12 Valve injector help
 

I know that it has been popular to install the marine spec injectors in Dodge diesel trucks. I have 12 valve Cummins engines in my boat. They are the 330HP version. I want to uprate the engines to 370HP spec. My injectors are Bosch 0432131753 (Cummins 3897596). Some companies are advertising this part as a 370 HP injector. The Bosch injector 0432131715 (Cummins 3865968) is rated as a 370HP injector. I have removed a 753 injector and it is a 5/12, 260 Bar injector. I am trying to understand what is different between these injectors. I have been told many things such as there is no difference, the 715 has 4 larger holes, the 715 has a higher pop pressure, Etc. My Cummins parts book lists both injectors and a parts breakdown. Besides the information I have heard, the parts book shows all the same part numbers for both injectors. Same nozzles, same pintle, and all the other parts that make up an injector.

Can anyone help me learn the specs on the 715 injector? I want to learn the hole size and number, as well as the pop pressure.

Thanks
Jack

Jack:

I am not familiar with all of the "Cummins" Marine Injectors. However, I have run the 370 Cummins Injectors in my 1996 Dodge CTD 12 valve. I can tell you without a doubt that those injectors have FIVE (5) holes in the nozzle and if I recall the holes are .013. A bone stock 1996 Dodge CTD with the 180 Pump had FIVE (5) hole. .09 nozzles. Hope that helps you some.

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John_P

Well it's a long time and many beers ago... If I recall this correctly the marine version of the B series had different pistons and (more pertinent to your question) a different geometry of the injectors.
The spray angle and the desired spray distance was different to the automotive (Dodge Ram) design.
I can not help you with the search for better injectors, but I can advise you to this difference. (And to search for the horror stories of mixing these two designs)

Thanks for the quick responses. If the 715 injector has a 5/13 nozzle that could explain the increase in power output. In addition to the injectors, the only other differences I can determine is the additional 200 RPM top speed and 2 degrees more advance. Perhaps that is enough to get 40 more HP on these engines?

Sounds like the marine injector is not the best choice for the truck pistons. Nice to see that the aftermarket offers so many choices for the truck engine. I want to make a little more power, but not at the expense of fuel burn and more smoke. My boat has above the water exhaust so billowing black smoke is not an option.

Has anyone increased the pop pressure on their injectors? I know it can retard the timing, but are there any benefits?

Thanks
Jack

About pop pressure- increasing the pressure can lead to a little cleaner idle, due to better atomization of the fuel. But above a certain point there are no more gains, stock pop pressures should give you a clean idle. An increase above the stock pressure will only increase the load on the lines and the pump with no benefit.
If I recall it correctly the difference between 330hp and 370hp marine was only in the pump calibration, mainly different governor springs and the plate. The 2degrees more advance were needed for a clean burn at the higher rpm with the longer injection time.
Timing charts give you the start of the injection event, and the more fuel you inject the longer it takes to get it into the cylinder.

So for your engine I'd suggest to check the injectors for proper spray pattern and pop pressure, and then adjust the injection pump to the specs of the 370hp version.
Depending on your configuration and usage it may be beneficial to change the turbo to a more efficient design, this can keep your EGTS and fuel consumption down a bit.

The 715 marine 370 injectors are not 5x13's...theyt are 100% 5x12's. Sold thousands of them when they were popular way back in the day & have pin measured them at .012"

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Thanks for the info on the 370 nozzle holes Mark! At least I was close.........................LOL!

I really appreciate all the feedback. Getting information about these engines has been very difficult. I have heard that the 753's are 4/12, 5/10, and 5/12 so I purchased a set of pin gauges in order to be certain about my injectors. Does anyone know the pop pressure for the 715 injector?

Since the injectors have never been out I suspect that they could be low on pop pressure after 20 years. My plan is to buy new injectors verify their pop pressure then swap them. If I buy the same (753) injectors then I would clean and pop set originals to swap in when it is time. That's were I am stuck, which injector to buy. If there is something different about the 715's I want to buy them. When I spend money I try to also make improvements. If they are different then I would buy another set of 715's to swap in 5-10 years from now. I'm thinking that pop testing injectors periodically is maintenance.

I cannot find out about the governor springs or the fueling plate. Bosch refers me to Cummins, they refer me to a fuel injection shop. The shops I have contacted say bring them in, we will then give you an estimate. I know the 370 engine has a 200 RPM higher top speed, but everything else remains a mystery. I do have 197 delivery valves. The engine data sheets plot HP and TQ across the RPM range. The 370 engine shows slightly higher numbers at each RPM point.

Both engines come with the Holset HX40 turbo. They have a different mounting flange than the truck turbo and they do not have wastegates. I do not see any aftermarket turbos for the marine engine. I can't find out what the boost pressures should be. I heard that the engine data sheets show max boost at top speed. All I can find is a manifold pressure rating in Inches Mercury. That number converted is 28 PSI for the 330 HP and 30 PSI for the 370. Not sure if am right, but I will check the AFC to that number to start.

Besides keeping the engines running well, I have three issues that I am trying to improve.
1. The engines smoke at idle (more like a haze) more than I would like. I keep it in a marina and want to be respectfully of my dock mates. I have been advised to raise the pop pressure to have a cleaner idle. I was advised to set the timing from 22 degrees to 28 then set the pop pressure to 300 Bar. I plan to reset the timing to at least 24 degrees (370 spec).
2. The bow starts to rise getting on plane at 1800 RPM and its up on plane by 2000 RPM. Once I get to 1800 RPM the boat stops accelerating and the RPMs won't go higher. It I as if the load at that moment is greater than the power output of the engines. 10-15 seconds later the boat slowly gets up on plane and it runs fine. If I advance the throttles to full speed at this point the RPM's and boat speed does not increase. If I do advance the throttles at this point the engines start blowing black smoke until it gets on plane. At this speed the engines have 5-6 PSI of boost. Not sure if that's OK?
3. I like running the boat at 25 MPH. At that speed the engines start to get loud (2400 RPM). If I can safely increase the power output I can re-pitch the props and reduce the noise levels. This one is my wish the first two are important to me.

Looks like I wrote a novel. Sorry about that.

Any help or suggestions are greatly appreciated.
Thanks
Jack

Jack:

Let me see if I can help you out some with your questions.

First of all, let me recommend an excellent shop to you in Terre Haute, Indiana, namely, "Scheid Diesel." They have been in business for well over thirty (30) years and they are a certified Bosch Fuel Injection Shop. Give Joe Hackman a call @ 1-800-669-1593 and I know he will be able to help you out with the selection of the right injectors for your boat engines. He is also VERY knowledgeable on anything concerning diesel turbochargers.

You mentioned the HX-40 Turbochargers. Both my Son and I ran the Holset HX-40 Turbochargers on our 1996, 2001 and 2002 Dodge CTD Pickups. Our Holset HX-40's WERE wastegated and we had the 16cm exhaust housings on them. They performed VERY well for us BUT,...you cannot run them with boost pressures much above 40psi. I still have one left if you are interested in it.
Scheid Diesel should be able to hook you up with the proper "flanges" but if not they also have a full machine shop and can most likely make them for you.

Here is their website Jack:

www.scheiddiesel.com

[QUOTE=JKosinski;3360334
2. The bow starts to rise getting on plane at 1800 RPM and its up on plane by 2000 RPM. Once I get to 1800 RPM the boat stops accelerating and the RPMs won't go higher. It I as if the load at that moment is greater than the power output of the engines. 10-15 seconds later the boat slowly gets up on plane and it runs fine. If I advance the throttles to full speed at this point the RPM's and boat speed does not increase. If I do advance the throttles at this point the engines start blowing black smoke until it gets on plane. At this speed the engines have 5-6 PSI of boost. Not sure if that's OK?Jack[/QUOTE]

Seems like a Holset 40 should give you better than 6 PSI boost. Or do you measure boost above std atm? My 1998 180 HP Cummins P/U with Holset 35 factory setting was 22 PSI on the gauge. I can run like this without a lot of smoke, and rated HP developed at moderate RPMs.

We always say smoke indicates unburned fuel and that is a result of not enough air (boost) or too much fuel (big injectors). Have you inspected for compressed air leaks? How do you cool your compressed air? Without a waste gate, how do you control EGT? Without decent boost you won't develop the expected HP, can't get up on plane. Don't expect bigger injectors to help if you can't burn the fuel.

BTW, my injectors are original, never been out, and idle is smooth with no smoke. 20 years. Why do you think pop pressure is a problem?

OK
1. Sounds like worn injectors, or maybe slipped timing. (Injectors more likely, the holes get worn over time, so simply setting pop does not cut it- get new tips at least)
2. The non-wastegated HX40 is below it's boost threshold @1800 rpm for your engine. So you do not have the air to burn more fuel and create more torque to get moving faster- instead you blow black smoke- also a little bit depending on the injectors, but mainly it's a turbo thing. You could also say that you are over-propped for your turbo.
3. Unless you do something about the turbo and the injection you will have negative results with steeper props. (More lugging and black smoke until you are on the plane. )

I would not go over the stock pop pressure. This is only a band-aid for worn injectors, but no cure for improper spray pattern and drop size.

Another thing to consider is the air supply- start at the air filter, if plugged it will hinder performance, Boost leaks will also affect you, a plugged intercooler is also a possibility.

A search for pictures of the marine turbo it will show how different the mounting flange is. The marine turbo is water cooled. The boost pressure is cooled by an aftercooler that uses lake water. There is a very short circuit from the turbo to the intake manifold. The fittings appear tight. Air filters are new and I serviced the aftercoolers, no issues there. I pin timed the engines. The engine and injector pump pins align so the engines should be at 22 degrees. Because there is not a wastegate the boost curve must be such that it won't over pressurize. I can't find any data that tells me what the boost pressure should be at any RPM points. I have thought about installing an aftermarket turbo wheel, but I am concerned that it could over boost at max RPM.

I have a Maretron network that measures, Boost, Pyro, Fuel Pressure, Fuel burn, and Water Pressure. The exhaust temp never goes over 1,000 degrees. I have read that in the case of the dodge engine adjusting the smoke screw will increase low speed boost pressure and bring on boost sooner? Without knowing what the boost should be I don't know what 6 PSI means. I believe it needs more air because advancing the throttles only creates black smoke.

I have not heard of anyone pop testing used injectors that popped to spec. After 20 years there is a good possibility that they will pop below 260 Bar. I want to swap in new injectors to reduce the down time. I was only considering raising the pop pressure of the new injectors if it would benefit performance. Perhaps new injectors with the correct pop pressure would smoke less?

The prop pitch is determined by Max RPM. Gas powered marine engines list an RPM range such as 4800 to 5200 RPM. If the boat is over propped the engines won't reach 4800. If under propped the engines will rev past 5200. Diesel engines should be propped to run 150 RPM past max RPM. My engines run to 2950 (2800 spec+150) in neutral as verified by a strobe tach at the crankshaft. It does run to that speed on the water as well. Diesel engines have throttle stops limiting max RPM. I plan to reset the stops to 3200 and see if the boat will go there with the props I have. The 370 spec engine has a Max RPM of 3000. If the engines go past 3150, the engines could take more pitch. It has been on my mind that a combination of weight, load, and prop size are overloading the engines at 1800. The prop shops say max RPM is the only determining factor in prop size.

I am hoping that new injectors, more timing, and a few AFC adjustments would be the cure. Without specs it is difficult to determine the problem.

Thanks
Jack

Your AFC does not work correctly, because it should keep the engine from smoking in low boost situations.
On the trucks the AFC sometimes limits fuel too much and causes low EGTs and slooooow spool. But that is not your problem, you can overfuel at will at 1800 rpm.
Pop pressure and spray pattern of a new and correctly calibrated injector should help with your idle problem, at least over here I do pop test new injectors before installing them.. Already had some injectors fail on the bench and saved time and confusion as to why the bugger still smoked/hard started/knocked etc. I strongly suggest that you take the 2 minutes per injector.

About props and timing- the boat with the props installed almost overloads the engines at 1800 rpm, therefore the torque of the engine is insufficient to accelerate the boat.
Increasing timing will result in a torque increase at higher rpm, but more smoke and torque decrease at lower rpm.
Your problem seems to be insufficient torque to get through the transition between full hull drag and the reduced drag while on the plane. This seems to be caused by the setup (turbo, injectors, etc) being made for a boat that does not plane, and that would need an almost linear increase in torque and power to accelerate.

Ideally you would get a VG turbo/shot of nitrous/twins to get the necessary air to get enough boost to make good torque at 1800 rpm with still enough air and optimum injection timing for your cruise. (But that's dreaming... )

Now with a boat that planes I would suggest that you get new injectors, pop test them and test drive. Also get a timing kit and go for about 17-19 degrees, to fatten the torque curve at 1800, and sacrifice some torque while on the plane. (Consider the different pump cam profile when timing the engines, do not simply use the charts from truck applications, and be aware that pin timing is not really accurate)

I have to emphasize that your boost is bust. My truck runs like a bat out of hell at 22 psi boost, 6 psi is a light load. Your 6 psi is a no-wake idle. You are not developing rated HP, and blowing smoke at full throttle, because you don't have enough air to support combustion. Boost is the first and easiest indication of engine power. Can you get a HP/torque/boost graph for your engines?

This is all really good info. It is helping me figure some things out.

6 PSI boost @ 1800RPM seems low, but I am confused that both engines have the same boost numbers? The engine data sheets give HP, TQ, and fuel burn plotted at 200 RPM increments. At 1800 RPM each engine should be producing 227 HP and 661 TQ. At 2000, 260 HP and 683 TQ. The paperwork shows manifold pressure at 56 in. Hg. I think 56 in. Hg converted is 27.5 PSI? If I am right about that it must be max boost. That gives me no idea of the boost at 1800 RPM.

Has anyone documented the boost pressures before and after AFC adjustments? When the dodge trucks are sluggish does anyone know the boost output? Did the AFC adjustments increase the boost? I understand the adjustments increase power, but does that mean the original adjustments were off of the factory specs? Has anyone bench checked their pump before making adjustments to see if the performance was up to factory specs before making changes?

My pumps have not been touched from new. The fasteners are paint sealed. I believe that the pumps are factory set to 22 degrees. In other words when the pump timing pin is aligned then the pimp is 22 degrees? I do understand that there is some play in the engine pin, but I thought it would give me a close number. If the engine and pump pins line up then the engine should be somewhat close to 22 degrees? I know it may be less than spot on, but I could be sure the timing is not 12 degrees? I am understanding this correctly? I have read that adding 4 degrees of timing to the Dodge engines have noticeable power increase. Will reducing the factory timing from 22 to 19 make the engines more sluggish?

I think the "smoke screw" controls fueling before boost. Turning in the screw pushes the AFC foot forward. This gives more fuel before boost? Some have said that this extra fuel before boost gets the boost started sooner and increases the boost pressure? Will 6 PSI move the AFC foot? At 1800 RPM I have assumed that the 6 PSI boost pressure has begun to move the AFC foot so more fuel is available.

I have seen the P7100 pump cutaways. I think the governor arm rides on the AFC foot until boost pressure pushes the foot forward and eventually the governor arm is riding on the fueling plate. At what point does the governor arm make contact with the AFC foot? Does the arm make contact from idle or does it make contact when the throttles are advanced?

Thanks
Jack