Turbo and Supercharged TJs

I love forced air induction and have done several custom projects with them. However, on a Jeep, I think they're pointless...just my opinion. You can see better and more practical gains with a re-gear. Not to mention, gears are much cheaper. TC/SC can be complicated getting the fine-tuning done and they aren't cheap to set up. I had my very first experience being around a supercharged Jeep on a trail this year, and it was one of the most annoying things I've ever heard, it was a constant whine every time he accelerated. That's a badass sound on a 10 second race track, but annoying as fuck on a trail for half a day.
 
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If you like off road, torque is your friend. However, mud and dust are real unfriendly to turbo and superchargers. And the torque you gain with a turbo is quite sudden, and in higher rpms. Yes, you can compensate, etc. The point is, at least from my perspective, rock crawling and turbos would be bad for the power spikes, mudding would be good due to the high revs, but bad for the turbo or a supercharger due to material intake. Supercharger may be better or smoother power application, but my thought is at the low end, where it actually has value off road, the gain is offset by the power drain of the supercharger itself.
Just my opinions of course, not physically tested any of this.

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I strongly disagree with wj, the drivability of a turbo tj is waaaay better with a well setup basic system running lower psi. As far as tuning, ya that can Be intimidating but with a wideband o2 sensor and a self learning fuel management it's pretty straight forward. I can drive highway all day long like it's a stock vehicle with full power band with 3.73 gears and 37" tires in his. Highway rpm keeps it a little in boost and gets almost double the mpg I do on 33s, plus he has way more power. It's not a replacement for gearing, it's just more power- sometimes that means you won't require a smaller gear change though. Turbos are much quieter than super chargers and you don't really hear it til you get on it. It does require premium gas though. But If you're not familiar with working on an engine or are afraid of hurting something I'd stay away from forced induction in general. As far as "contaminates" getting sucked in, are you guys not running air filters?? And if you use the right size turbo it's not "sudden" or only in high rpms, and besides that you still have the stock baseline of a 4.0l which isn't a lightweight to begin with. The only reason I'm not running the same on mine is I'm pretty sure the jeep may rust apart in the next few years and don't wanna spend more money on it.
 
Snboarder113 said:
I strongly disagree with wj, the drivability of a turbo tj is waaaay better with a well setup basic system running lower psi. As far as tuning, ya that can Be intimidating but with a wideband o2 sensor and a self learning fuel management it's pretty straight forward. I can drive highway all day long like it's a stock vehicle with full power band with 3.73 gears and 37" tires in his. Highway rpm keeps it a little in boost and gets almost double the mpg I do on 33s, plus he has way more power. It's not a replacement for gearing, it's just more power- sometimes that means you won't require a smaller gear change though. Turbos are much quieter than super chargers and you don't really hear it til you get on it. It does require premium gas though. But If you're not familiar with working on an engine or are afraid of hurting something I'd stay away from forced induction in general. As far as "contaminates" getting sucked in, are you guys not running air filters?? And if you use the right size turbo it's not "sudden" or only in high rpms, and besides that you still have the stock baseline of a 4.0l which isn't a lightweight to begin with. The only reason I'm not running the same on mine is I'm pretty sure the jeep may rust apart in the next few years and don't wanna spend more money on it.
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I agree with you for a Jeep on the road in conditions you described, but on trail, I still think it's really not worth the money. Also I agree, as you said, a turbocharger would be much more beneficial than a supercharger for the application you described. I also agree with BobNH, for MOST Jeepers, even with a good air filter, you are risking more engine damage with a FAI Jeep being they are in dirty environments much more than a street vehicle would be and you now have an extra instrument pushing air into the engine.
 
Well me having a TJ and wheeling it pretty hard I have never found myself in a situation where I thought to myself " shit if only I had more power". I honestly think that a turbo of any kind would be pointless on a jeep


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How are the rings on the stock 4.0L?

I don't know much about the motor because I haven't bothered to research but I have seen that the CR is quite low. If the rings are fine then it seems like a great candidate for a "junkyard" turbo project (prices I've seen for kits are just ridiculous). I've had great success with similar projects when I was into cars (autocross). Other than fuel management, the only other challenge is the exhaust manifold. But if the stock manifold is strong enough to support the weight of a turbo, a welded on flange takes care of that. Additional bracing can be fabricated pretty easily for insurance. Find an old Powerstroke intercooler, chop it down to size (whatever you deem reasonable) and put new end tanks on it. I actually built 3 intercoolers out of one PS intercooler. Selling the other 2 recouped all my intercooler cost, plus a bit. Then find a box of random mandrel bent piping and for the intercooler.

With the right size turbo your torque curve will be quite smooth, and with a stock-ish exhaust the whole thing could end up as quiet as OEM as long as there isn't an external waste gate.

I think the project sounds like a lot of fun but I believe all that matters is whether you think it's fun. Who cares whether other people think it's practical. I love to off-road my jeep but the sad truth is I also commute to work in it. A little boost would be nice... not for off-road but for all those unfortunate times when I'm on-road.
 
The rings are fine but none of the internals are forged so it can't take a lot of pressure but like 15 or less with a good tune is safe. What people forget is the 4.0 from factory is tuned pig rich. So a good tune and turbo increases fuel economy significantly.

And for never feeling like you need more power, that's cool, but others do. That's why people ls and diesel swap these. Turbo is more fun then swapping engines imo.


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Snboarder113 said:
The rings are fine but none of the internals are forged so it can't take a lot of pressure but like 15 or less with a good tune is safe. What people forget is the 4.0 from factory is tuned pig rich. So a good tune and turbo increases fuel economy significantly.

And for never feeling like you need more power, that's cool, but others do. That's why people ls and diesel swap these. Turbo is more fun then swapping engines imo.


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I am surprised to see the 4.0 is tuned "rich". Having owned one, I can say my opinion on it is that it is actually quite lean. Disturbingly so. So much so that it is the only vehicle I ever owned where the owners manual says "spark knock is normal". I agree the engine was designed that way, but my understanding is it was leaned out to meet emissions. I would have loved to have some extra fuel in the cylinders to cool it down. I was able to do that with my Volvo turbo, using Ford svo injectors and soldering a resistance pack inline.

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Snboarder113 said:
The rings are fine but none of the internals are forged so it can't take a lot of pressure but like 15 or less with a good tune is safe. What people forget is the 4.0 from factory is tuned pig rich. So a good tune and turbo increases fuel economy significantly.

And for never feeling like you need more power, that's cool, but others do. That's why people ls and diesel swap these. Turbo is more fun then swapping engines imo.


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Well shit.. might as well go big then to get all that extra power out of a tj. 94mm turbo and convert to M5! That should give you some HP!
 
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I did a zj way back when with a t3-t4 off a chrysler le baron. It was running about 9 psi and really woke that thing up. 4 hole injectors are a must for the older engines. With the low boost i was able to get away without a custom tune. It was a rather simple install compared to some ive done. Small intercooler behind the grill and a builder kit for the piping.

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That would be perfect! Someday I might do an old Volvo or mitsubishi T3... run 6 - 9 psi. 4 liters would have the turbo spooled by 2000 rpms easily, and probably be off its peak by 3500. I think my budget for this project would be in the $1200 range...


A big challenge might be keeping the turbo cool while crawling around on trails at low revs & low throttle. Might have to experiment with the right size water line & maybe even ventilate the hood. If the stock manifold can handle the heat, exhaust wrap would help with under hood temps significantly.

Bench racing is fun... ;-)
 
I love forced induction, but as others have said, on a Jeep the power isnt applied at the right times. I wish somebody could figure out a way to tune say a Ripp supercharger for the JK so that the power is always optimal, and figure out the overheating issues they seem to cause.

Dammit I just gave myself ideas :doh:
 
longarmwj said:
I love forced induction, but as others have said, on a Jeep the power isnt applied at the right times...
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Are people finding their jeeps (especially 4.0L's) to be under powered on the trails? I feel like the stock power & torque output are great for the time I spend off-road. But I do avoid mud holes, etc. My additional power needs are for when I'm merging into traffic on the way to work or passing on the freeway. I hope that one day my jeep can be a weekend warrior but at for the near future I have to drive it to work as well.
 
sm31 said:
Are people finding their jeeps (especially 4.0L's) to be under powered on the trails? I feel like the stock power & torque output are great for the time I spend off-road. But I do avoid mud holes, etc. My additional power needs are for when I'm merging into traffic on the way to work or passing on the freeway. I hope that one day my jeep can be a weekend warrior but at for the near future I have to drive it to work as well.
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I really like the 4.0 in the tj. Has a great amount of torque for that size vehicle and they last forever in my experience.
 
sm31 said:
Are people finding their jeeps (especially 4.0L's) to be under powered on the trails? I feel like the stock power & torque output are great for the time I spend off-road. But I do avoid mud holes, etc. My additional power needs are for when I'm merging into traffic on the way to work or passing on the freeway. I hope that one day my jeep can be a weekend warrior but at for the near future I have to drive it to work as well.
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Don't know what kind of wheeling you do. But at least for me in California, all of the wheeling here is slow going crawling really. I feel having a turbo would get annoying on a trail. Always waiting to build boost and for the turbo to spool up.
 
I think some of you guys are missing the point of the question. Obviously at normal trail speeds boost of any kind is not needed. I really don't think anyone who is thinking about a turbo upgrade is considering it for trail benefit. We all know with any stock power plant Jeep weather you have done a great changes or not, they are not highway power houses. The benefits are all highway and daily drivability. Improved fuel economy and at speed power are where this upgrade make your Jeep feel like you have a small block under the hood. I agree the aftermarket kits out there are way over priced. With the amount of tuner shops out there today it is easier to get that part accomplished. I have been researching this for my xj and will be pulling the trigger in the next year. Anyway, not sure that my opinion matters but thought I'd chip in.

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