so if i were to disconnect the line that runs from the fpr on the fuel rail to the IM my fuel mixture would "fatten up"?

im having an argument with a buddy of mine about this and would like some clarity. TIA

 

I believe removing the vacuum line would make your car run lean. When the vacuum line is connected, fuel pressure is less because the regulator is opened more than when the vacuum hose is disconnected and the valve is closed more.

 

ok and the only way to "fatten up" the mixture is to have an adjustable fpr correct or no?

im having a lean mixture problem with my car and we are trying to figure out how to "throw a band aid at it" until i can get tuned.

 

Well, now that I think about it, fuel pressure is higher when the vacuum line is disconnected, so with higher FP you get more fuel sprayed when the injector opens up, and w/ a FPR higher pressure correlates to a richer mixture. And yes, a FPR would be only a band aid until you get a tune and larger injectors if you need them.

 

so your saying he is right, it will help out a little bit? even at WOT?

 

here is the mods list of the motor:
b18c1
blox v-stack and filter
3" intake arm
skunk2 IM
hondata IM gasket
CTR intake cam
hytech replica header
stock bottom end

so with those mods and running the motor on a virgin p30 ecu you should see my dilemma. as small a problem it may seem i am uncomfortable knowing it is running like this cause its also my dd. i dont want to have to spend money on a chipped ecu cause i am trying to save for the s300 and dyno time.


Modified by polishedturd at 2:01 PM 6/2/2008

 

I believe that line compensates for pressure changes in the intake. Think of the injector in terms of the transition from one pressurized system (fuel side) to another pressurized system (the intake plenum). That is, they are separate systems except for the connection via the injector. If you set the fuel pressure to a specific value - let's say 40 psi as an example - then it sprays a certain amount of fuel per second. However, the pressure on the other side of the injector is always changing. On a turbo car, it might go from a significant vacuum to 30+ psi of positive pressure. If the fuel side stays at 40 psi and the intake pressure rises to 30 psi, then your effective pressure (net) is only ten psi. That is, the injector would flow the same rate as if the fuel were set to 10 psi with no pressure on the down stream side. Make sense?

So, if the line goes from negative pressure to atmospheric (zero correction) it would raise your effective fuel rate. However, now it won't adjust/correct at all as the pressure changes - it will be lower when you transition from full vacuum to some value close to zero. So you may solve the problem at one throttle point, but you will probably make it worse at another.

 

well doesnt the old saying go: "its better to run alittle rich than alittle lean"?

i would be ok with it being alittle rich at all throttle points if thats the case. would this be a way to fool it into running rich all the time or would it (like you say) just be rich at idle?

 

NO. The FPR is regulated by vacume, when you figure out how this works, you will be beter educated.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">NO. The FPR is regulated by vacume, when you figure out how this works, you will be beter educated. </TD></TR></TABLE>
thanks DonF, well then should i be ok temporarily running on this ecu until i can get it tuned or what would you do in my shoes? it will help me sleep better at night coming from you(no joke).

 

morning bump
anybody?

 

in donF's shoes.. he would tune it.. the first day it started running...

id do the same too..

why? cuz it may run ok now.. and all.. without knowing that the condition of the motor is deteriorating

then, when the s300 comes, and the dyno tuning begins.. we all wonder.. why such a low whp?

HTH

 

well i drive pretty conservative and rarely take it over 4krpms(cause i know i need to tune it but dont have the money right now) so would i still be deteriorating the motor?

 

If your motor is running lean, then yes, that's bad for the motor.

 

so basicly im fuc[ked

 

An overly lean and or rich mixture could both be bad for your motor. It could be over a short or long period of time. With no way to monitor what your engine is doing internally you will never know.


Better safe than sorry,
I don't know a lot about your particular setup. It sounds like you had better put it all back to stock until you can afford to have it tuned. You should always budget a build starting with the tuning. Even though it's the last thing you do it's the most important. Make sure you set aside money for a dyno tune or two from the start.

 

well going back to stock is not an option right now but could something as simple as forking out the $150 for a chipped/street tuned ecu with a type r base map and a "fatter fuel mixture"(judging by my air/fuel gauge) be an "ok" option to get me by?

i know that i am sort of "painting with a broad brush" on this one but i really just want to be on the safe side for the sake of my dd without having to buy all the stock parts back and doing double work.

 

That would be a band aid solution but yes it is better than an open wound for sure.

Talk to the people that you will have tuning your car and see what they can do for ya. They may be able to hook you up with an ECU that will be good to go for there tuning setup for a reasonable price. Better to do that than just getting any old chipped ecu online.

 

crank up your FPR and call it a day until you tune it.

 

well thats who i was going to get the chip/street tune from is my tuner.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2LEM1 &raquo;</TD></TR><TR><TD CLASS="quote">crank up your FPR and call it a day until you tune it.</TD></TR></TABLE>
how would i do that without an adjustable fuel pressure regulator?

 

Get a B&M adjustable FPR and a good gauge, they're fairly cheap, about $100 or less.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by polishedturd &raquo;</TD></TR><TR><TD CLASS="quote">
how would i do that without an adjustable fuel pressure regulator?</TD></TR></TABLE>

Sorry, reading &gt; me

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all-mtr-teg &raquo;</TD></TR><TR><TD CLASS="quote">Get a B&M adjustable FPR and a good gauge, they're fairly cheap, about $100 or less.</TD></TR></TABLE>

^this

 

thats the thing, why pay the $100 for a fpr when i can get my tuner to burn me a chip(not some online chip but something fairly compatible with my setup) with a type r base map and fatter fuel table if need be plus i can choose my vtec engagement point and rev limiter.? i can monitor my air/fuel ratio with my autometer gauge pretty accurately cant i? i know its not spot on but its something. or am i totally wrong?

 

I've never used an Autometer gauge so I can't tell you if if they are reliable enough or if they are nothing more than a blinking Christmas tree ornament. From what I have read there not the most accurate device...

Yes, You would be better off spending the money on the ECU & base map. Talk to your tuner and see what he thinks. What people tell you on the internet shouldn't matter. If you have a tuner that you trust do what they tell you to do.