logalinipoo

So would repositioning the siphon outlet cure the problem.

Maybe lay the siphon on its side where the outlet is at the top and air does not bubble fuel out of the bowl.

Brettus

iTrader: (2)

You mean ..............like Mazda did for the s2


There is little doubt that the s2 assembly works better than the s1 . So why not just buy an S2 assy ? The issue for me was that I would still have to upgrade the pump as it wouldn't flow enough, and there are lots of unknowns around that . Plus , I think this idea will work better anyway..............

logalinipoo

Ahh ive never seen anything on why s2 was better. Just a bunch of people saying it was.

4DRcoupe

hmm...i will try this before my next track day. now the difficult part is to find the correct size 'outer bowl'...

without the outer bowl it won't 'work'?

Brettus

iTrader: (2)

It might help at 1/4 tank but below that I doubt that it would work as well .

The whole point of the outer bowl is to allow fuel to flow back into the inner bowl while cornering and accelerating - buying time . If that bowl was not there but the holes were , I'm pretty sure the holes would be uncovered a lot of the time once the tank gets down that low .

slash128

Nice work Brettus. It's good to see people like you experimenting. If it gets you the results you were after then I say it's a success!

TeamRX8

iTrader: (25)

I still say the S2 pump with a kenne bell boost a pump or jms fuelmax frequency controller is the best option since you can tie the pump output control to a boost signal rather than recirculating heavily with an oversize pump.

Brettus

iTrader: (2)

Who has tried it ?
I read the info on the kenne bell site . I couldn't see how you could get the duty cycle to ramp up like they are saying when all it has for a sensor is a pressure switch. Surely that just means on or off ?
Also : They say there is no problem boosting the pump output 75% - do you believe them on that ?

Looks good though ....wish I had seen it earlier.

FazdaRX_8

iTrader: (1)

I just read it too,

the only thing I can think of is the following, examine the second graph the pump is pegged at 17v so the boost-a-pump is "on", the duty cycle could increase as the flow increases given the same pressure that the graph indicates.
so as the Duty cycles on the injectors increase, so would the pumps need to pump more at the same pressure. labeling the graph as duty cycle is odd I would call it flow.

so that makes sense to me, I think this could work great, seems someone could rig something up though, like take our resister and make it decrease resistance.
or even take the High Pump signal away from the ecu and connect that to a hope switch, so if you go into boost the High pump mode fires up.

Brettus

iTrader: (2)

But our system doesn't work the same way as a mustangs which is what they reference .... Pressure on our system is controlled by the relief valve and pump is operating at its maximum duty cycle at all times , albeit at reduced voltage on the first stage.
So If i'm reading how it works correctly , on our system when it switches over it will switch to 100% duty cycle at 17.5V !

Which still might be a better scenario than what we have with a larger pump ................. but could lead to premature pump failure .

FazdaRX_8

iTrader: (1)

you are right we are stuck with the regulator at 60psi or so right?

the same idea though, if you had 100% duty cycle on the injectors and a fuel pump that can keep 60psi at say 70% of the injectors duty cycle, then the pumps flow would decrease and hit like 40-50psi at 100% injector duty cycle. there idea is get more voltage to the pump so it spins faster harder. to make up the difference. which probably would lead to premature pump failures.

we don't seem to have the pump problem, we are pumping enough fuel well with upgraded pumps in S1 assemblies
The issue is there is no fuel around the pump to pump, lol
which is what your mod addresses

team is suggesting a S2 pump assembly as is no walbro or dw200 or whatever, just the increased voltage from a booster to get it to pump more.

FazdaRX_8

iTrader: (1)

TeamRX8

iTrader: (25)

Here? Nobody, which is no surprise.

Plenty elsewhere on similar pumps as ours. Some of the replies following yours indicate a lack of understanding. The relief valve is like any other regardless of it's location If flow from the pump exceeds demand then it is diverted by the relief. If not, you will see fuel pressure drop below the relief pressure setting.

I personally prefer the JMS version, though it is more expensive. It has timing controls for ramping up from the setpoint rather than simply on/off. I'll have one on my E85 NA system.

Brettus

iTrader: (2)

There is a good reason for that ......................................... people (including myself initially) belived MM.

TeamRX8

iTrader: (25)

well he was trying to sell pumps/assemblies

from what I've seen my gut is to pay the higher price of the Fuelmax version

that said, from one of the most knowledgeable people on RX7Club: Kenne Bell Boost A Pump - RX7Club.com

just noticed some news about a new MSD unit in the link above, hmmmm


.

TeamRX8

iTrader: (25)

interesting

Programmable Fuel Pump Voltage Booster - 2351

edit: appears to be for FI vehicles only since it uses an internal boost line signal device


.

Brettus

iTrader: (2)

Yeah that does look like the best option but I'm leaning towards going back to the Walbro (from DW300) and calling it a day.

As an aside : I just did a little test to confirm a suspicion I had that the DW300 pump I fitted was something to do with my hard start on cold mornings issue .
When the engine is cranking the pump switches to Full speed mode ,with the DW 300, pressure shoots up to 68psi ! So .....too much fuel pressure at startup ! The same effect happens (to a slightly lesser degree) when the full speed mode kicks in under load ,causing overly rich mixtures .

I removed the high speed relay a week or so back and cold start issue has gone . Plus there is still plenty of fuel so .....this pump is too big and was a real bad idea !

Rotaman

Also says on there under specifications that it is only to be used on systems with a return line.

I would certainly be very cautious running more then 16v into anything for more then a few seconds at a time.
I'm sure you may be able to run more voltage into the fuel pump, but possibly at the expense of fuel pump life. It may not last very long running those high voltages for any time period.

Rotaman

FazdaRX_8

iTrader: (1)

What where your symptoms of high fuel pressure cold startups?

Brettus

iTrader: (2)

Took ages to start , sometimes wouldn't start till i put my foot hard down on accel. I originally thought it was a map i had altered in ME that fixed it but then realised the fix coincided with removing the high speed relay.

4DRcoupe

when does the pump go into high speed mode? during open loop?

Posted From RX8Club.com Android App

logalinipoo

I have the 300 and it starts just fine. No difference that i can tell.

I have noticed when i turn the car on the pump pressures up then shuts off. Once my gauge boots up i show 55-58 psi.

FazdaRX_8

iTrader: (1)

thanks brettus, I have been experience the same kind of issue, it turns over several more times then normal, I will try to pull that relay and see if it starts better, I think it has to do with new motors. it always starts though and vacuum is good, my fuel gauge reads higher like 65-70psi

Brettus

iTrader: (2)

doubt the walbro does the same thing as it doesn't flow nearly as much. I'm not sure now - maybe is was the change to the crank fuel map that fixed it ....... more testing needed.

65-70psi sounds high though does it increase in pressure around 4000 when in boost ?

TeamRX8

iTrader: (25)

We have a very short return line called a bypass. They are referring to fuel systems that are return-less with no bypass. The flow and pressure on those systems is controlled by pulse modulating the fuel pump by the ECU. I guess you didn't understand this in the parentheses at the end of the warning you're referring to