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View Full Version : TOTM: 4.0L power mods



rstrucks
09-02-2011, 11:27 AM
Most of our Jeeps came with the ol' 4 oh and most of us want more power. If you aren't ready for a V8 swap, extracting more power/torque/throttle response out of your straight six may be the way to go.

So, what are the good, cost effective ways of getting more out of the engine?

zjeepin
09-02-2011, 12:14 PM
Stroking the 4.0 is a good option buuut not very cost effective..

99+ intake is cheap
Upgrade injectors.
Bored Throttle body
Port and polish intake and exhaust ports
shorty head gasket from mopar performance
exhaust mods..

i'd ported and polished my 4.0, 99+ intake with bored TB and upgraded injectors.. runs damn good IMO.. i think others would agree.

the single cheapest and most effective mod was the port and polish although its hard to say if that would have made much of a difference without the intake and tb mods.

Mtn WJ
09-02-2011, 01:50 PM
Here are my observations on the mods I have done to my 2001 4.0 WJ.

first mod was a KN filter. Did not do much except I like the idea of being able to clean it and not have to replace the element.

Second mod was a cat back type system. I basically had a Deltaflow type muffler and 2.5 inch exhaust installed after the Cat. This did improve highway performance and mileage to a small degree but was noticeable. I now have a Cherrybomb and 2.5 inch pipe. The glasspack style muffler made a larger improvement and sounds better. The previous turbo style muffler never sounded right to me.

Third was a Fastman 63mm bored throttle body. - This made a definate improvement in highway power and a bigger improvement with mileage. Go figure bigger bore and better MPG. I was able to maintain highway speeds climbing the mountain passes on I70 - pretty much at will with 32 and 33 inch tires and running 4.10 gears at the time.
However I still had some transmission gear hunting and suffered some pulling my pop up camper on hwy 285.
I now have 4.56s and the mods listed above. I can climb drive anywhere at will at or above highway speed in the Colorado rockies with no gear hunting. I can also pull my camper on the 285 passes at the speed limit. I have not pulled my camper on I70 with the 4.56s but suspect it will be better than before but feel some of the passes will be under the speed limit.

Is it a race car? no way. However I am not the one in the slow lane and that is all the matters to me.

I feel with the 99 and newer 4.0s it does take the combination of the intake/filter, TB and Exhaust to make a decent change in power. Gears are just as important. I liked the 4.10s with 32 inch and smaller tires. 33s need 4.56s and I suspect 35s would be best suiited with 4.88s. It seems the 4.0s powerband range is best suited with the correct gearing more than other engines I have had.

I know that the 99 and newer 4.0s in the WJ have several differences over the previous 4.0s. Intake manifold has larger smoother bores, exhaust manifold mimicks a header than a typical cast manifold, ignition uses coil packs rather than a distirbutor and the CPU has a wider threshold with better abiltiy to adjust to air/fuel mixture changes. The WJ 4.0 also comes with a larger volume water pump.

Remember to keep your cylinders inline with the 4.0 to go.

ajmorell
09-02-2011, 01:52 PM
My 4.0 is pretty decently modded. It's hard to say what made the most substantial difference because I went from a basically stock motor straight to one that has a bunch of work done to it. The 4.0 doesn't breathe worth a shit in stock form so anything you can do to improve that will help. My list of mods includes a 99+ intake manifold (gasket matched/ported), head work (valve grind, port/polish), a good exhaust (banks header - ported, 2.5" mandrel bent the whole way out), and an improved cam (comp 68-232-4). Plans are to add a bored TB (on the way), upgrade the injectors (to the style with the improved hole design), possibly do something with the air intake, and look into having it tuned. In hindsight if I could change one thing, I would've had the head decked to bump up the CR a bit.

ajmorell
09-02-2011, 01:54 PM
My 4.0 is pretty decently modded. It's hard to say what made the most substantial difference because I went from a basically stock motor straight to one that has a bunch of work done to it. The 4.0 doesn't breathe worth a shit in stock form so anything you can do to improve that will help. My list of mods includes a 99+ intake manifold (gasket matched/ported), head work (valve grind, port/polish), a good exhaust (banks header - ported, 2.5" mandrel bent the whole way out), and an improved cam (comp 68-232-4). Plans are to add a bored TB (on the way), upgrade the injectors (to the style with the improved hole design), possibly do something with the air intake, and look into having it tuned. In hindsight if I could change one thing, I would've had the head decked to bump up the CR a bit.

I should also add that I'm running a hotter ignition system with platinum plugs that the gap is opened up on...

DJJordache
09-07-2011, 01:31 PM
yeah what they said, mine:
port polish head
LS1 valves (intake and exhaust)
port match head to intake and vice versa (including gasket)
99+ intake swap
polish runners of 99+ intake
grind down ports of 99+ intake on all 6 ports to make them equal on the area around the injector boss
22.5lb (or 23lb I can't remember right now) injectors @49psi
Hesco adjustable FPR @49PSI
Crane multispark ignition system
2.5" mandrel from the exhaust manifold back
had a banks header but that cracked 2x, so now I have the ebay special with the flex joints on 1&6 and can't tell the difference between the two
turbo city intake (will modify it soon, maybe to cooler air in front of windshield cowl)
60mm TB
62mm TB spacer (only b/c I got it CHEAP)
Carsound OBDII high flow cat
Magnaflow (will change to a custom one I'm building in future)
thats all I can remember right now.

soon:
taurus fan = I dyno proved that a fan clutch in "max thermal lock" (not locked solid) can pull IIRC 12hp at the ground.
further:
4.7L - 4.9L stroker dunno what route I'm taking yet, but at least custom parts are in the mix.

ATL ZJ
09-07-2011, 09:11 PM
This is a TOTM, really? jk Ryan thanks for doing a great job with these.

My 4.0 "power" story is pretty simple. I ported and polished the head on my 4.0, swapped in a thinner mopar performance head gasket, and did my best to port match the original zj (non 99) intake to my ported head. Just those nearly free mods, combined with an existing k&n cone filter, homebrew intake and a decent exhaust system with a header that wasn't cracked made it run so much better. The biggest difference was that it wanted to rev and did a better job of staying in the mid-high rpm band even while spinning four heavy 40" LTBs on rough surfaces that would bog the motor down before.

I still like the 4.0 for its simplicity and durability (we have rolled and flopped rigs with 4.0s in our regular wheelin group many times without any damage). Ultimately I swapped mine for a 6.0 but if I had to go back to a 1994 Jeep motor I would swap the 4.0 back in long before a 5.2. It deserves a lot more credit than it gets so I'm eager to see where this thread goes with guys like ajmorell and djjordache who really know 4.0 performance posting up.

DJJordache
09-08-2011, 10:33 AM
oh yeah forgot about my brothers XJ that we built
4.7L Stroker
Ross racing custom made pistons to keep the CR stock.
port polish head
Mopar 5.9 valves (intake and exhaust) (same size as LS1 but stock diameter stems)
port match head to intake and vice versa (including gasket)
99+ intake swap
polish runners of 99+ intake
grind down ports of 99+ intake on all 6 ports to make them equal on the area around the injector boss
5.0 motorsprts 24lb injectors
Hesco adjustable FPR
Borla long tube header that has been modified to have a 3" collector
3" mandrel from the exhaust manifold to the cat & muffler that has dual 2.25" outputs to mandrel dual out
ARB snorkel that we actually measured some "ram-air" effect at speed (measured by repeatable changes in vacuum)
modified stock airbox to allow the snorkle and more airflow.
68mm TB from a 4.7L dodge/jeep v8
custom TB spacer if you can call it that, but it's really an adapter plate for the intake 4bolt to the TB 3 bolt mounting
opened up intake hole to 70mm for the new TB size.
4" custom airhat to allow more airflow into the TB but allow the hood to still close.
Custom made adjustable MAP sensor mod
Carsound OBDII high flow cat
Magnaflow (will change to a custom one I'm building in future)
Custom mod to the TPS to work with the new TB and the Renix system on the XJ.
Flowmaster super40

thats all I can remember off the top of my head right now.:smt082

Mtn WJ
09-08-2011, 11:27 AM
DJjordache, any ideas on how much power either of the those two 4.0s are putting out? Torque or Horsepower?

I saw a 4.6 stroker light up 33s in 1st and second on a YJ. Not just a chirp, lightem up baby. Lots of torque with the strokers.

DJJordache
09-08-2011, 11:48 AM
I'll have to look up the HP TQ on the XJ when I get home later.
but on my ZJ the link in my sig shows dyno's and my final result was at the engine (calculated drive train loss) HP: 227 / TQ:256.
I do know that the before and after on the stroker was a dyno proven gain of 51%HP and 60%TQ. But I'll dig around for the final numbers.

Here is more info on that Stroker XJ:
FYI some things have been redone since this post back in 2005, exhaust is now mandrel, different cam and lifters (crane sucks)
http://www.jeepsunlimited.com/forums/showthread.php?t=382042

03wjay
02-21-2012, 11:05 AM
Anyone here have experience with 505 performance cam kits?

ZJ TINS
03-09-2012, 10:04 AM
ATL ZJ, did you see any gas mileage change with your mods? Seems like everything you did should make a more efficient air pump but I wonder if it did any good in the mileage dept.

I have an extra head and I plan on porting and polishing and match transitions. I sure could use some better gas mileage.

Any recommendations on tools to use, not use, techniques?

ajmorell
03-09-2012, 10:38 AM
ATL ZJ , did you see any gas mileage change with your mods? Seems like everything you did should make a more efficient air pump but I wonder if it did any good in the mileage dept.

I have an extra head and I plan on porting anf polishing and match transitions. I sure could use some better gas mileage.

Any reccomendations on tools to use, not use, technichues?

I used a dremel with a grinding wheel on it when I did my intake manifold. I had the head done by the shop, so I don't know what they used. I imagine a pneumatic die grinder would be about perfect.

ATL ZJ
03-09-2012, 07:48 PM
ATL ZJ , did you see any gas mileage change with your mods? Seems like everything you did should make a more efficient air pump but I wonder if it did any good in the mileage dept.

I have an extra head and I plan on porting anf polishing and match transitions. I sure could use some better gas mileage.

Any reccomendations on tools to use, not use, technichues?

Mileage probably was better. It was difficult to measure since my rig was 100% trail duty at that point, saw very little use over 40mph and I didn't have a speedometer/odo. I did notice slightly less throttle was required climbing some of the mountains around here on access roads. It ran a lot better but it was still a 4.0.

I bought a cheap HF abrasive set for a dremel and used pretty much the entire thing on the head. It worked really well and only took a few hours to port/polish. Go slow and read a few guides to porting before you start. They are all over the web.

My only other advice is to clean everything extremely well after porting (obviously). It is also a great opportunity to get out the parts cleaner and wire brush and clean up a lot of the brackets, fasteners, etc that tend to collect grime.

zippoflint
04-02-2012, 01:32 AM
Hesco supercharger!!