Max HP supported for stock LS400 system
- Thread starter spf_lexus
- Start date
The 1UZFE EGR Delete Kit is available for sale here.
Sean, this may sound a bit wacko, but don't worry too much about your line size, just make sure your pump has enough head to overcome any line restriction, and can maintain the pressure necessary at the regulator at the highest boost you want to run.
The mentality of oversizing fuel lines is leftover from the days of carbs and mechanical fuel pumps that were "sucking" from the tank. Nowadays with electric fuel pumps that are immersed in the fuel tank, and are pushing the fuel to the engine, all that matters is whether they can maintain the pressure needed at the rails.
Any pressure restriction from the line will be made up by the reserve capacity of the pump, if that makes sense? If your fuel pressure starts dropping off at high boost, get yourself a bigger pump (or better yet, a Kenne Bell Boost-a-Pump).
Here's a good article on KB's website: http://www.kennebell.net/techinfo/general-info/fuelpumptech.pdf scroll about 3/4 of the way down and look at the question "Should I install larger fuel lines......."
The mentality of oversizing fuel lines is leftover from the days of carbs and mechanical fuel pumps that were "sucking" from the tank. Nowadays with electric fuel pumps that are immersed in the fuel tank, and are pushing the fuel to the engine, all that matters is whether they can maintain the pressure needed at the rails.
Any pressure restriction from the line will be made up by the reserve capacity of the pump, if that makes sense? If your fuel pressure starts dropping off at high boost, get yourself a bigger pump (or better yet, a Kenne Bell Boost-a-Pump).
Here's a good article on KB's website: http://www.kennebell.net/techinfo/general-info/fuelpumptech.pdf scroll about 3/4 of the way down and look at the question "Should I install larger fuel lines......."
spf_lexus
Active Member
Thanks Cribbj. I am in a back-forth arguement with my builder (who I may stop using) about pumps and line size. I mentioned the boost-a-pump in combination with my 255lph walbro. I thought the 255 supports 500hp and he says its too small and that fuel cannot be forced through a certian bore. After your description I get the feeling he's sticking to his old school roots. Anyway I have an AEM universal 100psi fuel reg and a 100psi gauge and just need basic fittings to mount inline. I know my stock system is enough to at lease start and run reasonably so it's on the back burner for now. I was seeing 7psi with 4.0L and I expect around 5psi with the 4.7L so I suppose fuel consumption will not skyrocket over my original setup.
Do you think i'm safe with the factory fuel line on a 4.7L at 5-7psi of boost with the parts listed above?
Do you think i'm safe with the factory fuel line on a 4.7L at 5-7psi of boost with the parts listed above?
Anodyne,
You plan on running an 800hp engine with a 700hp pump? Something doesn't add up there.
I assume you're planning on using an 044 which won't flow 700hp worth of fuel @ 90psi.
I run 2 044's to be on the safe side and for the cost of a pump and hose it's cheap insurance.
You plan on running an 800hp engine with a 700hp pump? Something doesn't add up there.
I assume you're planning on using an 044 which won't flow 700hp worth of fuel @ 90psi.
I run 2 044's to be on the safe side and for the cost of a pump and hose it's cheap insurance.
Builders believe in big pumps, big lines, and KISS. They don't like black boxes that have electronic gizmo's in them that are hard to understand.
Here's a link to some fuel pump testing that my friend Jeff Lucius & I did back in 2002/2003: http://www.stealth316.com/2-fuelpumpguide.htm#j5 and below is the actual test sheet that RC provided me on the Walbro. Below that is an Excel calc that translates fuel flow to HP, so as you can see, unless you're planning to turn your LS into a 2000 HP funny car, you're fine with the Walbro + the BAP, and the stock lines.
Here's a link to some fuel pump testing that my friend Jeff Lucius & I did back in 2002/2003: http://www.stealth316.com/2-fuelpumpguide.htm#j5 and below is the actual test sheet that RC provided me on the Walbro. Below that is an Excel calc that translates fuel flow to HP, so as you can see, unless you're planning to turn your LS into a 2000 HP funny car, you're fine with the Walbro + the BAP, and the stock lines.
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spf_lexus
Active Member
Yeah your probably right, i'm giving him until tomorrow afternoon to produce something or AAA is coming to my rescue. I'm assuming at WOT the voltage is still 12v right? I always see 14.4 on my voltometer, is it possible the pump see's voltage this high? I took a good look at the chart and it looks like w/o the BAP I can still cover my 450bhp peak target.
Funny, I always figured the higher the pressure = more lph. Is the "psi" side possibly flip-flopped? I dont get why 40psi of fuel pressure flows more than 100psi of fuel pressure.
Funny, I always figured the higher the pressure = more lph. Is the "psi" side possibly flip-flopped? I dont get why 40psi of fuel pressure flows more than 100psi of fuel pressure.
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spf_lexus
Active Member
Still does not make sense. My stock LS400 has around 30psi at idle and it raises up to above 60+ at WOT to supply more fuel. Why would the engine require less pressure at WOT for more flow?
Do Walbro's operate differently than my identical OEM denso pump?
The chart above shows less LPH as psi rises. I do not get this..
Do Walbro's operate differently than my identical OEM denso pump?
The chart above shows less LPH as psi rises. I do not get this..
Sean, I think you're confusing what the engine wants with what the fuel pump can supply. You're correct that at high boost, WOT, the engine wants the most fuel flow, and at the highest pressure. Unfortunately, this is just the inverse of what fuel pumps can provide. They provide the most flow, at the lowest head (pressure). It's just the nature of the beast.
Nearly all pumps (except for piston pumps) have a characteristic curve that shows flow dropping off with increased head (pressure). So unless you have a variable speed pump controller, you can get high flow at low pressure, or low flow at high pressure out of most pumps.
The trick is to know how much flow you need, at what pressure, and make sure your pump is man enough to do it, and has enough reserve to overcome any pressure drops along the way (like smallish lines, fittings, etc.) That's why these pump "dyno" charts are useful.
Walbro's are not a bad pump, however they're noisy compared to the Supra pump, and they've been known to die prematurely, whereas I've never known a Supra pump to die, unless it was 15 years old. There's a reason the Denso pumps are double the price of the Walbro, and it's not just because of the Toyota name on them. For my money, I wouldn't put anything but a Supra or a Bosch 044 pump on a high HP, in tank, boosted application.
You should size/pick the pump with at least 25% more capacity than you need, which will allow for aging and wear, and of course, remember that we run a return type fuel system, so in order for the whole fuel system to work properly, you have to oversize the supply "somewhat". Some people do this with multiple pumps, I prefer to do it with a variable speed controller, like the Kenne Bell BAP.
Also remember that as you pressurise the fuel it heats up, then when you run it up through the fuel rails on the hot engine, it picks up more heat. As fuel heats up, it loses density and energy (this is why old drag racers used ice packs for fuel coolers.) So think about this before putting on a monster fuel system that will pump 1000 HP of fuel, when your engine is only wanting 50-75 HP at cruise. All you're doing with that monster fuel system is recirculating and heating a lot of fuel, so you're going to evaporate a lot of it due to the heating, plus your engine will actually be down on power due to its loss of density. (There are some very good engineering reasons why Toyota and the other OEM's reduce the voltage to the fuel pumps at idle and at cruise; people who bypass this function and run full voltage to the pump(s) all the time are missing this very important point.)
Another problem with monster fuel systems is the people tend to forget the return line. When you're pumping 1000 HP of fuel from the tank, but the engine is only using 100 HP, the rest has to go through the return to the tank. Now, for the fuel pressure regulator to work properly, the return must be running at atmospheric pressure, but obviously if you're trying to stuff 900 HP worth of fuel into it, there's going to be some restriction, and this restriction downstream of the fuel pressure regulator is going to cause it to do strange things upstream, like raising the fuel pressure much higher than it should at idle and cruise. So then you adjust the fuel pressure down at idle, but take the car out and do a WOT run and you lose fuel pressure and go lean and wonder why?
So IMO, there are just way too many potential problems with these monster fuel systems to use them for a street car. I much prefer designing the system for where it's going to operate most of the time, and using the BAP to boost it for those "occasional" WOT runs.
In my single Denso pump fuel system (which has been running with rock solid reliability on my single turbo Supra for the last six years) I PWM the voltage to the fuel pump down to 8.5 volts at idle and cruise, and then raise it to 12v for low/medium boost, and then run it up to 15-16 volts for high boost. This corrects the problem of the pump's characteristic curve, and matches its output to the needs of the engine. (BTW, if you reduce the voltage to the Walbro, you must use the PWM method, and not just a dropping resistor. We found back in 2002 that the Walbro's will not operate reliably at a constant voltage of 8.5 to 9.0 volts, but will with a 12v supply, PWM'd to 8.5v)
The key is to try to flow just enough fuel to maintain the correct (42psi) fuel pressure across the injectors under all conditions (and this is what returnless fuel systems do). This way, the ECU stays happy because the injector deliveries stay linear and the engine is much easier to map. When the tuner is finished, the fuel map should then resemble the engine's torque curve, instead of a topographic map of the Rocky Mountains
which you can get when the fuel system isn't working right, and you try to compensate for it in the ECU.
Sorry for the length of this, but oversized fuel systems, and the problems they can cause tend to get me on my soapbox.
Nearly all pumps (except for piston pumps) have a characteristic curve that shows flow dropping off with increased head (pressure). So unless you have a variable speed pump controller, you can get high flow at low pressure, or low flow at high pressure out of most pumps.
The trick is to know how much flow you need, at what pressure, and make sure your pump is man enough to do it, and has enough reserve to overcome any pressure drops along the way (like smallish lines, fittings, etc.) That's why these pump "dyno" charts are useful.
Walbro's are not a bad pump, however they're noisy compared to the Supra pump, and they've been known to die prematurely, whereas I've never known a Supra pump to die, unless it was 15 years old. There's a reason the Denso pumps are double the price of the Walbro, and it's not just because of the Toyota name on them. For my money, I wouldn't put anything but a Supra or a Bosch 044 pump on a high HP, in tank, boosted application.
You should size/pick the pump with at least 25% more capacity than you need, which will allow for aging and wear, and of course, remember that we run a return type fuel system, so in order for the whole fuel system to work properly, you have to oversize the supply "somewhat". Some people do this with multiple pumps, I prefer to do it with a variable speed controller, like the Kenne Bell BAP.
Also remember that as you pressurise the fuel it heats up, then when you run it up through the fuel rails on the hot engine, it picks up more heat. As fuel heats up, it loses density and energy (this is why old drag racers used ice packs for fuel coolers.) So think about this before putting on a monster fuel system that will pump 1000 HP of fuel, when your engine is only wanting 50-75 HP at cruise. All you're doing with that monster fuel system is recirculating and heating a lot of fuel, so you're going to evaporate a lot of it due to the heating, plus your engine will actually be down on power due to its loss of density. (There are some very good engineering reasons why Toyota and the other OEM's reduce the voltage to the fuel pumps at idle and at cruise; people who bypass this function and run full voltage to the pump(s) all the time are missing this very important point.)
Another problem with monster fuel systems is the people tend to forget the return line. When you're pumping 1000 HP of fuel from the tank, but the engine is only using 100 HP, the rest has to go through the return to the tank. Now, for the fuel pressure regulator to work properly, the return must be running at atmospheric pressure, but obviously if you're trying to stuff 900 HP worth of fuel into it, there's going to be some restriction, and this restriction downstream of the fuel pressure regulator is going to cause it to do strange things upstream, like raising the fuel pressure much higher than it should at idle and cruise. So then you adjust the fuel pressure down at idle, but take the car out and do a WOT run and you lose fuel pressure and go lean and wonder why?
So IMO, there are just way too many potential problems with these monster fuel systems to use them for a street car. I much prefer designing the system for where it's going to operate most of the time, and using the BAP to boost it for those "occasional" WOT runs.
In my single Denso pump fuel system (which has been running with rock solid reliability on my single turbo Supra for the last six years) I PWM the voltage to the fuel pump down to 8.5 volts at idle and cruise, and then raise it to 12v for low/medium boost, and then run it up to 15-16 volts for high boost. This corrects the problem of the pump's characteristic curve, and matches its output to the needs of the engine. (BTW, if you reduce the voltage to the Walbro, you must use the PWM method, and not just a dropping resistor. We found back in 2002 that the Walbro's will not operate reliably at a constant voltage of 8.5 to 9.0 volts, but will with a 12v supply, PWM'd to 8.5v)
The key is to try to flow just enough fuel to maintain the correct (42psi) fuel pressure across the injectors under all conditions (and this is what returnless fuel systems do). This way, the ECU stays happy because the injector deliveries stay linear and the engine is much easier to map. When the tuner is finished, the fuel map should then resemble the engine's torque curve, instead of a topographic map of the Rocky Mountains
which you can get when the fuel system isn't working right, and you try to compensate for it in the ECU.Sorry for the length of this, but oversized fuel systems, and the problems they can cause tend to get me on my soapbox.
spf_lexus
Active Member
Thanks for the breakdown Cribbj. I soaked up a lot of that. I am pretty green in the fuel delivery department but i'm glad to know I don't need to re-do the entire system. I think I will fire it up and test for lean spots or pressure drops like you stated to see if my 255 is running out of steam, and if so I plan on the Kenne Belle add on. When you said
As of right now the only fuel mods done are the 315cc injectors, walbro, and 0-100psi AEM fuel reg w/ gauge that I am in the process of finding fittings for.
As of right now the only fuel mods done are the 315cc injectors, walbro, and 0-100psi AEM fuel reg w/ gauge that I am in the process of finding fittings for.
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