I cut and pasted this from a post I just made on another thread. For your thoughts and comments-----

My comment on CAI/muffler replacement/ignition mods/tuners, etc on the 3.8 Jeep- I think that mods are much more effective on this vehicle than others and slight gains are much more cost effective because it is so underpowered. Example- my Corvette is grossly overpowered. Five horsepower on my Vette is unnoticeable. Five horsepower on my Jeep (especially at part throttle, which isnt on dyno tests and reflects 99% of every day driving) is very noticeable. If your car is 100% overpowered and is pushing 300+ hp at the wheels, 5 HP (@1.2% increase) will never be felt. When your vehicle is 30% underpowered, 2.5% increases (5 hp) will make a noticeable difference for sure and should have a measureable effect on fuel economy. That is why I advocate bolt ons for these vehicles whereas on high performing vehicles I am much more ambilvalent. Kind of fuzzy of the top of the head math, but it makes much sense to this guy.

 

Makes sense to me too. I agree with everything you said.

 

When you say 2.5% = 5 hp, that's at the top of the dyno chart, not the part throttle you said is 99% of daily driving. (202hp X 2.5% = 5.05hp)

The gain at 2,000 rpm will be substantially less.

 

I was thinking about this sort of thing the other day too. Seems interesting

 

Absolutely correct at WOT......but what is the gain at part throttle? I believe when people say they feel better throttle response, they are actually feeling more power at less than WOT. Putting aside math (because nobody dynos at part throttle), I feel any gains on underpowered vehicles are very noticeable and worth the effort. A 3300lb car at nearly 400 crank horsepower doesnt notice 5 HP. A 4100lb vehicle at 202 crank horsepower will perform noticeably better with 5 more HP, because you are dealing with a performance deficeit. (Thats been my experience anyway)

 

Ok so what's the best bang for the buck mod to boost hp in a 3.8?

 

All true; however, the hot rod rags have proven for years that you can't go add ten different hop-ups that each claim +5 hp and get +50 at the end of the day. Realistically if you take those ten and get +10 hp all together you're lucky, and then the true question becomes - at what real cost did that +10 hp come from.

In theory you are correct. In practice, it just isn't that simple. Best hope is to add minmual hp before the computer says "hey, something's wrong with me"... limp, limp. If hp were that simple to add, Jeep would have done that before they trashed it all and went with another drivetrain and computer. Ford has done that a lot times on the Mustangs. I know, I have four of them today and two put down in excess of 485 rwhp and are daily drivers.

If you go the bolt on route, the aftermarket guys will love you. My good buddy manages one of the largest Mustang/Dodge/Chevy aftermarket companines in the country and that's how they make their living. I've spent a zillion bucks and decades going that route and at some point you realize that if you can gain +50% hp in a smaller motor that gets better fuel mileage and has a better tranny (5 speed auto), go for it. That's just my experience.

There is no right or wrong, just thought I'd share with you the limitations of bolt on's if the end goal is (I want a 100 hp!!) unrealistic.

 

Ok so ill share my experience with you guys. Take it ever how you want but this is the results i got.
Im a creature of habit. I travel a highway from home to work. Literally i make a right hand turn from my driveway onto highesy, travel 22miles north and make a right into work.
I added a cheap cai intake on thursday last week. Ran it for a day and a half. Felt good. The loom of rain worried me so i removed it till i could come up with a sealed solution.
This labor day i decided to work on the intake but remembered i left the cai at work. Got in jeep and drove said road to work with stock air box and filter. About one mile before work there is about a. 75 mile long hill. Its straight andusually trans downshifts twice while climbing to maintan 60mph.
My test began here. I held the tbrottle at 60mph as it started up the hill. After the trans shiffting, at the top of the hill i was at 52mph.
Skip forward. Removed stock air box and installed cai. Drove 10 miles south back down the hill. After purchasing some materials i drove back up said hill with in 30min of first trip. Held throttle at 60mph at base of hill in same lane as before. Trans down shifted twice as before. At the top of the hill the speed wad 63mph. No not a typo.
Once the trans shifted and rpms climbed to 3000rpms the jeep began to pick up speed slightly.
Like i said take it for what you will but im just sharing my recent experiment. Im not gonna speculate on hp gain and whatnot but do feel that it made a slight impeovement. Not bad for $60.

 

You are absolutely right, many times 5hp +5hp =7hp. Some mods show gains top end, some show it at the bottom, some in the middle. I think like most guys I am most interested in gains under the curve, especially with the 3.8, which is kind of challenged. I noticed a good driveability improvement with the Banks intake. Nothing world changing, but definately more grunt. It sure isn't like it used to be when MAF cars could adapt to most mods within the limits of the sensors and the capacity of the injectors! To be fair, everything is much better optimized from the factory these days, they don't leave near as much on the table. The factory exhaust (excepting the muffler) on our jeeps looks pretty good. The reasons why the OEM doesn't make intakes and exhausts more efficient are compromises with water induction, noise levels, and durability/maintenance. All that being said you should be able to get a solid 5-8 HP with an intake and exhaust....maybe more relavantly expressed in torque (although somehow we don't talk torque in aftermarket bolt ons) annd maybe 15-20 total with a tune thrown in, and equally important under light load maybe 2 mpg. Interestingly my 96 Vette picked up 17HP with just a Corsa cat back (previous owner did this mod)....like I say, not as much on the table these days. Back in the day, LT1 cars were pulling 30-40HP with bolt ons, and LS1 cars even better. All that being said, I am an advocate of gears on fast cars, hence my Vette has 4.10s.