Prechamber Mod "Flame" Front

OM616

10mm MW

572

01-26-2011, 11:40 AM #59

(01-26-2011, 12:14 AM)Hercules My two cents worth.In 1981 mbz increased prechamber hole size,in1982 hole size was reduced back to1981 level. Mbz stated,inorder to reduce piston crown temps. Why the increase in hole size? Mbz was looking for more power. (It did work) ... Not just theory. Only concerns of high piston crown temps. Now in 1985 Mbz again increased hole size to 1981 level,larger size. Have I done this,Yes, does it work,Yes. Noted results,Increased performance, quicker spool,pulls grades in high gear much better. Mbz did it. A little twist,not wanting to go larger than mbz did, I taper reamed all the holes. Larger outside hole smaller inside. Was trying to give flame front a little better direction,to spread more evenly. Results,Little or no smoking. Even wife commented after several months of use,that she had not seen any more smoking after those adjustments.
Well maybe that was three cents worth.

I would have paid a hole dollars worth of cents to have you post that information!!

Seriously, thank you for posting. I like the conical port idea as it helps air get in but doesn’t help the gasses going out. Ideally if the ports could be calibrated so that the amount of pumped air can get in and out of the prechamer with in the time available, however the additional expansion gasses will increase the volume of gasses that need to flow to balance the pressures, which will take longer, prolonging the pressure inside the prechamber. Another way to put it is, 10 people can quickly pass through a door, (compressed air), however it will take 50 people a bit longer to get through the same door, (expansion gasses).

I have not posted 99% of the data that I have from the tests that I have done, most with the assistance of others. I can see that could cause a cloud of skepticism to form over my posts, regardless of the other members that have posted about their modification of their prechambers, none which have reported melting anything. I also attached a scan of the manual I refferenced that did not have hole specs.

In an effort towards full disclosure, I feel it would be appropriate for me to provide some examples of previous experiences in the automotive field.

I attained a Master Auto Certification from the State Of Michigan three months before I graduated from high school. I then went to work for an independent repair shop as a derivability technician.

The management promoted further certification by reimbursing the costs of the tests, and giving a $20 one time bonus for every additional certification a technician earned. Needless to say I started collecting ASE certifications, and when I left that shop to go open my own, I had accumulated 37 ASE certs, many in advanced categories.

A side story; I was sure that I had the record, but the last time I went to a testing center, I decided to talk to a guy that I saw every time I was at the local center, and most of the time at out of town locations, (they only are in the area once a year, so I would go out of town to test more often), and to my dismay I learned that he had 42 certs, not including the three tests that he just took.

I had my own shop for several years and during that time I acquired additional training; Mercury Marine Outboard Factory Trained, Mercury Marine Inboard, (including Diesel), Factory Trained, Yamaha Snowmobile, Motorcycle, and PWC Factory Trained, and a FAA Aircraft Power Plant Ticket. I also was granted an Annual Authorization from the State of Michigan as a instructor in Automotive and Welding Technologies.

I then had an opportunity to go to work for an independent engine developer as a machinist / fabricator in the Instrumentation Department, modifying parts for sensors, making special bolts for strain gauges, Fiber optic scope adaptors etc. I did that for about 10 months, and then was transferred over to the engineering side where I remained for about 5 or so years, until I was transferred to head the Forensic Department. After a year or so, I went to work for GM, which took a big hit and thus I am now back on my own again.

I still have contacts and privileges at the Engine Development Center, even asked for a consult from time to time. The facility is incredible, and the security is tighter than a nuclear reactor, (I have a friend that was a reactor operator for U of M when they had the reactor running).

Anyway, the Instrumentation Department is developing a new temperature sensor in house and they were looking for non-program applications to test it out, I mentioned my little research project and they insisted that I bring the engine in to wire up.

Now, no paper leaves that building unless it is shredded, no camera phones, no memory sticks, no CDs, no lap tops, no Ipods, are allowed past security. Industrial espionage is a very serious subject, there are at any given time at least two different F1 engine programs going on, in addition to Big Three, and Air Craft programs. The security protocols insure the clients that their technology stays confidential. All e-mail is incepted and a individual key is assigned to every clients address, and unless the recipient of an e-mail has the right key, no dice. That prevents accidentally sending information to the wrong address.

Needless to say all my data is in note books with in the compound, and that is where they will stay until they are destroyed. It is kind of a bummer, because I have lots of cool and groovy graphs and what not, but I am going to have to go from memory, and be very careful as to what and how I post any information. It sometimes becomes an issue where the mere mentioning of a measurement result implies that someone out there is capable, and is measuring that specific parameter. So no offence intended when I don't seem forth coming.

Additionally, the fact that other members, Jeemu and Hercules, have posted that they have modified their own, and in Jeemu's case others as well, prechambers and their reports of the result range from, in Jeemu's case not that apparent per butt dyno, (not dynoed yet I don't think), to noticeable improvements in smoke and power (per but dyno), and none of us, my self included here, have melted a piston, (through at least), or destroyed an engine.

Dose that mean that modifying a prechamber as no risks, no, does that mean that there is not a modification drawback that is not apparent with out proper measurement, of cores not. In the beginning I posted that I didn't want to get into this subject in depth because I wanted to wait until I had an engine on my dyno, and data as to the affects of specific degrees of modification. I do enjoy a good technical discussion though, and this thread, despite the tension, has been, and I hope will continue to be, a good technical / theoretical discussion where members post questions and thoughts when they normally would refrain themselves because they think they are not knowledgeable enough to offer anything. That is NEVER the case. Even the simplest of questions or thoughts can spur ideas and create tangent thought strings. Even just posting that you like the thread, or your thoughts about how it would be better encourage continued discussion.

Now moving right along. There seem to be two schools of thought regarding where the majority of fuel is burnt, the cylinder or the prechamber. If I may, Thought #1), those advocating that the fuel is burnt in the cylinder, contend that in essence, the prechambre is strictly an extension of the injector nozzle that conditions the fuel into a more burnable form and disperses the conditioned fuel throughout the cylinder where it then ignites and burns like a DI engine. And #2, those, (myself), that advocate that the prechamber is actually the combustion chamber, or more, a constant / fixed volume combustion chamber, where as much fuel is burned as possible in a fixed area that retains and concentrates heat, maintains a pressurized environment longer than the cylinder to promote complete combustion, and incoming air is directed in a swirl to help dilute and scavenge the remaining post-combustion gasses left over from the previous cycle.

Unfortunately, I have to go for now, but I will continue with my thoughts when I get back.

This post was last modified: 01-27-2011, 07:24 PM by OM616.

Attached Files

Image(s)