Duel fuel line mod M818 855 cummins

[350TacoZilla]

I had talked about this in a 923 turbo thread and no one knew what i was talking about I'm going to tackle this project before adding a turbo or even driving my truck again, I cant see a reason not to ( basically free HP, less egt spikes from cyl to cyl, smoother idle,better mpg) . I think even if I would gain 0 hp but gain atleast one of the other benefits it would be worth it.

 

[patracy]

Well well, I got the plug out of the back head! I twisted up my nice allen key set doing it, but it's out. I had read online that placing a dab of lapping compound would give it a little extra "grip" instead of rounding off. I ended up twisting my allen key set about 180*, but the head retained shape and it all came out in one piece. I'll take a deformed allen key set over drilling and tapping any day! The tee is made up and plumbed into the PT pump. The line to the back head is installed as well. Got the front line disconnected and the factory port out. I'm going to have to pick up a street elbow or use a male to male and female to female to extend the front away from the head enough. The rear installed just fine.

I used 3/8 inverted flare steel lines for the fuel lines. One was 40" the other 30". The tee is a 1/4" NPT. I used 1/4" to 3/8" Inverted flare adapters out from there to the lines. The adapters at the heads are 1/8" npt to 3/8" flare. (Plus remember you'll need to space out the front head fitting.) I used a 1/4" npt to a JIC adapter to plumb the tee into the adapter that comes out of the emergency stop valve. (It has a O ring and a straight thread)

Ron, I'll report back on the power after this mod. I'm not expecting a great deal of power, but I can certainly see how it would affect things. (Common rail diesels routinely have to increase pressure and volume to ensure fuel delivery for upgrades) If in the least, it will certainly benefit the HT3B turbo that will eventually come to it. Again, I'm not looking to try to make a NHC 250 into a 575hp turned up big cam. I just want to have about 300hp, which should be very obtainable. Mainly to compensate for the power loss I'll see when it's completely swapped to a M931A1.

 

[swbradley1]

I'd like to do this but the cutting holes and breaking tools all while trying to get a little plug out bothers me. I understand the reasons behind wanting to do it and it certainly sounds like a good idea but all we have so far is anecdotal evidence, no proof of the mod doing anything (other than holes and aggravation).

Dyno tests would prove HP changes and dB sound pressure levels from a meter at certain points around the engine may show that it runs smoother but everything said so far is subjective.

There may very well be a big difference on a higher HP engine but on a 240HP engine is it really going to make a difference.

 

[Maxgussam]

That, and the opinion of 73M-819 is the reason that I decided not to do the mod.
My truck has enough power to do what I need it for anyway.
I pulled a 46k fertilizer spreader that was buried to the frame in mud out. This was going uphill through 6" of mud, so it works fine as is in my opinion.

 

[patracy]

Well unfortunately I have no chassis dyno to test this on (nor would I have previous results). However, I do know what the truck drove like previously. Horsepower wise, I doubt I'll feel anything. But I would suspect a little more torque (from what I've seen in the past playing with common rails). I also am not of the mindset that a cold air system and an exhaust and tuner will add each of their advertised power increases. (I learned that with my dodge)

I won't sugar coat anything. I'm pretty unbiased on my documentation. (Work Habit) I will tell you honestly if I see any improvement, any loss, or if I can't tell a difference. Like I mentioned earlier, I mainly took on this mod to help complement the turbo that is to come.

 

[patracy]

Well preliminary results are in.

1. I'm a dummy. I crossed the lines up front and left one line loose causing me to pump about 3 or 4 gallons worth of fuel on the ground wondering why it wouldn't start.

2. When I realized what I did. I plumbed everything back correctly. (Bottom most post is the fuel feed line) And she roared to life.

I need to get more fuel now, so I'll probably make a weekend joyride out of it. (There's some decent hills between here and the truck stop)

I can say this much though already. I do detect a improved throttle response. It will rev to 2300rpm a bit faster than previously. I know that's kinda subjective. But I can tell a difference.

Also idle smoke is down greatly. And it does seem to not lope at all now. Again, these aren't measurable results, but my subjective opinion. But I honestly didn't do this for reduced idle smoke or less lope.

 

[doghead]

Do you think you could have incidentally repaired some pre-existing air leaks, while doing this modification?


and thanks for the additional sigline!

 

[patracy]

Do you think you could have incidentally repaired some pre-existing air leaks, while doing this modification?


and thanks for the additional sigline!

If there would have been air leaks, I would have seen it with slow starting/rough starting prior to the mod. It has always started within a second or two of hitting the starter.

The only existing lines that were touched was the front line, that line has been replaced. All other fittings have been reused. If anything, I was introducing more points to leak at.

A road test will be the final answer. I will update the thread then.

 

[M813A1]

Well you already boosted the fuel pressure in the fuel rail just by routing the fuel from both directions !! I bet that was a big help to the engine by itself ?? Another simple trick used by the old time Road drivers was to take a dime and drill a hole in it and then remone a fuel return line fitting and reconnect after putting the dime inline. That would also help the fuel back pressure to the fuel rail and raise your fuel pressure!!

 

[Maxgussam]

Well you already boosted the fuel pressure in the fuel rail just by routing the fuel from both directions !! I bet that was a big help to the engine by itself ?? Another simple trick used by the old time Road drivers was to take a dime and drill a hole in it and then remone a fuel return line fitting and reconnect after putting the dime inline. That would also help the fuel back pressure to the fuel rail and raise your fuel pressure!!

Ha!
I heard about that trick from a guy that drove for my Co. before he retired.
He couldn't stand the DOT anymore, not to mention what he called the "New Breed" of drivers.

 

[patracy]

I encourage everyone to go inspect their 250's. Since there's three heads to it. Not only does the fuel go into the head up front. But to connect the heads together are two U shaped lines. So by the end of #6. That fuel had to 90 into the head, flow across two injectors, 90* inside the head, then 180* out into the next head, 90* back down into the rail, pass two more injectors, 90* out, 180* U bend again, 90* back into the third head, then hit the last two injectors.

Now the fuel in my engine 90*from both ends into the two end heads. 90*'s back out of each of the end heads. 180's on both of the heads. 90* again back into the head, then each feed would hit 3 and 4 respectively.

I'm no fluid mechanic, but I know the stock way was a lot of turns for the fluid to travel.

 

[juanprado]

Could you post pics of where you had to cut and the size at the doghouse? Also pics of the set up as this sounds very doable.

Thanks!

 

[Cycletek]

Would there be enough room to put the fuel lines into the two lines between the front and middle head and the middle and rear head? I believe this may make it easier to get more fuel to all three of the heads. I will have to look at this possibility on my engine. That means no need to remove the rear plug and you could just plug the front. I am going to look at my TM I printed out...... OK I looked it up and found it to be a couple of looped tubes with a 4 bolt flange, I am going to pick up a couple to see if I can duplicate it in an aluminum block and and tap it to accept a fuel line fitting.......worth a shot if it adds some performance and drivability......

 

[patracy]

Could you post pics of where you had to cut and the size at the doghouse? Also pics of the set up as this sounds very doable.

Thanks!

I will document with pics tomorrow. Been on the road most of the day today. Still need to make up my patch panel and install it.

Would there be enough room to put the fuel lines into the two lines between the front and middle head and the middle and rear head? I believe this may make it easier to get more fuel to all three of the heads. I will have to look at this possibility on my engine. That means no need to remove the rear plug and you could just plug the front. I am going to look at my TM I printed out...... OK I looked it up and found it to be a couple of looped tubes with a 4 bolt flange, I am going to pick up a couple to see if I can duplicate it in an aluminum block and and tap it to accept a fuel line fitting.......worth a shot if it adds some performance and drivability......

Wouldn't be possible to plumb between the heads unless you redesigned those hooped tubes. The plugs in the heads aren't accessible when installed.


Now for the part everyone has been waiting for....

I *think* there's a little more power. No, not earth shattering amounts. More smoke has been noted out the exhaust. The truck pulls harder in the lower and mid range. But I don't believe there's been any top end fueling improvements. But thinking it through, that's exactly what *should* happen. The PT pump is only going to allow so much flow for max output. This is typical results from my dealings in the common rail 5.9 cummins when rail flow has been increased.

I've got about $40 in this mod. I know the truck's throttle response has increased. I believe I gained a slight bit in the mid range. Would I tell everyone to do this? No. Am I happy with the results? Yes, $40 has given me some benefits. I've spent more than $40 on parts for other things and not found any improvement. Would this be a worthwhile mod for a stock truck? In the grand scheme of things, most likely not. Would this be a good mod for a truck that will be turboed? Yes, I believe so. Would this complement a truck with a different button? Yes, I believe so. Would this complement a truck with a shimmed gov spring? Yes I also believe so.

So I can't give you a scientific answer by any means. But I believe the right path to turbo'ing a 250 would include this mod. (As well as a button and gov spring swap)

 

[FireFighterHill]

I wonder if making a Fuel Manifold would make a difference run the supply to a block with enough ports to feed each cylinder individually. This would make sure each cylinder is getting the same Fuel Pressure and volume.

 

[patracy]

I wonder if making a Fuel Manifold would make a difference run the supply to a block with enough ports to feed each cylinder individually. This would make sure each cylinder is getting the same Fuel Pressure and volume.

I don't believe the benefits would outweigh the cost of that.

 

[swbradley1]

Ok, so in case you may have changed my mind do you have exact part numbers for all the fittings you used?

 

[patracy]

Ok, so in case you may have changed my mind do you have exact part numbers for all the fittings you used?

Honestly no, I don't have any part numbers. I simply walked in and knew what I was looking for.

From the emergency cut off valve I used the following parts.

JIC flared fitting to 1/4" NPT adapter
1/4" NPT tee
1/4" NPT to 3/8" inverted flare adapter (two)
one 20" 3/8" inverted flare steel line
one 30" 3/8" inverted flare steel line
two 3/8" inverted flare to 1/8" npt adapters
one 1/8" npt male to male nipple
one 1/8" npt 90 or straight female to female coupler

Everything except for the JIC flared fitting was purchased at the local auto parts store. The JIC flare to NPT I got at the local hyd. hose place. But if you're buying from a NAPA, I'm sure they'd have that. (Or a parts store that does hyd. hoses)

 

[M35A2-AZ]

Great info.!!!

 

[FireFighterHill]

You should be able to use a billet fuel rail as long as it has enough ports. What is the PSI being supplied through those steel lines?