This seems roughly inline with the dyno graph contained in Go-Jeep's article showing an improvement way above the normally driven range. Although that test, too, has a modified fuel system!!!

Thanks for sharing

 

That's right

 

The other potential issue with the 99+ upgrade is fuel economy.
Larger plenum, more airflow = more gas.

Just like sliders, swampers and all the other things we do and add = more gas.
So maybe it is not an issue...

 

I'd start with the injectors. 30-45 minutes & you should be done.

I have $50 in my injectors & intake. One reason I did it.

 

Here's something from the other side of the spectrum. I found a 99 AT computer in the junkyard and thought what the hell, I'll try it in the 98 MT. Turns out, it works even if the TCM isn't there and doesn't have a coil pack. Only codes I got were from the missing TCM. The other main issue I noticed is that my oil pressure gauge stayed on zero. Drive-ability was good though it took a little while for it to get idle right. It even died on me a couple times. But the most noticeable thing was 60-80 mph. I have swapped to 3.55's with my MT and holy cow... Just changing the computer was like a whole other engine. So I believe that an intake, injector, AND computer swap will be where the biggest differences will be noticed.

 

Can you rephrase that? You post reads like you swapped to 3.55:1 gears and saw an improvement.

Also, on an OBD-II Jeep PCM, when you remove battery power for any period of time, you ditch the adaptive memory and it defaults to a "run rich" program until it relearns the vehicle's normal parameters after about 50 warmup cycles.

 

Yeah. I'm confused also.

But then again I can answer a simple question and be a butthead to some people.

 

I swapped to 3.55's long before I started playing the PCM shell game. But going from the 98 PCM that came with my jeep to the other 4 97 and 98 computers was pretty much the same performance across the board. When I put the 99 in, it was like a whole new engine. And no I haven't put on a 99+ intake either. Still have my 98 intake.

 

so I have to ask this question. one of the bigest things I've ever heard of as a down fall for a inline six is the uneven air distrubution to the furtherest cylinders from the intake. case in point on the jeep ho one and six. on a bmw s54 its 5 and 6 this is why there ITbs have larger airscoops. on the jeeps with the 99 intake the cylinders have a equal chance to grab air for one because of the runner design and two the fact they allow more air than the heads are designed to use. is this not the main point of the redesigned intake?

same concept renix intake is a better mainifold than the ho do to the larger runner design thats why renix engines respond to a bored throttle body cause the factory ones dont allow enough air in.

as for the rpms I like the improved power of the injectors/99intake/header/bored throttle body on my jeep. allows me to be able use the engine all the way up to 5400rpms.

 

I've been searching for injector and intake manifold swap for my zj cheap. One time 25 bucks for a99wj intake but I had no extra money

 

ZJ? Do you have an XJ?

 

No. I have a ZJ.

 

You're in the wrong part of the forum then. Try this link:




https://www.cherokeeforum.com/f5/

 

AFAIK ZJ injector swaps should be the same as the similar generation XJ. Same fuel system, same 4.0 L. Dunno about a year split but the OBD-II ZJs I've seen have EV6 injectors with Jetronic, like pre-99 XJs

 

Good to know. He's in the wrong part of the forum.....