Since I have no experience with an automatic I can not say for sure the VRV is anything, but I do seem to remember VRV stands for variably regulated vacuum for the C6 modulator valve.

I have seen directions about adjusting them and the vacuum numbers you should see, but since I will never own one I just read through the posts.

Send PLC 7.3 a PM, I think he is the one that posted the info about adjusting it correctly. The pressure switch tied into the oil system is a good idea, so is the master switch to disable everything in case of trouble.

I can almost see a stepping control tied to the IP throttle linkage that used micro switches to control the different propane levels.
Problem is when you take off from a stop and floor it, you go to max propane delivery while the engine RPM is way to low.
That would require a much different driving style than the one I use most of the time when towing or loaded heavy.

 

Pretty close - certainly the same idea

Good point, hadn't reallky thought about that. Of course the same would apply to the VRV idea.

Gonna' have to noodle on how to integrate the RPMs into the metering equation. Maybe by creating some kind of circuit to sense RPMs off the tach sender and using that signal to cut the power to the system below a set threshold value....

 

OK, I think I have a couple of systems worked out. Basically the way it would work would be it would have multiple gas solenoid valves to control the gas flow.

It would take input from both the tach signal and throttle position to determine which/how many solenoids to turn on and therefore how much propane flows into the intake.

I've worked out everything I need to get and how to set it up one of 2 ways.

A 2 solenoid (3-step) system that that works like this
1st stage kicks in when RPMs get above 900 or if throttle is more than 3/4 open below 900 RPMS
2nd stage kicks in at 1700 RPMs or if throttle is more than 3/4 open between 900 and 1700 RPMs
3rd stage kicks in at 2500 RPMs or if throttle is more than 3/4 open between 1700 and 2500 RPMs

A 3 solenoid (4-step) system that works like this
1st stage kicks in at 900 RPMs or if throttle is more than 1/2 open below 900 RPMs
2nd stage kicks in at 1500 RPMs or if throttle is more than 1/2 open between 900 and 1500 RPMs
3rd stage kicks in at 2100 RPMs or if throttle is more than 3/4 open between 1500 and 2100 RPMs
4th stage kicks at 2700 RPMs or if throttle is all the way open between 2100 and 2700 RPMs

I've also worked out a 3 solenoid SEVEN step system, but given the relatively narrow range of RPMs that our engines are operating over (900-3300 RPMs), I think that would be overkill.

Really the only thing that still remains to be worked out is what kind of output signal I can get from the tach sender (current, voltage, or frequency), and what kind of circuitry it will take to manipulate that signal into a form I can use.

The system would be customizable in that the gas flow output from the solenoids would be through needle valves - allowing it to be fine-tuned to the engine.

So, what do you guys think? If I can do this successfully, and were interested in building, packaging, and selling a system like this, what would it be worth to you as NA IDI owners? Is it worth the additional complications and expense to do the 4 stage system over the 3 stage?

What I'm wondering about is the possibility of selling complete systems from the regulator to the intake. Basically everything but the propane tank.

What do you think it would be worth?

 

This is starting to sound expensive.

 

Actually it might not be that bad, I have seen the solenoid operated valves for anywhere from 50 dollars down to about 10 dollars each.

The throttle switch would take a little planning, but once it was past the prototype and fine tuned it should be easy to reproduce.

Electronics are not that expensive to build, Radio Shack has plenty of parts to build the prototype, then you can order parts from a supplier to get better prices after it is debugged.

 

Exactly. Like any electronic device or system, the cost is in the R&D and building the first prototype. After that it's pretty cookie cutter, and buying parts in multiple quantities - even 10 pieces at a time - can cut the costs to produce additional units. Of course the labor to build the units is still there, but, if you're building 10 at a time of something, you get faster at it too.

The basic principle of the system amounts to taking a voltage signal from a potentiometer (like the volume **** on your radio) connected to the throttle as a throttle position sensor (TPS). Then taking a voltage signal from the tach - converting it to voltage if it isn't already - and combining that with your TPS signal voltage, and feeding that combined signal into the input of an an analog to digital (DAC) chip. The binary output of the DAC is then used to drive relays that turn the solenoids on and off. As with most things the devil is in the details.

You have to get both the tach and TPS signals into the right range, 0-1v for example, and you have to properly decode the binary output to trigger the right solenoids at the right RPM & throttle points. You also have to manipulate the pressure on the input side of the solenoids and the oriface sizes on the output side of the solenoids to get the right amount of propane flow for the conditions.

The system I've devised should be very flexible with adjustable propane input and output pressures and flows. It would also allow you to "tweak" the RPM and throttle signals to change when the solenoids turn on, and lastly you would even be able to adjust WHICH input - RPM or throttle - has the bigger effect on when the propane comes on. The control box would be mounted inside the cab - probably on the dash. I'm thinking something like a 2"x3"x4" black box (give or take an inch in any one direction) with two cables coming out of it - 1 pull-type cable and an electrical cable with several wires in it. The face of the unit would have 1 green and 3 red LEDs - green for the power "ON" indicator and a red LED for each level of boost.

FYI, just so no one thinks I'm blowing smoke here, I have a degree in Computer Engineering and a second degree in automation. I'm not sharing that to toot my own horn, just to say that I'm about 95% sure I CAN really do this. However, it is going to take a LOT of work and tinkering to build and tune the first one. Assuming I do perfect the prototype, and get it working well on my truck, I will be interested in offering to build and sell them to others. I'm thinking about maybe say, 6 months from now.

Would somewhere in the $300-$400 range be reasonable for a 3-stage system like what I describe above? Like I said, it would be a complete system ready to install, and complete with installation and tuning instructions along with everything you'd need except the tank. I even have a name picked out for it - the TRIPLE SHOT.

So, what do you guys think? Would anybody around here pay the price I'm suggesting for the system I've described?

 

CheaperJeeper, I sent you a PM to really start you thinking and offer a different idea for your consideration.

 

PM-ed you back Dave. Amazing how much our thoughts/ideas run in paralell!

Anybody else got a comment on the system/price of what I'm describing? The more people interested the less it will cost per system to build.....

If you think the suggested price is too high, no problem, just say so. I won't be offended, and even if the idea isn't marketable, that certainly won't keep me from building one for myself

 

Why do feel you need to increase your engine's power? Increasing a diesel engine's power with propane can result in a catastrophic engine failure, which is definitely not covered by your warranty.

While there are many commercially available propane injection systems for diesel engines, this fuel is poorly suited for compression ignition engines. Even though propane has a high octane rating (resistance to self ignition), it is not high enough for the high compression ratios common in diesel engines. This means that propane will knock severely when you add enough of it to the diesel engine's air supply.

While the Mr Sharkey LPG article does provide some useful information, he presents a system that uses portable cylinders. These are dangerous and illegal (non-compliant with NFPA 58). Do not use portable DOT-style fuel tanks in a motor vehicle.

Stationary industrial engines are often dual-fueled with natural gas because natural gas has a higher octane rating than propane. These engines are specifically designed for this purpose and use a pilot (small) diesel injection to light the fuel mixture.

Franz Hofmann wrote an excellent diesel dual fuel FAQ on the Eng-Tips forum. I suggest you read the FAQ before you modify your engine.

 

Do you have one of these older trucks? If so, one has to wonder how you can ask this question. Less than 200 HP to move 7000 pounds of steel (more if you use it for towing - as most of us do)? If you drive one, the answer should be pretty obvious.

It sure can - BE CAREFUL. A pyrometer is a must.

WARRANTY?!? LOL! Dude, my truck is 20 years old! ALL of the trucks owned by people in this forum are at least 12 years old. Warranty isn't much of an issue for us. Know your audience

Ummm, YEAH, if you don't do it right, it sure can. That's one of the reasons I'm not planning on using a mixer - see previous posts. My plan is to meter propane the same way that the diesel is metered - based on RPMs and throttle opening - again see previous posts.

First off, there isn't a commercially available system for the 6.9 or 7.3 non-turbo IDI.
Second, we aren't talking about running on straight propane - though there is plenty of good info on the 'net about how to do that if a person wanted to.
Third, the idea here is to add small, appropriately measured amounts (around 20%-25% BTUs worth of propane relative to the BTUs of the diesel) to suppliment the primary fuel (diesel) and promote more complete combustion. Not just to dump large unmetered amounts into the engine and let it ping itself to death. BTW, this principle is well documented - lots of info on the net about it.

True. However, I carry a camper on my truck and it has one of those cylinders in it. That is perfectly legal. Motor homes carry them. Heck, before I had a camper I carried one loose in my vehicle when going camping. Millions of vehicle transport them safely every year. What would you propose to do? Make hauling them around illegal? My point is that if properly mounted and protected, that isn't really much of a concern or problem - though it is true there is the question of legality once you connect the cylinder to your engine.

Again, he is talking about dual-fuel systems where the engine runs on diesel OR CNG - not using CNG to suppliment the diesel. So your point here is....what? That our engines aren't stationary, that CNG is better for diesels than LPG, or that the stationary engines are "designed" for it - meaning they have some things added to their fuel delivery and control system to make them suitable for gaseous fuels - and our engines aren't? BTW that is a pretty good description of what we are really discussing here - modifying our engine's fuel delivery systems to make them more suitable for burning small amounts of a gaseous fuel (LPG).

Interesting article. A couple of things about it aren't really applicable in this case though. He specifically states right up front that he is talking about modern engines. Our IDIs are at least a 20-25 year old design - probably even older than that. Not quite what he's talking about. The older designs like our IDIs aren't nearly as efficient as the newer ones he's talking about, and do exhaust more unburned fuel than the newer engines - certainly more than the .001% number he quotes.

Also he states that 'Propane is NOT used as a catalyst to "more completely burn the fuel"'. Which is true in the strictest terms (see his chemistry definition of catalyst). The propane is not a catalyst in that it doesn't modify the actual chemical reaction of combustion - just as he states. What it does do - due to its quicker, hotter burn characteristics (what he refers to as combustion pressure rise time) - is add a bit more heat to the combustion process and a little earlier in the combustion cycle. Of course this must be done in small amounts to prevent predetonation. As I understand it, that is how and why it helps with more completely burning the diesel.

Also, as he states, diesels normally operate in an "excess air" mode - meaning there is more air available than there is fuel to mix with it. Adding small amounts of propane (fuel) is just taking advantage of that fact to make more power - pretty much just like he said.

Not trying to be mean or anything, just trying to
a) understand where you're coming from and
b) help you see where WE are coming from and
c) show you that most of us in this discussion have a pretty good grasp of the concepts, and lastly
d) point out that everything Mr. Hofman states in his article doesn't neccessarily apply to this situation/discussion.

Hope I haven't offended you, just wanted to address your points.

 

I'm not offended. Sometimes there's a frenzy of enthusiasm for an idea that sometimes ignores the risks. My concern with a DIY system is that even though a little is good, a little more can be too much and this can be very tempting with a dashboard-mounted dial.

While I know that these vehicles aren't covered by warranty any longer, others with different vehicles may also be following this forum. I should have worded that point a bit differently.

About the quote regarding the mixers, I started writing a reply to this article when it was on its first page. I only noticed the subsequent postings after my reply was posted so I immediately deleted that paragraph.

Regarding the fuel tanks, ASME rather than DOT fuel tanks are legal for motor vehicle fuel tanks. If you have an accident and your insurance company investigates, you may not have the coverage you were expecting.

 

Yeah I guess I should have worded my earlier posts a little more carefully as well. When I'm describing being able to adjust the system I have in mind, I'm talking about inserting a 1/8" wide screwdriver through holes in the side of the control box to turn adjustment screws for fine-tuning things like RPM range and throttle opening required to activate the stages of the system. Not a dash-mounted dial. You're right - that would be WAY too tempting for many people. For flow rates, the adjustments would be made at the solenoids mounted under the hood - again, not something you could do "on the fly" while driving.

Gotcha'

OK I see now.

True. That's why the system would be supplied without a tank. That decision would be left to the end user - with the appropriate liability-deflecting warnings of course

 

i dont have any degrees and only a couple years of diesel related experience but I've been thinking alot about propane lately... I'm thinking this through as I write so I can only hope it will come to a useful conclusion.
The "engine and fuel engineering faq" presents some troubling points:

-propane displaces air (increasing air volume and flow is the goal of all intake and exhaust mods, proven to help efficiancy)
-propane has less energy for the same volume of diesel

...so if there is enough air available to burn the propane why not just inject more diesel and burn that instead, his logic is far too simple because if it worked exactly the way he lays it out, propane would not increase horsepower at all under full throttle conditions where you are putting out more diesel than can be burned completely (black smoke).

The "fact" that propane does increase hp even in applications where diesel injection is increased to the point of ineffient burn leads me to the conclusion that its not really that all the available air is used up but that conditions in the combution chamber (heat/pressure) have simply lessened to the point that what air is left will not readily combine with th diesel. If this is accuate then actually injecting propane at the corect moment to extend the combustion process seems more beneficial than fumigation. Also infinately more complex and expensive... similar to the newest high pressure injection systems with multiple injection events.

The more I read and think about the whole idea the more confused I get, and the more i wish i had access to a dynometer and a set-up to experiment with... Mabey the "fact" i mentioned earlier isnt a fact at all. Mr. Sharkey's page on propane fumigation states "Nearly no increase in power will be noted at full throttle, assuming that your injection pump is correctly adjusted already" is this because the added hp is proportionally less or because there isn't enough air to burn both fuels resulting in no REAL gains. if there are really no gains at full throttle there are no real gains at all. the addition of propane is no better than increasing throtle position.

The only way propane fumigation has any real benefit is if it really does allow the diesel to burn more efficiently rather than just giving that apperance due to decreased smoke. Its only logical that smoke will be reduced if you inject propane (a very clean burning fuel) instead of more diesel.

The simplest way to prove one way or the other is to measure egt versus dyno tested hp/tourqe using different combinations of diesel and propane. If you can get more power out of an engine by adding propane without raising egt it must be running more efficently (according to my logic anyway). Reducing emisions doesnt come into the equation for my definition of efficiency. Catalytic converters reduced gassers emissions but reduced actual efficiency.
Apparently the conclusion I hoped for was not to be. All I got is we need accuate impartial testing... if anyone bothers to read all this please point me to some reliable data on the subject so i have something besides theoretical thinking to back me up.
dave mcguire

 

guppy,

I have a Bullydog Propane injection system on my IDI and I have to agree to most of what that artilcle says...I want to point out that I do not have a turbo and I belive to maximize propane injection, a turbo is a must.

What I have experienced [towing my 5th wheel] with propane injection is not so much as HP gain but MPG gain...empty, not towing any thing, it goes like a bat out of hell but thats not why I bought a diesel, I bought it to tow.

I'm looking forward to see what kind of results I'll get when I install a turbo...I don't expect mind blowing HP's but in a turbo application, I belive I will be "dialing down" the amount of propane injected with greater results?!

 

how long have you had your system installed? does the increased mpg actually pay for the propane you are using? I am tempted to put a system on my 84 volvo 760 turbo diesel (no laughing, i kinda like it :P. even if power isn't increased much having a reasonable amount of power without black smoke would be nice on a car. But it seems like if you dont mind the smoke the same power could be acieved by adding more diesel. Unless the propane does improve burn efficiency signifigantly.
Forgive me for the rambling last night btw, it was late and i was feeling a little loopy.
dave mcguire