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Unread 09-15-2003, 01:48 PM   #1
CanukYJ
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Throttle Body Conversion important Q

Sorry, I'm sure this has been asked a million times before, and I may sound stupid for asking but:

1) In a throttle body conv (2.5l to 4.0l) does it add horsepower? Increase MPG? Why do people do it?

2) Can ANY year of 4.0l TB be put on a 92' jeep YJ 2.5l? Ex- Can I got to the junkers and yank a 4.0l TB from a 95 cherokee? Or does it HAVE to be a TJ? (same engines, no?).

Sorry if these are painfully obvious questions, just want to cover my ground before spending money on a TB for no reason.

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Unread 09-15-2003, 02:23 PM   #2
LoOpY
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A little research would yeild all your answers. Google is your friend. But since im bored:

Any 92 or newer TB, from a YJ or XJ will work.

I did it because my daily driver does about 200 miles of highway a week, and I always am looking for ways to increase power and fuel economy.

Ive had my 40TB on for 3 days now, and this is what Ive found:
-Low end torque get a huge boost. Your 0-40 range becomes significantly more powerful. Upper end doesnt gain a whole lot, but im still testing that. Seems to help me maintain 70mph uphill and into wind, my topend appears to be around 78 now (without wind assistance or hinderance)
-Shifting is smoother. Starting from a dead stop, I dont bog down anymore, and my shifts are smoother, because the engine can breathe easier and the RPMs dont drop off as quickly.
-Fuel economy is the big thing Ive still gotta watch. Before, when my gas gauge read 1/2, i usually had 120mi on the tripmeter or so. This is my first tank with the new TB, and im showing 140mi. Coincidence? possibly, Ill let you know.

But after doing this mod, I can say its the best 50 bucks Ive sunk into my Jeep. However, keep in mind that all this is on a vehicle running 33s, with a flex fan, headers, free flow exhaust, and a new motor (aka good compression) so your results could vary
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Unread 09-15-2003, 02:36 PM   #3
CanukYJ
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Ok as long as it's worth the time installing it, I'll check the junkers in town, anyone have an horror stories? Also what about TB spacers? Are they really worth the 70$??
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Unread 09-15-2003, 03:02 PM   #4
TellyDSP
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TB swap is a fairly effective cheap mod. It, along with a few other things gave me about 2-3 more MPG. As far as the spacer, they are ok, go with the smooth bore, it's supposed to be a better improvement. Just make sure to swap all the sensors. You basically want to fins a 4.o TB with the 4 bolt pattern.

This might help...Write-up
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n00bs bashing n00bs, it's a pitifull thing.
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Unread 09-15-2003, 03:16 PM   #5
CanukYJ
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Thanks for the link, read through it and it answers some questions. Does this "whistle" effect happen alot or is this a result of the TB spacer?
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Unread 09-15-2003, 03:50 PM   #6
TellyDSP
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As far as I know, the whistle is a result of the helix, you do get used to it after a while though. But like I said before, everyone says the smooth bore is better for you anyways.
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Originally Posted by Jeeples
n00bs bashing n00bs, it's a pitifull thing.
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Unread 09-15-2003, 04:04 PM   #7
Ramblin
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Just did a 2.5 to 4.0 conversion over the weekend. Overall feel seems like it brought up the power a bit, but haven't really given it the workout yet.

I have heard different views about the spacer and whether it really helps or not, and also different views on smooth or ripple spacer bore.

Anyone know how a spacer is supposed to help? With MPI that is.
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Unread 09-15-2003, 04:13 PM   #8
LoOpY
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Ill sell my TBS for 20 bucks
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Unread 09-15-2003, 04:15 PM   #9
LoOpY
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Quote:
Originally Posted by Ramblin
Anyone know how a spacer is supposed to help? With MPI that is.
It doesnt. sure the effect of swirling air is supposed to do some magical things. But on PFI, bah! And dont get me started on the concept of the smooth bore on PFI... TBI, I could see how it would help, a little.
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Unread 09-15-2003, 04:30 PM   #10
CanukYJ
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Thanks for the info guys, I'll go dig in the cherokees at the junkers this weekend and see what I can find, I'm gonna be buying it from a junker where I'll strip it out myself, any idea of an avg price range I'll be looking at (that way I'll be able to tell if I'm getting ripped off".
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Unread 09-15-2003, 06:56 PM   #11
Shinner
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Quote:
Originally Posted by TellyDSP
Just make sure to swap all the sensors.
Thought you were supposed to reuse the 2.5 sensors? No? This mod is on my list hopefully in the next few weeks and I'd like to be sure on what I need to do.
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Unread 09-15-2003, 07:05 PM   #12
Jay-P
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Quote:
Originally Posted by Shinner
Thought you were supposed to reuse the 2.5 sensors? No? This mod is on my list hopefully in the next few weeks and I'd like to be sure on what I need to do.
Yep thats what he means. Swap all your sensors off the 2.5 TB onto the 4.0 TB.
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Unread 09-15-2003, 07:42 PM   #13
TellyDSP
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The tricky part of the swap is that the sensors, at least the AIS, are held on with tamper proof torx. I honestly only changed one sensor because the other is held on with a tamper proof torx, which i dont have. When I start the engine, it idles high for about 20 secs then evens out. I have to get ahold of a tamper proof torx eventually, but you are supposed to change all sensors.
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Quote:
Originally Posted by Jeeples
n00bs bashing n00bs, it's a pitifull thing.
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Unread 09-15-2003, 07:47 PM   #14
Shinner
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Quote:
Originally Posted by Jay-P
Yep thats what he means. Swap all your sensors off the 2.5 TB onto the 4.0 TB.
Doh! I misunderstood...sorry ya'll!
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Unread 09-15-2003, 08:01 PM   #15
CanukYJ
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About prices at the scrapers though, let's say in Canadian funds, if I pay 100$ (approx 75$ american) am I being ripped? Is 30$ considered expensive?? Just wondering because the scrappers in town here are real con artists, and if they say a price that is actually REASONABLE I wanna be able to take it rather than piss em off hehe.
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