# Fuel Pressure Regulator



## 0341TODD (Nov 15, 2003)

If I use an aftermarket fuel pressure regulator is there a problem with finding something better for the fuel temp sensor to do besides nothing? Is it going to cause a problem with the ecu? Can I simply unplug it and use a resistor and loop it? Can someone who actually has experience with changing it write me back Please?



Todd


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## Spongerider (Nov 18, 2002)

0341TODD said:


> If I use an aftermarket fuel pressure regulator is there a problem with finding something better for the fuel temp sensor to do besides nothing? Is it going to cause a problem with the ecu? Can I simply unplug it and use a resistor and loop it? Can someone who actually has experience with changing it write me back Please?
> Todd


Do you have a fuel pressure gauge? And why do you want one? I'm not flaming. I ask because you don't seem to know what FPR is used for because of the questions you are asking. 

But to answer your questions, no, it could so yes, please answer my questions first?


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## 0341TODD (Nov 15, 2003)

B/c Sponge, I am running more boost now and I was also going to replace the fuel pump as well. Wouldnt it help me to run like 5 or so more pounds of pressure through the fuel line or no? That is why Im asking dude, b/c I dont know if it is kinda pointless or if I should do it since Im running more boost. If I do need to do it then can I bypass the fuel temp sensor or do I even need to do that or can I ? Of course I have a pressure gauge, thats one of the first things I put on. I have like three laying around the shop and when I first got the car I hooked it up b/c I knew I would be modding the car and it was quicker then hooking up and actual tester.


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## Zen31ZR (Mar 24, 2004)

Yeah I'm wondering about this myself. I would like to delete the fuel temp sensor. I suppose the easiest way to do this is to add a resistor to make it beleive fuel temperature is always 30 degrees or so , Kinda like some guys do with IAT sensors. I have read in the manual that if the fuel temperature goes past a certain point the sensor will cause the ECU to run richer. Not really sure why , since warm fuel atomizes much more easily.


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## Spongerider (Nov 18, 2002)

[email protected] said:


> Yeah I'm wondering about this myself. I would like to delete the fuel temp sensor. I suppose the easiest way to do this is to add a resistor to make it beleive fuel temperature is always 30 degrees or so , Kinda like some guys do with IAT sensors. I have read in the manual that if the fuel temperature goes past a certain point the sensor will cause the ECU to run richer. Not really sure why , since warm fuel atomizes much more easily.


This is how see a a FPR, it is like a band aid of sort. An example, say you have 550cc injectors but your setup (MODS) is good for 590+rwhp. People will install FPR to make the 550cc injectors work like 600cc (Not scientific but you get the point?) If you do it the right way you would upgrade the injectors to 740cc so you don't have to worry about adding a FPR let alone if one fails while your at WOT.

Most people that use them can not get a hold of the right cc injector so they get the FPR to compensate. 

So you can do it the right way (above) or if you want to save on some money get the FPR.

I'm a Z32 guy and we do not delete the fuel temp sensor because it will affect the engine performance. Think about what you said above?



> "I have read in the manual that if the fuel temperature goes past a certain point the sensor will cause the ECU to run richer. Not really sure why , since warm fuel atomizes much more easily."


That is because heat will detonate your engine. If your surrounding enviroment is hot the fuel will get hot as well. That temp sensor tells the injector to run richer so you do detonate. Do you get? It's there for a very good reason.

Also what size injectors (cc) are you running? 

Here is a link on what they do.
http://www.capa.com.au/fuel_regulators.htm


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## Spongerider (Nov 18, 2002)

0341TODD said:


> B/c Sponge, I am running more boost now and I was also going to replace the fuel pump as well. Wouldnt it help me to run like 5 or so more pounds of pressure through the fuel line or no? That is why Im asking dude, b/c I dont know if it is kinda pointless or if I should do it since Im running more boost. If I do need to do it then can I bypass the fuel temp sensor or do I even need to do that or can I ? Of course I have a pressure gauge, thats one of the first things I put on. I have like three laying around the shop and when I first got the car I hooked it up b/c I knew I would be modding the car and it was quicker then hooking up and actual tester.


You only need it if your injectors and turbos need it? How do you know you need a FPR? Did you put it on the dyno or does your current mods demand it? Could you list you mods with injector size?

I would not touch your FTS.

Please read my above post to [email protected] and it was really ment for you.


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## Zen31ZR (Mar 24, 2004)

Spongerider said:


> This is how see a a FPR, it is like a band aid of sort. An example, say you have 550cc injectors but your setup (MODS) is good for 590+rwhp. People will install FPR to make the 550cc injectors work like 600cc (Not scientific but you get the point?) If you do it the right way you would upgrade the injectors to 740cc so you don't have to worry about adding a FPR let alone if one fails while your at WOT.
> 
> Most people that use them can not get a hold of the right cc injector so they get the FPR to compensate.
> 
> ...


I'm not gonna argue with you , but suffice it to say it doesn't make much sense. I spent several years in the hot rod community before I turned to imports , and fuel temperature was one of the least things we worried about. Hot fuel atomizes much more readily , and is more desirable than cold fuel for that reason. Also , all fuel injected cars have an FPR , so I don't understand you saying one is not desirable? Ever heard of FPR overrun? That's what happens when you have too much fuel pressure and volume and not enough recirculation capacity , it causes the injectors to run much richer than they are supposed to. A higher capacity FPR is an absolute necessity for high powered sports cars. I've also seen FPR failures spike fuel pressure to very high levels , depending on how it fails. And I don't see how keeping an undesirable temperature sensor can hurt performance , instead it would HELP , because the engine would not be forced to run richer than it is supposed to. Fuel temperature often has nothing to do with engine temperature. Given where the fuel lines go under the vehicle , the inclusion of even a 3" exhaust and a large cat can heat up the fuel lines and the fuel inside.


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## Spongerider (Nov 18, 2002)

[email protected] said:


> I'm not gonna argue with you , but suffice it to say it doesn't make much sense. I spent several years in the hot rod community before I turned to imports , and fuel temperature was one of the least things we worried about. Hot fuel atomizes much more readily , and is more desirable than cold fuel for that reason. Also , all fuel injected cars have an FPR , so I don't understand you saying one is not desirable? Ever heard of FPR overrun? That's what happens when you have too much fuel pressure and volume and not enough recirculation capacity , it causes the injectors to run much richer than they are supposed to. A higher capacity FPR is an absolute necessity for high powered sports cars. I've also seen FPR failures spike fuel pressure to very high levels , depending on how it fails. And I don't see how keeping an undesirable temperature sensor can hurt performance , instead it would HELP , because the engine would not be forced to run richer than it is supposed to. Fuel temperature often has nothing to do with engine temperature. Given where the fuel lines go under the vehicle , the inclusion of even a 3" exhaust and a large cat can heat up the fuel lines and the fuel inside.


Hold on, I hope I did not come off as arguing or flaming you? I just gave you my opion.


[email protected] said:


> "I'm not gonna argue with you , but suffice it to say it doesn't make much sense. I spent several years in the hot rod community before I turned to imports , and fuel temperature was one of the least things we worried about. Hot fuel atomizes much more readily , and is more desirable than cold fuel for that reason."


I know that but there is a reason for a FTS sure you would like cool fuel going into the engine but all your doing is tricking the ECU and hot fuel is being delivered right? Unless your running a standalone and you car is tuned for that "trick" it is not wise to run any setup that way. Even Mike Kojima would agree and why he doesn't run that setup in any of his cars.



[email protected] said:


> "Also , all fuel injected cars have an FPR , so I don't understand you saying one is not desirable?"


I think now I understand what you were say, I *thought* you were talking about a *Adjustable FPR* and I'm sorry, please disregaurd whta I said in the above posts. :dumbass: 



[email protected] said:


> "Fuel temperature often has nothing to do with engine temperature. Given where the fuel lines go under the vehicle , the inclusion of even a 3" exhaust and a large cat can heat up the fuel lines and the fuel inside."


Remember the cause of detonation is not enough fuel or/ and too much heat. 

And why there is a relationship between engine and fuel. If the engine is hot the fuel has to run through the engine, right. The unused fuel is put back in the tank thus heating the gas. The hotter the engine gets the hotter the fuel. The Fuel pump and outside temps also affect the gas but not as much as the engine temps. 

Outside weather does effect engine temps much more then fuel so when the weather is hot the engine runs hotter which makes the fuel run hotter. Do you understand my logic?


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## Zen31ZR (Mar 24, 2004)

All discussion of the FPR aside , I'd like to know the basis for cold fuel being required. Cold fuel will not cool off a hot engine , in fact it is the mechanics involved in evaporation which provide the cooling , and warm/hot fuel evaporates much more readily than cold fuel does. Depends on the formulation of the fuel , of course , but lets say for the sake of argument I am talking about summer fuels , which are formulated to not evaporate as quickly as say , winter fuels are. It's much the same as whether you use warm or cold water in your Aquamist sytem , it honestly doesn't matter , it's the thermal reaction in the evaporation which cools the intake air. a 10 or 20 degree difference in water temperature is not going to make one iota of difference in a 230+ degree environment , such as our non-intercooled intakes would have , especially on a 80 degree day. You follow my logic so far? 
I would perhaps understand the inclusion of a fuel temperature sensor from an engineers point of view , his job is also to protect the manufacturers warranty which will be on that car , and running the engine a bit richer makes sure there are no burnt pistons.  But on an 18 year old turbo car long out of warranty , it would seem to be a useless affectation.


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## 0341TODD (Nov 15, 2003)

Yeah, what he said-LOL

Hey sponge, I was talking about adding a adjustable fpr when I do a fuel pump. Mike had told me that a walboro 255 would work just fine or I could use the Z32 pump. The only mods I have are exhaust and intake and 10-11 psi. Thats it. I was just thinking that "Hey, if Im going to upgrade the pump, why not do the fuel pressure regulator too and find out if I should just get a stock unit or an adjustable one like the nismo one- its like 40 dollars more". 

That aside...........I thought having cooler fuel was always better performance wise anyways? Isnt that why all the guys with 70 chevelles run those crazy insulated fuel coil canisters that they shove with ice before they go racing?


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## silvernismo (Jun 27, 2004)

what is the base fp on an 89 maxima? i have a bad fuel pump and am buying a walboro 255 and need to know if it is to much without an afpr


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## Zen31ZR (Mar 24, 2004)

0341TODD said:


> That aside...........I thought having cooler fuel was always better performance wise anyways? Isnt that why all the guys with 70 chevelles run those crazy insulated fuel coil canisters that they shove with ice before they go racing?


 I've never seen that , they don't use anything like that here. Certainly not in any of the 9 second cars I've seen at Bandimere. Too much weight , for one.


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## 0341TODD (Nov 15, 2003)

its kinda like a styrofoam can that they fill with ice dude. Ive seen it on a few cars. It only wieghs maybe like 1 pound- but youre supposed to get like 80 hp out of it!!! (yeah Im joking about that) DID YOU GET THAT LETTER YET?


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## 0341TODD (Nov 15, 2003)

Not to be a dick due, but the guys in the maxima forum will probably know better then us. Maybe like 34 psi or something- that is such a shot in the dark though- its different for the turbo 3.0 and the NA. That is why there is the "Maxima" part of the fourms though


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## morepower2 (Apr 19, 2002)

0341TODD said:


> If I use an aftermarket fuel pressure regulator is there a problem with finding something better for the fuel temp sensor to do besides nothing? Is it going to cause a problem with the ecu? Can I simply unplug it and use a resistor and loop it? Can someone who actually has experience with changing it write me back Please?
> 
> 
> 
> Todd


The fuel temp sensor is there to help prevent vapor lock. At a certain temperture the ECU turns on a solenoid to the vacume line to increse the fuel pressure and the boiling point of the fuel. At the same time the ECU goes to a different program to lean the mixture to compensate for the higher fuel pressure. This only happens on hot restart.

If you take the temp sensor and the solenoid out, then the car will run slightly lean for a few minutes after a hot restart. Usualy you will just see some minor drivabilty issues for a few minutes after a hot restart. If you hit boost, the ECU will turn this lean condition off so it's not dangerous.

Mike


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## Zen31ZR (Mar 24, 2004)

morepower2 said:


> The fuel temp sensor is there to help prevent vapor lock. At a certain temperture the ECU turns on a solenoid to the vacume line to increse the fuel pressure and the boiling point of the fuel. At the same time the ECU goes to a different program to lean the mixture to compensate for the higher fuel pressure. This only happens on hot restart.
> 
> If you take the temp sensor and the solenoid out, then the car will run slightly lean for a few minutes after a hot restart. Usualy you will just see some minor drivabilty issues for a few minutes after a hot restart. If you hit boost, the ECU will turn this lean condition off so it's not dangerous.
> 
> Mike


Apparently mines not working anyway. Still vapor-locks on 80+ degree days.


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## 0341TODD (Nov 15, 2003)

ditto- maybe that is the source of why I have to hold my throttle partially open to start the car when its hot.......I still havent checked the IAC valve.


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