JimmyBlack

Have you tried re-installing one of your old "bad" pumps? This would work to rule out the pump install/removal process from causing your issue.


While the fuel starving issue appears to be pretty common, it also seems that some rx8s are more prone to it than others. If this were the case it'd like me either mechanical or electrical variation between each car. If a mechanical variation existed in the tank it could explain why some have experienced improvements with swapping to a different (s2) assembly while others haven't observed any improvement. On my S1 I haven't experienced fuel pressure drop at any time except when doing donuts with the petrol light on. Having said that, I don't track my car that often to induce sustained lateral Gs.

slash128

^- This is curious to me as well. While I only recently installed a FP gauge I could tell indirectly via AFR gauge that I had enough pressure to satisfy needs while doing WOT pulls around and slightly below 1/4 tank. I tried to avoid it but Since installing the FP gauge I can say the pressure stays within +/- 2psi or so as low as 1/8 tank.

Brettus

iTrader: (2)

That has never been an issue for me either . Once it gets below the orange light level it started to be a issue after i fitted the DW300 .

Try it again when you refit the turbo .

Running dry is a matter of getting the wrong combination of several factors . It only becomes an issue once you go below 1/4 tank . At that point one side of the tank is dry and the level in the other side goes below the height of the bowl.
At this point several other factors come into play :

fuel pump size ... The bigger the pump the worse it gets .
fuel flow
cornering Gs
Acceleration Gs

You could avoid any issues by always keeping the tank above 1/3 at all times . This thread is only for those that are not happy with that compromise.

slash128

Aye, gotcha. I though I was doing it wrong

Brettus

iTrader: (2)

Think I've cracked it ...who thinks that being able to run down to the E on full throttle at 15psi while cornering at the limit................. would be worth achieving ?

RotaryMachineRx

iTrader: (1)

Let's hear it!

RotaryMachineRx

iTrader: (1)

Yeah depending on how long my car is off for i will see it drop to about 45psi

Brettus

iTrader: (2)

I've gone back to the inner bowl with no holes in the side and modified the siphon assembly . Hope to get the car on the track soon to prove it in extreme conditions . But the run last night on 'E' for ENOUGH was a good indicator to me that it's working well .

dannobre

iTrader: (3)

Hope it works.....i could run it on the street down to the light....but on track i never got it to work well enough to trust it with a boosted application

Brettus

iTrader: (2)

I'm going to rig up my fuel gauge alarm so it triggers a boost dump so I don't have to keep looking at the fuel pressure gauge

dannobre

iTrader: (3)

I have mine set to hit the rev limiter setting.....and the low level on the Water/meth and low oil pressure does the same thing.

Makes figuring out problems interesting sometimes ;-)

logalinipoo

I know you have something that's working, but have you thought about a tee in the hose to the siphon and a plug that you can drill a hole in to bypass the extra flow caused by the DW300.

Brettus

iTrader: (2)

Was considering something like that till I realised that the extra flow would be benefficial if the right mods were made . I'm prettty sure that the fuel level in my inner bowl is now at the top of it vs before it could only ever be at the same level as what was in the tank.

I'm noticing that the pressure under WOT is now a lot more stable as well for some reason . Possibly related to the fact that fuel is no longer spewing out the popoff valve any more .

4DRcoupe

brettus, let me guess...you drill the siphon venturi hole bigger? i'm not refering to the return hole.

Posted From RX8Club.com Android App

Brettus

iTrader: (2)

As far as I can tell from the thread 'the guy' drilled it out to !/8" (3.2mm) which is way too big .

The venturi hole itself is 1.0 mm .
I drilled it out to 1.5mm which is just over double the area . But I have also more than doubled the flow through it with the DW300 .
I also modified the nozzle at the bottom of the bowl to flow more . End result is the venturi still works .
It has solved all of the problems i was having for street use ...
However,I tested the setup on the track a couple of days ago and regret to inform that I still got starvation at 1/4 tank .
I think my outer bowl is draining too quickly ... going to try another design .

Brettus

iTrader: (2)

Latest outer bowl design ..... drains out really slowly and fills up very quickly at any fuel level above the orange light . That is the theory anyway . Also is held in place nicely by obstacles in the tank. V cut goes towards rear . Has a flapper valve in the side and really small hole either end so i can run the tank right down if i need to.
Inner bowl is a neat fit , which should decrease slosh from one side to the other .

4DRcoupe

brettus, how's your version2 outer bowl doing?

I've just done a track day and with the outer bowl, i could go until fuel is about 1/3 and no starvation issue. wanted to push to 1/4 level to test but my rear pads are toasted.

fuel pressure is holding at 58psi and above.

is it normal that fuel pressure will be higher when fuel is cold compared to when fuel is warm/hot?

Brettus

iTrader: (2)

Have not had the chance to test the mk2 at the track yet .

FazdaRX_8

iTrader: (1)

its spring over there make it happen!

Brettus

iTrader: (2)

Went to track last weekend hoping to try the mk2 setup .
As I was pulling out of my garage I remembered that 1/2 full bottle of synthetic premix I had that's been sitting around for over two years . So I grabbed it and dumped it in the tank when I filled up.
Big mistake !
With fuel at 7/8ths of a tank I started to get fuel starvation . By the 4th session I could barely accelerate and even got passed by an N/A 8 . On the way home it died completely twice but restarted after 10 mins or so both times.
Pulled the pump apart and found the lower filter had a film over it that was restricting flow so bad the pump could not suck any fuel through it at all!
Did a search of the net but couldn't find any other mentions of this kind of thing happening with old premix.
Hope to get back to the track within the next month or so for another try.

logalinipoo

I dont remember where we talked about it so heres those bits.

dannobre

iTrader: (3)

That sucks.....can't imagine the pre-mix would go bad....

Is the pump OK?

TeamRX8

iTrader: (25)

Pouring oil in and then pumping gas in after and assuming it will mix is a big mistake.

Brettus

iTrader: (2)

seems to be fine . I would not have imagined that would happen .



And as far as the dump and pump comment from Team ... I did that exact thing for about 6 years and never had an issue .

swoope

iTrader: (5)

i said this a long time ago. dont forget to premix the premix.. if you have to dump and go, dump after the fill..

beers