4.0 performance mods

I have my eyes on the Banks CARB approved turbo with intercooler. Supposed to be pretty easy to bolt on. The turbo is little over $3k, the intercooler is a little under $2k. I’m guessing it’s a weekend install. I have a 30k mile complete 4.0 sitting in the corner of my garage. I’ll probably do the swap first since I feel better about turbocharging a motor with 30k vs one with 123k... I chose 4.56 gears over 4.88s with a turbo in mind.

If you can afford it, do it, you'll be glad you did. I installed the turbo kit by myself over a weekend (before they offered the intercooler) and it was very easy. You do need to weld a bung on the oil pan for the turbo oil return, but other than that, you only need basic hand tools. Since my exhaust manifold was cracked in two places, I went ahead and replaced it with the Banks header. I think it was actually harder to replace the header than to install the turbo (some of the exhaust bolts were really difficult to get to).

I kept a careful eye on intake temps (it got over 200 on a hot day) so as soon as the intercooler was available, I added that. I also added the Banks cat-back, so they must love me as a customer.

My TJ had around 30k miles so it was well broken in but should still have a long life. Having twice the power has transformed my enjoyment of driving it. I hadn't gotten around to re-gearing it, even though I know I should since I'm running 35"s. With a manual I could only use the overdrive 6th gear on level ground, and had to downshift at any uphill grade. Now I can use 6th pretty much any time I want, and I don't feel the need to re-gear. I've got all the power I need for pretty much any situation, and can comfortably cruse at 75 on the highway.

$5k is a lot of money, but a local Jeep guy paid someone $12k to install a Hemi in his Jeep so, it doesn't sound bad compared to that.

For the money, I got a system that doubles the power of the Jeep, I installed it by myself in the garage with basically hand tools in a little over a weekend, I keep the reliable factory engine, and it's smog-legal in California. My gas mileage actually went up a couple of mpgs, I think because previously I was pushing the engine harder to accelerate with 35"s and stock 4.10 gears. I'm thoroughly happy and would recommend it highly to anyone interested.
 
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what is this about? I thought elect fans were a no-no.for tjs .

I put an electric fan on a few years ago, and the engine seemed to spin up faster (seat of the pants, no real data to support it) so it seemed to accelerate a little faster.

Bombing around Pismo dunes one weekend I bounced hard and heard a strange noise under the hood. A couple of the blades on the plastic fan had broken off. I broke off a couple more on the opposite side to try to balance it, and was able to drive home. I put the stock fan back on and have had it there ever since.
 
The 4.0 is an odd engine , because it isn’t really detuned , nor is it in a high state of tune either. An in-line 6 just makes good low end torque and is somewhat flat on top , and basically displacement is all that changes its performance notably , until you add a turbo or supercharger.


First , it really doesn’t need more power. Off-road , power and faster “spool up” decreases traction and causes you to blow out the tires , meaning spin and lose traction. It’s also harder on the driveline , clutch and transmission. Everything on the Jeep is designed for what that engine produces and how it produces it.

Second , if it’s lagging due to big tires , it’s the gearing . A 4.0 can’t pull larger tires effectively with stock gears, the power band isn’t broad enough . A good regear feels like a 50 hp boost .

Third , if you really need significant power , say for passing on the highway, a supercharger is likely the best option .

I love my 4.0, I have had 7. They are extremely reliable engines, and just killer in displacement and power for a light , agile Jeep....especially off road.

There is a video where on out pulls a v8 , big time .

My opinion , the best way to get more power is to get years more , by caring for it and changing the oil and air filter , which is best kept stock ...the fan blows too much nasty water off road into an open style filter like a K and N .
I know where you are coming from , I’d like it to run like my deleted 6.7 diesel ...but when that thing blows I ‘ll need a second mortgage .

I had a v 8 Jeep - it was cool , but almost violent .

Anyway , good thread , and definitely look into regearing if your tires are larger than stock...I had no idea how bad mine was until I regeared.
 
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The 4.0 is an odd engine , because it isn’t really detuned , nor is it in a high state of tune either. An in-line 6 just makes good low end torque and is somewhat flat on top , and basically displacement is all that changes its performance notably , until you add a turbo or supercharger.

It's even more awesome when you consider the basic architecture came from a 1941 Nash! Wikipedia


First , it really doesn’t need more power.

What are you, un-American? EVERYTHING needs more power! :)
(meant as humor, please take it as such)
 
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In my case. I just want sea level power in the mountains, not more power per se. So an intercooler is not in my scope. A basic turbo, super charger or a 5.9Grand V8 will do what I want, hauling a 2K# trailer up mountain passes. On the I70, Denver to Utah, a basic Banks Turbo would be a godsend.
 
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A 'cleaned-up' stovebolt 292 would be an interesting swap.
Lots of tech experience and speed /adapter equipment available.
Gain of 8cu.in. per hole.
If I were so inclined to swap in another inline 6, I'd think really hard about the Trailblazer 4200. I just haven't had the right low enough mileage Trailblazer land in my lap yet.
 
Unless you plan on putting a snorkel on you will not have a true cold air intake.. i have a mbrp catback exhaust, snorkel, bigger injectors, aftermarket cooling system, throttle body, and a m16 supercharger

Banks Sidewinder Turbocharger has a true cold air intake. I also have ant intercooler and their Monster exhaust.

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despite forum folk lore, bolt-on's with a TUNE really do wake up a 4.0! FRP recently developed their canned tune for 87 Octane and picked up 12WHP and 25WTQ on a stock 4.0 with Gibson exhaust, 4.88 gears, 35" tires, and a 5 speed. That's HUGE on the 4.0! His 93 Octane canned tune will be coming out soon, and i'm expecting impressive results.

I have a supercharger, and like everyone else has stated, boost really wakes these engines up and makes them a lot more fun on the street. However, I have a custom FRP tune with my timing and fueling cranked up when not in boost, and it's a night and day difference to how my Jeep was before (when not in boost).

So if you don't have the funds for boost, put on a cat back exhaust and a canned tune and get proven results!

4.0 Dyno.jpg
 
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His 93 Octane canned tune will be coming out soon, and i'm expecting impressive results.
There will be no benefit to running a higher octane like that without also installing a high compression head to boost the compression level. All more octane does is allow more compression to be run without pre-detonation or pinging.
 
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There will be no benefit to running a higher octane like that without also installing a high compression head to boost the compression level. All more octane does is allow more compression to be run without pre-detonation or pinging.

higher octane allows much more aggressive timing, which makes more power. I'll post that dyno chart too when it's complete.
 
higher octane allows much more aggressive timing, which makes more power.
I've been around engines for >50 years, I know how it works. Advanced timing can only do so much before the compression level needs to be raised. Otherwise we wouldn't have high compression engines, you could just do it all with timing if that was true. It's the additional compression that actually gives the additional power when properly combined with a matching cam profile.
 
I've been around engines for >50 years, I know how it works. Advanced timing can only do so much before the compression level needs to be raised. Otherwise we wouldn't have high compression engines, you could just do it all with timing if that was true. It's the additional compression that actually gives the additional power when properly combined with a matching cam profile.

engine with 10 degrees of timing vs 30 degrees of timing, all things equal, 30 degrees makes more power. detonation is what keeps us from cranking it up, 93 octane allows us to crank it higher than 87 octane... This is common tuning results and practices of 87 vs 93. Yes compression certainly will make more power, but i'm simply discussion a stock engine and incremental gains.
 
This is way outside the things I understand, but it seems like the inabilities to effectively tune the 4.0 have changed in recent years. Consumer level technology has improved and the DIY guys are catching up to what the industry has been doing for a long time.
 
This is way outside the things I understand, but it seems like the inabilities to effectively tune the 4.0 have changed in recent years.

It's drastically changed, FRP tuning has been doing some really cool things with TJ's and setting records on 4.0's! Even making crazy power with boosted 2.5's!