Topic: 50mm tbi install.

[chardrc]

as some of you may remember Sharpxmen bored out the lower half of a 2.5l tbi unit. after receiving the throttle body and spacer 2 months ago to test I've final gotten around to installing it.

I've been a little gun shy while dissembling the tbi after breaking bolts replacing the tps on our 1990xj 2 weeks ago. haven't broken any bolts yet (1 more to come off letting it soak a bit longer in penetrating fluid). have to wait for a new gasket to arrive at the parts store tomorrow morning to start assembly. for the initial stage I'm just going to install the larger tb then latter on ill install the spacer. i will have to bore out the manifold as it is 46mm (stock tb  is 44), but haven't decide if I'm going to bore now or latter. in addition the diameter at the bottom of the upper-half is smaller than that of the top of the stock lower unit. I also need to make some spacers for the vacuum line metal harness before i can install the spacer.

here are the pics
the upper fuel half of the tb



manifold


new lower by old upper


Sharpxmen's handy work


will upload more pictures upon completion..

looks like my tb has been off before as one of the studs was replaced by a bolt which reviled why they have studs as it is abit of a pain to get the bolt fully undone without trapping your socket.

[sharpxmen]

can't wait to hear if and how it works.

one thought - you should put the spacer in, would help with the flow around the butterfly  as it would keep it further away from the manifold which is smaller. you should be able to use 4 bolts for testing.

[chardrc]

thats a good thought... now ill have to order another gasket 

[Jeffy]

thats a good thought... now ill have to order another gasket 

If you don't have the time make one from some cardboard.  Not the corrugated kind.  Use the other gasket as a pattern.

[grumpygy]

If you don't have the time make one from some cardboard.  Not the corrugated kind.  Use the other gasket as a pattern.

File folder works great.

[sharpxmen]

I can guarantee you silicone or RTV will be just fine between the spacer and the t/b, they were both machined so you would need a thin film applied with your finger and will be sealed.

[chardrc]

I ended up just installing the larger tb without the spacer for now (ran out of time since I had to help change shackles on a cj7 and repair a leaky t-case cover). I actually have real gasket material now since I needed a new seal for between the lower and upper half of the tb and to get a new one you have to get the $50 kit with a new fpr and 4 different tb to manifold gaskets (generic set for all vehicles with that style of tbi).

after attaching the tps, and iac / wide open throttle switch bracket i found that the throttle spring was installed on the wrong notch and prevented the throttle from going wide open so i got to take everything back off and pull the shaft out a bit to fix that. the new shaft has a slightly different end to it that has a few different cable attachment  options which made the finger throttle attachment easier. but i did notice the new shaft has more side to side play than my old one. also the new tb had an interference issue with the egr valve when sliding it on the studs so I had to grind the housing  a bit to fit around the massive egr valve.  

random pics of old tb.



As for the results. there is a noticeable difference. only negative right now is the jeep is idling a hair above 1k, going to adjust the tps when it cools down to hopefully fix that. jeep seems to be more responsive and run smoother and pulls allot better from ~3500 through 4500 RPM. will now have to be more pedal conscious off-road to make sure i don't over-rev it. some of the smoother running could be from cleaning out the vacuum lines going out of the tb as they had some built up junk in them.

edit: doesn't gas eat away at the rtv over time?

[sharpxmen]

cool stuff man - happy to hear it works.

Gas won't get to the rtv as it is pressed between the body and spacer.

for the high idle, you might need to adjust the control arm and possibly lower the adjusting screw for the butterfly 1/4 to 1/2 turn (but make sure it doesn't bind (this is since the t/b diameter is larger so whatever the idle control was holding at min before would allow more air into the intake).

should get better response if you match the intake to the spacer too.

[chardrc]

we adjusted the tps and got it to idle just below 1k which seems to be normal for this jeep. I was thinking that i may have to adjust the bolt at the end of the idle air controller but it seems to still be-able to retract enough to idle low and still starts with the arm fully out (just revs a little more at initial start up when arm is fully extended but its quick to throttle it back. ) that stop screw on the tb itself usually never comes into play with the idle control motor but i will check. plate is about totally closed at  the point where it stops so shouldn't have to move (would be a real pain to get to when its installed with the aic and its bracket in the way. I'm going to drive around with it is for a while and then find a weekend to bore the intake and install the spacer.

[sharpxmen]

we adjusted the tps and got it to idle just below 1k which seems to be normal for this jeep. I was thinking that i may have to adjust the bolt at the end of the idle air controller but it seems to still be-able to retract enough to idle low and still starts with the arm fully out (just revs a little more at initial start up when arm is fully extended but its quick to throttle it back. ) that stop screw on the tb itself usually never comes into play with the idle control motor but i will check. plate is about totally closed at  the point where it stops so shouldn't have to move (would be a real pain to get to when its installed with the aic and its bracket in the way. I'm going to drive around with it is for a while and then find a weekend to bore the intake and install the spacer.

if the idle control motor keeps the lever off the adjusting screw in the t/b then there is no need to adjust this one, you might still need to lower the idle control motor to get the idle right but i don't really have much insight into that.

[cvdenson]

Any updates?  I'm really interested in doing this if it works out for you.

[chardrc]

still running good. idle is still normally just a bit over 1k... if you start it up when its fully warmed up it will drop below 1k at its old idle point but then eventually goes back up after driving for a while. I think its near bottoming out or is bottoming out the idle control motor and the screw needs to be turned in but they used some thread lock stuff on it and you are supposed to "heat with a soldering gun" to loosen it up to be able to adjust it without breaking it... but im not too worried about that right now. more worried about the sub-par cooling system and varying clutch pedal.

made a real nice improvement on the highway. with old tb that last 10% of the gas pedal made no real difference but with the new one there seems to be a difference right up to the floor board also at 3/4 throttle allot more than before and using 5th gear more often (could be that bent portion on the original tb plate blocking air when its wide open and near wide open.

I got 17mpg last tank (up form 13-15 but with more highway than before). depending on weather and how much i drive today i should be filling up Tuesday to get a second sample for averaging out the millage.

would definitely suggest this mod to any tbi user. still haven't messed with the spacer or matching the manifold. 

[cvdenson]

still running good. idle is still normally just a bit over 1k... if you start it up when its fully warmed up it will drop below 1k at its old idle point but then eventually goes back up after driving for a while. I think its near bottoming out or is bottoming out the idle control motor and the screw needs to be turned in but they used some thread lock stuff on it and you are supposed to "heat with a soldering gun" to loosen it up to be able to adjust it without breaking it... but im not too worried about that right now. more worried about the sub-par cooling system and varying clutch pedal.

made a real nice improvement on the highway. with old tb that last 10% of the gas pedal made no real difference but with the new one there seems to be a difference right up to the floor board also at 3/4 throttle allot more than before and using 5th gear more often (could be that bent portion on the original tb plate blocking air when its wide open and near wide open.

I got 17mpg last tank (up form 13-15 but with more highway than before). depending on weather and how much i drive today i should be filling up Tuesday to get a second sample for averaging out the millage.

would definitely suggest this mod to any tbi user. still haven't messed with the spacer or matching the manifold. 

Nice update...Did you end up using your old injector or opt for a bigger one?  I just rebuilt my 2.5 and the TB and am just getting it broke in at ~3000 miles.  I was getting 12-13mpg but the last few tanks have averaged 16mpg.  I got rid of the A/C, don't have power steering, so I'm only driving the alternator.  I wanted a simple, reliable setup for when I'm out on the trails.

[chardrc]

i kept the old injector. didn't touch the upper-half fuel part other than to clean it up a little.

[barrettsyj]

Got An extra intake and tbi laying around so I am def going to do this.