countryboy

I have the jeep 4.0L H.O. in my cherokee and i want to know what the
difference (more power, less fuel economy...etc) is between putting a bored out throttle body in. and which size (62mm,
62.5mm, 63mm and 64mm) throttle body sizes are the best? help?

Tural

i got 63mm and i'm happy with it. i'm not sure how much power i actually gained, because i did a bunch more upgrades in the same time.

countryboy

has anyone else tired this?

EMAXX620

yea, i also have a 63mm from stroked jeep in mine. Had a 60mm in my jeep from the PO when i bought it and wanted a bit bigger.
http://strokedjeep.com/tbody.html

dont have any complaints.
Had him cut the top bar and make a brass butterfly. No idea on actual gains though.

kbad

hey CountryBoy .... yes, every 'little' mod makes a difference .... the stock tb is 58mm at inlet (top) and tapers to ~53mm at base (bottom) - some smart engineer decided we couldn't handle a little power and decided we should ease into it! .... the intake opening of the manifold is at 63mm ....so, do the math .... more volume, no obstruction = better all around .... 62-63mm bore is good enough ... you can add a 1" spacer and you're set!

... fyi ... changing the single-nozzle injectors out for quad-nozzle injectors (i.e. from dodge neon) is easy and makes a lot of noticeable difference ... and swapping your pre-99 intake manifold for the better designed with a larger plenum is definitely a must ... see pix, left=older, right=newer ... good luck!

countryboy

thanks for the great info! but i'm interested in what your saying about the injector swap, can you give me some more information? or where i could find some?

kbad

hey man... yeah, the neon injector swap is simple plug and play and you gain some performance and mpg .... but you need to make sure to use NEW o-rings and dab some oil on them before install so they don't rip!....

...if you're interested.... i have an extra used set (6 injectors + 2 spare = 8 total) of the dodge neon 420a injectors ... you can have all eight (8 injectors) for $65, shipped .... let me know .... good luck!

00jeepXJ

put a 60mm throttle body on mine and it was noticably louder when pulling in air. Gave me a little bit more power, as for the injectors... boy did that make a difference. Swapped them out for my 00 and with in a 5 minute idle period that I did it was smoother idle and shortly after that it was a lot smoother in power delivery and application. Best money spent so far.

countryboy

what year of neon do they need to come from? and is there different neon engine sizes to stay away from?

OttawaXJ

I'd be willing to try a bigger throttle body if they weren't insanely priced but as for the throttle body spacer, you're better off putting a "K&N" sticker on your jeep as you'll get the same HP increase for less money.

1991Jeep_Man

Don't waste the cash on the larger plenum 99+ intake. Putting it on an older XJ 4.0 LOSES horsepower... and no I am not BSing, it was tested and proven.

Throttle body spacers are junk. Simple, they don't do anything. They're better for carbs, not FI.

To get the most out of a Bored TB, opening the exhaust up helps. Larger diameter pipes, high flow cat (a vendor on the site sells them) and a high flow muffler does the trick. But the engineers at Chrysler didn't make the TB the way they did because they thought we couldn't handle the power. I forget the exact reason, but it was for a reason much like the obstruction in the stock airbox.

TheJerm

I would recommend the 99+ intake for 2 reasons:

1) for the ~50-80 bucks it cost to swap it is totally worth the ease to loosen and tighten the belt. You also will probably get a better PS pump to replace the 20yr old you have.

2) It does give you more power but not by itself. I did the 99+ intake, APN header, high flow cat and muffler, i was very happy with the pick up the jeep had afterward and less downshifting on hills, none on the highway in the mountains.

WantACherokee

Can the '99+ intake be installed on a Renix engine? Or is it a ton of work?

I was thinking about having the stock throttle body bored out, but was disappointed to find out it's so much smaller than the HO throttle body to begin with.

I do intend to do some other mods. Already have a cone air filter, gonna do the injector swap and an upgraded exhaust.

TheJerm

in 99 or 2000 they changed the thickness of the intake and exhaust flanges, I belive its was in 2000. Its no a big deal but alittle massaging is needed to fit it on without bending the bolts

5-90

Considering that the OEM throttle body will support airflow for a mid-range stroker (4.6-4.7 litres displacement,) you won't gain any power installing a bored version - it's not the bottleneck.

What you can gain (and will notice) is crisper part-throttle response - most people think of that as a power gain, but it's not.

If you want to gain actual torque or horsepower, you're going to have to stick to proven engine work and turning - reprogramming of fuel/ignition curves, new camshaft (changes valve event timing,) camshaft advance/retarding (moves the peak power bands,) cylinder head port work (where the bottleneck actually is,) and stroker combinations (increases compression, increases displacement, increases low-end torque.)

If you're going to install just a bored throttle body to gain power output, save your money.