I recently bought a 1991 YJ with a 2.5L 4 cylinder Jasper rebuild and 2" lift. I'm new to jeeps so if I ask something dumb please correct me.
Are cold air intakes a good idea? What's a good brand to purchase?
Would I see a positive performance difference if I replaced the headers and cat-back with mileage?
I want to go get a 4" What brand do yall recommend?
Will 31" tires look bad with the lift?
Would I have to change the gearing in the differential?
Would the new exhaust pipes get in the way? (When I bought my jeep I was looking under it and when the previous owner lifted it no one bent in the pipe so the front drive shaft was grinding against it.)
OK, a couple of things; first off, congrats on the new purchase. The 4 banger is not most powerful engine, but it holds its own just fine, and they are nearly undestructible.
Regarding your questions, I think steel pretty much hit it dead on on the CAI and exhaust part, so I will not cover that. I think 4" lift is too much for 31's. The Jeep will look like a roller skate with this lift and tire combo. Here's a pic of mine when I had it like that (I have since moved to 33's):
You can easily stuff 31's on a YJ with 2.5L, and this may save you form having to get a SYE and new CV drive shaft (which you will most likely need for the 4" lift). You can also stay with the stock springs, and swap to TJ flares and do a bit of body cutting (google up "TJ Flares"; a bunch of articles will pop up) and fit 31's just fine, but since you seem to be a rookie, I would do a 2.5" lift instead. As for brands, there are many good ones out there; personally, I prefer Rubicon Express, but there are many others that are good.
Regarding gears, I would recommend you regear. If you have a stick, I would recommend 4.88 with the 31's. I know all the charts will say 4.88 is for 33's, and 4.56 is for 31's, but I have run 4.88 and 31's, and it plain rocked! You can actually cruise on 5th and dont need to be dowshifting for every hill that comes at you... Besides, at 70mph, the 4 banger will be running at about 3,200RPM, which is about where the little engine likes to be (that's right in the torque band). And I even had better fuel economy with this setup than 4.10 and 31's (about a 1mpg improvement).
I also disagree that the mods dont work; there are some cheap ones you can do to free up some power and make some. These include swaping the throttle body for a 4.0L one (should run you under $50), or changing from a mechanical fan to an electric one (also under $50 if you go the junkyard way). I would do these before CAI or headers. Also, keep in mind some headers are aimed at geting more HP, not low end torque. THis means that they tend to shift the power band to higher RPM's (which you will rarely use), while sacrificing low end torque (which is what you really need). In other words, make sure you research before investing on mods... Some may not be what you are looking for.
If you want tons of info on the 4 banger, drop by
www.4bangerjp.com and look around. This site is only for 4 banger owners, and has TONS of info on the little engine that could. You will find people that have modded the HECK out of their engines. Some run 37 or larger tires, some have turboed their Jeeps, some have supercharged theirs, some have built theirs to increase compression and what not, and others still run stock, so you'll get tons of viewpoints on what works and what does not.
Oh, and about your fuel gauge... It's VERY likely that the reason your gauge is acting the way it is is because the previous owner did the 20 gal tank conversion. YJ's all used the same tank, but they sold the 20 gal one as an option. The only difference is that the breather tube on the 16 gal tank is longer, and if you just remove it, you gained 4 gals. more of tank for free (at the cost that the tank reads full all the way from 20 gals to 16 gals). Also google it up, and you will find info on this.
Anyway, I hope this helps at least get you started!
:lol:
