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Turbo 4.0l ZJ

201K views 627 replies 116 participants last post by  TurboTPI 
#1 ·
I am starting a project. I have a turbo on the way for my daily driver/weekend worrier ZJ. I have experience in turbo setups. The 4.0 has a strong bottom end and I'm going to push it. My thoughts are 5-7 lbs of boost on 93 octane. I'm going to do a fuel management unit at the ratio of 12:1. (12psi of fuel pressure to 1lb of boost) Photos will follow. Wish me luck. Lol. This will be a test of the 4.0l engine. Mind has 210,000 miles on it now. We will see how it holds up. It currently does not use any oil or leak any. And I take very good care of it maintenance wise.
 
#569 ·
Jjmx11 said:
Alright thanks and what about a blowoff valve? Did you add one?
No blow off valve. With my intercooler piping I don't have alot of room to add one and I'm not very concerned about having one at my boost levels.
 
#570 ·
otmtex said:
Im sorry if you posted this already, Im on the edge of trying to turbo my 98 ZJ,I have some background with building turbo drift cars, No tuning though always had my ECU Remapped by a expert (Enthalpy Tuning), what kind of FMU are you using to control the fuel and air?

Thanks
I was using a vortech FMU that would come with their supercharger kits. But I removed it cause it quit working and I just have an adjustable fuel pressure regulator and 36lb injectors. I dialed in A/F ratio at wide open throttle via fuel pressure and actually like how it runs better now
 
#585 ·
So with 36lb injectors and a FPR your seeing better performance and Im guessing A/F ratios? Thats awesome man, its great to get simple yet successful. Do you mind sharing some of your Pressure readings so I have a ballpark of where to start? I still have my AEM Wideband from a 240sx I can throw on the ZJ. And you said to swap out the fuel rail from my 98 to a older fuel rail?

Another question when are you seeing boost kick in RPM wise? I would think since our 4.0l dont rev very high, maybe Ill try a smaller turbo, T28BB possibly? I'd like to see boost soon cause Im running a 42re and normal driving I usually dont see above 2,000rpm unless im 3/4 throttle down.

-Mark
 
#572 ·
Aeromotive. It's a universal one. It increases fuel pressure 1lb per lb of boost. (1:1)
 
#573 ·
Though, you may not NEED a BOV, it would be a good idea to have one.

If you do install a BOV, you'll need to decide what kind. You have two options, an open atmosphere, or an upstream BOV. Open atmosphere dumps out to the open air under your hood and gives you that cool blow off sound. Upstream BOVs redirect the pressure release upstream back to the air intake. So the next logical question is, "How do I know which one to use?" The answer lies with where your air volume sensor is located.. Basically if you have a MAF (Mass Air Flow) or MAP (Manifold Absolute Pressure) sensor. You see, these are what the computer uses to determine how much air the engine will have, and thus how much fuel it needs.

With a MAP, the sensor is at the throttle body, so when you dump your pressure from letting off the accelerator, the sensor gets a "realtime" feed of how much air is coming in, because the change has occurred BEFORE an air volume reading was taken; so the ECU gives you the right amount of fuel. With this setup, you would use the BOV that dumps to open atmosphere.

With a MAF, the sensor is most often located at the filter or "Air Box". This means that the air volume reading is taken before the turbo system, meaning that any changes in the turbo charged air are made AFTER the ECU has taken an air volume reading. So if you let off the accelerator and dump your pressure, you've changed the air volume that the computer is calculating for, but AFTER it's made a reading on that volume. So, you need a BOV that will redirect the dump back up stream to where the MAF sensor is located, so that your computer readings are consistent with the air volume you are feeding your engine.
 
#574 ·
TurboRubicon said:
Though, you may not NEED a BOV, it would be a good idea to have one.

If you do install a BOV, you'll need to decide what kind. You have two options, an open atmosphere, or an upstream BOV. Open atmosphere dumps out to the open air under your hood and gives you that cool blow off sound. Upstream BOVs redirect the pressure release upstream back to the air intake. So the next logical question is, "How do I know which one to use?" The answer lies with where your air volume sensor is located.. Basically if you have a MAF (Mass Air Flow) or MAP (Manifold Absolute Pressure) sensor. You see, these are what the computer uses to determine how much air the engine will have, and thus how much fuel it needs.

With a MAP, the sensor is at the throttle body, so when you dump your pressure from letting off the accelerator, the sensor gets a "realtime" feed of how much air is coming in, because the change has occurred BEFORE an air volume reading was taken; so the ECU gives you the right amount of fuel. With this setup, you would use the BOV that dumps to open atmosphere.

With a MAF, the sensor is most often located at the filter or "Air Box". This means that the air volume reading is taken before the turbo system, meaning that any changes in the turbo charged air are made AFTER the ECU has taken an air volume reading. So if you let off the accelerator and dump your pressure, you've changed the air volume that the computer is calculating for, but AFTER it's made a reading on that volume. So, you need a BOV that will redirect the dump back up stream to where the MAF sensor is located, so that your computer readings are consistent with the air volume you are feeding your engine.
If I buy a turbo with a internal waste gate do I still need a BOV?
 
#578 ·
Yes. A BOV is useful for when you are hard on the throttle at full boost, and let off the gas and the butterfly valve closes completely, leaving all that boosted air between the turbo and throttle body nowhere to go, forcing it back through the turbo. The sound it makes is known as turbo bark. The BOV releases all that pressure so it doesn't go back through the turbo, but on low boost it doesn't matter as much.

For example:

 
#579 ·
Luke95 said:
Hey turboTPI Howd you tune a no return line setup like on a 97+ on the cheap?:thumbsup:
Go and get yourself a fuel rail off an older return fuel system 4.0l. That's what I did. Mine was returnless also stock.
 
#581 ·
Freestyle713 said:
Yes. A BOV is useful for when you are hard on the throttle at full boost, and let off the gas and the butterfly valve closes completely, leaving all that boosted air between the turbo and throttle body nowhere to go, forcing it back through the turbo. The sound it makes is known as turbo bark. The BOV releases all that pressure so it doesn't go back through the turbo, but on low boost it doesn't matter as much.
Yep, I never got around to putting a BOV on cause its not critical at my boost level. I figured if Turbo Buick Regals don't have them stock and they run about 15lbs of boost, I'll be fine. My dads Buick GN has 120,000 miles on it and the original turbo is still fine and its been running near 20lbs.
 
#582 ·
TurboTPI said:
Yep, I never got around to putting a BOV on cause its not critical at my boost level. I figured if Turbo Buick Regals don't have them stock and they run about 15lbs of boost, I'll be fine. My dads Buick GN has 120,000 miles on it and the original turbo is still fine and its been running near 20lbs.
How many lbs you running
 
#586 ·
I think base fuel pressure is in the 65lb range if I recall correctly. With the turbo I have, it will start building boost around 1800-2000 rpm
 
#587 ·
Turbo, I got the same t3/t4 turbo as you, along with the adjustable fuel pressure regulator and so far oil feed line. What did you use as a downpipe? Also the manifold pipe that has the four holes on the turbo? I'm thinking of running 10-12psi on 93 octane. Is an intercooler a necessity?
 
#588 ·
ryanfuscozj said:
Turbo, I got the same t3/t4 turbo as you, along with the adjustable fuel pressure regulator and so far oil feed line. What did you use as a downpipe? Also the manifold pipe that has the four holes on the turbo? I'm thinking of running 10-12psi on 93 octane. Is an intercooler a necessity?
The turbo compresses the air. As you compress the air, the air heats up (basic gas laws will tell you this - PV=nRT). In order to keep intake temps down, build power, and decrease the risk of detonation, intercoolers are used to cool the compressed air from the turbo down to a more appropriate level.
 
#589 ·
Intercooler would be recommended but I am sure you could work around it. I run 8 psi non cooled on my Miata. Three important things.... High octane, a box from MSD that retards the timing at boost and I also run water methanol.

I imagine an intercooler would be easier on a jeep
 
#591 ·
TurboTPI said:
I think base fuel pressure is in the 65lb range if I recall correctly. With the turbo I have, it will start building boost around 1800-2000 rpm
Turbo, help me please. I have many questions that i could really use some help on. What do you use for fuel management? How is your air/fuel ratio; is it running too lean with all that extra air? Is a wastegate a necessity? If you tuned it, how did you? Did you use anything to retard the timing like a box or anything from msd?
 
#592 ·
I don't have any boost/retard box, but before the Intercooler it would detonate some with 93 octane at 8lbs of boost. I figured an Intercooler would be best, cools the air (more power) and no loss in power cause of retarting ignition timing. I have the air/fuel ratio at about 11:1.
 
#595 ·
Very interested in this build I think as soon as I get a few things touched up I'm going to start stockpiling for this and and saving for a paint job. Just want to confirm that what I should need on a 1998 would be.

Exhaust manifold and Y pipe from TJ (also a little curious on how that connects back to your exhaust if you could get back to me on that)
Older fuel rail with in line fuel filter and return line +Fuel pressure regulator (really unsure if oem fuel injectors will cut it but after reading whole thread seemed like I could use them especially if whats said about 97+jeeps having larger ones is true)
heater core from suburban with rear heat, water pump from buick 3.8
turbocharger itself
The oil feed line
The obvious tubing to throttle body from turbo /turbo air filter
Then I was curious about how you go to a colder plug. I feel like I should know this because I work at autozone, but is that the next metal type up or do they sell colder copper plugs?
As well as (this sounds really dumb, but you guys are more experienced with this and could throw me a quicker answer) if my jeep has the MAF or MAP and if I have the MAF if there is anyway around the upstream BOV such as I really want to get a atmospheric BOV when I turbo, but I know OBDII is going to have a fit when I go for all of this so just if theres any simpler ways or how to find someone who could program my computer or anything. I have a general idea of all of this I just rather have someone clarify for me and point me in the right direction.

Also curious about regular unleaded gas or about how to tell if I'm getting 93octane or e85.

Thanks a lot guys and thank you Turbo for this build thread.
 
#596 ·
So, to be honest, I haven't drove my jeep much this summer. I pretty much drove my car everyday. But I've been driving the jeep the last few weeks. But it really started to cool off here in Chicago the last few days. Highs in the 30's. Its awesome. The jeep is a totally different animal when it's cold. It rips!! It will spin the tires at a 15-20mph roll! It's pretty fast in warm temps, but it shreds in the cold. I Seriously need to dyno it in the cold. lol
 
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