolstered seats, which I find very comfortable now I've adjusted them properly.

Main thing to watch out for on the engine are oil leaks and the water pump. Other than those and an appetite for ABS Sensors mines been perfectly reliable.

Griff43V8

Original Poster:

90 posts

11 months

Friday 26th April
quotequote all
thks for reply, yes I too have now discovered that:

all UK 125i have Triple Inlets with Dissas, same CR and build as 130i, requiring only a simple 130i map upload to get 275bhp

VANOS solenoids need replacing @ c.100k and are easy and inexpensive

The oil filter gasket needs replacing @ c.100k and are easy and inexpensive

The Water pump and thermostat are an ongoing concern as elec. or mechanical failure results in overheating / breakdown / engine shutdown at best - not straightforward to replace due to design burying it deep down under inlet etc - Replacement Cost Unknown **

MPG reports vary enormously. Some people claiming 50 mpg on light throttle cruise (seems unlikely / inaccurate readings) - Am hoping for c 40 mpg cruising around motorway limit and 35 mpg min Overall average, incl backroad blasts - These would be both surprising and reasonable for a daily driver, covering 12k pa

I have yet to hear an aftermarket exhaust better than the 128i / 130i original

The inlet must be able to release an early M3 type guttural inspired howl with some 3D printed parts?

==========



I dont like the saloon type steering wheel - My Zoe wheel was infinitely nicer - Is there a smaller, more sports orientated wheel that is affordable and replicates controls / interfaces ok?

Presumably the OE rims take non run-flats without difficulty?

I see some people put same width tyres front and back instead of staggered - if u r of an age where snap oversteer is no longer fun on a bumpy backroad with surprise corners, does car settle down if u stay staggered and fit more grippy tyres on rear only?

bodhi

10,543 posts

230 months

Friday 26th April
quotequote all
Not sure on the steering wheel - mine has the M Sport wheel which I'm a big fan of - not too big and the wheel mounted controls are in easy reach.

I've put 120k on mine taking it up to 175k, haven't had to touch the VANOS solenoids, water pump needed replaced at 169k (was original as far as I can tell). Others report they last 80 - 100k.

Wheels take non run flats fine, mine were a straight swap from the original Potenzas (terrible tyres) to Pilot Sports. I went up 10mm front and rear (225/40 on the front, 255/35 on the rear iirc) due to tyre availability at the time, no issues in fact the Speedo is more accurate now.

No issues with grip at the rear, even in the wet with Pilot Sport 5s. It needs a lot of provocation - i.e driving like a dick - to make it break traction.

Griff43V8

Original Poster:

90 posts

11 months

Friday 26th April
quotequote all
thanks

I shall, hopefully be upgrading to around 280bhp, hence worry re rear breakaway - some alarming youtube completely sideways driving demonstrations - fun with a safe run off, alarming on public roads.

I see u have recently had the water pump done - How did the failure show itself? - Dash warning of pump failure? Complete shutdown? - I see BMW chose to hide the engine temp from customers, which May be ok in normal operation, however crazy if offered limp mode / no warning.

What is the cost of parts - cost of labour please - any specialists up to looking after N52 in Northants area?

Your mileage is very encouraging - amazing that an engine capable of nr 100bhp / litre and 7k redline apparently survives 200k miles smile

Mr Tidy

22,411 posts

128 months

Friday 26th April
quotequote all
FWIW you might want to upgrade the front brakes if you get a remap as 130is (and 123ds) had bigger front discs but then you'll also need at least 17" wheels to clear them.

The water pump in my first Z4 died after 60K miles, but it had a temperature gauge and the red light started flashing! I drove it another 5 or 6 miles home as I was on an unlit NSL dual-carriageway on a December night and it did go into limp mode, but caused no lasting issue. The BMW Indy I was using bought the new pump from BMW and in 2015 it was £500, so total bill was just over £800. eek

When I had one die in my 325i it was on 135K, but it may have been its second! No temperature gauge, just an amber light followed by a red one in less than a mile, but it was a sunny day and I found a layby so I just waited for a tow from the RAC. Used the same Indy but he bought the new pump elsewhere for £300 so bill was just over £500 that time. The car was still running fine when I sold it on 139K.

The OE pumps are made by Pierburg and come with new fitting bolts as they are aluminium single-use ones. Because they just die some owners get a new one fitted to avoid being stranded if they don't know the cars history.


Court_S

12,997 posts

178 months

Friday 26th April
quotequote all
A remap on the 125i definitely wakes them up. I had a 130i at the same time my wife had a 125i cab, and her car was flat as anything higher up the rev range. I had it mapped by P Torque where it made 270bhp. Once mapped it probably felt a bit better than my 130i due to the slightly smoother torque curve.

Fuel economy was improved post map too. On a decent run, it’s happily return mid to high 30’s. The long term average was circa 28mpg taking into account the short trips my wife usually does. The 130i brake upgrade is well worth it if mapping.

The EPAS is honestly fine. BMW’s HPAS is nice enough, but it’s still not amazing. Fitting M3 arms adds a bit of negative camber plus better bushes and seems to make the steering better.

Exhaust wise, might be worth seeing if a 135i back box fits - that made my 130i sound great although they’re quite hard to find these days.

Sofa

429 posts

93 months

Friday 26th April
quotequote all
bodhi said:
Wheels take non run flats fine, mine were a straight swap from the original Potenzas (terrible tyres) to Pilot Sports. I went up 10mm front and rear (225/40 on the front, 255/35 on the rear iirc) due to tyre availability at the time, no issues in fact the Speedo is more accurate now.

No issues with grip at the rear, even in the wet with Pilot Sport 5s. It needs a lot of provocation - i.e driving like a dick - to make it break traction.
I'm on 225/40, 245/35' PS5s on mine and it seems like a good combo personally, steering feel has improved a little and I've honestly not been brave enough to find the limit of grip in the front end. The rear is virtually impossible to break loose, even if you're trying- I could get a little slip out of the Nankangs I bought the car with, but even then only when I really wanted to, and that was when they were at MOT Advisory levels of tread.

There's a few common codes which the water pump throws up when its starting to go- you can pull these with an OBD2 reader (Bimmerlink is the recommended app) but it won't actually tell you otherwise until you're stuck at the side of the road with a coolant temp warning. I did mine as preventative maintenance at about 80k as I was getting one of the codes and figured it wouldn't last another hot summer (jokes on me, summer '23 was crap...).

My car was mapped by a previous owner by Celtic Tuning down in Newquay and allegedly did 281hp on their dyno. Realistically it's probably more like the ~270hp you'd normally get out of an N52B30, but that's no bad thing- plenty of torque down low and when you hit 4000rpm you get a nice little shove in the back as the VANOS comes on song, at which point it builds up until the 7000rpm red line. Mine is also currently sat at an average of 29.7mpg during my ownership according to the OBC, and that's with lots of horrible Bristol City Centre traffic, and enthusiastic runs on B-roads. I've had mid-30's on motorway journeys even when 'making progress' and if you're really good it will nudge into the 40's...

Edited by Sofa on Friday 26th April 23:37

Griff43V8

Original Poster:

90 posts

11 months

Saturday 27th April
quotequote all
thanks guys for feedback smile

Presumably, when re mapping 125i they can concentrate less on emissions, tweak timing and fuelling beyond 130i OE too - That coupled to better flowing inlet and exhaust has to be good for 20bhp over 130i OE?

Wonder if VANOS can be s/w tweaked for better fuel / emissions too?

Would ideally like it hi torque and approaching 300bhp with a significant on cam feeling ramping up in the low 4k region.

The power figures should then replicate my Griff....just be 0.7 tons heavier! ..Reducing power from 300 to 211bhp / ton ..ouch! frown - That explains why they struggle to crack 6secs I guess. - Incidentally, the new MG4 X has same bhp/ton (425/ 2 ton) but is 3 secs to 60.... Torque however is 443 lb ft (c 212lb ft/ton) - 130i is c 230 (135ftlbs/ton) Griff c. 290ftlbs / ton again explaining difference in acceleration I guess - Streuth, that means the Griff has 37% more torque & BHP/ ton than mega MG4 X awd twin motor... So how come X is not slower to 60? X is c 3 secs and Griff c. 4.1...all down to awd?!

BM Waterpump cost is irksome at £500+ fitted, however if that is the biggest likely main mechanical component cost and is only once every 5 or 6 yrs, cant be bad smile

Dare I ask about timing chains and VANOS longevity?

Griff43V8

Original Poster:

90 posts

11 months

Saturday 27th April
quotequote all
anyone come across a Z4 type induction sound pipe to cabin mod for 125i?

Griff43V8

Original Poster:

90 posts

11 months

Saturday 27th April
quotequote all
anyone come across a Z4 type induction sound pipe to cabin mod for 125i?

Some Z4 notes here

Not sure how practical it is for 125i engine bay - was considering doing it electronically through a mixer amplifier into cabin speakers

I would emphasize that I havent even road tested a 125 to 130 spec yet, so induction sound may be good enough standard - the old M3 I tested was too much (suspect there wasnt an air filter, that invasive - cheapened car, as does, for me, a brash exhaust)

Creamy and melodious for my ancient ears is preferable - The Griff is going to be quite a shock after being laid up 16 yrs and driving electric last few yrs!!

Griff43V8

Original Poster:

90 posts

11 months

Saturday 27th April
quotequote all
anyone come across a Z4 type induction sound pipe to cabin mod for 125i?

Some Z4 notes here: https://www.zpost.com/forums/showthread.php?s=58ce...


Not sure how practical it is for 125i engine bay - was considering doing it electronically through a mixer amplifier into cabin speakers

I would emphasize that I havent even road tested a 125 to 130 spec yet (so, going by many Youtube clips), induction sound may be good enough standard - the old M3 I tested was too much (suspect there wasnt an air filter, that invasive - cheapened car, as does, for me, a brash exhaust)

Creamy and melodious for my ancient ears is preferable - The Griff is going to be quite a shock after being laid up 16 yrs and driving electric last few yrs!! - One of the few exceptions of a loud exhaust I love - most V8s can sound great

Court_S

12,997 posts

178 months

Sunday 28th April
quotequote all
BDS Motorsport have managed to get an N52 close to 300bhp but it’s quite expensive.

270 is a bit as far as you’ll see with just a remap. Induction kits for the 1 series are pretty limited…I have an Armaspeed carbon induction kit on my wife’s 330i which sounds good but not sure if it’s available for the 1 series.

The engine bay in the 125i / 130i is quite snug. Access in a Z4 is much better.

Edited by Court_S on Sunday 28th April 06:39

Griff43V8

Original Poster:

90 posts

11 months

Sunday 28th April
quotequote all
thanks - I wont go down the rabbit hole of chasing the last 10bhp at escalating cost - EVs have made that a thing of the past smile

Have u seen the new MG4 X Power reviews? If that follows the trends of halving in value within 3 yrs with 4 yrs left on the warranty.....

Court_S

12,997 posts

178 months

Sunday 28th April
quotequote all
Griff43V8 said:
thanks - I wont go down the rabbit hole of chasing the last 10bhp at escalating cost - EVs have made that a thing of the past smile

Have u seen the new MG4 X Power reviews? If that follows the trends of halving in value within 3 yrs with 4 yrs left on the warranty.....
Makes sense. It’s hard work with an N/A engine to extract power.

Agree re EV’s killing ICE cars when chasing performance. For me, there’s more to cars than figures.

Griff43V8

Original Poster:

90 posts

11 months

Sunday 28th April
quotequote all
Have pre cat Griff and Stag for the orchestra, hence looking at this engine smile

EVs make phenomenal daily drivers though - MG4 X would do nicely - even my Zoe Gt was just great smile