best option for upgrading injectors?

[marco]

it is looking like i am going to have to look at my fuel system if i am going to get the most out of my latest mods, and was hoping for a bit of input as to the best route.
the car will have a set of BNRs on a streetported engine, with a well ducted Greddy SMIC and a 2D mappable WI system (if FJO ever actually start producing their new kit...), am hoping to hit around 350 at the wheels, but if it is slightly below i wont lose sleep over it.

the way i see it i have the following fuel options.

just increase the fuel pressure with a decent FPR and fuel pump (i have a supra pump to go on, so take it as read in all of the following that it is installed) -however i don\'t think it will give enough fuel

run 850s on the primaries- looks to be the cheapest option, but have heard stories of having trouble setting idle, and means i am relying on old injectors

run after market secondary rail- sorts out idle problem but is there an issue tuning them when the secondaries come on line due to the size difference between the two?

run after market primary and secondary fuel rails and new injectors- can cherry pick the injector sizes for correct capacity and avoid large size difference, but it is going to cost a lot more (would guess £500-600 to do it properly).

so, what do you recommend? would particularly like input from tuners about possible issues and just how much of a problem they are. i know money no object it would be best to go for full after market rails, but would i get any real world benefit from it?

ta in advance

Marco

[chrisJDM]

I would say all you need is some 1600cc secondary injectors, a great upgrade for upping the boost on the twins and also i know a few people that are running standard primaries and 1600cc secondaries on single turbo set ups.

I went for the following kit, comes with everything you need including the competition rails:

  http://www.rx7store.net/product_p/extremefuelfd.htm

[Timmy]

I would say deffinatly need bigger injectors. I\'ve maxed the stock ones out at half throttle at 4500 rpm on stock twins. That was stock fuel pressure but even upping it would be touch and go plus there is a preferred fuel pressure.

[m1tch]

Apparently the stock 550s can take up to about 370ish bhp b4 they max out, perhaps just uprate the secondarys as after 3,500 the primarys throttle back and switch to the secondarys, I think there is a program on here somewhere that tells u the kinda of maximum bhp u can get from different injector setups

found it:

http://www.rx7.com/calculators.html

[Timmy]

if that calculator is correct i must be running approx 400bhp on stock ic and turbos...........

[shaunwil]

The yanks bhp is usually a lot higher too !

You can up the pressure on the rail to get more out of injectors but you need an after market ecu and a Fuel pressure regulator but you pretty much all the way to having larger secondaries.

Shaun

[marco]

ok, have been giving this more thought (and it has nothing to do with it being payday on Monday and it is burning a hole- oh no...)

are there any problems with having large secondaries (1600) with stock primaries, e.g. around the transition point or is it totally fine? i want to do this properly and get it right first time, so am happy to bite the bullet and buy full primary and secondary rails with new injectors- but if i can save myself a couple of hundred quid i will do....

[chrisJDM]

i ahve noticed no issues at all or problems with change over and i have this setup