OK, bear with me - crazy ideas ahead!

[94DieselSub]

So over the years quite a few people have tossed the idea around of direct injecting a 6.5 via c/r injectors adapted to fit down to were the cups reside. This has yet to physically manifest its self due to high cost, complexity, and the need for a dmax or aftermarket pcm & whole-lot-of-tunning to make it work.

So there's that.
But what if a much simpler route of implementing high pressure c/r injection were pursued?

OK - here comes some crazy!

What if:
(1.) A cp3 pump were to be installed.
(2.) C/R injectors that were actuated by electrical signal only (not electrical over oil hydraulic).
(3.) Said injectors were only actuated on wot demand, within a defined upper rpm window. They would run 100% duty-cycle when on (saturated). IE, stupid simple.
(4.) Said injectors (only 2 or 4) were installed in tig welded bungs in the 6.5's upper intake manifold just post turbo (think like water/meth injection).

Now this arrangement is not a ecm/pcm controlled fuel addition. Rather a Nitrous Oxide like wot only, on/off extra 100HP of injected diesel fuel on demand.

I also think a simple time delay circuit could be implemented to phase in the second half of the injectors. This simple staged injection approach would allow the turbo to spool up without rolling coal like an unlimited sled-pulling rig.

And yes, I'm quit aware that I'm not the first to propose such insanity! But there's enough evel-knievel type experimenters on these forums who might just try it!

A possible secondary benifit might be a slight charge cooling effect. As c/r injection produces a micro-droplet fog rather than a spray like a idi. This fog has much higher temperature volatility, thus gas phasing could occur due to the turbo's discharge temps.

Anyway,
That's my crazy post for the day!

 

[MrMarty51]

How about exchanging positions between the glow plugs and the injectors ? would that make it a true direct injection unit ?

 

[93detroit]

I would think that your diesel-enriched air would begin to burn before your piston hit tdc. Same problem as running too high of methanol content in a w/m system.

 

[Will L.]

I would think that your diesel-enriched air would begin to burn before your piston hit tdc. Same problem as running too high of methanol content in a w/m system.

YUP. Getting it to not be a smoke show or burn excessively soon is a pain. I tried this before going to what @MrMarty51 said.
Getting a ton of fuel into the cylinder can be accomplished by a healthy built db pump and opening up injectors. Then spray the propane in the intake to help burn it all.
Just understand you are going to learn the same way I did: by destroying 8-9 blocks.




Trying to go Di on this engine is a neat theory. Many talk about it but once the get $25000 into it they pitch the idea. What you are really talking about is carburizing the engine or throttle body injection. Gasoline engines are far easier to control because you can choose the exact moment the fuel ignites- not so on diesel.

Think about how long the tbi engine lasted and compared to older carburetor ones and later di ones. Does it function? Yes is it really an advantage? No. No engine runs tbi now for a reason- to hard to control. The few advantages it has over carburetor pale in comparison to di. It’s all cool in theory, but you are looking at quite the endeavor.

 

[94DieselSub]

Yeah you guys got me - damn injection timing thing - total brain fart on my part!

You might get away with it on c/r engine due to the very low compression ratios. But unfortunately y'all are right, on an idi the charge would cumbust on the upstroke (btc). This is catastrophic detonation, like holes in the sides of your block kind.

TBI was phased out due to ever tougher emissions standards, not mpg, control schemes, or performance. Actually if you ever drive a tbi chevy 350, I think you'd be pleasantly surprised by the midrange tq.

 

[Rockabillyrat]

I've though about a common rail system for a 6.5. The biggest hurdle are the injectors.

Here's what I came up with.

Mount a cp3 in the valley. Duramax fuel rails and of course you would have to build all the HP lines to connect everything. Then use all the engine sensors from a lb7. The cam and crank sensors need tone wheels. I think the duramax crank wheel could be machined to mount on the balancer much like a Cummins. Then make a mount for the sensor. The cam wheel would have to be custom made. I think you could machine the cam gear for the tone wheel to mount to. Then make a sensor mount on the timing cover. Control it with the duramax ECM/IDM, tune it with efi live, and run a standalone TCM or a nv4500.

But the injectors are the part that makes it impossible. They would have to be completely custom made. And that's way beyond my skills or wallet.

 

[94DieselSub]

@Rockabillyrat,

Yes a massive dmax c/r to 6.5 retrofit could be feasible given enough r&d and cubic-$. But at that point I think I'd just run out and grab a nice clean LBZ truck and call it a day.

At 1:00AM stupid crap like that seems like genius concepts - till you think through the next day! Oh well :-(

I'm still wondering if an old idea of mine (less stupid) could be pulled off without damaging parts in the process?

People who have experienced runaway PMD's have almost unanimously stated the 6.5 will pull harder than wot could ever normally achieve! Although the psychological impact of such an even might distort peoples perceptions of things, with the adrenaline rush and all.

So I was thinking the PMD Fuel Solenoid command pulse feedback signal could be artificially generated by delaying the command signal via small and cheap microcontroller. This would replicate a normal PMD feedback pulse timewindow loop to the ECM/PCM so no error codes, defueling or retarded inj timing.

Meanwhile the fuel solenoid could be energized at 100% duty cycle, thus making your poor DS4 squirt out as much fuel as possible per given RPM. This alternative FS energizing could be carried out by somthing more robust than a PMD, say like an SSR which are also cheap. The output of the PMD would have to be temporarily bypassed. This transitional period might cause issues though. Like the PMD output stage might go into oscillation without a normal FS load, or at least a resistive dummy load.

This would obviously have to be a time limited engagement, like hill climbs or hwy on ramps only. What I don't know is if the FS thermally could even take it for a few minutes without cooking the windings? The max normally commanded FS duty cycle is most likely less than 70%?

Just another half-baked idea of mine.

 

[Rockabillyrat]

With custom tuning you could command 100% duty cycle and not cause a defuel. Although its probably not good for the solenoid life spand. But it's not going to gain you much. The DS4 is limited by the cam ring. There is no way to physically increase fuel volume on a DS4 other than changing cam rings. Most "HOT" DS4s are just calibrated and tuned to make better use of the fuel volume the pump already has. Because a DS4 fills the pumping chambers 100% every charge cycle. If you swap to a more aggressive cam ring you can increase fueling dramatically.

The downfall to a aggressive cam ring is the increased ramping rate and pumping volume add alot of rotating resistance to the rotor. Enough to over power transfer pump pressure and rotate the cam ring thus making very unstable timing.

 

[Will L.]

The piston design of the lb7 is required to deal with those injectors at that pressure. It simply needs that volume inside the piston to direct that fuel burn. The more- flattop design of the 6.5 is part of our worse rattle sound. As anyone here that has ran loads of fuel and propane to help burn it can tell you, that rattling gets scary loud. It is not fun when it gets bad, then you open it up to see the valley side of all 8 pistons were kissing the walls from that extra side load. A piston design like that would require shorter rods, but shorter rods allow for higher rpm. idk cp3 rpm capabilities at all, but if 6,000 is capable, Il tell you what, this engine that far bore over stroke- there is all your hp gain for hiway use or end of track everyone wants.

Cutting up precups to barely seal the head and open up room for di injector to fit is doable, and is just cash. Machining the metal to fit the engine and adapt to an existing injector is t a crazy thing to do. Just having the parts in your hand in a junkyard or Autoparts store can quickly rule out or show possible options. By memory of swapping lb7 injectors, simply taking an old 6.5 injector housing, welding it near solid, then drill out an machining to hold the longer and skinnier lb7 injector in it with machined surface for the oring to seal. The factory hold down clamp might get ‘buried’ but making a different hold down bracket that is like a boxed end wrench over the higher part on the main section would be easy enough.
The really someone with descent tig welding skills and a tiny harbor freight lathe could make that adapter. Oh, to install/remove the adapter piece intk the 6.5 head, just spanner wrench style holes inside the bore above the oring sealing surface, and a spanner wrench with spreading screw to hold in place for the force. Someone diy tig and machining out the adapters alone should be under $500 in materials to figure out. Once made accurately, beat treat and chryo and they should be fine.

I don’t want to discourage someone from trying something. But just realize that even if you get the fuel system working perfect first time out, serious engine damage is likely while figuring things out. So build the heads to go on junkyard short blocks until you have it very controllable.

The cam sensor is easily done off oil pump drive. Crank sensor is just machining a different reluctor wheel.

 

[94DieselSub]

I could be mistaken but I thought I've read in the past that gm ecm/pcm capped the max "tunable" FS duty cycle in the code. I also seem to remember tuners explaining that, that part of the code is not the typical variety which they would alter.

Something like machine level code for a pc, its something most code-heads don't deal with.

But on a stanadyne pump test-rig I bet you could effectively drive the FS 100% on?

Custom aggressive rotor cams I'm sure are out there, but the mtbf goes from years to months. I suspect even with the hardened ceramic "arctic" upgrade parts. There are oem larger diameter plunger/rotor assemblies, but they're as rare as unicorns and I believe were mfg for marine applications.

I also seem to recall talk of possible cavitation/fuel vapor bubbles at high rpms being caused if the FS assy failed in the on position. Although I have nothing to substantiate that hypothesis.

I think I originally tossed this idea towards quadstar or somebody years ago. They mention the unnatural pwr during a pmd runaway event. So I thought to myself - well hell, what if we could produce that effect on demand.

 

[94DieselSub]

@Rockabillyrat,

I apologise for my earlier response to you, I poorly wrote that (was in a hurry and at work)! And after getting home and reading what I wrote, I realized I unintentionally sounded really rude to you - sorry about that!!!

I didn't mean your dmax to 6.5 c/r convertion concepts were "stupid crap"! It sounds to me like you've put a lot of educated thought into the subject.

Rather, I meant to write that my 1:00am idea of direct injecting diesel into the intake mani like nitrous oxide was retarded.

 

[Will L.]

@Rockabillyrat,

I apologise for my earlier response to you, I poorly wrote that (was in a hurry and at work)! And after getting home and reading what I wrote, I realized I unintentionally sounded really rude to you - sorry about that!!!

I didn't mean your dmax to 6.5 c/r convertion concepts were "stupid crap"! It sounds to me like you've put a lot of educated thought into the subject.

Rather, I meant to write that my 1:00am idea of direct injecting diesel into the intake mani like nitrous oxide was retarded.

Well the base idea of having atomized fuel in the intake so there is more over all fuel getting into the cylinders isn’t all bad. It requires more steps to keep things safer like reed valves in the intake to guard fuel back to the turbo. And having that fuel supply shutoff a minute before the engine shuts off the Each time and not engaging until the engine has been running a minute, or only engaging above say 1500 rpm.
Propane or nos or wmi gets intake sprayed often just fine. But it takes much more fuel to have the same effect as say a little nos. But spray pressure has to be so much higher with the thicker diesel fuel that it makes it difficult.

But most people dont build a 6.5well enough to o handle max fueling that can be had from a ds4 or db2. A fully built 6.5 running very efficiently can gulp down some fuel. Think about N8in8or’s build and recall he hasn’t installed his wmi system yet which helps a lot. Get the ip he has dialed in then the wmi up to a 50/50 mix and when all that isn’t enough for him, there is still propane. Then above that is nos. And all that can be done quite reliably on the street. Once the street is and long engine life are out if the question- nitropropane awaits!! Haha

 

[94DieselSub]

@Will L. ,
You beat me to the response, well here's what I was pecking out on my cell phone:

My original hairbrained idea seems to have sparked some conversational interest in the idea of a real 6.5 C/R conversion.

And while the scope of that project is well outside of my sphere of available time and budget, I'll throw in my 2-cents.

The IDI design relies on a very high compression ratio to vaporize, and then autoignite the coarsely sprayed fuel. It is also how the IDI 6.5 makes the power it does. If you lowered the comp ratio down to dmax levels (16:1), and some how got the fuel to light off, the hp/tq would be miserable!

Most IDI's also utilize some variant of the Ricardo bowl type piston along with a pre-cup.

All of the above would be a disadvantage to C/R injection. Without drastically reducing the 6.5's compression ratio, I fear that the common rail's ultrasonic-like fog of fuel would ignite waaaaay before TDC.

Of course this would result in the rods/crankshaft performing a JATO to the ground in record breaking time. Like Will L said, best to have a pile of disposable engines before embarking on such a project.

If only there were an auxiliary (non-timed) injectable power adder like nitro-propane, nitro-propylene, that wouldn't toast your engine! It would be so easy!

Years past, Audi was dominating American Lemans racing with small'ish rev-to-the-moon "diesel" engines. Their secret was their proprietary "diesel" rocket fuel mixture. It sure in the hell wasn't anything reassembling #2. Probably had nasty chemicals like hydrazine in it.

 

[94DieselSub]

To further expand what I was saying about unattended ignition way before TDC.

Yes a tune could attempt to radically delay the C/R injection event(s) to prevent this in an IDI platform.

But I highly suspect the remaining time left to complete the injection would be too small. What would result is half the injection event would occur ATDC. Resulting in poor economy, performance, and very high egt under load.

Although, I'd place a Vegas bet that after a certain engine speed (>6000RPM), if the engine could handle that speed, continuous intake injection would be viable. The combustion cycle is so short at those engine speeds, what normally would produce catastrophic detonation would now be just about a normally timed diesel ignition.

 

[94DieselSub]

Holy cr@p my brain works much better before midnight!

That's it, No more late night postings for me!

I think my drunken weekend posts are far more coherent and thought out!

 

[Rockabillyrat]

No need to apologize lol

But I never said anything about converting the 6.5 to DI with the common rail system. I would leave it an IDI with stock compression. The cp3 is capable of 20,000psi. The DS And DB max out at 8000psi. So the whole system could be tuned to run 10,000psi max. Lb7 injectors won't work because the they have a multi orifice nozzle. You need to build a single orifice injector to mimic the original injectors spray pattern. Then you could tune the pilot injection to mimic the flow rate of the throttling pintle found in our injectors.

Even if you got a lb7 piston and injector to fit the angle of the injector is in the wrong spot. The injector needs to be centered in the combustion chamber for the fuel to hit the piston in the proper location. So a full custom head would be required. And at that point just durmax swap it. It would be a better idea to leave it an IDI and work around that style engine.

I thought about the cam sensor off the oil pump drive. But the pattern needs to be identical to duramax so the ECM doesn't get confused.

The DS4 only ever cam with one plunger size (.310) like I said the only way to increase fueling is to change the cam ring. The DS4 was available with a few different cam rings and none of which are aggressive enough to cause the pump to prematurely fail. The most aggressive is found in the 6033 pump that was put in the p400. The DB2 had a few different plunger sizes and configurations (.290 .310, .330, 4 plunger. 310) also had a few different cam rings available. The most aggressive are found in the 4911 and 5079 pumps. But I'm not sure why people think these are "unicorn" parts. One call to my stanadyne rep and I can have the parts I need to build a hot DS4 or a 4 plunger DB2. I have the complete parts list ready to go for my 4 plunger build that will be ULSD compliant. I think the reason you dont seen many pumps built with these parts is the cost. Not many are willing to spend over $2000 on a pump for a 6.5.

Oh and if you want to go full potato on a pump build. Certain cam rings can be machined to work in different pumps. That's how guys are getting huge fuel numbers like the pumps R&D builds. But that may lead to shorter life of the pump. I haven't seen feed back on how long the RD4180 is lasting.

 

[Rockabillyrat]

Just for comparison. Here is a DS4 cam ring vs a DB2 cam ring. You can clearly see why a DB2 with outflow a DS4. The DS4 may have two more plungers but the DB2 has twice the plunger travel. That is the less aggressive ring out of a 5521s. I dont have any other DS4 cam rings at the moment. But you can see why upgrading to the more aggressive DS4 cam ring is a must if you want more performance.

 

[Rockabillyrat]

Sorry I kinda took this thread off topic from the common rail conversation to DB and DS pumps. I was just tring to show why 100% duty cycle on the FS won't gain you much in performance.

 

[Will L.]

We all know I am the king of taking any conversation sidetrack. Friends remind me that trains have tracks not tractor tires for a reason! We all love the info and thoughts you share, so don’t stop.

So, Now I get what you were after keeping idi... for several years a lot of us got into sky high pop pressures on the injectors.

Boyles law iirc more pressure and same size opening is less volume. So marine injectors is bigger hole, you can keep pressure the same and increase volume or increase pressure (for better atomization and quicker burn) and same volume.
So i get why the dmax injectors is a thought to go for if di, but if staying with idi and after way more power than stock, bigger injector port and nozzle than the marine ones. That moves up the volume, increase spring tension for higher pressure and it’s advantages. The drawback (providing you can burn that added fuel) is the ip load. So if your familiar with the cp3, what about just adding one component at a time- the cp3.
I’m sure the factory return lines on injectors needs addressing so they dont blow off.

The higher pressure cp3 can surely solve the issue of trying to run monster hole idi injectors at a high pop pressure without the start issues that have gotten way worse with this new fake diesel fuel.

Machining larger injector nozzles and using top quality material should be far easier now with all the advancements in machinist equipment. Yes having them made would cost a pretty chunk of change. If needed the bodies could be remade to deal with the higher pressure return lines out the injectors. That much increase in volume and pressure may just mandate it.
But solving this combo could make for profit in the market. Not because there are so many wanting their 6.5 to have oodles of power, but a cp3 kit and injectors to replace the one day nla pump and rotor issue... Then the added ability for more power is a selling point instead of the main point. I imagine it will be some time before the cp3 market goes away.

Now- one thing is, the cp3. If you are adapting in a different pump- is there a better pump to go to? I could be mistaken but seem to recall an issue or two with the cp3 and it’s injectors.

 

[Rockabillyrat]

Sometimes its fun to take crazy ideas and roll with them. The common rail 6.5 just snowballed one night while I was researching injection pumps.

We dont have to worry about pop pressure on a CR system because the injector will be opened and closed electronically. Injection pressure will be equal to rail pressure. If you ran 6.5 injectors on a CR they would stay open anytime rail pressure is above pop pressure. If you could somehow replace the top part of the injector with an electronic solenoid that controls the needle. Then you could possibly use parts off the stock injector. But with constant rail pressure to them you would have to make sure they don't return too much fuel. Which would cause a low rail pressure issue. also finding a solenoid that is fast enough for multiple injection events in the same compression stroke is another challenge. So developing new injectors might be easier, but no less expensive.

Also all 6.2/6.5 injectors have the same orifice size. Even the marine injectors. All Bosch did was change the pintle design and needle lift for more flow. I do plan on increasing the orifice on my prototype injectors 30% though since my DB2 will flow near triple the stock pumps output.

The CP3 is a great pump to run. They don't have the issues the CP4 did. And they are designed for 20,000psi operating pressure. So we wont cause any added stress on it running 10,000psi. Could you imagine 200cc at 4000rpm on a 6.5!! We would be blowing up block daily LOL!!