Topic: Installing aftermarket air intake on 90 YJ

[chardrc]

only way i could find info on flow rates of the jeep tbi injector was to contact a vender that did flow tests. weird thing is that that 32lb/hr was at 20 psi so if that's adjusted for the stock 14.5psi you get 27.25lb/hr.. something is different here... i looked at my email again from the vender and they had listed that for the 5.0l chevy injector it flowed 92cc/15seconds which they said would be 52lb/hr where the converter on the site you linked to would rate it at 35lb/hr.  somewhere here...  and what you said about cfm to lb/hr makes sense....

"The 7747-64 Flows 84cc on my ASNU  Machine On Test E @ 20psi.  These flow as follows on the same test:
5235203...81cc...47lb/hr.....$34.99
5235279...92cc...50lb/hr.....$34.99
5235206..103cc...55lb/hr.....$39.99
17084327...112cc...68lb/hr...$49.99 (out of stock)
Hope this helps you out."

maybe that "test E" means something that would make it make sense...

[sharpxmen]

i was thinking this morning.. and with mpfi you have 1 injector for each cylinder so 19 *4= 76 which is what that program is wanting out of the 1 injector tbi... but realistically not all the cylinders need fuel at the same time so need less at one time...

that's what i was trying to figure out and tried to get my head around it but the actual total fuel needed is in fact related to the CFM air flow, can be 1 cyl or 8 cyl, you get the same amount of airflow (roughly) at a certain rpm for the same displacement to which you add the amount of required fuel - just no way to make the power otherwise. Same for the number of injectors, seems to be working for 4, 6 or 8 injectors so i am assuming is the same deal if you have 1 injector - needs to deliver a certain amount of fuel. the only variable there is duty cycle, but the minimum is still 56lb/hr (at 100% which never happens). I could be missing something fundamental but otherwise those numbers seem to be in sync. The only thing that i don't know is if the factory rating is somehow different. I looked around and didn't find anything on the 2.5L TBI injector.

here's a good article about TBI i just found, seems to be pointing in the same direction with one difference as the duty cycle is mentioned at 85%

http://www.dynamicefi.com/TBI_Fueling.php

[dwtaylorpdx]

One thing to remember about TBI, Its the American version of  Bosch
CIS (Continious Injection System) If you scope the injector with the
engine running you should see the injector signal at a constant trigger
rate that increases Amplitude and frequency as the throttle is opened
and decreases as throttle closes. Its not "timed" to the engine crank position.

In certain applications it can provide better performance than a MPI becasue most MPI
are not timed injection either they are gang fire and timed to engine position. Which
means the injector fires on a "dry" hole every other time it fires.

http://sdsefi.com/techseq.htm give a better description than me.
Also I think their EFi computer is one of hte best out there for 
a stand alone controller for folks like us. For racing anyway, their system
does not focus on emissions and the idle control is very basic. But this thing is
totally K.I.S.S. has just exactly what the engine needs to run and nothing more.

It would be the easiest way I can think of to convert a TBI to MPI for the typical off
road vehicle.

Dave

[C.Redbeardd]

so it doesnt look like there is a bunch of room down there to change the inlet tube that goes into the filter box to the front of the radiator. You think there is enough space to put in a tube and then flex it to the sheet metal?

[sharpxmen]

so it doesnt look like there is a bunch of room down there to change the inlet tube that goes into the filter box to the front of the radiator. You think there is enough space to put in a tube and then flex it to the sheet metal?

i didn't understand the question - can you explain in a bit more detail please.

[dwtaylorpdx]

I just removed the tube from the air box to the front sheet metal.
Made sure both holes were big enough an let it go.

So far no inspection droid has noticed...

Dave

[C.Redbeardd]

i didn't understand the question - can you explain in a bit more detail please.

of course, you know when you said to put a 2.5" to 3" tube to replace the current one? It doesnt look like there is too much room to fit a bigger on in there. IDK, havent tried yet. But thats just what it looks like.

[sharpxmen]

of course, you know when you said to put a 2.5" to 3" tube to replace the current one? It doesnt look like there is too much room to fit a bigger on in there. IDK, havent tried yet. But thats just what it looks like.

i see - you mean on the sheetmetal under the headlight where the square opening is? i'll have a look on mine tomorrow (i have a day off  ) and will report back.

[C.Redbeardd]

well im sure i can cut a bigger opening, BUT im not sure a 3" tube will fit in that space?

[dwtaylorpdx]

I pointed this out before but,,, If you have a tube in there you will
easily fill the airbox up with water if you hit too deep or fast. I did it once,
luckily the air filter stopped the water from making it too far...

I think that's the biggest advantage of a snorkel, the cold air intake above the water line... :)

Dave

[C.Redbeardd]

well, i just think its too bad that I wont be driving through any lakes. :P

[dwtaylorpdx]

I did it hitting about 1' of water at about 40 mph. Came around a corner and there
was a plugged drain. Sucked enough water to stall the engine but it didn't get through the air filter.
The way the stock inlet tube was made it trapped about 1 qt in the airbox... I think the bow-wave
off teh tire is what did it... My bumper has a set of tabs on it now to protect the front from that happening again.

Dave

[C.Redbeardd]

Wow, that just sounds very unfortunate. Ive never had a problem with water. I mean I've driven through much more than a foot of water. Never a problem.

[dwtaylorpdx]

The jeep dealers in 94 and 95 were removing the tubes up here in
Oregon under a TSB because they were replacing too many engines...

Of course I didn't have a lift kit on at that time and a stock YJ is
about the same height as a subaru....

Funny thing, My 85 toyota got recalled for the air tube and they put one
in with a funky plastic bulb on it for the water issues..

Dave

[C.Redbeardd]

Yeah, I'll im doing is making the tube bigger in diameter and replacing the smaller rectangular one. Either way, they would both act in the same manner i assume.