Semi-Returnless Fuel Setup

[R3N3]

Is there any disadvantages to running a semi-returnless fuel setup (fuel return from fpr and only 1 line to rail)? It would really let me simplify the fittings to the rail (I would just run a centre feed). I’m only going to be pushing 300ish kW so I’m assuming it will be ok?

For context, I’m running the following

- stock hardlines with AN adaptors

- GFB FX-R regulator (6AN one)

- 30 or 40 micron (can’t remember) cartridge filter 

- EFI hardware fuel rail (8AN ports at ends of rail and a single 6AN port in centre)

Cheers

[Duncan]

I'm a little confused what you mean exactly, but at 300kw the stock lines and rail are fine so whatever you are thinking above should be too.

[R3N3]

7 minutes ago, Duncan said:

I'm a little confused what you mean exactly, but at 300kw the stock lines and rail are fine so whatever you are thinking above should be too.

Sorry, hopefully this makes it more clear:

[GTSBoy]

What he means is the reg is mounted somewhere off rail, say on the guard or firewall and returns to tank from there. A T takes fuel from the supply side of the reg over to the fuel rail and the rail is dead head, just like a returnless system.

The disadvantage of any returnless/semi-returnless system is that the fuel sits in the rail until it is used, so you do have higher possibility of heat soak related problems

I wouldn't even bother. Why bother having the reg in the engine bay and a return line? Just put the reg at the rear of the car like a true returnless system.

If you're going to put the reg in the engine bay, just plumb the rail up properly, like everyone else has always done. It's a piss or get off the pot situation here.

 

Edited May 2, 2023 by GTSBoy

[Duncan]

Thanks the pic helps, I've not had any experience with semi or fully returnless personally. A standard, return setup would certainly work at that level with -6 feed lines.

I would say that a single 30 micron filter might be an issue, generally you would have a larger (100 micron) pre-filter as well.

[R3N3]

ok, thanks team.

its clear what i need to do!

@Duncan so are you saying to have 2 fuel filters?

[Duncan]

Yes, I would (I do). The small filter may block very quickly and require regular cleaning (or you risk sudden engine death)

[R3N3]

9 minutes ago, Duncan said:

Yes, I would (I do). The small filter may block very quickly and require regular cleaning (or you risk sudden engine death)

Ok, out of curiosity what sort of micron filter is the stock-type one? 

[Murray_Calavera]

Am I the only one that thought 30 micron filter wasn't small enough? 

This is the efficiency chart of the filter I use, it filters down to 5 microns. 

[Duncan]

no idea on the standard one, ryco don't think it is important to list as a spec: https://rycofilters.com.au/part/z387

however not the size of the filter is very large compared to the 30 micron AN style ones.

[GTSBoy]

Paper filter elements for petrol are generally ~10 micron. And once they have any sort of filter cake on them, they tend to filter even finer.

[R3N3]

4 hours ago, Duncan said:

no idea on the standard one, ryco don't think it is important to list as a spec: https://rycofilters.com.au/part/z387

however not the size of the filter is very large compared to the 30 micron AN style ones.

What filter sizes do you run in your 2 filters?

[Duncan]

I use a larger 100 micron and smaller 30 micron set. Of course it is in a race car but it does run pump fuel, I just clean them out each year

[MBS206]

6 hours ago, Murray_Calavera said:

Am I the only one that thought 30 micron filter wasn't small enough? 

This is the efficiency chart of the filter I use, it filters down to 5 microns. 

Micron ratings are useless without the efficiency data like you've given.

 

If you chose between 2 filters, one 20 micron, the other 30 micron, purely based on the size, you could be in for a shit show, as that 20micron may be at 1%, while the 30micron is 100% efficient.

 

On your data, you may be 5 micron, but that's only 88.2% efficient.

If wanting 100% efficiency (where I feel a filter should have it's micron rating taken at), your rating would be somewhere at 25 to 30 micron.

[Murray_Calavera]

6 minutes ago, MBS206 said:

Micron ratings are useless without the efficiency data like you've given.

 

If you chose between 2 filters, one 20 micron, the other 30 micron, purely based on the size, you could be in for a shit show, as that 20micron may be at 1%, while the 30micron is 100% efficient.

 

On your data, you may be 5 micron, but that's only 88.2% efficient.

If wanting 100% efficiency (where I feel a filter should have it's micron rating taken at), your rating would be somewhere at 25 to 30 micron.

Yep, agreed. 

I thought 5 micron at 88% efficient was quite good. I don't know of a filter that does a better job, if I did I would have gotten that one instead lol

[Dose Pipe Sutututu]

23 hours ago, GTSBoy said:

I wouldn't even bother. Why bother having the reg in the engine bay and a return line? Just put the reg at the rear of the car like a true returnless system.

Mark at MRC Performance & Dyno in NSW does this quite often, then uses both return/feed OEM lines as dual feed lines to the fuel rail.

The only drawback from this is the length of the vacuum hose from plenum to regulator at the back of the car, also increases the chances of that line failing from debris, unless you go tits out and make it all a hard line.

 

 

@Murray_Calavera I run a 40 micron filter, followed by a 10 micron filter, seems to be the norm? I just copied whatever most of the big shops do LOL.

Another sex spec option, something I may do in future if I still haven't gotten rid of the shit box is to run this:

http://injectordynamics.com/id-f750-fuel-filter/

has a gauge to show you the health of your filter too, no guessing around pulling things out to try clean/resolve.

[R3N3]

2 hours ago, Dose Pipe Sutututu said:

Mark at MRC Performance & Dyno in NSW does this quite often, then uses both return/feed OEM lines as dual feed lines to the fuel rail.

The only drawback from this is the length of the vacuum hose from plenum to regulator at the back of the car, also increases the chances of that line failing from debris, unless you go tits out and make it all a hard line.

 

 

@Murray_Calavera I run a 40 micron filter, followed by a 10 micron filter, seems to be the norm? I just copied whatever most of the big shops do LOL.

Another sex spec option, something I may do in future if I still haven't gotten rid of the shit box is to run this:

http://injectordynamics.com/id-f750-fuel-filter/

has a gauge to show you the health of your filter too, no guessing around pulling things out to try clean/resolve.

Thanks, based on that flow graph, I’m assuming that’s what you have @Murray_Calavera?

[Murray_Calavera]

@Dose Pipe Sutututu

40 + 10 micron sounds good to me.

That's the filter I'm using. This is my setup, ignore the yellow circles, they were for an unrelated thread.

 

[Dose Pipe Sutututu]

@Murray_Calavera sexual, less faffing about with those stupid twin filters.

Makes servicing so much easily.

I haven't bothered to service mine because it's a pain in the arse to undo lol

 

[GTSBoy]

4 hours ago, Dose Pipe Sutututu said:

The only drawback from this is the length of the vacuum hose from plenum to regulator at the back of the car, also increases the chances of that line failing from debris, unless you go tits out and make it all a hard line.

This is the reason that factory returnless setups use a fixed pressure reg with no MAP reference.