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Setting up a 67 Fastback for FI
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Max Welton
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PostPosted: Mon Jun 19, 2017 5:16 pm    Post subject: Setting up a 67 Fastback for FI Reply with quote

Continuing the project to move my 1776 type-3 Megasquirt engine into a 67 Fastback I picked up last year. In the 68, I was able to use the fuel-lines (supply and return) already present in that car. But the 67 was a carb car, so I need to provide the return line.

I'll store all the pictures with the same title so this search should always find the collection.

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At the tank, I'm using a T fitting from CB. This allows any air in the return line to just escape into the tank. Gravity is my friend.

Image may have been reduced in size. Click image to view fullscreen.



My return line from the engine will run through a pass-through under the rear seat, lay in the corner of the tunnel and floor (under the carpet) and through another pass-through under the passenger-side foot-board to the tank. Following the late Bob Hoovers lead, I made the pass-throughs from 1/4" ID lamp repair pipes.

Under the rear seat ...

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Image may have been reduced in size. Click image to view fullscreen.


and under the foot-board...

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Image may have been reduced in size. Click image to view fullscreen.


Max
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PostPosted: Tue Jun 20, 2017 8:50 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

If I could give a little advice from someone who has installed many efi systems, do not use the existing fuel line, use 2 5/16" min. for pressure and return, also do not use the "T" fitting on the bottom of tank. I destroyed 2 fuel pumps due to cavitation trying to make it work.
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PostPosted: Tue Jun 20, 2017 10:10 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Can you tell me more about your setup?

What kind of fuel pumps were you using? Where were they located? Why do you think the CB T fitting is a problem? Were you still using the stock sock in the tank? What other filters and where were they?

Max
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PostPosted: Tue Jun 20, 2017 11:48 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
Can you tell me more about your setup?

What kind of fuel pumps were you using? Where were they located? Why do you think the CB T fitting is a problem? Were you still using the stock sock in the tank? What other filters and where were they?

Max


On my 71 Notch, I ran 2 new 5/16ths lines under the car right along the plate in the center, then they dipped under the rear subframe. I used Adel clamps to hold the lines in place, and I never saw any "impact" marks from it being lowered. The 2 new lines also ensured that I had clean fuel running thru them, and IF I ever needed to replace 1, I could do so easily. It also ensured that I didn't have any rust thru thin spots in it (you can't really see inside the tunnel after all).

The idea behind using 2 same sized lines, and not using the factory line in the tunnel 1/4 inch (5mm) line is flow. The smaller line becomes a restriction, and could cause problems with pressure regulation and flow to your injectors. Most FI systems use 5/16ths minimum, and others go to 3/8ths. My 92 Geo (Toyota wannabe) uses 5/16ths for both lines, as does the 3 Hondas I have here. The older VW FI like your 68 had used 7.5mm lines.

I'd also set up the return line to dump into the fuel filler neck, as it's large enough to access a fitting into without having to do any welding. Just a thought.

I hope this helps.
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PostPosted: Tue Jun 20, 2017 12:26 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
Can you tell me more about your setup?

What kind of fuel pumps were you using? Where were they located? Why do you think the CB T fitting is a problem? Were you still using the stock sock in the tank? What other filters and where were they?

Max


CB pump with CB fitting, what happens is the pump will pull fuel from both the tank and the return, it will pull harder on the return, it then will cause cavitation within the "T" the pump will become restricted and burn up. There is a reason all auto manufactures use a return into the top of the tank with a tube going to the bottom.
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PostPosted: Tue Jun 20, 2017 12:54 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Bobnotch wrote:
I'd also set up the return line to dump into the fuel filler neck, as it's large enough to access a fitting into without having to do any welding. Just a thought.

I hope this helps.

I understand the need to avoid undersized lines. I can (and now will for sure) actually test for negative pressure in the feed line to the pump to see if that is actually happening. I can also measure load on the pump in various ways with the regulator operating in the high pressure part of the loop.

But I still don't get why you guys don't like the T fitting (Scott) or why the reco for returning to the filler neck (Bob).

I'm just trying to understand.

Max
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PostPosted: Tue Jun 20, 2017 1:29 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
Bobnotch wrote:
I'd also set up the return line to dump into the fuel filler neck, as it's large enough to access a fitting into without having to do any welding. Just a thought.

I hope this helps.

I understand the need to avoid undersized lines. I can (and now will for sure) actually test for negative pressure in the feed line to the pump to see if that is actually happening. I can also measure load on the pump in various ways with the regulator operating in the high pressure part of the loop.

But I still don't get why you guys don't like the T fitting (Scott) or why the reco for returning to the filler neck (Bob).

I'm just trying to understand.


Experiance one, all auto manufacture's do it this way two. Do you really think any one at CB is smarter than the engineers at Ford, GM, toyata, honda ect? Oh, and I used to work there. Funny thing when I was there returning to the bottom of the tank was an extreme no no.
I have had 2 pump failures using the "T" on the bottom of tank, both cured by changing the location of the ruturn.
Max

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PostPosted: Tue Jun 20, 2017 1:44 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

mcmscott wrote:
If I could give a little advice from someone who has installed many efi systems, do not use the existing fuel line, use 2 5/16" min. for pressure and return, also do not use the "T" fitting on the bottom of tank. I destroyed 2 fuel pumps due to cavitation trying to make it work.



Yes.....all spot on. Larger lines...and....as mcmscott noted....there is a reason the factory used separate inlet and outlets for fuel supply and return. That is to prevent cavitation at the Tee from blocking flow to the pump.

And..by the same reasoning...the original D-jet used a "Y" ..and not a "T"between the return line and the relief port on the original three port pump.

You wont need that with a modern two port pump but you must have a separate inlet/outlet for the tank. Ray
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Max Welton
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PostPosted: Tue Jun 20, 2017 5:32 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Thanks guys. The fuel loop on the engine is unchanged from when it was on the squareback. The build thread is over on STF somewhere. I put something like 25k miles on it without any pump issues. Airtech e2000 pump. When I get home i'll measure the lines. I used 1/4" ID FI hose where I didn't have hard lines.

Routing the return up to the filler neck is a good idea. And I can easily run a second hard line. I did buy 25' of the steel brake line... Wink

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PostPosted: Wed Jun 21, 2017 5:52 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

I actually have another question for you guys. In my 68 I mounted the pump on the beam very close to the location of the original Bosch pump.

For the 67 I am planning to locate the same airtech pump over the transmission to simplify the wiring. The ECU and relay board live under the rear seat. What do you see as implications of the increased length of the low-pressure supply and return line runs?

Max
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PostPosted: Wed Jun 21, 2017 6:10 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
I actually have another question for you guys. In my 68 I mounted the pump on the beam very close to the location of the original Bosch pump.

For the 67 I am planning to locate the same airtech pump over the transmission to simplify the wiring. The ECU and relay board live under the rear seat. What do you see as implications of the increased length of the low-pressure supply and return line runs?

Max


Keep it on the beam. The pump needs to be mounted as close as possible to the fuel tank. It has much more ability to "push" fuel through the lines than it does to "pull", which is why FI pumps are always mounted adjacent to, or inside, the tank. Trying to maintain a constant suction over a long distance will cause it to overheat and fail, not to mention the added heat which would rise from the transmission.
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PostPosted: Wed Jun 21, 2017 10:44 am    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Donnie strickland wrote:
Max Welton wrote:
I actually have another question for you guys. In my 68 I mounted the pump on the beam very close to the location of the original Bosch pump.

For the 67 I am planning to locate the same airtech pump over the transmission to simplify the wiring. The ECU and relay board live under the rear seat. What do you see as implications of the increased length of the low-pressure supply and return line runs?

Max


Keep it on the beam. The pump needs to be mounted as close as possible to the fuel tank. It has much more ability to "push" fuel through the lines than it does to "pull", which is why FI pumps are always mounted adjacent to, or inside, the tank. Trying to maintain a constant suction over a long distance will cause it to overheat and fail, not to mention the added heat which would rise from the transmission.


Exactly. When I use a low pressure pump for carbed engines, I locate the pump near the tank on them as well. Most electric fuel pumps are better "pushers" than they are "pullers". Plus, it keeps the inlet side of the pump full of fuel (unless the tank is dry), which makes it already primed.
Putting it at the back of the car will cause the pump to burn up from running dry (trying to get primed). Remember, most electric pumps use the fuel to keep them cool.
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PostPosted: Fri Jun 23, 2017 3:46 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

So this shows the input port supplied with the Airtex E2000 pump (right) and the 67s stock output pipe (left) from the tank. Clearly the old line is smaller so I will be running a new supply line. I can absolutely see how that small line could cause problems.

Image may have been reduced in size. Click image to view fullscreen.


This next is really interesting. The output (left) and input (right) ports supplied with the airtex pump are not the same size. They intentionally reduced the size of the output (high-pressure) port.

Image may have been reduced in size. Click image to view fullscreen.


Max
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PostPosted: Fri Jun 23, 2017 4:35 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
So this shows the input port supplied with the Airtex E2000 pump (right) and the 67s stock output pipe (left) from the tank. Clearly the old line is smaller so I will be running a new supply line. I can absolutely see how that small line could cause problems.

Image may have been reduced in size. Click image to view fullscreen.


This next is really interesting. The output (left) and input (right) ports supplied with the airtex pump are not the same size. They intentionally reduced the size of the output (high-pressure) port.

Image may have been reduced in size. Click image to view fullscreen.


Max


Its not a problem either way really. The stock pump which puts out 1 liter per minute at its max pressure of 70 psi had no issues with the feed pipe diameter.

The reason why its good to upsize the line a little is that the original D-jet pump had exceptional suction. While the newer turbine ring type pumps like the Airtex are so much better than the sliding vane type of the 80s and are made to better tolerances than the turbine pumps of the 90s and early 2000s......they still suck a bit less hard than the low to mid pressure roller cell pumps.....and better than the high pressure roller cell pumps like the Bosch 044.

There are several variants of the Airtex 2000. What you are seeing on the outlet "may" be a check valve pressed in. Some of the output pipes unscrew and can be changed as well. Ray
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PostPosted: Fri Jun 23, 2017 5:20 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

I'll have to check that. I'll also check the Airtex I used on the 68. It's still strapped to its beam out in the yard. I bought this one new a while back for another project and decided to use it on the 67.

But it has me thinking about flow.

It seems like the amount of circulating flow should be related to the amount of pressure being maintained between the pump and the regulator. Higher pressure => more restriction from the reg => less flow to the return line. Seems to work at the limits.

Max
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PostPosted: Fri Jun 23, 2017 5:55 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Max Welton wrote:
I'll have to check that. I'll also check the Airtex I used on the 68. It's still strapped to its beam out in the yard. I bought this one new a while back for another project and decided to use it on the 67.

But it has me thinking about flow.

It seems like the amount of circulating flow should be related to the amount of pressure being maintained between the pump and the regulator. Higher pressure => more restriction from the reg => less flow to the return line. Seems to work at the limits.

Max


Bear in mind that tbese pumps.....by themselves..... produce volume.....not pressure. The regulator creates pressure by restricting that volume.

The pump....puts out nearly.... ....the same volume when its restricted by the regulator as it does just flowing freely.
But.....the problem that people run into when testing a old pump is to not hook the pump up direct to power with the engine off.....and measure the return volume from the regulator.

On a new pump or one in great shape....the output volume under pressure is only slightly less than when unrestricted.
An old or worn out pump can move the same volume as a brand new pump....unrestricted. but when you put load on it.....the return volume drops significantly. This can be as simple as no check valve or a bad check valve......or a very worn out turbine or compression area in the pump. Flow across the compression stage in the turbine stalls, the turbine cavitates and the pump overheats. Ray
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PostPosted: Fri Jun 23, 2017 11:10 pm    Post subject: Re: Setting up a 67 Fastback for FI Reply with quote

Also keep in mind that the Airtex pump is designed for quick release couplings, which might help explain the slight reduction in output size.

I think if you ran 5/16ths lines from the tank to the engine, to the regulator and back to the tank you should be fine. I've had no issues with it on my wife's 70 Fastback, or my old 71 Notchback.
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