6 million dollar question on corvette fuel filter/regulator

[homemade87]

In the process of getting my truck to the dyno my tuner said I was questionable on fuel on the upper end . So I decided to go with the aeromotive pump with a wire upgrade . Got every thing together and decided to check fuel pressure ( 56lb ) . Should be 58 to 60 so I decided to change filter/reg with the wix 33737 being I am performance oriented on this build . I got 54lb . So I got another thinking I got a low rating one . Buddy of mine got me thinking about connections . He said the fuel feed is supposed to be the center 5/16 . I have my fuel feed on the outer 3/8 connection and the return on the 5/16 center position which I think a lot of people do an has worked fine for a few years now. On an average engine its not a problem . But those few lbs up top make a difference in fuel delivery and addimize the fuel . I have googled and seen it both ways but but unclear which is right . I looked on the wix site for instructions but I did not see any . The wix specs does say 5/16 inlet and 3/8 vapor .

Heres some pictures when I google and the wix site

https://www.google.com/search?q=wix+...HezlC9IQsAQIJA

http://www.wixfilters.com/Lookup/Par...px?Part=209876

If indeed the 5/16 is the feed this could be why the regulator is a few lbs low and not letting the reg work proper .

[homemade87]

I just found this on speedway . Picture shows center 5/16 inlet and 3/8 return . Could be the sticker is just for general reference on that end .


But look what they say in the notes . Which is it.


Notes
The inlet side of this filter/regulator is the end with the (2) male port tubes. The larger 3/8" tube is the pressure inlet from the pump. The smaller 5/16" tube is the return to the tank. The female side of the filter assembly utilizes the male 'snap' in fitting. This is the outlet side of the filter for the line to the fuel rail of th

[mongocanfly]

On the wix filter/reg the angled 3/8 fitting is the inlet..the center 5/16 is the bypass back to the tank. That's some confusing info you got. But when I set mine up they stressed which connector was which.

[mongocanfly]

On the wix filter/reg the angled 3/8 fitting is the inlet..the center 5/16 is he bypass back to the tank.

[homemade87]

Originally Posted by mongocanfly

On the wix filter/reg the angled 3/8 fitting is the inlet..the center 5/16 is the bypass back to the tank.

And I think thats what most of us do and it works fine but thats not what the wix specs say but is it correct .

Product Specifications
Part Number: 33737
UPC Number: 765809337374
Style: Fuel (Complete In-Line) Filter
Service: Fuel
Type: Full Flow
Media: Enhanced Cellulose
Height: 5.755 (146)*
Outer Diameter Top: 2.23 (57)*
Outer Diameter Bottom: Closed:
Nominal Micron Rating: 5
Inlet: 5/16
Outlet: 1/2
Vapor: 3/8

[mongocanfly]

Yeah I read that. Thats what's confusing. They told me 3 or 4 times to be sure not to hook it up wrong. I don't know if it would even work hooked up backwards..mine is not a hot setup but with my walbro 255 I have 55-60lbs on my gauge. I'd have to go back and look but I don't remember my outlet being a 1/2" fitting either. I was thinking it was 3/8"

[homemade87]

I found a couple pictures on another forum that may shed some light on this . I will let everyone look and respond before I comment on these pictures and give my theory .

[mongocanfly]

Yeah I read that. Thats what's confusing. They told me 3 or 4 times to be sure not to hook it up wrong. I don't know if it would even work hooked up backwards..mine is not a hot setup but with my walbro 255 I have 55-60lbs on my gauge.

[mongocanfly]

That's a good pic..that shows the outside fitting being the inlet end the center is the reg bypass..never seen one torn apart. I always wondered how it worked

[homemade87]

Yep , That how I see it also . In on the 3/8 and travels thru the filter, filtered fuel go to engine or back to the tank thru the center 5/16".

Even if you did put fuel to the 5/16 , like Mongo said it would probrably dead head against the regulator part . If fuel did get past and thru the 5/16 fitting it would be unfiltered fuel going straight thru .

So it is confirmed the 3/8" offset fitting is the inlet . There is miss information all over the place for this . Best as I can tell wix even has it wrong on there specs .

Now that I know for sure how it works and I do have it right . It looks like the wix filter is reading lower pressure . I am going to put another on and see what it does . It not any better I am going with a a/c delco . If that don't do it I will put a aeromotive regulator on it and do away with the filter/reg . That probably what I should do anyway .

[homemade87]

Originally Posted by mongocanfly

Yeah I read that. Thats what's confusing. They told me 3 or 4 times to be sure not to hook it up wrong. I don't know if it would even work hooked up backwards..mine is not a hot setup but with my walbro 255 I have 55-60lbs on my gauge. I'd have to go back and look but I don't remember my outlet being a 1/2" fitting either. I was thinking it was 3/8"

If I was not performance oriented on this engine I would not even worry about it . Also I think the 1/2" reference is from the diameter of the fitting itself on the reg . It does accept a 3/8" fuel line.

[mongocanfly]

Are you sure what pressure your pump is putting out before it goes thru the filter? My gauge is after the filter so I don't know what my pressure drop is going thru the filter.

[BigDan3131]

So if you spent the money on that pump why didn't you use their filter with a return style regulator and either use the existing fuel line as the return and use a -8 line or bigger or just run two new lines?

[class01]

anyone have the "fuel system" for dummies? I need all the fittings/lines/regulator all the way from my boyd tank to the motor? anyone have all the part numbers/sizes? thanks

[homemade87]

Originally Posted by mongocanfly

Are you sure what pressure your pump is putting out before it goes thru the filter? My gauge is after the filter so I don't know what my pressure drop is going thru the filter.

The pump I have is capable of 90 psi if regulated to that . The pressure before the filter will not be that if the regulator is dumping fuel back to the tank . I do not know what that pressure would be .

[mongocanfly]

Gotcha there homemade..I was curious what the pressure drop across the filter was after the reg dumped..i know what my outlet pressure is but i have no clue what my inlet pressure is..i think its 80 psi...since those are non adjustable and you need more psi I would go with inline adj reg and inline filter but I guess you done thought of that.

[homemade87]

Originally Posted by BigDan3131

So if you spent the money on that pump why didn't you use their filter with a return style regulator and either use the existing fuel line as the return and use a -8 line or bigger or just run two new lines?

The pump I had was on the edge up top . I wanted a quality pump to do the job with out having to worry about it failing . The plumbing I have is up to the job . This is not a 1000hp set up . I am at 550hp at the flywheel . At 60 psi with a good pump will sure do the job because the volume is there now . The filter/regulator was the problem at 54 psi . Could it have been tuned at the 54psi , sure it could . But i would have rather tuned 58 to 60psi . If it comes to a separate regulator and filter thats what I will do . But at this time the pump was the week link and that has been addressed . The low fuel pressure with the regulator was the issue apparently before and after the pump change . I just wanted to get the pressure to where it was supposed to be before the tune .

[homemade87]

Update , I got another wix filter/regulator . After install it is at 60psi . The other I got was at 54psi . Thats 10% difference in pressure . Not a big deal on just an average swap with a stock fuel pump .

I started this thread to understand the filter/regulator and how it works . As it turns out check your fuel pressure if it is for performance use . Don't just trust what it is suppose to be .

We have confirmed the inlet is the 3/8 offset by the pictures . The internet is all over the place about which is inlet and return . I have come to understand this filter . I am going to tune with this filter and if not satisfied I will upgrade .

[mongocanfly]

That's a lot of difference.I guess that shows what mass production gets you..

[aknovaman]

The regulator is just like a pop off valve on an air compressor. Most fuel pumps can supply 100-150 psi if you dead head them. So the pump runs, it pressurized the filter and rails to 60 psi then fuel pressure overcomes the spring pressure setting and dumps the unneeded fuel back to the tank. The feed is the 3/8 line. Go crawl under any newer Vette to see how it is plumbed. It makes no sense to have a bigger return than the feed line. As the engine uses fuel at any rpm like heavy acceleration, the pump will continue to provide fuel through the injectors and the relief valve closes enough to maintain 60 psi in the rail. So less is returned to the tank when the pop off closes to maintain 60 psi at all Rpm. I have had multiple Vette filters fail right out of the box including some wix filters.

I use the $21 eBay generic regulator and a TPI single in and single out filter. Works perfect every time. The regulator has a good neoprene diaphragm and a chrome check ball and good spring.