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Old 10-31-2018, 07:16 PM
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You aren't running the stock regulator are you?
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Old 11-01-2018, 07:15 AM
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Originally Posted by ridethecliche
Are you sure you have it programmed right in tune? 100% duty cycle with those injectors and that pump in a miata would be a **** ton of power. More so than that plot hints at.
Which parameters would be programmed wrong? We talking deadtime and voltage correction? I’ll take another look at both.

Originally Posted by SpartanSV
You aren't running the stock regulator are you?
Yes, stock regulator. Other than the fuel pump (with a hardwired relay), the injectors, and I guess technically the ECU (DIYPNP), the fuel system is 100% stock.
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Old 11-01-2018, 12:13 PM
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Andrew mentions issues with the dw300 and a stock regulator. Deatschwerks Fuel Pumps (DW100/200/300)

Additionally, the stock NB regulator tries to achieve 60 psi in the feed line no matter the conditions. If you add 27 psi of boost to the intake you effectively have 33 psi of fuel pressure. That's how you max out ID1000s and a dw300 at your power.
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Old 11-01-2018, 12:30 PM
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Originally Posted by SpartanSV
Andrew mentions issues with the dw300 and a stock regulator. Deatschwerks Fuel Pumps (DW100/200/300)

Additionally, the stock NB regulator tries to achieve 60 psi in the feed line no matter the conditions. If you add 27 psi of boost to the intake you effectively have 33 psi of fuel pressure. That's how you max out ID1000s and a dw300 at your power.
Yeah, you've got effectively 30 psi at WOT and an unregulated 80-90 psi at idle. You need a proper regulator.

--Ian
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Old 11-01-2018, 01:01 PM
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Makes sense! Thanks guys. I’ll order a regulator tonight. If anyone has any brand/model recommendations, feel free to drop them here.
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Old 11-01-2018, 01:27 PM
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Ah right , that entire ditty. I suppose I'll run into that if I push too much harder as well.
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Old 11-01-2018, 02:16 PM
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Originally Posted by Carloverx
Makes sense! Thanks guys. I’ll order a regulator tonight. If anyone has any brand/model recommendations, feel free to drop them here.
You should probably put your wallet away and do some reading on converting to a return style fuel system.
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Old 11-01-2018, 04:27 PM
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Originally Posted by SpartanSV
You should probably put your wallet away and do some reading on converting to a return style fuel system.
This.

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Old 11-02-2018, 04:38 PM
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Originally Posted by SpartanSV
You should probably put your wallet away and do some reading on converting to a return style fuel system.

Since this aspect of the fuel system is completely new to me, I did a good amount of reading today. That said, I have a few questions:

1. Outside of stabilizing the flow of fuel to the injector, what would be the benefit of going to a return style system? Is the point that it flows more? (And if so, can someone explain how?)

2. If I were to follow the steps in the thread linked below, would I still be limited to the NA FPR PSI? Or does the NA FPR and its vacuum operation allow for it to flow more than an NB in-tank FPR?
https://www.miataturbo.net/diy-turbo...l-style-74629/

3. Assuming the NA FPR can provide enough flow under high boost, because I’m running an aftermarket ECU, I wouldn’t need an adjustable FPR, correct?

In conclusion, I think I may need to read more because I’m not completely following the benefits of converting to returnless at this point, over simply installing an AFPR. :-/
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Old 11-02-2018, 04:58 PM
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The stock regulator is in the fuel tank. You can't easily put an AFPR in there, so you're looking at doing at least some rework of the fuel system no matter what. There's basically two options:

A) convert to a return system like an NA.

B) move the regulator down next to the charcoal canister and use it to drive the non-return line from there like FM does in their "big fuel kit".

If you do B, you will probably need fuel pulse damper(s) up in the engine bay.

--Ian
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Old 11-02-2018, 06:32 PM
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What about what Savington did with his 452hp NB?
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Old 11-02-2018, 08:52 PM
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To your questions:

1. and 2. The idea of a referenced FPR is that, as boost goes up, so does fuel pressure. That means more flow. The non-referenced (or atmosphere referenced to be more precise) flows more up to roughly 15 psi boost. After that, the manifold referenced system provides more fuel.

It is a misnomer to say that the NA is "vacuum referenced". It is "manifold referenced". Therefore, it is vacuum referenced only when there is less than one atmosphere (100kPa) in the intake manifold.

3. Yes.

You can also look in my build thread for how I did the conversion. I did use a full size return line, and I did not add extra pressure beyond the NA FPR (or, more precisely, a FPR from a UK NA). Depends on how much more fuel you need. Since you have the big injectors, and you are running quite a bit of boost,

Whether your pump is over-powering your regulator, or would the NA regulator, I don't know, but it has been discussed how big you can go before you need an aftermarket FPR.
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Old 11-03-2018, 12:08 AM
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Originally Posted by DNMakinson
To your questions:

1. and 2. The idea of a referenced FPR is that, as boost goes up, so does fuel pressure. That means more flow. The non-referenced (or atmosphere referenced to be more precise) flows more up to roughly 15 psi boost. After that, the manifold referenced system provides more fuel.

It is a misnomer to say that the NA is "vacuum referenced". It is "manifold referenced". Therefore, it is vacuum referenced only when there is less than one atmosphere (100kPa) in the intake manifold.

3. Yes.

You can also look in my build thread for how I did the conversion. I did use a full size return line, and I did not add extra pressure beyond the NA FPR (or, more precisely, a FPR from a UK NA). Depends on how much more fuel you need. Since you have the big injectors, and you are running quite a bit of boost,

Whether your pump is over-powering your regulator, or would the NA regulator, I don't know, but it has been discussed how big you can go before you need an aftermarket FPR.
Great info! But here’s what I’m struggling with: Why does it matter if my fuel pump is over powering my FPR? Wouldn’t that be a problem of TOO MUCH fuel? I’m my case, isn’t it nearly the opposite, in that the FPR is actually choking the flow of fuel?

In other words, most people add a big fuel pump and then the FPR can’t stop enough fuel from getting to the injectors. Creating a rich state. In my case, the engine is consuming more fuel than the FPR is allowing for. (At least that’s my interpretation of everyone’s comments).

I know it’s been repeatedly discussed about how big of a fuel pump you can go until you over power the stock FRP, but aren’t those discussions regarding the RICH scenario where you’re getting too much fuel? Is there information as readily available regarding when the stock FPR becomes the choke point creating a lean scenario?

Thanks again for everyone’s insight. I apologize for my ignorance on the topic. I’m catching up as fast as possible

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Old 11-03-2018, 12:38 AM
  #154  
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Originally Posted by Carloverx


Great info! But here’s what I’m struggling with: Why does it matter if my fuel pump is over powering my FPR? Wouldn’t that be a problem of TOO MUCH fuel? I’m my case, isn’t it nearly the opposite, in that the FPR is actually choking the flow of fuel?

In other words, most people add a big fuel pump and then the FPR can’t stop enough fuel from getting to the injectors. Creating a rich state. In my case, the engine is consuming more fuel than the FPR is allowing for. (At least that’s my interpretation of everyone’s comments).

I know it’s been repeatedly discussed about how big of a fuel pump you can go until you over power the stock FRP, but aren’t those discussions regarding the RICH scenario where you’re getting too much fuel? Is there information as readily available regarding when the stock FPR becomes the choke point creating a lean scenario?

Thanks again for everyone’s insight. I apologize for my ignorance on the topic. I’m catching up as fast as possible

The problem with the pump overwhelming the FPR is that the fuel is then unregulated. Yes, you can compensate for higher pressure by shortening the idle, but an unregulated pump does not produce a consistent pressure. As things like voltage and temperature change, the pump performance changes, so the fuel pressure at idle changes, and thus the amount of error is not consistent.

As an example, say you have the regulator set to 60 psi, but the pump produces so much fuel when it's at 14.5 volts that the regulator can't keep up, so the pressure spikes to 80 psi. You go into the VE table and change the cells around idle to compensate. Then a few months later it's December. Temperature has dropped, so the fuel is more viscous and the pump has a harder time pumping. You're running the heater, blower motor, and defroster, so there's a lot more demand on the alternator. With the lower temperature the battery is also not performing as well, so you're only get 13.0 volts at idle. The pump performance sags, it can only do 60 psi, and now your VE tables are 25% too lean at idle, and the car starts stalling at stoplights.

Overwhelming the FPR isn't going to blow the motor up, but it will make it a PITA to get the car running consistently well around town. It hurts drivability.

--Ian
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Old 11-03-2018, 09:23 AM
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Originally Posted by codrus
The problem with the pump overwhelming the FPR is that the fuel is then unregulated. Yes, you can compensate for higher pressure by shortening the idle, but an unregulated pump does not produce a consistent pressure. As things like voltage and temperature change, the pump performance changes, so the fuel pressure at idle changes, and thus the amount of error is not consistent.

As an example, say you have the regulator set to 60 psi, but the pump produces so much fuel when it's at 14.5 volts that the regulator can't keep up, so the pressure spikes to 80 psi. You go into the VE table and change the cells around idle to compensate. Then a few months later it's December. Temperature has dropped, so the fuel is more viscous and the pump has a harder time pumping. You're running the heater, blower motor, and defroster, so there's a lot more demand on the alternator. With the lower temperature the battery is also not performing as well, so you're only get 13.0 volts at idle. The pump performance sags, it can only do 60 psi, and now your VE tables are 25% too lean at idle, and the car starts stalling at stoplights.

Overwhelming the FPR isn't going to blow the motor up, but it will make it a PITA to get the car running consistently well around town. It hurts drivability.

--Ian
Got it, that all makes complete sense. That said, would overwhelming a FPR with too much fuel result in a lean scenario under high load? If not, then long story short, I’m still not following how a return style setup would benefit the problem at hand.

Furthermore, if I am overpowering the stock FPR with too much fuel, then replacing the FPR with an AFPR may not even fix the problem, UNLESS the stock FPR, even when possibly overpowered, is still restricting fuel.

If that’s accurate, my plan is to remove the OEM in-tank FPR, grab a $30 AFPR kit off eBay (for testing), install it under the hood, and bump up the base pressure by 10psi. The only question there is whether the stock fuel system will have any issues with the full force of the fuel pump running from the tank all the way to the engine, since before it was pressure regulated long before traveling the length of the car.
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Old 11-03-2018, 10:17 AM
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I apologize for bringing up the over-powering subject. I was not looking to confuse, just wanted to let you know there was another variable to consider, not for your present set-up, but for your improved set-up.
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Old 11-03-2018, 12:35 PM
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You can get a real regulator and set it to stock base pressure 60psi. When you make 30psi of boost, you will have 90psi of fuel pressure because of the real regulator you bought (probably around $150.) As Ian and Andrew taught me.
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Old 11-03-2018, 02:30 PM
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Originally Posted by Carloverx


Got it, that all makes complete sense. That said, would overwhelming a FPR with too much fuel result in a lean scenario under high load? If not, then long story short, I’m still not following how a return style setup would benefit the problem at hand.

Furthermore, if I am overpowering the stock FPR with too much fuel, then replacing the FPR with an AFPR may not even fix the problem, UNLESS the stock FPR, even when possibly overpowered, is still restricting fuel.

If that’s accurate, my plan is to remove the OEM in-tank FPR, grab a $30 AFPR kit off eBay (for testing), install it under the hood, and bump up the base pressure by 10psi. The only question there is whether the stock fuel system will have any issues with the full force of the fuel pump running from the tank all the way to the engine, since before it was pressure regulated long before traveling the length of the car.
There are two unrelated problems with your setup. Pressure regulators work by mechanically comparing the pressure on two sides of a diaphragm. One side of the stock regulator has pressurized fuel on it, the other is the "reference", and the regulator opens or closes a relief valve in order to have those two pressures be equal. Your first problem is caused by the fact that the factory regulator has this reference open to the ambient pressure inside the fuel tank, meaning that it always produces a fuel pressure that is ~ 60 psi higher than whatever the ambient air pressure is.

Injectors work off a pressure difference -- subtract the pressure in the intake manifold from the pressure in the fuel rail, and that's how much pressure there is trying to squirt fuel out when they are open. With a naturally aspirated engine, the max pressure in the intake manifold is the same as ambient, meaning that there is always at least a 60 psi difference (and more than that when the manifold is in vacuum). With a turbo car, you have the ability to raise the manifold pressure above ambient. 27 psi of boost means that the manifold is 27 psi above ambient, and if the manifold is only 60 psi above ambient then you only have 33 psi pushing fuel out. Since you've only got half the effective fuel pressure, your id1000s will only flow half as much fuel as they would if you had 60. This is why you're running lean, the system as currently set up simply cannot supply enough fuel.

The factory setup on an NA, and what most people use for aftermarket regulators is to have the reference side of the regulator connected to a vacuum line, so that it is the same pressure as the intake manifold. This means that the regulator will produce a fuel pressure which is always a fixed delta higher than MAP. This means that as the turbo adds boost pressure to the intake manifold, the regulator adds fuel pressure to the fuel rail to balance it out. Your injectors thus always see the same relative pressure and you don't lose fuel capacity.

The second problem with your current setup is the "overwhelming the regulator" one. It is a problem that manifests not with high power loss of capacity, but with unpredictable low power response, and thus drivability problems.

To fix both problems you need to install a MAP-referenced regulator which is larger than the stock NB one and can handle the larger volume of fuel that the aftermarket pump produces. I don't know if a stock NA regulator will do that or not, I have an AEM. You then need to mount that regulator somewhere, because it can't go in the tank.

On a stock NB, the in-tank pump pressurizes a line that exits the tank, flows to the filter (mounted down by the passenger rear wheel), and then splits into a tee. One half of that tee goes back into the tank and to the stock regulator, the other half goes forward through the hard line to the engine bay, to the fender-mounted pulse damper, and then to the fuel rail where it dead-ends. You have two choices about how to set this up:

- The first is to put the new regulator up in the engine bay, on the firewall for example. To do this you need to remove the tee at the back, run the outlet of the filter to the hard line, drill/tap a second port in the rail, run a line from there to the regulator input, then run the regulator output to a new return line that you run underneath the car. That new return line then goes to the port on the tank that isn't being used any more. This is how the fuel routes on an NA.

- The second is to put the regulator next to the fuel filter, just after the tee, in the return line to the tank and leave everything going forwards with the same config. This is how FM does it with their "big fuel kit" (except that they also replace everything going forward with -6 AN for more fuel flow. It's somewhat debatable as to at what power level you need that -6 line, vs the roughly 5/16 stock line).

Note that except for the steel hard lines, the stock lines are all plastic with quick disconnect fittings. They don't really bend to new routings and you can't easily shorten them, so to change them you're basically replacing them with rubber and getting hose-barb-to-quick-disconnect fittings from Dorman. You need high pressure fuel injection hose.

Most people on this forum recommend adding the return line. The FM-style routing works (that's what's in my car), but it's not clear if it'll work with all regulators or if the AEM that they supply is special in some way. It also tends to produce pressure pulses when the injectors open, this is what the pulse dampers are for, they smooth them out.

In either case, you need a lot more than a $30 AFPR kit from ebay. Note also that you need to remove the stock regulator from the tank, and if you're going to run the car on track you need to replace it with a short piece of submersible fuel hose (not regular hose) in order to return the fuel to the baffled area that the pickup goes into. Otherwise it'll go lean in hard left-handers when you drop below about half a tank of fuel.

--Ian
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Old 11-05-2018, 01:58 PM
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Originally Posted by codrus
There are two unrelated problems with your setup. Pressure regulators work by mechanically comparing the pressure on two sides of a diaphragm. One side of the stock regulator has pressurized fuel on it, the other is the "reference", and the regulator opens or closes a relief valve in order to have those two pressures be equal. Your first problem is caused by the fact that the factory regulator has this reference open to the ambient pressure inside the fuel tank, meaning that it always produces a fuel pressure that is ~ 60 psi higher than whatever the ambient air pressure is.

Injectors work off a pressure difference -- subtract the pressure in the intake manifold from the pressure in the fuel rail, and that's how much pressure there is trying to squirt fuel out when they are open. With a naturally aspirated engine, the max pressure in the intake manifold is the same as ambient, meaning that there is always at least a 60 psi difference (and more than that when the manifold is in vacuum). With a turbo car, you have the ability to raise the manifold pressure above ambient. 27 psi of boost means that the manifold is 27 psi above ambient, and if the manifold is only 60 psi above ambient then you only have 33 psi pushing fuel out. Since you've only got half the effective fuel pressure, your id1000s will only flow half as much fuel as they would if you had 60. This is why you're running lean, the system as currently set up simply cannot supply enough fuel.

The factory setup on an NA, and what most people use for aftermarket regulators is to have the reference side of the regulator connected to a vacuum line, so that it is the same pressure as the intake manifold. This means that the regulator will produce a fuel pressure which is always a fixed delta higher than MAP. This means that as the turbo adds boost pressure to the intake manifold, the regulator adds fuel pressure to the fuel rail to balance it out. Your injectors thus always see the same relative pressure and you don't lose fuel capacity.

The second problem with your current setup is the "overwhelming the regulator" one. It is a problem that manifests not with high power loss of capacity, but with unpredictable low power response, and thus drivability problems.

To fix both problems you need to install a MAP-referenced regulator which is larger than the stock NB one and can handle the larger volume of fuel that the aftermarket pump produces. I don't know if a stock NA regulator will do that or not, I have an AEM. You then need to mount that regulator somewhere, because it can't go in the tank.

On a stock NB, the in-tank pump pressurizes a line that exits the tank, flows to the filter (mounted down by the passenger rear wheel), and then splits into a tee. One half of that tee goes back into the tank and to the stock regulator, the other half goes forward through the hard line to the engine bay, to the fender-mounted pulse damper, and then to the fuel rail where it dead-ends. You have two choices about how to set this up:

- The first is to put the new regulator up in the engine bay, on the firewall for example. To do this you need to remove the tee at the back, run the outlet of the filter to the hard line, drill/tap a second port in the rail, run a line from there to the regulator input, then run the regulator output to a new return line that you run underneath the car. That new return line then goes to the port on the tank that isn't being used any more. This is how the fuel routes on an NA.

- The second is to put the regulator next to the fuel filter, just after the tee, in the return line to the tank and leave everything going forwards with the same config. This is how FM does it with their "big fuel kit" (except that they also replace everything going forward with -6 AN for more fuel flow. It's somewhat debatable as to at what power level you need that -6 line, vs the roughly 5/16 stock line).

Note that except for the steel hard lines, the stock lines are all plastic with quick disconnect fittings. They don't really bend to new routings and you can't easily shorten them, so to change them you're basically replacing them with rubber and getting hose-barb-to-quick-disconnect fittings from Dorman. You need high pressure fuel injection hose.

Most people on this forum recommend adding the return line. The FM-style routing works (that's what's in my car), but it's not clear if it'll work with all regulators or if the AEM that they supply is special in some way. It also tends to produce pressure pulses when the injectors open, this is what the pulse dampers are for, they smooth them out.

In either case, you need a lot more than a $30 AFPR kit from ebay. Note also that you need to remove the stock regulator from the tank, and if you're going to run the car on track you need to replace it with a short piece of submersible fuel hose (not regular hose) in order to return the fuel to the baffled area that the pickup goes into. Otherwise it'll go lean in hard left-handers when you drop below about half a tank of fuel.

--Ian
Awesome stuff. Thanks so much Ian. This really helped close some of the gaps.

i digested your post for a day and then attempted to make a basic diagram of some of your key points. See below.



If my understanding is correct, I’m likely going to attempt the FM style setup. It may not have the optimized drivability of the full return style, but the reduced complexity is worth it in my case. Plus, if I do decide to go full return, it won’t have been too much wasted work. Thanks again!

Last edited by Carloverx; 11-05-2018 at 04:40 PM.
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Old 11-08-2018, 12:52 AM
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I run the returnless setup and drivability is good. Savington has a nice regulator, and it's a good deal, I bought my pump from him too. Best to follow Sav's advice IMHO, even though I did it slightly different. I wanted a 90, and I blocked one port on the regulator meant for a return system. But mine is unusual and I am comfortable making/working with the PA12 line.
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