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Discussion Starter #1
I've got 180K on my 12 valve now. I've got all my upgrades in my sig, and I'm thinking about injectors for two reasons. 1) My mileage is suffering, I can only get about 16mpg empty, and i used to get 19mpg stock. 2) my tailpipe is smokey and I would like to clean it up. I have a number 10 plate that is only about half full forward. I'm thinking that at 180K my nozzles could be burnt. Also I think that my pump is well capable of over-fueling my stock injectors.
Main concerns: EGT's, fuel mileage, power. In that order. Also my boost only runs about 7psi cruising down the highway, I would think that it would be a little higher, but that's another story.
I'm leaning towards sdx 5x12 injectors. Looking for advice on injectors, if that's what I need. Also thought about advancing my timing more, have it set at 15.75 deg. The wastegate on my new turbo is set at 40 and i'm somewhat worried about my stock head gasket and stock head bolts.
 

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7psi at cruising is normal. Imo i would back down the turbo to 35psi just to be safe. I have the plate pulled and i dont get smoke till I step on it. One suggestion is keep a eye on the k&n intake if you have the k&n filter, they dont like turbos. Had to clean and oil mine every 3k and thats all highway driving.
 

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first things first, fuel filters, overflow valve and or fuel pressure, also try checking to see if your fuel shutoff solenoid is adjusted properly, some of guys i talked to at the bosch dealer say that after 200k injectors will start to loose their pop and new ones are a good investment. also retorque your stock head bolts to 125 lbs and thatll do ya well.
 

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Well you don't neccesarily need new ones... You can have your current injectors rebuilt or pop tested to see how they are. You have a 215 pump and 215 injectors and thats a good thing as far as that goes. I agree with 12valveterror, Fuel pressure should be a thing you should check and have a gauge for. Don't waste money on filters of overflow valves that don't need to be changed. Pre-filter would be a good thing to clean.

What color of smoke? The psi at cruise will effect mpg. Also EGT at cruise. You want less. I think 5 psi and less and 600* and less is best for max mpg. Maybe more timing is in order...? I would look more at fuel pressure first, then go to the nest step. Throwing $450 worth of injectors at something you don't know is going to fix the issue, seems kind of wasteful to me.
 

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Discussion Starter #5
exactly what i'm thinking dieseltech. Was thinking i need more timing. Have been thinking on the fuel pressure gauge for a while. Does anyone know if you can get the autometer three gauge pillar pod for the second gens? Should I run a mechanical or electric fuel gauge? Any advice on that one would be appreciated. My other gauges are autometer phantom II. Overflow valve and lift pump are both fairly new. Smoke is black, some light colored smoke on cold start up in winter. Will change fuel filter and see if that helps, been on this one for about 8K and it might be dirty. I haven't driven my pick-up without a trailer in forvever so I couldn't tell you what cruising egt is off the top of my head.
Also like the idea of retorqueing head bolts, do you just retorque them or do you pull them one at a time and oil them? what would be best?
thanks
 

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for retorquing the headbolts its up to you, but i would pull them and dip them in motor oil get them tight to about 100lbs then go in 5 lb increments to 125 and follow this sequence>>
 

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I would definitely get the timing done and check fuel pressure then go from there.
If your current injectors provide enough power for you stick with them.
 

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Discussion Starter #8
Any suggestions on the amount of timing?
 

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15-18 degrees should be good
 

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any decent shop will tell you 15.5 to 16.5
 

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Discussion Starter #11
I checked it again and i am running 15.75 right now. I need to add that to my sig.
 

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Discussion Starter #12
hey kronic 187 how do you like those sdx 5x.014 injectors? I've been thinking on those or 5x.012. Did you notice an increase in egts, or mileage gain or loss?
 

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mileage is better on the hwy @ a steady speed if anything.... if you keep your foot in it, mileage drops.... EGTS go up yeah, of course.... running them with this hx35 sux right now, but i got my afc set up pretty tight to tame them a bit....

i'm happy with them, they haze a touch for about 45 seconds or so until i idle it up to 1000rpm for a min or so, but thats to be expected.

big power bump and they burn real clean compared to some injectors i've seen....
 

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Also thought about advancing my timing more, have it set at 15.75 deg.
You guys who are telling him to change his timing, need to learn to read.
This is in his 1st post.

That is an ideal timing setting for stock injectors.
It's also a very good medium setting for big injectors.

Once you do get injectors, maybe bump it up 1-2º or if you feel like going nuts, heck push it to 20º or more, but timing has nothing to do with your problem if you're indeed at 15.75º.

FYI: Timing isn't exactly a precision process, you can say you have it at 16º. Just round up.

The wastegate on my new turbo is set at 40 and i'm somewhat worried about my stock head gasket and stock head bolts.
The guy who told you to lower it to 35 also didn't read your post or your sig. He thinks you have a stock turbo! :lol2:

You could push that thing to 45-48PSI easy.

And for best HWY fuel economy, it's best to keep your boost around or below 5PSI. And you aren't going to see cruising EGT's below 700ºF unless you're either running compounds, water injection, a big intercooler or all of the above. So whoever said 600º EGTs are ideal for cruising, I don't know what kind of fueling you have, but it must be all stock.

You could have old worn-out injectors and that's why your MPG's are suffering now. But it could be so many other things doing it.

I can assure you, your 16º timing is perfect. Don't touch it!
 

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Also, I'm wondering if your turbo (turbine wheel) sizing spec is wrong in your signature.

I thought the HTB2 was a 62/71/13... your sig says "62/64/13ss".
That's a mistake right??

I haven't heard of a 62 w/ that small of a turbine wheel.

And I was thinking about possible causes of bad fuel economy and they can range from bad wheel bearings and dragging/rubbing brake pads to who knows what... and then obviously there are the usual suspects like tire pressure, but you seem to have covered the rest except maybe fuel filter... the K&N could be getting clogged too.
 

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Discussion Starter #16
Yes it is a mistake but it's a 62/65/13. Been thinking of upgrading to 71 at some point and that's part of the reason I bought the high tech was they give you room to grow fairly cheap.
The truck is in good to excellent mechanical condition (new hubs, fairly new brakes, 80psi tires, fairly new not real aggressive tread.) I'm really leaning to worn injectors.

Thanks for the input everyone.
 
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Once you do get injectors, maybe bump it up 1-2º or if you feel like going nuts,.
Depends on the pop off pressure. High pop off pressure can take away more timing then most think

And you aren't going to see cruising EGT's below 700ºF unless you're either running compounds, water injection, a big intercooler or all of the above. So whoever said 600º EGTs are ideal for cruising, I don't know what kind of fueling you have, but it must be all stock.
Mine cruised at 700ºF...

Cam, head work, and low cruising boost will see lower then 700 easily.
 

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Depends on the pop off pressure. High pop off pressure can take away more timing then most think
I don't see any reason to debate this. The O.P. is having an issue. People ignored him saying his timing is verified at 16º and they recommended him up his timing to fix the problem.. as though his timing was stock (or slipped).

My point is that his timing is fine. He might bump it to 17-18º if he gets injectors and that is the 1-2º I was talking about, but at 16º he's not going to be getting crappy mileage due to a timing issue.

I'm just trying to be the voice of reason and help him get to the bottom of his problem by eliminating non-issues that are just adding confusion.

Mine cruised at 700ºF...

Cam, head work, and low cruising boost will see lower then 700 easily.
Yeah at 700º.
I said, to see lower than 700ºF is gonna be difficult, let alone below 600º.

I would call cam & head work difficult.

And he was saying 600º or less is better... my point is that number isn't exactly realistic or attainable... and it's not necessary or the reason for the O.P. only getting 16MPG's.

I used to get 700º cruising down the road in my stock (turned up pump) truck myself and it got 22MPG.

Now with hot 5x12's I get 750-800º cruising. You're not going to get below 600º on a single w/ 5x12's or 5x14's unless you go to great lengths. And it doesn't really matter for MPG's (whether you're cruising at 600º or 750º) is the moral. OK?

Keeping the boost below 5PSI, I will definitely agree with that being the key MPG factor.

And keeping your EGT's at the bare minimum (for your setup) is great because that's running at highest efficiency & minimum load. That gets you good MPG's for sure.
 

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Could someone explain the logic in thinking that low fuel pressure from the pump, a partially clogged fuel filter or a fuel solenoid not fully open could cause low mileage? These are diesel engines so IMO a lack of fuel would only result in low power.

I had very little decrease in mileage when my original injectors had 570k on them. I never had them pop tested but I could see with my nakes eye that the holes had enlarged from the hundreds of gallons of fuel that had been forced through them so I am confident that the spray pattern was less than optimal. I did experience a small loss of power when I installed a new set of 215s but the haze went away also.

Increasing timing could decrease mileage if the engine isn't running at the RPM that the timing is optimal at. That is why I get better mileage at 2000 rpm than 1700, even though it is commonly accepted that lower speeds will provide higher mpg.
 

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Depends on the pop off pressure. High pop off pressure can take away more timing then most think.
I know that 260bar is stock pop-off.
What do you consider high pop-off, 300bar?

Weston set mine to 280bar, so I'm just wondering how that pertains to mine and my 17º. I would think it would be a minimal effect. But maybe that's why he was pretty adamant about me setting the timing to 18º. Maybe the 280bars bring it back down to 16-17º.

What do you think about that?

Could someone explain the logic in thinking that low fuel pressure from the pump, a partially clogged fuel filter or a fuel solenoid not fully open could cause low mileage? These are diesel engines so IMO a lack of fuel would only result in low power.

I had very little decrease in mileage when my original injectors had 570k on them. I never had them pop tested but I could see with my nakes eye that the holes had enlarged from the hundreds of gallons of fuel that had been forced through them so I am confident that the spray pattern was less than optimal. I did experience a small loss of power when I installed a new set of 215s but the haze went away also.

Increasing timing could decrease mileage if the engine isn't running at the RPM that the timing is optimal at. That is why I get better mileage at 2000 rpm than 1700, even though it is commonly accepted that lower speeds will provide higher mpg.
That's really interesting. Good points.

I have gotten better mileage on road trips where my veggie oil filter is clogged and I'm running very low pressure going into my P-7100. It basically keeps the boost under 10PSI no matter what. Unless I flick the switch back to diesel and then it's like hitting a Nitrous switch. :lol2:
The amazing thing about a P-pump is they don't suck themselves to death. They can suck fuel at 0PSI and the only problems are A: if you work it hard in that state (no incoming pressure) it cavitates the plungers (over a long time) and B: the upper section of the pump is lubricated by return fuel and it will lack the extra lube fuel and may heat the pump up and accelerate wear.

Your theory of timing changes effecting peak-efficiency cruising RPMs is one I've never heard before, but it makes sense.

But wherever in the RPMs, the peak torque occurs, that's where the cruising RPM's (especially un-laden) yield max MPG's according to what I've heard & read. The torque peak is very low (low-mid 1000's) whereas the HP peak is upper 2000's) depending on timing and other things.
 
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