5.9 swap questions

[GoldenGorilla]

I used the 2.5 exhaust.

If you go through Engine Masters content you can see what difference 2.5 vs 3.0" exhaust delivers. May or may not change your mind.

For what i do, the 5.9 is very impressive a d more than I need.MPG is not the best as I get about 11 MPG.

That seems a bit on the low side unless you're heavy with the right foot. Could a gear change put you a more efficient rpm? This is from a 2001 5.9, but I'd imagine it's pretty similar across the years. If you can get your cruising rpm above 2000, the you've got alot more power available on throttle tip in which should keep you in more efficient closed loop running.

 

[Wildman]

If you go through Engine Masters content you can see what difference 2.5 vs 3.0" exhaust delivers. May or may not change your mind.

I'd forgotten about that episode.... And yes I think it does matter.

That seems a bit on the low side unless you're heavy with the right foot. Could a gear change put you a more efficient rpm?

The Magnum engines were never known for their GREAT fuel mileage but it does seem a bit low. Some folks who'd done the V-8 swap on Jeep Forum with the 5.9 claimed 15-17 MPG... But I don't remember what tire size a gear ratio they were running.

He'll be getting some new parts that might help some come next spring. And while it's pricey I do think a tune for someone like FRP or Hemifever would also help.

And YES this is one of the arguments for the LS engines. As I've said before my only experience with one was in my Chevy 3/4 ton with a 6.0 that got shit fuel mileage..

 

[GoldenGorilla]

I'd forgotten about that episode.... And yes I think it does matter.

It was based around a 600hp big block motor and WOT testing at higher RPM. But it was also a dual exhaust. Yes, it gave up 15hp or 2.4% at peak and pretty much the same everywhere under the curve (from 3000RPM and up).

All of these tests are performed at WOT focused on the RPM range from 3000 to the point where horsepower rolls over. Great for some specific use cases, but not necessarily applicable to all and you can sometimes see that at lower RPMs the curve is moving in a different direction. There is just as much variance between different muffler types and there are other episode comparing cheap versions of straight through (Magnaflow) vs turbo (Dynomax) vs chambered/baffled (Flowmaster).

 

[Wildman]

It was based around a 600hp big block motor and WOT testing at higher RPM. But it was also a dual exhaust. Yes, it gave up 15hp or 2.4% at peak and pretty much the same everywhere under the curve (from 3000RPM and up).

All of these tests are performed at WOT focused on the RPM range from 3000 to the point where horsepower rolls over. Great for some specific use cases, but not necessarily applicable to all and you can sometimes see that at lower RPMs the curve is moving in a different direction. There is just as much variance between different muffler types and there are other episode comparing cheap versions of straight through (Magnaflow) vs turbo (Dynomax) vs chambered/baffled (Flowmaster).

My opinion about exhaust size comes more from the Magnum swap thread over on Jeep Forum and where some of the guys reused the stock TJ exhaust only to up the size a year or two after and most were shocked but pleasantly surprised with the added performance they got.

https://www.jeepforum.com/threads/wrangler-magnum-v8-discussion.1365878/#replies

And this build thread he swapped to a larger exhaust too.

https://www.jeepforum.com/threads/m...ps-my-stroker-wiped-its-cam-bearings.1516649/

When I was building the stroker for my TJ I was advised that I should be up around 3.5" exhaust I think it was based on the CI of the engine. But I couldn't figure out how to squeeze anything larger than the 3" exhaust pipe I had.

I don't have any dyno numbers to support any of this just the butt dyno of a few people.

 

[GoldenGorilla]

I would agree with my experience with a 2.5" system and the 4.0L with mild modification. I went from a 2.5" Flowmaster Delta 60 with 2.5 mandrel bent final section and then switched to a 2.25 Walker Quietflow SS welded to that 2.5 mandrel bent pipe. I felt like this gave up 5-10hp in the mid-high RPM range and the Flowmaster is probably not as good on peak power as a straight-through style like a Magnaflow. For me, the quieter interior was worth the trade-off but I maybe should have tried the 2.5" Dynomax super-turbo I've got sitting in the attic.

 

[Paparock1]

If you go through Engine Masters content you can see what difference 2.5 vs 3.0" exhaust delivers. May or may not change your mind.

That seems a bit on the low side unless you're heavy with the right foot. Could a gear change put you a more efficient rpm? This is from a 2001 5.9, but I'd imagine it's pretty similar across the years. If you can get your cruising rpm above 2000, the you've got alot more power available on throttle tip in which should keep you in more efficient closed loop running.

View attachment 660843

I am ignorant to reading and understanding these graphs. I always thought that getting the rpms lower at cruise was better efficiency? I have 4.56 gears and 35 inch tires. my transmission is the 46re that I rebuilt. I have a 242 transfer case but it is the same ration as the 231. I will check my rpms tonight but I do drive between 65 to 70 normally. I must have a vacuum leak as my heater shuts off when I give it more gas. not sure how to track that one down.

Thanks for the information though

 

[Paparock1]

Late to the party, but a 1997 Magnum V6 Dakota fan clutch is the shortest one available (see pics from my thread). The trade off with that clutch is that it'll make accessing the front of the engine a pain as it pulls the fan extremely close to the engine.

I'm running a cheap eBay stock replacement and its adequate but not amazing. Mine still gets a tick warm on interstate driving but I'm not convinced the radiator is entirely the culprit there. I'd recommend looking into https://bricethomasradiator.com/ and getting an LS swap radiator to get both inlet and outlet on the passenger side. My lower radiator hose could be much shorter if the radiator outlet was on the opposite site.

I bought a new radiator here recently. I will post up where I got it when I get home tonight.

 

[Wildman]

I am ignorant to reading and understanding these graphs. I always thought that getting the rpms lower at cruise was better efficiency? I have 4.56 gears and 35 inch tires. my transmission is the 46re that I rebuilt. I have a 242 transfer case but it is the same ration as the 231. I will check my rpms tonight but I do drive between 65 to 70 normally. I must have a vacuum leak as my heater shuts off when I give it more gas. not sure how to track that one down.

Thanks for the information though

This is with me guessing your tires are 34.25" tall.... IMO you'd be better off with 4.88 or even 5.13 gears but I can't say that this would help your MPG any. This is about where my 98 Ram with a 5.2 cruised at so for factory spec's you're pretty close.

Here's what I know about the Ram PCM... There was a what was coined as the DEATH Flash done in the late 90's due to the Magnum engines pinging since they don't have a knock sensor. And due to this they retarded the timing and cut leaned out the FI...This is why I think it's worth it to even just get a canned tune from either FRP or Hemifever.
Will this for sure help your fuel mileage? Don't know but I do think it'll help your engine run tons better. If you can find a local shop to tune your engine you can do it that way also...

Obviously things like headers & roller rockers & larger throttle bodies & intake manifolds & better flowing heads & better flowing exhaust will all help your engine run better plus can help performance.

 

[Paparock1]

I looked up a way to check to see if my PCM had the death flash, I cant remember right now how to do it but I determined that mine does not have it.

 

[Wildman]

I looked up a way to check to see if my PCM had the death flash, I cant remember right now how to do it but I determined that mine does not have it.

I used to have some of the sites that had all that info too. Even without the death flash just like our 4.0's PSM the tuns on them is very conservative. It's why getting a tune either remotely or locally IMO is a good thing.
You can of course choose to get HPTune and do the tuning yourself... I don't want to risk grenading my engine.

 

[Wildman]

Just like here where he found what gained in the 4.0 a lot transfers to the Magnum engines too.

https://wranglertjforum.com/threads/dyno-testing-bolt-ons-on-the-4-0.79004/

 

[GoldenGorilla]

I am ignorant to reading and understanding these graphs. I always thought that getting the rpms lower at cruise was better efficiency? I have 4.56 gears and 35 inch tires. my transmission is the 46re that I rebuilt.

Lower RPMs are more efficient with a very aerodynamic car where you are putting very little load on just pushing it through the air. The TJ is pretty much the opposite of that, so it becomes a bit more where you have better power production efficiency. As much as people say torque matters - it doesn't directly. It affects the hp curve, but it's the horsepower that actually gets you down the road.

I look at those graphs as where can I get sufficient power potential so that I can stay off wide open throttle at inefficient rpms. I would change up the grimm jeeper gear ratio calculator for the speeds probably 60, 75 and 85 or 50, 60 and 75mph. At 2000rpm it is cross 100hp and at 2500 it is crossing 150hp. This is enough to push the jeep through the air. But in OD you are just getting into the 2000s at 70mph. Going from 4.56 to 4.88 would increase the rpm at same speed by ~200rpm adding about 25hp potential through that part of the curve. Your 3rd gear would remain in a workable window as well with 70mph around 3500 rpm.

I ran my Rubicon with "33s" and 4.10 gears for 20 years before finally moving to 4.56 gears. I did a few other power mods at the same time, but I believe getting the RPMs into a more efficient band helped the fuel economy most in getting me from 13 no matter the speed to 15.5mpg consistently at 65mph. It falls at 75mph due to the poor aero efficiency. I did not go to 4.88s because I wanted to keep my cruising RPMs at 75mph under 3000 in 5th gear with the NV3550.

 

[Wildman]

Here's with 4.88 gears... Only going to change you 200 RPM's

5.13 gears not even 300 RPM's

IMO 5.38's would be the best gear ratio putting your RPM's @ 2550 but you'd need at least Dana 44's F&R to do this.

Can I 100% say that running at that RPM would be the BEST for fuel mileage? No I can't say that. About the only thing you could try would be to put it into 3rd and drive around for 2 tanks of fuel & see if running around at 3,000 RPM's helped fuel mileage any.

 

[Paparock1]

well here is what my RPMS are at a set cruise MPH
40 MPH 1200
55 MPH 1500
60 MPH 1900
65 MPH 2000
70 MPH 2200
75 MPH 2500
of coarse this is taken from the stock gauge cluster. I do have a wifi code reader that I will install to get actual RPMs

 

[Paparock1]

I am going to post my actual OBD2 recordings in my own build thread. if you toggle my signature you will find the link to my build.

 

[srimes]

You'll want to go to 3" after the Y-pipe. Your 5.9 will thank you for it..

I've got a spare 5.9 block and a stroker kit for the 5.9 making it a 6.7 (408) also.

 

[Wildman]

View attachment 661193

It could be yours.... Hell I'll meet you in Portland with it...