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Originally Posted by maupineda
Thanks a lot for sharing your experience, a lot of great information and details.
I have to say that you probably had already found a sweet spot and in the chase of more power you ended up finding trouble. for the cost of going to a stand-alone ECU I'd rather revert back to stock cams and the tune from your friend, or add the CSL Box and the non-stepped headers with an Alpha-N tune, both of which are tested solutions.
I have a CSL box with EU headers with EPIC's tune and I have no driveability issues (no hesitations and I have a smooth power delivery), I also can do heel and toe. Due to the CSL box mine is an Alpha-N tune.
I was also wondering if any day we will find someone that can really tune the MSS70 ECU, but since our cars are so low volume I understand why tuners have not dedicated time to develop their knowledge in our platform.
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Hi Maupineda,
Yes I agree, the sweet spot was with stock cams and V1 stepped headers with a tune sorted out. I should've just added a 3.91 diff and it would really be a super sweet spot
To come back to stock cams is one of the options, and then I can put those cams on my M3. I must admit I would like to avoid this option. When driving the Z4M with these cams with lower and medium throttle inputs it is so responsive and eager, it promises so much and shows such potential.. it is such a pity the ECU won't allow full power. I did put the 3.91 diff on my Z4M and trust me, it feels torquey like a big V8 (with moderate driving).
Regarding making mistakes, let me introduce one more that I did. This 3.91 diff - I bought another unit (it is interchangeable with M3), and I bought with a new clutch plate LSD. The LSD is setup to have too much lock. On the track with the TC Kline setup, there was zero under-steer with stock LSD, the front end was amazing, grips and grips. I changed the diff and I got so frustrated with the introduced under-steer, unbelievable! It is with 12 active clutch plates and 40/65 ramping angles. Stock diff is back on the car, so I did a new setting according to advice from the supplier. Now it is set to have 8 active clutch plates (33% less locking "power"), ramping angles the same.. but I would prefer ramping angles with less lock (higher angles, such as 50/65 for instance). Until I sort out the tune I won't be putting back that diff. I want to compare 100-200 km/h acceleration times, step by step - what do cams provide, what does a 3.91 diff provides.
BTW, I measure those times with precise GPS tool and on same roads and similar conditions (temps). Z4M managed 9.8 sec with stock diff and 334whp (stock cams). My M3 E46 does 11 sec with 312whp, my friends stock manual E92 M3 does 10.7 sec. What is interesting here is that when I put 17 inch wheels on M3 (from my E36) which have a 5% smaller diameter, I measured M3 and got 10.5 sec. So, 0.5 seconds less. The diff is shorter 8%, which means that I highly recommend this mod in any case. Needless to say, M3 E92 has a 3.85 diff stock, and a 6th gear which is 0.87.. while on M3 is 0.83 and on Z4M is 0.85. Either way with a 3.91 diff, our cars have the same revs on the highway as does the M3 E92 in stock form.
Another advice regarding the choice of LSD. Our cars are lighter than other M cars. They're not turbo or huge displacement. I have rear tires Toyo R888R 275/35 R18 and an aggressive LSD is not needed. Hell, with such big sticky tires it would run with an open diff LOL I will experiment and share my experience. My driving style is smooth, and I like to manage the rear end while having the front end like a go kart. I am not a fan of trying too hard to keep the front end gripping in order to have huge lock LSD. Probably if I were to have a square setup, the diff "pushing" would cause less problems.. The point is everything affects everything and it should be properly matched, and, according to your taste. Hope this will help