With regards to airflow increasing perceived acidity, I would put this down to the cooling effects from air flow that is too high. What usually happens on a stock M3 is there is a very brief spike in air temp and bean temp ROR when adjusting the air flow up. Depending when and where one does this during the roast and how aggressive the adjustment is, it can certainly lead to slightly less overall development and in worse case quite severe underdevelopment instigating a slight stall then bake scenario, particularly toward end of ramp to first crack and beyond, killing sweetness.

Since I have modified the drum, the range for effective air flow setting has decreased significantly! Fan starts moving at 1 on the dial, MIN setting is 1.5 - gently pulls lighter flame at tryer hole, MAX is 2.5 - Very strong pull on the flame. This range of adjustment is small but now incredibly sensitive as to the effects it has. As an example 2.2 to 2.5 can make or break a roast making it even easier to use too much air leading to undeveloped / baked coffee.
I now know the limitations of the applied heat / airflow balance and when making airflow adjustments I turn the knob VERY slowly, so that the adjustment takes place over 5 to 10°C resulting in a smooth change to the environment.

In comparison to the stock configuration along with the fan always stuck ON at a setting that was far too high, it is a completely different roaster and when I get the balance right the results are great. If one was to open up the airflow on the back of the drum on a newer M3 without cutting the fan resistor so that you can have complete control, I am guessing that it would only serve to cool the roaster further and decrease development.

I am not saying that one can not achieve nice roasts on a stock M3, I had some great roasts after much trial and error which is the name of the game.

OldmatefromOZ wrote:With regards to airflow increasing perceived acidity, I would put this down to the cooling effects from air flow that is too high. What usually happens on a stock M3 is there is a very brief spike in air temp and bean temp ROR when adjusting the air flow up. Depending when and where one does this during the roast and how aggressive the adjustment is, it can certainly lead to slightly less overall development and in worse case quite severe underdevelopment ......

I can't agree with this. I think the greatest factor affecting what you're talking about is time the roaster is left in certain conditions. The small blips and flips are highly dependent on probe placement and aren't going to drastically affect the beans. The entire system of a Quest roaster is very tiny, and in constant flux. There's very little cruising happening unless one were to charge high and just max everything out and just watch how the roast progresses over time. There's just not enough mass for it work otherwise.

I have probes all over my Quest, and the only one that matters to me beyond the bean temp probe is my exhaust air probe that measures the temp of the air immediately exiting the roaster. If that's caving too fast, you either have inaddequate heat, or (more likely) too much airflow.

TomC wrote:I can't agree with this. I think the greatest factor affecting what you're talking about is time the roaster is left in certain conditions. The small blips and flips are highly dependent on probe placement and aren't going to drastically affect the beans. The entire system of a Quest roaster is very tiny, and in constant flux. There's very little cruising happening unless one were to charge high and just max everything out and just watch how the roast progresses over time. There's just not enough mass for it work otherwise.

I have probes all over my Quest, and the only one that matters to me beyond the bean temp probe is my exhaust air probe that measures the temp of the air immediately exiting the roaster. If that's caving too fast, you either have inadequate heat, or (more likely) too much airflow.

Fair enough Tom, not many people really agree on anything in roasting. We will probably have to agree to disagree because after 1000+ batches over the last 2 years they are my thoughts on the subject, with regards to my setup / probe placement, which is currently just standard bean temp probe with exposed tip. I stopped bothering with the exhaust temp along time ago and chose to focus on one reading. For me any major upward spikes on an overall declining profile end up having negative consequences in the cup, yes I have cupped / brewed / refracted blind.

Any roasting system whether tiny or large is in constant flux, I understand what you are saying in that the quest is tiny and comparatively a larger roaster can cruise along a lot more. But define cruising? With the painted drum and fire blanket insulation it is pretty darn cruisy for me on a 200g roast. I do not have a comparison like you so its all relative.

I can only go by what I have read / seen from you in the past, my guess is we are using our quests in completely different ways - roast style / profile, so we will never have close to the same findings.

Incase anyone is interested....
As I touched on previously the last couple of months I have been nailing down a certain style (having previously tried just about every quest recipe going around) I am actually charging very low 130 - 140°C for a 200g batch so that I may achieve 3min to 100°C, 6min yellow, 9 - 9.30 first crack with 20 to 25% post first crack time to an appropriate medium roast for espresso. As I said previously the quality and consistency I am achieving has exceeded my expectations. Rich, sweet, fulll with balanced acidity / fruits florals.

I use minimum airflow until around BT 125 130°C where I bump it up to 50% of my range. At FULL YELLOW i make my final adjustment to 75% to 100% of my range, adjusting power from here on to smoothly decline the roast.
Artisan settings: smooth curves=5 smooth deltas=9 deltaspan=6sec smooth spikes=ON
Sample intervel=3sec with oversampling=ON

OldmatefromOZ wrote:Fair enough Tom, not many people really agree on anything in roasting. We will probably have to agree to disagree because after 1000+ batches over the last 2 years they are my thoughts on the subject, with regards to my setup / probe placement, which is currently just standard bean temp probe with exposed tip. I stopped bothering with the exhaust temp along time ago and chose to focus on one reading. For me any major upward spikes on an overall declining profile end up having negative consequences in the cup, yes I have cupped / brewed / refracted blind.

Any roasting system whether tiny or large is in constant flux, I understand what you are saying in that the quest is tiny and comparatively a larger roaster can cruise along a lot more. But define cruising? With the painted drum and fire blanket insulation it is pretty darn cruisy for me on a 200g roast. I do not have a comparison like you so its all relative.

I can only go by what I have read / seen from you in the past, my guess is we are using our quests in completely different ways - roast style / profile, so we will never have close to the same findings.

Incase anyone is interested....
As I touched on previously the last couple of months I have been nailing down a certain style (having previously tried just about every quest recipe going around) I am actually charging very low 130 - 140°C for a 200g batch so that I may achieve 3min to 100°C, 6min yellow, 9 - 9.30 first crack with 20 to 25% post first crack time to an appropriate medium roast for espresso. As I said previously the quality and consistency I am achieving has exceeded my expectations. Rich, sweet, fulll with balanced acidity / fruits florals.

I use minimum airflow until around BT 125 130°C where I bump it up to 50% of my range. At FULL YELLOW i make my final adjustment to 75% to 100% of my range, adjusting power from here on to smoothly decline the roast.
Artisan settings: smooth curves=5 smooth deltas=9 deltaspan=6sec smooth spikes=ON
Sample intervel=3sec with oversampling=ON
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This is very helpful info, James, thank you. To those who modify the Quest and report their findings, a huge thank you as well! These threads have been immensely interesting and insightful.

Pertaining to mods, do you therefore recommend the resistor-cut mod to others to increase resolution of the fan? I was considering also painting the drum flat black. I'd like to be able to play with the fan, and if the mod increases both low-end and high-end usability of the fan, I'm all for it.

OldmatefromOZ wrote:Fair enough Tom, not many people really agree on anything in roasting. We will probably have to agree to disagree because after 1000+ batches over the last 2 years they are my thoughts on the subject, with regards to my setup / probe placement, which is currently just standard bean temp probe with exposed tip. I stopped bothering with the exhaust temp along time ago and chose to focus on one reading. For me any major upward spikes on an overall declining profile end up having negative consequences in the cup, yes I have cupped / brewed / refracted blind.

Disagreement is usually a good thing and I encourage it. Regardless of any of us using the same "chassis", we're all driving different models and we're pouring the results over different tastebuds. It's not a "I'm right and you're wrong" -sort of thing. I bet your coffee's spectacular if you're putting that level of commitment into it.

My main concern I want others to be aware of is that talking of spikes and blips and whatnot, all are clouded in a ton of uncertainty, even with the exact same probe type, even located in the same exact spot. Any dampening or softening, or sampling interval changes will drastically affect what data is trended on a wave form. And I doubt there's a large body of users who have everything set identical from hardware to software, literally.

But I'll say this about the Exhaust Air Probe, it's utility lies in knowing in an instant if you're falling behind. If the waveform is steadily increasing throughout the post drying phase, you can trend that and adjust, and know that you're not stalling out. It's especially important with a roaster like this with so much lag. On my 1 kilo, I have the same setup, but I can fix what appears to be a possible stall quite quickly.

TomC wrote: My main concern I want others to be aware of is that talking of spikes and blips and whatnot, all are clouded in a ton of uncertainty, even with the exact same probe type, even located in the same exact spot. Any dampening or softening, or sampling interval changes will drastically affect what data is trended on a wave form. And I doubt there's a large body of users who have everything set identical from hardware to software, literally.

But I'll say this about the Exhaust Air Probe, it's utility lies in knowing in an instant if you're falling behind. If the waveform is steadily increasing throughout the post drying phase, you can trend that and adjust, and know that you're not stalling out. It's especially important with a roaster like this with so much lag. On my 1 kilo, I have the same setup, but I can fix what appears to be a possible stall quite quickly.

I see what you are saying now and agree about the " data " aspect. As always I guess it comes down to each individual getting real personal with their gear and I definitely do not mean to imply definitive statements of fact.

Yeah the lag with the electric elements is annoying and coming from a gas cooking upbringing it was something I really struggled with for some time. One of the reasons I have been chasing the current style of roast and the way I execute it, is that it pretty much eliminates the lag factor. BUT, if i make a mistake or less than optimal adjustment when getting to know a new bean or sometimes I am just tired, it is pretty much game over with no ability to quickly recover. I have completely stuffed plenty of good green in the past.
I am mostly watching the power meter the roaster is plugged into and thermometer for the BT probe, whilst looking through the sight glass, with occasional smelling of the exhaust and clicks / glances at Artisan.

Would love to roast on gas one day if budget allows. I can imagine so much more flexibility to pursue different approaches.

Zanderfy wrote:This is very helpful info, James, thank you. To those who modify the Quest and report their findings, a huge thank you as well! These threads have been immensely interesting and insightful.

Pertaining to mods, do you therefore recommend the resistor-cut mod to others to increase resolution of the fan? I was considering also painting the drum flat black. I'd like to be able to play with the fan, and if the mod increases both low-end and high-end usability of the fan, I'm all for it.

No worries, just giving back a tiny amount of what has been given by many others doing it much longer than I on HB.

As for mods, well personally I would never go back to how MY FAN was setup stock. I am hesitant to say YEAH just do it to others without knowing what there stock configuration is like. The manufacturing has undergone many slight variations with the parts they use.
But yes for me there was a significant increase in top end power (only good for cooling a roast - I cool externally) and near infinite adjustment to the bottom end where it counts.

Are you capable of re soldering the resistor if your not happy? I remember someone making a damper out of foil or something like that? to play with airflow at the exhaust tube / loading chute junction. Perhaps could try this to see if its something you want to do first.

Painting the drum black definitely helps with loads 200g and above. Below that it is not really necessary and personally I did not like it with the stock drum.

Trying out one mod at a time is probably best.

A few questions after reading the banter between Tom and James.

Airflow - This has been a big plus for me coming from a behmor as I always felt airflow was an issue with that unit. I currently wrapped my quest with insulation, but I've also questioned doing the other two mods, fan and drum. But I do agree that only one mod should be done at a time. Personally I haven't found a reason to take fan speed below 20% nor have I found a reason to adjust fan during the roast. I find that the PID really helps maintain a constant temp that helps me get some damn good roasts. With that in mind, between fan and drilling the drum, what mod would you say has made a most defining difference for you?

Probes - I have all of the Eric S. probes in play, but have some mixed thoughts. When I sample roast I only roast 100g's and find the upper bean probe to be less accurate in the beginning, but more accurate towards the end. To explain further, the lower bean probe is definitely deeper in the bean mass but I typically find that when I near first crack, the lower bean probe is reading around 350-360, while the upper probe is reading 375-385 which seems more realistic for first crack. Has anyone checked this out? I'm just curious if my lower probe isn't deep enough or this is just biproduct of only roasting 100g.

Exhaust Probe - Where would this probe be placed and what probe are you using?

Lastly, James I see that you charge at around 140c (284F), which is exactly what I do. Tom what do you charge at, and what are your thoughts?

Thanks guys for your input!

Tom - very interesting about the exhaust probe. what is the relationship between the exhaust probe and the ET probe? Don't both measure internal air temp?

djbetterly wrote:A few questions after reading the banter between Tom and James.

,,,,. With that in mind, between fan and drilling the drum, what mod would you say has made a most defining difference for you?


,,,,Exhaust Probe - Where would this probe be placed and what probe are you using?

Lastly, James I see that you charge at around 140c (284F), which is exactly what I do. Tom what do you charge at, and what are your thoughts?

Thanks guys for your input!

Mod wise, I think installing a perforated rear drum wall has been the best.

My Exhaust Air probe comes in from the top left (facing me) side of the chute, thru one of the holes that was held by a small screw. The probe angles down and the very tip of it floats mid-air catching the temp reading as it exits the drum. I can't recall what exact probe it is, but I custom made it from Omega.

The ET probe is good enough for establishing a charge temp when empty, but when the drum is full, it's not quite as useful. So I've bent it and positioned it in such a way that it is aiming high and very very close to the drum wall surface, positioned about 2 o clock. Here, it's not going to get disturbed by bean strikes, and gives me a more reliable indication of what's going on in the drum.

My charge temps vary depending on so many things.