OPV Update

RE*AC*TOR

I shall in the next few minute be testing the precision of the OPV mod I performed on my Gaggia Classic previously.

That mod is outlined here - http://www.boards.ie/vbulletin/showthread.php?t=2055136560&highlight=opv

Pictures & Video to follow....

Mr Magnolia

Careful, I was told the Classic don't run with the blank filter!

RE*AC*TOR

Mr Magnolia

Water-filled gauge 'n all!

'nuff said so.

RE*AC*TOR

Glycerin filled. Uploading (admitedly terrible) movie to youtube now.

The story here is my OPV modded Classic is running at 11 bar.

If you look at the graph http://www.ulka.it/eng/e5_gra.htm

That's kind within the margin of error for my flow rate calculations - but right at the top.

So more adjusting to do.

RE*AC*TOR

This also means - stock my machine was running at 13-14bar instead of the 12 I previously thought.

Mr Magnolia

The gauge effectively blanked it, did it not? Did the water just flow back on the return?

RE*AC*TOR

Yes. Same as with a blank disc except you get a read out.

RE*AC*TOR

Right reduced it down. Its about 8.75 now. Gonna run a shot and see how it fairs.

Mr Magnolia

*f5*
*f5*
*f5*

RE*AC*TOR

I'll do my best but these videos take time for youtube to process.

Mr Magnolia

What was the coffee like?

RE*AC*TOR

Oh Dear God!!! Its ****ing Amazing!!!

RE*AC*TOR

First video (with the gauge).

https://www.youtube.com/watch?v=NBIzaDwudmU

Mr Magnolia

RE*AC*TOR wrote: »

Oh Dear God!!! Its ****ing Amazing!!!

I'll be carrying this adjustment out myself so. I did reduce it down last year but had no way of measuring the output. I can put my hands on a gauge handy enough.

Did that spout just screw off?

RE*AC*TOR

The spout screwed off with great difficulty. Had to use a strap wrench.

Mr Magnolia

I assume you got it back on ok then?

RE*AC*TOR

Haven't done that yet, but it won't be a problem. I'll put it that way. I used a strap wrench cause I was afraid of scratching the chrome.

RE*AC*TOR

https://www.youtube.com/watch?v=Smz2AXsUojE

RE*AC*TOR

Final comments: brought it back up from 8.75 to 9 on the dot.

The mouthfeel of the coffee has changed substantially. Its gotten quite a bit thicker, gloopier etc. Seems to be about the same amount of crema.

I am detecting more bitterness though. This may just be the particular beans I'm using at the moment. But certainly from the same batch of beans I was using earlier the coffee now feels thicker, is overall a bit richer, but maybe a bit more bitter on the aftertaste.

Mr Magnolia

That shot looked good. I really like that basket. I wouldn't have thought the bitterness would have anything to do with the mod.

Thanks for the report. I'll be adjusting my OPV over the next couple of weeks, I'll start get the fixings together. I'll stick a video in here when I do it. I got those latte cups today, haven't opened the box yet though. Can you let me know if you see those glass cups anywhere, I'd like to pick up a couple.

RE*AC*TOR

Haven't seen them for sale in any bricks and morter place.

The thing about the bitterness in the aftertaste - i'm 100% sure I didn't notice it earlier today with the same beans. It is possible that this is a true reflection of the beans, and the high pressure was masking it.

Mr Magnolia

Very true, could be that. I'll watch it when I do my mod.



I'll check the stickies again for the shot glasses, hadn't seen them anywhere I was browsing recently though.

Mr Magnolia

Do you know what that spout thread size is?

RE*AC*TOR

1/4" i think - let me check I bought 1/4" and 3/8" pieces

2 secs...

RE*AC*TOR

no its 3/8" my gauge is 1/4"

Mr Magnolia

Thanks for that.

RE*AC*TOR

make sure you use plenty of PTFE tape

Mr Magnolia

Will do. It'll probably be a few days before I get time to do this. I'll let you know though.

Found the shot glasses on a couple of sites.

Kitchendresser.ie has them, they're near €20 for 2, a bit steep. It's a good site though, I've used them before.

Amazon won't ship them to Ireland for some reason?

I'll keep searching.

Mr Magnolia

Right.

Took the machine apart and tried to expose the OPV. First problem, I'd over tightened the OPV housing the last time I was at it and strugglefd to get it open. Got it eventually.

Put the gauge and the reducers together and went to the machine with it. Second snag, the friggin gauge with the reducers were too long to fit into the machine housing - disaster.

The last time I carried out the mod I hadn't got a blank filter so I got it out of the press and used it for the mod. I didn't measure it before adjusting but I wasn't too far out after the last adjustment. Still, I went to far with the OPV first, I adjusted it back until I'd a flow of 130ml in 30 seconds which is 260ml in 1 minute which according to the graph is 9Barg.

After each OPV adjustment I tool the blank out and primed the pump so all factors would be equal.

Happy enough. I'm off to tidy up and pour myself a coffee

RE*AC*TOR

Not sure if I follow. Did you actually get to measure the pressure using the gauge?

Mr Magnolia

No. The reducers left it too long to fit into the housing.

I measured the flow using the blank until I had 260ml in 1min which, according to the graph is 9Barg. I didn't have the blank the last time I made the adjustment, so better than nothing.

I will see if I can lay my hands on an elbow so the gauge will fit into the housing.

This is the gauge and reducers that were too long for the machine housing:

RE*AC*TOR

That's a long aul arm alright. Even with the drip tray out it doesn't fit?

Mr Magnolia

RE*AC*TOR wrote: »

That's a long aul arm alright. Even with the drip tray out it doesn't fit?

No it wouldn't fit. The base of the machine under the drip tray obstructed it.

Happy enough with the flow rate though.

RE*AC*TOR

I was happy with the flow rate until I realised the margin of error on the graphs is enormous.
I was still at 11bar with the flow rate measured.

Mr Magnolia

Hrmm.

Have to get that elbow or some new fittings so.

RE*AC*TOR

You are more than welcome to borrow my gauge and / or arm. Maybe not so practical as you are in louth (?). But the offer is there.

Mr Magnolia

RE*AC*TOR wrote: »

You are more than welcome to borrow my gauge and / or arm. Maybe not so practical as you are in louth (?). But the offer is there.

Thanks for the very kind offer. I'll have a look at what I have available. I may take you up on that though.

Mr Magnolia

Well the flow rate against the pressure was out.

It was running at 10Barg, I've now adjusted it down to 8.75Barg and am very happy with the results. It's resulted in the espresso having a more syrup like texture. The crema is also thicker. I can also pick up a slightly smokie aftertaste too now, I hadn't noticed that in this bean before, perhaps because the extraction process is running at the lower pressure and the flavours are enhanced or more detectable? Time for another.

Thanks to RE*AC*TOR for the loan of his gauge

RE*AC*TOR

I found the lower pressure highlighted the flaws in my roasting process.

I was doing iRoast roasts in around 9 mins at the time. Think this was scorching the outside of the bean, resulting in a bitter taste, when I stretched out the roast it improved.

Try a bit of temp surfing also. It's just as important as the right pressure.

The jist of it:
Listen for the super-heated water flashing to steam, once that stops you have a defined temperature. Then say count to 4 seconds from that point, lock in the portafilter and brew.

Experiment with the flush time till you get something you like.