HomemadeTurbo - DIY Turbo Forum - 1994 Jeep 4.0 FI Turbo

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1994 Jeep 4.0 FI Turbo

Ok guys, i've been reading all the threads and im developing a really good understanding for this whole turbo thing but i do have a ton of questions before i start buying parts and installing them, i want to do my research before going ahead with this.

i have a 1994 jeep wrangler yj, its a 4.0L inline 6, its obd1, it has about 158,000 miles on it and seems to be running strong

i want to put a turbo on it, im eyeing a T3/T4 im not to sure what trim it is, but i want something that will build boost from about 1800-4000 and nothing about 4000 because my jeep is auto and shifts at 4000, so i want to get all my boost then, i dont really want to run over 8 lbs cause then you start getting into really unreliable situations, or at least for a stock jeep...now i have a few questions, i know how im going to run the downpipe, it will go under the engine to the turbo then out to the exhaust, so thats figured out, doing the oil lines should be fairly straight forward, the only thing im really stumped on with this whole thing is fuel management and the computer

i know that at one point 505 performance was giving an FMU from Vortech for their kits, and being OBD1 i dont know how well a piggyback will work, if i went with the FMU is that all i need? and would i have to upgrade my injectors with the FMU? i know i would with the piggyback, but piggybacks are really expensive...injectors can be too, and im on a really tight budget, any information you guys can give me will be great, also how do i know what size wastegate and blow off valve to get?

Quote:

Originally Posted by Ghost94 (Post 1307462)

fuel management is the key to power and reliability. an fmu is not fuel management. all it does is overly richen up the mixture when it see boost. there is no fuel management about it. it also dangerously rises your fuel rail pressure. this can cause injector damage and fuel pump wear.

the best thing for you to do is install larger injectors and have it tuned. there is no other option for reliability that you are looking for. a custom tune will give you the best power output and reliability.

boosting without a tune is just like using your money to light a camp fire......

Ya FMU's are not tuneable and therefore unreliable. Best bet is to go standalone or some type of software you could put in your OBD1. But i am not sure if jeeps have software like that. If your on a tight budget just wait a bit longer and save up some more cash and do it the right way.

look on the pirate forum, there is a few projects there.

If you have a 94, it's very likely you have a Dana 35 being pushed by an AX15 transmission. The AX15 is pretty good up to a point, and has been used behind some V8's..... but....yea, BUT.... the Dana 35 is your weak link here. Most of the guys are going to Ford 8.8 rear axles, and the ones with the disc brakes. It's also fairly likely you are running stock 3.07 front and rear gears. The 8.8 Ford doesn't come in that configuration, so it will be a gear change to consider also. And if you 'Lift', then it gets even more complex with a CV driveshaft and slip yolk, and from there 'wedging' the axles for Caster to keep the driveshaft angles within acceptable ranges, and for the front axle to run true and self center while driving. Without the proper caster of about 6 degrees on the front, it will be twitchy and want to wander on the road. You won't be taking your hands off of the wheel, you will be driving with two hands, guaranteeee'd. So wedging the front is in order to bring back the steering.

These are just some of the mechanical items to consider.
Also consider how well the stock 4.0 performs, and how your usually under or at 2,000 rpm at road speeds. The 4.0 lives at a snails pace in this regard, but if you occasionally wind one up to redline going through the gears, they are pretty rapid and entertaining...... and satisfying. At a buck fifty on the odometer, your gonn'a need to go through the motor, and surely the cam, lifters, and pushrods, not to mention everything else like a major rebuild, otherwise you will quickly wear out what's left of your first run in this motor before its first rebuild. It's very likely you will use up your Cam, timing gears and chain, your rings and finally your bearings and gaskets. I hope I'm not discouraging you, but facts is facts. It's likely your 4.0 sounds sort of like a Diesel....? Well thats an indicator that you'v got about 30-40 K left until your gonn'a need a rebuild. That is, if you drive it sanely and not hotrod it.