I have a B35 intake to install. It came with the fuel rail from a 735i. I like the setup with the fuel lines. It would make for cleaner fuel line routing. But this fuel rail has no cold start valve line. I was thinking of getting a brass "T" splitter and splitting the supply line to the CSV and the fuel rail. I can't think of a reason why the CSV would have to be supplied from the fuel rail.
Thoughts? Experience?
TIA
Rich
Anyone use/ing a B35 fuel rail on B34 engine?
[QUOTE="fastpat"]The fuel in the rail is regulated, the fuel prior to the fuel pressure regulator is unregulated fuel. The Cold Start Valve (CSV) needs regulated fuel for proper function.
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
i kind of think his idea would be fine. the pressure is the same in the supply line, as the fuel rail. the regulator regulates the backpressure out of the return line, not the pressure into the rail.
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
i kind of think his idea would be fine. the pressure is the same in the supply line, as the fuel rail. the regulator regulates the backpressure out of the return line, not the pressure into the rail.
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Velocewest
- Posts: 1558
- Joined: Feb 12, 2006 12:00 PM
- Location: UK
[QUOTE="fastpat"]The fuel in the rail is regulated, the fuel prior to the fuel pressure regulator is unregulated fuel. The Cold Start Valve (CSV) needs regulated fuel for proper function.
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. You could run the CSV from a splitter off the supply line. As others have mentioned, if this is Motronic 1.1, no CSV needed, right?
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. You could run the CSV from a splitter off the supply line. As others have mentioned, if this is Motronic 1.1, no CSV needed, right?
[QUOTE="5er Quest"]I'm really stupid, I know- but I honestly did not think that the B35 even HAD a CSV. I'm looking at that M5 with the M30 engine and a B35 head. There aint no CSV to be had.
[/QUOTE]
A full on Motronics 1.3 system does not use a CSV, it is sensitive enough and fast enough to accomplish the same thing with the standard injectors only.
The original question was posed as if he's using a CSV, so that's how I couched my answer.
[/QUOTE]A full on Motronics 1.3 system does not use a CSV, it is sensitive enough and fast enough to accomplish the same thing with the standard injectors only.
The original question was posed as if he's using a CSV, so that's how I couched my answer.
[QUOTE="fastpat"]The fuel in the rail is regulated, the fuel prior to the fuel pressure regulator is unregulated fuel. The Cold Start Valve (CSV) needs regulated fuel for proper function.
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
[QUOTE="Velocewest"]Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. You could run the CSV from a splitter off the supply line. As others have mentioned, if this is Motronic 1.1, no CSV needed, right?[/QUOTE]
Well, now after having examined no less than four engines; I've seen that there are differences in one and the other three.
The two B35 engines and the single B34 engine I have all have the return line leaving the back end of the fuel rail.
The single M20B25 engine I have with Motronics 1.3 does not have a return line from the fuel rail, it comes out of the FPR itself, which is what I was thinking of when I posted earlier, just having worked on it today.:@ Now, I'm curious as to which method is better, any thoughts?
So, where does that leave us?
Maybe he could use the FPR with the return line built into it, and use the fitting for the return line from the fuel rail for his CSV.
You could braze a fitting to the fuel rail, but only after it's been steam cleaned of fuel.[/QUOTE]
[QUOTE="Velocewest"]Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. You could run the CSV from a splitter off the supply line. As others have mentioned, if this is Motronic 1.1, no CSV needed, right?[/QUOTE]
Well, now after having examined no less than four engines; I've seen that there are differences in one and the other three.
The two B35 engines and the single B34 engine I have all have the return line leaving the back end of the fuel rail.
The single M20B25 engine I have with Motronics 1.3 does not have a return line from the fuel rail, it comes out of the FPR itself, which is what I was thinking of when I posted earlier, just having worked on it today.:@ Now, I'm curious as to which method is better, any thoughts?
So, where does that leave us?
Maybe he could use the FPR with the return line built into it, and use the fitting for the return line from the fuel rail for his CSV.
[QUOTE="fastpat"]The fuel in the rail is regulated, the fuel prior to the fuel pressure regulator is unregulated fuel. The Cold Start Valve (CSV) needs regulated fuel for proper function.[/QUOTE]
[QUOTE="chrism"]the pressure is the same in the supply line, as the fuel rail. the regulator regulates the backpressure out of the return line, not the pressure into the rail.[/QUOTE]
[QUOTE="Velocewest"]Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. [/QUOTE]
[QUOTE="fastpat"]Well, now after having examined no less than four engines; I've seen that there are differences in one and the other three.
The two B35 engines and the single B34 engine I have all have the return line leaving the back end of the fuel rail.
The single M20B25 engine I have with Motronics 1.3 does not have a return line from the fuel rail, it comes out of the FPR itself, which is what I was thinking of when I posted earlier, just having worked on it today.:@ Now, I'm curious as to which method is better, any thoughts?
So, where does that leave us?
Maybe he could use the FPR with the return line built into it, and use the fitting for the return line from the fuel rail for his CSV. [/QUOTE]
Pat,
Chris M. and Velocewest are are correct on this. The fuel flows from the pump, through the supply line, into the back of the rail near the firewall, and either departs via the injectors or the FPR at the front of the fuel rail near the thermostat housing, and back to the tank via the return line. The FPR functions by changing restriction of flow from the fuel rail, not into the fuel rail. Thus, all of the fuel from the pump outlet, through the supply lines and the fuel rail, all the way to the FPR is at the same pressure (not considering the fluid dynamics factor, of course); the return line is at essentially zero pressure.
Also consider that rising-rate FPRs such as the Cartech FMU install in the return line after the stock FPR and increase fuel pressure by further restricting the outflow from the fuel rail.
As a test to convince yourself that it indeed works this way, you can do what I do when I de-fuel before an autocross (I like to run with about 1/3 tank): remove the fuel line coming out of the FPR, attach a length of line to the now-unoccupied fitting on the FPR and run the other end to a gas can. Turn on the ignition or jump the fuel pump relay. You'll have fuel flowing out of the FPR and into the gas can. The only way for this to be possible is for the system to work as Chris M., Velocewest, and I have described.
Thus, getting get back to Rich's original question -- yes, you can tee into the supply line and run that line to the CSV.
[Edit by Shawn D. on [TIME]1108735938[/TIME]]
[QUOTE="chrism"]the pressure is the same in the supply line, as the fuel rail. the regulator regulates the backpressure out of the return line, not the pressure into the rail.[/QUOTE]
[QUOTE="Velocewest"]Pat, I think it's the other way. fuel enters the rail at one end, and departs either through an injector or the FPR. [/QUOTE]
[QUOTE="fastpat"]Well, now after having examined no less than four engines; I've seen that there are differences in one and the other three.
The two B35 engines and the single B34 engine I have all have the return line leaving the back end of the fuel rail.
The single M20B25 engine I have with Motronics 1.3 does not have a return line from the fuel rail, it comes out of the FPR itself, which is what I was thinking of when I posted earlier, just having worked on it today.:@ Now, I'm curious as to which method is better, any thoughts?
So, where does that leave us?
Maybe he could use the FPR with the return line built into it, and use the fitting for the return line from the fuel rail for his CSV. [/QUOTE]
Pat,
Chris M. and Velocewest are are correct on this. The fuel flows from the pump, through the supply line, into the back of the rail near the firewall, and either departs via the injectors or the FPR at the front of the fuel rail near the thermostat housing, and back to the tank via the return line. The FPR functions by changing restriction of flow from the fuel rail, not into the fuel rail. Thus, all of the fuel from the pump outlet, through the supply lines and the fuel rail, all the way to the FPR is at the same pressure (not considering the fluid dynamics factor, of course); the return line is at essentially zero pressure.
Also consider that rising-rate FPRs such as the Cartech FMU install in the return line after the stock FPR and increase fuel pressure by further restricting the outflow from the fuel rail.
As a test to convince yourself that it indeed works this way, you can do what I do when I de-fuel before an autocross (I like to run with about 1/3 tank): remove the fuel line coming out of the FPR, attach a length of line to the now-unoccupied fitting on the FPR and run the other end to a gas can. Turn on the ignition or jump the fuel pump relay. You'll have fuel flowing out of the FPR and into the gas can. The only way for this to be possible is for the system to work as Chris M., Velocewest, and I have described.
Thus, getting get back to Rich's original question -- yes, you can tee into the supply line and run that line to the CSV.
[Edit by Shawn D. on [TIME]1108735938[/TIME]]
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Rich in WI
- Posts: 1115
- Joined: Feb 12, 2006 12:00 PM
Thanks Shawn. I didn't think we'd get into the issue of fuel flow, but it's good that we had the discussion. The main difference I see with the "T" fitting is that fuel pressure at the CSV would no longer necessarily be the same as the fuel rail pressure. But since fuel rail pressure would still be maintained by the FPR, I'm guessing that the downstream effect would still impact the CSV. I think that to ensure minimal differences between the CSV and the fuel rail I should have as short a distance from the "T" to the CSV.
And to clear up a point of confusion - I have a B35 intake, but it will have a CSV. I'm going to tap the screw holes. There's already an opening that fits the CSV. It has some sort of vacuum line coming out of it now. In normal operations, the B35 system does not need a CSV. This would be covered under Motronics 1.1 or 1.3. I'm sticking with 1.0 for now, so the CSV is quite necessary.
Thanks for the help,
Rich
And to clear up a point of confusion - I have a B35 intake, but it will have a CSV. I'm going to tap the screw holes. There's already an opening that fits the CSV. It has some sort of vacuum line coming out of it now. In normal operations, the B35 system does not need a CSV. This would be covered under Motronics 1.1 or 1.3. I'm sticking with 1.0 for now, so the CSV is quite necessary.
Thanks for the help,
Rich
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FirstFives Dictator
- Posts: 849
- Joined: Feb 12, 2006 12:00 PM
- Location: Virginia Beach, VA
- Contact:
[QUOTE="Rich in WI"]Thanks Shawn. I didn't think we'd get into the issue of fuel flow, but it's good that we had the discussion. The main difference I see with the "T" fitting is that fuel pressure at the CSV would no longer necessarily be the same as the fuel rail pressure. But since fuel rail pressure would still be maintained by the FPR, I'm guessing that the downstream effect would still impact the CSV. I think that to ensure minimal differences between the CSV and the fuel rail I should have as short a distance from the "T" to the CSV.[/QUOTE]
The supply hose and rail is virtually at the same pressure - I wouldn't sweat any minute differences for the cold start valve
I probably will be figuring out how to braze a fitting on the a rail also, as I'm trying to fit 533i rail into my US e12 ('Repo Car'). The CSV fitting is not in a convenient direction for the old e12 manifold. I'll probably use refrigerant silver solder as it's good for high pressure and sticks to darn near anything.
Still needs to be clean though
The supply hose and rail is virtually at the same pressure - I wouldn't sweat any minute differences for the cold start valve
I probably will be figuring out how to braze a fitting on the a rail also, as I'm trying to fit 533i rail into my US e12 ('Repo Car'). The CSV fitting is not in a convenient direction for the old e12 manifold. I'll probably use refrigerant silver solder as it's good for high pressure and sticks to darn near anything.
Still needs to be clean though
[QUOTE="Shawn D."]Pat,
Chris M. and Velocewest are are correct on this. The fuel flows from the pump, through the supply line, into the back of the rail near the firewall, and either departs via the injectors or the FPR at the front of the fuel rail near the thermostat housing, and back to the tank via the return line. The FPR functions by changing restriction of flow from the fuel rail, not into the fuel rail. Thus, all of the fuel from the pump outlet, through the supply lines and the fuel rail, all the way to the FPR is at the same pressure (not considering the fluid dynamics factor, of course); the return line is at essentially zero pressure.
Also consider that rising-rate FPRs such as the Cartech FMU install in the return line after the stock FPR and increase fuel pressure by further restricting the outflow from the fuel rail.
As a test to convince yourself that it indeed works this way, you can do what I do when I de-fuel before an autocross (I like to run with about 1/3 tank): remove the fuel line coming out of the FPR, attach a length of line to the now-unoccupied fitting on the FPR and run the other end to a gas can. Turn on the ignition or jump the fuel pump relay. You'll have fuel flowing out of the FPR and into the gas can. The only way for this to be possible is for the system to work as Chris M., Velocewest, and I have described.
Thus, getting get back to Rich's original question -- yes, you can tee into the supply line and run that line to the CSV.
[Edit by Shawn D. on [TIME]1108735938[/TIME]][/QUOTE]
Arrrgh, I hate it when I have it backwards (no double entendre intended). ~0
Thanks for clearly this up for me and the rest.
Chris M. and Velocewest are are correct on this. The fuel flows from the pump, through the supply line, into the back of the rail near the firewall, and either departs via the injectors or the FPR at the front of the fuel rail near the thermostat housing, and back to the tank via the return line. The FPR functions by changing restriction of flow from the fuel rail, not into the fuel rail. Thus, all of the fuel from the pump outlet, through the supply lines and the fuel rail, all the way to the FPR is at the same pressure (not considering the fluid dynamics factor, of course); the return line is at essentially zero pressure.
Also consider that rising-rate FPRs such as the Cartech FMU install in the return line after the stock FPR and increase fuel pressure by further restricting the outflow from the fuel rail.
As a test to convince yourself that it indeed works this way, you can do what I do when I de-fuel before an autocross (I like to run with about 1/3 tank): remove the fuel line coming out of the FPR, attach a length of line to the now-unoccupied fitting on the FPR and run the other end to a gas can. Turn on the ignition or jump the fuel pump relay. You'll have fuel flowing out of the FPR and into the gas can. The only way for this to be possible is for the system to work as Chris M., Velocewest, and I have described.
Thus, getting get back to Rich's original question -- yes, you can tee into the supply line and run that line to the CSV.
[Edit by Shawn D. on [TIME]1108735938[/TIME]][/QUOTE]
Arrrgh, I hate it when I have it backwards (no double entendre intended). ~0
Thanks for clearly this up for me and the rest.