Will I really get performance gains from a 4.0tb? - JeepForum.com

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post #1 of 28 Old 08-06-2011, 02:21 PM Thread Starter
Getdirtyoffroad
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Will I really get performance gains from a 4.0tb?

And how much? I have a 95 YJ 2.5L. Is there something online that I can read or watch to show install?

Thanks...


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post #2 of 28 Old 08-06-2011, 02:27 PM
TheNewbie
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You don't really need a video to learn how to install it. Just unplug the wiring harness plugs and take out the 4 bolts and remove the TB. Then take the 2 sensors off (the IAC and TPS) and put them on your 4.0 TB. Then bolt it on and plug the wires back in.

Oh I forgot about the throttle cable too. Jut pop it off and on.

I did notice more power on the highway at higher speeds. It helps in the higher RPM's. And I can make it further on uphill stretches without having to downshift. It is easier to keep up with highway speed trafic. But it's not going to make that much of a difference. Just enough to notice. I still struggle on the highway. Just not as much. I used to go 55-60 to keep from having to floow it and downshift ever minute or so. Now I go 65-70. So it does help a little bit. I still ahve to really fight it to keep up with 75 MPH traffic. And passing is tricky because there is still not much room for acceleration. It just stops the deceleration from being so bad...

In town and off road (lower RPM situations) there was no difference that I could notice. Just on the highway.

1995 YJ 2.5 - 4 RC lift - 1" MML - 33's - flat fenders front - TJ flares rear -Raptor lined exterior - Herc'd interior - DIY front bumper & winch plate - 136 amp alternator mod - 4.0 TB swap


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post #3 of 28 Old 08-06-2011, 03:46 PM
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^Your bigger tires offset the speedometer, unless you put a new speedo gear in. At 65mph you should be reading something like 55-56mph on your speedometer. At 65 on your speedometer you're really doing 76mph. And at 75 on your speedometer, your flux capacitor will discharge sending you into another time zone.

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post #4 of 28 Old 08-06-2011, 04:31 PM
TheNewbie
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Quote:
Originally Posted by Xpress View Post
^Your bigger tires offset the speedometer, unless you put a new speedo gear in. At 65mph you should be reading something like 55-56mph on your speedometer. At 65 on your speedometer you're really doing 76mph. And at 75 on your speedometer, your flux capacitor will discharge sending you into another time zone.
I use a GPS speedometer most of the time if I'm on the highway. It also helps offset any disturbance by the flux capacator.

I've had it over 100 MPH before I realized how much the speedometer was off. It was NOT a smooth ride and did NOT feel safe in any way. Now I stick to about 10 under the speed limit on the highway unless I'm passing (or trying to pass).

1995 YJ 2.5 - 4 RC lift - 1" MML - 33's - flat fenders front - TJ flares rear -Raptor lined exterior - Herc'd interior - DIY front bumper & winch plate - 136 amp alternator mod - 4.0 TB swap


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post #5 of 28 Old 08-06-2011, 06:10 PM Thread Starter
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Speedo corrected... Stay on topic people ...Throttle Body upgrade...

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post #6 of 28 Old 08-06-2011, 08:14 PM
sbsg2005
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Don't forget the 4.0 throttle body is a bigger bore so unless you match the bore in the intake to the bore in the throttle body you will likely see no gains. There is a forum that is dedicated to 4 banger Jeeps and I did alot of reading on this swap and some felt gains and some didn't. I did but it may a been an accumulation of gains from the header, full exhaust, injectors, throttle body spacer, throttle body, and adjustable fuel pressure regulator. But I got everything for free or close to it. The gains I have seen wouldn't warrant me to go spend the cash on all the crap if I had to do it again and had to pay for items above.
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post #7 of 28 Old 08-07-2011, 07:37 AM
hesserdude07
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when i had my 2.5, i noticed positive gains from the 4.0 TB. But as stated above, i also had injectors, pace setter header and full exhaust and a intake. I always had plenty of power to turn my 35s on stock 4.10 gears, and could still do 70-75 on the highway without much problem... i only swapped motors after i blew my 2.5 up.

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post #8 of 28 Old 08-08-2011, 11:14 AM
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Quote:
Originally Posted by sbsg2005 View Post
Don't forget the 4.0 throttle body is a bigger bore so unless you match the bore in the intake to the bore in the throttle body you will likely see no gains.
Hmm, I thought that the opening in the 2.5 intake was bigger than the 2.5's TB opening. So swapping a 4.0 TB on withh just match the size...

I could be wrong. Btu I never bored anything. I also never measured. Maybe I should.

1995 YJ 2.5 - 4 RC lift - 1" MML - 33's - flat fenders front - TJ flares rear -Raptor lined exterior - Herc'd interior - DIY front bumper & winch plate - 136 amp alternator mod - 4.0 TB swap


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post #9 of 28 Old 08-08-2011, 11:37 AM
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I didn't notice much, to be honest.
I am able to do machine work at my house, so I purchased the 4.0 throttle body and machined it to 60mm straight through. Throttle response seems to be a bit quicker and a bit more sensitive, but I didn't get any noticeable power gain. I don't know if I'd spend a lot of money on the conversion, and because I can do the machine work it was only 10 or 15 bucks for a used throttle body and about an hour's worth of work total to try it out.
Another area that one hears about is the throttle body spacer. I have a piece of aluminum chucked up in the lathe right now, but only making one out of curiosity. I really don't expect much from it, though.
I think we get sucked into all the "snake oil" because of some silly sense of need from a lack of power from a 4 cylinder. C'mon folks, in the end it is a 4 cylinder and it is what it is.
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post #10 of 28 Old 08-08-2011, 11:51 AM
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Quote:
Originally Posted by nzpete View Post
I didn't notice much, to be honest.
I am able to do machine work at my house, so I purchased the 4.0 throttle body and machined it to 60mm straight through. Throttle response seems to be a bit quicker and a bit more sensitive, but I didn't get any noticeable power gain. I don't know if I'd spend a lot of money on the conversion, and because I can do the machine work it was only 10 or 15 bucks for a used throttle body and about an hour's worth of work total to try it out.
Another area that one hears about is the throttle body spacer. I have a piece of aluminum chucked up in the lathe right now, but only making one out of curiosity. I really don't expect much from it, though.
I think we get sucked into all the "snake oil" because of some silly sense of need from a lack of power from a 4 cylinder. C'mon folks, in the end it is a 4 cylinder and it is what it is.
The spacer can't do anything on your 95 model. It's MPI. So the gas and air don't mix in the TB so the spacer won't do squat. On a TBI setup it gives mroe time for the gas and air to mix for a more uniform mixture. But with your setup it will only give the air more time to travel by itself after the TB. Which is itself cannot really do anything. Some people claim that the spacers with the spiral in them allow mroe air to get in because of chanign the pressure or somethign like that. But I wouldn't bet on it.

If you have a TBI system though, the spacer MAY help.

1995 YJ 2.5 - 4 RC lift - 1" MML - 33's - flat fenders front - TJ flares rear -Raptor lined exterior - Herc'd interior - DIY front bumper & winch plate - 136 amp alternator mod - 4.0 TB swap


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post #11 of 28 Old 08-08-2011, 11:57 AM
nzpete
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Quote:
Originally Posted by TheNewbie View Post
The spacer can't do anything on your 95 model. It's MPI. So the gas and air don't mix in the TB so the spacer won't do squat. On a TBI setup it gives mroe time for the gas and air to mix for a more uniform mixture. But with your setup it will only give the air more time to travel by itself after the TB. Which is itself cannot really do anything. Some people claim that the spacers with the spiral in them allow mroe air to get in because of chanign the pressure or somethign like that. But I wouldn't bet on it.

If you have a TBI system though, the spacer MAY help.
Yes, but the claims are out there that it will.
My point is that most of this is "snake oil", and the only reason I don't mind trying is because I can make the components myself. I lose a little time, but not a whole lot of money, and this is a hobby, right? )
If I actually had to pay the money that some folks do for the throttle body and the spacer, I would pass.
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post #12 of 28 Old 08-08-2011, 12:11 PM
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In my experienc on my 02 tj with the 2.5. I added a 4.0 tb, tb spacer and intake. I got an 8 hp gain on a mustang dyno. The average is between 6-8 depending on how healthy your motor is to begin with. The best result was when using the the tb spacer, 4.0 tb and intake, they worked together in a system. Most times the spacer adds nothing, but with this application, the spacer was good for 2hp when added with the tb and intake on the jeep 2.5. 8 hp isn't alot, but on the puney 2.5 it makes a noticable difference in throttle response. With a catback and header you can get 10-12 total hp bump. It's a chunk of money for only 12 hp, but on the 2.5 you need every hp you can get.

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post #13 of 28 Old 08-08-2011, 12:12 PM
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Originally Posted by nzpete View Post
Yes, but the claims are out there that it will.
My point is that most of this is "snake oil", and the only reason I don't mind trying is because I can make the components myself. I lose a little time, but not a whole lot of money, and this is a hobby, right? )
If I actually had to pay the money that some folks do for the throttle body and the spacer, I would pass.
I couldn't agree more.

1995 YJ 2.5 - 4 RC lift - 1" MML - 33's - flat fenders front - TJ flares rear -Raptor lined exterior - Herc'd interior - DIY front bumper & winch plate - 136 amp alternator mod - 4.0 TB swap


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post #14 of 28 Old 08-08-2011, 12:42 PM
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Quote:
Originally Posted by nzpete View Post
Yes, but the claims are out there that it will.
My point is that most of this is "snake oil", and the only reason I don't mind trying is because I can make the components myself. I lose a little time, but not a whole lot of money, and this is a hobby, right? )
If I actually had to pay the money that some folks do for the throttle body and the spacer, I would pass.
Honestly it's not going to work on a system that uses multi-port injection.

Throttle body spacers only work when the fuel and air can be mixed directly inside of the throttle body spacer chamber, so that is why you basically won't see gains with your setup, because all it is going to do is stir the air a bit, which then is dissipated by the bends inside of the intake.

All about that unibody life.
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post #15 of 28 Old 08-08-2011, 03:13 PM Thread Starter
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Think I'll hit the junk yards and look for a throttle body...cheap clean it up and stick it in...see what happens...already have the spacer on the stock tb. Thanks everyone...won't cost me but a couple of bucks for this upgrade, what the heck!

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