EFI fuel pump, problems being too big?

[81cutlass]

Thanks for the shameless plug 😛 glad it's helpful!

I also recommend not using a return less setup. I have a return less setup on my fbird and have had issues. Besides running out of fuel pressure under boost and having to scale injector flow rates in the tune as manifold pressure changes you are also at risk of air locking the system. We had an issue where the car ran out of gas and we couldn't it started when refilled. I think the issue was air was stuck in the injectors and rails. The only way we got the problem resolved was when the fitting on the rail was removed so the air could get bled out.

 

[RabbitHoleSS]

Thanks, I have both but I picked returnless because the drop in kit is a returnless setup.I ran both lines when I did the frame before i had ever heard of the drop in kit. So It's not a big deal to swap them over.

If you haven’t bought the parts yet, then steer clear of the return less rails or a non-return system if you’re going to boost it. Not being able to boost reference the FP is a giant PITA tuning situation. And then you need to be able PWM the pump as well which is a bunch more money.

What’s the reason for choosing/wanting a returnless setup?

I can't lie, I hadn't put much thought into a boosted setup and the problems I could cause myself with the dropin kit. I'll be tuning it, and im obviously a novice so that might just be the deciding factor for me.

Thanks for the shameless plug 😛 glad it's helpful!

I also recommend not using a return less setup. I have a return less setup on my fbird and have had issues. Besides running out of fuel pressure under boost and having to scale injector flow rates in the tune as manifold pressure changes you are also at risk of air locking the system. We had an issue where the car ran out of gas and we couldn't it started when refilled. I think the issue was air was stuck in the injectors and rails. The only way we got the problem resolved was when the fitting on the rail was removed so the air could get bled out.

Its a good cheapskate tech channel, it's my favorite genre. I basically plan to copycat what you've done with the sender, just gotta order parts and a metripak crimper.
So if im understanding this right if i used a returnless setup, I'd have to know how much pressure is in the manifold at any given rpm and adjust the tables accordingly? Then pray my undersized pump can overpower the manifold pressure or I risk running lean and pushing air up thru the injector into the system.
I don't think that's really a feasible option with me doing the tooning.
I've tried to be forward thinking while building the car. I thought if I was to upgrade the engine, I'd do it with FI instead of ported heads and raising compression like we'd do with a SBC.
So with that in mind, it looks like I've changed directions again.
I'm glad I posted that original question to the forum that led to this.
You 2 are the some of the better driveway engineers on here, especially when it comes to boosted ls engines. So I'll definitely take your advice.
Ill order the 4.3 monte sender and tank. Any suggestions for fpr? There's a ton of options and I can't see a big difference, I have this in my cart for now.
Aeromotive 13129 Regulator, EFI Bypass, Adjustable (2) -6 inlets, (1) -6 bypass https://www.amazon.com/dp/B004084DBU/?tag=gbody-20

I found the 450 on Amazon for 90$, from the walbro store but that's 30$ cheaper then everywhere else. Anyone know if these are easy to spot fakes? I hate to give away 30$ but I don't wanna blow up my junk because of a cheap pump either.

 

[Supercharged111]

Thanks, I have both but I picked returnless because the drop in kit is a returnless setup.I ran both lines when I did the frame before i had ever heard of the drop in kit. So It's not a big deal to swap them over.

I can't lie, I hadn't put much thought into a boosted setup and the problems I could cause myself with the dropin kit. I'll be tuning it, and im obviously a novice so that might just be the deciding factor for me.

Its a good cheapskate tech channel, it's my favorite genre. I basically plan to copycat what you've done with the sender, just gotta order parts and a metripak crimper.
So if im understanding this right if i used a returnless setup, I'd have to know how much pressure is in the manifold at any given rpm and adjust the tables accordingly? Then pray my undersized pump can overpower the manifold pressure or I risk running lean and pushing air up thru the injector into the system.
I don't think that's really a feasible option with me doing the tooning.
I've tried to be forward thinking while building the car. I thought if I was to upgrade the engine, I'd do it with FI instead of ported heads and lowering compression like we'd do with a SBC.
So with that in mind, it looks like I've changed directions again.
I'm glad I posted that original question to the forum that led to this.
You 2 are the some of the better driveway engineers on here, especially when it comes to boosted ls engines. So I'll definitely take your advice.
Ill order the 4.3 monte sender and tank. Any suggestions for fpr? There's a ton of options and I can't see a big difference, I have this in my cart for now.
Aeromotive 13129 Regulator, EFI Bypass, Adjustable (2) -6 inlets, (1) -6 bypass https://www.amazon.com/dp/B004084DBU/?tag=gbody-20

I found the 450 on Amazon for 90$, from the walbro store but that's 30$ cheaper then everywhere else. Anyone know if these are easy to spot fakes? I hate to give away 30$ but I don't wanna blow up my junk because of a cheap pump either.

Walbro fakes are notorious, so much so that's why I avoided the brand altogether. And Amazon seems to be a great place to get duped for that. I gave up looking at widebands on there for that very reason.

 

[64nailhead]

That regulator is a good one. And if it's in the budget then get it. Regarding the pumps and Amazon/E Bay purchases - the fakes are a crapshoot IMHO.

I found this place 8-9 years ago - https://www.extremepsi.com/store/search.php?mode=search&page=1&keep_https=yes
They cater to the foreign car (ricer)guys, but they only sell genuine stuff if the listing is indicating genuine. I've bought every Walbro and Tial part from them. They are always within 5% of where I can find genuine Walbro and Tial parts anywhere else. And they have more than the website indicates, i.e Tial fire rings, clamps, bots, etc. They are also quite close to me (Philadelphia, PA), so if I order before 11am I have it the next day from USPS for little to no shipping. The moral to the story, if you find a trustworthy vendor, then stick with them because they'll help you out when you need help.

And the drop in kit will work if meets your flow demand, but the returnless setup is..........umm........no bueno.

Jake (81cutlass) put me onto his Viking shock source - good people and saved me $50-80.


To the fuel rail type with a 'Corvette' style filter that acts as a regulator. They work for a mild NA build. But that system was designed for a system that is both PWM the fuel pump and alternator to control fuel flow. I'm guessing you don't want that headache. As mentioned, NA it will work for you - I'm tuning a guys car remotely presently that has that setup and it makes for a whacky looking fuel table. But boosted - yikes - it will scatter your motor in a second if you don't have it managed correctly. A normal FPR that is boost referenced just makes everything so much simpler other than the fuel line plumbing - but it will keep your motor in one piece.

Do you understand what happens in boost to the injector flow due to increased manifold pressure? I can explain if you don't

 

[Supercharged111]

That regulator is a good one. And if it's in the budget then get it. Regarding the pumps and Amazon/E Bay purchases - the fakes are a crapshoot IMHO.

I found this place 8-9 years ago - https://www.extremepsi.com/store/search.php?mode=search&page=1&keep_https=yes
They cater to the foreign car (ricer)guys, but they only sell genuine stuff if the listing is indicating genuine. I've bought every Walbro and Tial part from them. They are always within 5% of where I can find genuine Walbro and Tial parts anywhere else. And they have more than the website indicates, i.e Tial fire rings, clamps, bots, etc. They are also quite close to me (Philadelphia, PA), so if I order before 11am I have it the next day from USPS for little to no shipping. The moral to the story, if you find a trustworthy vendor, then stick with them because they'll help you out when you need help.

And the drop in kit will work if meets your flow demand, but the returnless setup is..........umm........no bueno.

Jake (81cutlass) put me onto his Viking shock source - good people and saved me $50-80.


To the fuel rail type with a 'Corvette' style filter that acts as a regulator. They work for a mild NA build. But that system was designed for a system that is both PWM the fuel pump and alternator to control fuel flow. I'm guessing you don't want that headache. As mentioned, NA it will work for you - I'm tuning a guys car remotely presently that has that setup and it makes for a whacky looking fuel table. But boosted - yikes - it will scatter your motor in a second if you don't have it managed correctly. A normal FPR that is boost referenced just makes everything so much simpler other than the fuel line plumbing - but it will keep your motor in one piece.

Do you understand what happens in boost to the injector flow due to increased manifold pressure? I can explain if you don't

The F-body setup has a regulator in the tank, the filter itself isn't a regulator. The split just gives the excess fuel somewhere to go so it doesn't deadhead the pump, no PWM pumps involved here (but the Mustangs were doing PWM pumps around this time). But the injector flow difference is compensated for in the tune, and in the 411 I'm looking at right now it's only defined for 0-80kpa, f00k that. If it's a vacuum referenced FPR you jam the same value in top to bottom and done and it doesn't matter if you blow the lid off of that table.

 

[RabbitHoleSS]

That regulator is a good one. And if it's in the budget then get it. Regarding the pumps and Amazon/E Bay purchases - the fakes are a crapshoot IMHO.

I found this place 8-9 years ago - https://www.extremepsi.com/store/search.php?mode=search&page=1&keep_https=yes
They cater to the foreign car (ricer)guys, but they only sell genuine stuff if the listing is indicating genuine. I've bought every Walbro and Tial part from them. They are always within 5% of where I can find genuine Walbro and Tial parts anywhere else. And they have more than the website indicates, i.e Tial fire rings, clamps, bots, etc. They are also quite close to me (Philadelphia, PA), so if I order before 11am I have it the next day from USPS for little to no shipping. The moral to the story, if you find a trustworthy vendor, then stick with them because they'll help you out when you need help.

And the drop in kit will work if meets your flow demand, but the returnless setup is..........umm........no bueno.

Jake (81cutlass) put me onto his Viking shock source - good people and saved me $50-80.


To the fuel rail type with a 'Corvette' style filter that acts as a regulator. They work for a mild NA build. But that system was designed for a system that is both PWM the fuel pump and alternator to control fuel flow. I'm guessing you don't want that headache. As mentioned, NA it will work for you - I'm tuning a guys car remotely presently that has that setup and it makes for a whacky looking fuel table. But boosted - yikes - it will scatter your motor in a second if you don't have it managed correctly. A normal FPR that is boost referenced just makes everything so much simpler other than the fuel line plumbing - but it will keep your motor in one piece.

Do you understand what happens in boost to the injector flow due to increased manifold pressure? I can explain if you don't

I would appreciate that. What I think I know and what I actually know aren't the same lol. I assume it goes down because of increased pressure, kinda like when a fuel line is too small.
That holley kits pump isn't pwm compatible, I'm not sure exactly how it works but the fpr is in the tank on the sending unit. It looks kinda like a thermostat. I figured it was just held closed by spring pressure. That's the fpr/filter in the kit.
https://www.holley.com/products/ls_power/fuel_pump_regulator_and_filter/regulators/parts/12-878

The F-body setup has a regulator in the tank, the filter itself isn't a regulator. The split just gives the excess fuel somewhere to go so it doesn't deadhead the pump, no PWM pumps involved here (but the Mustangs were doing PWM pumps around this time). But the injector flow difference is compensated for in the tune, and in the 411 I'm looking at right now it's only defined for 0-80kpa, f00k that. If it's a vacuum referenced FPR you jam the same value in top to bottom and done and it doesn't matter if you blow the lid off of that table.

Does that mean the pcm will only allow you to adjust the table by that small of an amount?

 

[Supercharged111]

I would appreciate that. What I think I know and what I actually know aren't the same lol. I assume it goes down because of increased pressure, kinda like when a fuel line is too small.
That holley kits pump isn't pwm compatible, I'm not sure exactly how it works but the fpr is in the tank on the sending unit. It looks kinda like a thermostat. I figured it was just held closed by spring pressure. That's the fpr/filter in the kit.
https://www.holley.com/products/ls_power/fuel_pump_regulator_and_filter/regulators/parts/12-878

Does that mean the pcm will only allow you to adjust the table by that small of an amount?

For a returnless system using a tuned stock PCM, yes. Your injector flow data would then have to be faked into the VE table. It would suck.

 

[81cutlass]

Thanks, I have both but I picked returnless because the drop in kit is a returnless setup.I ran both lines when I did the frame before i had ever heard of the drop in kit. So It's not a big deal to swap them over.

I can't lie, I hadn't put much thought into a boosted setup and the problems I could cause myself with the dropin kit. I'll be tuning it, and im obviously a novice so that might just be the deciding factor for me.

Its a good cheapskate tech channel, it's my favorite genre. I basically plan to copycat what you've done with the sender, just gotta order parts and a metripak crimper.
So if im understanding this right if i used a returnless setup, I'd have to know how much pressure is in the manifold at any given rpm and adjust the tables accordingly? Then pray my undersized pump can overpower the manifold pressure or I risk running lean and pushing air up thru the injector into the system.
I don't think that's really a feasible option with me doing the tooning.
I've tried to be forward thinking while building the car. I thought if I was to upgrade the engine, I'd do it with FI instead of ported heads and lowering compression like we'd do with a SBC.
So with that in mind, it looks like I've changed directions again.
I'm glad I posted that original question to the forum that led to this.
You 2 are the some of the better driveway engineers on here, especially when it comes to boosted ls engines. So I'll definitely take your advice.
Ill order the 4.3 monte sender and tank. Any suggestions for fpr? There's a ton of options and I can't see a big difference, I have this in my cart for now.
Aeromotive 13129 Regulator, EFI Bypass, Adjustable (2) -6 inlets, (1) -6 bypass https://www.amazon.com/dp/B004084DBU/?tag=gbody-20

I found the 450 on Amazon for 90$, from the walbro store but that's 30$ cheaper then everywhere else. Anyone know if these are easy to spot fakes? I hate to give away 30$ but I don't wanna blow up my junk because of a cheap pump either.

Yeah basically returnless that's not vacuum referenced has in effect non continuous flow rates. The injectors get 'bigger' as the manifold vacuum increases as you gain relative fuel pressure.

In a manifold pressure reference set-up NA you have 42.5 psi of fuel pressure at wide open throttle, no vacuum or with the engine off. At idle with 28" of vacuum you have about 30 psi of fuel pressure relative to the air you breath but it's actually 42psi relative to the air in the manifold because it's at a vacuum.

Returnless setups can be harder to tune because if it's not manifold pressure reference the effective fuel pressure at idle is say 56psi which makes the injectors roughly 10% larger. You have to ramp the injectors size as the air pressure in the manifold changes.

And yeah, walbro or TTI pumps are great but there are a lot of fakes. If you go with one from a reliable seller, I got mine from highflowfuel or from racetronix, where I get my bigger wiring bulkhead parts from, you should be fine. But Amazon and eBay are yikes.

 

[64nailhead]

81cutlass explained the idea of the returnless setup better than I can.

Regarding boost, and why the need for a boost referenced FPR, when boost pressure is present in the manifold it is also applying pressure to the injector tip. And that pressure has to be overcome - basically,
there is a pressure differential between the manifold and fuel system. The fuel supply end of the injector has fuel pressure on it and the other end has manifold pressure on it. The difference between the two is referred to as ‘pressure differential’ in this discussion.

The goal of the referenced FPR regulator is to keep the pressure differential between manifold and fuel system the same for all boost levels. For example , you have a system that runs at 43psi base fuel pressure (set at atmospheric pressure with the engine off.) 43 is now the value to be set as the pressure differential number. At 10 psi of boost the FPR adds that same 10psi to the fuel system to generate 53psi of fuel pressure. At 20 psi of boost the fuel pressure becomes 63psi. I’m sure you get it, but the important piece of puzzle is that the injector is now in a constant pressure differential of 43 psi all the time. And this occurs in vacuum as well, hence the reason why the fuel pressure drops in vacuum to a negative psi.

The negative psi number starts becoming confusing because rarely does anyone reference pressure in negative psi. The most common unit of measure that is simplest is kpa due to the scaling of it. And kpa infers ‘absolute’ pressure rather relative pressure. But that’s another discussion if needed.

Onto injector data consideration and how fuel pressure affects injector flow. All injectors’ flow characteristics are not the same as fuel pressure varies. A Siemens Deka flow rate flow rate change due to fuel pressure variance might be 5-10% more than a Bosch, Multec, Delphi, etc. This makes tuning an injector swap even more demanding at a varying fuel pressure differential. So again, a constant fuel pressure differential across the injector makes for very linear, predictable and most importantly - consistent - tuning.

One variable that is tuned by most every ECU is flow rate changes due to voltage changes. The varying flow rates due to voltage changes are what is entered into most every ECU as ‘injector data’. With this in mind, consider running with a consistent fuel pressure that doesn’t take fuel injector pressure differential into account. Now you are having to adjust for both voltage change and pressure differential change. This situation turns into a 3 dimensional aspect of the tune rather than a 2 dimensional aspect (aspect implies a table). Perhaps the newer factory ECM’s can handle this, and I’ll guess they can, but that is because they have at least one of two things going on or both - they have very specific injector data for all 3 dimensions and/or they have the O2 sensor commanding wild injector duty cycle changes. The factory ECM is probably doing more than what I just referenced.

This leads to a simple question. Why not put in a 1 to 1 vacuum/boost referenced FPR and make this very easy - so easy in fact that all of the big name aftermarket ECM manufacturers can handle - I.e Holley, Haltech, Big Stuff, Fuel Tech, Megasquirt, etc.?


I referenced absolute pressure via relative pressure a couple of paragraphs back. Having a full understanding of the difference between the two is extremely important when trying to understand what is happening in your fuel system and inside your intake. I only mention this, because I either didn’t understand or overlooked this when I first started messing with tuning cars. It was something taught in most every chemistry and physics class through my high school and college classes, but dang, that was 25 years before I needed to know how it applies to tuning a motor on earth lol.

p.s. I typed this post on my IPhone - I’m trying to force myself to be better at using this damn dinky key pad 😉

 

[64nailhead]

Gen 3 truck intake.

You know you can get the factory rails for an early Gen 3 than have a fuel return built into them - with two Amazon fittings that slide onto the supply and return you’re all set with a -8 or -10 supply and a -6 return? I ran that setup to my 1st high 9 second pass before I swapped to the Trailblazer intake. I used the built in FPR without issue. And if you get a Deka injector, then you can space the rails with a thick plastic washers from Lowe’s (that’s my back up plan in the basement).