BMW 640i - "35i" engine?

[joropug]

Looking at a couple of 640i's, am I right in thinking they actually have the N55 engine i.e. 35i in most models?

Any feedback from how it performs in this car? It's a Gran Coupe so not light obviously. Reliability a concern?

[Pistonheader101]

Good cars maintenance can be expensive so find a good independent

[HelldogBE]

The B58 never made it to the F-series 5- & 6-series platform. Any reference to a 640i with the B58 is the current G-series Gran Turismo.

This is a great guide on the N55:
https://bmwtuning.co/n55-common-problems/#:~:text=...

The B58 has a great rep for tuning, but if you're only going stage one I don't see what's wrong with the N55. It sounds terrific with an M Performance Exhaust!

[joropug]

Well I think a stage 1 remap would be on the cards so that is good to know. Interestingly though, there might be a stumbling block, gearbox.

The wikipedia page for the 6 Series suggests the 640i gearbox isn't rated to the same level of torque as the 640d version - in fact it's pretty much on it's limit.

Stock power is 315bhp, 450nm

8-speed ZF 8HP45Z automatic (640i) (Max torque 450nm)
8-speed ZF 8HP70Z automatic (640d / 650i) (Max torque 700nm)

That aside though I'm torn between a 640i Coupe or Gran Coupe and an Audi S5 Coupe or Sportback - I think the Audi is the more modern car but is a bit dearer. Both have a ZF8 but the

8-speed ZF 8HP55 automatic (S5 B9) (Max Torque 550nm)

There seems to be plenty of tuned 640is so it's probably ok but would be an expensive mistake to do the gearbox in.

[HelldogBE]

I've heard very little of ZF8's going wrong but it does happen. If you're not towing or doing race starts all the time and actually service the box they should be pretty robust. You might find more info in dedicated 1/2-series forums as loads of the M135I's have been tuned. The ZF box is the least worrying thing about a car like this IMO. (For example adaptive dampers cost an arm and a leg for the F-series compared to the G, it's 4000€ for 4 shocks for my car without labor. I'd also avoid Xdrive if you want peace of mind.)

xHP offers DIY smartphone flashing of the box which offers increased pressure on the wet clutches engaging the gears, along with improved shift mapping.

If you're doubting between an S5 and a 640i, I suggest you go on a test drive. The 6-series is a big and heavy car and more of a cruiser. I drive an F11 530D Xdrive (admittedly even a tad heavier at over 2 tonnes) and if you like hammering B-roads it starts feeling too wide to throw around very quickly. The Audi is definitely a size below and what you'll gain in agility you'll probably lose in comfort. A 340i is the direct competitor and has the same ZF8hp50 (which is a revised/newer version of the hp45).

https://blog.fcpeuro.com/zf-8-speed-transmission-g...

[jason61c]

I’d go for the 640d. It’s. A much quicker car in the real world, great on fuel etc also