Pre combustion chamber design research

[Rockabillyrat]

Some of you might know I've been spending alot of time researching and developing an injector nozzle in hopes of picking up some extra HP and MPG. (I know I know a full write up on that is coming very soon.) But I shifted gears and started looking into pre combustion chamber designs because I feel injectors and cups have a direct relationship to each other. And after reading alot of research papers I've come to the conclusion that we might be going about this all wrong.

For as long as I can remember marine injectors and diamond pre cups have been the go to for performance set ups. But the more and more i dig into this I think we are going backwards. Thinking that gm engineers changed the injector flow rate curve and cup sizes for power is comical. These are light duty economy engines that's what they are built for. I believe all the changes made to the 6.5 vs the 6.2 was simply for emmisions and nothing else. After all look at the era the 6.5 comes from. Ford didn't change their cup design nearly as much as gm did. And those guys and making more hp than we are. It may have something to do with the fact that these engines ended up in 1/2 ton trucks and emmision standards are different in lighter vehicles.

A idi relies on heat and a high velocity of air entering the pre combustion chamber to atomize the fuel and start the combination process. The combustion pressure then pushes the remaining air/fuel mixtute out the chamber. A pressure drop at the cup throat farther atomizes the fuel before it finishes the combustion process in the cylinder.

I found a research paper "combustion characteristics of a swirl chamber type diesel engine" and it had some interesting information. It compared different pre combustion cup throat sizes and angles and what effect it had on the combustion process. Here is where things get interesting. I'm going to focus mostly on throat sizes because that seems to be the biggest difference between all of the cups offered in the 6.x platform.

The smaller the throat size the greater the velocity entering the pre combustion chamber. And it has the same affect on the air/fuel mixture leaving the cup. More velocity equals more atomization. It also speeds up the combustion process. Faster burn makes higher cylinder pressure causing a harder push on the piston. In other words more power!!!

A larger throat has the opposite affect. Slower velocity in and out of the chamber resulting in less atomization. Creating a longer burn time making less cylinder pressure.

Compression ratio can also have an affect on air velocity into the chamber

With this information I think there may be an advantage to using the smaller pre combustion cups. But to get the best affect the correct injector flow rate curve and spray pattern need to be used with the smaller cup.

I'm not going to get too heavy on this subject because I'm saving some of this info for my injector write up.... Because of the high air velocity entering the pre combustion chamber an idi can use a very course spray patter. The combination of vaporizing on the cup/ chamber walls and air velocity does a great job of atomizing the fuel. Ricardo himself did testing on spray patterns and found that a course spray pattern with large volume and short duration made the best power. It has a faster burn time making higher cylinder pressure. Also a course pattern gets more fuel into the cylinder resulting in more combustion pressure on the piston. While a fine spray pattern with long duration does the opposite. Longer burn time with less cylinder pressure and less combustion pressure on the piston due to more combustion in the chamber. But I think there can be too much of a good thing though. A very course single shot injection event could make the most power. But could have horrible idle and cold start characteristics.

In conclusion I think the smaller pre combustion cup combined with a course spray patter that has a large flow rate and short duration may be the trick to getting more performance out of these old oil burners. It will have a faster burn rate resulting in higher cylinder pressures. And the small throat size will cause a higher air velocity into the chamber and better atomization of the suspended fuel entering the cylinder from the chamber. Just have to find the right combination of both.

But I'm no expert and you can take what I have to say with a grain of salt. Have a great day everyone!

(P.s. sorry for any misspelled words or grammar mistakes.)

 

[ak diesel driver]

John of unique diesel ran lower pop pressure on his race truck to get more fuel into the engine.

 

[Rockabillyrat]

John of unique diesel ran lower pop pressure on his race truck to get more fuel into the engine.

I want to play around with pop pressures when I get around to bench testing my nozzle. I could see a benefit to lowering them to get the spay pattern I'm after.

 

[n8in8or]

John of unique diesel ran lower pop pressure on his race truck to get more fuel into the engine.

I went from 2500psi to 1750psi pop pressure and didn’t find any power on the dyno. To Rat’s point though, pressure is just one part of the equation. I like the ideas and it would be interesting to test. I remember War Wagon had small pre chambers in one of his builds and he said it smoked more, but I’m not sure what affect it had on his power. It’s cool stuff to think about and tinker with! Too bad it takes so long to swap precups.

 

[Will L.]

We did a bunch of testing and it is quick to see lower pop pressure allows the ip to push more fuel through the injector. But the finer mist produced more power and better mpg.

We didn’t try all combinations possible I’m sure, but we were doing runs for everything from stock heads, turbo, etc. To twin turbos, punched heads altered precups, etc.

The larger volume of fuel from everything we did was far more altered by ip than injectors.

The small precup and higher air speed is a long known and proven concept, but it was easier to get high volume of air and allow more fuel to come in through larger precups.

It will be interesting to see what you come up with.

 

[WarWagon]

The smaller the throat size the greater the velocity entering the pre combustion chamber. And it has the same affect on the air/fuel mixture leaving the cup. More velocity equals more atomization. It also speeds up the combustion process. Faster burn makes higher cylinder pressure causing a harder push on the piston. In other words more power!!!

A larger throat has the opposite affect. Slower velocity in and out of the chamber resulting in less atomization. Creating a longer burn time making less cylinder pressure.

Compression ratio can also have an affect on air velocity into the chamber

With this information I think there may be an advantage to using the smaller pre combustion cups. But to get the best affect the correct injector flow rate curve and spray pattern need to be used with the smaller cup.

In conclusion I think the smaller pre combustion cup combined with a course spray patter that has a large flow rate and short duration may be the trick to getting more performance out of these old oil burners. It will have a faster burn rate resulting in higher cylinder pressures. And the small throat size will cause a higher air velocity into the chamber and better atomization of the suspended fuel entering the cylinder from the chamber. Just have to find the right combination of both.

But I'm no expert and you can take what I have to say with a grain of salt. Have a great day everyone!

(P.s. sorry for any misspelled words or grammar mistakes.)

Frankly, No.

I have run the small NA 6.2 precups with a "hybrid 6.2/6.5" after blowing a couple 6.5's all to hell. No one knew any better and budget had me run the 6.2 heads. With the "Asthma Attack" GM3 turbo you really don't notice the difference. Now we step into the word "Performance" and toss the POS GM3 to the scrapyard. So dealing with engines that can actually breathe...

Performance to me is going from 33 MPH to 55 MPH... while climbing a 10%+ grade in 100+ degrees towing at or over GCWR with the throttle wedged to the floor for miles hoping we don't scuff a piston again. 4X4 low is an option to gear down. Turbo "boost creep" at altitude of 8600' is a problem I had to address on the GM3. A performance limiting item to me is the limits of conventional diesel engine oil.

Running both DB2 and DS4 with a huge ATT turbo and all the fuel I could throw at them: Small precups turn "performance" fuel levels into big belching clouds of black smoke. The Military exempt 6.2 NA precups with a DS4 would block out the sun! EGT's could pass 1550 degrees sustained. Fing dog that could hardly light the turbo and get out of it's own way. Biggest goddammed mistake I ever made was trying to get performance power out of a 6.2 NA engine precups. I had the tuner sitting next to me and we tried everything to clear the smoke. Timing, etc. Finally had to simply cut fuel even though we had 17 PSI+ (The limit of the map sensor) out of the ATT blasting air through the engine at 1550 EGT sustained towing grades. We even tried a HX40II on that engine - no real change.

The minimum you can play with is the 6.5 NA precups. I run that now with "Patch" and it hits a wall as well. Not as bad as the smaller 6.2 precups. Only reason I have 6.5 NA precups over the 6.2's was FOD ruined the 6.2 heads and forced me to change them.

There is simply a point where the precup is just that: starts the fire and blows some air and all the fuel out the precup to swirl, mix, and burn above the piston. The swirl mixing allows a more complete fuel burn and good MPG for the antique injection technology. Add power and more "boost" and the air velocity is swirling so fast it centrifugally separates the fuel and air. Yes, you literally blow the fire out! Result is black smoke.

Look up the Econo 100 HP precups used in the Frito Lay delivery vehicles. Gutless wonders that got great fleet MPG.

Edit: I actually posted more about this including pictures of precups I run here:
http://www.thetruckstop.us/forum/threads/harmonics.47008/page-2#post-551432

 

[THEFERMANATOR]

I read your post, and I didn't see any mention of turbo charging. All of what you posted sounds true, for a naturally aspirated application, but adding a turbo can greatly change things. With a N/A application, the airflow in and out of the pre-cup is pretty much static, but with turbo charging the airflow changes with boost. As boost goes up, so does the air present in the chamber, so the combination that has the correct attributes at N/A levels will greatly change with boost, and you can actually increase the airflow in and out of the precup to the point it stalls like war wagon describes.

It would be nice if the prechamber was large enough that you could do something like mercedes did, but I don't see there being enough depth to run that type of prechamber in a 6.5l.

 

[Rockabillyrat]

Thank you Will L. and WarWagon for some of your real world experience and information.

Boost pressures increasing the air velocity is something I have thought about. I just wonder if there is a right combination of parts that can make it work. But there is only one way to find out. I do have a set of both 6.5 n/a and diamond precups I plan to test my nozzles on. Either way it will be a fun experiment not much of that going on with these engines now a days...

 

[Will L.]

You said “boost pressure increasing air velocity...”

Not to be picky, but two different things there. Pressure is a by product from the restriction of flow and the decrease of velocity. Kinda the basis of ATT or hx40 turbo vs gmx ones. The bigger turboflows more air with less pressure. The velocity of the air being drawn from precup to be measured and being better at all rpm simply cant happen. If is going to flow better at low, middle, or high rpm.
The larger the precup opening the better at high rpm.

Increased air velocity isn’t always the best. Smaller head ports, smaller valves running at identical rpm will increase air velocity, but acceleration rates are always slowernin those engines. Thats why porting heads always helps. The only drawback to porting is generally cost and in certain engines (not ours) the loss of scavenging if opened up too much.

That said, I don’t want to discourage you from trying. Proven best method is always right until someone proves a better way.

 

[Rockabillyrat]

You said “boost pressure increasing air velocity...”

Not to be picky, but two different things there. Pressure is a by product from the restriction of flow and the decrease of velocity. Kinda the basis of ATT or hx40 turbo vs gmx ones. The bigger turboflows more air with less pressure. The velocity of the air being drawn from precup to be measured and being better at all rpm simply cant happen. If is going to flow better at low, middle, or high rpm.
The larger the precup opening the better at high rpm.

Increased air velocity isn’t always the best. Smaller head ports, smaller valves running at identical rpm will increase air velocity, but acceleration rates are always slowernin those engines. Thats why porting heads always helps. The only drawback to porting is generally cost and in certain engines (not ours) the loss of scavenging if opened up too much.

That said, I don’t want to discourage you from trying. Proven best method is always right until someone proves a better way.

Poor wording on my part. I was talking about the increase in velocity after the pressure drop through the pre cup throat. I really like your referal to turbine housings. That's a great way of looking at this whole thing. I think matching the pre cup size to an engines air flowing capabilities will have benefits.

I really want to compare our pre cup throat size and cc volume to the 7.3. Justin at R&D has pushed big fuel and boost number cleanly on the stock cups.

Not discouraged at all. Trust me I got all sorts of negative feed back when i made a comment about my injector nozzle research on Facebook. At least your not resorting to name calling lol

 

[THEFERMANATOR]

The other thing to keep in mind when comparing the 6.2/6.5 vs 6.9/7.3 is the fact there engines can take more abuse without failure. So even though they may be hitting the wall, there engines can take the extreme where the GM engine will melt down. Several of the highest HP 6.5's to my knowledge are running pre-cups that are larger than the diamonds.

 

[Rockabillyrat]

I still think that the 6.5 injectors and turbo cups are designed for emissions. The 6.2 uses a nozzle design similar to the 7.3. But the 6.5 nozzle resembles those found on small economy diesels over seas. Gm used the same nozzle (dn0sd304) on both the 6.5 n/a and turbo engines. The pintle design creates a slower, complete burn by flowing fuel more evenly across all stages of lift. The 6.2 pintle on the other hand increases flow more as the needle lifts. If you compare the pintles you'll find that the 6.5 has a flat spot machined into it that the 6.2 doesn't have. I think the 6.5 nozzle flow rate curve was the reason that the cup throat was opened on the turbo engines. Boost increased combustion speed and a bigger throat was needed to slow it back down to keep soot levels low. But there is a fine line because the more you slow it down the more NOx it will generate. Throat angle also plays a role but I have to physically measure that to see the difference if any between the cups. I believe cup volume is determined by engine displacement and static compression ratio. Different throat area and angles are used to adjust the combustion characteristics.


(6.5 stock - Marine - 6.2 long)

So I think the injector flow rate curve plays a big part and this diagram might help me explain that better.

As you can see the injection event starts BTDC and ends ATDC. Fuel injected BTDC is to start the combustion process and raise the chamber temperature and pressure. Fuel injected ATDC is used for additional combustion in the main cylinder. Injecting more of the fuel volume BTDC increases the amount of combustion in the chamber. This is exactly what the 6.5 pintle does. Increase fuel volume to performance levels and it could lead to a poor incomplete burn in the chamber, and lowered cup temperatures. I think to get better combustion a smaller amount of fuel should be injected BTDC then a large volume of fuel injected ATDC at peak cylinder/cup pressure. The larger pressure drop from smaller cups will help mix the air/fuel and a bigger combustion event will happen in the cylinder. With the flat spot machined into the 6.5 pintle this flow rate curve would be impossible to achieve. 6.2 pintles have a more desirable flow rate curve. But when increasing fuel volume they might become restrictive and need modifications. But since these are mechanical injectors there is only so much that can be done to them.

I believe timing, pump volume, injector flow rate curve, pop pressure, boost pressure, static compression, cup volume and throat size all have an effect on one another. You need the right combinations of all of them to get the desired combustion event. This is why n/a cups, 6.5 nozzles, and increased fuel and boost numbers don't play well together. I don't believe the "super swirl" theory. There might be a point where larger cups are needed but I don't think we are even close to those fuel volume numbers yet.

But at the end of the day there is only so much you can do with a idi and keep it drivable. And even finding the right combination will only get you so far. I just don't think we found the wall yet.

 

[WarWagon]

Don't forget the 6.5 heads also have a different injector angle than older 6.2 NA heads. The 1992+ design has same heads for 6.2 and 6.5 engines that were both in production for a time. Was the reason for the angle change just to clear the turbo manifold?

 

[Rockabillyrat]

I think the angle change and use of short injectors was done to help clearance for the turbo manifold. The long injectors will not clear the stock 6.5 turbo manifold. But that's fine with me. I wouldn't waste my time running that engineering master piece. I was going to run a sidewinder manifold.... But I don't like side mounts on v8's. So Im building a center mount set up for mine.

On a side note the short 6.2 nozzle might work also. But I haven't got one in my had yet to see what the flow rate curve will be. If anyone has any dn0sd253 nozzles I would love to have one.

 

[Will L.]

According to Gary Travinski (works with military/AM General) on thread about the new hmmwv called the NXT 360, the p400 in that can be ordered with up to 600 torque and 350 hp.
Now, seeing as @n8in8or hit some numbers -at his wheels -right there, it doesn’t surprise me.

And not to take away anything GEP or Nate did, but they have room for improvement, I’m sure. The fact that Nate did it on a budget much tighter than GEP (guessing, not sure- haha) just make me smile more for the Tahoe owner.

Anyways, look at the precups in those engines. Not exactly tiny from what I remember reading.

The 6.2 and the old 6.5 n/a precups being smaller relate to natural aspiration as Thefermanator mentioned.

I had already played with filler welding and opening up precups while in highschool shop class in ‘87. The mechanical teacher and welding teacher were next to each other and buddies. When inconel got brought up in welding, I siezed the opportunity and we did joint class for 2 weeks. The year before we already added a turbo to the welder teachers 6.2 Chevy. He got the GM dealer to give us a test 6.2 to teach diesel mechanics with. We played with precups- and didn’t build injectors to match each one. But what I learned then had me opening up precups to devastating sizes.

By all means, build a couple engines and just start swapping precups and testing. You may find something the rest of us missed.

And yes I agree that having the entire system matched properly will bring it to peak efficiency. But in an engine that is already known to have crap airflow, an under built fuel system, choke manifolds/ turbo/ exhaust, is keeping everything matching more important than making major air and fuel flowing improvments? Gotta say no.

If: your heads are well ported, some improvement on headers and turbo(and out) and you are flowing some descent volumes of fuel through the injectors- then you can be fighting some precup issues.

And to the injectors themselves, yeah, they limit horribly when pushing for power above 450 hp and 800 torque. Yes, thats where I know they can do. Going above that, I just used a cummins grid heater and replaced glowplugs with a custom adapter to hold another set of injectors being driven on a second ip out the front. Later, figured out to have the front ford ip location run the nitro propane into the gp holes.

I understand chasing it, and commend you for it, and for sharing. Especially for asking input. But not knowing what you are trying to improve on exactly, makes it hard. A more powerful engine over all, but at 1/4 throttle may burn less fuel than a stock one at 3/4 throttle and do same work per gallon. But unless you are maxing out the biggest part if diesel efficiency- turbo and related air flow- you might be spending dollars to save a dime. From the engines I went crazy with on the dragstrip, I can tell you there is a lot to be gained by lightening the rotataing mass. But cost? Haha.

It’s like roller rockers on the 6.5: do they help? Yes. Are they worth it? Well... maybe. Descent investment for minimum gain. So if everything is stock except roller rockers- complete waste of time and money. But if you already have improved turbo, exhaust, intake- maybe. Do you put around never getting above 2100 rpm? Is it a 140 hp generator engine? In a boat that runs natural aspiration? Horrible waste of $ in all those uses. In a truck or boat that lives at 2500 rpm or above already having kicked the gm turbo to the curb unless you have one on each side- yeah now they can reduce enough friction to let other things work more freely because now they may be where a lot of the drag is coming from. The drag the stock ones have is the same, but until it moves up on the list in the percentage category, it may or may not be worth it.

What power and mpg do you have now, and what are you shooting for?

You mentioned gain in power and mpg- so efficiency. But what is more important to you.

Can Nates Tahoe can do ok mpg compared to stock if he babies it? But he didn’t build it looking for mpg.
The NXT360 has greatly improved mpg over the previous version. But not if you get the 350/600 version.
My 6.5 drag truck didn’t get MPGs, It got GPMs. Well, actually it got over 2 Gs Per 1/4 M between the 2 fuels.

You need to choose which is more important a d know that your turbo and exhaust is correct for your usage first.

 

[n8in8or]

@Rockabillyrat and I have been talking offline and the thing that frustrates us both about the 6.2/6.5 platform is the lack of available data on what affect certain modifications have. There are a lot of theories, a lot of butt dyno experiences and a lot of stories of things that have been tried and succeeded or failed....but no data for people to see to support them. When I first got into the 6.5 I couldn’t believe how hard it was to find reliable info. I liked going to Heath’s site because there were power numbers associated with his combos.....now I know those numbers aren’t real and I’m glad I didn’t start chasing that dragon, but wouldn’t it be nice to have some combos with real dyno results available for the 6.5?

Luckily I went beyond Heath’s site and started hanging out on the forums and reading as many accounts as I could on what was working and what wasn’t. Even so, you had to really trust what people were saying and hear enough corraborating reports to believe what was fact and what was fiction. When I started building my combo, I decided that I really wanted to document what parts I had and then find out what it did in the end. Now I can confidently say what combination of parts will make 350hp and 600tq at the wheels (so far). But even so, there are some variables in the equation: my home-ported heads - how did those contribute to this combo? Did they help and if so, how much? What apsect of my porting did what it did? What about my header? Same questions. And even if it didn’t help power is it helping my combo survive because #8 cylinder is staying cooler?

But again, this is the power it’s making with this combo of parts, what if there are other changes that could be made that would improve that number even further? Conventional 6.5 wisdom does say to use larger pre-chamber openings when chasing power, but what if we’re wrong? I haven’t personally seen any hard data that supports this. It may be true, but again, data would be nice. There’s some info out there that suggests that this thinking is incorrect and may even be hurting power. I think it would be great to know that for sure, and I think that would be info we could all benefit from.

Luckily rockabillyrat (man you need a shorter handle, ha) and I don’t live TOO far apart, so doing some collaborative testing isn’t out of the realm of possibility. Our hope at some point is to get an engine on a dyno and spend a day or two with a bunch of different parts and see what effect those parts have on power. We’re still in the infancy of planning this, but at least for me, the idea is pretty exciting. Neither of us has an agenda (other than to make good power with the 6.5 platform) and neither of us has products that we are trying to sell, we just want to see some data and see if there are new things that can be tried for power. Testing on an engine dyno will make it a lot easier to do injector and even head & precup swaps, so hopefully we will be able to test a lot of different parts in a dyno session. We won’t be able to test all combos of course, but we should be able to test some of these injector pressure, pintle shape and precup size theories out on at least one engine combo. Who knows, maybe we will even be able to swap injection pumps out and see what effect these have on different fuel volumes?

I don’t really know what to expect from all of this, but the idea of actually testing them and having hard data from the tests is exciting I think.

To your point @Will L., this is going to be a power exploration for the most part, but hopefully with power there can also be some mileage benefits as well, but that will be much trickier to test as we won’t be able to test that on an engine dyno and we probably won’t be doing all of this part swapping on an actual truck.

Now I feel like I’m rambling....I just wanted to come on here to say that it’s true that some or all of these ideas may not pan out, but some of them might and if we do a good and thorough job of testing we will have the data to say yes or no for sure.

 

[ak diesel driver]

Can't wait to see the results!

 

[3500GMC]

"The long injectors will not clear the stock 6.5 turbo manifold. But that's fine with me."

Wasn't fine with me, that's why I made it work. Even with using wider angle 6.2 heads.

 

[Rockabillyrat]

Will L. You make a good point about HP and MPG. I should come the the realization that I really can't go for both on my build and will have to choose. Well it's not a hard choice, the kid in me just loves HP. My goal is to try and push HP as high as I can but still be 100% Streetable. If I could see MPG in the mid teens I would be completely happy with that.

I though alot about why GEP contuned to use the bigger cups and 304 nozzles. And the only thing I can think of is MPG. Alot of the Quadstar fans have reported 20+ MPG with his pump, turbo, and tunes. And if I remember correctly all of them have diamond cups and 6.5 injectors. His ds4 can push around 100cc/1000. GEP might have seen no reason to try and reengineer the injection system. Once they stepped up fueling with the 6033 pump they might have been happy enough with the HP and MPG numbers. I think they where more concerned with fixing the block and cooling issuse.

Doing all this injector/cup work on a stock engine might be a waste of time. There are so many other things that need to be fixed first on these platforms first. But n8in8tor is at the point where you have to start dialing every part of the system in to get over the next HP level. And I'm thankful he has joined me in this adventure. I'm really excited to have someome like him to work with on all of this.

When I first started getting into the 6.5 I too was a Heath believer. 500hp!! I mean he's in a magazine so it must be true.... But after spending time around the community I learned about all the smoke and mirrors. And boy is this platform full of them. Quadstar reports all of these gains but has yet to show any dyno number, or show the data logs. When I asked him why he said the dyno was a waste of time!! Again all smoke and mirrors. I'm not saying the guy can't write a tune or his turbos are junk. But I like numbers, facts, real data I can compare. He's a business owner and understand being a little hush hush about it. But it's time for a change. I'm not in this for the money. I just want to clear the smoke, break the mirrors and do some real testing and share all of it with the community. All of my theories are just that untill I prove them wrong or right. Maybe this whole thing is a waste of time. But not a single person has given me a solid piece of proof that it's not. So it's time to get dirty and do some real testing.

I've got some really exciting things planned. I've even think I found a way to tune a DB2 with a lab scope.

I hope everyone has a nice Father's day!

 

[Will L.]

That’s awesome you guys are close enough to work together. That would be so cool to see a complete flip of things. It’s like the crankshaft debate cast vs forged. There was evidence pointing toward both sides. Some folks still on opposite sides, mine- well only one style survives in top fuel...


@n8in8or It’s just a money thing why there isn’t that much dyno info. And the fact that you aren’t selling things is why you can’t pour money into the proof of a dyno. Say you sold custom parts like your header or you rebuilt and sold turbos. You could dyno your set up with a stock manifold and get the comparison, cost maybe $1500 counting labor. Then that gets paid for out of selling headers- But how many? Same for turbos.
Now if you just do 0-60 or 0-100 runs and maybe track mpg of 1 tank each way, that is much cheaper. But it isn’t documented unless a video- then that could be questioned just like people question a dyno run.
But those who believe the story and based on your results, some folks would buy from that.


Crossing my fingers one of you stumble on a $100 pickup with 6.2/6.5 parts in the bed. I really wish I had the big parts pile still to donate, unfortunately it all got donated long ago.


Wait, Labscope? That sounds like a dedicated thread itself full of wowed moments.