Bored out throttle body ?

[firehawk]

I'm curious to know if there is really any advantage to boring out the throttle body? What are the advantages, and disadvantages? Does it give any real horsepower gains, and at what price? Lower MPG?

I could pull one off at the Pic A Part here, and have a machinest at work bore it out on his Bridgeport.

[Mudderoy]

I would do it. I have read it inceases air flow, horse power and mile per gallon.

[DETOURS]

I have yet to read anyone has gained anything from them......over the years.....:boohoo:

[firehawk]

Thanks, good to know before I go out and waste MORE money and time.

Guess I'll save my pennies for this guy in Ky that makes Jeep stuff.:thumbsup:

[DETOURS]

Hey thanks.......consider a cold air intake for a'lil more umph, those can actually work.:thumbsup:

[firehawk]

Hey thanks.......consider a cold air intake for a'lil more umph, those can actually work.:thumbsup:

Question I then have is, if I get a cold air intake, wouldn't it work even better if I removed the restriction below the butterfly in the throttlebody?:confused:

Of course WHERE does one get "cold" air under the hood of an XJ?:rolleyes:

[DETOURS]

Snorkel
or
Reverse home brew snorkle exiting the air box back into the cowl vent thru the fire wall........Mine is set up that way but, Im sorry I dont have pics.

[Mudderoy]

JP magazine just recently put a intake kit on a TJ. the TJ uses teh same equal length runner intake as the 99+ XJ mani. They ran the kit and dyno'd it with and without a TBS and the results were a whapping 1hp at around 4500 and 0 gain in torque.

It did change the torque curve and it peaked sooner than it normally would have, but then again, the HP peak was much further up in the rpm band as well.

I bought a cheapo TBS for my 93 awhile back and I noticed 0 gain in the old "Butt Dyno".

Bored TB will give you a nice gain. It won't be neck breaking, but you will notice more pull in the upper RPM and the low end throttle response is sharper. This is only using a DIY 60mm bored TB, I would imagine the 62mm would be even nicer.

http://www.jeepforum.com/forum/showthread.php?t=418719

[AJsArmor]

Part of the problem is the wording that manufacturers are using to describe these throttle bodies as it's very misleading.

A lot of them are selling a port matched throttle body under the label of "bored out", which isn't quite true. The newer style TB taper under the valve so they're not increasing the overall bore diameter, just port matching the bottom half to the top. In terms of airflow, it's smoothing out the path and any hotrodder will tell you that's going to give you better throttle response.

Even on the older XJs, I have no idea why but the opening at the bottom of the TB is smaller than the opening on the intake. Not sure why they did that, but simply port matching it did increase throttle response. As far as hp/torque...meh...not enough to detect.

[Voldemort]

It will not add much unless your going to upgrade to a stroker than it is a must even at 4.5L.

[2000XJ]

Boring the throttle body will greatly increase throttle response. This is nice because you'll most likely increase your MPG since you won't have to use so much skinny pedal to get moving.

When combined with a nice intake and exhaust, you can definately increase your power numbers and you'll notice gains in acceleration.

My buddy did this in his LJ with a CAI, Exhaust and chip, and the thing moves pretty well for being on 35's with 4.56 gears.

[cher96]

Check out my Signature

You can see what I have done... My XJ has fantastic pick up after about 2500 RPM, however, I don't get great gas mileage driving like that. I prefer to always keep it under 2500 RPM.

The last thing I did was to add the 62/63mm Throttle Body. So given all things being the same when I added the Bored Out TB... my gas mileage went done... but I have fantastic throttle response.

It is my belief, and I may be wrong, that the sensors mounted on the TB pick up the added air flow and increases the Fuel Mix accordingly. IDK

I only know I drive the same as before and since I added the Bored Out TB I have to fill the tank much sooner than before and when I do the math my Mileage is 1 to 3 miles less per gallon depending on what type of driving I am doing.

I don't want to be a kill-joy, however, this is my experience with the new TB.

[jugbutt]

look at this

All Throttle bodies can be machined to 62mm, 62.5mm, 63mm or even 64mm at your request.

Absolutely no whistle!
Due to lack of demand, I have stopped stocking powder coated t-bodys. If you want one powder coated, please ask for pricing and availability.
The easiest performance gain for the money you will find. The stock 4.0L throttle body measures a mere 59mm plus a major restriction of 55mm at the bottom which keeps the air from really flowing at low throttle openings. They were engineered that way to provide a smooth takeoff and ride. Boring the throttle body 63mm straight through does away with the restriction and increases airflow at all positions of the throttle. You will notice an immediate difference in power and torque due to the increased airflow and best of all-NO turbulence from poor machining or that annoying power robbing whistle!


Custom bore sizes are available if you send in your throttle body or if I have a core available. Those wanting a throttle body for the 2.5L would benefit the most with a straight through and smaller bore.




Sensors are NOT included. Simply swap out the sensors from your stock unit. A core charge of $70.00 is required and will be promptly refunded when I receive a fully functional 4.0L throttle body from you. I do not take 2.5L throttle bodys as core.



Price for a T-body is $90.00 plus the $70.00 core. All cores must be a fully functional 4.0L T-body and the same year as the one you purchased. Cores must be returned within thirty days of receiving my shipment.


go to Leigh performamce machine.com

[Ruinator]

I bought a TB at a JY for 15$, went a machinist and he bored to 60mm straight through for 40$. Now i have a spare to boot

[4.3LXJ]

Even on the older XJs, I have no idea why but the opening at the bottom of the TB is smaller than the opening on the intake. Not sure why they did that, but simply port matching it did increase throttle response. As far as hp/torque...meh...not enough to detect.

The reason air runners are tapered is to increase air velocity which increases vacuum at the point where the air passes. Old trick in carbs to get the gas flowing better. In fuel injection, it can be done where ever vacuum is created and can be used to generate vacuum even without manifold vacuum.

[4.3LXJ]

From what I have read, boring a throttle body does not do much for a Renix motor. You need the higher flow possible in the OBDII heads. It works even better with the 99 - 00 intake which can flow better yet.

[SargDeath]

From what I have read the bored out throttle body's don't do much. But the main things with the best gains are the cold air intake with a high flow cat and muffler.

[4.3LXJ]

From what I have read the bored out throttle body's don't do much. But the main things with the best gains are the cold air intake with a high flow cat and muffler.

What I have noticed it that it doesn't do much for the Renix motors. They just don't breathe well enough anyway. But if you are using a HO motor with a 99+ intake, then you can benefit from it. You have to have a motor that can breathe in the first place, or a worked over stroker.

[W.O.R.P.Offroad]

i have a question what is the stock size?

[W.O.R.P.Offroad]

mudd partially answered it. the H.O.'s are 55 at the bottom renix is smaller anyone know the size on it?

[TheWeiss]

I have the cold air intake (solid gain in throttle response) and headers, high flow cat and a catback system. At this point it seems to me like my next (and likely) last two steps are a bored throttle body and new injectors. With all that said, is the general consensus against the throttle body?

[TheWeiss]

I posted the most recent post on this thread but never heard anything back. Does anyone have any thoughts at this point?

[bluedragon436]

A bored out TB will help... now it also depends on what size you run... If you run a 68mm TB than it isn't going to help you a whole lot... unless you rebuild your engine into a nice 4.7+L stroker... I am looking at either picking up or just boring out my stock TB to roughly 60-62mm, because that seems like the usual that you can purchase, and it seems to be the ones that most "experts" say is the perfect size for our engines... At least you have the other intake upgrades, and the full free flowing exhaust... so that will help... but as a word of "advice" if you will... I would reset your PCM after you install the new TB and injectors... so your PCM will "learn" the new setup and will adjust fuel and everything to run correctly for your full setup... just my $.02... someone else can correct me if anything I said is wrong..

[Jeepster19]

Hey thanks.......consider a cold air intake for a'lil more umph, those can actually work.:thumbsup:

I bought a K&N unit for my Xj,my mileage went down&air filter gets dirty easily.Just my opinon but a waste of money.Spent almost $315 on it and got rid of it for $100 cash!:sad0147:

[Jeepster19]

Question I then have is, if I get a cold air intake, wouldn't it work even better if I removed the restriction below the butterfly in the throttlebody?:confused:

Of course WHERE does one get "cold" air under the hood of an XJ?:rolleyes:

You won't get cold air from under the hood of a Xj,just hot air and bad M.P.G if you go with a so called cold air kit.A stock air box with a modified air inlet would be best,snorkel if you want to go that far.The best of both worlds with a snorkel,cold air&protection from sucking in water when going wheeling.:thumbsup:

[bluedragon436]

Well I thought about picking up an aftermarket big bore TB, but after talking to some people that did it, they said the best for the money mod they did as far as the TB was to take a factory one, to a machine shop and have them bore the bottom from the butterfly down to the same diameter as the top part... and the most anyone said they had spent on that was like $50... so I am going to do that now that I am back stateside.. as soon as I can find a machine shop that will do it. And all else fails if it isn't worth the mod, than I will throw my other stock one back on, and call it a day... if it does than I will do the same mod to my other stock one, and sell it for what I paid for the mod, and shipping... and will post up on here..

[Jeepster19]

Has anyone tried the high flow throttle body spacer from Hesco,Part#17009?It has a 60mm opening for the 4.0l throttle body..Anyone know the stock opening size of throttle body on a 98 Xj 4.0l engine?:confused:

[bluedragon436]

I haven't used the spacer you are talking about but have read some reviews since I have been looking at the TB bore/spacer upgrade for when I do my intake upgrade.. They all said it was a good product, but the only thing is, if you don't bore the lower half of your stock TB from the butterfly down to 60mm, the opening is only 58mm stock... so you will have 2mm of useless space with your TB spacer.. so if you can, I would take your stock or another stock TB to a machine shop, and have them bore out the TB to 60mm, from the bottom of the butterfly down... and then get the spacer and install them on your intake...