Cummins 4BT & Diesel Conversions Forums banner

101 - 118 of 118 Posts

·
Registered
Joined
·
52 Posts
Ok, if converting a diesel to cng, could you also include a wvo system to ignite the cng? Also, since there are hp gains with cng, could you manually shutoff injectors to a few cylinders, to further decrease fuel consumption? Ie...variable displacement diesel that burns cleaner than prius lol, with maybe water/methanol injection to keep egt's low...:idea:
WVo should work.
My cars use a simple aspirated system that feeds CNG in just before the turbo, so shutting off injectors would just be wasting CNG. If you went with a more expensive CNG system that used individual CNG injectors it might be possible.

I may pursue water injection on CNG in the future for fun. Not at all needed, but could allow for higher ratios of CNG in pulling or racing situations. ( neither of which apply to my daily drivers). :)
 

·
Registered
Joined
·
49 Posts
Water inj: I suggested it in order to keep temps down, and a few more pony's never hurt ;) , could cng be plumbed into individual intake manifold veins in order to prevent 80% waste on valves you didn't want to receive cng? Or would it require a better vacuum source? Btw i'd probably never afford this mod, just piqued my interest in low cost of fuel(higher cost to convert), and ways to produce same power with half the engine firing...
 

·
Registered
Joined
·
52 Posts
Water inj: I suggested it in order to keep temps down, and a few more pony's never hurt ;) , could cng be plumbed into individual intake manifold veins in order to prevent 80% waste on valves you didn't want to receive cng? Or would it require a better vacuum source? Btw i'd probably never afford this mod, just piqued my interest in low cost of fuel(higher cost to convert), and ways to produce same power with half the engine firing...
I'm not sure how well it work. Doubt it would be worth the trouble for anything short of a factory installation. The big names are starting to get into the dual fuel game: http://marinelog.com/index.php?option=com_content&view=article&id=2335:cummins-to-launch-high-horsepower-dual-fuel-engine-line&catid=78:oil-a-gas

In a way the CNG does allow you to make the same power using very small amounts of diesel.

The only thing more ponies hurts is transmissions!! :) I am trying to take it easy on mine so it lasts a long time. My truck makes 800ft/lbs of torque from the factory and this is plenty!! With CNG the motor probably makes around 1100ft/lbs of transmission destroying torque!! Gotta be careful.

goincommando- this is my daughter's license plate:


My weekend is going to be wiring up the new 3800 Series 2 motor we just dropped in. Fun, fun...
 

·
Registered
Joined
·
5,528 Posts
could cng be plumbed into individual intake manifold veins in order to prevent 80% waste on valves you didn't want to receive cng?
absolutely, this is currently one of the most usual setups in aftermarket cng conversions
 

·
Registered
Joined
·
49 Posts
I was considering possibility of running an om617t with 3 cyl being fed cng, 2 blocked off with valve in individual injector lines to stop diesel feed, custom intake with individual butterflies to stop air flow/cng suction into undesired cyl, with water injected ports and a blower instead of turbo for forced induction, and to assist exhaust flow...sorry for run on sentence, but actually had a thought there, and you could always turn fuel valves and open butterflies to feed all 5cyl and leave your clutch in ashes...
 

·
Registered
Joined
·
52 Posts
I was considering possibility of running an om617t with 3 cyl being fed cng, 2 blocked off with valve in individual injector lines to stop diesel feed, custom intake with individual butterflies to stop air flow/cng suction into undesired cyl, with water injected ports and a blower instead of turbo for forced induction, and to assist exhaust flow...sorry for run on sentence, but actually had a thought there, and you could always turn fuel valves and open butterflies to feed all 5cyl and leave your clutch in ashes...
One of the reasons a diesel is more efficient is that there are no pumping losses due to throttle plate restrictions. My hunch is that you would be better off keeping it simple and running all 5 cylinders on a CNG to diesel ratio that keeps the motor happy. Water injection with CNG is something that I have considered, but there is zero information out there concerning the combination.
 

·
Super Moderator
Joined
·
8,672 Posts
I was considering possibility of running an om617t with 3 cyl being fed cng, 2 blocked off with valve in individual injector lines to stop diesel feed, custom intake with individual butterflies to stop air flow/cng suction into undesired cyl, with water injected ports and a blower instead of turbo for forced induction, and to assist exhaust flow...sorry for run on sentence, but actually had a thought there, and you could always turn fuel valves and open butterflies to feed all 5cyl and leave your clutch in ashes...
Hang on a minute.
Different combinations in different cylinders are going to run *extremely* rough.
Blower instead of turbo, means high fuel consumption.
Throttled intakes, mean high fuel consumption.
Water injection? Why? You can apparently run gas engines lean to control EGT in exactly the same way diesel does.

Why not just meter the gas into the intake like everyone else? Keep the turbo, keep all cylinders the same and tune EGT on fuel.
 

·
Registered
Joined
·
49 Posts
Like the older rat rods I was thinking of individual intakes per intake valve, making a hp custom exhaust manifold, and was bouncing around idea of cng to all 5 intakes but was wondering could it run on only 3 cyl in which only 3 are fed air and fuel, then later connect throttle to all 5 intakes and make a fuel thirsty power monster....Morocco and some othe african countries make you pay a fee based on displacement and horsepower, like 6500 dirhams or $800 to get a 4cyl HYUNDAI TUSCON in...there are loads of om617 but are well over 500k mile mark and power mass transit taxis lol, and making a blower work on 5 individual intakes only make me consider sealing and height issues,....
 

·
Registered
Joined
·
49 Posts
300+ hp diesel but run on 3 cyl only= produce stock hp rating...and fair level of economy with $6-10/gal of diesel in Morocco, and occasionally "give her all she's got" when your out with "polite society" who have a couple vw v10 touregs
 

·
Super Moderator
Joined
·
8,672 Posts
Like the older rat rods I was thinking of individual intakes per intake valve, making a hp custom exhaust manifold, and was bouncing around idea of cng to all 5 intakes but was wondering could it run on only 3 cyl in which only 3 are fed air and fuel, then later connect throttle to all 5 intakes and make a fuel thirsty power monster....Morocco and some othe african countries make you pay a fee based on displacement and horsepower, like 6500 dirhams or $800 to get a 4cyl HYUNDAI TUSCON in...there are loads of om617 but are well over 500k mile mark and power mass transit taxis lol, and making a blower work on 5 individual intakes only make me consider sealing and height issues,....
300+ hp diesel but run on 3 cyl only= produce stock hp rating...and fair level of economy with $6-10/gal of diesel in Morocco, and occasionally "give her all she's got" when your out with "polite society" who have a couple vw v10 touregs
Back the bus up a minute.

I can't see them giving you any fee discounts for having a 5 cyl engine only running on 3-4 cylinders. Otherwise people would be pulling spark plugs to rort the system (no officer, it's a 2 cylinder really). The balancing and firing order of the engine is all designed around all 5 cylinders firing evenly. Any attempt to run on fewer cylinders will at a minimum shake stuff to pieces (likely crack engine mounts etc) and at worst possibly do a crank.

You are not going to get 300hp from an OM617 running on 3 or even 5 cylinders of anything.

Valves in injector lines will cause rupture of the injector lines or the pump. If you want to cut off fuel to a cylinder on a diesel, you need to deactivate the pump barrel. Blocking the line will just spike pressure until something breakes.
 

·
Registered
Joined
·
49 Posts
They strap it, kinda, to a dyno and check hp if its foreign, otherwise they have a numbers sheet for all mercedes, peugot, lr...euro models
Didn't take post injector pump pressures into consideration, t1 steel motor mounts that are 5/8" thick and brace both sides of wrangler frame will keep it in place regardless of vibration, however the rubber would likely shear...variable dispacements have been done in v8's why can't diesels be done? And sorry for veering way off topic of mech or elec pump cng, but was considering that since cng is usually a hopped up or extremely efficient (costwise anyhow) diesel combustible fuel, similar power characteristics of running alcohol in a blown gasser, could it be achieved? I do know if throwing enough money creates a solution or money pit, was just pondering...
 

·
Super Moderator
Joined
·
8,672 Posts
MYNA pump? Anyhow was asking 'IN THEORY' if a "variable displacement diesel" could/can be achieved while running cng...
Crunching some numbers.

These engines produce max power at 4000rpm, their BSFC efficiency there is 300g/kwh.
To deliver 300hp (222kw) at 4000rpm requires 530Nm.

To get 530Nm from a 3 litre diesel at 4000rpm will require around 59psi boost, 44 lb/min of airflow and 130cc/1000 shots of fuel.
A Myna pump might get you that much fuel. But good luck holding the engine together. High compression idi diesels do not mix well with high boost pressure.

That is on all 5 cylinders. If you want to drop to 3 cylinders, everything gets a lot worse. You now have a 1.8 litre engine which requires ~125psi boost, 217cc/1000 shots fuelling to deliver that same power.
 

·
Super Moderator
Joined
·
8,672 Posts
The displacement on demand engines cut out cylinders in a way that'll keep the resulting engine reasonably well balanced. On a V8 you can cut out certain groups and get away with it at lower power outputs. At higher loads all cylinders are firing.
 

·
Registered
Joined
·
5,528 Posts
Water injection with CNG is something that I have considered, but there is zero information out there concerning the combination.
basically, a water+meth setup and a cng setup have the same effect into a diesel, so it would be pretty much redundant to have both systems, unless you would get a setup similar to the one used in some newer cummins-westport engines which cng is directly-injected before the regular diesel (instead of sprayed into the intake manifold)
 

·
Registered
Joined
·
41 Posts
The displacement on demand engines cut out cylinders in a way that'll keep the resulting engine reasonably well balanced. On a V8 you can cut out certain groups and get away with it at lower power outputs. At higher loads all cylinders are firing.
Yeah, for example GM LSx V8 engines with AFM/DOD cut out cylinders 1,4,6 and 7. It's done via VVT, where both exhaust, and intake valves are closed with collapsible lifters so the pushrods can't open the valves. Also the ignition and fuel supply are closed. All this happens within 250 milliseconds in cruising speed.

To make some old 5-cylinder diesel work like DOD... impossible.
 
101 - 118 of 118 Posts
Top