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+--- Thread: Prechamber Mod "Flame" Front (/showthread.php?tid=2169)
RE: Prechamber Mod "Flame" Front - ForcedInduction - 01-29-2011
(01-29-2011, 08:42 AM)yankneck696 Also, Hercules stated that on an otherwise stock engine, that chamfering the holes on the outside benefitted.A bell-mouth form will improve flow efficiency into any tube, its simply not cost-effective for a manufacturer to do that on a large scale production. Increasing flow efficiency is a good thing, increasing flow volume isn't (in this case).
Quote:In a carbeuretor, when you increase air volume, you need to change jets (as an example).A carb has no relation to a diesel. The jets are increased to allow the necessary amount of fuel to flow, otherwise they get a lean condition at high throttle.
RE: Prechamber Mod "Flame" Front - yankneck696 - 01-29-2011
<<Could a heavily modded engine benefit from chamfered AND enlarged PC holes, common sense would say yes to me. In a carbeuretor, when you increase air volume, you need to change jets (as an example).>>
That was the whole statement. Now, as injected fuel volume is increased & more air introduced, would not the chamfered & enlarged PC holes allow for better HP numbers? Wouldn't the larger orifices do a more efficient job being calibrated to the volumes changes? Kind of like changing the jets to allow more fuel in a carbeuretor with more airflow?
<<A bell-mouth form will improve flow efficiency into any tube, its simply not cost-effective for a manufacturer to do that on a large scale production. Increasing flow efficiency is a good thing, increasing flow volume isn't (in this case).>>
OK, I think we are all in agreement of the chamfering, then. Cool. That means that air is going in & fuel-air/possible combustion is comming out is more efficient. Now, again, with more volume of air & fuel, would not the smaller holes be a restriction? Would not the larger diameter in this instance lead to better clearing of the prechamber? Would it also bring the velocities & atomization back to comperable to factory, but more volume & get the same effects with more efficient HP gains without the lag in fuel ejection from the prechamber that might raise the EGTs (biggest enemy of diesels as far as I understand?
Let's take a garden hose with a an old time brass twist nozzle as an example. at a certain pressure & volume of water, you get the spray pattern that you want & when you turn off the valve, the water stops immediately (theoretical circumstances, I know) . Now, turn up the volume to that nozzle & it increases the pressure comming out. Fuel may be more atomized, but when you turn off the valve, there would be a certain ammount drizzling out of the nozzle. Put to diesel applications, that drizzle would lead to higher EGT' & unburned fuel (black smoke which is undesireable due to HP out the tailpipe?
Not arguing, but trying to understand better.
Ed
RE: Prechamber Mod "Flame" Front - ForcedInduction - 01-29-2011
(01-29-2011, 09:39 AM)yankneck696 That was the whole statement.It was not quoted as one because the two have no relation to each other.
RE: Prechamber Mod "Flame" Front - yankneck696 - 01-29-2011
What about the rest of the post? I think it might have merit towards what the discussion is all about. Please give your opinions.
Ed
RE: Prechamber Mod "Flame" Front - erling66 - 01-29-2011
(01-29-2011, 09:39 AM)yankneck696 <<Could a heavily modded engine benefit from chamfered AND enlarged PC holes, common sense would say yes to me. In a carbeuretor, when you increase air volume, you need to change jets (as an example).>>Why would you introduce more air to the PC? You already have enough for the pre ignition and the atomization of the fuel. The main combustion happens in the combustion chamber and you want more air there.
That was the whole statement. Now, as injected fuel volume is increased & more air introduced, would not the chamfered & enlarged PC holes allow for better HP numbers? Wouldn't the larger orifices do a more efficient job being calibrated to the volumes changes? Kind of like changing the jets to allow more fuel in a carbeuretor with more airflow?
(01-29-2011, 09:39 AM)yankneck696 <<A bell-mouth form will improve flow efficiency into any tube, its simply not cost-effective for a manufacturer to do that on a large scale production. Increasing flow efficiency is a good thing, increasing flow volume isn't (in this case).>>The small holes would be a restriction but you don't need more air in the PC so they are not.
OK, I think we are all in agreement of the chamfering, then. Cool. That means that air is going in & fuel-air/possible combustion is comming out is more efficient. Now, again, with more volume of air & fuel, would not the smaller holes be a restriction? Would not the larger diameter in this instance lead to better clearing of the prechamber? Would it also bring the velocities & atomization back to comperable to factory, but more volume & get the same effects with more efficient HP gains without the lag in fuel ejection from the prechamber that might raise the EGTs (biggest enemy of diesels as far as I understand?
The small(original) holes will not raise the EGT. Raised EGT is a result of increased fueling and insufficient amount of air in the combustion chamber(among other factors)
(01-29-2011, 09:39 AM)yankneck696 Let's take a garden hose with a an old time brass twist nozzle as an example. at a certain pressure & volume of water, you get the spray pattern that you want & when you turn off the valve, the water stops immediately (theoretical circumstances, I know) . Now, turn up the volume to that nozzle & it increases the pressure comming out. Fuel may be more atomized, but when you turn off the valve, there would be a certain ammount drizzling out of the nozzle. Put to diesel applications, that drizzle would lead to higher EGT' & unburned fuel (black smoke which is undesireable due to HP out the tailpipe?The last example makes no sense to me. maybe someone else can explain
Not arguing, but trying to understand better.
Ed
RE: Prechamber Mod "Flame" Front - OM616 - 01-29-2011
(01-29-2011, 10:19 AM)yankneck696 What about the rest of the post? I think it might have merit towards what the discussion is all about. Please give your opinions.
Ed
You got it!! Should win a prize of some sort I think.
I think it is funny that the concept is condemned as blasphemy, and yet no one on the nay side of the discussion will comment on the report (from a member other than myself), of improved performance, reduced smoke, faster spool, quick starts, etc., on basically a stock engine after the holes were opened up.
For the MB worshipers, why did MB increase the holes in the PC?
_____________________________________________________________
I didn't forget the gasket, the piston sticks up from the deck a bit, so to simplify, I went a bit generous with the TDC volume guestamate.
The numbers are just numbers. No calculations implied by them. This isn't my first rodeo. I am actually very deliberate regarding what I post, or do not, in some cases.
Remember this is a fun theoretical discussion, intended for entertainment, to get people thinking about things that they normally would not, and I can see that is what is taking place, we are not trying to put a child on mars or anything.
RE: Prechamber Mod "Flame" Front - OM616 - 01-29-2011
(01-29-2011, 08:22 AM)ForcedInduction(01-28-2011, 01:06 PM)OM616 I agree that smaller holes = quieter operation, I am interested in more power.
Enlarging the holes will not do that..
Why did MB inlarge the PC holes then?
(01-28-2011, 01:06 PM)OM616 If the size of the holes were increased to allow more air into the prechamber, the prechamber air temperature, (before, and at the time of injection), would be higher from the additional pressure, (increasing the conditioning of the fuel), aiding in combustion.
(01-29-2011, 08:22 AM)ForcedInduction Inside the prechamber, where the increased combustion pressure is completely wasted on immovable surfaces..
The higher pressure will increase the velocity of the gasses from the PC.
(01-28-2011, 01:06 PM)OM616 Also, if more air is allowed to enter the prechamber, then the pressure differential during compression would be lower, if the prechamber pressure is always higher than the cylinder pressure during combustion with the small holes, (high pressure differential during compression), then with a lower compression pressure differential, the prechamber combustion pressure would be even higher than the cylinder pressure, blowing out its contents even faster and with more vigor.
(01-29-2011, 08:22 AM)ForcedInduction Reducing the amount of fuel ejected into the cylinder.
?
(01-28-2011, 01:06 PM)OM616 blowing out its contents even faster and with more vigor.
(01-29-2011, 08:22 AM)ForcedInduction It would actually blow out slower with less fuel reaching the main combustion chamber. Larger orifice = lower velocity.
See above
(01-28-2011, 01:06 PM)OM616 The faster the engine is running the less time there is for air to make it into the prechamber, lowering the prechamber pressure and reducing the amount of vigor. Less vigor, bad, more vigor, good.
(01-29-2011, 08:22 AM)ForcedInduction Nope. The less air in the prechamber the less fuel wasted burning inside a non-movable chamber.
See above
(01-28-2011, 01:06 PM)OM616 If more air is allowed to flow into the prechamber then the swirl in the prechamber will be increased
(01-29-2011, 08:22 AM)ForcedInduction No. Swirl would be reduced, remember; Larger orifice = lower velocity.
Swirl is generated from gasses being expelled from the burn tube and then being deflected off the ball.
(01-28-2011, 01:06 PM)OM616 If larger elements are used, then the length of time that the fuel is injected in is reduced, and the holes will need to flow at an increased rate to keep up.
(01-29-2011, 08:22 AM)ForcedInduction Also no. Injection time has no bearing on swirl or atomization. Fuel volume is what necessitates larger orifices.
But it does have bearing on the rate of pressure rise.
(01-28-2011, 01:06 PM)OM616 any extra air that is allowed to enter the prechamber, and is not used up, will be expelled
(01-29-2011, 08:22 AM)ForcedInduction Such a condition would defeat the entire purpose of a prechamber.
There is never leftover air in the prechamber (except possibly at idle).
So it hapens already
(01-28-2011, 01:06 PM)OM616 The closer the prechamber and cylinder pressures are during compression, the less energy that is used to raise the prechamber pressure above the cylinder pressure during combustion.
(01-29-2011, 08:22 AM)ForcedInduction Incorrect. More energy would be wasted pushing on solid walls.
The larger holes will flow more in less time so extra energy will blow out the larger holes, and that is the point.
(01-28-2011, 01:06 PM)OM616 All in all, I see larger holes as a win win.
(01-29-2011, 08:22 AM)ForcedInduction If you're making over 100hp/cyl..
Agine, the engine needs to run well at power out puts and speeds well bellow full power, and they apparently do with larger holes.
(01-28-2011, 01:06 PM)OM616 And the reports, from other members besides me, support larger holes.
(01-29-2011, 08:22 AM)ForcedInduction Except the ones that do it correctly are making 100hp/L on top of what any OM61x has ever achieved. Even the "245hp" Norwegian 240D doesn't meet the need for modifying the prechambers...
I did not read anything about the prechambers in the information regarding the 240D. But lets say that he did not touch them, that does not mean that there is not some efficiency that could be had from scaling the prechamber to the higher output.
(01-28-2011, 01:06 PM)OM616 The increased air entering the prechamber will create a stronger swirl improving the mix of gasses and fuel.
(01-29-2011, 08:22 AM)ForcedInduction Incorrect. The air will be higher density and lower velocity, which will both work to reduce swirl..
The diameter of the burn tube stays the same, more air flowing out of it in the same period of time = faster flow that hits the ball and induces a stronger swirl.
(01-28-2011, 01:06 PM)OM616 Due to the lower cylinder / prechamber pressure differential, the result of larger holes, more pressure will be exerted on the piston sooner,
Corrected.
RE: Prechamber Mod "Flame" Front - Hercules - 01-30-2011
What prechamber best to mod. (my opinion )1984Ca.or 1985Ca.and Fed. My reasoning,this information from 1984 Mbz new modler year book. Title: prechamber,to reduce smoke emissions at partial load, the prechamber has been modified as follows:
Nozzle seat 1 mm deeper
Bore in upper half enlarged from 8 mm to 14 mm
Production phase-in:
California version at start of model year.
Will be gradually phased-in on Fed.version engines. Pertaining to 617.95 engine
Have cleaned,reset,or ( rebuilt) hundreds of Mbz nozzles,these gave the least amount of troubles.
Also set pressures at 950lbs +0- best performance,smoke levels.
RE: Prechamber Mod "Flame" Front - tomnik - 01-30-2011
these are exactly the MB internal instructions (Europe/Germany) to mod the PC in very hard cases that customers claim idle and partial smoke.
(01-30-2011, 05:28 AM)Hercules What prechamber best to mod. (my opinion )1984Ca.or 1985Ca.and Fed. My reasoning,this information from 1984 Mbz new modler year book. Title: prechamber,to reduce smoke emissions at partial load, the prechamber has been modified as follows:
Nozzle seat 1 mm deeper
Bore in upper half enlarged from 8 mm to 14 mm
RE: Prechamber Mod "Flame" Front - erling66 - 01-30-2011
(01-29-2011, 05:11 PM)OM616 Remember this is a fun theoretical discussion, intended for entertainment, to get people thinking about things that they normally would not, and I can see that is what is taking place, we are not trying to put a child on mars or anything.
Hi OM616
Your tread is great, makes us think
A world without experimenting would be boring, we would still be driving with Rudolf Diesels first engine and Forced would argue that his engine works fine on Peanut oil so why try the new petro diesel fuelAnd one question for you: Have you tried(or thought about) to make the holes as large as possible and only leave enough metal to keep the cup tip in place?
According to your theory, this should be even better, maximum air flow in and little restriction out of the PC. And minimum pressure difference.
RE: Prechamber Mod "Flame" Front - OM616 - 01-30-2011
I’m glad to here that people are having fun. The ideas that have been shared so far have been fantastic, and as a result, I am going to reduce the dia of the burn tube its self, just a little bit, in my custom designed PC to increase swirl. I’ll do a couple of sizes as I would be able to increase the ID easy enough if the ideal size is larger than the smallest size I try.
For my next mod I will machine a slot from the left hole across to the right hole, making a mouth.
When I look at the area of the holes of a 60X PC compared to the cylinder displacement, and then look at the 61X PC hole area compared to the 61X cylinder displacement, I see that even with the holes opened up, I'm still on the concretive side. When I look at the area of Jeemu's modded PCs compared to the cylinder displacement, The slot looks good.
I will have some more numbers to post later that pertain to laminar flow of an orifice the size of the PC holes. The point being that hole size makes a difference. 8 small holes will flow differently than three big holes of a total area = to the total area of the 8 small holes. (poorly worded I know).
__________________________
Hercules,
Great info, I think Tomnik posted similar, (if not the exact), MB PC mods in my other thread. I was waiting to bring them over hear until the idea that MB sanctioned changes was officially challenged. If it hasn’t been challenged by now, I don’t think it will be.
There was another one for the OM615 to address complaints of low power, I believe it said to open up the burn holes in that one, but I have to look again to be sure. I have incorporated those changes into my PC design.
RE: Prechamber Mod "Flame" Front - josha37 - 01-30-2011
oh oh oh I want less smoke and more power! sign me up.
RE: Prechamber Mod "Flame" Front - Biohazard - 01-30-2011
So this has me intruiged. I put in a thicker headgasket to drop my compression, and my car is smoking pretty bad at idle when it's cold. Do you think putting in a thinner PC shim (has the 2mm one now) and tapering the holes will help keep it from smoking as much? From what I'm gathering reading through this, I think it will. I have another set of pre-chambers, just need to get the right tool and those taper bits.
Please, keep up the good work and quality discussion! It's nice to see an actual discussion and not just mindless arguing.
Also, please feel free to comment on my question as well.(01-29-2011, 05:11 PM)OM616 we are not trying to put a child on mars or anything.
On a side note, we're definitely going to need bigger prechambers to get a kid to Mars...
RE: Prechamber Mod "Flame" Front - OM616 - 01-30-2011
(01-30-2011, 11:21 AM)josha37 oh oh oh I want less smoke and more power! sign me up.
Less smoke??..... From what you have been tilling me you would probably be happy with less of a soot trail out the back!! LOL If you can get back to just smoke I think that would be progress in the right direction.
RE: Prechamber Mod "Flame" Front - josha37 - 01-30-2011
yea... i remember what smoke was like... can you see the side of my car from the front passenger wheel back? (the exhaust exits there)
RE: Prechamber Mod "Flame" Front - dieselboy - 01-30-2011
(01-30-2011, 02:15 PM)josha37 yea... i remember what smoke was like... can you see the side of my car from the front passenger wheel back? (the exhaust exits there)
Hahaha awesome. I worked on a ship that was like that. Lcs1 the freedom had side exhausts for some reason and the crew called them the "war stripes" lol.
The problem is that you will never be 100% smoke free if you want power. You will either get smoke on the bottom end or have a little on top from timing.
It can be greatly reduced by the Alda, timing, boost, and fuel rate, were hoping that this precup mod actually works. And helps with the smoke a little an of course more power.
The thing I'm seeing is that there are a few people that have actually gone this route. Jeemu and om616 both "say" that it was a improvement over stock. But need you remember that they both don't have stock pumps and are putting out 3X the Orig power. Now if I didn't just do the head on my om617 the week before this started I would have been all for opening up the precups a little.
RE: Prechamber Mod "Flame" Front - josha37 - 01-30-2011
I think my pump might be flowing a bit more fuel than stock, im blowing smoke even in the midrange with 15 lbs of manifold pressure. im willing to bet the stock intake ports are a bit restrictive so im not getting as much benefit as i could be from the added air flow but at any rate im sure opening up the prechamber will assist in getting some of this fuel to burn.
RE: Prechamber Mod "Flame" Front - dieselboy - 01-30-2011
I get smoke in the high revs with 20psi. It because of the long injection time though.
RE: Prechamber Mod "Flame" Front - DeliveryValve - 01-30-2011
(01-23-2011, 11:11 AM)ForcedInduction(01-22-2011, 05:52 PM)DeliveryValve ...
Quote:My understanding is the stock Prechambers are just fine for higher HP output and any modification would hinder and not improve performance.They are, you're correct.
....
[(01-29-2011, 09:11 AM)ForcedInduction [quote='yankneck696' pid='23822' dateline='1296308579']Also, Hercules stated that on an otherwise stock engine, that chamfering the holes on the outside benefitted.A bell-mouth form will improve flow efficiency into any tube, its simply not cost-effective for a manufacturer to do that on a large scale production. Increasing flow efficiency is a good thing, increasing flow volume isn't (in this case).
...
Holy Shi-at. Am I reading that FI is moving from the hardline stance and states a certain modification of a pre-chamber will be a benefit!?
(01-30-2011, 05:28 AM)Hercules What prechamber best to mod. (my opinion )1984Ca.or 1985Ca.and Fed. My reasoning,this information from 1984 Mbz new modler year book. Title: prechamber,to reduce smoke emissions at partial load, the prechamber has been modified as follows:
Nozzle seat 1 mm deeper
Bore in upper half enlarged from 8 mm to 14 mm
Production phase-in:
California version at start of model year.
Will be gradually phased-in on Fed.version engines. Pertaining to 617.95 engine
Have cleaned,reset,or ( rebuilt) hundreds of Mbz nozzles,these gave the least amount of troubles.
Also set pressures at 950lbs +0- best performance,smoke levels.
Interesting that you posted this. I always wondered what were the differences when I first saw it. It has a distinctive "open" neck. As opposed to the previous "collared" neck.
Here is a shot of a couple of pre-chambers one from a model year 1984 Cali 617 and the other from a Model year 1983 617 motor. Same number 617/03 stamped on both.
RE: Prechamber Mod "Flame" Front - josha37 - 01-30-2011
AH!!! i heart pictures.. thank you
I have smoke on the top end as well but not nearly as much when im down around 10-15 psi or below.
RE: Prechamber Mod "Flame" Front - ForcedInduction - 01-30-2011
(01-29-2011, 05:11 PM)OM616 I think it is funny that the concept is condemned as blasphemyPerhaps you should understand the discussion before using words with a definition that have no relation to what you are describing.
Quote:, and yet no one on the nay side of the discussion will comment on the report (from a member other than myself), of improved performance, reduced smoke, faster spool, quick starts, etc., on basically a stock engine after the holes were opened up.Thats because there isn't. All you've got is anecdotal text, you haven't provided any form of empirical evidence to support your claims.
Quote:For the MB worshipers, why did MB increase the holes in the PC?Technology. They understood their design was flawed so they updated it. In the 21 years since the only other changes they made to the design was to angle the injector and rotate the ball.
Quote:I didn't forget the gasket, the piston sticks up from the deck a bit, so to simplify, I went a bit generous with the TDC volume guestamate.Do you have any actual data?
Quote:Remember this is a fun theoretical discussion, intended for entertainmentIncorrect. It is a technical discussion that could be interpreted by non-current members as factual data when in fact it isn't.
Quote:The higher pressure will increase the velocity of the gasses from the PC.Incorrect. Gas velocity means nothing, you're reducing the volume of fuel used to do work in the cylinder.
Quote:Swirl is generated from gasses being expelled from the burn tube and then being deflected off the ball.Incorrect.
Quote:But it does have bearing on the rate of pressure rise.Also incorrect. The difference in PC pressure rise between stock and 100hp/L is zero because the inlet orifices will always, by definition, limit the amount of air allowed into the PC. That means the available air to burn will always be the same at a given RPM & boost pressure no matter the injected quantity.
Quote:So it hapens alreadyNo.
Quote:The larger holes will flow more in less time so extra energy will blow out the larger holes, and that is the point.Incorrect.
Quote:Agine, the engine needs to run well at power out puts and speeds well bellow full power, and they apparently do with larger holes.Not based on actual data.
Quote:I did not read anything about the prechambers in the information regarding the 240D. But lets say that he did not touch them, that does not mean that there is not some efficiency that could be had from scaling the prechamber to the higher output.Correct. He would lose significant low-end combustion efficiency which is required to spool up such an extremely oversized turbo.
Quote:The diameter of the burn tube stays the same, more air flowing out of it in the same period of time = faster flow that hits the ball and induces a stronger swirl.Incorrect. Lets repeat for the fourth time; Larger orifice=lower velocity.
Quote:Falsified.Corrected. Please don't post false information and attempt to present it as accurate, thats known as trolling.
(01-30-2011, 05:28 AM)Hercules What prechamber best to mod. (my opinion )1984Ca.or 1985Ca.and Fed.There is no difference between the two, they are the same part number.
(01-30-2011, 11:21 AM)josha37 oh oh oh I want less smoke and more power! indoctrinate me.
Quote:I think my pump might be flowing a bit more fuel than stock, im blowing smoke even in the midrange with 15 lbs of manifold pressure.Thats only because your non-turbo camshaft has valve overlap. Its allowing exhaust to be pushed back into the cylinder.
(01-30-2011, 04:41 PM)DeliveryValve Holy Shi-at. Am I reading that FI is moving from the hardline stance and states a certain modification of a pre-chamber will be a benefit!?Increasing fluid flow efficiency is not pseudoscience.
(01-30-2011, 04:41 PM)DeliveryValve Interesting that you posted this. I always wondered what were the differences when I first saw it. It has a distinctive "open" neck. As opposed to the previous "collared" neck.The larger diameter is to reduce carbon buildup between the injector heat shield and PC which affects long-term emissions. It has no effect on performance.
Here is a shot of a couple of pre-chambers one from a model year 1984 Cali 617 and the other from a Model year 1983 617 motor. Same number 617/03 stamped on both.
RE: Prechamber Mod "Flame" Front - OM616 - 01-31-2011
(01-30-2011, 04:41 PM)DeliveryValve(01-23-2011, 11:11 AM)ForcedInduction(01-22-2011, 05:52 PM)DeliveryValve ...
Quote:My understanding is the stock Prechambers are just fine for higher HP output and any modification would hinder and not improve performance.They are, you're correct.
....
[(01-29-2011, 09:11 AM)ForcedInduction [quote='yankneck696' pid='23822' dateline='1296308579']Also, Hercules stated that on an otherwise stock engine, that chamfering the holes on the outside benefitted.A bell-mouth form will improve flow efficiency into any tube, its simply not cost-effective for a manufacturer to do that on a large scale production. Increasing flow efficiency is a good thing, increasing flow volume isn't (in this case).
...
Holy Shi-at. Am I reading that FI is moving from the hardline stance and states a certain modification of a pre-chamber will be a benefit!?
I think it is safe to say no to that one.
We are all undocumented, uninformed, lying, hacks according to him, oh and I’m a Troll too. Not sure about everyone else, but I'm OK with that.
RE: Prechamber Mod "Flame" Front - Hercules - 01-31-2011
(01-30-2011, 11:24 PM)ForcedInductionMost often reason for replacing pre 84 injector( overheating),sunken distorted injector tip end,and or pintle bluing(overheating)distortion again,sticking causing poor spray pattern.Cause,Heat transfer to tip from seal being to close to pintle end. Enlarging hole and seal also gave cooling effect,unshrouding,allowing some cooling from incoming fresh fuel and air. After the changes in prechamber and seal, these conditions were seldom if ever seen again. Can these conditions cause reduced performance and higher emissions or both? Mbz made the changes!!(01-29-2011, 05:11 PM)OM616 I think it is funny that the concept is condemned as blasphemyPerhaps you should understand the discussion before using words with a definition that have no relation to what you are describing.
Quote:, and yet no one on the nay side of the discussion will comment on the report (from a member other than myself), of improved performance, reduced smoke, faster spool, quick starts, etc., on basically a stock engine after the holes were opened up.Thats because there isn't. All you've got is anecdotal text, you haven't provided any form of empirical evidence to support your claims.
Quote:For the MB worshipers, why did MB increase the holes in the PC?Technology. They understood their design was flawed so they updated it. In the 21 years since the only other changes they made to the design was to angle the injector and rotate the ball.
Quote:I didn't forget the gasket, the piston sticks up from the deck a bit, so to simplify, I went a bit generous with the TDC volume guestamate.Do you have any actual data?
Quote:Remember this is a fun theoretical discussion, intended for entertainmentIncorrect. It is a technical discussion that could be interpreted by non-current members as factual data when in fact it isn't.
Quote:The higher pressure will increase the velocity of the gasses from the PC.Incorrect. Gas velocity means nothing, you're reducing the volume of fuel used to do work in the cylinder.
Quote:Swirl is generated from gasses being expelled from the burn tube and then being deflected off the ball.Incorrect.
Quote:But it does have bearing on the rate of pressure rise.Also incorrect. The difference in PC pressure rise between stock and 100hp/L is zero because the inlet orifices will always, by definition, limit the amount of air allowed into the PC. That means the available air to burn will always be the same at a given RPM & boost pressure no matter the injected quantity.
Quote:So it hapens alreadyNo.
Quote:The larger holes will flow more in less time so extra energy will blow out the larger holes, and that is the point.Incorrect.
Quote:Agine, the engine needs to run well at power out puts and speeds well bellow full power, and they apparently do with larger holes.Not based on actual data.
Quote:I did not read anything about the prechambers in the information regarding the 240D. But lets say that he did not touch them, that does not mean that there is not some efficiency that could be had from scaling the prechamber to the higher output.Correct. He would lose significant low-end combustion efficiency which is required to spool up such an extremely oversized turbo.
Quote:The diameter of the burn tube stays the same, more air flowing out of it in the same period of time = faster flow that hits the ball and induces a stronger swirl.Incorrect. Lets repeat for the fourth time; Larger orifice=lower velocity.
Quote:Falsified.Corrected. Please don't post false information and attempt to present it as accurate, thats known as trolling.
(01-30-2011, 05:28 AM)Hercules What prechamber best to mod. (my opinion )1984Ca.or 1985Ca.and Fed.There is no difference between the two, they are the same part number.
(01-30-2011, 11:21 AM)josha37 oh oh oh I want less smoke and more power! indoctrinate me.
Quote:I think my pump might be flowing a bit more fuel than stock, im blowing smoke even in the midrange with 15 lbs of manifold pressure.Thats only because your non-turbo camshaft has valve overlap. Its allowing exhaust to be pushed back into the cylinder.
(01-30-2011, 04:41 PM)DeliveryValve Holy Shi-at. Am I reading that FI is moving from the hardline stance and states a certain modification of a pre-chamber will be a benefit!?Increasing fluid flow efficiency is not pseudoscience.
(01-30-2011, 04:41 PM)DeliveryValve Interesting that you posted this. I always wondered what were the differences when I first saw it. It has a distinctive "open" neck. As opposed to the previous "collared" neck.The larger diameter is to reduce carbon buildup between the injector heat shield and PC which affects long-term emissions. It has no effect on performance.
Here is a shot of a couple of pre-chambers one from a model year 1984 Cali 617 and the other from a Model year 1983 617 motor. Same number 617/03 stamped on both.
RE: Prechamber Mod "Flame" Front - 300D50 - 01-31-2011
If your spray pattern is whack, and you have carbon buildup, yeah, negative performance will occur.
RE: Prechamber Mod "Flame" Front - josha37 - 01-31-2011
"Thats only because your non-turbo camshaft has valve overlap. Its allowing exhaust to be pushed back into the cylinder"
Sad.. seriously though how much overlap could the cam in these have? anyone have any cam degree info?
RE: Prechamber Mod "Flame" Front - ForcedInduction - 01-31-2011
Holy crap, don't quote an entire friggin post!
(01-31-2011, 01:36 AM)Hercules Most often reason for replacing pre 84 injector( overheating),sunken distorted injector tip end,and or pintle bluing(overheating)distortion again,sticking causing poor spray pattern.Cause,Heat transfer to tip from seal being to close to pintle end.Using the correct (small opening) crush seal solves that.
Quote:After the changes in prechamber and seal, these conditions were seldom if ever seen again.How was it never seen again when it didn't happen to start with? The 100,000 617a's made from 79-84 have managed to survive very well without any need for retrofit.
Quote:Sad.. seriously though how much overlap could the cam in these have? anyone have any cam degree info?
RE: Prechamber Mod "Flame" Front - josha37 - 01-31-2011
Leave it to the germans to complicate a cam card... either i am having trouble going from charts with only tdc values or the 616 has zero valve overlap. exhaust closes 14 degrees before and intake opens 11 after so that would be negative 25 degrees of overlap? basically?
RE: Prechamber Mod "Flame" Front - erling66 - 01-31-2011
I don't have any 61X engines(only 606) so I can't take measurements, but if that cam card is correct, It is easy to see where you can gain power from a 61X.
Maybe Forced can teach us amateurs how to read his cam card?
RE: Prechamber Mod "Flame" Front - Hercules - 01-31-2011
(01-31-2011, 02:10 AM)ForcedInduction Holy crap, don't quote an entire friggin post!Was not a matter of survival,but of reducing smoke emissions.
(01-31-2011, 01:36 AM)Hercules Most often reason for replacing pre 84 injector( overheating),sunken distorted injector tip end,and or pintle bluing(overheating)distortion again,sticking causing poor spray pattern.Cause,Heat transfer to tip from seal being to close to pintle end.Using the correct (small opening) crush seal solves that.
Quote:After the changes in prechamber and seal, these conditions were seldom if ever seen again.How was it never seen again when it didn't happen to start with? The 100,000 617a's made from 79-84 have managed to survive very well without any need for retrofit.
Quote:Sad.. seriously though how much overlap could the cam in these have? anyone have any cam degree info?
Mbz thought it enough problem to make the change,But what do they know any way??
RE: Prechamber Mod "Flame" Front - OM616 - 01-31-2011
(01-31-2011, 02:53 PM)Hercules Was not a matter of survival,but of reducing smoke emissions.
Mbz thought it enough problem to make the change,But what do they know any way??
IMO all MB was ever worried about was emissions. They designed a system that burnt as little fuel as possible, hence the small elements. Increasing any one of the variables in the fuel system without equally massaging the others is like doing half the job so to speak, or crutching it.
One thing can be safely said, they were not out to build a muscle car when they designed the 616.
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Just a quick thought given the latest amendment to the rules, when everyone feels that this discussion has gone as far as it can go, is there any interest in a similar discussion concept regarding valve train? I know there are threads here and there, but thought I would ask.
RE: Prechamber Mod "Flame" Front - yankneck696 - 01-31-2011
Sure..... Should be alot easier with the changes.Ed
RE: Prechamber Mod "Flame" Front - OM616 - 01-31-2011
As promised, I prepared some flow numbers, (based on a reference text for design flow guidelines), and I must say that I am surprised as to what the results were.
The reference chart has sharp edged orifice diameters and pressures, with SCFM amounts for a diameter at different pressures. I had a reference text at one time that had a formula that you could plug in an area, pressure differential, temp of air, and depth of the orifice, and it would give you the flow rate +- a touch. Not absolute, but would give you an idea if the design was in the ball park for the application. After the move I found some stuff, and lost some stuff.
Any way, I took a .125 Inch Dia. (This is America so inches rules the day LOL), and found the area of the diameter, .0122716 sqin.
I then multiplied that area X 4 holes to get a total area of .0490864 sqin.
I then reversed the process and found the single diameter that has the area of all four .125 dia holes (.0490864), and the single hole size is .2499966 inch diameter.
At 100 psi the chart said that a .125 sharp edged orifice will flow 26 SCFM, X 4 holes = 104 SCFM (actual about 75%)
At 100 psi the chart said that a .250 sharp edged orifice will flow 104 SCFM (actual about 75%)
I must say that I am surprised to see that they flow the same. There is not a consideration for length, like a tube, but the wall thickness of the PC is not much, (it may be a ratio of a percentage of the diameter sort of thing). I really like Hercules approach of tapering his holes which thins the tubular portion of the hole as well as funnels in air and creates a rapid pressure drop when the gasses are expelled from the PC.
Perhaps some one more knowledgeable can comment on the flow math. I thought there would be more of a loss with the smaller holes.
RE: Prechamber Mod "Flame" Front - winmutt - 02-01-2011
Instead of making the holes bigger it sounds like adding one or 2 might be preferred. Does anyone have any pictures or schematics of other (non mbz) prechambers?
RE: Prechamber Mod "Flame" Front - OM616 - 02-01-2011
(02-01-2011, 09:18 AM)winmutt Instead of making the holes bigger it sounds like adding one or 2 might be preferred. Does anyone have any pictures or schematics of other (non mbz) prechambers?
The more examples to reference the better.
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I am more of a believer in physical testing than paper testing, so I have spent 90% of my time learning how to build prototypes and models that I can actually test, instead of learning all the complex math. Don't misunderstand that statement, we need each other so no dis was implied, just pointing out one of my week areas.
The flow tests that I have done of various pieces parts, (not PCs) showed that 1 large hole will flow more than 4 holes, (at the same pressure), that have a total area equal to the 1 large hole, there are differences in velocity of course. The chart I referenced gave a constant 25% loss for all the hole sizes, where the other formula I had at one time would calculate the loss specific to the hole area and its depth.
I did do a flow measurement test with the stock PC I have, (went up to 1000 psi), but I did not mod one to retest while I was there, and that is where my notes are.
My point to the large hole small hole flow differences was that you do not have to open a hole up very much to get a large change in area.
After looking at the hole area to cylinder displacement ratios, I can see that MB did learn something from the past and increased the total hole area and decreased the cylinder displacement for the 60X engines.
I still need to CC the 61X prechamber I have, but if the 60X prechamber has the same volume, then it is an even larger percentage of the total combustion chamber area in the 60X engines.
RE: Prechamber Mod "Flame" Front - ForcedInduction - 02-01-2011
You still don't grasp the knowledge that higher flow into the PC is not good.
RE: Prechamber Mod "Flame" Front - winmutt - 02-01-2011
(02-01-2011, 12:52 PM)ForcedInduction You still don't grasp the knowledge that higher flow into the PC is not good.
I certainly get it. Dispersement is more important than flow here. If anything more flow with same or less dispersement is bad.
RE: Prechamber Mod "Flame" Front - OM616 - 02-03-2011
I been meaning to post this thought, but kept forgetting to.
Regarding a conical entrance to the PC, I am wondering if the tapered hole would act like the first half of a two-stroke expansion chamber?
The wall thickness is very thin, but if everything was in proportion, I am wondering if the expanding gasses flowing out the tapered side would create an even lower pressure on the PC side of the hole?
RE: Prechamber Mod "Flame" Front - jeemu - 02-04-2011
Hmm. Bigger elements, bigger holes on prechamber = faster, shorter = better
Been there done that and works fine
RE: Prechamber Mod "Flame" Front - ForcedInduction - 02-04-2011
(02-04-2011, 04:27 PM)jeemu Hmm. Bigger elements, bigger holes on prechamber = faster, shorter = betterFlawed logic.
RE: Prechamber Mod "Flame" Front - dieselboy - 02-04-2011
(02-04-2011, 06:39 PM)ForcedInduction(02-04-2011, 04:27 PM)jeemu Hmm. Bigger elements, bigger holes on prechamber = faster, shorter = betterFlawed logic.
Yet he has proven it works.
RE: Prechamber Mod "Flame" Front - OM616 - 02-04-2011
(02-04-2011, 04:27 PM)jeemu Hmm. Bigger elements, bigger holes on prechamber = faster, shorter = better
Been there done that and works fine
It is nice to have ideas confirmed by someone that has done it and lived to tell the tail.
Many thanks for sharing your work.
RE: Prechamber Mod "Flame" Front - yankneck696 - 02-04-2011
(02-04-2011, 06:53 PM)dieselboy(02-04-2011, 06:39 PM)ForcedInduction(02-04-2011, 04:27 PM)jeemu Hmm. Bigger elements, bigger holes on prechamber = faster, shorter = betterFlawed logic.
Yet he has proven it works.
And has WAY more HP & torque than anyone in this hemisphere.
Ed
RE: Prechamber Mod "Flame" Front - OM616 - 02-04-2011
Came accros this today
RE: Prechamber Mod "Flame" Front - 300D50 - 02-05-2011
Hard to read those, care to repost a larger version?
RE: Prechamber Mod "Flame" Front - ForcedInduction - 02-05-2011
(02-04-2011, 06:53 PM)dieselboy Yet he has proven it works.
Where? I haven't seen anything but theoretical math and anecdotes. No dyno sheets to be seen.
I find it hard to believe that $75 and 2 hours is such a budget/time hindrance to adequately documenting major changes. If I can fit it into my budget and you have enough spare cash to afford a myna pump, there really isn't an excuse.
Quote:And has WAY more HP & torque than anyone in this hemisphere.That only means he is injecting more fuel.
Quote:Came accros this todayThe precup design has little in common with Mercedes' design.
RE: Prechamber Mod "Flame" Front - OM616 - 02-05-2011
(02-05-2011, 06:37 AM)ForcedInduction Where? I haven't seen anything but theoretical math and anecdotes. No dyno sheets to be seen.
I find it hard to believe that $75 and 2 hours is such a budget/time hindrance to adequately documenting major changes. If I can fit it into my budget and you have enough spare cash to afford a myna pump, there really isn't an excuse.
Implying that the members that posted information that you disagree with are liars is nothing but confrontational. If we can not trust what a member says, then what is the point. I mean heck, anyone that has any skill with a graphics program can create a dyno sheet that supports anything.
I say enough. Statements that contradict solely for the sake of contradiction are aggressive, and deter members from posting. Unless you have something relevant to "CONTRIBUTE" to a thread, don't.
(02-05-2011, 01:50 AM)300D50 Hard to read those, care to repost a larger version?
Tried, I can't attach a larger file. Magnifying glass perhaps? It doesn’t have any information in the text anyway. It is just another Prechamber design to ponder.
RE: Prechamber Mod "Flame" Front - willbhere4u - 02-05-2011
I'm not touching this one with a 10ft pole!
But the way to prove it works is to dyno before and after to see the power differences at said rpm/load! With no other mods besides swapping the modified prechamber's! theirs some thing we can all agree on!
RE: Prechamber Mod "Flame" Front - jeemu - 02-05-2011
I know that i need those modified chambers. Those not there just for fun.
And yes its been dynod. Actually my engine is dyno every time when done changes. Thats why i have differend nozzle open pressure, pump timing, etc than others.
I have no need to prove anything to anybody. Do this just my self.
RE: Prechamber Mod "Flame" Front - Volker407 - 02-05-2011
(01-29-2011, 08:22 AM)ForcedInduction(01-28-2011, 02:59 PM)Volker407 concerning the atomization the common rail DI is better than IDINot for those up to the current generation. Current pressures are still too low to vaporize fuel to the extent a prechamber can.
They haven't even caught up to the pressures generated by early-90's unit injection systems. Thats why VW went with unit injectors (pumpe duse) in the previous generation of TDI. The primary reason for common rail today is unit injectors can't have multiple injection events beyond the compression/power strokes. Which is why manufacturers that have stayed with unit injectors, like Cat, use a "7th injector" post-turbo to produce the heat needed for DPF regeneration.
So you say prechamber atomization is better altough common rail has higher injection pressure (3-4 times higher than our OM61Xs got) and can superheat through pre-injections? ("superheat" implies to me that that is hotter than "some kind of undefined prechamber fire")
Gruß
Volker
RE: Prechamber Mod "Flame" Front - OM616 - 02-05-2011
(02-05-2011, 03:07 PM)jeemu I know that i need those modified chambers. Those not there just for fun.
And yes its been dynod. Actually my engine is dyno every time when done changes. Thats why i have differend nozzle open pressure, pump timing, etc than others.
I have no need to prove anything to anybody. Do this just my self.
Well said.