Topic: 4.0 throttle body

[dunklervogel]

going to get 4.0 tb soon but can't figure out with all the engine mods on mine if it would be benificial to go to a 62mm or that is going to be too much. 

I'm pretty sure I read here that someone else went the 62mm bore TB route and it was too much.  The engine had idling problems and other issues with the increased airflow.  Then again some people have been fine with a 62mm.  Here is a thread about it : http://4bangerjp.com/forums/index.php?topic=1011.0

I plan on getting ahold of a 4.0 tb somewhere but use the stock bore unless I'm convinced a 62mm will run fine..   

Lanulos can you give more of a description on the difference once you got it installed?  Also, do you have a TB spacer as well or just the 4.0 TB?

[YJmechanic]

the intake i was running was a three inch pipe located across my engine cavity.  it was too big and too long.  i went to using the stock tb hose and an adapter on the left side of my engine bay.  torque came back up a little. 


i know others have seen different results with the 62mm but you have to remember my motor is 60 bored custom 426 cam, 10.5:1 compression and custom everything.  i run in a higher rpm band than everyone else.

i think i will find a stock tb first and see how that goes, if i can find one reasonable.

[SKI BOY]

i think i will find a stock tb first and see how that goes, if i can find one reasonable.
[/quote]

check on e-bay or junk yard, usually can be had for $30-50. I run 4.0 tb & tbs and saw a noticable power gain!!

[Enjoi]

correct me if im wrong but i thought most engines run lean to help pass smog, so more air in the system would make it run leaner right? But with 16lbs injectors would make it run a little more richer?

[dunklervogel]

The 2.5 in stock form is known to run rich.  Probably why mods like the 4.0 TB improve performance.. to take advantage of that.

[YJmechanic]

i have a set of 19lb injectors and a afr gauge to install soon so i got that covered now to find the tb I have watched ebay but you ad shipping and everyone is at least $50 and i haven't had the junkyard time lately.

[chrisfranklin]

I use the 62mm TB and I haven't noticed any idling problems with it (iridium plugs did seem to affect idle for a while, though).  So, I'd say the 62mm is "ok."  Course, your standard, smaller (56mm?) 4.0L TB on a 2.5L might work "more ok" than the 62mm TB on a 2.5L -  I wouldn't know.

With my 62mm, compared to stock TB, I think crawling at idle or low rpm is easier.  WOT is stronger too, obviously. 
 
I dont' know what kind of air-fuel ratio I am getting with the 62mm TB - too lean or too rich.  But, good new is that I did pass the CARB emissions ok with the 62mm TB. 

Keep in mind I am running the stock airbox/paper filter with the 62mm, not a cone filter or "CAI" set up any more (so, even with the wide 62mm TB, I don't suspect that airflow is now outpacing fuel-flow by too much in my case). 

Fairly sure the YJ and TJ 2.5s all use MAP versus MAF, so if you are starting to angle towards a big airflow combo on the 4banger (62mm TB, Cone filter, intake manifold grinding, porting) you'd want to do a MAP adjuster or a Chip (where available). 

Sounds like the 4.0L TB is a good thing for you, though.  My school never had stuff for my car