1999 Gen VI EFI to Q Jet 4L80E

[amrush2112]

That's not really how that works. The fuel pump is providing(and rated for) a certain volume at a given pressure. The regulator is adjusting the pressure before the carb using a variable sized orifice and returning the unused fuel back to the tank. The pump impellers are designed to have maximum efficiency and volume at the pressure they are designed for. Any difference in the pressure of the system from designed would result in a lower than designed volume. The EP381 flows enough volume in a standard fuel injection setup ,with the regulator after the injectors, to support ~450hp. I would bet that having the regulator before the carb like that you will likely run out of volume much sooner than that. I would bet that setup runs out of fuel closer to 350-400hp(which would probably still put it near what you are going to get from the TBI pump).

It sounds like the OP is wanting to run serious HP, so he will likely need to swap to something a bit more serious, like a walbro 455 in the tank or a Holley blue pump on the frame rail. The holley blue would be comparable flow rating to the walbro, but rated at a more carb friendly pressure.

I have run a Holley Blue Pump years ago with 1/2" lines to a Pontiac 455 motor that made about 600 hp. It was a 9 or so PSI wide open and I used two Holley regulators on an 850 DP to drop it back to 6.5. It worked fine. If I run into any fuel issues I know that works! Lol!

 

[BeXtreme]

IDK, I'm running my Blue Print "383" TBI at 20 PSI with the EP381, putting out over 400 HP, with no issues keeping ~12.5 AFR up to 5700 RPM (I may go to 6000 but I'm still breaking it in).

From "Fluid Power" classes I seem to remember, with a centrifugal pump, the higher the pressure, the lower the volume due to internal slippage.

Are you regulating the flow before the throttle body, or is the regulator on the return line? My point was that you are flowing low volume at the pump because it is pushing against the regulator and then you are restricting the volume at the regulator in order to pull the pressure down before feeding it to the carburetor. That's the absolute worst of both worlds.

In a normal fuel injection system with a return, you are feeding full available volume to the injector and the regulator is at the end of the system to control the pressure in the entire feed line. If the regulator can't flow enough fuel, the pressure would actually be too high at idle and it needs to do LESS work to maintain pressure as the demand on the fuel system increases. In a carb setup with a regulator that is feeding to the carb, you could have any pressure in the feed line to the regulator(it could be 5psi or 100psi.. there's nothing really controlling that) and the regulator is needing to open more and more in order to feed fuel to the carburetor as the demand increases. So you could be increasing the pressure on the feed side as less fuel is bypassed to the return(thereby lowering the provided volume) and the regulator could be unable to flow enough volume through the orifice to maintain the 5psi feed to the carb. The obvious solution would be to plumb the carb setup similar to fuel injected where you have the fuel pump run to the carb and the regulator on a "return line" after the feed to the carb to maintain that pressure, but almost no one actually plumbs a carb feed that way.

 

[amrush2112]

I do need to say the dialogue here is fantastic! You guys ARE the reason this forum is so awesome! Whether I am right or wrong is irrelevant in all this. It is about collective of minds and experience that input some amazing data that I need to go through. This is why I appreciate everyone's input for all they comment on. Thank you!

 

[BeXtreme]

Tell me how long you expect a 4L80 to live running full line pressure all day every day? And what would ECT and MAP require in terms of adjustment to provide anything useful?

And I misspoke on the ECT with regards to TCC function, that's a function of TFT which stays in this scenario.

He said he is building a high horsepower fun toy. People run full line pressure all the time in similar builds where they have gone to full manual or have trans brakes and anything besides full line pressure is not an option. I don't actually think it would go to full line pressure though. I'd have to take a look at the trans tables, but I'm pretty sure that the line pressure table doesn't reference MAF or MAP.

ECT would need adjustment for what he is doing with his cooling system. MAP will need adjustment for whatever wild cam he is putting in it. If the thing is only pulling 10in. hg. at idle, it will think he is at 50% load all the time.

 

[Supercharged111]

He said he is building a high horsepower fun toy. People run full line pressure all the time in similar builds where they have gone to full manual or have trans brakes and anything besides full line pressure is not an option. I don't actually think it would go to full line pressure though. I'd have to take a look at the trans tables, but I'm pretty sure that the line pressure table doesn't reference MAF or MAP.

ECT would need adjustment for what he is doing with his cooling system. MAP will need adjustment for whatever wild cam he is putting in it. If the thing is only pulling 10in. hg. at idle, it will think he is at 50% load all the time.

They don't directly reference MAF or MAP, but the PCM uses both to calculate torque. Line pressures are commanded based on calculated torque output. When the MAF is out, it defaults to full line pressure. Been there done that.

Neither ECT nor MAP require any adjustment, it was a bit of a truck question as I had no idea where you were going with this. It looks like you're alluding to VE now and I'm not sure why since with a carb the PCM doesn't control the engine and the calculated torque is irrelevant if you insist on ditching the MAF.

 

[PlayingWithTBI]

My point was that you are flowing low volume at the pump because it is pushing against the regulator and then you are restricting the volume at the regulator in order to pull the pressure down before feeding it to the carburetor. That's the absolute worst of both worlds.

The regulator has 3 ports, one to the float (or injectors), one from the pump, and one return line to the tank. When the carb, (or TB) needs more flow the regulator's diaphragm closes down to maintain the same set pressure, no matter what the flow is. When the engine is shut off, it maintains the same pressure and diverts all the flow back to tank. There may be a little delay from the regulator but, that's why your carb has a float bowl.

I guess someone will have to take the EP381 and turn it on full flow to a jug and measure how much it can pump. I'll bet it pumps more than the 155L/Hr it's rated at full pressure.

 

[BeXtreme]

They don't directly reference MAF or MAP, but the PCM uses both to calculate torque. Line pressures are commanded based on calculated torque output. When the MAF is out, it defaults to full line pressure. Been there done that.

Neither ECT nor MAP require any adjustment, it was a bit of a truck question as I had no idea where you were going with this. It looks like you're alluding to VE now and I'm not sure why since with a carb the PCM doesn't control the engine and the calculated torque is irrelevant if you insist on ditching the MAF.

You brought up MAP, MAF, and ECT.

Are you saying that an 0411 runs full line pressure on the trans in speed density mode? That doesn't seem right. Properly failing the MAF input should default to speed density mode. He can then tune the Normal and Performance tables to the line pressure he wants. I would suggest just using Bluecat and copy the tables straight in. Again, no MAF or ECT needed. Probably doesn't actually even need MAP, but having it would give him full function.

https://forum.hptuners.com/showthread.php?90270-Pcm-0411-MAF-code-P0102-and-P0107

 

[Supercharged111]

You brought up MAP, MAF, and ECT.

Are you saying that an 0411 runs full line pressure on the trans in speed density mode? That doesn't seem right. Properly failing the MAF input should default to speed density mode. He can then tune the Normal and Performance tables to the line pressure he wants. I would suggest just using Bluecat and copy the tables straight in. Again, no MAF or ECT needed. Probably doesn't actually even need MAP, but having it would give him full function.

https://forum.hptuners.com/showthread.php?90270-Pcm-0411-MAF-code-P0102-and-P0107

Bluecat tool is the ****. I'm saying the black box and 411 both will revert to full line pressure once the MAF fails, but the 411 has a custom operating system available to keep that from happening. No such option on the blackbox. The torque calculation model sucks in speed density mode and the PCM knows it so it kinda gets thrown out the window.

 

[Erik the Awful]

would bet that having the regulator before the carb like that you will likely run out of volume much sooner than that. I would bet that setup runs out of fuel closer to 350-400hp(which would probably still put it near what you are going to get from the TBI pump).

There are two common setups, a return style FPR, and a deadhead FPR. The Holley 12-887 is a return-style FPR, and the only way you're going to "overpower" the regulator and hit the carburetor with too much pressure is if you flow so much fuel that it can't exit the return fast enough. The Holley 12-803 is a deadhead FPR, and I run one at a steady 7 psi on my big-block Cadillac motor with a 255 lph fuel pump. It is possible to overpower a deadhead FPR if you have a strong enough fuel pump with no bypass built in, but typically the pump just can't push past the spring.

Of the two, the return-style FPR is preferred and will give a steadier fuel supply. The fuel pressure will remain constant even if you switch out pumps. With a deadhead FPR, you have to re-adjust the fuel pressure if something changes the pump's flow (i.e. significant voltage change or replace the pump).

 

[BeXtreme]

Bluecat tool is the ****. I'm saying the black box and 411 both will revert to full line pressure once the MAF fails, but the 411 has a custom operating system available to keep that from happening. No such option on the blackbox. The torque calculation model sucks in speed density mode and the PCM knows it so it kinda gets thrown out the window.

This is just not true.

98-2001 black box and 0411 DO revert to full line pressure on the stock OS's if you don't change the settings like is described in my previous posts' linked thread on the HP tuners forum. It is not because the data isn't there for it to function, but because the OS is set up to do that when the MAF is failed. There are options in the OS to turn that off. A 2002 0411 OS will not default to full line pressure if the MAF is failed properly. There ARE custom SD OS's, but those are usually only to allow the 2 and 3 bar MAP sensors so that you can run boost. It is standard to fail the MAF sensor in the OS to revert the system to SD so that you can dial in the VE tables. Most people just let it go to full line pressure while doing this, since it doesn't really hurt anything. It just makes the shifting much harsher at low throttle conditions. I'm running an '02 OS, so I don't have this issue at all.

If you fail the MAF in the tune and then just hook up a line pressure gauge to the trans, you can tune the normal and abuse mode tables to set them properly based on what the PCM thinks the engine is doing.