2008 BMW 135i: Do it. Do it now!

The BMW engineers are certainly capable. Please ask the factory why they didn't do it. If there is no answer then perhaps it is marketing. But that doesn't ring true. The may well be reliability concerns.

"The BMW engineers are certainly capable...why they didn't do it...perhaps it is marketing."

Audi's dynamics engineer spoke out about that in the EVO and TopGear reviews of the Audi S5. He said the marketing [monkeys] forced him to setup the S5 with the traditional Audi understeery handling.

I'm with epbrown on this one. The Bavarians didn't want the 135i running up on the M3. Bad enough in the real world, where few drivers can match nagazine test-track numbers, that the car runs so close to the Motorsport.

I'm still interested in seeing if this gets past dealers when it goes in for maintenance. I'm considering buying a used 135 or 335, and I'd definitely go for this if it doesn't blow the warranty, especially since I live in the LA area.

I'd be interested to see what it does to the gas mileage over time.

If driven sanely, it should increase the mileage. If driven like some guys from Edmunds are on it, it will only get worse. You guys rag out cars because there's no personal penalty for doing so.

Can't wait to see what happens next time you bring it to the dealer...

I have always wondered if these power-adding tunes put the catalytic converter under added stress and make it likely to fail sooner.

Evos ran rich from the factory and tuners would often lean out the mixture as they made power. Is running right easier on the cat somehow? Is leaning the mixture going to do it damage?

nice, like i said all along... i'd get exhaust and reflash and call it a day. this is WHY the 135i is the best performance deal you can get today. the fastest one i know of runs 11's in the 1/4 mile with the use of race gas. on 91 octane, it's easily faster than the M3 in a straight line. (you still can't touch the handling of the M3, though)

as for the catalytic converter, running too rich will kill it. running lean shouldn't be a problem.

Random thought: if you could make a car mod that was undetectable by a dealer but made a significant change to performance, how does that affect resale? Would you want to buy a car that could have been significantly modified but you would have no idea? I know the odds are overwhelmingly against that ever happening, at least with this particular mod, but it does pose an interesting question.

Nice, but you may want to consider changing the engine oil a bit more often. The more aggressive tuning may result in more rapid degradation of the engine oil.

Huyracing, you know that the M3 suspension parts (front wishbones and tension rods, rear guide rods, upper links, bushings) are direct bolt-on for the 135i right?

I'm pretty sure stuff like this voids your warranty. no thanks.

bimmer13,

So you mean somebody could build a mini-M3? Have people done it, and what were the results?

Just for reference, most modern cars have what is called a cat protection mode whereby measured cat temps (either using the O2 sensor, or other means) can trigger a special fueling mode. This fueling mode results is substantial extra fuel being dumped (usually under high load and high engine speeds) to cool the catalytic converter. You can see this happen on the various supercharged Caddys, or even a Civic Si if you make several quick acceleration passes in succession.

So, under full throttle and short duration, running somewhat richer than optimal actually helps the cat live longer (EGT's go down and they are the primary driver of cat temps in that situation). Doing so at part throttle for long periods of time would tend to create higher temps than normal because as mentioned earlier, the cat must do its job and attempt to catalyze the excess hydrocarbons.

I hope I'm being clear, you've got different dominant factors under different conditions.

wshuff, yes you can build a mini-M3. there are plenty of modded 135i's running around and there are a few comparisons with the M3. from what I've read, its still slower than the M3 around a track.

bimmer13, yes i do know the suspension swaps over, but it is only part of the equation in matching the M3's handling goodness. not saying its not possible, but i haven't seen it yet.

We need full disclosure!

When the first reviews came our for the 335/135 - Edmunds raved about the power delivery of the 3 liter turbo, and how BMW had built one their best engine ever (or something to that effect). And even Wards Auto chimed in with a "Best Engine" award for the 135 in the 2009 ratings.

But along this came reports from user blogs about how the BMW N54 power-plant did have a turbo lag issue after some software upgrade - so god knows who was telling the truth. Never heard anything on that from Edmunds...

So - here goes the question. Does BMW build a special vehicle for Edmunds or, say Auto Ward to test? Or does BMW marketing do a good job convincing the journos (with a taste for some beluga and the high life, on modest salaries) to understate deficiencies. One will never know.

Because the comment here "the DME reflash proved its worth. There's a whole new midrange. There's no turbo lag" above does confirm one thing - the midrange was not all that was it was made to be, and there IS turbo lag.

Or is it DME marketing now that is working its magic.

The problem that arises is this - with all the noise in the measurement, who do you trust???

Jatbeni -

I think you are drinking some kool-aid.

If you had driven a 335 when they first came out, you'd know that it had no appreciable turbo lag. It wasn't a naturally aspirated engine either, but there was no "build-up and rush". And the engine kicked hard at 1500 rpms.

The software reflash BMW came out with supposedly gave some turbo lag. Owners complained. They came out with a new software program that once again gave the engine back its character. I don't know if edmunds ever got the first flash.

As for the mid-range - Getting a "whole new mid-range" doesn't mean the original was not all it was made out to be. IMHO, the stock N54 mid-range didn't FEEL all that powerful because it's an incredibly smooth inline six engine and the torque comes on so early. In most cars, a good mid-range is represented by feeling peak torque hit around 3000-4500 rpms. Not so in this car.

With the DME reflash, they are hitting peak torque in the mid-range now....so there is an actual rush.

I guess the answer to your question is: Are you actually able to analyze a situation?

Joe

Almost forgot to ask Magrath, what do you mean by unreasonable power in the GSR? First of all, is there any such thing as unreasonable power? And second, the EvoX is kinda flat over 5000 rpm on power (tends to be near peak by 5500 rpm or so and not build much) so the comment was confusing. Maybe you meant the throttle response is not linearly linked to the power? Anyways, I know its off-topic kinda, but I was curious. If its the throttle reponse, that can be cured though.

"There's a whole new midrange."

"Why they didn't do this from the factory is beyond me. It's as driveable as it ever was before except now there's more power everywhere."

These quotes reminds me of my good friend and his 07 Civic Si sedan. He installed the usual I/H/E, although that was an improvement, it still seemed to be missing something.

I then broght to his attention the Hondata reflash. It wasnt long until he sent his ECU to them for the application. The Hondata reflash changed the car completely. Although there was a sizeable gain in peak power, the low-midrange was in a whole different league as there was a SIGNIFICANT gain. I believe the dyno sheet with the same mods on Hondata site says a 30ftlb gain in the midrange! Thats exceptional for a normally aspirated small displacement 4 cylinder thats already highly tuned from the factory.

Though Church123's comments are very interesting,

Does the retuned 135 still pass CA emissions testing?

As for "unreasonable power", anything that stresses the drive train into plastic deformation (drive/half shafts start twisting like rubber bands, and don't unwind) is unreasonable.