How xHP changes the logic of 8HP

How xHP changes the logic of 8HP

The 8HP is an extremely competent transmission, how do you make that even better?



Last week (Jan 21st 19), we released our first 8-speed Transmission (ZF8HP) setups for F-Series BMW. The first cars supported were M135i/M235i/335i/435i and 535i variants. All are equipped with the N55 3.0 straight-six turbo-engine and ZF 8HP45 transmission. This is just the first release, and of course, we will be working our way through most 8-speed cars, just like we did with the 6-speed E-Series BMW. Before release, many people asked us: "What the hell do you want to improve with the 8-speed?“ :)

Well, the 8-speed is a highly competent transmission, achieving virtually anything you can imagine. From smooth-as-silk yet reasonably fast shifts to totally instant and rocket-fast. The shifts with a sportive touch. So, yes...doing maps for it, which we judged to be better by ourselves, took work. We spent over six months just with Re-Mapping in the car. We accumulated over 10,000 kilometers (approx. 6,200 miles) on our F31 test car while having the laptop on the passenger seat. 

Why did it take so long? Our standard is not to remove some torque limiters or raise line pressure a bit. Our bar is to improve your driving experience daily with your car. That’s what xHP stood for in the past, and that’s what we always want to achieve when doing setups. While removing a torque limit or helping the trans to hold a bit more power may be necessary for the minority of people who run double the stock power on their car, this does not help anything for people with stock power cars, nor will it get you more fun when running a vehicle with a bit more power than stock. It gets you a better feeling that you did the right thing to prolong your transmission life when running an engine tune, but that won't make you smile every day.

So, what do we do with our maps? The answer is simple: the way is complicated: We not only "tune" the transmission, we change the rules, how it behaves, and how it reacts to driver inputs. That’s where the DEC-Switch comes into play. The majority of F-Series cars come equipped with it. DEC stands for "Driving Experience Switch" and lets you adjust your car behavior from the driver’s seat on the fly. The settings are Eco-Pro, Comfort, Sport, and Sport+. So unlike in most E-Series 6-Speed cars, where the transmission had a fixed map set for D-Mode, S-Mode, and M-Mode, we can now combine those modes in the F-Series cars with the four positions of the DEC switch. This gives you a total of 12 operating modes, which you can access instantly from your driver’s seat.

Just like you aren't in the same mood every day, your car does not have to be the same every day. It can run full economy style on your commute to work in traffic-jam while simultaneously being a total beast with rocket-fast shifts and intense throttle-blipping on downshifts just with the flip of a button. That is an excellent tool made by BMW so that people can adjust their cars to their liking. But now starts the "bad" news: BMWs are made for a wide-spread of people/target groups, and yeah...they do make compromises, even if all options are at hand. In general, only their M-Cars get the whole potato. Everything else gets restricted here and there. This means you don't get the last bit of performance on a lower model, even if the transmission could do it. Or they restrict the number of modes you can access through the DEC because the marketing department says: "No, that’s too extreme for that target group.“ 

So let's explain it with an example: The 335i (same goes for M135i and M235i) accesses the same transmission mode when putting the gear-lever in S or when setting the DEC to "Sport" but leaving the gear lever in D. The trans is still "slow" in both modes but you get a bit higher shift-points. That’s not so exciting at all. Another example is the manual mode: No matter what you have set with the DEC, it will constantly shift to the fast way and rough. Some may like it, but it restricts what the system can do. 

Our Stage 2 calibration follows a simple rule: The gear lever changes the Shift-Points, while the DEC changes your Shift-Speed. You can combine it freely and make full use of what the transmission can do rather than what the marketing department thought you should be able to do. That’s how BMW does it in their M-Cars, and that’s how we think it should be. So now that all modes are accessible, what is that good for?

Answer: You now have three different shift programs in every operating mode. For instance, combining average daily-drive shift points with rocket-fast shifts creates a pretty awesome experience. You can feel all the torque the N55 produces in the lower to mid-range, while the shifts are so fast you can't even notice any lag between gears. On top, the trans makes little bangs through the exhaust on every gear change. Or you can now access the fastest shifts possible in S-Mode with full auto-operation and do not have to use M-Mode for that. Last but not least, you can also run your transmission in full manual mode but don't need to get your head jolted at each shift. Just use M+Comfort, and the trans will shift reasonably fast but very smoothly.

Hundreds of other minor changes will make the trans a bit more driver-oriented and not so much economy-focused. It is accessing 8th Gear later in D mode (that lugs the N55 a bit) or showing you the actual gear always on the Dash, even in normal D-Mode. It's too much to list and sometimes a bit hard to explain without going into full detail of the trans logic, but in general, our setups are generated through driving, driving, driving, and not just by drawing lines or raising values at the computer.

The Stage 3 file builds on top of that but makes S combined with the Sport+ setting ready for roll-racing and the racetrack. As soon as you engage this mode, the trans will keep your RPMs above 4,000 and won't upshift below 6,500 RPM. This is especially useful when you want maximum acceleration without having to think of the right gear by yourself. This mode can also be used on the Race-Track. It will shift just like a race driver with a stick would do it. Hold gears until the upper RPM range and aggressively blip down by itself when braking into corners.

You don't like all that? Do you think BMW already made it perfect for you, but you still need to get rid of the torque limiters in the 3rd and 6th gear so your engine tune can fully deliver? Then the Stage 1 is the right one for you. It keeps stock behavior in all modes but raises line pressure for high-power cars and sets your torque limits to > 1,000 Nm (which Stages 2 and 3 also do).

xHP customers can always choose between all 3 Maps. A Map change is only 40 seconds away!