Topic: hi flow TB + extra fuel pressure??

[herman]

hello guys,

just signed in but here's my first question: I read there are a lot of people here with 4.0 TB, etc.;
couple of weeks ago I ordered a hi flow throttle body, written in the advertisement was that it's highly recommended to buy also an adjustable fuel pressure regulator. Ok so I did.
Knowing these parts are actually made for a 4.0 I'm wondering if this extra fuel pressure is really needed on a 2.5 engine?
For the moment I just installed the TB and the helix spacer, putted some silicone between and waiting now till the silicon is dry enough to go for a test. meanwhile I guess this extra fuel pressure is not needed, any experience someone?

Herman

[FourbangerYJ]

For me I did not add a adjustable fuel pressure regulator. I have been running the 4.0 for a number of years with no problems. Looking at the 62mm thread there is no mention there either needing one.

[Jeffy]

I have a 4.0L TB with a Helix TBS and 19# design III Injectors.  The most expensive part was the TBS at $70.  I have not futxed with teh fuel pressure any.  Although, you can get teh same effect as larger injectors by bumping up the pressure.  Only problem with that is that you don't really know how much it's gone up.  You would really want a wide band O2 sensor to make sure you're giving it the right ratio of air/fuel.

[herman]

This O² sensor, i read about it here before. Where is this sensor responsible for? I thought the O² sensor (also known as lambda sonde) was checking the amount of oxygen in the exhaust. and that this info was an indication for the ECM about how good the combustion was..?
although i understood that this oxygen sensor is not working the whole time? only at idle and full throttle..

[herman]

just made a testdrive, the engine misses when driving 
first when the engine was still cold it went good, but after a few miles it started missing.. at the end when he was on temperature i could hardley start driving in first gear.. it almost stalls. I waited now 24h for the silicon to dry, are there other places i could have created a vacuum leak by swapping the TB?

[Bounty Hunter]

I put 62mm throttle bodies on a lot of 2.5L and 4.0L jeeps and have never had a need for an adj. fuel pressure regulator (4.0L TB is 55mm).  My 2.5L is pretty heavily modified and I still don't run an adj. FP regulator.  May tinker with one someday, found a website where a guy modifies stock FPR's and resells them for a lot less than Hesco FPR and others.

[herman]

Just checked all my vacuum hoses, they're ok. I just started thinking about the AIS.. could it be that if this motor stays open while driving, the engine misses?  Are there ways to check this AIS?

Herman

[herman]

euhm I ment in my last post the ISA motor instead of the AIS 

thx for the hulp guys, I'm learning

[herman]

Ok, I replaced the IAS motor and that gave a good improvement... as long as the engine was cold it ran pretty good. than it got warmer and the missing started again. Finally I checked and replaced the spark plugs, These 4 funny guys looked not that bad but after replacing them the engine goes super again!
once above 2500 rpm i can really feel the difference now! 
thanks for the help