Tank Baffle Design

Fuel Supply & Ignition Systems

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sideshow
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Tank Baffle Design

I'm building an interior fill FI/EFI compatible tank for my daily driver.

So what I think I have is a '68 lower section (I filled the gas door, because it was broken & even if I fixed it isn't the locking style) that came with the ghia, and a '65 beetle tank with a rotten bottom.
Image
My theory to date involves using 3/8NPT union and welding near the sand blasted area. Then welding the two part together, followed by a POR-15 like seal kit.

Looking at http://home.att.net/~airdoc/notchfi.html the first three pictures show a baffle in a T-3 tank. I haven't seen a '75 -up US beetle baffle nor do I have one.

So the question is, what should a baffle & pickup look like?

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raygreenwood
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Post by raygreenwood » Sun Mar 20, 2005 8:57 am

I have never seen the inside of say....the type 3 tank and it baffel on the fuel injected car, but many say it looks like a cup...or circular wall. To really work well, I think it should be an upside down cup sealed to the bottom with the inlets inside. There should be a ring of say...half inch holes around the top...to make sure there is no impediment to fuel flowing in....but enough coverage to make sure that it would take a very long angleing of the tank for it all to flow out. There should be several smaller half mon holes around the bottom edge of the cup where it welds or attached to the tank, to allow scavenging fuel from the very bottom when the fuel gets very low. I would think that its total volume should be about 1/2-3/4 liter. Ray

germansupplyscott
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Post by germansupplyscott » Thu Mar 24, 2005 5:08 pm

this is the inside of a VW bus FI tank. you can see the baffling in the foreground of the photo. it is not the best photo, but it is basically a cup with a partial lid on it.

Image

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aircooledtechguy
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Post by aircooledtechguy » Thu Mar 24, 2005 6:34 pm

punkinfair wrote:this is the inside of a VW bus FI tank. you can see the baffling in the foreground of the photo. it is not the best photo, but it is basically a cup with a partial lid on it.

Image

Cool shot Scott!! Thanks for taking the time to share that!!

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mondshine
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Tank baffle design

Post by mondshine » Thu Mar 24, 2005 6:51 pm

In my project to re-do/clean up my CIS installation in my Thing, I'm considering replacing my fuel tank with one from a FI standard Beetle.
I'd only do it if it was close to a "drop in" replacement. Does anybody have any experience with this? If so, is there a source for these tanks?
Tanks, Gary Mondshine

Chris V
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Post by Chris V » Thu Mar 24, 2005 7:07 pm

raygreenwood wrote:I have never seen the inside of say....the type 3 tank and it baffel on the fuel injected car, but many say it looks like a cup...or circular wall...

The way I remember my FI Std Beetle tank was a 3-sided box...slant of the tank made it look like a house built on a hill....no holes, held maybe 12oz.

If somone is really interested in the stock design I'll take it down from the attic and snap a shot.

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mondshine
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Tank baffle design

Post by mondshine » Thu Mar 24, 2005 7:18 pm

Chris-
I'm very interseted in that photo. Maybe we can make a deal and you won't have to put the tank back up in the attic.
Thanks, Gary Mondshine[/quote]

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Tom Notch
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Post by Tom Notch » Thu Mar 24, 2005 8:08 pm

I just happen to have the bottom of a T1 EFI tank sectioned and about ready to graft it onto the bottom of a split tank. Good way to salvage some old tin.
Image

And this is the "Dog Bowl" out of a T3 efi tank, the one I grafted into my notch.

Image

Tom

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germansupplyscott
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Post by germansupplyscott » Thu Mar 24, 2005 8:28 pm

[email protected] wrote:Cool shot Scott!! Thanks for taking the time to share that!!

hey, you are welcome nate. richard atwell is responsible for the photo, in fact.

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sideshow
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Post by sideshow » Thu Mar 24, 2005 10:06 pm

Hmmmm...Cool advise and pictures! And Scott, that looks close to my Bus tank but mine is pre-FI can I assume the general outside shape of a tank (say'65- '70) is close to the '75 and up?

So I guess it is a question about how much volume a baffle should be? So far my bench racing design is taking a piece of 2? exhaust tubing and using that as a sump sticking maybe 1? out the bottom of that sandblasted area.

germansupplyscott
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Post by germansupplyscott » Wed Mar 30, 2005 3:31 pm

sideshow wrote:Hmmmm...Cool advise and pictures! And Scott, that looks close to my Bus tank but mine is pre-FI can I assume the general outside shape of a tank (say'65- '70) is close to the '75 and up?

the exterior dimensions of the early and late bay tanks are very close to exactly the same. the only differences are in the filler neck and the FI tanks have suppply and return, plu the pipes are over to the side, early bay the single outlet is in the middle. not sure about pre-68.

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Wally
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Post by Wally » Fri Apr 01, 2005 3:04 pm

Interesting; I have also made a baffle in my original carb 1303 tank and thought to use a late US 1303 cabriolet tank for it.
I found out after looking inside that tank that it did have a outlet and a return line into it, but NO BAFFLE !!
So, I have cut open my tank and made one myself, largely from the example of Tom Notch's webside of the Type 3 tank :wink: (Thanks Tom)

Works fine now, but haven't tried it on a circuit with little gas in the tank...

Regards,
Walter

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marekv8
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BAFFLE QUESTION

Post by marekv8 » Wed Apr 06, 2005 10:16 am

I'm converting an early Beetle (1964) to an EFI RAT Type 4 2270 and need to modify my tank as well. Just to confirm, would a Standard Beetle tank from 1975-77 have the necessary internal baffles and large enough pick-up to do the job once spliced with the top portion of an earlier T1 tank?

Any advice would be appreciated. Thanks, Dave

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sideshow
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Post by sideshow » Fri Apr 22, 2005 1:51 pm

A few people (ray) have pointed out that the tank design isn't that important and the solution is the two pump method. I was a little surprised that the 1303 used nothing for baffling. So I used some random steel bits to construct this;
Image
Image
The actual volume of this sump is really tiny because the bungs are welded off the bottom and two 7/8 holes were drilled above the tank bottom facing the side and back. Frankenstein would be proud.

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raygreenwood
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Post by raygreenwood » Fri Apr 22, 2005 5:07 pm

Two pumps....is important...but does not replace the baffel. Two pumps prevents a pressure drop on cceleration. The baffel prevents the ingestion of air, which can be a problem with any number of pumps. But, even if you don't have a baffel...you could always build an air seperator external to the tank and before the main pump. But that works best with two pumps. Ray