raising fermenation temp - timing

So I've got an area that is pretty much constantly at 66F where I do most of my fermenting. Then my brew area is more like 69F. I've had some diacetyl issues lately which I am beginning to think were caused by not enough oxygenation (fixing that, my Williams aeration wand came today) but I'd also like to ramp up the fermentation temp as it nears completion. Problem is, I have the above two temps to work with.

So what would be considered a good time to move the beer from 66F to 69F?
I have dunkelweizen 4 days into fermentation and the krausen is starting to drop.

Thanks

Doug

It sounds like you are stating ambient temps and not beer temps? If that is the case, even an ambient temp of 66F is on the warm side for a lot of ales, the temp in the fermenter could be well into the 70's. With that being said, I usually pitch most of my beers a few degrees below fermentation temps, then let them rise to my pre-determined temperature and if I'm going to ramp up at the end, I usually do it when the krausen just starts to fall. You don't want to ramp up too early in the growth phase, it will cause the yeast to produce more esters and fusels.

Yea, I expect your fermentations are warm as well. You may be right about the diacetyl though- strains that produce a lot of diacetyl tend to need a lot of oxygen in order to prevent it. Warm temperatures tend to favor metabolism of diacetyl, not production of it. What yeast are you using?

Wyeast 2112, the cali lager, and S-05. Both batches had it.

Yes ideally I would have a temp controlled fermentation box but I don't right now. I will do a swamp cooler thing if the oxygenation does not help, but as you say, higher temps are not supposed to produce diacetyl, they're supposed to help it.

I've done 60+ batches of beer in this way and produced great results, but lately my venturi oxygenation tube kind of crapped out, and I neglected to do the carboy-shaking exercise the way I should. I really think it's the oxygen.

But the krausen is dropping, so I'll move that batch now.