I make this information public even though it isn't 100% tested and proven . The last attempt at a solution claimed that it worked and time has proven that it did no such thing .With this I'm saying ....."I did this , and got a good result " and make no claims that it will be the solution to your particular problems ...........although it may well be .
I would like more people to try this under various conditions to verify that it works as I don't have the inclination nor the resources to test it as thoughroughly as it needs to be.
Indeed ... the design I came up with could be refined substantiably as much of it was guessswork and I only got to try 2 iterations .
Problem I was having:
Running 350whp(16psi) , when at approx. 1/3 - 1/4 tank and less , exiting high speed corners (either side) and nailing the throttle i would get fuel starvation .
With this modification I can do the same thing down to when the yellow light comes on ...................without starvation!!!!!!!111111111+++++++


Anyway here goes ..............................

 

1/Step 1 under review .....


2/Remove the flapper valve at the bottom of the bowl and open up the 3 orifices as much as possible such that the flapper still covers the hole .

3/Fit upgraded fuel pump (suggest DW 200 ) and melt the top of the popoff valve per that "other" thread. Note ....you only need this for applications over 300whp.

4/Make surge tank as shown from medium wall,flat bottomed HDPE container about the same height as the stock fuel bowl. Mine is diameter 175 x 95 high . This is as big as you can go without interferrence from the indentations inside the tank . Slightly smaller would actually be better i think.
Drill 8 x diameter 5mm holes just above the bottom equispaced about the circumference.



5/
Squeeze surge tank through the fuel tank opening and fit pump assembly into surge tank. Not as easy as it sounds .............. but if you got this far , shouldn't be a problem.
There are upstands and a solid bracket inside the tank. Those plus the spring pressure from the fuel bowl should stop the surge tank from moving around when cornering .

6/reconnect and enjoy

 

It'll be a while before I can make an attempt, but subbed for future reference. Thanks! Hope it continues to work for you.

 

Good right up!! so in the large black bowl, are the holes on the bottom near the outside edge?,

I was kinda of thinking along the same lines of adding in baffolds, this is ingenious to that same concept.

 

The holes are on the outside at the bottom, i drilled through from the inside so they were as close to the bottom as i could get them . You can't see them in the pic , probably because it's black, but they are there .

 

Correct me if I'm wrong -- so conceptually, you have basically enlarged the volume of the fuel bowl, right?
The fuel from the integrated fuel bowl bleeds out into your enlarged bowl and cannot slosh away.

 

any particular reasons for the hole sizes and halfway height of the holes on the stock bowl?

 

It was a bt of a guess to be honest . I wanted to still allow the fuel bowl to work as it normally does when the tank is near empty - so you don't run out of fuel under mild acceleration when there is still several litres left in the tank. But at 1/8tank (yellow light)the fuel level in the tank is about half way up the bowl , so with the surge tank there , fuel will flow back into the bowl under cornering and acceleration through those holes . I think you could drill the holes a bit lower if wanting to get the most from an NA car - don't really know though because there are so many variables that come into this like :
How many g's are you pulling under cornering,braking,accceleration.
How quickly the surge tank drains ,
How quickly the fuel bowl drains under power
How much siphoning is going on to get fuel from the other side
How much air is displacing fuel from the bowl through the siphon
What sized fuel pump you have and how that affects siphoning
How hot is the fuel
Where are the holes and how big are they in both the fuel bowl and the surge tank.
I could probably double this list ............

The concept works , but getting the absolute best out of it in every situation will take lots and lots of experimentation.

 

Essentially yes . But also tried to retain the ability of the system to use all the fuel in the tank before running out .


otherway around . Fuel flows back into the stock bowl from the enlaged bowl when the stock bowl would otherwise have run dry.

 

I tried something similar....I found it helped a bit...but I still had problems in the long sweepers at around 1/4 tank. Going to a return system is worse..it empties out the cup faster than a returnless system

The black cup will act as a baffle only...it will not stay fuller than the fuel level in the drivers side tank...so it won't solve as many issues as you think. You still need to deal with the fuel slosh between tanks...and the lack of return to the drivers side when the siphin isn't working at high fuel flow levels

I still stand by my comments that the only thing that works without issues is a surge tank if your rules allow

 

This is why I didn't want to make extravagant claims about how well it works . But for many of us , I believe it offers a significant improvement .I also think, given enough R&D there will be a design that works almost as well as an external surge tank.

 

For street driving I think it will work....Track driving I would just go to the surge tank and be done with it

I designed a number of in tank surge setups...and due to complexity never bothered to try them...I have no rules constraints that need a stock or in tank fuel system

Good luck...I hope you figure something easy out that I missed

 

I agree . However , I don't want an external surge tank in my street car for a number of reasons . Some guys have been refilling their tanks at the 1/2 level , hopefully this mod will allow them to at the very least run down to the 1/4 tank level and possibly lower.

 

Yeah ...about that ................
I realised pretty early on in the piece that he didn't and was one of the few people on here that would challenge him . He had a way with words however, that few others could match ,so on most occasions he was able to convince the majority that black was white . Much to my frustration at the time .

Thanks for the encouragement .

BTW : that DW300 fuel pump I bought off you .............. totally the wrong thing for our cars . Wish I had gone for the DW200

 

kind of disappointed, thought you were adding more flapper valves or something similar which is likely what's needed for competition/high-G cornering

otherwise Dan and I had discussed something similar a long time ago. The issue is getting fuel in "and keeping it in", unfortunately drilled holes let it back out

but if it works for your situation then I guess that's good enough for you

 

I looked at doing that but couldn't work out how to get it in the bowl without the flapper shaft hitting the bottom of the tank. I did , however , port out the existing flapper holes as much as i could which I'm sure does help.

As far as the holes letting it back out ................ the positioning of the holes does have some bearing on that . What I can tell you though ,is that without the holes , it doesn't work . That was the first iteration I tried.

There is a good reason Mazda redesigned the siphon assembly for the S2 and when my first attempt didn't work I realised what it was ........................

 

The best in tank idea I came up with was a fuel cell fabric enclosure with 3 flapper valves that the stock pump enclosure sat in. The fabric was flexible enough to scrunch it up and get it in the tank.

Wasn't going to be cheap though :-(

If you put in a passenger side pump and the excess stays in your extra cup that would help as well.

 

Mine did cost me $37.00 . But with that I got 5L of oil so .... not too bad . LOL


By the time the tank gets down to 1/4 full , there is no fuel on the passenger side to pump . It would get rid of air by eliminating the siphon but I think my design addresses that issue anyway .................

 

Damn...must be good oil ;-)

 

probably not in kiwiland

 

Nope ............. good oil is $70-$100+ for 5L

 

Worth a try. The last few track day I did was run with full tank of fuel in fear for starvation at the track. As this can be detrimental on a FI car. However, the weight penalty of driving on a full tank is slower lap times.

 

So theres nothing like this available to buy for RX8?


FEED Intank Collector Tank FD3S - RHDJapan

 

rather than drilling the 2 holes towards the rear of the car, won't it be better if the holes are on the driver side?

Posted From RX8Club.com Android App

 

Couldn't say . My logic for drilling them there was that the least g's ever experienced are toward the rear of the car .
It might even be best to drill a series of holes all the way around the bowl so that it refills quickly from any direction.


What I did solved my problem ...........

The reason the bowl empties on the stock setup is because, at 1/4 tank, air from the siphon displaces the fuel in the bowl . It isn't due to g forces ! Once people realise that they will understand why this idea works.