Returnless Fuel Systems - what is the limit?

[Full-Race Geoff]

I have had a lot of people asking me when they need to add an external FPR and a fuel return line - however after spending a day with tuner-extraordinaire jeff evans of Evans Tuning - EFI Tuning Specialists he let me know some interesting things i wanted to share with you guys. ** these estimations assume an equal length header turbokit and ID 1000cc injectors tuned properly

-a walbro 255 high pressure intank pump, can flow enough fuel for ~440whp on stock intank FPR, and ~500hp on a crushed FPR "Comptech Style"

-a bosch motorsports intank fuel pump, can flow enough fuel for ~480whp on stock intank FPR and ~550hp on crushed 'Comptech Style' FPR

-if you install a product called "Boost-A-Pump" mfg'd by Kenne Bell, this will jump the fuel pump's voltage supply to 20V (perfectly fine for the fuel pump, in fact good for it!) and allow the walbro to flow close to 600hp and the bosch beyond this

i hope this helps some guys realize its not absolutely necessary to add the return line and external fpr, of course for anyone looking to run 30+ psi or have a race car the FPR may prove to be a wise investment, but not at all needed for 99% of the builds out there (these cars are too damn nice to turn into drag cars anyway!)

[Implosive_Disgorgence]

+1 for good info, i know a lot of people have been asking about fuel return systems as well.

[udumkid]

Thanks Geoff... wonder why other companies didnt realise this,making $ perhaps on add ons?

[Str8JDM]

good info! didnt know bosch made an intank pump. where could i find one of them?

[soxfan143]

Good stuff Geoff. Are you guys gonna start selling the boost-a-pump?

[BlueSi4]

Sweet, 1000cc injectors here I come

[buurner]

So that makes me wonder why JRSC in install directions does not call for a crushed FPR like the Comptech setup... interesting

[Implosive_Disgorgence]

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

[Full-Race Geoff]

Originally Posted by Str8JDM

good info! didnt know bosch made an intank pump. where could i find one of them?

we stock and use them, they are much more expensive than the walbros, but a better and more robust design, i just installed one in my R14 recently

Originally Posted by udumkid

Thanks Geoff... wonder why other companies didnt realise this,making $ perhaps on add ons?

perhaps, hard to guess - its possible they just dont know this?

Originally Posted by soxfan143

Good stuff Geoff. Are you guys gonna start selling the boost-a-pump?

I didnt really consider selling them, i know im considering picking one up for the R14

Originally Posted by BlueSi4

Sweet, 1000cc injectors here I come

that is definitely the injector size to use, and i recommend the ID 1000cc because they offer the finest quality spray pattern and corresponding performance

Originally Posted by Implosive_Disgorgence

i know a lot of people have been asking about fuel return systems as well.

Originally Posted by Implosive_Disgorgence

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

neither are really proper fuling solutions persay, bu they both get the job done obviously...

[erik loza]

Jeff, what about the pump dropping pressure as boost rises? How does that factor into all of this? Thanks in advance.

[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!

[erik loza]

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!

Thank you very much. I am linking this thread over in our supercharger forum over at ClubRSX. Many over there will be interested in it.

[tmartin]

The only thing I would like to add to this is that in a supercharger application the whp figures given are way lower do to the fact that the blower has a lot of parasitic drag compared to a turbo setup. I never would have made my 407 whp with my Lysholm Twinscrew blower without a return setup because of this. I am running the ID 1000 injectors with a full -6an return setup. Best injectors on the market by far.

Good thread I am eager to see more on this topic.

[Alphi]

Thanks Geoff for the info. Good to know.

[erik loza]

Geoff, I was reading over the mfr's specs and they are stating that there is no increase in fuel temps. My understanding was that part of the issue in a deadhead system is that the fuel heats up once the car goes into boost, as the pump is trying to work harder to force it through the injectors against manifold pressure. Can you comment on the fuel temp issue?

[2RotorMotor]

with non return system the fpr cant compensate for boost, so if you are boosting a higher ammount than 10psi, this can affect the ammount of fuel delivered because of the pressure differential, its better just to switch to a return system if you are serious about boosting. A greddy kit or similiar should be fine with the returnless system.

[tmartin]

Originally Posted by 2RotorMotor

with non return system the fpr cant compensate for boost, so if you are boosting a higher ammount than 10psi, this can affect the ammount of fuel delivered because of the pressure differential, its better just to switch to a return system if you are serious about boosting. A greddy kit or similiar should be fine with the returnless system.

I agree with you.

It makes sense that getting higher and more consistant voltage to the fuel pump is a good thing but what isnt being addressed is the spray pattern that can be effected by lack of regulated and correct pressure. With a FPR you can adjust you are sure you are maximizing the injectors ability to spray correctly by giving it the correct regulated fuel pressure. No matter how good an injector is it can only be as good as the systems that support it. In the case of the injector dynamics injectors that we all love I would suspect that they would be the best of the bunch at being able to maintain a good spray pattern but even these would be open to the above concept I would think.

Interested in thoughts in regards.

[Full-Race Geoff]

Originally Posted by erik loza

Thank you very much. I am linking this thread over in our supercharger forum over at ClubRSX. Many over there will be interested in it.

please make sure they post up in here, since i dont visit that part of the site!

Originally Posted by tmartin

The only thing I would like to add to this is that in a supercharger application the whp figures given are way lower do to the fact that the blower has a lot of parasitic drag compared to a turbo setup. I never would have made my 407 whp with my Lysholm Twinscrew blower without a return setup because of this. I am running the ID 1000 injectors with a full -6an return setup.

yes good point, hence the reason my assumption was "an equal length header turbokit" with the supercharger it is just less efficinet due to the parastic losses and that requires fuel to overcome

Originally Posted by erik loza

Geoff, I was reading over the mfr's specs and they are stating that there is no increase in fuel temps. My understanding was that part of the issue in a deadhead system is that the fuel heats up once the car goes into boost, as the pump is trying to work harder to force it through the injectors against manifold pressure. Can you comment on the fuel temp issue?

I wish i knew the answer to you - from an engineering standpoint my instinct says it would be no different from a returnless to a return, the only heat added to the system is from the fuel pump, and thats the same regardless of a return or not.

Originally Posted by 2RotorMotor

with non return system the fpr cant compensate for boost, so if you are boosting a higher ammount than 10psi, this can affect the ammount of fuel delivered because of the pressure differential, its better just to switch to a return system if you are serious about boosting. A greddy kit or similiar should be fine with the returnless system.

yes absolutely, this is correct and the 1:1 rising rate found on external pressure regulators. The way this returnless system can work well is to crush the FPR so you have a base FPR of ~70psi, then simply use a robust fuel pump to maintinat that, and if boost goes to 25psi you still have 45psi fuel pressure to work with.

***KEEP IN MIND: Fuel pump output pressure - boost level = fuel rail pressure***

Originally Posted by tmartin

I agree with you.

It makes sense that getting higher and more consistant voltage to the fuel pump is a good thing but what isnt being addressed is the spray pattern that can be effected by lack of regulated and correct pressure. With a FPR you can adjust you are sure you are maximizing the injectors ability to spray correctly by giving it the correct regulated fuel pressure. No matter how good an injector is it can only be as good as the systems that support it. In the case of the injector dynamics injectors that we all love I would suspect that they would be the best of the bunch at being able to maintain a good spray pattern but even these would be open to the above concept I would think.

Interested in thoughts in regards.

[tmartin]

Originally Posted by Full-Race Geoff

yes absolutely, this is correct and the 1:1 rising rate found on external pressure regulators. The way this returnless system can work well is to crush the FPR so you have a base FPR of ~70psi, then simply use a robust fuel pump to maintinat that, and if boost goes to 25psi you still have 45psi fuel pressure to work with.

***KEEP IN MIND: Fuel pump output pressure - boost level = fuel rail pressure***

With no true FPR doing the regulating does this not add to much pressure to the injectors thus not allowing for proper spray patterns? I know in the case of the ID injectors they love lots of pressure as do most but not having done a lot in this area I would wonder if there is a upper boundary on fuel pressure to consider as well?

[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?