CNG Injection

[sms8921]

I am going to be installing a CNG injection unit on my 94 td. I want to run as little diesel as I possibly can. How would I turn the fuel down to do this? I was thinking with the fuel screw on the pump but I wasnt sure if you can turn it down too much and the screw come out of the mechanism inside and it fall apart without pressure on it. 50% CNG/50% diesel is what im hoping for after installing.

 

[Agnem]

I'm a bit confused here. Are you saying you are going to run your engine on a fuel (natural gas) you are going to feed through the air intake? Doing this, you will have no throttle control through the injection pump, so messing with the fuel screw does nothing for you. You would just not press the throttle pedal. There is a whole lot more questions than answers going on in this thread so far!

 

[sms8921]

my CNG injection has a regulator that determines the amount of cng to flow into the intake by the amount of air flowing through. The more air flow the more cng it injectes. I just want to know how to reduced the amount of diesel fuel going to the motor beings im going to be injecting cng into the intake. I want to lean the engine out.

 

[Goose_ss4]

Id say turn it up to not burn the cylinders. Although we burn diesel it does lubricate the inside alittle. Cng will heat things up to so id watch .

 

[Agnem]

The diesel takes in the maximum amount of air ALL THE TIME. It is not like a gas engine where the inflow of air is restricted intentionally. At idle, it sucks in the same volume of air as it does at full throttle. The only thing that changes is the CFM due to engine revolutions. So you cannot really control the air/fuel ratio.

 

[cr430c]

50% CNG/50% diesel is what im hoping for after installing.

In order for this to work properly you would have to inject into the cylinder not the intake. Just like Mel stated I've got more questions running thru my mind than answers for you. I think before you decide to do something like this you need to do some more research on how it all works. It's not just hook up and go. For CNG you will have a hell of a time getting it into a tank without having a station nearby or paying thousands to get a station for your home. I'd say read read read. Then decide.

 

[ocnorb]

I am looking seriously at doing this also. Many CNG stations here and the price is around $1.43 GGE right now.

To the OP: You don't need to do anything with the diesel fueling on your truck. The amount of fuel will be controlled by the throttle pedal. When CNG is flowing you will only need to push the pedal half as far to get the same power. As Agnem said above there is no throttle plate in a diesel- its full air all the time.

My system will incorporate 2 extra safety features. There will be a shut off valve tied to oil pressure and boost so that no CNG can flow at idle or when the truck is not running. I consider this to be the most important part. I will also have a CNG tech inspect my installation prior to putting any fuel in it. These guys are relatively easy to find here in Utah.

Another thing you need to consider is that CNG can easily detonate at high flows and loads- this will generally mean a blown head gasket. My CNG system will be set up to deliver the highest CNG/diesel ratio at highway cruise speeds. As you demand more power you actually need to taper the CNG off or your peak cylinder pressure will get too high. Its readily accepted that 50/50 CNG/diesel at cruise is safe, but at any other load you should not go over 30/70.

CNG has a compression detonation factor near 15:1, so you have to take care running it in one of these old 21:1 and higher trucks. It will effectively advance your timing too far.
Propane is worse with a 13:1 detonation factor, which is why you hear so many horror stories from guys that have tried it.

Good luck and keep us posted.

 

[ocnorb]

In order for this to work properly you would have to inject into the cylinder not the intake.

Not true. Look at Deluca CNG systems. He has gone over 70% CNG into a Dmax using a simple mixer pre-turbo. He used to have some good pictures of his set-up on the net, but he has taken them down now that he is making money on the systems. His new system uses a knock sensing device to actually tune the CNG flow delivery to maximum possible without detonation issues.

The only downside to not injecting directly is the time time lag from when you let off the throttle until the fuel stops being pulled into the cylinder. (Based on the time it takes to go through your turbo, intercooler and piping.)

Have a look at RASO's Red Rooster system also. Its not out yet, but the tech sheets have a ton of good info.

 

[sms8921]

I have a compressor and a tank, I just need to see if it is safe. I dont want to blow head gaskets and I get what you are saying now about the fuel issue. Is it safe to use with propane at all or only natural gas?

 

[ocnorb]

The guys selling them say they are safe... but you must consider that most of their customer's trucks don't run as high of compression ratios as a good ole torquey IDI. It may ok at a low level, but who wants to be the guy that finds out what that level is?

 

[oregon96psd]

Make sure you video tape the first start of this thing The term runaway diesel comes to mind.....you say that
your kit decreases the amount of cng when the airflow slows, if you rev a diesel and let off the fuel what slows the airflow? It seems a hole lot like once it starts speeding up and increasing flow/adding fuel it wont stop until the crank flies out the bottom.

 

[tanman_2006]

I have considered doing this on my 6.5's. The 94 and 95 yrs leave room for multiple tunes that could be set with progressive fuel cut backs and an adjustable cng regulator *** in the cab would be possible. My only change to the typical system would be having 1 nozzle in each intake runner, as close to the head as possible.

Still has alot of kinks to work out I'm sure. Filling up won't be an issue though.

 

[ocnorb]

Nope. There are lots of installs that have been running for years. The CNG is controlled flow, not just rampant fuel input. Some kits use a stepper motor, some use vacuum referenced from ahead of the turbo. Once the pressure is dropped from 3000psi the rest of the system is the same as propane. Some of the kits use the old Impco propane regulators.

 

[ocnorb]

I have considered doing this on my 6.5's. The 94 and 95 yrs leave room for multiple tunes that could be set with progressive fuel cut backs and an adjustable cng regulator *** in the cab would be possible. My only change to the typical system would be having 1 nozzle in each intake runner, as close to the head as possible.

Still has alot of kinks to work out I'm sure. Filling up won't be an issue though.

Not in OK!

 

[88beast]

sorry diesel knock sensor thats funny like a smart blonde