Thought on turbos?

mbmast

New member
Well you can certainly fit an LS 5.3L V8 in there. And it's an aluminum engine, so it weighs nearly the same as the stock engine.

Aftermarket turbos can be very expensive when done correctly. If you plan on running around 4 or 5 pounds of boost, you can pretty much bolt on a turbo. Any more boost than that and you really should build the engine for the turbo. This would entail forged aluminum pistons (to survive any unwanted knocking that might occur), increased volume oil pump. The turbo is lubricated and cooled by engine oil that flows fairly freely past the impeller shaft. This can significantly drop your oil pressure, hence the need to install a high volume pump. Overboost must be prevented, so you'll need an inline limiter (not the best) or a waste gate (the best). Then there's the nightmare of connecting two exhaust manifolds together. Do they go under the engine (but where?) or over the engine (but where)? A cleaner install would be bi-turbo, one for each head. That eliminates the cross over pipe and, because each of the two turbos is smaller than a single turbo, you cut any turbo lag by a factor of around 4 (the angular momentum of the impeller/compressor is half that of a single larger turbo and the amount of time required to get to speed is a function of the square of the rotating assembly's moment of inertia). You could also install sodium filled valved to help transfer heat out of the engine cylinder. And what about the bottom end of the engine. The 3.8s are pretty weak.

A more practical solution is a supercharger. The install is easier but you should still do the other things you'd do to build a turbo engine. The problem with either of these solutions is that there are guys out there that, after the installation, are still not satisfied with the power. I have a 4 door set up for expedition, so it's heavy. 2nd battery, on board air, air tank, 35s, roof rack, heavy tool box I drag around, refrigerator, crap on the roof rack. It adds up pretty fast.

I put in the LS 5.3L V8 with the 6 speed trans. You have other options as well: 6.2L with 8 speed trans for example. There's no extra stuff in the engine compartment. The V8 fits almost exactly like the V6 it replaces, so even with the V8 it
's not all tight and cramped in there. I had MoTech in Las Vegas do the swap (see lswrangler.com).
 

NevadaZielmeister

Caught the Bug
I'm no expert, but don't you get the most out of a turbocharger, when the engine is wound up at high rpm? Would that really benefit a Jeep?

A gear job can really help put power on the ground.

But regarding turbos, I don't feel they would be worth the effort or cost on a jeep unless you really know what you're doing. I've messed with a few on other vehicles and it is tricky to dial in unless you get a good kit or know someone who can really flash the ECM accurately. As far as low end power, if you are going to run a turbo, a helpful option is a t3/t4 hybrid. It uses a t3 smaller turbine housing whereas the compressor housing is a larger t4. You can get better spool up at low rpms while forcing a higher of volume of air in the engine at the lower rpms as well. I still think on a jeep application, gears are the way to go.

So here we go again on the gearing discussion, but let's look at this a different way. And I will just use my limited experience with Jeeps and my experience after a significant build. You can check out what I did on the signature line below. Long story short, left my Jeep weighing over 5,000 pounds, maybe even closer to 6,000 pounds. I re-geared it to 5.38 and this was mostly for the off-road performance. I have to say that no amount of gearing would change my ability to get up long uphill sections at freeway speeds. The engine simply does not have the horsepower with the added weight.

The question is, with added turbo boost (horsepower) at moderate to higher RPM's would increase my Jeep's ability to get up those long drags, right? The reason I ask is not hypothetical, but every time I drive RubySky to and from home, as there is a large hill along Highway 395 that I must traverse. I sometimes dread heading up that thing on windy days because the most I can do is 50 mph. Any thoughts would be appreciated.
 

QuicksilverJK

Caught the Bug
Yes more horsepower will net you a higher road speed in any given gear setup until you are gear bound. The gearing is what allows you to climb said hill or obstacle with less effort. This is torque application.
A semi with 375 HP can carry a load of 160k+ pounds. Do you think a 375 HP Subaru can? The difference is in the gearing.
I honestly think because you hadn't driven your jeep in any configuration but stock and current that the concept is getting lost on you. The hill that you hate climbing now, I guarantee you wouldn't be climbing at 40mph with your stock gears and everything else the same.


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NevadaZielmeister

Caught the Bug
Yes more horsepower will net you a higher road speed in any given gear setup until you are gear bound. The gearing is what allows you to climb said hill or obstacle with less effort. This is torque application.
A semi with 375 HP can carry a load of 160k+ pounds. Do you think a 375 HP Subaru can? The difference is in the gearing.
I honestly think because you hadn't driven your jeep in any configuration but stock and current that the concept is getting lost on you. The hill that you hate climbing now, I guarantee you wouldn't be climbing at 40mph with your stock gears and everything else the same.

Why do I feel like I am being followed? :bleh:

You are right about the gearing change back to stock with the extra weight, but the gearing itself does not get me up the hill any faster. It seems more horsepower would solve my problem given the gearing is already set, right?
 

notnalc68

That dude from Mississippi
So here we go again on the gearing discussion, but let's look at this a different way. And I will just use my limited experience with Jeeps and my experience after a significant build. You can check out what I did on the signature line below. Long story short, left my Jeep weighing over 5,000 pounds, maybe even closer to 6,000 pounds. I re-geared it to 5.38 and this was mostly for the off-road performance. I have to say that no amount of gearing would change my ability to get up long uphill sections at freeway speeds. The engine simply does not have the horsepower with the added weight.

The question is, with added turbo boost (horsepower) at moderate to higher RPM's would increase my Jeep's ability to get up those long drags, right? The reason I ask is not hypothetical, but every time I drive RubySky to and from home, as there is a large hill along Highway 395 that I must traverse. I sometimes dread heading up that thing on windy days because the most I can do is 50 mph. Any thoughts would be appreciated.

This hill you keep mentioning, must be huge. Seems like you need a 6.2L Motech swap.


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Sahara_Maverick

New member
This is a great thread since I have been seriously considering an engine swap. My 07 still has the original 3.8L and I've been thinking about this upgrade.

One question I have is about the overall powertrain. If we are increasing power and torque the stuff between the engine and the tires will feel it.

What else between the engine and wheels do we change or upgrade?
Transmission, transfer case, diferentials, axles?

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Strodinator

Caught the Bug
This is a great thread since I have been seriously considering an engine swap. My 07 still has the original 3.8L and I've been thinking about this upgrade.

One question I have is about the overall powertrain. If we are increasing power and torque the stuff between the engine and the tires will feel it.

What else between the engine and wheels do we change or upgrade?
Transmission, transfer case, diferentials, axles?

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Take a look at my build thread and that can tell you. Mine is into a TJ but it's the same idea. For the most part an LS v8 around 350 horse is not too much for the transfer case and differentials if you have the Rubicon I.e. Dana 44's. Transmission will take more research depending on your hp/ torque mods. Pcm reflush and wire splicing.

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QuicksilverJK

Caught the Bug
This is a great thread since I have been seriously considering an engine swap. My 07 still has the original 3.8L and I've been thinking about this upgrade.

One question I have is about the overall powertrain. If we are increasing power and torque the stuff between the engine and the tires will feel it.

What else between the engine and wheels do we change or upgrade?
Transmission, transfer case, diferentials, axles?

Sent from my SAMSUNG-SM-G891A using WAYALIFE mobile app

My understanding is when MoTech does the LS swap they ditch the 4:1 transfer case in favor of the 2.72:1 because of the additional strain. This is why motech is a great option if your looking to get ahold of a Rubi case.


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fiend

Caught the Bug
My understanding is when MoTech does the LS swap they ditch the 4:1 transfer case in favor of the 2.72:1 because of the additional strain. This is why motech is a great option if your looking to get ahold of a Rubi case.


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I don’t think it’s due to additional strain but rather some kind of output shaft compatibility issue.
 

Bierpower

Hooked
I don’t think it’s due to additional strain but rather some kind of output shaft compatibility issue.
I've had a talk with motech on this. The 2012 and up t-case has a male input shaft so it won't work but the 2011 and prior will.
They ditch it, because of how low the first gear is on the GM transmission.


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Motech recommends the 2.7:1 case because the GM transmission has a 4:1 first gear maintaining the factory Rubicon type gearing overall.

Jeep-3:1 first gear and 4:1 case
GM-4:1 first gear and 3:1 case

Robbie also said that if you were to swap the input shaft on a Rubicon case to fit behind a 6L80 that it would make it weaker because of the design of the planetary on the Rubicon case. It's been a couple of weeks since we talked so I'm a little fuzzy on all of the details.

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QuicksilverJK

Caught the Bug
I've had a talk with motech on this. The 2012 and up t-case has a male input shaft so it won't work but the 2011 and prior will.

Motech recommends the 2.7:1 case because the GM transmission has a 4:1 first gear maintaining the factory Rubicon type gearing overall.

Jeep-3:1 first gear and 4:1 case
GM-4:1 first gear and 3:1 case

Robbie also said that if you were to swap the input shaft on a Rubicon case to fit behind a 6L80 that it would make it weaker because of the design of the planetary on the Rubicon case. It's been a couple of weeks since we talked so I'm a little fuzzy on all of the details.

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That makes a lot of sense. Thanks for the info. I was going off of what I thought I read a year or so ago when trying to find a 4:1 for mine.


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