2.5L throttle body upgrades?

[Shorty]

I was recently given a 4.0L throttle body ('94ish) and was told it would "wake up" my little DD 2.5L (1994,5spd, 2WD)

Does anyone have practical experience with the swap-- done it, seen it, read about it? I've searched a bit a don't see much on here (maybe I just suck at the search...)

 

[old_man]

I build a performance 2.5L. The larger throttle body is minimally effective. Just like on the 4.oL, it improves throttle response. You can do that by moving the mounting point of the throttle cable closer to the pivot. In order to get it to make a difference, you need to make the engine breath more air and actually use it. See if you can score a Mopar Purple cam for the engine. It makes quite a bit of difference and unlike the 4.0L, you can change the cam without pulling the head.

I did the purple cam, oversized valves, Clifford header and 2.5" exhaust all the way back. The difference was significant but still no where close to the output of a 4.0L. I did enjoy the great gas mileage though.

 

[Shorty]

I build a performance 2.5L. I was hoping you'd see this... The larger throttle body is minimally effective.definitely wasn't expecting NOx kind of results:roll: Just like on the 4.oL, it improves throttle response. You can do that by moving the mounting point of the throttle cable closer to the pivot.got any details on this? it's the first time I've heard of it. In order to get it to make a difference, you need to make the engine breath more air and actually use it. See if you can score a Mopar Purple cam for the engine.This is what me initial feeling was as well-- it seems to run out of air in the 4000rpm range, but it fees more like a function of short duration and low lift than restricted throttle opening. It makes quite a bit of difference and unlike the 4.0L, you can change the cam without pulling the head.

I did the purple cam, oversized valves, Clifford header and 2.5" exhaust all the way back. The difference was significant but still no where close to the output of a 4.0L. I did enjoy the great gas mileage though.

I'm still on the fence as changing a good TB for another, but If I decide to take the plunge, do you know if I want the IAC from the 4.0L throttle body or the IAC from the 2.5L if I do it? I saw they were different part numbers, but haven't looked into what is the actual difference.

any reading that anyone can provide is welcomed-- just like to know what to expect before I dig into a well-running motor for no reason....

 

[old_man]

I don't remember about the tps. There is a yahoo group out there called 4banger IIRC where you can score a ton of info.

Think about boring the throttle body. At low throttle, all you would have to do is add more throttle to compensate for the smaller bore. Where it really comes into play is when you hit WOT and can't open it any more.

As for throttle response, given a movement of the accelerator, the cable moves a fixed distance. That movement works on the bellcrank on the throttle plate shaft. If you have a shorter bellcrank and have the same movement on the cable, the throttle opens further giving you what feels like better throttle response, but is really just the fact that the throttle plate is opening more for a given movement of the accelerator. So if that is what you want, bore a new hole on the bellcrank and move the little piece with the ball on it closer to the centerline of the throttle shaft.