Black Smoke.....power or waste?

Lenny, i dare say your not married....

 

As Black _Dog said you can't be married. I often wonder if you use the board to relieve anger from a bad day. You did good in the turbo conversation, but had to retaliate in this one........did ya have a bad day? I'd say your a very smart and would be interesting to talk to in person about Hp, unless your panties were in a bunch that day

 

Originally Posted by V8Lenny
Yes, but temperature needed to ignite diesel fuel is made by compression ratio and boost. You don't want the piston to dwell at TDC because it can not do any work in that position, it's just trying to blow your heads off and crack the piston and bend the conrods and crank.

Yes, dwell time can do this too. You didn't and still don't understand why I'm saying the stroke helps increase fuel efficiency and the burning of the fuel. You talking theoretically while I'm talking about everything in the engine being equal........stroke matters then. I loved to play with Chevy Big Blocks over thirty years ago. The bore is the same between a 427 CI and a 454 CI BB, but the stroke is longer in the 454 to achieve the larger CI displacement. With everything being the same in two engines except the stroke. The longer stroke engine would build more Hp at 2* less total ignition timing at 3000 RPM........can you explain why? Why would I have to ###### timing for more Hp in the longer stroke engine, when the shorter stroke engine needed more total timing to burn the fuel efficiently

I'm talking about the same displacement engines with different stroke/bore ratio, you can't compare two different displacement engines because so many things changes. But I can quess what causes 2* difference in Chevy timing: larger cylinder bore don't allow so much advance without knock because it takes more time for the flame front to travel from spark plug to the furthest end of the cylinder. This has nothing to do with diesels, it's one of the very few differences between gasoline and diesel. There's many pages written about the subject by some Cadillac engineer somewhere in the internet.

But about the diesels: one of the reasons why we get same power from Cummins L-10 and N-14 is that L-10 has smaller conrod to stroke ratio and that takes piston quicker out of the TDC and moves it to position where it can make power. In gasoline engines that point is about 15* ATDC, I havent found data about the diesels, I quess it's a little different because burn rate is different.





Yes, they were.

Whatever you say



Because longer stroke gives less dwell time.

longer stroke has a faster piston speed up and down the bore, along with a faster acceleration rate away from TDC and BDC, but has a longer dwell time at TDC and BDC..........I hope you understand what I'm getting at now



US engines have higher injection pressures because your emissions regulations are tighter, higher injection pressures reduce smoke output.

I'm working with a 15 year old injector design.......do you think the pressures are higher? The working pressure of an injector in a 3406E/C-15/C-16/C-18 is the injector opens at 5000 psi and closes at 3500 psi. What is the working pressure of your injectors over there.......higher?

About the same and it's just opening pressure of the needle. Injection pressure is a lot higher, something like 2000 bar (29 000 PSI). Needle opening pressure is there only to prevent cylinder pressure and exhaust gases to get backwards into the injector. Scania/Cummins type injectors are open type, they don't have any needle and that's why their fuel in the tank is always black.




Correct, almost. You don't need the pressure for the needle but to atomize the fuel well enough to mix it properly with air. If your injector body is large enough I can let some company fabricate you bigger plungers. It wont be cheap though. Cheaper option for you would be to let some cam grinder to grind you a special injector cam that has more agressive profile, that will also raise the injection pressure

I see you don't understand how a CAT Electronic Unit Injector works. The camshaft profile at the injector lobe will increase Hp to a point. The problem is it will also increase the internal pressures in the injector to the point of modulating the actuator assembly to blow off the excessive pressure at the tip. This is to keep from blowing the tip off the injector into the engine. You can't burn the tip for energy, let alone fuel control for atomization. Most of the time a tip breaks........you're rebuilding the engine. You need a bigger plunger to increase pressure while at the same time increasing the tip orifice size for more fuel flow. (The best remedy would be to have some one make tips with more orifices instead of larger ones for better atomization and higher fuel flow.) You can't raise the pressures higher without a tip failure or the actuator assembly bypassing fuel back to the fuel rail while the injector is firing. Again you don't understand how a CAT injector works when saying that pressure doesn't have anything to do with the needle and it's function with the injector working properly. The fuel pressure in the injector is what raises the needle from the injector tip seat. The needle has a shoulder at the top of it that acts as a hydraulic piston to lift it up off the seat when fuel pressure rises to 5000 psi. When the pressure rises above this internally in the injector the actuator assembly modulates to control this fuel pressure this allows fuel to escape into the fuel rail even though the injector is still firing fuel into the cylinder. Once the ECM decides to stop injection the actuator assembly is opened fully to allow the pressure to drop below the 3500 psi mark and this closes the injector. As I said earlier these injectors are 99.9% mechanical. So I'm stuck dealing with the 5000 psi pop off pressure and the 3500 psi closing pressure. If you try to modify the needle lift spring(to change pressures) and the amount of needle travel.......this causes other problems

Cat injector works the same as Delphi (Volvo, Detroit) or Bosch (Scania, Mack and others) injectors, in fact it's the old Delphi injector or Lucas back then if I'm right.

Actuator only closes the spill port when ECM wants to start injection and opens when ECM want's to end injection. Opening pressure is like I said earlier but injection pressure is made by cam acceleration, plunger size and tip orifice size. Smaller orifice = higher injection pressure, quicker cam ramp = higher injection pressure, bigger plunger = higher injection pressure.

Latest Scania Commonrail engines have injection pressure of 3000 bar (43500 PSI), I think new Detroits are about the same.




It's hard to find a good tuner here also but they do exist. At least everyone of them can make a smokeless and well behaving engine. Are you still chattering, surging and popping around with your Cat? It's all in the programming, believe it or not.

Just wait, we are coming, they already do some farm tractors and industrial engines. I believe PDI is using european softwares and hardware to read and edit the ECMs, so we kind of are there too.

No, I'm not married, don't even have a girl friend at the moment, no girl wants to live with a guy doing this job, traveling weeks around Europe.

Me and a couple of non-married friends of mine might be coming over there for a cross-America trip next spring, then we maybe can talk about HP if we don't get arrested by US coppers before it.

My ex-girlfriend said I'm always so negative, maybe I'm having a bad day everyday? Or maybe it's just that I don't want to argue about the basic engine working principles that can be read from many books and documents out there. And because I have said that Caterpillar engines are the worst engines made in 21st century, which they are at least over here.

 

I am confident every member here is surprized...

 

Lenny

I'm not in the mood for a technical discussion at the moment.

The actuator assembly also modulates during the injection cycle. The reason for this is all the 3406E/ C-15/C-16 and the C-18 injectors are basically the same except for the orifice size in the tips. If you have a fast ramp rate injector lobe with a small tip the pressure rise will be too fast and high to keep from breaking the tip. Once the pressure rises above the opening setting the actuator spring opens/modulates the spill port to keep this from happening. Once you enlarge the orifices then you have to worry about the pressure at the tip not staying high enough to maintain the needle in the raised position. Think of the shoulder on the needle as a hydraulic cylinder and the high pressure fuel coming from the barrel is the oil needed to move the cylinder or in the case the energy required to compress the spring that holds the needle against the seat.

You can't change the camshaft profile too much without worrying about the plunger bottoming out in the barrel. As orifice size increases you actually get to a point where the needle go out of control and the flow rate of the injector drops. At this point the only option left is a larger diameter barrel and plunger.

You have to stay in the working pressure range of the needle lift spring when you increase the orifice size.

Going to a smaller orifice size will only modulate the actuator assembly more to keep from breaking the tip. This is how CAT can install a large variation of tips on one injector body for many different flow rates.

I want to personally thank Far_Call for this information. I sent him a number of injectors tip with many size variations for him to test on his flow bench. The information I've learned in the last 30-45 days about these injectors and how they work is credited to his time and effort in testing some extreme tips and his explanations of the results

Thank You Sir

 

Not trying to bad mouth BD but this is pretty much exactly what my tune from BD does... Don't like it but love the power.

 

No it's not. The ECM programming in my two competition ECMs has been proven many times in other trucks......it a problem in my truck. I changed two injectors and got rid of 80% of the problem. I still have to find the other injector that is bad. Unfortunately without the proper flow bench to test them on this problem is very hard to find. I do believe it's injector number 5 with everything I've done to isolate it. The problem I believe is the shoulder of the needle that acts as a hydraulic piston to raise the needle is worn or the injector body area it rises into is worn. This allows fuel pressure to bleed away from the tip making the needle chatter during the firing cycle

 

I think you didn't understand the difference between needle opening pressure, so called pop-off pressure, and injection pressure? It's also hard for me to believe that modulation thing, that ECM is not fast enough and they have no way to measure and control the pressure. You can easily make 5000 PSI needed to open the needle even with very large orifices, in fact when thinking again, orifice size has nothing to do with opening pressure because needle is before orifices. The problem with large orifices is low injection pressure that is not atomizing the fuel and penetrating through air well enough.

This is from Diesel Engine Reference Handbook:

And finally, the nozzle must be able to
seal off the fuel-injection system against the hot, highly
compressed gases from the combustion chamber (up to approx.
100O​

​

​

​

0C). In order to avoid blow-back of these gases when the
injection nozzle opens, the pressure in the nozzle's pressure
chamber must always be higher than the combustion pressures.
This requirement is particularly difficult to comply with at the
end of the injection process when injection pressure has already
dropped while combustion pressure is increasing rapidly

I thought Cat (like all other manufacturers) was using different injector cams for different applications to keep injection pressures optimal?
​

I could also explain why badly tuned ECMs are chattering and jerking at part load conditions but maybe later.

 

No woman no cry.

 

better than pay somebodys Child Support-alimentation

but did you consider to get truck for shorter trips like timber/tipper/crane and be at home every night