I'm on my fourth BDB (or rather, Sage as I'm in the UK) but this is my first brand new one. The first three were bought second hand, and I've kind of done them up, ironed out problems (with lots of help from these forums, thank you) and sold them on.

I was regularly getting between 9 and 10 bar and a 35-40 second extraction on my other machines. However, new machine, same grind and beans, coffee comes out in about 25 seconds at between 8-9 bar. How can this be?

Easily fixed by grinding quite a bit finer, the end result being an improved gloopy tasty espresso, so I shouldn't complain. But can anyone shed any light on why there might be such a variation between an old and new machine, and also why a new machine can push the water through quicker at a lower pressure?

I'm confused.

Dave

I'm not an expert on this specifically (pcrussel here will know much more about it), but I have had different BDBs and they have had some variations, especially new compared to old: The OPV may be set slightly differently, a brand new machine may have clearer flow paths while used machines may have had some degradation, scaling, etc that caused the pump to work harder (higher pressure).

As long as the latitude in settings, grind size, dose get you the resulting taste you want, I wouldn't worry about it. Have you confirmed with a blind basket (or the silicone disk used for cleaning) that your pump pressure gets to around 10bars? If that is good, I'd leave it be. If it isn't getting up to 9 bars, I'd dig deeper (OPV may need adjustment, or you might want to exchange the machine).

Bret wrote:...Have you confirmed with a blind basket (or the silicone disk used for cleaning) that your pump pressure gets to around 10bars?.....

That is interesting.
My BES920 (purchased in March) works always at 9 bars. With or without silicon disk. Few times, when I pull a shot it drops a little, something like "8.75" but otherwise it's alway at 9.

Yea I think there are some normal variations: my last machine went to 10.5 with the blind basket, my current one tops out at just under 10. One coffee I use is just below or at 9b when pulling, another is solid on 9.5b for best taste. Clearly dose/grind/roast are variables during the pulls. And those pressures would change as the coffee ages, but I change my grind as the coffee ages so that doesn't end up varying much.

For the OP: you are using the same coffee and same grind -- is there a chance that the coffee is literally the same bag you were using with the previous one, and has aged in the meantime?

There is some variation in Breville flow rates. My guess is your older machines pumped water closer to 8 ml/s and your newer one is closer to 6ml/s. Lower flow means a finer grind is needed.

Bret wrote:... a brand new machine may have clearer flow paths while used machines may have had some degradation, scaling, etc that caused the pump to work harder (higher pressure).

That sounds very plausible.

...Have you confirmed with a blind basket (or the silicone disk used for cleaning) that your pump pressure gets to around 10bars? If that is good, I'd leave it be.

With the silicon disc it's 9.5. The older machines were 10, but that's because I'd adjusted them to that. I was hoping not to have to open up my new machine until at least the warranty period has expired. But 9.5 is ok yes?

For the OP: you are using the same coffee and same grind -- is there a chance that the coffee is literally the same bag you were using with the previous one, and has aged in the meantime?

The coffee is my own home roasted, which is a source of variation(!), but this was the same batch, and on the same day.

JayBeck wrote:There is some variation in Breville flow rates. My guess is your older machines pumped water closer to 8 ml/s and your newer one is closer to 6ml/s. Lower flow means a finer grind is needed.

I can't get my head around why that would affect it in that way, but I'm happy to believe you! I replaced the pumps in the older machines with the ULKA EP5 as the originals just gurgled and didn't pump during pre infusion. Is that the same as the original Breville supplied pump? Have they changed them since the early days of the BES920?

Sounds like changing pumps and OPV on your older machines fully explains the differences you are seeing in the new, unmodified machine. Probably changing the OPV in the new one will get you nearly back to similar results again.

It should be fine to stay at 9.5 on the OPV, but you'll likely need to compensate with grind size, dose, and/or pull time to get the same in-the-cup result as before. Who knows, you might like it better

Bret wrote:Sounds like changing pumps and OPV on your older machines fully explains the differences you are seeing in the new, unmodified machine. Probably changing the OPV in the new one will get you nearly back to similar results again.

I agree with you about the pump, but the extractions before I changed the grind were at below 9 bar, so I'm guessing the OPV wouldn't be a factor?

It should be fine to stay at 9.5 on the OPV, but you'll likely need to compensate with grind size, dose, and/or pull time to get the same in-the-cup result as before. Who knows, you might like it better

You're absolutely right, I do prefer it. I'll keep it all as it was out of the box, and enjoy. Thanks for all the replies and suggestions.

Dave

albionbrass wrote:That sounds very plausible.



With the silicon disc it's 9.5. The older machines were 10, but that's because I'd adjusted them to that. I was hoping not to have to open up my new machine until at least the warranty period has expired. But 9.5 is ok yes?



The coffee is my own home roasted, which is a source of variation(!), but this was the same batch, and on the same day.



I can't get my head around why that would affect it in that way, but I'm happy to believe you! I replaced the pumps in the older machines with the ULKA EP5 as the originals just gurgled and didn't pump during pre infusion. Is that the same as the original Breville supplied pump? Have they changed them since the early days of the BES920?

Lower flow means longer dwell. Longer dwell means finer grind needed to achieve similar flow since puck will compress differently to hit 9 bar.

Moka 1 Cup wrote:That is interesting.
My BES920 (purchased in March) works always at 9 bars. With or without silicon disk. Few times, when I pull a shot it drops a little, something like "8.75" but otherwise it's alway at 9.

I have recently received a new BES920. This one instead usually works between 9 and 9.5 bars when pulling a shot, and at 9.75 with the blind disk.