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.