Returnless Fuel Systems - what is the limit?

[XSRCivic]

Originally Posted by soxfan143

Well from what I've read on the Boost a pump it uses a vacuum reference to know when to up the voltage to the pump. So at idle the fuel pressure will remain at the stock pressure and once the boost a pump sees 5psi+ it will up the voltage accordingly. Now my question is how does it know how much voltage to add to keep the fuel pressure from spiking all over the place? Once 5psi hits does it increase voltage in increments or does it just jump right to the max 20v?

Check this out...

http://www.kennebell.net/techinfo/ge...heory_kens.pdf

[soxfan143]

Originally Posted by XSRCivic

Check this out...

http://www.kennebell.net/techinfo/ge...heory_kens.pdf

I read that already. But it doesn't really say if it gradually increases voltage or not. And does our fuel pump reach 100% duty cycle when we are WOT and will increasing voltage do anything. The Fords use fuel pump speed control in their base ECU operation. I don't think Honda does this. So I'm not sure of it will operate like it would on a Ford. I'm only throwing out questions here to make sure it will even work with our cars. I'm sure it will but just being cautious.

[Hondata]

I have been using a Boost-A-Pump on my Acura RSX landspeed car with return line fuel system for two years. Here are some of the facts as it pertains to my 700 + HP twin supercharged K20.

- I have run RC 1200cc and 1600cc injectors
- I run a stock fuel rail
- I run a stock fuel line from the tank to the fuel rail
- I use a Walbro 255 high pressure pump with the static pressure set to about 45 psi
- The superchargers take 120HP to drive at about 25 psi - thus my 700 WHP car is making 820 at the crank.

With the Boost-A-Pump not connected the fuel pressure starts dropping at about 450 HP. Connected the voltage is 18V, and the pump spins much faster maintaining fuel pressure at peak boost to the redline.

For the same amount of work, a higher voltage (within reason) will lower the current - and it is the current that heats up the motor coils (= less reliability)

I run the Boost-A-Pump permanently at max voltage. For a road car the pressure switch simply switches the Boost-A-Pump between battery and its higher voltage. The fuel pressure is set by your pressure regulator, so at the 400HP level on my car the fuel pressure is the same no matter if the Boost-A-Pump is running or not.

At the 500 HP level the fuel pressure is higher with the Boost-A-Pump than without as the Walbro is spinning faster and can deliver the fuel the engine needs (think in litres per minute).

Something to think about is that as the pressure rises the fuel pump cannot deliver the same volume of fuel. Tech - Fuel Delivery

In a test earlier this year I was running out of fuel with the 1200cc Injectors - so I bumped the fuel pressure by 10 PSI. The result was that at the top of the rev range the fuel pressure dropped. So I lowered the fuel pressure back and installed 1600 CC injectors, made more power and maintained fuel pressure to the redline.

[soxfan143]

So basically you're saying that the boost-A-pump will work very well on a boosted Si not wanting to run a return line. Or would you recommend a normal return setup over this?

[PanamaSi2007]

Originally Posted by Full-Race Geoff

great question! thats what the boost-a-pump is all about -- take a look and read up if you have a minute Kenne Bell Boost-A-Pump

the fuel pressure would not be increased at a 1:1 rate like ideal, but this is a returnless system so that is not an option!

I understand the idea of installing an external FPR (return system) is precisley to increase 1:1 under boost. With moderate boost 10-11 psi or lower I beleive an external FPR is not so required.

[PanamaSi2007]

I have also heard that those Bosch intank pump are noisy.

[Hondata]

Go to time index 1:05 on this video YouTube - Flashpro Race Calibration and watch the next two minutes about this supercharged Civic Si.

The following comments will now make sense.

When we tested the fuel pressure on the exit to the tank, the pressure drop was 5 psi, so the remaining 5 psi was lost along the stock fuel line.

At most, the Boost-A-Pump might add 5 psi to the fuel pressure on a stock fuel system - for this supercharged example and then only at the top end of the power curve. Edit. The word add is incorrect. A better description would be prevent from dropping.

For supercharged S2000s running in the mid to high 300 HP level, the boost a pump adds 1/2 a point AF ratio at redline - in the last 500-1000 rpm. For the S2000 owners seeking more HP I recommend a return line system.

[soxfan143]

I've watched that vid like 100 times. lol..While I was waiting for FP to release. I completely understand the theory behind fuel pressure and the drop off from positive manifold pressure. I just want to know if the Boost-A-pump will keep my fuel pressure constant at about 14-16psi if I have a Wlabro 255 and a crushed FPR from a CT-E kit.

[Hondata]

The Boost-A-Pump will not keep your fuel pressure constant in the stock Civic Si returnless fuel system. In the example of our supercharged Civic you lose 5 psi from the fuel pump to the connector on the outside of the tank and another 5 psi between the tank connector and fuel rail due to the friction of the high volume of fuel and the fuel lines.

The only way to minimize the 5 psi fuel pressure drop between tank connector and fuel rail is to run a larger diameter line.
Without further investigation I am not too sure whether the 5 psi drop from the fuel pump to the tank connector is due to the fuel pump or size of plastic fittings. As the fittings cannot be easily modified the only option is a bigger pump or Boost-A-Pump.

Realize that as the fuel pressure across the injector drops, the atomization deteriorates.

My suggested setup would be a return line system regulated 1:1 under boost with a Boost-A-Pump and stock fuel pump for moderate power and Walbro 255 high pressure pump for high power setups.

- A crushed FP regulator that increases FP by 10 psi would increase the fuel pressure differential across the injector in our Civic at the end of our run from 34 to 44 psi which provides about 14% more fuel.
- A return line system with stock FP regulator keeping the injector pressure differential constant at 55 psi would provide our Civic with 26% more fuel and better atomization.

[Swift Racing Technologies]

Originally Posted by Hondata

The Boost-A-Pump will not keep your fuel pressure constant in the stock Civic Si returnless fuel system. In the example of our supercharged Civic you lose 5 psi from the fuel pump to the connector on the outside of the tank and another 5 psi between the tank connector and fuel rail due to the friction of the high volume of fuel and the fuel lines.

The only way to minimize the 5 psi fuel pressure drop between tank connector and fuel rail is to run a larger diameter line.
Without further investigation I am not too sure whether the 5 psi drop from the fuel pump to the tank connector is due to the fuel pump or size of plastic fittings. As the fittings cannot be easily modified the only option is a bigger pump or Boost-A-Pump.

Realize that as the fuel pressure across the injector drops, the atomization deteriorates.

My suggested setup would be a return line system regulated 1:1 under boost with a Boost-A-Pump and stock fuel pump for moderate power and Walbro 255 high pressure pump for high power setups.

- A crushed FP regulator that increases FP by 10 psi would increase the fuel pressure differential across the injector in our Civic at the end of our run from 34 to 44 psi which provides about 14% more fuel.
- A return line system with stock FP regulator keeping the injector pressure differential constant at 55 psi would provide our Civic with 26% more fuel and better atomization.

Thanks Doug, could not have said it better myself, this is exactly what we had discussed months ago.

[soxfan143]

Originally Posted by Hondata

The Boost-A-Pump will not keep your fuel pressure constant in the stock Civic Si returnless fuel system. In the example of our supercharged Civic you lose 5 psi from the fuel pump to the connector on the outside of the tank and another 5 psi between the tank connector and fuel rail due to the friction of the high volume of fuel and the fuel lines.

The only way to minimize the 5 psi fuel pressure drop between tank connector and fuel rail is to run a larger diameter line.
Without further investigation I am not too sure whether the 5 psi drop from the fuel pump to the tank connector is due to the fuel pump or size of plastic fittings. As the fittings cannot be easily modified the only option is a bigger pump or Boost-A-Pump.

Realize that as the fuel pressure across the injector drops, the atomization deteriorates.

My suggested setup would be a return line system regulated 1:1 under boost with a Boost-A-Pump and stock fuel pump for moderate power and Walbro 255 high pressure pump for high power setups.

- A crushed FP regulator that increases FP by 10 psi would increase the fuel pressure differential across the injector in our Civic at the end of our run from 34 to 44 psi which provides about 14% more fuel.
- A return line system with stock FP regulator keeping the injector pressure differential constant at 55 psi would provide our Civic with 26% more fuel and better atomization.

Cool. But I don't have a stock Si fuel system. I have a Walbro 255 HP pump. I guess I should just run the return setup and keep my 650cc injectors.

[buurner]

Originally Posted by Implosive_Disgorgence

jrsc comes with injectors. ctsc uses stock injector, and uses the crushed fpr to up the fuel psi

But even with CT coming without injectors on the stage 2 the FPR is still crushed and they supplied 520cc injectors, JR is using 650cc injectors and even with the 440cc with the Xede tune the FPR was not crushed.

[Bugermass]

We had investigated this a while back and decided the return system is just plain more reliable.. The one issue not mentioned here, is with a returnless setup since the pressure drops with boost, you loose the ability to easily scale your fueling in the map.

Basically since your fuel pressure is still dropping as boost goes up, your fuel scaling between load points will gradually get larger as boost goes up. By inducing this phenomenon into your fuel mapping, you gradually deteriorate the abililty to catch issues that may make themselves evident based on trends in the fuel map..

Its really not a big issue in most cases but, its nice to be able tune fueling for say 8psi then 20psi, based on that, scale your map to 50psi, go to the track crank the boost to 35psi and only have to make small changes in fueling.

Better to have a totally reliable, stable, and dependable fuel system, then a bandaided one.

Just my opinions.

[soxfan143]

Originally Posted by Bugermass

We had investigated this a while back and decided the return system is just plain more reliable.. The one issue not mentioned here, is with a returnless setup since the pressure drops with boost, you loose the ability to easily scale your fueling in the map.

Basically since your fuel pressure is still dropping as boost goes up, your fuel scaling between load points will gradually get larger as boost goes up. By inducing this phenomenon into your fuel mapping, you gradually deteriorate the abililty to catch issues that may make themselves evident based on trends in the fuel map..

Its really not a big issue in most cases but, its nice to be able tune fueling for say 8psi then 20psi, based on that, scale your map to 50psi, go to the track crank the boost to 35psi and only have to make small changes in fueling.

Better to have a totally reliable, stable, and dependable fuel system, then a bandaided one.

Just my opinions.

Yea. I agree. That is why I decided to go with the return setup. The 650s with a return should be plenty for me with the GT2871R I'm running.

[Supa Ninja]

I installed my return setup not to long ago and definitely love it. Street tune was a piece of cake, 11.5 afr to redline at 20psi with my little 525's have a duty cycle no more then 87% with my pressure set at 60 psi.

With a -6an feed and return minus the fuel rail, it cost the same as a set of I'd 1000's. I think it's worth every penney. Just my 2 cents.



Ps I should be getting it tuned next week locally. I'm really curious to see my numbers.

[soxfan143]

Originally Posted by Supa Ninja

I installed my return setup not to long ago and definitely love it. Street tune was a piece of cake, 11.5 afr to redline at 20psi with my little 525's have a duty cycle no more then 87% with my pressure set at 60 psi.

With a -6an feed and return minus the fuel rail, it cost the same as a set of I'd 1000's. I think it's worth every penney. Just my 2 cents.



Ps I should be getting it tuned next week locally. I'm really curious to see my numbers.

Yea. I agree. I will be running my return with the stock line as he feed and a -6AN return with my 650s. Should be more than enough to support 14-16psi on my little 2871. Then I will upgrade to the 1000s when I do the GT30R.

[Supa Ninja]

Hey mike if you want I can make a high speed mspaint of what you'll need to add a return line.

[soxfan143]

Originally Posted by Supa Ninja

Hey mike if you want I can make a high speed mspaint of what you'll need to add a return line.

I'm good. I have everything pretty well figured out. Thanks for the offer tho bro. I need a fuel rail, FPR, some fittings and some line. Not exactly rocket science. lol..But thanks anyway.

[Supa Ninja]

You'll need a fuel filter and about a foot of the 5/16" submersible fuel line so you can bypass the stock fpr.

[soxfan143]

Originally Posted by Supa Ninja

You'll need a fuel filter and about a foot of the 5/16" submersible fuel line so you can bypass the stock fpr.

Yup. Have the submersible line already and the filter as well. I think the stock feed should be large enough for my goals. Anyone know at what power level the stock feed with a return system starts taking a crap? I think the RSX guys found that around 550-600whp it starts crapping on itself. But I'm not sure.