Tuning the OPV on a Gaggia Classic

frlinux

Hello All,

Haven't been posting in a while in this forum.

Back then Doodee convinced me that I needed to do some proper work on my Gaggia. Well it took only 5 months but I eventually overcame my fear of opening the machine, I have made a gallery just to show how easy it is.

I have to say, the OPV was set to almost its highest pressure, I have now turned it clockwise quite a few times to take the pressure down. I still believe it is a bit high but way less than it used to be. So will test with different coffees before reporting back.

Just thought I'd share

Doodee

Well done.
You are about to notice a hell of a difference.

Just wondering did you check your pressure with the backflow method?

frlinux

Doodee wrote: »

Well done.
You are about to notice a hell of a difference.

Just wondering did you check your pressure with the backflow method?

Yes, this is what i used, hence my comment about it beeing still slightly too high. I have about 150ml of water pouring down in 25s at the moment. I'm afraid to screw it clockwise some more as I seem to have reached a limit, so dunno if it is just stuck or am I at the end of it.

PPC

Pop a message onto ch2008 and i'm sure he'll be more than able to help you with all your questions

Sinfonia

Does anyone know if the backflush method can be done using one of those rubber backflush discs, or does it have to be a blind filter basket?

frlinux

Sinfonia wrote: »

Does anyone know if the backflush method can be done using one of those rubber backflush discs, or does it have to be a blind filter basket?

blind filter.

Sinfonia

And how come?

(From reading other forums on the subject, it seems to be suggested that a rubber disc is fine, but it's never explicitly stated)

Mr Magnolia

The rubber discs are fine. Anything that blocks the water from coming through the portafilter will backflush the machine.

Sinfonia

Mr Magnolia wrote: »

The rubber discs are fine. Anything that blocks the water from coming through the portafilter will backflush the machine.

Thanks! I actually went ahead with the rubber disc, worked fine.
Measuring the backflow presumably isn't 100% accurate anyway, but at least the pressure is lowered to around the right area.
Crema seems darker but not really coming out in 'globs' as I've read, but that's probably a technique thing on my end too. I've also got a grinding issue because the MDF doesn't go to 7.5 :P (unless I do the stepless mod)

Tom Ghostwood

Just adjusted the pressure on my gaggia classic. 125ml of water from the OPV @ 30 secs. Took a good few tries to get it there as I was adjusting the nut the wrong direction at the start. Bottomless portafilter came today. Beans arrive tomorrow.

Any tamp & grind tips/settings for Jaberwocky & gaggia mdf grinder? Just to begin with like.

Zymurgist

I really need to adjust the OPV on my classic i think.

I can't pour a shot without getting coffee spraying out about foot either side of the machine!!

PPC

Zymurgist wrote: »

I really need to adjust the OPV on my classic i think.

I can't pour a shot without getting coffee spraying out about foot either side of the machine!!

You could try grind finer as well, that should slow it down and you could tamp harder as well.
You should be aiming for about 30~40ml in ~25seconds.

Sinfonia

Zymurgist wrote: »

I really need to adjust the OPV on my classic i think.

I can't pour a shot without getting coffee spraying out about foot either side of the machine!!

Before anything else, check to see what kind of basket you have.
Someone on this forum recently bought a Classic and it came with a pressurised basket but without the little rubber thing that a pressurised basket needs

Here's a video about those baskets. It could well be the problem you're having.

https://www.youtube.com/watch?v=b2EDz4lango

Zymurgist

Thanks for the tip Sinfonia turns out that was the exact issue i was having.

Luckily i found the little rubber jobbie was just in a drawer so was able to track it down and fix the problem.

Thanks again

dakar

Hi Guys,

Unboxed my Gaggia Classic this morning (early Christmas present, well, I do want to have it up and running on Christmas morning!) and I have a couple of questions re filter baskets, OPV etc.

I don't have a blind filter basket or pressure gauge yet, so have no empirical way of testing pressure. Do you reckon I should just drop the pressure on the OPV (180-270 degrees or so) and see how it runs, or should I wait until I can check properly? I can't see any reason not to fiddle with it, other than wasting coffee in the process, but I don't intend running through my nice Hasbean Espresso starter pack for the experiments.

Also, I'm not gone on the idea of the pressurised basket. I was going to use the double basket from my old Cubika until I get hold of a VST basket. Does this sound like a reasonable plan?

Thanks in advance.

Sinfonia

dakar wrote: »

Hi Guys,

Unboxed my Gaggia Classic this morning (early Christmas present, well, I do want to have it up and running on Christmas morning!) and I have a couple of questions re filter baskets, OPV etc.

I don't have a blind filter basket or pressure gauge yet, so have no empirical way of testing pressure. Do you reckon I should just drop the pressure on the OPV (180-270 degrees or so) and see how it runs, or should I wait until I can check properly? I can't see any reason not to fiddle with it, other than wasting coffee in the process, but I don't intend running through my nice Hasbean Espresso starter pack for the experiments.

Also, I'm not gone on the idea of the pressurised basket. I was going to use the double basket from my old Cubika until I get hold of a VST basket. Does this sound like a reasonable plan?

Thanks in advance.

I'd say wait til you have a blind filter (or rubber backflush disk).
You don't necessarily need a pressure gauge. It will give you the most accurate results, but it kind of looks like a bit of a pain to get together (if you're not particularly au fait with that kind of DIY handiwork). I just measured it using the backflow method (should be easy to find a guide to that via Google, but if not come back and I (or someone else) can explain it.
It's not like the coffee is gonna be horrible in the meantime, and Classics tend to be shipped with the OPV set to different pressures, so it could be set to 9 bar currently, and then you'd be spoiling it. So wait until you can measure it.
(Extra tip: for the bit that requires a socket wrench to unscrew, use a socket wrench. After putting my entire body into trying to turn the thing with pliers and spanners without a budge from the screw (and some sratched paint!) I remembered that I had a 4-way socket wrench in my car for changing the tyres and it just so happened to have a 17" end. The screw came off like butter off a hot knife.)

Pressurised baskets seem to be a bit crap, so if the Cubika basket is the same size I'd say use that.
As for the VST, I ordered mine from Square Mile and it was delivered within two days, although I don't know how the postal service will be around this time of year.

Happy Classicing! :pac:

dakar

Thanks for that, I'm thinking that given there's just one hole in the pressurised basket that came with the machine, it can't too hard to make myself a backflush disc to do the job...

Hadn't found the VST baskets on Squaremile. Thanks for the heads up. It'll probably be the new year before I get hold of one though.

okedoke

I'm thinking about trying this mod on my classic and I've got the flow rate graphs for the Ulka pumps. http://www.ulka.it/pagine_1.php?id=151&id_liv=3&id_liv2=110&id_liv3=109

How do you know what pump your machine has?

Also I haven't seen any guide that explains the backflow test method (as opposed to the mod itself)

You insert the blind basket, turn on the brew switch? and water comes out somewhere? You measure this flow and compare to the cc/min in the graphs above.

Cheers

glynf

Sinfonia wrote: »

I'd say wait til you have a blind filter (or rubber backflush disk).
You don't necessarily need a pressure gauge. It will give you the most accurate results, but it kind of looks like a bit of a pain to get together (if you're not particularly au fait with that kind of DIY handiwork). I just measured it using the backflow method (should be easy to find a guide to that via Google, but if not come back and I (or someone else) can explain it.
It's not like the coffee is gonna be horrible in the meantime, and Classics tend to be shipped with the OPV set to different pressures, so it could be set to 9 bar currently, and then you'd be spoiling it. So wait until you can measure it.
(Extra tip: for the bit that requires a socket wrench to unscrew, use a socket wrench. After putting my entire body into trying to turn the thing with pliers and spanners without a budge from the screw (and some sratched paint!) I remembered that I had a 4-way socket wrench in my car for changing the tyres and it just so happened to have a 17" end. The screw came off like butter off a hot knife.)

Pressurised baskets seem to be a bit crap, so if the Cubika basket is the same size I'd say use that.
As for the VST, I ordered mine from Square Mile and it was delivered within two days, although I don't know how the postal service will be around this time of year.

Happy Classicing! :pac:

Hi,

Thought I would resurrect this thread instead of creating a new one.
I cannot find a link to a guide on how to use the backflow method to measure pressure on a Gaggia classic, can someone please point me to same?

I recently descaled and the pressure is down, so much so that it 'choke' the machine grinding beans at the normal consistency I use.

Might I have fried the pump by back flushing too much?

Mr Magnolia

Did you back flush or just descale?

If you did back flush, did you have a flow on your return line?

Edit; here's a back flush video, not a classic but principle is the same

https://www.youtube.com/watch?v=4U6J2JJH9gA

glynf

Hi,

Thanks for the reply. Yesdescaled and rinsed the machine twice to get all the detergent out. I backflushed it 1-2 times during each rinsing. I had and still have flow on the return line (to me the one that is off of the top the OPV itself?)

To check the flow:


I turn the machine on, then the steam button also to on. I then put the rubber disc into my portafilter, and reroute the tube off the top of the OPV into a measuring jug. Then I turn on the pump, and measure the flow from this. I have adjusted the OPV itself so I am getting about 125 ml in the jug in 31 or so seconds. I know its not the most accurate, but does this sound about right?

When I try a shot, the machine chokes like the pump does not have enough power..

I have an Ulka EP5 pump, another variable is I have not used the machine in about 3 weeks, I was awaiting new grinder blades-might sediment or something have built up inside?
I am happy enough that the coffee I am grinding is about the same consistency as always.

Mr Magnolia

Your pump is fine.

Your grind consistency as you put it needs to change in line with the adjusted pressure drop. If you've wound your opv out you've reduced water pressure to the group head. I would expect that your old grind is much to fine as you were extracting at circa 15bar whereas now with the adjusted pressure you're group head is at 9-10bar. You'll need to dial your grinder to a coarser grind to pull the same shot but you should note a substantial improvement in the quality of shot. I've never used the flow method for adjustment so you may need further tweaking, if you do you should seek out an pressure indicator.

glynf

Mr Magnolia,

Many thanks again for your reply. I was a bit nervous about he pump to put it mildly. I will try a coarser grind tomorrow-I'm out of beans and already bouncing around the place after several taste tests this evening

I'm not convinced the flow method re. adjustment is the best option, I looked at building a pressure tester before, is this what you mean by a pressure indicator-or is there a pre built unit available?

I put this together based on another forum post:



The part numbers are verbatim to what the guy used to build it but are imperial, I tried a few instrumentation & plumbing suppliers who told me they supply metric only. I don't want to destroy the threads on my portafilter forcing a metric fitting on it, so must try the UK or something for similar bits.

Mr Magnolia

Yeah, don't try and mix imperial and metric. If you have all of the above you should be able to find a reducer online fairly cheap though I've never looked for one myself.

Dial it a little coarser and let us know how you get on.

glynf

Nope, I have none of the above, not very clearly put but I meant I put the document together. Must try UK though. Will indeed post how I go with the coarser grind.

donnacha

glynf wrote: »

When I try a shot, the machine chokes like the pump does not have enough power..

I have an Ulka EP5 pump, another variable is I have not used the machine in about 3 weeks, I was awaiting new grinder blades-might sediment or something have built up inside?
I am happy enough that the coffee I am grinding is about the same consistency as always.

I might be picking this up wrong but my reading of this is that the major change to your set-up is that you got either new burrs/blades for your grinder... I'd say they are just doing their job and you need to adjust the grind setting to a coarser grind.

frlinux

I thought I would report on my experience on tuning my Gaggia, I have since descaled and cleaned the portafilter too. As expected, I had to readjust the grinding to finer since I had more water flow. Result is really peachy though so thanks for the advice guys.

okedoke

I have put together a pressure tester for my classic so I could change it to 9bar - if someone wants to borrow it - I'll lend it to you if you want to pay postage to you and back (as a crude security measure I'll say only people with a >100 posts can borrow it)

glynf

Hi okedoke, it would be brilliant if I could take you up on your generous offer? I can collect in dublin area and leave a deposit if required?

G.

okedoke

Hi Glynf

I'm in Cork - PM me your address and I'll send it on to you - you can paypal gift me the cost of postage.

OD

dakar

Hi okedoke,

I would love to check mine as well. I've tried adjusing the OPV without being able to definitively check the pressure. If you don't mind, I'd like to borrow it when glynf is done.

Many thanks

Darren

okedoke

Glyn

I posted that today - very easy to fit.

First Remove the spout from the portafilter. I did this by putting a thin screwdriver through the double spout and using this as a lever to turn the spout. I think its glued so it takes a lot of force to start moving but once you break the glue it moves quite easily.

You then have a threaded pipe coming down from the portafilter.

Take the filter basket out of the portafilter.

Turn on the gaggia and leave it to heat up for half an hour or so.

Fill the pressure guage with water by running the tap into it.

Screw the gauge onto the threaded pipe coming out of the portafilter.

Press the brew button and open the steam pipe until water is flowing out of the steam arm then close the steam pipe.

The gauge will settle at the pressure ( I read online that the pressure shown on the gauge is around 1 bar lower than the "true" pressure)

here's my test (before adjusting OPV) https://www.youtube.com/watch?v=2Qr-ttwTBUU

Adjusting the OPV is simple - lots of online guides to it.

Steve

okedoke

dakar wrote: »

Hi okedoke,

I would love to check mine as well. I've tried adjusing the OPV without being able to definitively check the pressure. If you don't mind, I'd like to borrow it when glynf is done.

Many thanks

Darren

Darren

no problem : Glyn - will you post it to Darren when you're done

Steve

glynf

Many thanks Steve,

I will PM Darren as soon as I am done with it.

glynf

It arrived this AM, I won't have a chance t adjust until Saturday so I will have it in the post Monday morning the latest to dakar.

glynf

dakar, I held off posting it yesterday and sent it this morning from Roscommon instead-should reach you faster than posting from Wicklow.

okedoke,

Thanks again for the loan & detailed post on using it. My machine was measuring 9.5 bar at the gauge, so I adjusted it to 8 bar at the gauge, based on what you mentioned about the gauge pressure being 1 bar lower than the "true" pressure. I'm getting better shots, about 18 sec. for a double, tastes good but the crema fades fast. I'm gradually adjusting the grinder for a finer consistency.

okedoke

Hi Glynf

I'm no expert but for most beans I find I get better shots (sweeter, less bitter) between 30 - 40 secs. Over 40 secs can sometimes be very tasty but is often sour for me.

dakar

The gauge arrived from glynf this morning. I will check my machine over the next couple of days and get it back to okedoke.

Thanks again guys

Darren

Mr Magnolia

Aim for 25-30 second shot.

Laphroaig52

Mr Magnolia wrote: »

Aim for 25-30 second shot.

When does the clock start?
When I flick the switch or when the coffee starts to flow?

PPC

Flyer28 wrote: »

When does the clock start?
When I flick the switch or when the coffee starts to flow?

From when you press the switch.

I'll normally aim for 28s for an espresso and about 20s for a shot for an americano which tastes nicer when diluted.

Sinfonia

Flyer28 wrote: »

When does the clock start?
When I flick the switch or when the coffee starts to flow?

When you flick the switch.

Bawnmore

Any chance at all I could borrow the pressure gauge too? I'd love to give this a go.

okedoke

Bawnmore wrote: »

Any chance at all I could borrow the pressure gauge too? I'd love to give this a go.

no problem - send a pm to Flyer28 with your address

Bawnmore

okedoke wrote: »

no problem - send a pm to Flyer28 with your address

Fantastic - will do. Cheers!

James_R

Just wondering if this gauge is still going around? I've tried to get my bar pressure correct by timing the amount of mls through the OPV with a blind portafilter in there but it might be nice to test it more accurately.

Muahahaha

Lads just wondering about seconds and millitres. Is there some sort of guide about how many ml of coffee a 20/25/30 second shot should produce ? I'm keen to measure what my machine is doing, it's a Classic and I can only presume the OPV is on its factory setting.
Also I plan on doing the OPV adjustment down to 9 bar soon, I'm waiting on a new shower screen and de scaling powder so will do everything together when it arrives. But I should ask about grinds because for now I don't have a grinder and am stuck purchasing pre ground espresso coffee. With that in mind is there any reason why I shouldn't dial down to 9 ? Also would people say that all preground espresso is ground more or less equally or are there large variances in the coarseness of the grind between different brands on the market ? If I like a coffee with lots of crema is it predominately Arabica preground I should be seeking ?

Sorry for all the questions, I'm just at the beginning of this journey, fascinated so far:)

Mr Magnolia

Muahahaha wrote: »

Lads just wondering about seconds and millitres. Is there some sort of guide about how many ml of coffee a 20/25/30 second shot should produce ?

25s 2 oz as a rule of thumb.

I'm keen to measure what my machine is doing, it's a Classic and I can only presume the OPV is on its factory setting.

Most likely still at 15Bg as you say.

Also I plan on doing the OPV adjustment down to 9 bar soon, I'm waiting on a new shower screen and de scaling powder so will do everything together when it arrives.

You'll need to try and get a pressure gauge and a few fittings from somewhere to do it right.

But I should ask about grinds because for now I don't have a grinder and am stuck purchasing pre ground espresso coffee. With that in mind is there any reason why I shouldn't dial down to 9 ? Also would people say that all preground espresso is ground more or less equally or are there large variances in the coarseness of the grind between different brands on the market ?

I'd stop buying preground, save your money and buy a grinder. Preground is a waste of time, really horrible stuff that won't really resemble what you'll be making with freshly roasted, freshly ground beans. What are you dialling down to 9? The pressure? Go for 8.5 if so and hold off until you get a grinder. It'd be like servicing a ferrari and filling it with diesel.

If I like a coffee with lots of crema is it predominately Arabica preground I should be seeking ?

I don't know that you could associate crema diectly with arabica coffee, freshness and roast profile would probably have more to do with it. Enjoy!

Muahahaha

Thanks for the reply Mr.Magnolia. I did a rough measurement the other night into a 150ml glass, a 25 second shot made me a coffee that was approx 100-110ml in size which seems like way too much if I am correct to say 2oz=60ml.

So it seems either the pump is pushing through too much water or else my puck is channelling the water too fast. It might be the latter as right now I'm using the standard plastic Gaggia tamper which is useless. When the proper one arrives in the post I should be able to eliminate channelling if it is the reason for my problem.

I totally get what you say about a grinder but I suppose like many coffee novices I put the cart before the horse and bought the machine first ! I have my eye on an Iberital MC2 as they seem good value and have decent reviews. It'll be a few weeks before I can afford it though !

Mr Magnolia

Put more coffee in. More coffee means more resistance = slower pour.

You should weigh what you're dosing to keep it consistent.