HP differences out of same engine???

[RobJ]

TRIPLE WRONG -> So why is the fuel overflow from each injector being fed back to the fuel tank with warm fuel then?

Simple, because more fuel is being supplied by the pump to each injector than what a single injection event is capable of injecting.

That is why simply adding larger orifice injector nozzles allows a larger cubic volume of fuel to be injected each time resulting in more torque and horsepower.

Honestly and kindly do a little research and you'll understand.

The fuel overflow is to catch internal leaks in the injector, things wear and there is a need to catch the fuel. There is also a spill port to allow pressure to be bleed off. Actually if you look at your system you'll see the the return line begins at the injection pump. There is also a check valve there to keep the fuel from coming back through the return line (and air). In a gravity feed system like on my L I don't think any fuel gets past that. If you have a feed pump you will get a constant flow through the return as the feed pump provides more volume than needed. All my diesels I worked on did this.

Why is it warm? I really have to say? The engine gets hot, the injection pump is connected to the engine, heat is transfered to the injection pump which transfers the heat to the fuel inside the pump. Same with the injectors, they do get pretty hot.

Seriously though Skypup, don't take my word for it, don't take the words of a Kubota shop manual, seek out someone who knows. They'll set you straight and you don't even have to come back here and say so.

What else you got?

Here is a simple one, what we have is an Inline Injection pump...note paragraph 3.
Injection pump - Wikipedia, the free encyclopedia

 

[SkyPup]

I've got the NipponDenso technical manual for the Bosch knockoff that Kubota utilizes!

 

[RobJ]

I've got the NipponDenso technical manual for the Bosch knockoff that Kubota utilizes!

And so??? Show me.

The knock offs use the same technology. That's why they are called knockoffs. And BTW, I have a knock off of that one, it's called the Kubota WSM. See above post.

 

[hz293]

So are you saying that to increase my B7510 Kubota 21hp by 10 to 15% all I have to do is put in a bigger nozzle?

Harris

 

[RobJ]

So are you saying that to increase my B7510 Kubota 21hp by 10 to 15% all I have to do is put in a bigger nozzle?

Harris

Hmmm, haven't seen skypup lately to answer? You know maybe instead of buying new nozzles you can just drill some bigger holes in the ones you have.

 

[CurlyDave]

...However some of the engines have the same displacement, bore, stroke etc and have hp differences of 10. For example the M6040 and M7040. How are they doing this? What are they doing? Just curious. Thanks,

Bryan

I got fairly involved in this maybe 25 years ago, and I suspect the answer today is the same as it was then. Bigger injectors and more fuel will increase the HP of a diesel engine significantly. Add a turbocharger and you can get even more HP.

The price you pay is engine life. An extreme example back then was the Cummins 855 cu in diesel. Owners of truck fleets would buy it set up for about 200 HP. Their drivers would think it was grossly underpowered, but it gave good fuel economy and it lasted about a million miles.

Owner-operators would buy it set up for about 400 HP and it would give a lot more acceleration and still last a reasonable amount of time.

The military would buy the very same basic engine and set it up for max horsepower, which was about 1200. A fairly compact power plant for an APC or something like that. OTOH the life was on the order of 5000 miles.

 

[SkyPup]

So are you saying that to increase my B7510 Kubota 21hp by 10 to 15% all I have to do is put in a bigger nozzle?

Harris

Yup, that's all you have to do!

The simplest way to increase the torque and horsepower of a Kubtoa diesel engine with a NipponDenso inline mechanical pump is to provide more fuel within the narrow crank angle of injection. To accomplish that, you either increase the injection pressure at the pump, or simply increase the diameter of the pintle orifice at the injector nozzle, both result in more fuel being delivered into the combustion chamber within the critical crank angle window of injection.

 

[Musclford]

Makes sense but I just hate the idea 1) of paying more for the extra hp when the engine itself cost no more than the de-rated one or 2) paying less for the de-rated engine but knowing that your engine makes less power than a virtually identical one.

I guess the next question is how hard is it to up rate a de-rated diesel?

fifteen years ago, the main difference between a 350 hp CAT, and a 400 Hp CAT on highway truck engine was fuel pressure? But the added cost of the 400 Hp engine was to cover warranty issues?

A friend worked in their R&D dept and said that your obviously more likely to break something with more power... Daaaa :O

Also, another friend was a CAT diesel mechanic... I couldn't tell you how many 350 Hp engines were bumped up to 400 + once they were in production.....

Granted, this was 15+ years ago, but I'm sure that still holds true today in most cases....

 

[RobJ]

To accomplish that, you either increase the injection pressure at the pump, or simply increase the diameter of the pintle orifice at the injector nozzle, both result in more fuel being delivered into the combustion chamber within the critical crank angle window of injection.

The plunger and barrel of an inline injection pump is capable of producing 10,000psi. The injector pops at about 2000 psi. Of course you need it to pop at a certain pressure to ensure proper timing. The only way to change the pressure is adding shims to the spring in the injector. But if you increase pressure, it'll take longer for that pressure to build and it'll delay the timing. So you must advance the timing, of course since the injection pump is metering fuel, you still get the same shot. If you want more fuel, you turn up the injection pump.

So Skypup, if the fuel is regulated by the injector. how does the engine change speeds (idle to WOT). And pressure is an incorrect answer. The plunger and barrel of the pump is a positive displacement pump.

Some more required reading below. It's ok to learn new stuff. Click next at the top of the page for more reading.

Figure 5-10.—Sleeve metering barrel and plunger assembly.

 

[Muleskinner]

It's like the 5.9 Cummins ISB in my 01 Dodge truck. The exact same engine in a school bus puts out over 300 HP from the factory. Mine makes 225 HP. Go figure.

 

[ozzie tractor]

skypup, im sorry but you are wrong, it is the injector pump which contols the fuel andd thus HP. the injector is only a thing which sprays the fuel at a set pressure, return to tank is internal by pass of injector,
inside the pump is a pistom in a bore, the bore has a hole in the side, fuel enters as piston is down, as piston travels up it blocks the hole and pressurises the fuel, starting injection. in the side of the piston is a slot at an angle which is linked to the top of the piston, so this slot is pressuresed with fuel as the piston goes up, once the piston travels up far enough, this slot opens up the inlet hole and pressuised fuel exits back through the inlet hole, dropping the pressure and stopping injection. because the slot is at an angle, if you move the position of the hole around in regards to the slot in the piston, the piston travels futher up before injection stops, which gives more fuel. i hope i didnt confuse matters futher with that description.

 

[ozzie tractor]

back to the question at hand. the manufactures do it to save money, they make a motor thats reliable at max hp, then de rate it till it becomes inefficient. its easy to derate an motor, there is a max fuel screw, and no im not saying where it is, because its illegal to touch for emmisions regs. (this is all mechanical injection only here people). once you add more fuel than a engine can burn you get lots of black smoke. the fix to this is as CurlyDave mentioned, a turbo. much more air in there now, so we add mcuh more fuel again. remember with a diesel, fuel equals HP or smoke, plus heat.
Example Kubota M95X Vs M105X (hope you get these models over there). 95 has turbo, no intercooler. 105 has turbo and intercooler, its my guess the 105 is running more boost (which creates more heat in the inlet) and needs the intercooler to keep inlet temps under control. more boost means they can add more fuel to make more power.

 

[SkyPup]

Larger hole in the injector flows more fuel during the injection crank angle window of the pump, simply works great for me.....

 

[machmeter62]

I added hp to my 92 Ford 250 7.3 liter diesel engine via a BANKS TURBO CHARGER, and the hp increased from 180 to 265 hp, but the cost was a couple of thousand dollars. I needed the power because of operating at higher altitudes by towing a large boat over the Sierra Nevada Mountains. I got an additional 10 inches more manifold pressure with the TC, to maintain seal level conditions. They also installed a pyrometer, along with the boost gauge, but mentioned the pyrometer was the limiting factor!! Don't exceed 1100 degrees F., where "piston melt" will start to occur!! There are times on those grades where down shifting was required, because of cylinder temperatue, and not lack of torque or horspower! The positive side of the TURBO, I was able to maintain freeway speeds most of the time. Under certain conditions, with larger fuel injectors, will heat be a damaging factor, by "piston melt", with a 15% hp increase to smaller cu. in. tractor engines under stressful conditions?

 

[RobJ]

Larger hole in the injector flows more fuel during the injection crank angle window of the pump, simply works great for me.....

Now I understand, you are talking about a gocart.

 

[ozzie tractor]

Larger hole in the injector flows more fuel during the injection crank angle window of the pump, simply works great for me.....

if you fit larger injector nozzles, the pump may well flow more fuel due to less restriction, BUT at the expense of injection pressure. this will affect atomisation of the fuel. drastically reducing the efficiency of the engine. bigger fuel drops in the chamber means less area of fuel expesed to the hot air. which means slower burning and dare i say it more diesel knock. this is not how you up rate a diesel engine, to do that you increase the injector pump flow (as i covered earlier or with a new pump with larger pistons in extreme situations) and then you match the injectors so they can move the required amount of fuel in the available time. most injectors can handle a bit more fuel without making the injection event become to long and run outside of the injection window which you speak of. fuel injected outside this window is wasted and ends up going straight out the exhaust and it is still burning as it goes. i have seen a MF 3505 which had the fuel pump output turned up shoot a 10" flame out the exhaust at WOT as it neared full RPM. it went ok, but very bad on fuel.

 

[ozzie tractor]

Larger hole in the injector flows more fuel during the injection crank angle window of the pump, simply works great for me.....

now have you actually dont this? would love to hear of examples. i know the way i have been taught to do things and im not silly enough to close my mind to all other possible methods of achieving the same result. but i know that the way in which i have outlined works. just fitting a bigger nozzle is like pulling the end of you garden hose. instead of a high pressure spray, you get a low pressure flow, it may well flow more water due to no restriction, but only to a point. then what ever is pushing the water becomes the restriction. diesel injection must be at extreme pressure for atomisation (yes we are talking from about 10 000psi all the way up to nearly 20 000psi in some systems) the better the atomisation the more efficient the motor uses the fuel.

 

[Egon]

I'm kinda confused with all the statements made on this thread. I'll also admit I am not very knowledgeable about the mechanics of diesel injection pumps or injectors.

I went out and looked at my Kubota B7100 HST. Its probably as simple as an injection system can get.

Gravity feed to injection pump
a steel line to the top of each injector
another steel line from the midpoint of the injector that conects all three injectors and teminates in a low pressure line to the top of the fuel tank

My 1996 12 valve dodge cummins diesel has:

Low pressure line to fuel heater and lift pump
steel line to injector pump
steel line to each injector
steel line from injector pump terminating in low pressure line to fuel tank

From internet reading I understand one can increase the horse power of this engine by some very simple means.

Open up the injector pump plate
install larger injectors
and then there are a host of other things that can be done.

Now I surely do not know how this all works but I'm sure one of you fellows out there does!

 

[SkyPup]

Now I understand, you are talking about a gocart.

Nope, just the two diesels I already modified with custom larger injectors. Like I said, it works great if you don't mind a little lower fuel mileage and a little more smoke, espcially under load.

 

[ozzie tractor]

Nope, just the two diesels I already modified with custom larger injectors. Like I said, it works great if you don't mind a little lower fuel mileage and a little more smoke, espcially under load.

that'd would be the side effect of the lower fuel injection pressure now wouldn't it.this certainly isnt how a manufacturer would up rate an engine, because as you noted you get more smoke. you cannot have that with an OEM aplication, so they turn up the fuel pumps, as a result of this they may bump up the injector nozzle size, hence keep the pressures up as well as getting the extra fuel in within the required time.
now i am not going to start on the subject of pollution and what the authority's think of all this