Quote:
Originally Posted by DSCPLN
From a high performance driver friend:
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This is really good and really explains the art that is a good launch. You have to take into account so much. The pavement temp, tire temps, outside temp, silt or road, asphalt or concrete and rpm range and clutch release. It really is an art that can probably only be mastered by practicing with a timer and muscle memory of what worked when and where.
I am still open so some suggestions, for example a driving instructor told me to pretend there was an egg between the throttle pedal and the throttle actuator so that you press delicately. It helped a bit and there are probably tips like that that hopefully will help out.
Now I go off a little bit......
DSCPLN I know the CDV keeps coming back in the discussion so I promise that this is the last mention I make. You said that there are many opinions on this which is one one of the problems with the forums and the Internet. Every opinion is weighed equally. Someone can spend days doing research, posting actual numbers and real data and engineering analysis and someone will just make an off the cuff comment and the forums weigh them equally as just another opinion. I think that is a mistake because there are many that are thorough and are on quest for the truth and try to back it up with data.
For example, I stated that the the transmission in our cars is near the limit of its rated capacity and that is something to consider when increasing the shock of removing the CDV valve. Especially when the bigger issue with our cars is the triple combination of turbo lag, a crazy surge coupled with limited traction and an engine that where output seems to vary quite a bit with temperatures. For example as related to launching the 1M. I find on cool morning the motor makes more power but the tires are colder! Later when the tires are warmer, the car doesn't pull as hard....crazy!
Anyway, our performance buddy is right on on every point but his last statement also goes with what I am speaking about the internet where everything is weighed equally.
The e90 does not make the torque like the 1M.
At 1800 RPM we are speaking about 320 lb ft going through the driveline and mounts. The e90 is more gradual and doesn't even make that much torque at full swing. Furthermore, the transmission in the e90 is much higher rating that the 1M gearbox. So he implies that his experience without CDV and launching all the time is directly related to the twin turbo 1M. If you look at the ZF link I provided the next model up is the M3 gearbox and it is a 53BZ rated at 600 NM (442 lb/ft). You have a higher rated gearbox with less torque. The opposite is true with the 1M. You have a lower rated gearbox handling more torque so driveline jolt is a bigger concern in our cars.
Also the part about BMW only one using CDV valve, I will not speak to because I only speak about things I research and don't know off-hand if that is true. What is true is that BMW uses expensive dual mass flywheels. The dual mass flywheel is a two piece flywheel where both pieces can move respectively with springs to absorb engine vibration. While this design makes for smoother running, it is another piece that is impacted severely by a jolt and they can soften over time, overheat and fail.
You will notice the 1M has a clutch temperature sensor. This piece is expensive and another reason engineers use CDV to reduce the driveline jolt.
https://en.wikipedia.org/wiki/Dual_mass_flywheel
I see a lot of these testimonials all the time. In another thread discussing direct injected turbo oils and 15k oil change intervals, someone chimes in and says my old 328i has 250K miles and I changed the oil every 15K miles totally discounting all the research posted about direct injection spraying cylinder walls and some fuel mixing with oil, etc. Again, everyone just weighs this off the cuff irrelevant statement the same. The 328i is a normally aspirated, port injected motor. The 1M is a twin turbo direct injected motor and the oil is taking a bigger beating than his 328i.
Another poster says on an F80 says I didn't break-in my e46 and 80K miles it doesn't burn any oil. Again, if that's true, lucky for him but his car used iron cylinder walls, the F80 used a new process where metal is welded directly on the aluminum block. Not the same material on the new cars.
So that is all I will say about it anymore and I apologize if your thread went off. I wish the CDV hadn't been the first silver bullet mentioned in it. I assume with your mods that you are OK incurring the additional risk to the driveline but I just want to make sure that people don't just think taking off the CDV is going to give them 2 second faster launches with no impact to the durability of the Dual mass flywheel and gearbox. I hope you understand the spirit of why I posted this.
Humbly.... done.
Thank you.