Can someone tell me what size throttle body i should use..i want to install some 12 hole injectors and i am going with a 62mm throttle body...but my buddies said i can go larger..how large can i go with my tb...and does anyone have a part number for a correct set of 12 hole injectors..there for a 97 xj with a 4.0L eng..

 

A 62mm is fine. 12 holes are not going to add any power that wasnt already there with good working stock injectors. You could save your money on those 2 items and put it toward an ECU tune that will probably net you more gains.

 

Many people have better throttle response after switching to 4 or 12 hole injectors. I have 12 hole injectors, APN header, 62 MM throttle body, and a 2.5" exhaust with no cat and my throttle is very sensitive.

 

that's the setup i want to run...what's the increase like..

 

Disagree with the injectors, I added 4 holes and the response off the line was immediate and noticeable.

 

62mm is the biggest you can go without opening the opening in the intake itself.

 

Did you first install new single hole injectors to see what your off the line performance gains were? Im not saying it's not possible but there is a good deal of subjective data that's thrown around. I have singles, 4 and 12s installed on 3 different Jeeps but I dont have any objective way of measuring the benefit of having them over one another.

The price I got from the mods above comes out to $600-700. I would bet that more power and responsiveness can be had with a 89 octane tune for less money. Those gains would be backed with objective data from the tuner.

 

Who makes tunes for our computers, and can they tune it so it will make more power but still run regular 87? There is no way I am paying for premium fuel.

 

JTECs can be reprogrammed. Syked ecu, Flyin Ryan and maybe Chris tuned if he is still at it. 89 is mid grade but allows more advanced timing. I run premium 93 on my set up and for what I get out of it it's worth it to me.

 

Everything I had seen pretty much said that 4.0s are tapped out from the factory and a tune doesn't really change much on them. I've never very seriously looked into a tune though.

 

Contact one of them and see what they can do for you. Personally I would go to Ryan first because he works directly on the JTEC ECU and has a very good reputation.

 

I tried contacting Flyin Ryan a few months ago about tuning my Dakota but never got a response.

 

Try him again. He got right back to me not long ago or contact syked ecu.

 

If u need a throttle body. I'm your man

 

What he said^