RRFPR vs. high flow injectors: what to buy??

MMamdouh · Post by **MMamdouh** » Sun Jun 11, 2006 5:09 pm

hi guys... you all know the 2.0 nubira is now turboed and runnung @ 8 PSI but still needs tuning as far as fuel managment is concerned.

the question here is what to get: RRFPR or high flow injectors?

we though of getting the RRFPR with the stock injectors but some people said that won't be enough... the injectors had to be upgraded as well to handle the extra pressure of the RRFPR. (is that 100% accurate BTW?)

now looking at the issue from the other side arround, we can get high flow injectors from a 3.0L engine or so to replace the OEM injector but will those be enough to handle the turbo demands at the 42 psi stock fuel pressure? what about off boost behavoiur? will it be too rich with those injectors?

if having BOTH is a must then what should we get first the RRFPR or injectors as far as safeguarding the engine is concerned? the injectors are going to cost as much as the RRFPR and the current finance is enough for only one thing for the time beeing so what should we hunt for first?

more info on the turbo/engine setup is in this post:
http://www.daewootech.com/forum/viewtopic.php?t=6536

thanks in advance for your help.

MMamdouh

Nubira2.2 · Post by **Nubira2.2** » Sun Jun 11, 2006 6:29 pm

i would say get first the RRFPR

if you get bigger injectors you will need something to tune them like a piggyback

otherwise you will have a ruff idle and may run too rich

with bigger and correctly sized injectors is not necesary a RRFPR because the flow rate of those injectors is messured @ 43.5 psi

thats more or less the amount our stock pressure regulators do

GsiTurbo · Post by **GsiTurbo** » Sun Jun 11, 2006 7:56 pm

Ideally, you want 1:1 raising rate fuel pressure regulator, boost dependant. This way, when motor creates vacuum it will work just like stock unit (1.7:1). However, when it detects boost, it will increase fuel pressure by 1psi per 1 pound of boost. This is example of good regulator: 8071835612 (eBay item number)

Using injectors from a larger displacement motor does not always mean they are higher rate. What you want to do is calculate what is the flow requirement for the injectors at given boost level. Then find out what is the operating fuel pressure of injectors you plan to use, and the new fuel pressure. You can go here: http://users.erols.com/srweiss/tableifc.htm if you know the part number.

To calculate new flow of injector (with higher fuel pressure), go here: http://www.csgnetwork.com/fiflowcalc.html

To calculate required injector flow (and others, this is actually a very nice link), go here: http://www.witchhunter.com/injectorcalc1.htm

ubuyau · Post by **ubuyau** » Mon Jun 12, 2006 1:00 am

Get the RRFPR first. That way when the car is off boost it'll act just like it did without the turbo (same fuel economy - same mixture). When its on boost it'll bump the fuel pressure up 1psi for each 1 psi boost.

Do a dyno run or check the AFR - you should be running much safer AFR now.

Get the injectors second if you are still running lean. Remember though you will always run rich with bigger injectors if you dont tune them - right the way thru the rev range. It'll be safer but you'll have less power...

I had both (RRFPR and bigger injectors from a Nubira). Yes I ran rich but it was safe... I believe you should have both (from a safety perspective...)

--Tim

MMamdouh · Post by **MMamdouh** » Mon Jun 12, 2006 10:36 am

well... i did some calculations but i found out i don't know the flow rate of the OEM T20SED injectors so i used 19lb/hr (200 cc/min) as an estimate, does anyone know the correct flow rate of those injectors??

crank HP 200HP
Injectors 4
B.S.F.C 0.625 (estimate)
duty cycle 80%
OEM flow 19 lb/hr (estimate)

anyways according to my calculations i will be needing a 39 lb/hr (410 cc/min) fuel flow... getting injector to do the job (no RRFPR) will make the off boost handling far from optimum and fuel economy will slip to the oblivion.

if i depended only on the RRFPR to get that kind of flow i'd be running at 184 psi with stock injectors which is insane for sure so we got to get both upgrades.

with 1:1 RRFPR and 8 PSI of boost we will go up to 50~52 PSI of fuel pressure... that will require a 38 lb/hr injector which is not very much different than a 39 lb/hr one... i think off boost performance will suffer as well.

what do you think guys... did i do something wrong with the calculations or is this just the fact when it comes to fuel managment underr boost??

MMamdouh

kinkyllama · Post by **kinkyllama** » Mon Jun 12, 2006 6:01 pm

MMamdouh wrote: that will require a 38 lb/hr injector which is not very much different than a 39 lb/hr one... i think off boost performance will suffer as well.

what do you think guys... did i do something wrong with the calculations or is this just the fact when it comes to fuel managment underr boost??

MMamdouh

I think that 39lbs/hr is way overdone for 200hp. But if you did everything right and it really needs that high injectors It'd be a good idea to upgrade the fuel pump as well.