Understanding Marine Injectors

[bison]

It is my understanding that in addition to what's been said already, the orifice size and pintle are slightly larger.

The purpose of this would be to reduce peak injection line pressures from additional fuel delivery of the marine pumps. Lower peak injection line pressures (already in the neighborhood of 11,000psi) will help reduce wear and fatigue on the pump drive systems turning the marine pump which, in the majority of 6.5 diesels, is the (cam) timing chain.

Furthermore, the larger orifice and pintle would provide for less mechanical capacitance in the injection line itself. The mechanical capacitance (think of a rubber hose swelling under pressure) would also ultimately limit the amount of fuel (delivery) reaching the injector or cylinder. The pump would not be "working so hard" to pump fuel through the nozzle. Some minute additional delivery in-cylinder would result.

Well... what about the cracking pressure being higher? The answer there is that it is just a "cracking" pressure, the pressure at which the nozzle will open. Remember the injection line pressure I mentioned earlier? This was much higher than the cracking pressure of the nozzle. Yes, the higher cracking pressure will result in better atomization because the nozzle is starting its injection cycle at a higher pressure, but because of the larger pintle and orifice the injection cycle is slightly shorter.

It is because of the slightly shorter injection cycle and minutely increased delivery that I believe that vendors can claim higher horsepower. Is 40HP increase in power accurate? IMHO maybe, but only if you are replacing worn out nozzles to start with...

Regards,

explain to me how you get to 11000 psi peak pressure if pop or opening pressure is lets say only 2200 psi ?? IMO that is all you gonna get.

 

[Edzzed]

explain to me how you get to 11000 psi peak pressure if pop or opening pressure is lets say only 2200 psi ?? IMO that is all you gonna get.

that is akin to saying dynamite only gives a peak pressure of x. well stick dynamite in a can and the peak pressure is gonna really want to peak out to see what is on the other side. remember diesel ignites by compression and when it sets off it is a lot more explosive in a can than outside the can in which case it only burns without an explosion. ED

 

[bison]

that is akin to saying dynamite only gives a peak pressure of x. well stick dynamite in a can and the peak pressure is gonna really want to peak out to see what is on the other side. remember diesel ignites by compression and when it sets off it is a lot more explosive in a can than outside the can in which case it only burns without an explosion. ED

I am referring to injection line pressure, Not what happens afterwards in the combustion chamber.combustion press won't travel back up trough the injector.

injector spring and needle seat works like relief valve,once it opens the press is released ,nozzle orifice and pintle only decide spray patern.

 

[Tin Man]

A number of people (incl. Bill and Todd at HeathDiesel) have told me that HO injectors are a good performance addition.

- better pattern and atomization... especially at higher RPM. If the orfice is unchanged and the big difference is the pop release pressure, a given volume of fuel can be squirted in a shorter burst.

- with HO injectors and stock programming, that is about the best benefit you should see; Todd told me that with HO injectors alone, you would notice very little difference in HP, but mileage and drivability may improve.

- add higher fuel rates, and you can get the same volume of fuel expended in a much shorter duration. Again, at higher RPM, you should notice the biggest difference, as the fuel volume is up, and yet the injection event remains crisp.

That's my take on it, anyway; I don't know enough about the mechanics of the event to build a better explanation, but a friend of mine put in a chip first, then HO injectors, and noticed a pretty big gain each time (first with the chip, then with the injectors). Unless it's the Hawthorne Effect; you pay more attention to something and it seems to improve.

Who knows?

When I went to buy my new injectors, Bill asked if I was still pulling my big heavy trailer in the Rockies... I said yes, and he changed his mind and recommended that I get the normal Bosch injectors. He said that with my tune and with that weight, I would risk overheating and high EGTs with Marine injectors.

I figure if Bill intentionally made less money off me, there must be something to the story.

When I went to buy my new injectors, Bill asked if I was still pulling my big heavy trailer in the Rockies... I said yes, and he changed his mind and recommended that I get the normal Bosch injectors. He said that with my tune and with that weight, I would risk overheating and high EGTs with Marine injectors.

I figure if Bill intentionally made less money off me, there must be something to the story.
__________________
X2 Bill recommended the exact same set up for me.I was only pulling 5500lbs but with the heath 2.0 a upgrade to ho injectors i would have to pay more attention to my gauges,with a slight improvement to perfomance.I decided to replace the injectors with stock. Refer to my signature.

 

[davo727]

Isnt an injection pump a positive displacement pump? Where its going to put out a set amount of fuel into each fuel line per firing event based on rpm and throttle position and calibration? Plunger stroke makes a set amount of fuel output?

The fuel is a liquid and non compressible, yeah the pressure in the line may be 2000 psi due to the restriction of the fuel nozzzle but that doesnt mean that the fuel got compressed because there is a law of physics that says that it didnt. Air can be compressed but a liquid cant, you can put it under pressure by restricting its flow but it still takes up the same volume.
Im thinking the pump is gonna put out the same amount of fuel whether the fuel line goes into a bucket or to a standard fuel nozzle or a marine nozzle.

Turn up manual pump to get more fuel or new computer calibration for more fuel on electronic pump. Am I wrong here or missing something?

 

[Slim Shady]

Isnt an injection pump a positive displacement pump? Where its going to put out a set amount of fuel into each fuel line per firing event based on rpm and throttle position and calibration? Plunger stroke makes a set amount of fuel output?

The fuel is a liquid and non compressible, yeah the pressure in the line may be 2000 psi due to the restriction of the fuel nozzzle but that doesnt mean that the fuel got compressed because there is a law of physics that says that it didnt. Air can be compressed but a liquid cant, you can put it under pressure by restricting its flow but it still takes up the same volume.
Im thinking the pump is gonna put out the same amount of fuel whether the fuel line goes into a bucket or to a standard fuel nozzle or a marine nozzle.

Turn up manual pump to get more fuel or new computer calibration for more fuel on electronic pump. Am I wrong here or missing something?

The pump displaces a fixed amount based on the electronics. The spill valve closes based on the PCM algorithm for that particular rpm load and intake air temp. Once fuel volume is set displacement takes place as the rollers go up the ramp. The fuel is not compressed but pressure builds as it tries to overcome the spring pressure in the pintle valve. When the initial pressure is overcome the fuel is displaced until the spring pressure is greater than the line pressure and the pintle closes.

Higher spring pressure, larger orifice equals shorter open time for a fixed pump displacement. The only way to get a larger amount of fuel out is to up the pumps displacement, which can never be greater than the pistons displacement (bore times stroke). Hence the marine DB2 four piston pump verses the DB2 two piston pump. Both have the same amount of time to pump fuel through the orifice but the DB 2 four piston can displace more fuel than the DB2 can in the same amount of time.

Now our DB2 2 piston pump with a smaller injector orifice and lower spring pressure has a relative spray pattern the same length as the Marine pump and DB2 4 piston pump . However the marine pump will put otu more fuel during the same injector time.

When you put marine injectors on a DB 2 2 piston pump you still get the same amount of fuel because the pump can only displace a fixed maximum fuel based on bore time stroke. The fuel injection event happens slightly later in time because of the higher spring pressure but is of a shorter duration because of the larger pintle valve,

Recap based on fixed maximum fuel volume
Marine Injectors
Larger pintle and higher spring pressure, slightly later injection event but of a shorter duration because the fuel is displaced in a shorter time.

Regular injectors
Smaller pintle lower spring pressure, earlier injection event (lower spring pressure) smaller orifice longer injection event because smaller orifice . Based on fixed maximum fuel displacement

Now different combinations would be interesting. And we are talking milliseconds of difference in timing.

This is my understanding of it, I could be full of it though.

 

[Goldsburg]

explain to me how you get to 11000 psi peak pressure if pop or opening pressure is lets say only 2200 psi ?? IMO that is all you gonna get.

You have to read a lot of diesel injection practice books to fully understand, but if you want the expurgated version, you can read HERE and HERE.

If I put 10 gallons per minute (delivery rate at idle) through a garden hose, that's not much of a challenge right? What if I now need to move those same 10 gallons in 1/5th the time through that same garden hose (aka max RPM)? What will happen to the pressure to move 10 gallons through that same garden hose in 12 seconds?

Regards,

 

[Goldsburg]

The pump displaces a fixed amount based on the electronics. The spill valve closes based on the PCM algorithm for that particular rpm load and intake air temp. Once fuel volume is set displacement takes place as the rollers go up the ramp. The fuel is not compressed but pressure builds as it tries to overcome the spring pressure in the pintle valve. When the initial pressure is overcome the fuel is displaced until the spring pressure is greater than the line pressure and the pintle closes.

Higher spring pressure, larger orifice equals shorter open time for a fixed pump displacement. The only way to get a larger amount of fuel out is to up the pumps displacement, which can never be greater than the pistons displacement (bore times stroke). Hence the marine DB2 four piston pump verses the DB2 two piston pump. Both have the same amount of time to pump fuel through the orifice but the DB 2 four piston can displace more fuel than the DB2 can in the same amount of time.

Now our DB2 2 piston pump with a smaller injector orifice and lower spring pressure has a relative spray pattern the same length as the Marine pump and DB2 4 piston pump . However the marine pump will put otu more fuel during the same injector time.

When you put marine injectors on a DB 2 2 piston pump you still get the same amount of fuel because the pump can only displace a fixed maximum fuel based on bore time stroke. The fuel injection event happens slightly later in time because of the higher spring pressure but is of a shorter duration because of the larger pintle valve,

Recap based on fixed maximum fuel volume
Marine Injectors
Larger pintle and higher spring pressure, slightly later injection event but of a shorter duration because the fuel is displaced in a shorter time.

Regular injectors
Smaller pintle lower spring pressure, earlier injection event (lower spring pressure) smaller orifice longer injection event because smaller orifice . Based on fixed maximum fuel displacement

Now different combinations would be interesting. And we are talking milliseconds of difference in timing.

This is my understanding of it, I could be full of it though.

What he said. Of course taking mechanical capacitance of the injection line into account (remember those milliseconds?)...

Regards,

 

[Goldsburg]

Isnt an injection pump a positive displacement pump? Where its going to put out a set amount of fuel into each fuel line per firing event based on rpm and throttle position and calibration? Plunger stroke makes a set amount of fuel output?

The fuel is a liquid and non compressible, yeah the pressure in the line may be 2000 psi due to the restriction of the fuel nozzzle but that doesnt mean that the fuel got compressed because there is a law of physics that says that it didnt. Air can be compressed but a liquid cant, you can put it under pressure by restricting its flow but it still takes up the same volume.
Im thinking the pump is gonna put out the same amount of fuel whether the fuel line goes into a bucket or to a standard fuel nozzle or a marine nozzle.

Turn up manual pump to get more fuel or new computer calibration for more fuel on electronic pump. Am I wrong here or missing something?

There is also a leakage rate associated with the barrel and plunger assembly that would reduce your actual delivery rate, especially at lower engine speeds.

Regards,

 

[Edzzed]

If I put 10 gallons per minute (delivery rate at idle) through a garden hose, that's not much of a challenge right? What if I now need to move those same 10 gallons in 1/5th the time through that same garden hose (aka max RPM)? What will happen to the pressure to move 10 gallons through that same garden hose in 12 seconds?

Regards,

unless you have a very strong hose it'll burst):h. Ed

 

[JiFaire]

I knew a girl that could suck a golf ball through a garden hose...





oh, sorry, wrong forum.

 

[Slim Shady]

I knew a girl that could suck a golf ball through a garden hose...





oh, sorry, wrong forum.

Dang, now I can't even see straight :mad2:, Laughing to hard to even make more of a reply than this. :thumbsup:

 

[Goldsburg]

I knew a girl that could suck a golf ball through a garden hose...





oh, sorry, wrong forum.

No, no!!! Please continue.... (but hurry to the good parts)opcorn::mikelsheep:

Regards,

 

[bison]

I knew a girl that could suck a golf ball through a garden hose...





oh, sorry, wrong forum.

I would like to meet that girl):h

 

[Deere Freek]

leave it to a mod to take it ot

 

[bison]

You have to read a lot of diesel injection practice books to fully understand, but if you want the expurgated version, you can read HERE and HERE.

If I put 10 gallons per minute (delivery rate at idle) through a garden hose, that's not much of a challenge right? What if I now need to move those same 10 gallons in 1/5th the time through that same garden hose (aka max RPM)? What will happen to the pressure to move 10 gallons through that same garden hose in 12 seconds?

Regards,

OK Goldburg. i read both articles,none of them said that peak injection pressure of the 6.5 is 11600 psi.It said the pumps are capable of producing that kind of pressure. Sooo it means to me that one could set injector pop press to 10.000 psi or more without wrecking the pump.

that brings me back to the 6.5 injection system that uses about1900/ 2200 psi pop pressure.

AS the pressure tester mimicks the inj pump and the adaptor line from the tester to the injector doubles as engine injector line,and the injector is the press relief valve.Than as far as I am concerned there is NO way possible that line press can become any higher than injector opening pressure.[No matter how quik I hammer the tester lever, pop pressure stays the same, And I am pretty sure the tester moves more fuel trough the injector per stroke than the IP will ever do at full trottle].
Unless ofcourse if an injector gets stuck in closed position. That will create the famous knock,[like a conrod with a bad brg].And that situation could create peak press listed. If the IP where to peak out at 5000 psi, then a stuck injector would crater the IP as well in a heart beat,If the inj line would not have burst sooner.

Am i correct,or am i missing something here.

 

[Goldsburg]

OK Goldburg. i read both articles,none of them said that peak injection pressure of the 6.5 is 11600 psi.It said the pumps are capable of producing that kind of pressure. Sooo it means to me that one could set injector pop press to 10.000 psi or more without wrecking the pump.

that brings me back to the 6.5 injection system that uses about1900/ 2200 psi pop pressure.

AS the pressure tester mimicks the inj pump and the adaptor line from the tester to the injector doubles as engine injector line,and the injector is the press relief valve.Than as far as I am concerned there is NO way possible that line press can become any higher than injector opening pressure.[No matter how quik I hammer the tester lever, pop pressure stays the same, And I am pretty sure the tester moves more fuel trough the injector per stroke than the IP will ever do at full trottle].
Unless ofcourse if an injector gets stuck in closed position. That will create the famous knock,[like a conrod with a bad brg].And that situation could create peak press listed. If the IP where to peak out at 5000 psi, then a stuck injector would crater the IP as well in a heart beat,If the inj line would not have burst sooner.

Am i correct,or am i missing something here.

I don't have the text books in front of me to quote exactly why the line pressure exceeds the cracking pressure of the nozzle. It has been about 10 years since I read those books!

It has to do with injecting a quantity of fuel through a fixed orifice (nozzle) in a shorter and shorter duration (higher and higher RPM). If you would like further proof that the injection line pressure can exceed the cracking pressure, I submit Exhibit B (courtesy of Taylor Diesel Group).

Click the link and refer to question 4 (answers are below)...

Regards,

 

[bison]

I don't have the text books in front of me to quote exactly why the line pressure exceeds the cracking pressure of the nozzle. It has been about 10 years since I read those books!

It has to do with injecting a quantity of fuel through a fixed orifice (nozzle) in a shorter and shorter duration (higher and higher RPM). If you would like further proof that the injection line pressure can exceed the cracking pressure, I submit Exhibit B (courtesy of Taylor Diesel Group).

Click the link and refer to question 4 (answers are below)...

Regards,

I start to see your point.friction in fuel movement trough the line must be causing some rise in line press .
But why would that not really evident on the tester gauge,as the tester is worked to its fullest stroke and the pressure gauge is situated at test pump, unless we take jifairs joke with sucking or blowing a golfball [being the fuel]trough the garden hose , expanding the hose where te ball is at any given point.If a guy can use that reference to simplefy a explanation.

Bison

 

[Matt Bachand]

bump

 

[buddy]

A pump outputs more pressure than the actual line pressure, to compensate for the drop in pressure. And even though an orifice opens at 2200psi doesnt mean the pressure behind it cant be greater. Imagine you poked a hole in your compressors hose and it didnt start leaking until you hit 80psi on the regulator, but then you can still turn up the pressure to 150 and it will maintain it because the supply is greater than than the drop in pressure across the orifice.