225 megane turbo injectors.. what FPR?

[ThrushMotorsport]

Hi guys, heres a debate for you.. on fueling with my turbo conversion.

Going to be running about 8-9 PSI on my turbo conversion, i have megane 225 turbo injectors for my build, they are 390CC injectors

At the moment, it has an adjustable FPR.. i want away with this as its a rising preasure one.. i was going to buy a 4 bar FPR off a cupra, but im wondering if this would be a bit overkill for the build for the injectors and power i am seeking?

Im going to be running standard cams, and internals, with a 1.9mm headgasket.

The power im wanting to acheive is anywhere from 200-225bhp at the wheels (will be forging the engine later on)

Ill be running a predator ECU

Would i be best with a VTR 3.5 bar one? or is the 4 bar one a much better all round option if its going to be getting mapped? as i dont want it overfueling and seeing det in the cylinders..

Ill also be using a walbro 255 pump.

thanks.

[ThrushMotorsport]

Comon guys, some of you must be running this setup

[jones91]

The 3.5bar vtr fpr with the megane 225 injectors will be ideal for around 225bhp at the wheels

[ryanmt]

3.5 bar would be fine but you could use a 4 bar if you wanted. Might just be a bit harder to get an idle with it.

[tweeqd]

i have 390cc marelli injectors and a 3bar FPR (connected to boost so rises to 4 bar )
im running 262bhp @ 1 bar on a T34 and injectors are about 80% at 7.5k

[K567]

id stay adjustable regulator with a fuel return setup on the vtr this is the best option to give the best turbo tuning.
what you have to look at is what the actual base pressure those injectors are set to run at, do they flow 390cc at 3bar, 3.5bar or 4bar
stay away from crappy rising rate regs, you want something decent like an aeromotive.....

but this is just my opinion....

[ThrushMotorsport]

K567 - the one i have on here is i think.. a cheap rising fuel reg, its on for the cam's that are on the engine im guessing, but i didnt do the work myself, so im unsure what make it is, it has no wording on it, but is defo a rising rate.

Not actually too sure what FPR the megane 225 use, i will research on it though a little more

Tweek/ Ryan / Jones - i dont want to go overkill with it, i might just go and grab a 3.5 bar one from the scrappys then if thats the usual choice on these size of injectors, as wasnt sure if 4 bar was overkill, and wouldnt really want a shit idle from it or slight overfueling

Tweek i take it your running a bar of boost then if yours rises up to 4 bar?

[tweeqd]

yes mate im running a vts FPR on an AX return fuel rail
im currently running 1 bar of boost and swapped my 4.5 bar reg for a 3 bar one as im going back for mapping at 2 bar and this would mean the pump would have to do 6.5 bar, my new pump will do that but its better for the pump if the power can be made at the lowest pressure you can

390 are good for 260 bhp with no problems, ive now upgraded to 630cc as im going to 2 bar

[ThrushMotorsport]

Hmm, saying that then, i may aswell just re-plumb back in the 3 bar FPR, as he did leave it connected to the fuel rail.. will save me a bit of spare cash to finally get the ECU ordered.

[Gareth_R]

it'll be more than 3.5bar by the time you're on boost anyway so 3 bar should be fine with those injectors and that BHP

[ThrushMotorsport]

Thanks guys, big help

[K567]

The biggest problem a lot of people come across with turbo tuning and injectors is they don't do the calculations for the engine, injector size, hp, air mass, flow and temps all of these numbers come into play. One of the biggest mistakes made is fuel, if you have injectors that are too big running too little or too high base pressure eg 660's at 3 bar but running 4 bar cos your mate said its best or vice versa rated at 4 bar and running at 3 bar, when it comes to tuning with a good FPR that you can adjust you half the time it takes to get it right, rather than having to fool it with the fuel map. Injectors at too low pressure when too big end up with poor spray patterns leading to fuel pooling, too small with too much pressure end up over worked, then having to add or pull too much fuel to make them work just makes the map harder to tune. It's all about getting the numbers right at the beginning.

[K567]

This is a good ref page to get an idea http://www.rceng.com/technical.aspx#...tor_Worksheet_

[K567]

So this calc shows that staying within Basic parameters you would need to run a static fuel pressure of 4 bar with 390's to get 225hp.

[axsaxoman]

lot of rubbish being talked about fuel pressure and effects on running
higher fuel pressure will ALWAYS give a better atomised fuel spray pattern + better running .
max pressure you can run std pump at is 4.5 bar --over that the flow rate will drop dramatically
pressure + flow are linked on all pumps, as pressure rises flow drops
as for using a rising reg to get round proper mapping --bollocks -- proper mapping is always required
the less number of variables the better -then when you look at the map you can make some sense of it .
personally I never connect the small pipe on fuel regs as that can make the fuel pressure rise to a point when the volume of pump drops --then you will get silly fuelling numbers

as for using big injectors and short injection times causing poor idle that could be caused by using an injector with a poor spray pattern for the shape of the inlet manifold /port or fuel pressure to low to give a good pattern at low injector duration times required by using a large injector with possibly a single hole pintel
some injectors have one pintel hole .some have 2 or 4 and some even have 12 .
also the spray angles differ on some , the spray pattern is not always straight and a single cone off set to point it better down centre of port
it has been proved in racing that using an injector with 12 holes of the same flow rate as a 4 hole unit that they give better power for less fuel consumption
On a dodge viper GT car it meant being able to go 3 more laps before refuelling was needed .
injectors are rated at 3bar of pressure ,but if buying from some sites be careful as i have noticed some listing them at higher pressures --use 3 bar as the guide line for comparing injector sizing .
when using on boosted cars you then must consider the actual pressure in the port --n/a car using 3 bar =3 bar of injection pressure
boosted car running 2bar of boost = 3 bar fuel pressure =1 bar of fuel pressure --not good --but you can why some may use a GOOD quality rising reg to keep fuel pressure in the port the same at any boost level .
but a good rising reg will cost alot of money ,this is why car makers use diferent reg pressures so the variation by the little pipe is a very small percentage and it is really not to rise the pressure but more to draw it off on overun when you have a big vacum in engine under certain conditions.
you will have noticed though that modern design engines do not use any vac on the fuel reg at all --they just map them better and can control the vac by altering the throttle opening with a the motorised body --that how they get idle control ,by moving the t/body relative to the map pressure signal .which is the main engine load sensor on modern cars ,
thats why the only correct way to map a boosted car is rpm /map pressure --not rpm /tps ,which will work fine with n/a high lift cam engines ,as the vacum /map signal is too irratic to be any use at idle and low rpm engine loads .
thats also why when you fit lumpy cams to std car it idles like crap ,because the std ecu uses vac/map signal to alter fuelling and that signal will be irratic due to high lift large valve overlap cams causing poor vac signal at low rpm s,
that also why you use ITB,S on high lift cams --not to get extra air ,you could do that by fitting larger single t/body
at low rpms when no1 cylinder is sucking in no4 will have the ex valve open allowing ex gas to go across the inlet manifold to no1 and the vac signal will drop and become unstable as well as a little ex gas will reduce the oxygen content being drawn into no1

this also why most modern cars will have VVT so that at idle they can have a very mild cam overlap ,which is good for idle and emissions and at higher rpms have more valve lift and overlap to make better power at the higher rpms all on a single t/body
we built an angine for an asian race series which specified single t/body only .using a 55mm t/body we made 190bhp --but it idled like shit at 1700rpm --not exactly a road car engine --but it proved the point that the reason for ITB is not for power but to give the engine a much wider usable power band --this engine did bugger-all till it hit 5k then pulled like stink to 8500rpm

[yr51ocw]

Originally Posted by axsaxoman

lot of rubbish being talked about fuel pressure and effects on running
higher fuel pressure will ALWAYS give a better atomised fuel spray pattern + better running .

wrong! a rise in fuel pressure will alter spray targeting, which if the target increases wall wetting then combustion stability and emissions will suffer

[Gareth_R]

running 2 bar of boost with a 3 bar fpr wouldnt result in 1 bar of fuel pressure. Pushing boost through my fpr raises the pressure (from 4 to 4.5 bar). Whether thats the case for all fpr's i dont know but mine is only a standard little one that fits into the fuel rail.

[axsaxoman]

If you have wall wetting to any great degree then your injector size and or its placement is incorrect or gas speed in port is too low or port is wrong shape .
considering that lifting pressure by 1 bar usually only makes 10-12% difference in flow rate of injector then the chance of wall wetting is minimal .
wall wetting is only usually going to cause running problems at low power outputs + idle .
the injector duration at low power /idle should be so small that this would never be a problem .
If its happening at high power outputs then maybe you need to 0cnsider plaement of injector to allow enough time for the amount of fuel you are injecting to get fully atomised .
this is why i run 2 sets of injectors on my car as do some other tuners on full race spec n/a cars ,never mind boosted ones .

[axsaxoman]

Originally Posted by Gareth_R

running 2 bar of boost with a 3 bar fpr wouldnt result in 1 bar of fuel pressure. Pushing boost through my fpr raises the pressure (from 4 to 4.5 bar). Whether thats the case for all fpr's i dont know but mine is only a standard little one that fits into the fuel rail.

I was saying that with static pressure fuel reg -not with pipe connected .
I have had problems with the consistancy of this rise in pressure when using regs ,so I prefer to have all increase in fuelling done by the mapping ,if your reg throws a wobbly and doesn,t raise the pressure ,then you stand a good chance of running lean --your choice of how to do it

[ThrushMotorsport]

Originally Posted by axsaxoman

I was saying that with static pressure fuel reg -not with pipe connected .
I have had problems with the consistancy of this rise in pressure when using regs ,so I prefer to have all increase in fuelling done by the mapping ,if your reg throws a wobbly and doesn,t raise the pressure ,then you stand a good chance of running lean --your choice of how to do it

Well in my case it will be mapped properly doing a live map from either matty at wallace performance or ricky gauld, so my fuelling will presumably be controlled by that, should eliminate things like that if done properly?