Big injectors=re tune/ecm flash??

[Dntfkndie]

Hi all I'm new to the forum but I'm on my fourth XJ. This time I e decided to take a different approach from my last ones which where purpose built to crawl over anything. I landed myself a 2wd 96country an would like to put some more ponies to the ground. So my question for you guys is, if I put in bigger injectors like 20lb-24lb injectors would I have to flash or have the computer re tuned? I would be using Ev1 injectors I found from a online performance parts store.

[XJ Wheeler]

Shouldn't be necessary. You will probably want to reset the computer by holding the battery cable (detached from the battery of course) and hold them together. If i remember correctly you do that for 30 seconds.

Sent via messenger pigeon - i talk, he types.

[Pookapotamus]

If all you are doing is injectors it will be fine, will they run 100% efficient? No, will that make a difference? No.

The problem comes when you do more like change displacement. The stock computer is programmed for 4.0l of displacement and set for finite amounts of air and fuel. It can make small adjustments but only based on 4 litres of displacement and those set parameters of air and fuel.

Unfortunately you cannot reprogram the 4.0L pcm, you can add a jet chip, but it still does not change or modify the base parameters of the 4.0L engine.

If you are looking for more power out of the stock 4.0, find a 2000+ intake, larger throttle body, less restrictive intake tube, open the exhaust up to at least 2" from the header back, then maybe a coil pack, live wires and injectors out of a neon.

Don't waste your money on fancy injectors until you get a stroker and fuel system that can handle them.

If you really want to add horse power, go with a stroker, Google 4.0L stroker you will find tons of information.

Good luck, keep us informed.


Having 4WD means getting stuck in more inaccessible places!

[downsy]

For about 150 dollars you can pick up 4 hole Neon injectors on Rock Auto and they will pop in place of the stock single hole injectors. Been meaning to do this to my 97. Worked good on my previous XJ. Saw a slight fuel mileage increase and what felt like better throttle response. Of course that could have been because they replaced 180,000 mile old injectors to start with.

[Cheromaniac]

If you really want to add horse power, go with a stroker, Google 4.0L stroker you will find tons of information.

Just visit my sites and you'll soon be swamped by information overload. ;)

[Dntfkndie]

I really don't want to do a striker I want to stick to the 4.0. Also why does every one want a 2000+ intake? The 95- flow more cc's...

[4.3LXJ]

Actually the 00 intake flows much more. Also the runners are of equal length so the cc's are more equal into each cylinder

[Dntfkndie]

Here's a write up you guys should read, for one http://www.fourwheeler.com/how-to/engine/154-0911-jeep-4-liter-engine-myth-busting-true-lies/ While it may flow more volume it's not a good flow for the older engines. Hence why the 95- intakes flow better. Numbers don't lie. 2000+ intake is a myth. While the runners may be equal length, it's a single plane intake making it not much can of a big deal. Performance single plane intakes on motors such as Chevy small blocks big blocks fords etc, not all of the runners are equal length. Minuscule things like that really aren't going to give any power worth spending the time on unless your in a high power situation such as top fuel dragsters where every thing down to the hundredth of a second counts. so for every one with a 2000+ your actually snuffing your engine. You may get a higher volume of air in there but if your can, fuel system, an ignition system are up for that volume then your killing power.

[4.3LXJ]

On the other hand, I saw a dyno test that was just the opposite with some impressive gains. And don't forget you have to match the ports a little, which will make a difference

[Cheromaniac]

so for every one with a 2000+ your actually snuffing your engine.

I'll have to disagree. I swapped an '01 XJ manifold into my Jeep more than 6 years ago and ran it on the dyno afterwards. There were actually small peak gains of 1.8 rwhp & 4.5rwtq with gains of up to 5lbft of torque from low rpm. I also saw a near 1mpg improvement in fuel economy.
The main benefit of the newer curved runner intake is the smaller airflow variation between each of the runners thus producing a more homogeneous air/fuel mixture in each cylinder. This improves fuel economy and reduces CO & HC emissions. The only downside is that the smaller cross section runners reduce high rpm breathing but you'd only notice that in the last few rpm before the rev limiter.


I really don't want to do a stroker I want to stick to the 4.0.

That's fine. You could still do some upgrades to wake up your 4.0 such as a cold air intake, 62mm throttle body, '00+ curved runner intake manifold, header, 2.5" high-flow cat, and 2.5" exhaust. The stock injectors and PCM can handle those without any problem.
If you don't mind delving inside the engine, you could also do a performance cam swap and port the cylinder head. Then if you decide later on that you do want a stroker short block after all, all of the aforementioned performance upgrades can be used on a stroker together with oversize injectors.

[drakan1908]

I think Harland Sharp also makes a set of roller rockers for a 4.0. They improve throttle response and cut down on friction/ heat. Ebelbrock also makes an alum. head ($2000+).

sent from a van down by the river

[Pookapotamus]

My 92 also saw gains in throttle response and low end torque with the 2000+ intake.

The biggest thing overlooked with the 4.0 is the pcm, in many situations that intake will not perform better because the pcm has no way to detect or adjust for the intake, it has no idea any thing has changed, this pcm cannot even adjust for different elevations. Therefore a 2000+ intake can hamper performance or increase it depending on what environment the engine is run at.

Now you are going to say "then why did Chrysler use this pcm??" Easy, because it will run a stock 4.0 in almost any situation within a set of parameters defined to be acceptable, and it was cheap. Plus no two 4.0 are the same, there are too many discrepancies in a vastly mass produced engine that was engineered to be reliable.

Once you deviate from the norm, this pcm is no longer up to the task.

Hopefully this clears up the "I got good results, but I got bad results" issue.




Having 4WD means getting stuck in more inaccessible places!