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Audi 5 cylinder - Crank balancing factor

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I have just done a rebuid of my 5 cylinder engine (2018 RS3 2,5 DAZA - 400 HP), and we used 50 % balancing factor (100% rotational mass + 50 % recip mass) which seem to be common for Audis 5 cyl. I have found limited litteraure on the topic, and my balancing shop tried to fit some ultra light rods and pistons, which included bob weight reduction of 79 grams compared to oem. This is significant and we were not able to find required mass on cranck to balance this out. Nor place to add/insert mallory. From that point had to convert to a different piston rod combo . . Application is 50% track / 50 % road. Engine power 750hp / 900nm.

Couple of questions:

Is the 50 % balancing factor what Audi performs at the factory?

The oem engine revs to 7000 rpm and I will increase that to 8000 rpm including upgrade of valvetrain, conrods etc. Would the increase in rpm call for a change in the balancing factor? For those engines where balancing factors are changed to acommondate different rpm range, what level of change are we talking about, is it 5 % over/under balancing or more?



Following this too Jarle. See what Andre says :)

They're not a common engine for tuning down here, and so outside Andre's experience, so I would suggest checking out the European and American AUDI tuning forums.

However, unless I'm missing something elementary, I don't get why you want to ADD counter-mass when using LIGHTER reciprocating parts?


You would not. Adding mallory would only be a secondary way of moving the center of balancing to mid of crank counterweights to be able to remove applicable mass.