- Post is under moderationDynamic Additions #BMW-F32
We take a drive in the #BMW-F32-Birds modified #BMW-435i-F32 to see how small changes can make a big difference. While the #BMW-435i-F32-Birds makes a good looking junior GT, Birds thought that it needed some additional driver appeal. We sample its demonstrator to find out if it’s been successful Words: Bob Harper Photography: Max Earey
Ensuring there’s enough differentiation between models must be one of the most delicate of tightropes that a car manufacturer has to walk especially as each new model is expected to be more powerful, faster, more economical and demonstrably better than the machine it replaces. Logic must dictate that there will come a point when cars simply can’t get any quicker but we’ll have to wait for a few more years before that eventuality.
No, for the time being what we need to look at is the way that #BMW has to ensure that its new XYZ is better than the old generation XYZ but isn’t so much better that it treads on the toes of the inevitable M XYZ. A case in point is the F32 435i. New name aside this is obviously effectively a 335i Coupé and its onpaper stats are pretty impressive: 3.0-litre turbocharged straight-six developing 306hp and 295lb ft of torque. Good enough for a 5.4-second 0-62mph time with the six-speed manual (5.1secs if you opt for the eight-speed auto), and there’s no doubt that the vast majority of machines will be thus equipped.
These stats really aren’t very far off previous generation M3 figures and there’s no doubt that with its wide spread of torque the 435i will be more or less as fast as an E92 M3 in most driving situations. Or until the road becomes a little bit more demanding, requiring a little bit more finesse than the 435i seems to possess. While the Four is great piece of kit it’s perhaps gone a little too far in the direction of being a junior GT rather than a sports coupé – a little bit too soft in its reactions for the really keen driver. For the vast majority of us we’d be more than happy with a 435i straight-out-of-the-box but for those looking for a little bit more involvement, a little bit more feedback and drama, then there’s certainly room for some improvement. And who better to supply that than Birds? Kevin Bird has been fettling BMWs for probably more years than he cares to remember and in recent times we’ve been hugely impressed with the changes he’s wrought to a diverse range of machines – his 130i was a revelation on just how devastatingly good the hot hatch could be and the transformation he managed on the E89 Z4 had to be experienced to be believed.
Naturally enough he had plenty to say about the 435i he purchased as his company’s new demonstrator: “The 435i seems to have had a character bypass. Granted, it’s quite a pretty car with plenty of new visual signatures but the driving dynamics, which we are primarily interested in, are buried under a layer of electronic management systems. Keep an eye on the speedo, and it’s obviously a fast car, but the seat of your pants and the other driver interfaces – steering, pedals and the like – seem to be disguised under a layer of, err, can’t really say for sure.
“It feels like an excessively mature version of the previous 335i, but maturity seems to mean bigger, fatter, heavier, and boring in this case. Testing of the standard car went like this. Drive, foot to the floor, and it seemed there were immense levels of mechanical grip. Unable to get anywhere near the limits on the road. Okay. Let’s switch some of the gadgets off. Traction control first. Nope, no wheelspin or loss of grip found. Try harder, even in the wet, and no real signs of big traction loss. Maybe, by accident, BMW has bunged the M-Performance diff in as a free-ofcharge favour? After a few miles, the truth becomes clear. There is some traction management in here. The first three gears don’t appear to be authorised to accept the full power of the engine. Big brother is at work, managing the whole show.
“Now you can tell the throttle is blunted, but there is a Sport button, which sharpens the throttle response, so we’d better try that. Much better, now you feel like control over the engine is yours. Bad news, you can’t have throttle response and traction control off. It’s a struggle to find how to enjoy this car. Best solution is to switch the DSC fully off and give it everything and see what happens? Whoa! It gets massively untidy when you do find the limit. Don’t try that again. There seems to be no finesse, or the ability to hold the slide on power, or anything pleasurable like that.” We think it’s safe to say he wasn’t particularly impressed.
So, what were Kevin’s solutions to what he sees as the car’s dynamic shortcomings? “The lack of a limited-slip differential is an obvious shortcoming but given the levels of hidden traction management, we want to understand the handling balance of the car before giving it more traction. Anti-roll bars first, then. Changing the roll stiffness bias toward the rear increases the overall roll stiffness, allowing the front end to grip more in turns and quelling understeer. The front end feels immediately more responsive and accurate but, as expected, there is a loss of traction at the rear but not enough to worry about at this stage. The car seems to have gained a chunk of character and poise, and can be more accurately steered,” Kevin told us.
Birds has worked wonders with the suspension on other models we’ve sampled so it should come as no surprise that the setup on the 435i has come in for some attention. After Kevin’s own impressions and then some input from chassis guru Rhoddy Harvey- Bailey prototype springs were duly ordered. According to Kevin: “The spring rate changes make the car feel supple and balanced, and compliment the significant rear roll bar increase.”
Naturally enough damper changes were also required, and as Kevin’s not a fan of the OEM adjustable setup he spec’d the fixed dampers on his demo knowing they were going to be changed anyway. Kevin takes up the story once more: “Tuning the dampers is a matter for experts only. Having been involved in BMW chassis tuning for 30 years, mostly relying on other people’s work, the process is still completely alien. Watching the experts assess a damper dyno curve, draw lines on it, and then hand it back to the renowned Bilstein engineers is impossible to follow. But the results aren’t. As soon as you start driving the car, the differences are immediately tangible, in a positive way, of course. Several road tests later, and after a few calls to major tyre manufacturers’ engineers, we know we have a result. What’s more, we have arrived at a setting that can be used with 20-inch wheels and tyres – something that eluded us with the E92 development.”
With the suspension sorted Kevin was able to slot a Quaife limited-slip diff in to the car and start to enjoy its new-found abilities. “The car is starting to feel like a driving machine. The reactions of the chassis to inputs, both from the driver and the road, are measurable and repeatable. The car doesn’t misbehave on the limit and you can control the car on the throttle and the steering. Isn’t this the way it should be?” he argues.
The extent of Birds’ work on the 435i doesn’t stop there but what’s been discussed so far gives us more than enough to get our teeth into to start with and as we depart Birds’ Iver HQ we have two days of varied driving to put the car through its paces. We could just take it for a good blast along one of our favourite stretches of back road but that would only really show up one side of its character – if it’s to be a thoroughly convincing conversion it must also cope with commuting and a bit of motorway jogging, too. It doesn’t take too long to realise that there’s real depth to the suspension upgrade – it feels pretty supple on the motorway, absorbing dips and crests and expansion joints without breaking into a sweat.
Compared to our M235i longtermer we’d say it’s firmer than the Comfort setting yet much better damped than when in Sport. Around town it also works very well and after a while behind the wheel we really don’t notice the suspension – sure-fire proof that it’s comfortable enough for everyday use. Bigger potholes will send a shudder through the car but, overall, for a machine of this size to be able to run 20-inch wheels without ruining the ride is quite an achievement.
The following day we have a rendezvous with snapper Earey in the wilds of Northamptonshire to put the 435i through its paces on some proper roads and the run up there once again demonstrates how Birds’ work hasn’t detracted from the car’s mile-munching abilities. As well as the suspension upgrades there’s also a new exhaust system and while Kevin reckons this is the quieter of the two prototype systems he has test fitted it can be a little loud here and there. It’s not a drone per se and when on a constant throttle at 70-80mph you don’t notice it but it does become significantly louder when you put your foot down at those speeds. On the back roads it sounds superb so it would probably come down to personal preference as to whether this upgrade would suit you.
While we’re yet to give the car a through pasting it’s become obvious from the motorway and town stints that Birds has also given some thought to the gear change on the car. Kevin elucidates: “The clutch and gear change on the standard car are frankly appalling. The clutch pedal operation can be likened to stepping into a blancmange, with zero pedal reaction, no indication whatsoever as to whether the clutch is engaged and disengaged. It makes you drive like a learner, crunching gears both on up and downshifts. Ably assisted by a gear lever mechanism that is long in throw, and changes into even gears have your elbow in contact with the central armrest. Both of these items receive attention, and considerable improvement. Small issues like these are what really make a properly tuned car.”
Upgrades here include a short-shift kit that virtually halves the throw on the gear lever and a clever modification to the clutch pedal that removes the over-servoed effect. In our M235i it can be difficult to be smooth when changing gear, especially from first to second as there’s not a lot of feel as to where the biting point is. However, changes in the Birds’ machine can be completed lurch-free, which is surely how it should be.
It should come as no surprise that this 435i has also had a power upgrade too, and while Kevin wouldn’t recommend it on a 435i without the chassis upgrades, this fettled example can now make use of some more power. It’s not as easy as it used to be, though, and Kevin says that, so far, the latest BMW engine management cannot be modified and attempts to generate significant power increases often fail with engine management warning lights the norm. As far as the 435i is concerned, 362hp is the limit. What Kevin has also done, though, is a modification to the accelerator to allow decent throttle response – equivalent to the Sport mode when still in Comfort – and this will still allow the traction to be fully switched off at the same time.
Hammering up the B660 for our rendezvous with our photographer gives us a real opportunity to feel the whole package gel together and by the time we meet up there’s a Cheshire cat-sized grin etched on our faces – this is a huge amount of fun to punt along. There’s power aplenty and while it doesn’t matter hugely which ratio you’re in – such is the spread of torque – you do find yourself swapping cogs just for the fun of it as the upgraded interfaces encourage you to do so.
It’s the chassis that really impresses though and it exhibits just about every trait that we like to see in a car. There’s enough suppleness in the setup to allow for some body roll but it’s beautifully controlled, never lurching in its transitions and even when really committed mid-corner changes in surfaces or encountering a dip halfway round a bend don’t upset its balance. The more you hoon along the more confidence you have that the car will simply follow your instructions and respond to inputs in the way it should. It transmits those 362 horses to the Tarmac so well that you slingshot from one corner to the next safe in the knowledge that the upgraded stoppers will wash off speed with no drama or fuss. We’ve not mentioned these before but it’s an Alcon setup that offers awesome retardation and a better feel to the pedal that becomes the perfect pivot for some heel and toeing.
You couldn’t really ask for more from a complete conversion but, as with all things in life, quality doesn’t come particularly cheap. Carry out all the upgrades that are fitted to this machine to a new 435i – power, anti-roll bars, springs, dampers, LSD, brakes, wheels, tyres, short-shift, clutch modification, brakes and exhaust – and you’re knocking on the door of the price of a new M3 and M4. Dynamically it doesn’t honestly feel like it’s that far away in terms of its chassis but it doesn’t feel as quick either. No, the joy of the Birds upgrades are that you can cherry-pick the ones that you want, the ones that will suit your driving style and the type of roads you drive on. What is in no doubt is that Birds has brought about a huge number of changes to this machine and all of them for the better. It really does bridge the gap between the #BMW-435i and the M4 and transforms it from a gentleman’s GT into a rip-roaring performance coupé that’s a hell of a lot of fun to drive. Mission accomplished we’d say.
CONTACT: Birds Tel: 01753 657444 Web: www. #Birdsauto .com
Birds component prices
HARTGE ENGINE ECU 362HP: £2433.39
B4 ANTI-ROLL BAR KIT: £841.75
QUAIFE BMW LSD CONVERSION: £1562.00
B4 SPORT SUSPENSION: £1528.37
SHORT GEARSHIFT: £411.13
CLUTCH PEDAL WEIGHT MODIFICATION: £81.60
EXCHANGE QUAIFE BMW FINAL DRIVE: £1667.00
SPORT SUSPENSION SPRINGS: £600.04
ALCON AE BRAKE KIT FRONT, 365X32: £2797.40
ALCON AE BRAKE KIT REAR, 343X28: £2325.83
B4 REAR SILENCER, FOUR OUTLETS: £1593.91
HARTGE 20-INCH WHEEL & TYRES SET: £3961.00
Please note: All prices quoted within this panel refer to components fitted individually not as part of a B4 Dynamic Package. Prices include parts and labour but not VAT.
Birds B4 Package prices
B4-3.5 COMPLETE CONVERSION: £6,464.65
Hartge engine ECU 362hp, B4 anti-roll bar kit, Quaife
BMW LSD conversion, B4 Sport suspension, short
gearshift, clutch pedal weight modification
B4 DYNAMICS PACKAGE 1 £2,330.64
B4 anti-roll bar kit, Exchange Quaife BMW Final Drive
B4 DYNAMICS PACKAGE 2: £2,903.31
B4 anti-roll bar kit, Sport suspension springs, Exchange
Quaife BMW Final Drive
B4 DYNAMICS PACKAGE 3: £3,859.01
Exchange Quaife BMW Final Drive, B4 Sport suspension,
B4 anti-roll bar kit
Alcon AE brake kit front, 365x32, Alcon AE brake kit rear,
B4 rear silencer, four outlets
Please note: All prices quoted with this panel include labour and a discount on parts that only applies if a Birds Dynamic Package is ordered. VAT is not included in these prices either. See the separate panel for individual costs of specific components.
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