Brettspeed Fuel Pump Solution - FI on high speed corners
#101
Hybrid Greddy Boosted
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.
#102
^- 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.
#103
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.
Last edited by Brettus; 09-29-2014 at 03:39 AM.
#108
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 .
Last edited by Brettus; 10-01-2014 at 04:56 PM.
#112
Driving my unreliable rx8
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.
#113
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 .
Last edited by Brettus; 10-02-2014 at 02:39 PM.
#115
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 .
Last edited by Brettus; 10-05-2014 at 03:18 PM.
#116
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 .
Inner bowl is a neat fit , which should decrease slosh from one side to the other .
Last edited by Brettus; 10-06-2014 at 02:36 PM.
#117
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?
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?
#118
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?
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?
#120
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.
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.
Last edited by Brettus; 01-29-2015 at 01:27 PM.