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General Forums => The Mess Hall => Topic started by: chardrc on October 07, 2007, 04:42:31 PM

Title: 2 2.5l tbi questions
Post by: chardrc on October 07, 2007, 04:42:31 PM

as the name says i have to questions that are inspired by mpi mods. first i know guardian7 was making a throttle body spacer for the tbi 2.5l but the project kinda died when he got a new jeep. and I'm thinking of making my own using the cnc machine at school. so im looking for dimensions. i could measure bore size myself but how tall should it be?

my second question is about the tbi fuel injector. after reading pages upon pages about the ford 19# injectors for the mpfi 2.5l's i started to wonder if you can swap in a better injector for the tbi 2.5l after looking online i could find no specs on anything :brick: (as usual) but i found a site with pictures and the injector or the 2.5l looks almost identical to the injector(s) for the Chevy 4.3l and 5.7l. so this reminds me i have a 2 4.3l v6s around so i look at those injectors and the 2.5l injector and they look the same from the top. (didn't take them out of the carrier because all my tools are trapped in by our pool table). so what do i have to worry about if i try this out. is there any seals on the bottom end/ how do you know which way to plug them in (2 wire plug)

i know this is kinda a blind guess since the same amount of pressure will be going up to it so the only main thing that could be better is spray pattern as seen with the ford 19# injectors.

hope i didn't lose anyone in my days worth of questions and typing.

Title: Re: 2 2.5l tbi questions
Post by: dexetr30 on October 07, 2007, 05:19:19 PM

As far as I know most spacers are 1" thick.

Title: Re: 2 2.5l tbi questions
Post by: Shawn_c on October 07, 2007, 05:23:53 PM

Also you could use the TBI gasket as a template for your bore.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 07, 2007, 07:18:40 PM

ok found some info on the tbi injectors. the injector for the tbi 2.5l is made by the same company that makes the gm tbi injectors.     "ROCHESTER PRODUCTS". havent foudn the stock flow rates but found a handy chart for the chevy v8tbi injectors

Application    Throttle bore size    Injector color code    Flow rate    Part # 2.8l v6    1-3/8"    Black/White    ???    GM 5235430 *RPD 4.3L    1-13/16"    Yellow/Blue    ???    GM 5235203 *RPD 5.0L    1-13/16"    Green/White    40 lb/hr    GM 5235279 *RPD 5.7L pickup    1-13/16"    Orange/Black    55 lb/hr    GM 5235206 *RPD 5.7L Cop Car    1-13/16"    Yellow/Brown    65 lb/hr    17084327-ACR Late big block pickup    2"    Blue/Black    80 lb/hr    GM 1708430 *RPD big block pickup    2"    Dark Red/Dark Blue    90 lb/hr    GM 5235231 *RPD

now if i can just find what the stock flow rate is in comparison. oh and the stock gm fuel pressure is 13psi. what is jeep stock?

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 07, 2007, 07:43:50 PM

ok jeep 2.5l tbi fuel pressure is 14-15psi according to auto zone website. so both injectors are made for about the same pressure.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 09, 2007, 03:05:50 PM

ok so i emailed a company that sells the stock fuel injector and the Chevy one asking for the flow rate and this is what i got in reply.

The 7747-64 (jeep) Flows 84cc on my ASNU  Machine On Test E @ 20psi.  These flow as follows on the same test:
5235203 (4.3l v6)...81cc...47lb/hr.....$34.99
5235279 (5.0l v8)...92cc...50lb/hr.....$34.99
5235206 (5.7l v8)..103cc...55lb/hr.....$39.99
17084327 ( 5.7l cop v8)...112cc...68lb/hr...$49.99 (out of stock)

so the question now is how much of a higher flow rate would you want/ need. for a turbo or just to replace it and have say a freed up intact and a header/ cat back.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 10, 2007, 07:03:49 PM

ok got another email for the company to clarify the numbers. it was 88cc in 15 seconds. so they said the stock injectors are 48#.

the jeep virus is hitting me bad now and is making me want to spend $$$. so my next question is what header do you guys suggest?

Title: Re: 2 2.5l tbi questions
Post by: Jeffy on October 11, 2007, 12:27:34 AM

Keep in mind there are two ways to get more fuel  One is to install fuel injectors with a higher rating at the same pressure.  The other way is to boost the pressure.

This means, you better keep track of the pressure tested vs. what the Jeep produces otherwise, you're not comparing apples to apples.

To really know what pressure you will need for a Turbo, you will defiantly need a wide-band O2 sensor to monitor the actual air/fuel curve.

Title: Re: 2 2.5l tbi questions
Post by: jfrabat on October 12, 2007, 03:13:56 PM

How can you tell if the O2 sensor that I have in place is wideband or narrowband?  I replaced mine with a Bosch sensor about ayear ago, but I just looked for a direct replacement; I have no idea what I have in there!

Title: Re: 2 2.5l tbi questions
Post by: Jeffy on October 12, 2007, 04:02:40 PM

Quote from: jfrabat on October 12, 2007, 03:13:56 PM

How can you tell if the O2 sensor that I have in place is wideband or narrowband?  I replaced mine with a Bosch sensor about ayear ago, but I just looked for a direct replacement; I have no idea what I have in there!

Unless you specifically bought one, you don't/wont have one.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 12, 2007, 04:13:35 PM

i just got a reply back from jeep after i requested my jeeps build sheet. turns out i have three unfixed recalls on my jeep.
747  DISC BRAKE ROTORS ( those where worn all the way through which resulted in me getting my jeep :weee:)

617  OXYGEN SENSOR/CAT. CONVERT.

B03  PARK BRAKE PEDAL ASSEMBLY

i never use my parking brake so not too concerned there but the cat and oxy sensor would be nice to have new ones of. although i would like to get high flow and wide band which i doubt the recall would help any for.

Title: Re: 2 2.5l tbi questions
Post by: Guardian7 on October 15, 2007, 12:44:56 AM

chardrc, if you use a gasket for the TB spacer pattern it'll be way off, the gasket has a larger diameter bore.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 16, 2007, 06:28:04 PM

ok so i went to the junkyard with a friend today. and decided to to get some 5.0l injectors. so i got 2 green 5.0l injectors from a Chevy van 20.. all have to clean them up and get new o rings but ill eventually get around to trying them out.

Title: Re: 2 2.5l tbi questions
Post by: aw12345 on October 16, 2007, 07:06:33 PM

To fatten the fuel mixture you could also simply turn up the fuel pressure a bit its very easy on the GM TBI
We had to tinker with that with a Howell TBI conversion for a 4.2L Jeep engine

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 16, 2007, 07:32:21 PM

that was my other option.. but i was already there and they were only $8 for 2. bu i may adjust the fuel pressure instead...

oh and i found this http://www.thirdgen.org/o2tuning (http://www.thirdgen.org/o2tuning) website (don't know if the link worked but we will see) telling how to use a digital multimeter to read an 02 sensor. only thing that scars me about it is not grounding it out.

1 more question. how come this thread disiperes into thing air from the mess hall. not talking about lake of posts to it but it is simply gone adn i have to go to resent posts by me to find it.. idk maybe I'm just blind.

Title: Re: 2 2.5l tbi questions
Post by: chardrc on October 16, 2007, 07:33:43 PM

fail. i apparently cant read right :wall: :wall: :wall:

Title: Re: 2 2.5l tbi questions
Post by: aw12345 on October 16, 2007, 08:07:14 PM

To check a O2 sensor a digital multimeter is fine. When its a single wire sensor its a snap. Carefully insert a small paper clicp or something like it from the back of the connector connect positive wire of meter grount the other one
and you are good to go. On 3 wire sensor one wire is ground one is 12 volts with the ignition on and one is the sensor wire 0.0 to 0.8 volts. If you have a scanner you can also see if the feedback system works by driving it lean and rich and look for the fuel numbers to change, on GM block learn, on Fords fuel trim forgot what Chrysler/ Jeep calls it. You do this by touching the sensor wire with one hand and touching the positive or negative battery terminal with the other hand, this gives it enough resistance to not hurt anything but drives the injection either lean or rich.