Third Ride. More Impressions.

[Marcoose]

Hey, everybody. Happy owner here.

This 3rd ride, Part A and Part B, was to test the xHP flash. My complaint was that my expectation of how quickly a DCT should downshift in high RPMs was not being met. It's my first DCT car. I really thought it was instantaneous. I'm very quick at manual rev matching and toe-heel braking. On the Fireblade too (minus toe-heel, duh.) I found very disconcerting and disappointing the half second (or longer) lunging between 4th and 3rd, and 3rd and 2nd. So I was sent on the way of xHP.

The xHP installation was a 5 out of 10. It could've been better. Licence, packet, dongle and battery charger was around US$800. Ouch.

I rode California Highway 35. I know this road very well. Clean tarmac, clear viz, temps in the high 50s to low 60s. Part A of the ride was with xHP's factory packet. Yes, a big improvement. Part B was with a fellow member's personal tweaked packet. (That sounds super creepy. LOL) I don't know if the member wants to be singled out, but you know who you are, and I am very thankful. I owe you one. I felt a marginal improvement from the factory packet, and any improvement is worth keeping.

The DCT blips louder, seemingly faster, and the gears shift quicker. The car still lunges, but not as much. A massive improvement. Worth US$800, yessir. I found that, like with the Fireblade, downshifting whilst (feather) braking is much smoother. I'm training myself on LFB, so there's that.

My two major disappointments, massive understeering and lazy downshifting, are now solved. I thought I was going to feel the lack of a proper mechanical LSD, but so far, at least at the speeds I drive in the streets, the computerised diff is just fine. Time will tell. The next performance mod is a bespoke LFB pedal. The stock pedal position gives me massive foot/ankle/leg pain. That is serious lazy design on the part of BMW. The Subaru Impreza has better pedals.

Time to go. There's a long-legged young lady that wants cool air thru her red locks ... and I shall oblige.

Cheers,

Marc

 

[R.E92]

Good to hear everything went OK.

If you're in search of even better shifts the next step would be an engine tune. With the DCT box the gearshifts are a largely dependent on the DME(Digital Motor Electronics). The DME continuously reports a modelled torque value to the TCU(Transmission Control Unit), when a gearshift is requested by the driver the TCU will send a target torque value that it wants the engine to produce, the TCU will then change gear and the request for reduced torque will be removed.

If you are on the stock engine tune then things will be pretty good already. Problems only really tend to arise when using tunes. A JB4 unit is bad news for the DCT but even the "OTS" maps from the likes of MHD can cause problems as they aren't truly optimised for the DCT.
If you aren't the first owner of the car it might be worth checking that the previous owner hasn't left a JB4 installed (things like a gauge sweep on startup are a give-away). It's a bit harder to check if an ECU tune has been installed other than noticing the increased power.

The 35is produces a decent amount of power already but if you ever wanted to do an engine tune let me know. You can skip the hassle of buying premade maps and I'll send you my own engine tune.

 

[Marcoose]

Hi there, Rich. Thanks again for the help.

I don’t need more power, much less top end speed. This E89 is strictly for GT-ing in style in northern California. But if the urge to put down some performance arises, which happens, then performance is a must. In this region, performance above 60 mph is a waste.

If you have ideas to tune the engine for better throttle responsiveness and even quicker downshifting while performance driving, yes please, do tell.

 

[R.E92]

Certainly easy improvements to be made with throttle response. BMW has the throttle response dampened down quite significantly on purpose but this can be tweaked with an engine tune. There's no right answer with throttle dampening, they set the values quite high for the Z4, the same values that are used in the E9x 3 series, this makes for a more relaxed drive and flattens out unintended movements of the foot due to uneven road surfaces. Some people like to copy the values that BMW implemented in the 1M which is what I run in my cars, this is certainly much more direct but not to everyone's liking.

I can't comment on downshifts. I've never felt them to be slow but my car has never spent much time with the stock tune so that could be why. One thing to keep in mind with shift speed is that you can't rely on the tacho. The speed at which the tacho moves is rate limited in a similar way to how the throttle pedal is to make it move in a smoother manner, it's not a true reflection of actual engine speed, rather a rolling average. The tacho on M cars moves a lot faster and some people on bimmerpost have spent time coding their normal E9x tacho to move like the M3 one. It's not something that interests me so I never tried it.

Flashing the DME would be similar to the TCU is that you would need to buy MHD to flash but wouldn't need to pay for their built-in maps. I could make you a tune that retains the power level of your 35is but just tweak the throttle and make some general improvements. The stock tune is good but there's still room for improvement even without adding power.