Y’all will see me posting a little more than usual over the next few weeks. I have time away from work and need to get some things done on this truck. This is where I’d like to hear opinions: 

 

With good tuning and 7x.010’s can I get better top end for towing grades? To be more specific, I’d like to maintain speed (65 mph) on sub 1 mile 6%-8% grades towing 9K without having to downshift. Subjective I know, but can this be accomplished through tuning, injectors, and my hx35w, or do I need more turbo? 
 

Off the highway I tow with od locked out, and if it’s really steep in the mountains somewhere I use 2w low. The problem I’m looking to solve is specifically interstate/highway towing. 

 

Before Mike asks, 285/70-17

Good place to start

 

 

 

here's the result of your setup

 

 

 

The short if it is at 65 mph you do not have enough RPMS to tow up grades without downshifting.    rpms need to be up at or above 2k to prevent heat build up from lugging.  

 

your only real choice is 4.10 rear end if you dont want to downshift.  or just lock out OD and let the motor work like it was designed to do.  No amount of tuning, injector, turbo combo is going to overcome the lack of RPMS.   

 

 

You can ask @dieselautopower if the 57 gxe turbo  would get into its map fast enough prevent egt issues at 1600-1700 rpm while towing grades, but I wouldn't think it would.

Edited January 24, 20223 yr by Me78569

I was hoping you’d chime in @Me78569 good info. The frustration here is everything is 1/2 mile up then 1/2 mile down over and over and over.  I can build speed coming down and almost make it up the next one and then have to downshift. Still always gets me there I guess. 

I don't mean to be contrary but, the best way is to not be pushing the Cummins for everything she's got all the time. It will save you a lot of trouble in the long run. Best way of taking the long grades hauling heavy is click down into tow haul and go about 50/55, enjoy the scenery. I cringe when someone goes by hauling a big RV, pushing the engine for everything it's got. It's not the way to treat an investment meant for the long term. I don't mean to stir the pot here... just sayin'.

its easier on everything to just gear down and let it work.  3rd is 1:1 ratio, od is .69:1 so the struggle bus is a long heavier in OD. 

Edited January 24, 20223 yr by Me78569

10 minutes ago, JAG1 said:

I don't mean to be contrary but, the best way is to not be pushing the Cummins for everything she's got all the time. It will save you a lot of trouble in the long run. Best way of taking the long grades hauling heavy is click down into tow haul and go about 50/55, enjoy the scenery. I cringe when someone goes by hauling a big RV, pushing the engine for everything it's got. It's not the way to treat an investment meant for the long term. I don't mean to stir the pot here... just sayin'.

Not contrary at all. If I’m on a long grade I take it slow, and if I’m towing my horses I always take it slow. But I’m talking about short up and downs where I need a little more top end to crest the next hill without losing momentum and downshifting. So like 30 seconds of pushing it and then coast back down. My brother is an excavator and a lot of his guys have been out sick lately so I’ve been dragging equipment around to help him out. That’s what’s got me thinking about it while I’m getting ready to swap the original injectors out and all that. This truck works, but isn’t abused I promise. 

I see where your coming from. You know, there's too many guys out there that push an engine for everything  its got. I can see you are reasonable about it now that you explained. Your talking about getting over the hills with the ups and downs not long steep grades.

Yea it seems I’m just barely outside the sweet spot a lot of times and lose speed then drop to 3rd. Not the end of the world, just hoping I could cure it with tuning and maximizing the stock turbo since I’ve never even pushed it past 20 psi. And honestly I have no issue dropping a size in tire, but the ones on it are pretty new.  

dropping tire size will help, I dont know if it will be enough though.  

 

gearing down is easier on the truck and the wallet.

@Me78569 you still finding the will power to keep your 4th gen stock? Gotta be tough. 

it's got more than enough power in stock form.  

1 minute ago, Me78569 said:

it's got more than enough power in stock form.  

I’ve got pretty much the exact same truck. Only thing I didn’t really like stock was the fuel economy. Abysmal. 

Towing heavy you should be above 1800RPM.

 

Compounds give you more air/boost at lower RPM, but it still is a lot of torque and the torque is hard on components that are not spinning fast.

 

downshifting is probably your best bet.  going to a bigger turbo shifts your problems to have more EGT at lower RPM  and lower egt at higher RPM.

 

100HP injectors and 57/65/12 GXE or an HE351cw would work with less drawback.   

 

Your post did not say it, but do you have an adrenaline already?  Smaller tires or 4.10 gears would also help.

Add twins and 4.10 gears. It’s just money!

1 hour ago, dieselautopower said:

Smaller tires or 4.10 gears would also help.

 

Remember 245/75 R16 tires or 245/70 R17 tires would give you a final ratio of 3.69 roughly to the ground. Those 285/70 R17 push your final ratio 3.44 this creates more EGT's. Optimal final ratio is 3.55 to 3.73. The combo of the 245/75 R16 and the 3.55 gears makes it a perfect towing machine being the final ratio puts you right at 2,000 RPM at 66 MPH. This is optimal for towing you should be up close to 2,000 RPM for towing on the highway. Even running empty at 80 MPH is just short of 2,500 RPM. 

6 hours ago, dieselautopower said:

Towing heavy you should be above 1800RPM.

 

Compounds give you more air/boost at lower RPM, but it still is a lot of torque and the torque is hard on components that are not spinning fast.

 

downshifting is probably your best bet.  going to a bigger turbo shifts your problems to have more EGT at lower RPM  and lower egt at higher RPM.

 

100HP injectors and 57/65/12 GXE or an HE351cw would work with less drawback.   

 

Your post did not say it, but do you have an adrenaline already?  Smaller tires or 4.10 gears would also help.

No, the Adrenaline and injectors I’ll be ordering this week,  fixing another issue at the moment. Currently on stock injectors and the Smarty.

12 hours ago, Andyba20 said:

I’d like to maintain speed (65 mph) on sub 1 mile 6%-8% grades towing 9K without having to downshift.

 

11 hours ago, Andyba20 said:

But I’m talking about short up and downs where I need a little more top end to crest the next hill without losing momentum and downshifting. So like 30 seconds of pushing it and then coast back down.

 

10 hours ago, Andyba20 said:

just hoping I could cure it with tuning and maximizing the stock turbo since I’ve never even pushed it past 20 psi.

 

2 hours ago, Andyba20 said:

Currently on stock injectors and the Smarty

 

I see two issues that could help you/

 

1.  Go down on tire size - 245's would probably put the engine at about 1700 rpm at 65 mph.

 

2.  You mentioned, " I’ve never even pushed it past 20 psi.".  That sounds like a stock waste gate setting to me.  If the wastegate isn't clamped or a boost elbow is not installed, then the Smarty S03 can't do much for you.  You should be able to attain 28-30 psi boost above 1700 rpm.  So, just as long as your transmission is up to the job and since you already have a Smarty S03, I don't see why you can't do what you are trying to do.  The engine will pull hard at 1700 rpm and still keep EGT's in check with the right tune.

 

I have been running the Smarty S03 for over 110,000 miles, with the first 50,000 miles on OEM injectors with 250,000 miles on them - changed them out at 303,000 miles.  If I were in your shoes, I would get the wastegate operating properly and use the Smarty with a proper tune.  Since you already have the Smarty, it would be easy to experiment to see if it would work for you.

 

- John

20 hours ago, Andyba20 said:

With good tuning and 7x.010’s can I get better top end for towing grades? To be more specific, I’d like to maintain speed (65 mph) on sub 1 mile 6%-8% grades towing 9K without having to downshift. Subjective I know, but can this be accomplished through tuning, injectors, and my hx35w, or do I need more turbo? 

 

I'll chime in on this, with the following assumptions:

-9k is trailer and load only

 

I have one of these hills on a route close to my home, its 7% and about 1/4-1/2 mile per the odometer. It's also 40mph speed limit even though most are going 45-50. In all honesty, I don't think its good on anything to lug the motor like that for that long. It's easier on the vehicle to drop down to 3rd (auto) and let the engine spin. My truck I can get away with it because I have 4.10s and 285/70r17s. At 50mph in OD I'm spinning 18-1900 rpm. But towing I would probably back it down to 40 and drop down a gear.   

 

I think people forget that our Cummins is technically an industrial engine. One of its uses is/was stationary generators. Those engines once started go right to full throttle. Yeah, it sounds scary and its gonna be loud, but the engines are designed around it. Cummins engines can take sustained 1200°F egt's if I remember correctly. Might have to worry about melting stuff around the engine though.. 

 

Maintaining speed with the load is I think not likely either because of the TV(?) cable.. Full manual valve body might be able to do it but that's relearning the truck and usually a race only option.. 

 

I guess I should also ask why? Why do you want to maintain OD while climbing the grades? --- I reread everything, I think you did answer this... You are driving through more rolling hills than mountain grades.. Parallels the route I was talking about earlier. I don't know, might be worth dropping speed and just locking out OD from the get go.. This coming from a New Englander, you are going too slow if you are doing 75 in a 65 lol.

 

"Larger" turbo might help, but you have to make the decision on how you want to drive. And the wastegate issue being fixed will probably also help.

Like myself my normal cruise 65 MPH is ~2,000 RPM. If you cruising below 1,800 your not helping efficiency. This is one of the key features that gets me 425 miles to a half tank. Smaller tires that are lighter, also the final ratio very close 3.73 ratio to the ground. Hard to catch me with a high mark of 28.04 MPG set this last summer. 

 

Low RPM's is a bad thing. Causes lugging and high EGT's because you not working in the power band.

Repeating what Tractorman said. You’re leaving a lot  of Hp and even more torque on the table with only 20psi of boost. You’re HX35 should map out at about 32 lbs of boost. If you don’t have one yet you need a boost elbow or a spring and turn buckle to hold the wastegate closed till 30-32 lbs. once you get the injectors and Quad along with it your truck will tow much better. With a good tune of course. Also at 9k I’d be towing in drive as well. Lower rpm’s doesn’t equate to better efficiency with the Cummins. I just switched back from 285’s back down to 265’s. Haven’t towed with them yet but I will this Friday. Looking forward to seeing the difference. 

1 hour ago, Threadzy said:

Repeating what Tractorman said. You’re leaving a lot  of Hp and even more torque on the table with only 20psi of boost. You’re HX35 should map out at about 32 lbs of boost. If you don’t have one yet you need a boost elbow or a spring and turn buckle to hold the wastegate closed till 30-32 lbs.

 

Roughly speaking for every 1 PSI of boost will give roughly ~10 HP of power so HX35W could be ran at 35 PSI of boost easy slightly out of the map but still workable. Like my HX35/40 Hybrid is the same exhaust housing as stock with the same turbine. But the compressor is HX40 wheel. Stronger turbo than the HX40. 35 PSI is roughly ~350 HP. Otherr factors in volved again tires size, gear ratio, final ratio of the transmission, final ratio to the ground with tires, injector size, pop pressure of the injector, tuner, etc.