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kfardan kfardan is offline
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Posts: 53
Join Date: Feb 2015
Car: 2014 BMW 335i Sport Line
Default 06-29-2020, 09:55 PM

My personal experience on the N55 engine is 100% Meth made more power than 100% E98.
The car did however feel just a little bit smoother with E98.
I tried even mixture of both maybe 70-60% Meth and the rest E98 .. made almost same power as 100% Meth.
So now I just stick with 100% Meth.

Might be different on B58 though, but give both a try and see which one works for you.

'14 F30 335i N55 EWG - Speedtech Stage 3 EFR 8374 - BM3 OTS Stage 2H 93 Flash - xHP Flash - JB4 - BMS Meth kit - Dorch Stage 2 HPFP - ER FMIC & CP
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RMM RMM is offline
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Join Date: Apr 2017
Car: 120i
Default 06-30-2020, 07:59 PM

FYI I have BM3 with my own tune at about 25 psi, and e20 + 98, JB4 for meth, but no boost control, so I just run in map 0, with meth trigger set to 4.

Still running x98 on my car, I did try mixing in a bit more water again, like 25, 15, and it seems like at 25% I start to lose power, however the timing is perfect, so the water seems to be slowing the combustion down, or improving timing correction, but lose a little power.

I did increase the knock tables a little, and now have pretty consistent timing on both, however, there is a definite correlation to the % water, and timing corrections, so that would tell me that running more water is likely more safe for detonation.

One interesting comment, I have been adding more timing to my tune and , with more timing the power loss with added water is less noticeable. That supports my theory that the water is slowing the combustion and moving the MBT timing up. When I only had about 10-12 deg timing, adding 25% water was a noticeable and repeatable power loss like around 8%. However now with 14-16 deg timing, it is barley noticeable, or in the range of only 2-3%.

It may be that to get the benefit of the added water you need to add a few degrees of timing, but without a proper day of dyno testing I think that would be hard to know conclusively, as you would need to do many runs to compare different water % and different timing tables.
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