tested 545whp on stock fuel lines with walbro pumps
 

Hi guys, I ran into a problem with running lean on my 13b. I was only running 1 walbro intank pump, I was really impressed with how much that little pump could flow. Anyway something was running dry my injectors, stock lines or pump.
I have always been unsure of the flow limits with stock 3/16 lines. Some experts told me that this is the first thing to upgrade while others have said it can support 1000hp at the engine. hmm who do you believe?

So I decided to do a test with a......
2L container
Pressure gauge
Stop watch
Stock fuel reg
Syringe (to simulate boost on the reg)
Gate valve (to simulate a large injector)

I first tested a single intank walbro pump with the stock lines. What I did was turn on the pump on, I measured an instant base fuel pressure of 45psi then pressed the syringe to simulate 1.3bar boost. The fuel pressure rose to 65psi. I then open the gate slowly to see how much I could flow before the fuel pressure would drop.
The more the gate opened the more the pressure would drop.

I measured....

Base fuel pressure 45psi

60psi fuel pressure. 2L 36sec = 3.3L/min with 5psi pressure drop
55psi 2L 30sec = 4L/min with 10psi pressure drop

CONCLUSSION

from this I concluded that with one intank pump and stock lines assuming 5psi fuel pressure drop is acceptable, then this pump can support 375whp at 1.3bar boost.
I noticed that the pump would really start to struggle with flow as the reg pressure would increase with boost (simulated) and more than 1.3bar showed the pump flow slow dramatically. (I didn’t measure this just observed the flow from the gate as I increase the boost on the reg.) So I conclude that one walbro flow is only stable with 1.3bar boost applications.

My next test was with the two walbros installed. The results....

Base fuel pressure 65psi (stock reg is really struggling)

1.3bar boost simulated fuel pressures....

60psi 2L 25sec = 4.8L/min with 5psi fuel pressure drop
55psi 2L 24sec = 5L/min with 10psi drop
50psi 2L 22sec = 5.5L/min with 15psi drop.

CONCLUSSION

With 1.3bar boost pressure and two intank walbro, stock fuel lines are able to support 545whp. An aftermarket pressure reg is also needed with two pumps as the stock cant regulate accurately, with base pressure tested as high as 65psi.

thats amazing you did that testing yourself.
Good to know !

yes theorticaly though, yet to prove with dyno, i will need to upgrade the turbo and injectors now to test the max flow of this fuel system on a dyno. but the first test seemed to be accurate with the results i was getting on my set up as the turbo and injectors used were capable of 400whp, and i was just starting run lean at high revs and 1.3bar boost. this agress with the 375 measured with the single walbro.

That's genius even if it is in theory you have quite the intelligence.

haha! no just maybe too much time on my hands while my girlfriend is on holiday in Bali

good job, thats some impressive testing!

A+ bud, an excellent effort and kind of you to share.

You are gentlemen and a scholar

A+ as well!

:bigthumb:

Not to knock your test or anything, however those tests don't factor in other variables that are IRL; for example acceleration Gs.

If you are going to run that much power, why cheap out on runner larger diameter lines? I know some people are going to bring up the debate on overkill and the necessity but still...

Ive never seen a dyno that has yet to include the factor of g-force.

and as far as cheaping out, why waste money on unnecessary upgrades like fuel lines if simple testing like this proves that stock are fine. id rather save that money and put in into tuning or real hp upgrades.

but still the dyno could prove me wrong.

nice work 10 forum $ to you.

very nice work!

Awesome, thanks for sharing. You rarely see anyone provide some actual testing when they spout off theories on here. Nice work.

Thanks for the info, I better get a second walbro or bosch before I lean out my engine.

cool. what kind of voltage was (were) the walbro seeing?

awesome test! ogm.

I was wondering this myself and considering testing it, really glad you beat me too it.

looks like I'll be buying a 2nd walbro. :)

because i couldn't start my car for obvious reasons, i used a set of juper leads with my other car running to simulate 13v or normal orperating voltage on the rx7. also the fuel pumps have been rewired or hard wired to the battery in the boot.

update! pressure reg problems solved
 

Hi guys here's an update on the fuel system, If youve all read the original post you will know that i was having trouble with the stock fuel reg, It was not able to maintain 42psi base presure with the twin walbros installed. infact base presure jumped to 65psi.

I have over come this by running 2 stock fuel regs as the picture shows. The polsation dampner was removed and a second stock fuel reg has replaced it. they use the same thread. the only modification needed was a slight bevel machined in with a tapered grind stone to set the o ring. now with the stock twin regs the fuel pressure has droped back to 42psi and under simulated boost rose to aprox 70psi at 2bar (simulated with suringe)

CONCLUSION

twin walbro and twin stock fuel regs with stock fuel lines can support 545whp and maintain stable fuel pressure.

just for the record adding an extra stock regulator is only an option for S4s since S5's have the PD welded to the rail :)

Hey Oliver,

Just out of curiosity, what are you currently running for a turbo and what are you upgrading to?

Frank

i was running mp t-61 with p trim turbine at 1.3bar on bridgeport, one intank walbro wasnt quite enough fuel supply.
not sure what i will upgrade to yet ethier the similer flow but faster spoiling mp t-60 with the larger gt spec q trim wheel, or go the larger mp T-64 or T-70 and gt q trim turbine with higher boost levels.

hows your t-70 working out?

ah thats a shame...

do you know what your leak back pressure is and what the injector flow rating is that you are going to use on the car?.

This is a great thread Oliver!! And after you get more testing done, including dyno time I'll be sure to clean up the random posts and put this in the 2nd gen archives! Good on you bro.

Zach

It's coming, slowly but surely. I'm just solving the problems as they come. Turns out the flange was not only the wrong type, but also the wrong size :( , imagine my face when i tried installing the newly machined flange only to figure out it's a 4".

So when i got home from work I welded the flange I had bought for the downpipe to the housing. Now I just need another flange.

I'll have that turbo permanently installed in that car yet!

I'll let you know how it goes.