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Discussion Starter · #1 ·
A few years back I swapped a P-Pumped 4BT into my 2007 Wrangler Unlimited. I mated the engine to a NV4500 that I rebuilt. The truck is lifted about 2.5" and it has 315/70-17's on it. The stock Dana 44 rear end has a 3.23 gear ratio (which I found desirable for this swap). The NV4500 is 1:1 in 4th and 0.73:1 in 5th. I'm very conscious about keeping this vehicle in good shape I won't drive it in Ohio winters so I've only tracked about 14,000 miles on the swap now. I've been averaging ~22MPG for that period with the best mileage being around 23.8MPG. My speedo is slightly off as my programmer only allows round numbers for tire sizes (it reads a 2-3 mph slow @50 I think). I don't do a lot of highway miles, mostly city and country roads. With this setup, I have plenty of overdrive and I find myself always wanting to drop it in 5th gear while cruising on flat roads around 50MPH. In 5th Gear I'm only spinning around 1,150RPM where I'd be turning 1,550RPM in 4th. My thought has always been the lower the revs the better the mileage. I question this though as guys have always said these engines (at least the 5.9) is happiest cruising at 1,800RPM on the highway.

Can you please share your experience on this topic?
Would I have been better off with a higher gear ratio to keep the revs up more?
Should I try to hold cruising in lower gears since I have so much overdrive?

I've been meaning to post about this and a couple other bugs i've found with the swap for quite a while now. I thought I'd start with this...
 

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You sure don't want to run it at 1150 RPM. There you would have very little HP or torque. That would be lugging the engine badly. 1550 is much much better. The ideal number is right around 1700-1800 RPM. That is where the torque hits its peak. Your 22-23 MPG number isn't terrible and probably about average. I always tell people 25 MPG would be considered good. Getting above that takes a bit of experimenting. Have you made any changes to the engine from stock? Hard to understand, but some performance mods can improve fuel mileage. Your big wide tires are one thing that hurts mileage.
 

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How rough is that thing at 1150rpm?
Running unloaded at low speed at that rpm is no big deal. But a big 4 cyl will get rough as hell under load at that rpm.
 

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Discussion Starter · #4 ·
The engine is a CPL1839 pulled from a somewhat low mileage Freightliner MT35. I'm using the stock HX30 turbo and rebuilt stock injectors (as everyone said they would provide more than enough fuel). I installed 60# valve springs and the 4k gov spring kit which I'm not really convinced makes much difference because the engine doesn't seem real happy over ~2,800rpm anyways. I bought the Blue Point timing tool and socket to properly set the timing to whatever was suggested on here (have to check but I believe ~15-16deg adv). I turned the fuel up at the pump but it's nothing ridiculous. I'd like to think I'm making quite a bit over the stock 130hp but I really don't know for sure. Acceleration is nothing to write home about and I'd like to improve that some. Under load and climbing it will build ~23lb of boost max at ~11-1,200° F. I was able to squeeze a charge air cooler in front of the stock jeep radiator which was a goal of mine before the build. Considered a Super HX30 upgrade but I haven't pulled the plug on that yet. I've also considered ceramic coating the manifold and turbine housing due to bad heat soak to the cab but I think that's getting too far off topic for this thread.

As long as it's a flat road it doesn't seem unhappy or rough at 1150rpm. As mentioned, if there's a grade or something a downshift is in order but I'm seldom running over 1,700rpm regardless. I am open for suggestions and any criticism you guys can offer. Thanks for any feedback.
 

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It sounds like you've done most of the right performance mods. In theory you should have over 200 HP but there might be a missing element. How did you turn up the fuel? Did you change the torque plate in the injection pump? The #10 is the one most P pump owners seem to favor. Have you adjusted the boost control on the turbo? That engine should hit somewhere in the 30-33 PSI range before it runs out of steam. Do you have a good air filter capacity. More boost requires more incoming air. Another element in the puzzle can be the overflow valve on the injection pump. If it's spring gets weak it will vent most of the fuel back to the tank leaving less for the injectors. Easy part to change and not very expensive. Have you double checked to be sure your timing has stayed where you set it. If the pump gear had slipped you could have retarded timing. At 1150 RPM don't expect it to be peppy. The turbo has just begun to build boost at that point. You probably only have maybe 50 HP at that point which isn't going to be very peppy in your vehicle. However torque at that engine speed is up near 200 lb ft which is how you're able to run at that low RPM. You mention potential ceramic coating. That is a good thing if you can afford it. Coating the manifold and turbine housing helps with boost. Just be aware there are all different grades of those coatings. Some are only cosmetic and have ratings around 1000 deg F. Better ones go in the 2000-3000 deg range. If you have deep pockets, the make them in the 6000 deg range. Have not idea how expensive that one is.
 

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My 4bt was in an 89 ranger for 8 years and it was similar to yours. Dana 44 axles, nv4500 and 35s.
The difference is I had 3.73s in the axles. Cruising at 1800 I would be at 62 mph. As far as power is concerned I think you should swap to 3.73s. I think it makes the 4bt much happier.
Can u lift off in 2nd?
My truck scaled in at 5300 lbs.
Also it got 25 mpg on freeway.
With less lift and 33s I could get 30 mpg.
 

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Discussion Starter · #7 · (Edited)
It sounds like you've done most of the right performance mods. In theory you should have over 200 HP but there might be a missing element. How did you turn up the fuel? Did you change the torque plate in the injection pump? The #10 is the one most P pump owners seem to favor. Have you adjusted the boost control on the turbo? That engine should hit somewhere in the 30-33 PSI range before it runs out of steam. Do you have a good air filter capacity. More boost requires more incoming air. Another element in the puzzle can be the overflow valve on the injection pump. If it's spring gets weak it will vent most of the fuel back to the tank leaving less for the injectors. Easy part to change and not very expensive. Have you double checked to be sure your timing has stayed where you set it. If the pump gear had slipped you could have retarded timing. At 1150 RPM don't expect it to be peppy. The turbo has just begun to build boost at that point. You probably only have maybe 50 HP at that point which isn't going to be very peppy in your vehicle. However torque at that engine speed is up near 200 lb ft which is how you're able to run at that low RPM. You mention potential ceramic coating. That is a good thing if you can afford it. Coating the manifold and turbine housing helps with boost. Just be aware there are all different grades of those coatings. Some are only cosmetic and have ratings around 1000 deg F. Better ones go in the 2000-3000 deg range. If you have deep pockets, the make them in the 6000 deg range. Have not idea how expensive that one is.
Char, At the time of build I recall taking the fuel plate and shifting it all the way forward. I also turned up the 'smoke screw' until I was comfortable with the fueling/smoke. I was going to machine an old stock plate with a new profile but I honestly must have shifted focus and forgot about it. I don't recall having adjusted the boost control much so I started with that over last weekend hence the long reply time. I removed the waste gate actuator, tested it and shortened it two turns. I wanted to shorten it 2 ½ turns but I couldn’t reinstall it. After reinstalling, and test driving it I couldn’t get more than 14 lbs of boost. I clamped the actuator line closed again and I could still get ~23psi max (forgot to mention I was running with it clamped before any of this).

Next, I installed an aftermarket overflow valve. I didn’t get one before because I was getting around 28 lbs of pressure. After installing the new overflow, my fuel pressure looks like it went just over 30psi. It’s hard to tell because the gauge I put inline after the cam driven stock fuel pump is only 0-30 psi. It might be more than 30psi but it’s pegging??? Either way, I assume I have ample fuel pressure because after another test drive there was essentially no change.

On to the next change per your suggestions I installed the #10 fuel plate that showed up with the ofv. I left it shifted 2/3 of the way forward, not all the way like the stock plate. This fuel plate made a significant change. At moderate to heavy throttle there is now thick black smoke. However, without the actuator line clamped off it still wouldn’t build more than ~20psi. I’ve been driving it with the line clamped now. I can make build about 29lbs of boost max now. I have to be very careful now because the EGT’s will soar to 1,300f in the bling of an eye. If I’m easy on the throttle, the smoke is very controllable but I need to turn back the smoke screw. The responsiveness of the engine is now quite an improvement since it’s now building boost sooner. Cruising 50mph now in 5th shows a steady 3-4lbs of boost and it seems a lot happier.

Regarding the timing, I haven’t been able to check that again yet. I was pretty sure it didn’t slip but I’ll look into that soon as well. Can you comment on the boost and the reason I’m having to clamp the line to the actuator closed to build a decent amount? There’s Tee in the line coming out of the manifold, one side goes to the AFC and the other to the wastegate actuator. Thanks again for your help…
 

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Discussion Starter · #8 ·
My 4bt was in an 89 ranger for 8 years and it was similar to yours. Dana 44 axles, nv4500 and 35s.
The difference is I had 3.73s in the axles. Cruising at 1800 I would be at 62 mph. As far as power is concerned I think you should swap to 3.73s. I think it makes the 4bt much happier.
Can u lift off in 2nd?
My truck scaled in at 5300 lbs.
Also it got 25 mpg on freeway.
With less lift and 33s I could get 30 mpg.
I pretty much only start off in second gear unless I'm towing or on a steep grade. Now that the engine is getting a little more fuel/boost, I'm actually even happier with the gearing than I was before. It's never been better effortlessly cruising down the highway 75mph at 1,750rpm, even with the oversized tires humming away. You have me curious about the weight now, i've never had the truck on a scale before but I'll have to check it soon. I'm surprised to hear your Ranger is that heavy. I appreciate your input...
 

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I pretty much only start off in second gear unless I'm towing or on a steep grade. Now that the engine is getting a little more fuel/boost, I'm actually even happier with the gearing than I was before. It's never been better effortlessly cruising down the highway 75mph at 1,750rpm, even with the oversized tires humming away. You have me curious about the weight now, i've never had the truck on a scale before but I'll have to check it soon. I'm surprised to hear your Ranger is that heavy. I appreciate your input...
No problem!
A bit of tuning takes these engines from a slug to a real performer!
It doesn't take too long to get the weight up there. All those 1 ton drive train parts and bigger axles, more cross members, bigger bumpers, rock sliders...ect ect. lol. She moved pretty good still tho, no complaints.
I've dropped my 4bt in a ford expedition as the family has expanded and i'm pretty sure that truck is over 6k, but i've yet to scale it.
 

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Your problem is lack of boost from the turbo. The injection pump is giving the engine more fuel but it is only creating smoke and heat not power. The turbo should be producing boost in the 30 PSI range upon demand. Did you adjust the actuator in the correct direction? You want it to keep the wastegate closed until around 30-33 PSI. Now, don't expect that kind of boost just cruising down the highway. Boost increases upon load on the engine. Under easy load you may only see around 8 PSI but the fueling should be lower under that condition. Starting to sound like there is a problem with the AFC unit on the injection pump. That controls fuel to boost level and you should only get just a bit of smoke until boost comes on.
 
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