AFI Complete Kit Questions

I

IHCScout78

Member
Hi,

considering your complete TBI system.

Does the o2 sensor require a bung to be welded in the exhaust? I have ceramic coated stan's shorty headers. Where do you recommend the sensor to be installed?

Do you have any vapor lock issues with the external fuel pump? I have had some bad experiences with rail mounted pumps on a previous efi conversion.

For a 345, which manifold(2bbl, square bare, spread bore) do you recommend?

If you had the aluminum manifold in stock, that would definitely be part of the project....
 
Bill is the moderator here, but I will try and answer a few of your questions. As for the o2, normally the bung is welded in the collector of the header, you could move that back a bit to the exhaust pipe, but then I would recommend a heated o2 sensor.
You would be in open loop longer without one.

Vapor lock is where the gas expands at or near the fuel pump. So on a stock carb setup, the gas line running to the pump can vaporise and therefore the pump wont pump vaporized gas. With FI, the pump is constantly circulating the gas, hence the need for a return line from the TBI unit. So I'm not sure how you had vapor lock with your other FI system.
It is possible when very low on gas and climbing a steep hill that all the gas is away from the pickup tube and that would cause an issue

as for the manifold I would recommend the one you have, but if your thinking of mpfi (multi port fuel injection) then you need the aluminum intake.
 
Hi Craig,

thanks for the response.

I figured the o2 sensor belongs in the collector. Guess I'll have to grind off some of that sexy ceramic coating.

As for vapor lock:

with an external fuel pump, the hose from the pump into the tank is vacuum. I did an efi conversion for an oem with a rail mounted pump. During vapor lock testing, we instrumented the pick up line for temperature and pressure. We also installed clear tubing and made a video of the pick up line.

In this case, the bubbles causing vapor lock could be seen forming in the pick up line. Although the fuel temperature was reasonable, the temperature and pressure combination in the pick up tube were in the vapor region of a fuel phase change chart.

The problem was resolved with an in-tank, immersed pump. No pick-up tube, no low-pressure/vacuum.

If folks here have good experience with the external pump, I'll start with that. If not, I'll cobble an in-tank pump.

I see in your thread you are using the 2 bbl manifold, and I saw a comment from bill about size matching the holes, so sounds like the way to go. I happen to have one in the garage somewhere....

Thanks again,

ken
 
We do sell a 33 gallon fuel tank with in tank fuel pump arrangement. I don't have all my information in front of me but if memory serves me correct the tank with the internal fuel pump should run approximately $800 and that is with a factory GM pump. Best to call later this week as I'll be glad to quote you a more accurate price.
 
Hi Jeff,

I already have a northwest metal products 33 gal tank installed.

How difficult is it to put a pump in?

Ken
 
ihcscout78 said:
hi Jeff,

I already have a northwest metal products 33 gal tank installed.

How difficult is it to put a pump in?

Ken
Click to expand...

Since it wasn't made initially for the intake fuel pump you will have to cut it open on top to add in some additional baffles or "fuel snail" as I call it that will help keep the fuel from sloshing away from the pump. From there you can add the fuel pump mount. See these pictures in this post - http://www.forums.IHPartsAmerica.com/IH-only-build-ups/71-ld-s-custom-Scout-II-2.html#post473

Its not a nwmp tank but the procedure is the same.
 
I wouldn't mess up the coating on the header (and void the warranty) to install the o2 in it. Moving it to the pipe a couple of inches from the flange should be fine. The worst that can happen is that it falls out of closed loop during an extended idle. If that proves to be a problem then it is a simple process to switch to a heated o2 sensor.

It is important to note however that the system May be set up for open loop idle so it wouldn't make a difference anyway. You'll have to check with Jeff to see if the chip they supply is set up for open or closed loop idle.
 
X2


3" won't make a differance.


Post a pic of your headers if you get a chance, starter side would be nice.
 
I recommend the 3 or 4 wire o2 sensor behind the header.

No problem with vapor lock using an external pump if you follow the basic installation instructions.
 
Thank you for the responses.

2 bbl manifold, sensor in the exhaust pipe behind the collector, external pump. I suspect the internal pump is more important for mpfi due to higher pressure.

Also the mpfi pumps I have used are turbine type, which do not self prime.

I do like Jeff's snail. Nice work!

No digital pics until my son finds the cable....but he headers are the stan's shorties. I am using a geared starter for clearance.

My company is going through lay-offs. If I still have a job, I'll order the kit this spring.

If not, should have time to go the junk yard route....

Ken
 
You must log in or register to reply here.
Back
Top