What effect would larger throttle body have on 99 stock 4.0L

[JPrubo]

http://jeep4.0performance.4mg.com/intake.html

There are some numbers take them for what you want. But doesn't simple logic tell us that a bored throttle body will help with throttle response. Let's look at it very simple.....the throttle plate limits the RPM of the motor by controlling the amount of air into the motor. With the plate closed there is just a very little crack around the plate and the holes for the IAC of course to allow air in. As you twist the plate you increase the hole opening allowing more air into the motor increasing RPM and power. So if you have a larger hole then it would take less twist of the plate to let air in. Basically 1/4 throttle becomes 3/8 throttle and so forth. Then at the very top end 100% throttle becomes 105% (these numbers are just examples), now if your engine can use all the available air of 105% throttle you will see and increase in power. If you have a restriction else where where it can't fill the throttle body to 105% you will get nothing or perhaps a loss. None the less you will fill an increase through out the lower throttle positions as you will be effectively opening the throttle more with less pedal movement. This is the increased throttle response so many talk about. So yeah you should fill a difference with a bigger or bored throttle body. How much will depend on what else you have done to effectively take advantage of it. With our strokers the wot throttle numbers may be more then enough but why wouldn't we want to bring the power at a lower earlier position.

[JPrubo]

Well, I just finished porting and polishing a 4.0 throttle body. I intend for it to go on my stroker but decided to bolt it onto a friends stock 4.0 to see how it acted. This was a completely stock engine with stock intake and exhaust. There did seem to be a slight improvement in throttle response but a more noticeable drop in WOT power. I am assuming this is due to the removal of the tamper at the bottom of the throttle body. I figure this necking down of the bore increases velocity of the air charge at WOT. Next is to remove it from this stock engine and put it on one with intake and exhaust upgrades.

[darkcorp]

I researched the issue of the stock throttle body's adequacy using two methods.

1. Throttle Size Calculator https://www.classicfuelinjection.co.uk/throttlecalc:
- factory 56mm throttle body produces exactly the factory 180 hp.
- a 62mm throttle body can handle 221 hp.
- 4.7 V8 throttle body comes in two sizes: 65mm and 68mm. They produce between 243-266 hp. Factory 4.7 V8 power range is 220-265 hp.

2. Formula from a book for calculating throttle body diameter:
- for a 4.0L, 56.5 mm is required at 4500 rpm.
- for a 4.6L, ​​63.8 mm is required at 5000 rpm.

Accordingly, if you have more displacement or revs, you will need an even wider throttle.

BTW I make drilled TBs for 4.0 (renix & mopar and latest 2005/2006), 3.7/4.7 and 5.2/5.9.

TB calc.jpg

TB formula.jpg