Converting NB to return fuel style
Joined: Apr 2014
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From: Beaverton, USA
You use a vacuume referenced FPR to MAINTAIN constant fuel pressure. For every 1lb of manifold pressure on a fixed pressure system the effective fuel pressure at the injector tip is reduced by 1lb. The same effect happens in vacuum. (Most OEM FPR's are 1:1)
The NB uses a returnless fuel system to comply with emissions standards.
The NB uses a returnless fuel system to comply with emissions standards.
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You use a vacuume referenced FPR to MAINTAIN constant fuel pressure. For every 1lb of manifold pressure on a fixed pressure system the effective fuel pressure at the injector tip is reduced by 1lb. The same effect happens in vacuum. (Most OEM FPR's are 1:1)
The NB uses a returnless fuel system to comply with emissions standards.
The NB uses a returnless fuel system to comply with emissions standards.
EDIT: Aidan beat me to it.
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Joined: Jan 2015
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Yes and as stated before so you can use a rising rate FPR which again means you can use a smaller injector to achieve the HP goal. Which means you will have an even smaller injector to control at idle.
The difference is about 10lbs of fuel pressure at idle on an engine that has healthy vacuum of 40kpa(60kpa) (invert of 60kpa). So lets say 1000cc injectors at 45psi flow 1000cc and at 35psi they flow 880cc.
So its about a 10% difference. Admittedly that's a difference...... but you still have a 900cc injector at minimum. Its still a big *** injector that you have to control at idle. It may no longer be Nicki Minaj big but its Jessica Biel big. Either way you are in for a ride.
However, if you know you are going to be using 60psi as a base with a vacuum FPR and you need 1000cc you start with 850cc which gives you 1000cc at 60psi. Well at 50psi you still get 900cc.
So the only way you make the argument that the vacuum FPR will help idle by having lower injector flow to control is if you use a rising rate FPR that can get to say 90psi. Then you can use a 750cc injector to get to 1000cc at 90psi. And that injector will flow about 670cc at 35psi.
So a 670cc injector will be easier to tune at idle and maybe is not considered big *** anymore. Maybe now its only Jennifer Garner big. But this brings me back to the point about using mechanical parts to do the job electronic parts can do. I have read several times on this forum of success stories using 1000cc ID injectors and good idle fuel control. Of course that was with a good ECU. Quality components go a long way. And I've been reading on this site about a new generation of injectors that are even better. So why go to the trouble of relying on a mechanical part to make sure that you have enough fuel when you need it?
You can tell i have nothing better to do on a Sunday morning as I drink my coffee.
The difference is about 10lbs of fuel pressure at idle on an engine that has healthy vacuum of 40kpa
So its about a 10% difference. Admittedly that's a difference...... but you still have a 900cc injector at minimum. Its still a big *** injector that you have to control at idle. It may no longer be Nicki Minaj big but its Jessica Biel big. Either way you are in for a ride.
However, if you know you are going to be using 60psi as a base with a vacuum FPR and you need 1000cc you start with 850cc which gives you 1000cc at 60psi. Well at 50psi you still get 900cc.
So the only way you make the argument that the vacuum FPR will help idle by having lower injector flow to control is if you use a rising rate FPR that can get to say 90psi. Then you can use a 750cc injector to get to 1000cc at 90psi. And that injector will flow about 670cc at 35psi.
So a 670cc injector will be easier to tune at idle and maybe is not considered big *** anymore. Maybe now its only Jennifer Garner big. But this brings me back to the point about using mechanical parts to do the job electronic parts can do. I have read several times on this forum of success stories using 1000cc ID injectors and good idle fuel control. Of course that was with a good ECU. Quality components go a long way. And I've been reading on this site about a new generation of injectors that are even better. So why go to the trouble of relying on a mechanical part to make sure that you have enough fuel when you need it?
You can tell i have nothing better to do on a Sunday morning as I drink my coffee.
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Joined: Apr 2014
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From: Beaverton, USA
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Resurrect:
While traditionally a return style fuel setup is used on NA, if using it with conjunction to a surge tank to prevent starvation, is it still passé to use an adjustable FPR to feed the T of a dual feed configuration, or is a straight through the rail to FPR still preferred?
While traditionally a return style fuel setup is used on NA, if using it with conjunction to a surge tank to prevent starvation, is it still passé to use an adjustable FPR to feed the T of a dual feed configuration, or is a straight through the rail to FPR still preferred?
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In this thread, and in Andrew's VVT into NA thread, 90* fittings are shown or mentioned to attach rubber hose to the hard lines. The only ones I have found are made to go to nylon hose, not rubber hose. Just use those? or is there some special P/N's for the connectors to the rubber hose?
Andrew, I am taking your advice and I picked up a second, 5/16" supply hose from a guy parting out a car. So, I will need the connectors for both ends of that line, as well as the supply line.
Also, @SchmoozerJoe has shown a FPR from a Geo Tracker that seems to mimic the FPR from NB1 Euro version. He may divulge the P/N? AND, he has one for sale. Maybe @EO2K is still looking for one. I opted to purchase a used Euro one from England for mine '99.
EDIT: I has tagged ERAT, but meant to tag EO2K. Now fixed with Edit.
Andrew, I am taking your advice and I picked up a second, 5/16" supply hose from a guy parting out a car. So, I will need the connectors for both ends of that line, as well as the supply line.
Also, @SchmoozerJoe has shown a FPR from a Geo Tracker that seems to mimic the FPR from NB1 Euro version. He may divulge the P/N? AND, he has one for sale. Maybe @EO2K is still looking for one. I opted to purchase a used Euro one from England for mine '99.
EDIT: I has tagged ERAT, but meant to tag EO2K. Now fixed with Edit.
Last edited by DNMakinson; Jul 19, 2016 at 04:16 PM. Reason: Wrong callout
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This allows the fuel line to point down, and the vacuum line to come over the top.
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