I have a CFI camaro with a 350 in it and 350 conversion van injectors (orange and black) with the stock 305 tune. I put a TPI fuel pump in it and installed a summit fuel pressure guage between the throttle bodies. I did the adjustable fuel pressure mod but was having a hard time getting fuel pressure right. I didnt have a charcol canister so I took and split the return line to use that as well. It sits at 20 psi on the guage.

Will this cause a slightly rough idle, run rich, and foul the plugs?

What do I need to set the fuel pressure to?

What is the best way to do it since I have to take the injector pod off to adjust it?

 

In stock form the CFI system runs at the same pressure as any other factory TBI system of similar vintage- about 10-12 PSI. So, yeah, you're almost double the stock fuel pressure (plus you're using bigger injectors than the 305 tune is expecting).

Regardless of fuel pressure, you need a custom tune. Too many things are different from stock to expect a stock chip to run it very well. Obviously, try turning the FP down and you will probably get improvement. But don't expect fuel pressure changes alone to fix everything.

 

Wow yea, you have gone WAY overboard with fuel.

10-12 psi to start given the larger injectors & please report your BLM's or wide band AFR readings.

Your pressure needs to be set/monitored/logged while engine is at operating temp.

 

13 psi is the best to set the CFI at

 

Well I havent done any tuning. I am waiting to get the car back on the road before I try and convince the wife that I need EBL to get it running right. The truth is that this car runs good, no stumbling, hesitation, and makes good power so I cant complain.

I know that it needs a tune, but I have to do one thing at a time.

As far as fuel pressure, can I pull the pod up and hook up the lines and pressurize the pump, or does it need to be running in order to set pressure?

 

It needs to be checked running, as for setting it lots of us have had to build funky short tools, or do the set it, run & check it, reset, recheck thing.

An ALDL cable & TunerPro RT will get you started datalogging.

 

I figured it needed to be checked running but wanted to be sure.

I will have to get a ALDL cable. I know there are threads on here about where to get one or how to make one so I wont bother asking. Thanks for the info.

 

Actually a modded CFI 350 will tolerate up to 20psi given everything else is up to task. But I agree you need to do datalogging to find what's happening from idle to highway speeds.

 

yeah for modded CFI 350 but my motor is a stock CFI 305

 

I dont have any real mods done to my CFI so I am guessing a safe PSI will be 14. I dont think I am going to run into any drivability issues with that. I just need to find time to make some sort of tool for getting in there with the injector pod on.

 

you don't wont too much or too little pressure
14 psi would be good

13-15 psi would be a good range

 

It is best to parallel plumb the TBI units. As supplied by GM they are in series, which is why the stock injectors use two different flow rates.

To parallel plumb T the supply line and feed each TBI unit. Then each return line from the TBI's go to an external FPR. Then on back to the fuel tank. A FPR such as the Aeromotive 13301 has several inlets so no T required between it and the TBIs.

Remove the accumulator from the one TBI and the FPR from the other and use block off plates on them.

This will make a substantial improvement in fuel delivery. It also makes it easy to adjust the fuel pressure as required for any additional HP that will come down the road. It will also allow you to vacuum reference the fuel pressure once it gets to be over 18 psi. Note that the EBL will properly handle a VRFPR.

Stock service fuel pressure is between 9 & 13 psi. With the injector flow rated at 13 psi.

RBob.

 

RBob, thaks for the reply. So would swapping out my factory injectors for 350 injectors throw off the fuel delivery balance of the TB's?

Also, what size fitting comes out of the TB's?

My factory fittings are a pain to get tight enough to not leak cause they have been taken off and removed so many times in their life. I have seen adapters on the summit website but I dont have a thread guage to figure out if they are SAE or metric and what size they are.

 

Yes, the fuel will be slightly un-balanced with the same size injectors and serial fuel feed.

The following is correct for the standard 2-bbl TBI units. I am not positive that they are the same for CFI 1-bbl TBI units.

The adapters that are in the TBI unit are a metric thread. The TBI unit has 14mm x 1.25 for the feed, and 12mm x 1.25 for the return. These Russell -6 AN adapters thread in in place of the TBI unit adapters:

{edit: these fittings do not fit the CFI TBI}

RUS-640803
RUS-640813

The TBI adapter to fuel line is a metric Saginaw fitting. They are 16mm x 1.50 and 14mm x 1.50. These -6 AN adapters thread into them:

{edit: these fittings do fit the CFI adapters}

Earl's 991955
Earl's 991954

For hose use something that is teflon lined.

RBob.

 

Thanks.

I am pretty sure my adapters are different. I tried to use some of the 2 barrel TBI O-ring style adapters, but they would not thread into my TB's. I did find a pair on a single TBI car at the yard which I use, but things are tight on the drivers side inlet due to the throttle linkage. I wouldnt be able to put an adapter on that one and get a 45* fitting on top of it to clear the linkage. I guess I will have to find a way to identify what the thread size is in my TB's.

I would assume the block off plates would keep me from having to do any return stuff from the TB's and just use the return from the regulator right? (i.e. no fittings needed for the retun side of the TB, just the feed)

 

IIRC, I have a CFI TBI around here someplace. I'll try and find it.

The return ports on the TBIs have to go to the FPR.

RBob.

 

The regulator has 1 inlet port, 3 outlet ports, and 1 return port. I have two feed lines and two return lines from the TB's. How would I plumb all that to make it work?

Would I tee the feed and return lines off of the TB's and hook them both up to a outlet port on the regulator?

It looks as though the regulator has the return port coming directly off of the bottom of the regulator so between the regulator and the TB it would essentially be a deadhead system with the actual return line coming directly off of the regulator and not the TB's.

In that case would it make sense that I could just install one line to the TB's (like a carb) and block the return port? Or do they need to be routed back to the regulator somehow.

(sorry for all the questions, just dont want to be budgeting for unnecessary fittings and hoses)

 

I found the CFI TBI unit but I haven't been able to get the adapters out yet. Need something to bolt the TBI to in order to apply enough wrench to it. Will get there...

Can't, shouldn't, don't, bad news: dead end a TBI unit off a FPR. They are set up internally to vent vapor around the injector(s). When dead-ended vapor goes out the injector which causes banging and lean-outs.

The 13301 FPR return to the tank is the bottom fitting. There are three or four ports that are around the body. These are used to connect to the return ports on the TBI units. Also to be used for a fuel pressure gauge connection.

Feed line from tank: put a T (or Y) on it and then feed each TBI from an end off of the T.

Returns from TBI units: run each return to the body part of the FPR.

Return to tank: this is from the bottom fitting of the FPR to the return line (back to the tank).

RBob.

 

Thanks makes sense. Thanks for the help RBob.

 

can we have photos ?

 

Got the adapter fittings out of the CFI TBI unit. Glad I put a disclaimer in the above post.

Where the adapters thread into the TBI body are completely different then the standard 2-bbl TBI units. So the Russell fittings listed above that replace the adapters will not work on a CFI TBI.

OTOH, where the fuel lines thread into the adapters, they are the same between the CFI 1-bbl & TBI 2-bbl units.

So the Earl's parts can be used. Here they are again:

The TBI adapter to fuel line is a metric Saginaw fitting. They are 16mm x 1.50 and 14mm x 1.50. These -6 AN adapters thread into them:

Earl's 991955
Earl's 991954

I'm going to add an edit to my above post about the Russell parts and CFI TBIs.

CFI 1-bbl fittings on left. 2-bbl fittings on right

RBob.

 

On my car, it did not come with the saginaw fittings on the TB's. It has old fashioned 45* flare connections. Those adapters will not work on mine. I was looking to find the pitch and diameter of the threads in the TB itself and find some sort of carb fitting with a flat o-ring washer setup to connect directly to the TB's. Like the following:
http://www.summitracing.com/parts/EAR-991944ERL/
Then I can plumb the system much easier. I am just not sure if it is a metric or SAE threads in the TB itself. I am guessing it is probably a 10 or 12 mm x 1.5 but I am guessing on that.

 

https://www.thirdgen.org/forums/tbi/...-both-tbs.html

Use this information with caution, fueling schematics pictured would be very problematic.

See post #26

 

Checked the threads on the CFI adapter fitting to TBI body. They are both 12mm x 1.25

This is the same as the smaller adapter (return) fitting used on the 2-bbl TBI bodys. So if you have one it should thread in (I tried it).

Although for some reason as I stated earlier these CFI adapters have the Saginaw type ends for the lines.

If you have a set of calipers and an american thread gauge, a 12mm x 1.25 male thread will come out to about 0.465" OD by 20 TPI.

RBob.

 

6an should be good for both feed and return lines right?

I am not making any real HP compared to a stock vette motor, probably less because I am cruizing around on a 305 tune. I dont plan on doing any serious mods other than header to tail pipe exhaust system and maybe one of them fancy new crossfire intakes from DCS. Much later down the road though.

Edit: I will be doing EBL and a tune before both the above mods.

 

-6 will work great, plenty big.

I found the posts using the dual cfi bodies, (corrected post23), unfortunately it appears that his fuel supply plumbing is grossly incorrect, failing to parallel plumb or position a regulator on the return side of the injectors, I can't see what might be out of photo.

The correct plumbing,
http://www.kinsler.com/Cat_32_Pgs/Ca..._09_Pg_154.pdf

Your decision to employ the EBL system is IMO one of the best made for your ride.

 

I am going to set the sytem up like RBob said and run the feed directly to both TB's with a Y. I would like to use a tee, but I dont know if I would have distribution problems. A tee would be cleaner and easier to route though.

Then I am going to run the return lines (a tee would produce a cleaner layout) to the VRFPR. Then I will probably run a 3/8" aluminum line back to the tank from the bottom of the regulator.

I am assuming I would run the vaccum connection to manifold vaccum?