Brettus

iTrader: (2)

People are always asking if they can use a large 300l/hr plus pump in the stock fuel basket . Up till now I've put people off this because :

1/It causes the fuel to overheat at cruise
2/ It causes a pressure spike as the second stage kicks in due to siphon being overwhelmed
3/Most don't make that kind of power anyway so there's no point
4/It's kinda tricky to do and I can't remember the exact detail because it was so long ago that I did it.

But I've operated a DW300 pump (340l/hr) for about 5 years now and had no issues. It only runs out of flow at around 420whp when using E60 - so that gives you an idea how far you can go with this.
There is a way to avoid 1 & 2 and it's to drill out the siphon tube.

Edit : thanks to Madrotor for doing this so we now have better method :
Using a 1.5mm diameter stainless steel welding rod (or similar) heat the rod sufficiently enough to melt plastic and insert it into the siphon assembly hole and withdraw.
Ensure the siphon orifice (hole at 90 degrees) is clear after doing this.
Melt the popoff valve at top of assembly such that it can't...... pop off !

Reassemble and be sure to check siphon is still working by monitoring fuel gauge on first tank.

slash128

Heh, I was just contemplating the DW300. Any further details of how you did to install? Aside from drilling out the siphon was it pretty much drop-in? Any other mods?

Brettus

iTrader: (2)

Just the usual melting the popoff is the only other thing . I still don't have a way of posting any pics yet (phone died completely) but there really isn't much to show. I figure if anyone is clued up enough to get it all apart and understand what they are looking at ............. the mod will be really simple.

I worked out the drill diameter by doubling the x sectional area of existing with the logic that the new pump is double the flow of the old one so would need that to get the same pressure at the siphon to get it to flow. Be careful about getting all the swarf out !

Ricky SE3P

iTrader: (10)

If it helps, when I installed my DW 200 I successfully melted the pop off using the following method.

-Grab a piece of metal bar with some pliers (I used 3/16" thick as I had a small 4" long piece lying around. Locking pliers made this even easier.)
-Use a heat gun to heat the piece of metal. I would advise heating the piece of metal a little at a time and trying to do melt the pop off just enough to fuse the plastic together without damaging the assembly.

TeamRX8

iTrader: (25)

hopefully you started with a brand new S1 pump module then since the internal filter isn’t replaceable.

Blackwell

I was about to start a thread asking how far I can take the factory fuel setup. I really didn't want to go to a fuel cell and making lines. If you can detail the steps I will take pictures while I do it.

Brettus

iTrader: (2)

Before you start ...pick up a mini hand drill set similar to this (0.5-1.5mm)

https://www.ebay.com/itm/Mini-hand-d....c100009.m1982

Once you have the siphon apart you need to measure the size of the existing hole using one of the drills . It's somewhere around 0.75mm . Then calculate the x-sectional area of existing ...double that area then work out what diameter it needs to be to get that area.
I do remember the drilling out to be quite tricky to do but i managed it somehow...lol

As far as disassembling the pump,fitting the new pump and melting the popoff etc ...follow MMs fuel pump upgrade thread.
https://www.rx8club.com/series-i-maj...-modes-176491/

Blackwell

I have the drills and a pump on the way. Probably a week or two.

madrotor

Hello guys, I just finished modifying the siphon assembly.
so I found that the drill method is a bit of a "FAFF" due to firstly how long the actual assembly is against the drill bit and secondly due to the shavings left behind so I decided to use one of my TIG filling rods, after doing a rough old school calculation I came up with the new diameter (1.717mm) , my Stainless TIG filler rod is approximately 1.8mm so close enough, I heated it till it was red hot and went to town, it literally took 3 secs of pushing it through that orifice and it leaves a smooth surface behind it so no need to clean anything and no flow hindering should occur due to rough surface caused by drill bits.
I hope this helps
the depth of the orifice across to the other side is only few millimeters there after you can actually feel the spring of the pop off valve which I have melted as per MM thread.
Thank you Brett for your input.

Orifice enlarged to 1.8mm

Bit of an old school calculation and the TIG rod that i used

TeamRX8

iTrader: (25)

you could have gotten many paper napkins out of that wooden one.

TeamRX8

iTrader: (25)

You don’t have to go to a fuel cell. You can however rework the entire fuel system in it depending on how extreme you want to get. Unfortunately nobody is really offering a full PnP except in Japan, but it still uses two OE S1 pump modules which I’m not a fan of and like anything else from over there has a grossly inflated price. The S2 pump module is a bit of a pain to swap in, but at least all the internal components are available as separate replacement and it’s just a better design on multiple levels. The pump options are a bit more limited due to it being a 65c configuration. Which on the S1 module replacement parts aren’t an option per my previous comment.

madrotor

hahaha yes Team, I guess we need some napkins these days

Blackwell

I am not going extreme at all. I was more curious whether people were changing from the returnless to a looped system. I had noticed when tuning I was getting a lean spot for a split second right when my secondaries were coming on and I knew I was emptying the rail. Fortunately I'm only running .4 bar boost right now so I am just running my primaries up to a higher duty cycle and not having to transition.

madrotor

Hi Brett, the initial diameter was 1 mm or just a tiny bit above since my 1mm filler rod slid through fairly easily,
for stock pump @ 115LPH as per this forum ( I might be mistaken ) diameter for the orifice is 1mm Area = 0.785 mm2
for uprated pump @340 LPH the flow increase factor is 2.95 , so the assuming ( I know assumption is the mother of all failures ) that the area of the orifice should be big by the same factor to accommodate the increased flow , The new Area should be 2.95 x 0.785 = 2.32mm2 , R= SQRT( 2.32/pi) = 0.85mm
D= 2R= 2x0.85 = 1.71 mm

Brettus

iTrader: (2)

ok ...but what I actually said was 2x the area of existing ...which makes it 1.4mm diameter. You have made it over 3 times bigger. It might be ok but you will need to check that the siphon still works. Other than a road trip on flat straight road ....i'm not sure how you would do that.

Brettus

iTrader: (2)

Edited first post to include madrotor's method and correct sizing .

TeamRX8

iTrader: (25)

ok, well the only reason for a fuel cell imo is to have a smaller tank. I just wasn’t sure what your goal was.

.

Blackwell

Totally. I was thinking if I had to go looped with a regulator up by the fuel rail it was gonna screw up the siphon. In which case I'd put a cell in the trunk instead of having a dead side of the factory tank.

Blackwell

I am in the process of doing this but I have to disagree with the size madrotor has because Im putting a piece of 0.030" welding wire through that hole and its maybe got a thousandth of play. When I measure it with my Calipers they say the wire is 0.78mm. I'm thinking that hole is around .85mm. I ended up removing the pop off valve altogether and Just went down through the top with a 1/16" drill bit. It came up as 1.58mm on my calipers.

If you drill through the top cap you can pull it off and remove the spring and plunger.


Then I cut the top off on the mitre saw.


The plunger sits on a 5/32" hole. This pic is after I tested my screw in there first time. This is also the stage where I was finally able to get deep enough to get through the siphon hole with the 1/16 bit. It was very short.


These are the screws I ground down to block the hole.



Little dab of JB Weld for insurance. The shank was a tight fit so I bet would've worked fine without.


You can totally check the siphon still draws using compressed air. Its impressive how hard it sucks on my finger. I think you would have to go equal to or larger than the draw line in hole size to actually stop the siphon from happening.

Cheers

slash128

Just an aside, there is a small hole on the side that you can use a small flat head screwdriver to pop off the cap from the inside without drilling it. I just installed a DW200 and this is how I popped the cap off to glue it from the inside.

madrotor

Good work mate,

I think the issue is these things weren't made the same some differences are to be expected, your approach maybe required removing the assembly, I didn't want to give myself more work than I needed
Looking at the design anyway, The venturi pump should work as long as the orifice is smaller in diameter than that of the pipe enclosure, that orifice only serves the purpose of accelerating the fluid enough to create a low pressure zone on the exit side which in turn sucks the fuel from the other side, at full tilt the 340 lph will flow far more fuel at the same pressure so this should compensate if anything the pressure differential should be a tiny bit lower but not by much , time will tell for me anyway , I am yet to try it because I am still not done with my build, I should be able to report back on my work soon enough.
Thanks for sharing your work

Blackwell

I totally agree with this. Thought it was a bad design until I tested it and realized how effective it was. The popoff valve is the weak link.

I wasn't 100% sure what I was looking for until your post so cheers to that.

Part of me is starting to think that pump duty cycles are really whats gonna control fuel temperature though. The siphon does just recirc into the bowl. I wonder if increasing the return amount from the regulator and decreasing the colder fuel from the other tank will be an issue? I know mazda had the 2 stage relays, maybe that was heat control more than noise. I know the Haltech has a pump duty map, I'm not really sure how to use it yet. If one could just turn down the pump duty at idle and low MAP cruising would that make this siphon mod unnecessary? Brettus?

Brettus

iTrader: (2)

Yeah ...that's a definite possibility. The biggest issue is when fuel usage is at it's lowest.

RotaryMachineRx

iTrader: (1)

If you wanted to fill your curiosity still, I went to a return style system by modifying/gutting a stock S1 assembly (check out my REW thread) and running a return line back to assembly. It wasn't ridiculously hard but it really only makes sense if you are going to install aftermarket rails/regulator that will support a return line; which turns this into a much more expensive/"extreme" mod than just a direct pump swap out with some slight mods.

I still think the methods you guys are using make the most sense on a boosted Renesis, it's the same I had on my Greddy setup for years using DW200.

madrotor

I think that the fuel in the bowl is more so the issue because the cycle it goes through continuously is what produces enough heat for it to boil, the fuel sucked in from the other side is going to be the cooling agent but since the flow of fuel sucked from the other side is controlled by the efficiency of the Venturi system there is very little that can be done there, I believe that increasing the area of that orifice is going to aid significantly in decreasing the temperatures because the flow will be higher which will decrease the time the fuel spend under pressure before it is returned to the bowl. Again it is all so far a theory for me because I am yet to fire up my car with that setup.