Jeep throttle body...Too big?

[1995eternal]

Well I know this has been covered a bunch but I've been readin through the old threads about it and have a couple questions for those who are familiar with this mod. Im looking to get the quicker throttle response, which is why Im gonna do this mod, I already have a CIA, high flow cat, exhaust (in the mail). Im real interested in the jeep throttle body. I was previously a jeep guy so Im pretty familiar with those TB's. The Jeeps TB is 59mm wide at the opening and tapers down to 55mm at the bottom. I know this is much larger than my stock TB on my 420a. I know I can use the jeep TB but my question is if its too big? Which would cause loss of power in the lower RPM range. Basically I just want to make sure that the jeep TB won't rob all my low end power when I install it. Any tips or adivice would be great.... Thanks

 

[rstare]

The stock TB is 52mm, which is on the small end. This makes the Jeep TB a good mod, a lot of people open them up to 60mm.
2GNT.com - 60mm_Jeep_Throttle_Body

 

[1995eternal]

The stock TB is 52mm, which is on the small end. This makes the Jeep TB a good mod, a lot of people open them up to 60mm.
2GNT.com - 60mm_Jeep_Throttle_Body

Yea, I was thinking about getting a 60mm but then I read how that could be overkill for my n/a 420a. Just making sure the jeep throttle body would be worth it.... I also am interested in if boring the intake manifold would be worth doing at the same time. I can get a whole new intake manifold off ebay for like $50. That way I could take it to a machine shop and drop it in when I was ready. Does matching the intake manifold to the new throttle body really help?

 

[rstare]

60mm isn't really overkill, firstly.
Porting out the manifold is a great mod, as well. There's cheap Ebay options, but a lot of them take a lot of modifications to actually work. If I were you, I would have a shop port out the stock IM and match it to whatever size TB you decide on.

 

[1995eternal]

well im down to either getting a 55mm or the 60mm throttle body. The 55mm is a hundred less though. In the description for the 55mm it says something has been done to allow as much air as a 57mm. This car is my DD but I obviously want it to be fast. Would getting the 55mm and boring out my IM to match be enough for me to be happy. I dont want to end up getting the 60mm and notice loss in low end power. Which I really like having. So far I have an AEM CIA, hi-flow cat and a cat back system. I just installed the new exhaust the other day and I totally notice the RPM's climbing faster. So basically what I want to know from people with experience in this is if the 55mm will be enough to get the job done. Im not trying to go over bored on this car.

So been doing some more reading on the site. It seems that now I might want to go down the path of turboing my N/A. It seems if I keep it a N/A I could throuw a ton of money into the car and only see marginal gains. I want a car thats got some umph behind it and now after reading it seems the turbo is the best way to go. I would have posted this in the turbo section but I can yet, so sorry for that. Anyways if I plan on going turbo I should obviously go with the 60mm throttle body and match the intake manifold, or will I need a competly different IM if I go turbo. What Im wondering is can I throw on the 60mm TB and matched IM to my car before I turbo it. Or will that mess up my low end power. I already have some basic mods if that matter. Please I need some opinions on this, im new to this scene and learning as much as possible.

 

[rstare]

well im down to either getting a 55mm or the 60mm throttle body. The 55mm is a hundred less though. In the description for the 55mm it says something has been done to allow as much air as a 57mm. This car is my DD but I obviously want it to be fast. Would getting the 55mm and boring out my IM to match be enough for me to be happy. I dont want to end up getting the 60mm and notice loss in low end power. Which I really like having. So far I have an AEM CIA, hi-flow cat and a cat back system. I just installed the new exhaust the other day and I totally notice the RPM's climbing faster. So basically what I want to know from people with experience in this is if the 55mm will be enough to get the job done. Im not trying to go over bored on this car.

So been doing some more reading on the site. It seems that now I might want to go down the path of turboing my N/A. It seems if I keep it a N/A I could throuw a ton of money into the car and only see marginal gains. I want a car thats got some umph behind it and now after reading it seems the turbo is the best way to go. I would have posted this in the turbo section but I can yet, so sorry for that. Anyways if I plan on going turbo I should obviously go with the 60mm throttle body and match the intake manifold, or will I need a competly different IM if I go turbo. What Im wondering is can I throw on the 60mm TB and matched IM to my car before I turbo it. Or will that mess up my low end power. I already have some basic mods if that matter. Please I need some opinions on this, im new to this scene and learning as much as possible.

With a 55mm TB you won't see very big gains. However, A 60mm TB should provide noticeable gains. It's definately something you want to do if you're going turbo. It will be fine to do it before you're turbo, yes. I know quite a few people who are NA and running a 60mm.
Some other good mods would be a UDP and a lightened flywheel, both will help with low range RPM.

 

[1995eternal]

With a 55mm TB you won't see very big gains. However, A 60mm TB should provide noticeable gains. It's definately something you want to do if you're going turbo. It will be fine to do it before you're turbo, yes. I know quite a few people who are NA and running a 60mm.
Some other good mods would be a UDP and a lightened flywheel, both will help with low range RPM.

alrighty thanks for the clairifaction. I heard running a 60mm TB on a N/A could hurt low end. BUT if it doesnt im sure going to just get that one. I've been eye ballin the AF/X UDP and it sounds sweet. Could I keep that on if I go turbo later on.

 

[rstare]

alrighty thanks for the clairifaction. I heard running a 60mm TB on a N/A could hurt low end. BUT if it doesnt im sure going to just get that one. I've been eye ballin the AF/X UDP and it sounds sweet. Could I keep that on if I go turbo later on.

It could hurt it, but I wouldn't be too worried about it.
Yes, the UDP is a great mod, turbo, or not.

 

[lilredeclipse]

thanks to this post too!

 

[afoster98GSX]

I think it would ne an ok set up.

 

[greengoblin2011]

Ok, im going to play the retard role here. Just joined the forum and have seen alot about this tb mod. So here is my question. What year(s) jeep tb works on a 95 420a, and what mods if any are needed to adapt it to a stock intake manifold? Sorry for the dumb question, just never heard of this till now, and may look to do it. Thanks guys

 

[CODE4]

The stock TB is 52mm, which is on the small end. This makes the Jeep TB a good mod, a lot of people open them up to 60mm.
2GNT.com - 60mm_Jeep_Throttle_Body

Greengoblin, did you read the whole thread? A link was provided discussing this modification.

 

[Slo2gen]

I think the biggest that someone has run so far and actually could drive it is 75mm, I think there was an 80mm that was used but the drivability on it sucked balls so it was taken off.

 

[dsmjunk]

i dont know much about this stuff but my friend used a eclipse ported auto throttle body and wondered why someone would use an auto tb on a manual

 

[lee7]

I have a question about this mod. I am currently running on a 1/4 mile circle track at my local speedway, I decided last week to forgo this mod with out upgrading my fuel injectors or ECU. The exhaust is a stock manifold that I machined out to 2 1/2" id because the track doesn't allow headers. The car never comes out of second gear and I run about 37mph through the corners and hit about 62mph on the straights. After this Fridays race I came off the track and did my usual inspection to find that my entire exhaust manifold and 11" of pipe were glowing orange. I think she's running a little lean 8( so before I wreck anything, provided I haven’t already, do I need larger fuel injectors to go with this mod?

 

[genegoesfast]

You need a method with which to tune your mods. I doubt you're in need of bigger fuel injectors yet BUT with something like ecmlink you'd be able to tell at what percentage your injectors are running and make adjustments in the tune to utilize the additional airflow and throttle response.

 

[bullettdsm]

Well, neither of you guys are making sense to me

If you forgo something, you do without. Therefore, when you forgo this mod, you are doing without it. So what is your set-up?

And ECMLink for 420a's? Do tell......

MB

 

[Shake_Zulla]

You need a method with which to tune your car. I doubt you're in need of bigger fuel injectors yet BUT with something like megasquirt you'd be able to tell at what percentage your injectors are running and make adjustments in the tune to utilize the additional airflow and throttle response.

Fixed

Well, neither of you guys are making sense to me

If you forgo something, you do without. Therefore, when you forgo this mod, you are doing without it. So what is your set-up?

And ECMLink for 420a's? Do tell......

MB

Maybe he "forgoed" the whole throttle body? Joking aside is running lean the problem? Don't most n/a's lean out their fuel curve once they are able to tune? Correct me if I'm wrong here.

Oh and to the guy who asked why someone would use an auto trans TB over a manual TB... uhh they are the same TB, someone probably ported the auto one. ALMOST everything is the same on a manual and auto except the trans (and a very few other parts).

 

[jackblack65]

I have a question about this mod. I am currently running on a 1/4 mile circle track at my local speedway, I decided last week to forgo this mod with out upgrading my fuel injectors or ECU. The exhaust is a stock manifold that I machined out to 2 1/2" id because the track doesn't allow headers. The car never comes out of second gear and I run about 37mph through the corners and hit about 62mph on the straights. After this Fridays race I came off the track and did my usual inspection to find that my entire exhaust manifold and 11" of pipe were glowing orange. I think she's running a little lean 8( so before I wreck anything, provided I haven't already, do I need larger fuel injectors to go with this mod?

Well a glowing exhaust means more fuel is getting burned not that it is necessarily running any leaner.
Check your plugs for their color, you want a nice medium brown.
It has been a few decades since I tuned but not much has actually changed
Air fuel mixture is adjusted by a computer instead of a screw so however you are tuning you need the ability to enrich [more fuel] darker plug color.
You will actually need a variety of airhorns [TB] to really dial in the track conditions.
Find a place you can lay down a 1/8 mile at WOT repetitively without hassles.
Pull the spark plugs after each pass and check color. Use a stopwatch to compare times and log them with the ambient air temp,humidity and intake setup used.
Don't be surprised if that 55 outperforms the 60 on cold days.
The taper in the horn has some effect as well,so don't just "open up" a 55 to 60-75 without addressing the venturi effect it may cause.
25 mm per inch so 2.5 inch exhaust would be about 63 mm max
Good luck on race day!
Hint:
If the plugs are grey and/or have white flecks on them you need to pull the head and check for piston and valve damage!

 

[Ricardo18]

This seems like a very old thread, but I thought I'd add some additional info for future reference.

I did the Jeep throtte body mod along with port matching on a previous car ('99 avenger). Did it hurt low end? It might have, but it was not noticeable. The reason for this was the throttle response was increased. Because of a map sensor, it senses a greater difference in pressure over a shorter period of time, so I'd liken this mod to a short shifter. Acceleration did seem to flatten out as it got to a certain point. That is, 90% of throttle was the same as 100% of throtttle.

A negative side effect is that it leans out the A/F mixture. Due to the difference in pressure(higher with a larger tb/port job) at a given tps value, and the computer not knowing you upgraded tb size, you may lean out when going past a certain rpm.

I had a stock exhaust at this time, so I'm not sure if that would have had an effect on my results, but it is a mod I would consider doing again. The reason being I have a header, high flow cat, and catback this time. I'd consider it a complimentary mod on the intake side to compensate for higher flow on the exhaust side.

One additional note,

The taper in the horn has some effect as well,so don't just "open up" a 55 to 60-75 without addressing the venturi effect it may cause.
25 mm per inch so 2.5 inch exhaust would be about 63 mm max

Wouldn't this vary with what type of exhaust modifications are done? I'm quite curious also. Is there a database or some sort of data collection that I could use for reference? With exhaust gas temperatures being much higher than intake temps and the different gas compositions, I wanted to see how much backpressure is desired with varying exhaust and intake sizes and restrictions (eg cat.), turbo vs n/t etc.

 

[jackblack65]

This seems like a very old thread, but I thought I'd add some additional info for future reference.

I did the Jeep throtte body mod along with port matching on a previous car ('99 avenger). Did it hurt low end? It might have, but it was not noticeable. The reason for this was the throttle response was increased. Because of a map sensor, it senses a greater difference in pressure over a shorter period of time, so I'd liken this mod to a short shifter. Acceleration did seem to flatten out as it got to a certain point. That is, 90% of throttle was the same as 100% of throtttle.

A negative side effect is that it leans out the A/F mixture. Due to the difference in pressure(higher with a larger tb/port job) at a given tps value, and the computer not knowing you upgraded tb size, you may lean out when going past a certain rpm.

I had a stock exhaust at this time, so I'm not sure if that would have had an effect on my results, but it is a mod I would consider doing again. The reason being I have a header, high flow cat, and catback this time. I'd consider it a complimentary mod on the intake side to compensate for higher flow on the exhaust side.

One additional note,


Wouldn't this vary with what type of exhaust modifications are done? I'm quite curious also. Is there a database or some sort of data collection that I could use for reference? With exhaust gas temperatures being much higher than intake temps and the different gas compositions, I wanted to see how much backpressure is desired with varying exhaust and intake sizes and restrictions (eg cat.), turbo vs n/t etc.

Yes that is how I calculated the maximum diameter by assuming the exhaust would be the smallest constriction in air flow.This is not always the restriction however as
the intake itself may be the bottleneck.
As for the flow into the horn you need to understand how to tailor the shape of the venturi to put the torque where you want it.
You need higher velocity flow for top end power but you sacrifice low end to get it.
This is why we have more valves on today's motors,it is a compromise to have the best of both.
Look at this page to get a better understanding of whats going on inside the chamber.
Venturi Tube Simulation
Your "database" is your clipboard of your recorded times to conditions as observed
when you do your trials.You should also note the barometric pressure as well.

 

[Ricardo18]

Thanks for the response Jack . I have to download a plug-in for the interface, but I really appreciate the link. Ill check it out and will respond with any questions I may have.