alright, i need help. i like the fuel mileage of my 2.5L so im keeping it, no engine swaps. ive done some research but cant seem to find out how much power the bottom end on my motor will handle, and if not much, how can i strengthen it? im running a custom intake, and plan on a 4.0L throttle body and spacer, a freeflowing exhaust with jeep wrangler headers, and possibly a supercharger designed for the wrangler. thanks for the help.

 

Making a 4 cylinder fast will kill gas mileage just as much. You can do exhaust, etc., but it's not going to give you much more.

 

If you want good gas milage and a lot of power, give up now, there is no such thing. Your four banger gets good mpg because its small and doesnt have a lot of power. If you want a lot of power you gotta decide between power or gas like dandragorange said you can do a air cleaner, exhaust, but you will only gain a couple hp

 

i'm not sure the 4.0 TB will bolt right up, and the spacer won't do much.
you can do the exaust but remember this engine likes backpressure.
and the S/C will add plenty of HP.
you will lose some milage, but its a price to pay for more performance, luckily this engine has a lot to lose before it gets bad

 

im not too worried about fuel mileage. right now i get 24 to 26, if im nice to it. ive gotten down to 18 which is the estimated mpg for the new imported 4cyl trucks, so im happy. i figure with the add ons, my mileage wont go down much during regular driving. its when i get on the freeway and someone gets next to me that i really want the power. and like i said, how much can these things handle. ive heard the 4bangers are tough, expecially iron block, but im not sure. and batman, ive read in an article about the 4.0 tb swap, and saw the pics, but if you have experience, id like to hear about it. and why does this motor like backpressure so much? thanks for the help guys
strftr

 

its a low compression engine, less backpressure= less low end power&lt\\;br&gt\\;trust me, i had to drive with NO EXAUST and it had absolutly no *****, and i’ve driven with no cat and a high flow muffler, still had more power after i put the cat on.&lt\\;br&gt\\;i havnt heard about the 4.0 TB.&amp\\;nbsp\\; so i was assuming...&lt\\;br&gt\\;i really have no idea what they can handle. i’ve put mine thrtough its paces but havnt added power&lt\\;br&gt\\;

 

im glad you told me about the exhaust, bc i was actually thinkin of removing my cat. yeah, look up the 4.0 tb swap, it doesnt give much horse, but if you can find one at a junkyard, 4 bolt only, its cheap enough. the article i read said it gives a little more kick enough for good cruising. ive definately have put mine through hell, surprised i havent threw a rod yet. im only worried about adding power over 170 to 200, bc i know main bearings go BOOM easy like that. does that muffler add anything mor than just sound?

 

I would agree don't remove the catalytic converter. It doesn't take much horsepower, can actually hurt driveability, and is a felony in the United States if you happen to get caught with it removed (regardless of whether you have an emission test where you live). Just not worth it for 5 hp in my opinion.

 

a couple other things that people seem to overlook is maybe putting on an electric fan, and also if you have A/C on it and live in an area where you rarely use it, you can remove the whole unit. it wieighs quite a bit and the belt running it robs quite a bit of power even when it isnt being used.

there is a formula somewhere i have seen, but cant seem to find it now, on if a person can free up a certain amount of weight can equal so many HP...

i dont know how much all the A/C components weigh, but i have heard some vehicles A/C units can weigh up to and over 100lbs and that is including everything, not just the compressor. if you dont want to take all that out, you can bypass the A/C pulley and gain 5hp or so i have heard.

 

im guessing the 2.5 is the same one they put in the wranglers therefore its probably just like putting a 5.2 tb on a 3.9 the 2.5 is just a 4.0 with 2 less cylinders. I loved my 4.0 in my cherokee that woulda been bad *** if they put those in the dakotas instead of the 3.9's lol.