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Topic Review (Newest First)
07-22-2013 09:17 PM
jsuggs Before trying anything else I would replace the front O2 sensor and do a good tune up to make sure that there are no drivability/ tune issues. O2 sensors only last 50-60k under ideal driving conditions. They get lazy and do not switch between rich and lean as fast as they should. I would not recommend a 4.0 TB without first upgrading the exhaust. While I have not performed this modification I have performed similar on other drivetrains. The theory of engines being fairly constant I would say that what increase or decrease that you get depends on your driving style. It will affect the power curve of the motor. At low RPM you may loose torque at high RPM you may gain horsepower. So my opinion would be that it could improve hi speed driving, but off road where you need torque it may decrease performance. So it would depend on the balance that you are looking for.

After about 200 miles of driving the fuel trim/ plugs need to be checked to ensure that it is not running too lean, which will cause major issues.

Best of luck. I learned a long time ago that what works for one person dose not work for everyone. That is why they call it tuning.
11-20-2012 09:24 PM
NalinMFG
Quote:
Originally Posted by dos0711 View Post
4BangerJP.com dyno showed improvement. Depends on what source you use.
I recently had one of their guys send me a 2.5L intake manifold and tb spacer. He wanted them bored 64mm to match his ebay 4.0 throttle body.





I don't have a 2.5L or a dyno...but you guys are more than welcome to send them my way. I'll tell you whatever horsepower you want to hear
11-19-2012 03:32 PM
armyman5000
Quote:
Originally Posted by KBR97 View Post
So you cant replace 2 missing cylinders with TB spacers, intakes and bigger throttle bodies?? lol
You sir are correct you cant replace the 2 missing cyl with that but you can with a TURBO!! BWHAHAHA check it out! looks very tempting indeed!


505 Performance Turbo System For Jeep 4.0L Parts Photo 2
11-02-2011 06:28 AM
Tonycrd The only thing that would help for real is a turbo. Or NoS...LOL
11-01-2011 08:50 PM
geentj or fix a rough idle
11-01-2011 08:50 PM
geentj I have a intake and trottle body on my 2.5 and it seems that i have to clean my trottle body and run injector treatment atleast every three monthes to prevent a rough idle
09-30-2011 11:54 AM
jeepinmike The 4.0L TB will add some on the top end if anything. The 2.5 is flowing enough air through to really gain anything. The difference you feel in the low end is strickly due to the fact that the bore is large hence allowing more air in than a small TB at the same throttle plate position....it's more 'snappy' or responsive off idle. The PCM compensates for the extra air, so it is not an actual power gain.

Where the 4.0L TB really starts to help is when you have done some mods. My 95 YJ 2.5 had the 4.0L TB, 2.5 cat and cat back, MAP adjuster, Jacobs ignition, and a few other tweaks. It was quicker, but it was mostly at high RPM. It was quicker light to light than a co-workers bone stock renix YJ, and that was with 31's on mine.
09-30-2011 08:43 AM
geiman
Quote:
Originally Posted by Jerry Bransford View Post
Sorry to inform you that a throttle body does nothing when placed under the type of throttle body a TJ has. Spacers like that can help performance with the older TBI (Throttle Body Injection) style of throttle body with a fuel injector screwed into it, as well as with carburetors, but it won't help in the least when installed under a TJ's throttle body that has nothing but air passing through it.
x2; been there done that on my 2.5l. I'd chalk most of the improvements up to the placebo effect.
09-29-2011 07:39 PM
Jerry Bransford Sorry to inform you that a throttle body does nothing when placed under the type of throttle body a TJ has. Spacers like that can help performance with the older TBI (Throttle Body Injection) style of throttle body with a fuel injector screwed into it, as well as with carburetors, but it won't help in the least when installed under a TJ's throttle body that has nothing but air passing through it.
09-29-2011 07:35 PM
misweetrevenge i got a 4 banger because i drive mainly just around town and dont commute for work. there for the less-crappy mpg of the 4 banger is favorable and the lack of power is rarely a problem. i do drive over the hill once a week or so to visit freinds and could use a slight bit more torque so the 4.0 TB with a spacer and K&N filter is more helpful than the extra two cylinders.

it all depends on what you use it for. JMO
03-09-2011 10:26 AM
GOVT1911
Quote:
Originally Posted by rrich View Post
Why would anybody buy a Jeep with the toy 4 banger anyway? Don't they drive it first and see it has no power?

Same idea as people moving by an airport, then complaining about the planes.
\


Well, I paid $1200 for my 1998 Jeep with the "toy 4 banger" and 70,000 miles on it. That's MY "excuse", anyway!

I did the 4.0 TB swap, as well as enlarging the manifold and better exhaust. My butt-dyno says it has some improvement, but never actually dyno'd it. "Experts" say it's great/waste of money, depending on who you ask. I'm glad I did it, but that's my .02.
09-27-2010 11:09 AM
KBR97
Quote:
Originally Posted by Timmyk View Post
Well my friend maybe the people donít buy them. This vehicle was a gift to my girlfriend from her father. I understand there is no cure for displacement, how ever I thought this was an area you could ask questions and not expect to get ridiculed or belittled. I guess I was wrong. That is too bad.
Nobody meant any harm. You were given good points on both sides of the fence. We all like to ruffle feathers every now and then, lol.
09-27-2010 10:28 AM
Jerry Bransford Exactly where were you "ridiculed or belittled"?
09-27-2010 09:28 AM
Timmyk Well my friend maybe the people don’t buy them. This vehicle was a gift to my girlfriend from her father. I understand there is no cure for displacement, how ever I thought this was an area you could ask questions and not expect to get ridiculed or belittled. I guess I was wrong. That is too bad.
09-26-2010 02:17 PM
rrich Why would anybody buy a Jeep with the toy 4 banger anyway? Don't they drive it first and see it has no power?

Same idea as people moving by an airport, then complaining about the planes.
09-26-2010 01:17 PM
KBR97
Quote:
Originally Posted by Jerry Bransford View Post

The 2.5L isn't starved for more air, it is starved for more displacement.
So you cant replace 2 missing cylinders with TB spacers, intakes and bigger throttle bodies?? lol
09-26-2010 11:46 AM
Jerry Bransford A spacer won't do jack for the type of air-only throttle body the TJ uses. Spacers can do wonders when under a carburetor or the old no-longer used TBI (throttle body injection) systems that are "wet" because they have fuel passing through them but the TJ has only air passing through its throttle body.

And regardless of what 4bangerjp.com/ says about what they found with their dyno by using a 4.0L throttle body on the 2.5L engine, it's still pretty well agreed on that a 4.0 TB does nothing for the 2.5L engine. And one thing to know about a dyno... they are not (!) a precise device. You can run five different dyno tests on the same configuration and even if you try to get the results the same, you'll get five different results. Its error rate is greater than the dyno hp gains claimed by some.

The 2.5L isn't starved for more air, it is starved for more displacement.
09-26-2010 11:39 AM
Timmyk I have a 94yj with 4 pissed of gerbals in it. So if im getting it right, you all are saying that a 4.0 TB bolts right onto the 2.5 and will give me gerbals more food? and with a spacer say like a vortex or something same will help and someone who is not a master mechanic can do? Is there a photo log of the conversion anywhere?

Thanks
05-08-2009 09:36 AM
dos0711 4BangerJP.com dyno showed improvement. Depends on what source you use.
02-23-2009 07:52 PM
DontTellMeAboutCajun
Quote:
Originally Posted by Jerry Bransford View Post
I don't care what someone's butt-dyno is telling them who says it helped their performance. The Placebo Effect is a strong one that is hard to resist, that is for sure.

Well spoken Thanks for your input!
02-23-2009 07:46 PM
Jerry Bransford
Quote:
Originally Posted by DontTellMeAboutCajun View Post
Please, elaborate! How so?
Only that validated dyno tests... which should never be confused with the always overly optimistic butt-dyno... show no gain by doing that. In fact, Jp Magazine tried installing a 4.0L throttle body onto a 2.5L engine a year or two ago and they actually noticed a slight drop in performance. And I don't care what someone's butt-dyno is telling them who says it helped their performance. The Placebo Effect is a strong one that is hard to resist, that is for sure.
02-23-2009 07:41 PM
DontTellMeAboutCajun
Quote:
Originally Posted by Jerry Bransford View Post
Yes. If you are looking for an excellent way to waste your time and $$$, that is exactly what you need to do it with.
Please, elaborate! How so?
02-23-2009 06:16 PM
Jerry Bransford
Quote:
Originally Posted by DontTellMeAboutCajun View Post
Kinda feel dumb asking this, but I'd just like to be sure. For my 2.5 TJ, I'm gonna need a 4.0 TB from a TJ, correct?
Yes. If you are looking for an excellent way to waste your time and $$$, that is exactly what you need to do it with.
02-23-2009 05:53 PM
DontTellMeAboutCajun Kinda feel dumb asking this, but I'd just like to be sure. For my 2.5 TJ, I'm gonna need a 4.0 TB from a TJ, correct?
02-04-2009 12:34 AM
Triple88a
Quote:
Originally Posted by Jiffydarren View Post
I just stuck a K&N in mine... It helped.

Use your transmission right and you'll be fine.
^ one step forward, 2 steps backwards

Check how clean your intake pipe is in about a month and post pics and results.
02-04-2009 12:09 AM
Jiffydarren I just stuck a K&N in mine... It helped.

Use your transmission right and you'll be fine.
04-18-2008 09:27 PM
UNLIMITLESS My TB didnt come with IAC, TPS or MAP so I had to swap mine. The IAC housing is different. The hole inside is larger on the 4.0. I originally installed it by hitting the little tab with the grinder but I had a crazy idle. I also didnt have security Torx bits, but I borrowed a set to swap the IAC housing. Paid $28 shipped to my door. Im going to pull it off and port match it to the gasket.
03-15-2008 08:58 PM
Tinker
Quote:
Originally Posted by compshooter View Post
I had a different experience. It will not "bolt straight up". One little dohicky (official term) on the throttle bodies is different. There is a little tab on the dohicky that points downward and prevents putting a 4.0 TB on a 2.5 and vice versa. You must pull this dohicky off the 2.5 TB and put it on the 4.0 TB and then it bolts right up. As someone else said, make sure you get a new gasket before doing the swap though.

I did notice an improvement on the top end also. Good $50 mod.
I run into the same problem when I did mine 2 days ago, rather than remove the tamperproof screws I opted for a more...... um........ aggressive approach and just popped the tab off with a pair of pliers, and VIOLA'. I did notice a mild improvement in throttle response.
06-19-2007 07:59 PM
6DEVIL16
2 of a Kind

Quote:
Originally Posted by khenderson View Post
Anyone had any good/bad experiences with doing this little mod? Found a 4.0 TB at a junk yard, so I figured I'd give it a shot...could use a little more umph out of my little 4 banger.
No but I would love to know how that turned out, send me the results too. 6DEVIL16
05-05-2007 09:07 PM
4.0l sahara Ya i'm sure up to a 75hp shot would be fine.For a 20-25hp shot you shouldn't need new fuel injectors or a computer reprogram.For 20-25 a dry shoot is okay but when you get into the bigger shots a wet kit is better. Also be sure not to hit the rev limiter on the engien when the nitro is on.If this happens the nitrous can build up in the intake a then blow up and on some cars it can blow the intake off the engien.
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