Walbro 255 hp
Registered User
Joined: Oct 2002
Posts: 4,479
Likes: 1
From: Vortech Central
Originally Posted by Soul Coughing,Feb 24 2008, 10:39 AM
500whp for a supercharged setup right? as you said earlier, the motor is making more than that, but because of the parasitic loss of the supercharger, the motor is only making 500 to the wheels... So there is a difference in fuel needs for someone someone with a turbo setup compared to someone with a supercharged setup!
You realize it's all about fuel injector duty right? On a turbo and supercharged setup the highest duty cycles will be at or near near redline at WOT and at full boost.
*sits down in a Lazy Boy & kicks up the foot rest*
Joined: Sep 2001
Posts: 3,831
Likes: 3
I would think that the fuel demands of a turbo would be greater (not less) than a SC, given that a turbo will hit full boost much sooner...thereby requiring more fuel much sooner and for a more sustained duration. 
FWIW, I'm making over 500 whp with the Walbro, and have not encountered any fuel delivery problems as of yet. *knocksonwood*
FWIW, I'm making over 500 whp with the Walbro, and have not encountered any fuel delivery problems as of yet. *knocksonwood*
Thread Starter
Joined: Oct 2000
Posts: 9,033
Likes: 21
From: South of the pier, Huntington Beach, CA
Taking the supercharger drag into account I can't hit the equivalent of 540 turbo rwhp with this Walbro 255 hp pump.
I initially dynoed 464 rwhp at 9500 rpm with zero miles. I added a larger exhaust, more boost, and some other changes to up the output. Now broken in, it runs out of gas at at 465 rwhp. The good part is the 465 rwhp is at 8500 rpm so I have another 1000 rpm to make power. All I have to do is secure a steady high pressure source of fuel.
That is probably another 60+ rwhp if the supercharger keeps making boost.
I initially dynoed 464 rwhp at 9500 rpm with zero miles. I added a larger exhaust, more boost, and some other changes to up the output. Now broken in, it runs out of gas at at 465 rwhp. The good part is the 465 rwhp is at 8500 rpm so I have another 1000 rpm to make power. All I have to do is secure a steady high pressure source of fuel.
That is probably another 60+ rwhp if the supercharger keeps making boost.
Joined: Jan 2006
Posts: 16,548
Likes: 1
Originally Posted by Soul Coughing,Feb 24 2008, 10:43 AM
because a supercharger uses energy from the crank to pump air into the motor! So when a supercharged motor puts down 500whp, the actual motor is making more horsepower, but its being used up to spin the supercharger! So in reality, the supercharged motor is making near 600whp depending on efficiency of the blower! You have to account for that lost power with the amount of fuel your injecting into the motor! (thats why his fuel requirements dictate a change in the fuel setup at a lower whp) Whereas a turbo setup is using spent exhaust gases, so the efficiency of the system is increased dramatically! If sideways was using a turbo setup, he would be making alot more than 500whp, because the energy that would have been used to turn the supercharger is now being used to turn the wheels! That is why the fuel requirements of a supercharged setup is more than a turbocharged setup for the same 'whp'!
*sits down in a Lazy Boy & kicks up the foot rest*
*sits down in a Lazy Boy & kicks up the foot rest*
I think a turbo requires more fuel than a Centrifugal SC. Turbo needs fuel from lower RPM's for a longer time, SC needs more fuel as it builds.
Same reason SC can run more boost (stock for stock) over a turbo. SC will hit max boost at it's redline, turbo will hit max boost at mid rpms and carry boost.
Thread Starter
Joined: Oct 2000
Posts: 9,033
Likes: 21
From: South of the pier, Huntington Beach, CA
Originally Posted by PatS4P,Feb 23 2008, 11:51 PM
I have been researching this problem as I expect to be using 1000cc
injectors and I think fuel delivery may be a problem. I looked at the flow rates and pressures, injector duty cycles, etc. The Walbro and the Bosch are actually very close in delivery. Short of going with a Weldon (big $) Airmotive is gravity, I am going to use an intank Walbro with another inline Walbro and upgrade the pressure line (-8) and leave the return alone. Increase flow of 30-40% . I've been told by a respected tuner this setup is good to high 600whp setups.
injectors and I think fuel delivery may be a problem. I looked at the flow rates and pressures, injector duty cycles, etc. The Walbro and the Bosch are actually very close in delivery. Short of going with a Weldon (big $) Airmotive is gravity, I am going to use an intank Walbro with another inline Walbro and upgrade the pressure line (-8) and leave the return alone. Increase flow of 30-40% . I've been told by a respected tuner this setup is good to high 600whp setups.
The Bosch seems to be more capable than the Walbro at higher demands. As an inline booster pump it appears to be even more capable.
Registered User
Joined: Sep 2007
Posts: 1,490
Likes: 0
Originally Posted by Sideways,Feb 24 2008, 08:58 AM
The whole reason for this thread is the Walbro unit won't support 500 rwhp.
If the whole entire point of this thread was that a walrbo cant support 500rwhp, dont you think its somewhat important to put that in the initial post? and not 5 posts later? seems to me like the whole point in this thread is that you wanted a alternate source as a fuel pump as yours wasnt working past 8600rpm... So with that said... did i give you an alternate source? yes. in fact i gave you multiple. get your story straight.
Registered User
Joined: Jul 2003
Posts: 442
Likes: 0
From: Fastville, FL
which walbro pump are you using? i think something else might be wrong
ive been using walbros for years, on literally hundreds of cars. Id say there are 50-75 cars ive tuned over 500 whp w/ a walbro 255 hp.
the flow/pressure calculations never work exactly.
realistically different engine setups need different fuel requirements due to differences in volumetric efficiencies and in brake specific fuel consumptions.
ive been using walbros for years, on literally hundreds of cars. Id say there are 50-75 cars ive tuned over 500 whp w/ a walbro 255 hp.
the flow/pressure calculations never work exactly.
realistically different engine setups need different fuel requirements due to differences in volumetric efficiencies and in brake specific fuel consumptions.
Former Moderator
Joined: Jan 2002
Posts: 3,677
Likes: 1
From: Mesa
Is it possible that there is a restriction in your line? Did you add an inline filter, etc..? The OEM fuel line is ~5AN if I am not mistaken, some would recommend going ~6 or ~8.
Would be interesting to measure your pressure near the tank and compare it to what you are seeing at the rail when you hit the point where you are running out of fuel.
Would be interesting to measure your pressure near the tank and compare it to what you are seeing at the rail when you hit the point where you are running out of fuel.
Registered User
Joined: Feb 2007
Posts: 1,923
Likes: 1
From: Lincoln, NE
Originally Posted by rob!,Feb 24 2008, 07:03 AM
you only have a couple options... you can use an intank walbro... then from there run a -8 or -10 line with a inline walbro or bosch 044. Next option is to sump the tank. from there i would run a -10, if you want to run a aeromotive pump i would not get the a1000 although it is rated high, it does not support too much power, The eliminator supports much more. Weldon pumps are a lot of money but work great. The best option which i had done on one of my previous cars was I sumped the tank, ran -10 line with a Y then put two bosch 044's. then another Y and ran that line straight to the fuel rail. or you can run a dual sump, and two -10 lines then the two pumps then a Y into a single -10. No matter what once the walbro starts to lose fuel pressure on higher HP dyno pulls, you are running into big money. You have to run pre and post filters also. Here are a couple pics where i got my ideas from when i did mine.
