Performance 6.5 Injectors

[More Power]

There are a multitude of reworked injectors for the Duramax, Powerstroke & Cummins diesels. The hi-flow nozzles are usually the result of extrude-honing to increase fuel-rate (fuel passages are increased in size). The developers can show the flow rates for stock and their performance injectors. The current Duramax, Power Stroke & Cummins all use some form of high pressure common rail fuel injection systems. Common rail systems can push huge volumes of fuel through modified injectors.

The electronic 6.5's Stanadyne DS4 rotary fuel injection pump is limited in the amount of fuel it can deliver because of a finite volume in each of its four pumping plungers. Opening the nozzles beyond a certain point won't deliver more fuel because of this finite limit.

Hi-pop 6.5 injectors use higher-rate internal springs or additional shims to increase spring rate. This increases the "pop" pressure, which is the fuel pressure at which the nozzle begins an injection cycle. Higher pop pressure may improve atomization and combustion efficiency. Hi-pops may work fine when used with a healthy fuel injection pump, but they could also contribute to poorer starts or no starts, especially on a warm/hot engine if the injection pump is too worn. This is because an aging fuel injection pump might not be able to generate the fuel pressure it must to "pop" the injector at a typical 180-200 rpm cranking speed.

Many stock 6.5TD's dyno at about 160 rear wheel horsepower. I've been present at dozens of dyno events where, through the years, hundreds of 6.5L diesel powered trucks and Suburbans were dyno'ed. I absolutely know what they are capable of. Here is a series of questions that you should ask any vendor who wants to sell you a set of non-stock "performance" injectors for your 6.5L diesel.

1- What exactly is a 40 hp 6.5 injector?
2- Would they produce a 25% gain in horsepower from just a simple injector swap?
3- How are they different from a stock injector?
4- What is the flow rate for a stock injector, and what is the flow rate for a "performance" injector?
5- Does modifying the 6.5 injectors for additional fuel flow affect fuel economy or cold/hot startability?
6- Are there any dyno graphs - anywhere, that show a performance gain when comparing new stock injectors to new performance injectors?

Let me know if anyone knows the answers to these questions.

Maybe we need to do a product review. I now have access to a local Mustang chassis dyno...

Jim

[gmctd]

That would be interesting to compare a hi-mileage DS4 against a new or rebuilt version, both with standard injectors, then with hi-pop hi-flows, while connected to a scanner to catch the differences in idle rpm and timing.

Most of what we do is recognizeable by the PCM, which can compensate, accordingly.

PCM has no way of recognizing changes in injector pressure or volume - this is easily seen at idle, where PCM manages idle rpm on a per-cylinder basis.

So - what's it all about, alfalfa?

It would be some interesting tests.

[JeepSJ]

Yeah, I saw that post regarding the 40hp injectors and thought the same thing. Would it not be possible to put the 6.5 injectors through the same process to increase their flow?

[grape]

the volume comes from the stroke of the pump.........period. the larger nozzle decreases dwell time and makes the combustion and injection time "quicker" in crank degrees. So as to not be peeing fuel in while the piston is already way to far down to do any good............other than smoke and egt.

i doubt you'd see any power diff on the same engine.

[gmctd]

Except that the stronger spring delays injection while the pump is still building pressure to 'pop' that spring.

The volume between 1700psi and 2200psi is then lost - PCM doesn't know about that and doesn't compensate with the Fuel Solenoid - it is a fixed beginning\variable ending injection system.

Beginning of injection event, PCM closes FS, rollers are rising on the ramp, plungers are pumping their specific volume against the closed injector, building pressure.

At 1700psi inj pressure, injected volume is from that point on the ramp until PCM opens the FS at some point further up the ramp, ending injection.

At 2200psi, the rollers are further up the ramp when injection begins, but PCM still opens the FS at the same point further up the ramp.

PCM can attempt to correct for that at idle with the Cylinder Balance routines, but that's only at idle, used to maintain idle rpm in Neutral, Drive, A\C on or off or cycling, headlites on or off, anything that varies the load on the engine.

Even at that, hi-pop hi-flow injectors do not idle as smoothly as the standard versions, nor is idle speed stable, and can vary by 100rpm low.

Those Cyl Bal routines are not used off-idle.

The Injection Fuel Rate seen on the scanner is not measured - it is calculated, based on conditions with oem standard lo-pop injectors, spec'ed by engineering to ensure the camring and rollers would survive thru the warranty period, while still giving adequate spray pattern for economy.

'Course - I'm talking EFI DS4, you're talking mechanical injection DB2.....period.......and, as we all know, turning up the fuel on the DB2 effects the fuel rate from idle to full throttle, right?

That's why I would like to see dyno results compared to scanned data.

[Robyn]

I have talked to mark at Diesel fuel injection service in Portland about just such things.
His comments have been that these fancy injectors are real good for making more power in the sellers wallet.

I think its a gimic.
The DB2 Or DS4 was designed to run at a certain pressure and be able to deliver a pre determined amount of fuel as its max capacity and to have nozzles that are designed to work with these pressures and volumes.

I somehow think that maybe there are still folks out there that are trying to relate the nozzles of the 6.2/6.5 to the old "Injectors" of the 2 stroke detroits where they were the nozzle and the pump all wrapped into one.

We were always bumping the injector size on our little 318 Detroits a couple sizes to get a few more ponies, and usually a ton of black smoke in the process.

The little 6V71 I had in my first bus was set up with "city injectors" and IIRC it was rated at 260HPThe thing ran clean and got about 10 MPG on the road at 55mph at max governed speed of 2100 RPM.
Little Detroits were a happy little camper if you let them run at 2100 all day long.

Yup I think these so called performance injectors, at least considering how they are being marketed are just a waste of $$$$.
I will stick with locally rebuilt units that are set up to book spec for the engine.

I always ask Mark to be sure any he does for me are all to the top of the spec for POP pressure and that they dont vary much.
I am a firmy convinced that having the injectors matched closely is a good idea for engine durability.

If one or two are on the low end of the scale and the rest are scattered out with one on the high end it will IMHO make for a rougher running engine especially at idle.

Having the injectors all at the top of there spec does aid in good cold starts.
The spray is finer and easier to ignite.

If you could get some of these 40HP injectors it might be interesting to do some HP and mileage tests for sure..

Sounds like some of the goodies JC Whitney used to sell, maybe they still do.

Robyn