Interesting fuel injector flow with more fuel pressure info with the Explorer systems.

[rjrobin2002]

While doing a fuel injection swap using the 2000 Explorer 5.0 which uses 65psi fuel pressure and 17 pound injectors i had questions if it could as much power as the 19 pound injector systems.

I had traditionally used the mustang/96-98 explorer system that uses 19 pound injectors and 40 psi fuel pressure and I had people question if my 17 pound injectors on the newer 65 psi system could feed my 351 I put it on.

I found a fuel injector calculator and apparently the 17 pound injector with higher fuel pressure system can handle significantly more hp.

19 pound injectors with 40 PSI can handle 265hp.

17 pound injector with 65 psi can handle 300hp.

Just sharing what I learned today.

 

[bigmuddy]

Good info, so what happens if you apply the same amount of higher pressure to the 19lb injectors can they handle more HP or are they limited for some reason?

 

[rjrobin2002]

I played with that also.

 

[rjrobin2002]

It makes a engine with 19pound injectors able to handle 75 more hp.

But a efi pro would have to chime in on what would need done with the computer, MAF, amd throttle body if you increased the fuel pressure to 65psi on a mustang type system.

I just thought it was an area not well educated to us common folk.

 

[bigmuddy]

It makes a engine with 19pound injectors able to handle 75 more hp.

But a efi pro would have to chime in on what would need done with the computer, MAF, amd throttle body if you increased the fuel pressure to 65psi on a mustang type system.

I just thought it was an area not well educated to us common folk.

Thanks for posting that. I have been told by a local reputable source that the 19lb would easily accomodate a mild build on a 351w EFI engine, never thought to ask about fuel pressure though. Good intel!

Also I am using the stock mustang ECM and a little concerned about how far out of range I may be without a custom tune. Seems like less and less people are tuning this old stuff, either due to availability or the crackdown from the EPA.

 

[rjrobin2002]

Thanks for posting that. I have been told by a local reputable source that the 19lb would easily accomodate a mild build on a 351w EFI engine, never thought to ask about fuel pressure though. Good intel!

Also I am using the stock mustang ECM and a little concerned about how far out of range I may be without a custom tune. Seems like less and less people are tuning this old stuff, either due to availability or the crackdown from the EPA.

Mustang efi on a 351 lightning with gt40 lower,upper and heads only makes 240hp. That's the hp of those early ford lightning that had 351s in them.

That's what I have on my 351, explorer gt 40 heads, explorer gt 40 upper, and ford lightning gt 40 351 lower, so with my cam and header upgrade I may have 275hp, but my injectors with 65 psi fuel pressure is good for 300hp.

 

[jamesroney]

While doing a fuel injection swap using the 2000 Explorer 5.0 which uses 65psi fuel pressure and 17 pound injectors i had questions if it could as much power as the 19 pound injector systems.

I had traditionally used the mustang/96-98 explorer system that uses 19 pound injectors and 40 psi fuel pressure and I had people question if my 17 pound injectors on the newer 65 psi system could feed my 351 I put it on.

I found a fuel injector calculator and apparently the 17 pound injector with higher fuel pressure system can handle significantly more hp.

19 pound injectors with 40 PSI can handle 265hp.

17 pound injector with 65 psi can handle 300hp.

Just sharing what I learned today.

Oh, wow!

Consider that fuel injector static pressure flow rates are calculated at standard temperature and pressure. The standard is 43psi which is about 3 Bar.

So your 17 pound injector flows 17 lbs of fuel into a bucket when the injector is wide open, at 100% duty cycle.
Your 19 pound injector flows 19 lbs of fuel into the same bucket at 100% duty cycle.
Nobody runs an injector at 100% duty cycle, because it can't modulate, and it can only go lean from there. So don't.

If you put 65% more fuel pressure on the top of the injector, (40 psi to 65psi) it will flow more.
If you put more air pressure on the bottom of the injector, (by adding boost) it will flow less.

Fuel maps and engine control algorithms are based on established fuel injector delivery, and intake air flow. If you want to increase the fuel delivery, you have to build a new fuel map. Fox 5.0 guys cheated this for years by running a re-calibrated mass air meter that was tuned to match their injectors. It was "easier" to buy a set of 24lb injectors and a 24lb mass air meter and you didn't have to touch the computer, or the fuel system.
The same increase could be had by increasing fuel pressure...but you would need a better fuel pump, and a different FPR. And then you would have to recalibrate your MAF meter to match your new fuel delivery.

The same problem happens when you add forced induction. In order to stay within the EEC-4 maps, you would need to install an adjustable FPR to bump up the pressure when the supercharger starts working.

But nobody in their right mind is trying to build power with a naturally aspirated 351. The beauty of the 351 Lightning is Reliable, consistent, and durable horsepower, using off the shelf components. Why ruin that?

 

[bigmuddy]

Mustang efi on a 351 lightning with gt40 lower,upper and heads only makes 240hp. That's the hp of those early ford lightning that had 351s in them.

That's what I have on my 351, explorer gt 40 heads, explorer gt 40 upper, and ford lightning gt 40 351 lower, so with my cam and header upgrade I may have 275hp, but my injectors with 65 psi fuel pressure is good for 300hp.

Agreed, I was after that same engine more or less for good all around power. My cam profile is different but I think it will put me likely in the 250-300. Although 300hp may be optimistic?

 

[EFI Guy]

Ford uses a base pressure of 39.15 psi instead of 43 like GM. Those later injectors flow about the equivalent of 23lb/hr at 65psi. You can take it to 350 but I wouldn't go north of that (15% safety margin).
A cam change with the GT40 package can get you 300 and still be mild-mannered. A nice fat torque curve means more to me than HP numbers though. Feel free to chat with me on the phone if you want to know what is possible with the PCM.

 

[bigmuddy]

Thanks, I will reach out through your email as I don't have your contact phone number.

 

[73azbronco]

As an aside to anyone new begining to work on EFI, the very first step in diagnosing EFI problems, check fuel pressure. It all starts there.

 

[nvrstuk]

Oh, wow!

Consider that fuel injector static pressure flow rates are calculated at standard temperature and pressure. The standard is 43psi which is about 3 Bar.

So your 17 pound injector flows 17 lbs of fuel into a bucket when the injector is wide open, at 100% duty cycle.
Your 19 pound injector flows 19 lbs of fuel into the same bucket at 100% duty cycle.
Nobody runs an injector at 100% duty cycle, because it can't modulate, and it can only go lean from there. So don't.

If you put 65% more fuel pressure on the top of the injector, (40 psi to 65psi) it will flow more.
If you put more air pressure on the bottom of the injector, (by adding boost) it will flow less.

Fuel maps and engine control algorithms are based on established fuel injector delivery, and intake air flow. If you want to increase the fuel delivery, you have to build a new fuel map. Fox 5.0 guys cheated this for years by running a re-calibrated mass air meter that was tuned to match their injectors. It was "easier" to buy a set of 24lb injectors and a 24lb mass air meter and you didn't have to touch the computer, or the fuel system.
The same increase could be had by increasing fuel pressure...but you would need a better fuel pump, and a different FPR. And then you would have to recalibrate your MAF meter to match your new fuel delivery.

The same problem happens when you add forced induction. In order to stay within the EEC-4 maps, you would need to install an adjustable FPR to bump up the pressure when the supercharger starts working.

But nobody in their right mind is trying to build power with a naturally aspirated 351. The beauty of the 351 Lightning is Reliable, consistent, and durable horsepower, using off the shelf components. Why ruin that?

uh-oh... here we go again.... I pulled a sentence out of your post so we can visit it...again!! lol "But nobody in their right mind is trying to build power with a naturally aspirated 351. The beauty of the 351 Lightning is Reliable, consistent, and durable horsepower, using off the shelf components. Why ruin that? Great info in the rest of your post.


WHY do you think building power with a naturally aspirated 351W is a disastrous thing to do?? A built 351W IS A RELIABLE, CONSISTENT, and DURABLE HORSEPOWER" building powerplant! ALL the components are OFF THE SHELF and are probably ordered in faster than the stock parts which aren't "off the shelf" anymore because nobody stocks 351W stuff because it's 26-50+ yrs old! OUTDATED, not on the shelf.. It's so easy and cheap to make an extra 100-150 HP to a 351W block and have it last for 150K miles.

How do I know this? How can I type this and back it up? Because I've built them for decades- and so have thousands of others!! The 351W block is extremely durable, the bolt pattern for the heads is fantastic (same as 5.0 but larger dia bolts) so head gasket failure is NOT an issue. I could go on for paragraphs but come on James, you are putting out some good info then follow up with a statement like this about 351W's... again. It's not that we disagree, it's that you really are just plain wrong when you say you ruin a 351W and aren't in your right mind trying to build power with a 351W.

No apologies as you and probably tens of thousands of others who have built reliable 351W's disagree on this point- again.

Guys here need accurate information.

 

[Broncobowsher]

Back in the day (before custom tunes for EEC-IV) the supercharger kits got by with a rising rate fuel pressure regulator that spiked the fuel pressure under boost. Not just the 1:1 ratio of a normal pressure regulator (constant delta across the injector) Once you got into boost the fuel pressure would rise several PSI (3 or 4 I think was common) per pound of boost. 10 pounds of boost would add 40 PSI of pressure to shove extra fuel through the stock injector. Add in supplemental inline fuel pumps just to keep the flow and pressure both up. Those early days of hackery.

I remember a friend bought a Camaro that was built up that way. MSD boost retard, multi pumps, etc. Gutted it all out, kept the supercharger. Bigger injectors and a proper tune and it went from a lot of unrefined power into more power and drivable. Same thing for the mustangs.

I understand why the OEMs started spiking fuel pressure, better spray, less emissions. Small injector for better control.

 

[bmc69]

Back in the day (before custom tunes for EEC-IV) the supercharger kits got by with a rising rate fuel pressure regulator that spiked the fuel pressure under boost.

I'm still doing that on some builds. That's how the supercharger and EFI is set up on the flathead V8 in my 69 Bronco, for example. It's a speed-density (Holley HP) system with a 3-bar MAP and an Aeromotive fuel pressure regulator.

 

[jamesroney]

uh-oh... here we go again.... I pulled a sentence out of your post so we can visit it...again!! lol "But nobody in their right mind is trying to build power with a naturally aspirated 351. The beauty of the 351 Lightning is Reliable, consistent, and durable horsepower, using off the shelf components. Why ruin that? Great info in the rest of your post.


WHY do you think building power with a naturally aspirated 351W is a disastrous thing to do?? A built 351W IS A RELIABLE, CONSISTENT, and DURABLE HORSEPOWER" building powerplant! ALL the components are OFF THE SHELF and are probably ordered in faster than the stock parts which aren't "off the shelf" anymore because nobody stocks 351W stuff because it's 26-50+ yrs old! OUTDATED, not on the shelf.. It's so easy and cheap to make an extra 100-150 HP to a 351W block and have it last for 150K miles.

How do I know this? How can I type this and back it up? Because I've built them for decades- and so have thousands of others!! The 351W block is extremely durable, the bolt pattern for the heads is fantastic (same as 5.0 but larger dia bolts) so head gasket failure is NOT an issue. I could go on for paragraphs but come on James, you are putting out some good info then follow up with a statement like this about 351W's... again. It's not that we disagree, it's that you really are just plain wrong when you say you ruin a 351W and aren't in your right mind trying to build power with a 351W.

No apologies as you and probably tens of thousands of others who have built reliable 351W's disagree on this point- again.

Guys here need accurate information.

Because there is nothing that a 351w can do that a 408w can't do better. And in the factory block, a square 4"x4" is well optimized. I am a big proponent of the F4TE-block as a foundation for a build.

But the break point comes when you need new pistons. At that point, it is not economical to invest further into the 3.5 stroke.

Of course you can get an additional 100-150HP out of a 351W...but I am TRYING to keep things in context!!! I am talking about Horsepower that takes you beyond the capability of the EEC-4. There are many examples of the A9L computer up to 700HP.

Maybe you have me confused with someone else? I only advocate an 8.2 deck when the Windsor doesn't fit. I am perfectly aware that the reduced main journal 351w is the foundation for the NASCAR 355 that ran for years, (and won a lot of races.).

 

[Broncobowsher]

I'm still doing that on some builds. That's how the supercharger and EFI is set up on the flathead V8 in my 69 Bronco, for example. It's a speed-density (Holley HP) system with a 3-bar MAP and an Aeromotive fuel pressure regulator.

I didn't think anyone made the rising rate regulators anymore. A standard boost referenced regulator is still common. 10 pounds of boost adds 10 pounds of fuel pressure. Keeps a steady pressure drop across the injector (the output is into a high pressure area, or a vacuum depending on where the throttle is at). With a tunable EFI there is no need for the wild card of those bandaid fixes of the past.

 

[nvrstuk]

Maybe I did James and apologize if I did. I am a believer in stroking 'em. I haven't built a 351 w/o a longer crank since 1985! lol Bit cranky lately since my small journeled 351W aftermarket block (464ci) was down for 10 mo due to Ford Performance and now 5 weeks after I rebuilt it due to tuners taking your money and being "too busy" to tune...

Anyway, hope the week treats everyone well.

 

[DirtDonk]

I am a believer in stroking 'em. I haven't built a 351 w/o a longer crank since 1985!

Ooh, I feel a pun coming on…

Bit cranky lately…

Oop, there it is!

 

[nvrstuk]

THAT was a quick response!!

Best one I've had in a while!

Have a great week Paul.

(and yes, I was aware when I typed it) lol

 

[ba123]

You all are just not good for my wallet.

It’ll be interesting to see what kind of HP my little 5.0 puts out if I ever get to drive it.

All these fuel discussions, size matters discussions, stroke my... big injectors, blah blah… I'd love to go pwm returnless on my fuel system but I think the last thing I need is to add one more thing to my list.