RE: BMW M135i: PH Fleet

Monday 11th December 2017

BMW M135i: PH Fleet

In which Dan ponders that age old question; how much power is too much power?



The most powerful new hot hatch you can buy right now is the Audi RS3. All 400hp of it. Undoubtedly that is a staggering amount of go for a hatchback, but then £44,300 is no modest figure, either. I mention this because after its final round of updates (or is it? More later...) my M135i is now producing almost exactly the same power as the RS3. 390hp, in fact, up from 320hp.


You'll know the score by now. Earlier this year I bought a 30,000-mile BMW M135i for £17,500 and, working with renowned BMW specialists Birds, have been upgrading it bit by bit. We wanted to get the thing handling properly before we turned our attention to the motor, so the first jobs were to upgrade the suspension with a spring and damper kit that was developed specifically for the M135i by Birds, and then replace the open differential with a Quaife LSD.

Now it's the turn of the engine. According to the good people at Birds, the 'N55' 3-litre turbocharged six-pot can be wound up to almost 400hp with just a remap. The wick can be turned up even further, of course, but that causes fairly significant issues. "We did push one of these engines beyond 400hp," says company founder Kevin Bird, "but we found that the ignition timing was being retarded at maximum torque rpm in the higher gears. If you kept the throttle pinned for more than ten seconds you could also see that the throttle was beginning to close, ultimately triggering limp mode. We determined that the detonation protection was being triggered, and clearly the thermodynamic and physical limits of the engine were being exceeded at the level of boost required for 400hp plus. To get more power we would have to either open up the engine, or provide additional external equipment to increase the detonation limit of the engine." In other words, you would have to spend an awful lot of money, which really isn't the point of this project.


What I really like about the remap is that the basic character of the engine is completely unchanged. It hasn't suddenly become a truculent, boosty thing; the sharp throttle response is still there, as is the strong bottom end and the energetic top. It feels much the same as before, but more so. Along with 390hp the engine now develops a rather mighty 420lb ft of torque and when you put your foot down in any one of the higher gears you really feel it pull through the mid range with a muscularity that wasn't there before. Beyond 5,000rpm there's also a frenetic edge to the delivery that makes the car feel so much more urgent in a straight line.

What it doesn't feel is over-engined. It isn't as though we've shoehorned an unnecessarily powerful motor into an inappropriately small car. Instead, the engine now feels very well matched to the rest of the - much improved - chassis and drivetrain, which is exactly how I like it. I'm sure there'll be some people out there who want 500hp or more from their M135is and I've no doubt it can be done if you're willing to open your wallet wide enough, but on this occasion we've set out to build a cohesive and well rounded car, not an explosively fast one.

What I haven't mentioned yet is that the M135i is now more powerful than the 370hp M2, as well as a whole lot torquier. I haven't had a chance to run a set of acceleration figures yet, but all signs point to this car now being faster than the pugnacious little M2. The Birds remap, by the way, costs £2,249.

And that was supposed to be the end of our M135i project. But then, a few days ago, an email dropped in from Birds asking if I would fancy upgrading the car's brakes early in the new year. Well, it'd be daft not to, wouldn't it? The standard brakes have been just fine on the road, but I know from past experience that they aren't really up to sustained circuit work. The M135i will be around for a little longer than expected, then. Soon, it should stop just as well as it goes.


FACT SHEET
Car
: BMW M125i
Run by: Dan Prosser
Bought: July 2017
Mileage: 36,100 total, 2,800 this month
Purchase price: £17,500
Last month at a glance: Remap boosts power to almost 400hp

Previous reports:
'You could get an M135i for that' - so we have!
Shockingly good improvement with new suspension fitted
Dan gets a dose of LSD and loves the effects

Author
Discussion

HotRacer84

Original Poster:

1 posts

9 months

Sunday 10th December 2017
quotequote all
Sounds brilliant. This is making the m2 upgrade from my m135i seem less tempting! Would be nice to hear a bit more of a description about how the overall feel of the car has changed though.

MDMA .

3,881 posts

29 months

Sunday 10th December 2017
quotequote all
£2249 for a remap? Er, no thanks.

nickfrog

8,457 posts

145 months

Sunday 10th December 2017
quotequote all
Given how much publicity Birds are getting, I assume they only charged a fraction of that as this is extremely poor VFM indeed.

Alucidnation

8,088 posts

98 months

Sunday 10th December 2017
quotequote all
Quite.

Marketing that’s as subtle as a brick.

And over 2k for a remap?

Lol.

Escort3500

2,849 posts

73 months

Sunday 10th December 2017
quotequote all
So are you going to tell us how much you actually paid for the remap Dan? smile
Advertisement

thelawnet1

1,520 posts

83 months

Sunday 10th December 2017
quotequote all
So how is that better than this for 1/4 of the price?

https://www.aetmotorsportshop.co.uk/products/burge...

GregK2

1,056 posts

74 months

Sunday 10th December 2017
quotequote all
thelawnet1 said:
So how is that better than this for 1/4 of the price?

https://www.aetmotorsportshop.co.uk/products/burge...
I can see why some might opt against a JB4. A more fair comparison might be:

https://www.evolveautomotive.com/evolve-ecu-remap-...


Perpetrator

52 posts

124 months

Monday 11th December 2017
quotequote all
Golf R remapped for £500 to 370/370 - over 2 grand is a joke!

Bet its nippy now though to say the least with 420lb/ft

Impressive figures.

Esceptico

1,290 posts

37 months

Monday 11th December 2017
quotequote all
How come the mapping costs so much?

The problem I find with my M135i is not that it doesn't have enough power, it is using that power without spinning the wheels. If it is anything but bone dry and hot (and you are driving in a straight line) it is too easy to spin the wheels.

pimpchez

848 posts

111 months

Monday 11th December 2017
quotequote all
Alucidnation said:
Quite.

Marketing that’s as subtle as a brick.

And over 2k for a remap?

Lol.
I agree

What a contradiction if i ever saw one from the author , wants cheap mods but spends "rod job" money on a remap alone....

sixpistons

140 posts

51 months

Monday 11th December 2017
quotequote all
Seems a lot of money to me for a remap. One thing this car does not really need is more power - where in the UK can you actually deploy 400bhp for more than a couple of seconds? The chassis mods sound much more worthwhile

Sheets Tabuer

14,431 posts

143 months

Monday 11th December 2017
quotequote all
sixpistons said:
Seems a lot of money to me for a remap. One thing this car does not really need is more power - where in the UK can you actually deploy 400bhp for more than a couple of seconds? The chassis mods sound much more worthwhile
He says in the last paragraph it's for the track.

The car is more than powerful enough for shopping in it's original form.

kritter86

116 posts

63 months

Monday 11th December 2017
quotequote all
I'm sure I saw a youtube video of a 74 year old bloke who made 560 BHP from his.

This is just as much advert as an article. Surprised it doesn't come with a discount code on the bottom.

givablondabone

2,402 posts

83 months

Monday 11th December 2017
quotequote all
Anyone paying that much for a remap must have t**t written across their forehead!

I mean, seriously?


Lotusgav

15 posts

87 months

Monday 11th December 2017
quotequote all
On a slightly different note my old man had a 996 turbo once which, iirc, was about 420 hp. That was 90k at the time. So 40k for the RS3 doesn't sound bad to me. Probably got a nicer interior!

Maybe an interesting comparison test?

givablondabone

2,402 posts

83 months

Monday 11th December 2017
quotequote all
Lotusgav said:
On a slightly different note my old man had a 996 turbo once which, iirc, was about 420 hp. That was 90k at the time. So 40k for the RS3 doesn't sound bad to me. Probably got a nicer interior!

Maybe an interesting comparison test?
I reckon driving the RS3 quickly would be easier for most but Ill take your dad's 996 anyday thanks wink

Limpet

2,737 posts

89 months

Monday 11th December 2017
quotequote all
Suspension mods and LSD would be very tempting. The £2,200 remap (that's a typo, right?) less so.

strike4A

52 posts

121 months

Monday 11th December 2017
quotequote all
N55 engine ecu can now be flashed via OBDII - should be sub £1k at best

kbee540

136 posts

136 months

Monday 11th December 2017
quotequote all
DMS remapped my old M135i to c.400hp for just £600. Birds is by all accounts a fine company, but £2k for a remap is taking the p.

toby-w8jtf

55 posts

20 months

Monday 11th December 2017
quotequote all
The birds remap is just daylight robbery, its probably just a generic map too.

My friend recently had his M135i remapped at Unicorn Motor Developments for about £600, the mapper spent the entire day live logging and custom mapping it and even gave him switchable maps including crackle map etc so 2k+ is absolutely absurd

One thing to note is that a uprated forge boost pipe is needed at this level of power as it'll either be sucked almost flat or it'll split!

Really wished I'd bought one of these myself instead of my Golf R.... So much more fun to drive!