Aeromotive FPR position

[Grant Monkhouse]

i currently putting together my fuel system for my Rx4, and was wondering if i can put the FPR in the boot with the rest of the fuel system instead of in the engine bay where it normally goes?
 
Basically my system is going to run like this;
 
From the fuel tank out of 2 AN6 bulkhead fittings to my pick up up pump, from the pick up pump to the swirl pot,
swirl pot to fuel filter
fuel filter to bosch 044,
down fuel line (under the car) to fuel rails (primary and secondary)
back down the car to the FPR in the boot
then from the return outlet on the bottom of the FPR  back to the swirl pot, and then then there is a return on the swirl pot back to the tank.
 
Anyone confused:3Confused by that or do you understand and think i can run the FPR in the boot?

[turbotoaster]

the issue you have is that a fpr works by boost pressure/vacuum, the closer it is the engine, the faster it recieves info on what the engine is doing.

Now if its in the boot when your on/off the throttle, you have to wait for the desired boost pressure to reach the fpr, then you have to wait for the fpr to react then the fuel lines to pressurise.

in my opinion, putting the fpr in the boot will double the amount of time to change the fuel pressure, then again double the amount of time for the fpr to recieve its boost pressure.


Overall i wouldnt recommend it at all, you want it as close to the outlet of the fuel rail and vacuum source as possible.

This is all my thoughts but it is backed up by common sense

[Mir]

I agree with the above!

Mir

[Grant Monkhouse]

That\'s what I was thinking but was just wondering if it would work in the boot. Mounting it in the engine is no problem at all, makes me deciding on which an6 fittings I need to get as iv just about bought all of them I need now. Just an6 to 5/16 hard line adapters and a couple more then I\'m done. Apart from the hard line and braided line for in the boot.

[SiH]

Make sure you use the right hard line fittings. Too many people use the flareless sleeves that are only rated to about 50PSI or so. With a stock ~38PSI base pressure most people will easily pass that.

[Grant Monkhouse]

these are the fittings i am hopefully going to use into and out of the FPR to the hard lines from the fuel rails to the FPR and also from the bulkhead fittings through my boot floor to the hard lines underneath the car.
 
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=170648823448&category=72205&_trksid=p5197.c0.m619
 
i am going to be using braided fuel lines in my boot, connected together mainly using these fittings

[12at]

Fuel pressure regs are usually on the return so kinda pointless in the rear.. Mount it off the fire wall and that should sort it

[AtomicRex]

the issue you have is that a fpr works by boost pressure/vacuum, the closer it is the engine, the faster it recieves info on what the engine is doing.
 
Now if its in the boot when your on/off the throttle, you have to wait for the desired boost pressure to reach the fpr, then you have to wait for the fpr to react then the fuel lines to pressurise.
 
in my opinion, putting the fpr in the boot will double the amount of time to change the fuel pressure, then again double the amount of time for the fpr to recieve its boost pressure.
 
 
Overall i wouldnt recommend it at all, you want it as close to the outlet of the fuel rail and vacuum source as possible.
 
This is all my thoughts but it is backed up by common sense

Lee
 
Where are getting this info from?
 
The pressure in the line is going to change exceptionally fast!  You are talking an03 lines, so cross sectional area is so tiny it would be pretty much instantaneous.  Think next time you press the brake pedal?  You kind of hope that is instant, and air is just as much a fluid as the sticky stuff you put in the brake lines.
 
The problem however is the pressure loss.  The fuel system in our car was going to be returnless and run the FPR at the rear, this would minimise the fuel lines and therefore weight, and also prevent heat circulation.
 
You need to make sure you run a braided line, otherwise there are too many opportunities to get a kink in the silicon hose.  But as said, we\'ve moved back to the conventional system as it would mean contending with the pressure loss.

[Prof]

I think Lee was talking about the vacuum line going to the FPR in the back - that\'s a long length of hose - and air DOES compress - that\'s exactly what you do in a turbo - so there would be a hell of a delay between front and back of the car.
 
To use your brake analogy - that\'s why you bleed breaks - because the fluid is good at transmitting the pressure pulse, and air in the lines isn\'t !!
 
I\'d stick with the FPR up front.

[turbotoaster]

I think Lee was talking about the vacuum line going to the FPR in the back - that\'s a long length of hose - and air DOES compress - that\'s exactly what you do in a turbo - so there would be a hell of a delay between front and back of the car.
 
To use your brake analogy - that\'s why you bleed breaks - because the fluid is good at transmitting the pressure pulse, and air in the lines isn\'t !!
 
I\'d stick with the FPR up front.

pretty much what i meant.

Running a vaccum line to the boot can delay the fpr working, as above, air compresses and it only takes a miniscule delay to put it fuel pressure one map point behind where it should be, yes you can componsate on the map for it, but why should you have to?

also its its a rubber/silicone vaccum pipe, they expand aswell, which again slows the process down.

i would run the fpr as close to the injectors/vaccum source as possible as i want the fuel pressure to match vaccum/boost as close as i can, anything else is folly.

Again, you bleed your brakes to get the air out, as liquid doesnt compress well.

it theory everything should be braided/solid lines with AN fittings but it costs a fortune to do so hence alot of people use silicone hose and shorten lines to minimise losses/delay

also jon, where are my pics....your keeping mrc waiting :spank

[m1tch]

I will be running braided lines, aeroquip fittings with my Aeromotive FPR, its fueling and also the reason why I will be running a fire system lol

[AtomicRex]

Pics are on their way.....in the process of moving!
 
I think the emphasis on the speed of the vacuum is negligible you are only looking at fractions of a second, which I will agree does come into play when you consider the injector opening times are also fractions of a second, but this all does depend on the type of line you use.
 
Car manufactures started to run the return less systems so as to improve the vapour loss from the tank, this was due to the warmer fuel coming back from the lines.
 
It turns out that they have had to run big compensations due to the fact that the heat sits in the fuel rail, and actually causes the fuel to run hotter.....much to what I was led to believe by ATL when we first discussed this.  Certainly in standing traffic they have had to build in compensation maps to improve throttle response and also increase the fuel pressure dramatically to avoid the fuel from boiling.
 
Aeromotive dont recommend using returnless systems.
 
Sorry about the analogy of the brake fluid....Im knackered....and clearly having a funny 5 minutes!  Yes brake fluid is an incompressible fluid.....and air probably isnt!  I would go to explain further, but feel the hole Ive dug thus far is probably big enough!

[Grant Monkhouse]

For the people that don\'t use proper AN fittings, you are cheap and aren\'t doing things properly. Get your money out and do it right, cheapskates.

[Grant Monkhouse]

So what happens if you use a hard line for the vac line instead of a braided line? The time between response would be reduced?

[turbotoaster]

For the people that don\'t use proper AN fittings, you are cheap and aren\'t doing things properly. Get your money out and do it right, cheapskates.

haha grant you have never met me, im the tightest bloke you have ever met, I was actually contemplating running my car on 100% meth as it works out cheaper than pump fuel per rpm to hit the same afr!!

Flames would be nice to, dont think trackday organisers would be to impressed!

Im trying to avoid anything AN related at the moment to keep the costs down so i can spend it on other areas of the car to get it finished quicker.

So what happens if you use a hard line for the vac line instead of a braided line? The time between response would be reduced?

you wouldnt expect proper braided line to expand under pressure anyway so the change between them would be minimal, the issue is the distance of the line itself.

maybe a good analogy for this would the difference between a very small v mount cooler and a massive front mount cooler.

when at full throttle, due to there being more internal area from longer pipes/bigger cooler there is a delay in the full pressurised air entering the engine.

This is only minimal, but it is still there, normally this doesnt matter, but if you hit full boost and the fpr doesnt have chance to know what boost you are, close to ramp up the fuel pressure and in turn give you enough fuel your playing with fire a bit.


In an ideal world you could have the fuel pump next to the fuel rail one side and the fpr the other, this would minimise time differential and pressure losses from fuel and air.........but thats a bit over the top for 99.9999% of engines out there