autoxgt

Has anybody considered running a High volume pump (any brand) to a 1gal. expansion tank?
There are a few local Miata guys that run that style set up.

They run Bosch/Walbro pumps in the stock tank which feeds a 1gal. expansion tank that has an overflow line back to the stock tank. They run a stock fuel pump in the expansion tank to feed the fuel rail. I believe the the return line from the fuel rail returns to the stock tank.

dannobre

iTrader: (3)

I'm sure we all have

...usually you use a LP pump to the "sump" and then the HP pump from there to the fuel rail.....

Basically the biggest problem is where to put it...and is it legal in whatever class or series you race in.

I tried to keep whatever solution I used inside the fuel tank if possible. I just don't want an external fuel system inside the car without provisions to seperate from the drivers compartment. I think I would just go to a fuel cell if it came to that

sblethen

iTrader: (3)

We are not allowed any type of surge tank or additional fuel cell. However fuel filters are free, can be added, and can be put anywere along the fuel line that you want We are still thinking up a few ideas to get a bit more fuel in the car that meet the letter of the rule as written


Stephen

dannobre

iTrader: (3)

Use a couple of VW fuel filters inline ...they must hold at least a litre each

RNS11Z

So I have run into this problem recently.
I am trying to understand sblethen setup. Could someone please explain his 2nd pump set up?
Is there anyway of overcoming the fuel surge issue with our running a return line and surge tank?

sblethen

iTrader: (3)

You can simply add in a low pressure pump with a hose that runs to the drivers side of the car. We also added a gauge to that side with a switch to turn off the pump when he fuel on that side was low. Remember pumps cool themselves by pumping fuel...

sblethen

iTrader: (3)

FYI we just completed the "devil in the Dark race at NJMP using the above "solution" using the 09 pump on the drivers side with a low pressure pump on the right side. We could run 66minutes under green flag or about 41 laps at NJMP until we sputtered... We do fit in a bit of extra fuel because of the dry break system. If anyone has questions now or even 5 yrs from now doing a search and finding this thread just ask!

Stephen

airman90

I am about to finish a rew swap and my biggest concern is fuel. I thought about dual pumps. one on the right side and one inline to feed the engine. But the real question is. How can this be done. Is there any sort of access to the right side of the tank to drop a fuel pump in there

dannobre

iTrader: (3)

Have you gone to a return systen with the REW? If you have it changes things. PM me if you want and I will go over it with you...

If you stay return less the right side ofbthe tank has an identical port to the drivers side..and uou can drop in an OEM pump with just the plumbing and a plug rewire

TeamRX8

iTrader: (25)

are you even reading any of these threads? The reason nobody responds is because it has all been discussed and even the post before yours says to email him if you have questions.

airman90

pm'd

RNS11Z

So our solution to this is to use the s2 fuel assembly, utilizing the Walbro fuel pump. Comparing the 2 units there are significant changes to help reduce fuel surge. I will update the results after next weeks races.

H

skc

Look forward to seeing how your set up performs. Walbros of late have been quite unreliable. I will probably end up with a S2 swap.

I found that I only encountered starvation below 1/4 tank usually of high speed turns at the track

RNS11Z

Got the car running. With out touching the tune it runs considerably richer. On the dyno it made a few more hp as is. We will adjust the tune next time. You notice the richness on idle too.

Will post results after this weekend

H

RNS11Z

Well this set up definitely works!! No more fuel surge. Ran the car down to 1/4 tank and it ran mint!

blu3dragon

iTrader: (1)

Good info here. I thought Mazda had resolved this in the s2, but I guess they just improved the situation a bit. I experienced engine cut out on the track this past weekend once I got down to 1 tick over a quarter tank with a 2010 series 2 sport, stock engine, coilovers and 255 width Direzza Z2 tires. When I came off, I was able to add ~10 gallons of fuel, so ~5 were left in the tank. I guess I am using ~4 gallons in a 20-25 minute hpde session so I need to fill up every 2 sessions in future.

Last time at the same track I did not have any issue and actually ran until the fuel light came on. This time I was bit faster, carrying ~5 mph more through a high speed left followed by another left. It seems that was enough to trigger the issue on this particular track (it happened twice in the same spot but I had no issue anywhere else including a long, left, banked sweeper).

TeamRX8

iTrader: (25)

A common misconception is that you have to locate the regulator at the engine and pipe the return from there all the way back to the tank. You can instead easily tee the regulator off the fuel line back at the tank and dump it in back there instead. This would be similar to the OE system except external of the tank rather than internal. You could still use a low pressure transfer pump on the other saddle and reconfigure the OE pump assemblies to eliminate the internal bypass.

dannobre

iTrader: (3)

The issue is more about where the fuel goes back and how the OEM pump picks up same. The returnless system like stock results in much better fuel conservation in the pump assembly and this needs to be addressed if you change it. Otherwise the higher output pump just pumps itself out of fuel faater than OEM and makes things worse.

So for fuel needs close to OEM you would be better with a stocklike system...and when you need significantly more you need to be careful how you implement it, otherwise it can be worse than stock in corners due to slosh

TeamRX8

iTrader: (25)

That's where reworking the OE pump assy comes into play

dannobre

iTrader: (3)

LOL.....tried it a few different ways.....and the OEM system was just as good as how I did it

The problem isn't getting fuel to the engine...it's a problem keeping fuel in the pump. Upgrading the pump is useless in some respects because it doesn't solve the problem unless you have run out stock fuel capacity.
A bigger pump helps if you are close to the limit because it allows the siphon to work more efficiently.....at the expense of emptying the stock pump enclosure faster....and that is the tradeoff. I found a bigger pump and no provisions for slosh can make the problem worse.
There are a few things that you can do to help the slosh issue....and most of them are OK for the rules.... Speedsource reworked the tank to solve the issue...but it's kinda expensive

Solved the problem completely but it wouldn't be applicable to most of the racing rules, and it is complex. If you have the option...a fuel cell would likely be the best bet if it is allowed.

TeamRX8

iTrader: (25)

You just need a new custom housing assy is all. There are too many components displacing bowl volume on the OE assy, plus it isn't designed to the maximum potential volume capacity overall either.

dannobre

iTrader: (3)

I reworked the OEM assembly fairly extensively ( removed the fuel filter and made a cuatom top for the cup etc etc etc )...and looked at making a different enclosure with more volume. Not an easy task...and after thinking about it a lot I decided against going that route.
I was going to install a flapper type slosh box in there..and getting it in is the big problem. I enquired about getting a custom one made from fuel cell material...and the cost was crazy for what I was looking for.

Another problem is getting fuel into the assembly fast enough when it is available....(as the stock entry is limited) and keeping it in when there is no fuel around the base due to slosh

TeamRX8

iTrader: (25)

I thought you have a transfer pump in place of the siphon pickup?

dannobre

iTrader: (3)

I have both.....for street driving the transfer pump on the passenger side will run dry if the tank gets below 1/3 tank...so I shut it off...and the siphon will still return the fuel

For on track the pump is on...and slosh will keep the fuel on both sides relatively equally so both pumps seem to get fuel

I installed a 5L surge tank in the trunk with a Bosch 044 pump and haven't had an issue since....the stock pumps get every drop and the surge is big enough that it holds more than enough to keep things happy down to almost dead empty

Like I said though...not an available option to most of you...easier to just keep the tank fuller

TeamRX8

iTrader: (25)

I suppose the more I think it through the more two low pressure pumps in the tank feeding an external fuel filter with the external high pressure pump pulling from the bottom of it makes more sense