View Full Version : cheap top feed fuel rail for 2nd gen 3sgte

04-17-2010, 04:53 AM
just thought i'd post some of the stuff i've posted over on the MR2 boards over the years.

this how-to assumes two things:

1. you have the fuel pump to support these injectors

2. you have the engine management to control these injectors.

i came into a set of WRX top feed injectors for about $100 (they range from $100 to $150). these are 420cc/min- that is until you dremel the caps off the ends of the nozzles. they will then flow 750cc/min.

on the left is an unmodified injector clip. on the right is an injector with the side tabs on the plug filed off so that it plugs directly into the stock wiring harness. these are also high impedance injectors, so you can eliminate the injector resistor box in the engine bay.

our top feed fuel rail comes from the camry/celica/MR2 5SFE. i paid $4 for it at the local pick n pull. they usually don't sell for more than $20. it has a 12x1.25 feed inlet with a bolt on FPR. the hole for the FPR is almost exactly the correct size to be tapped for another M12x1.25 threaded inlet. aisin was also nice enough to put a chamfer on the hole for the stock MR2's FPR o-ring to seat in.

for those who question the 5SFE rail's ability to deliver fuel, i submit this:
that's a rail that i cut in half to get a cross section of the bore. as you can see it's easily more than 1/2" in diameter. that's equivalent to the ID of -8AN hose.

here are the WRX injectors in the rail:

the injector bungs you see on the ends of the injectors are merely the ends of a stock 3SGTE fuel rail cut off and cleaned up. if you're hesitant to hack apart the stock rail (why i have no idea- they're garbage anyway), the toyota previa uses similar sized side-feed injectors that would likely fit our heads as well. the injectors are sealed into these bungs using standard DSM injector insulator seals. normal denso top feeds will seal just fine using o-rings as well.

standard ND style injector seated into the cups:

you have to make a couple of S brackets to bolt the rail to the head. from top surface to bottom surface, these measure 42mm, and the holes are 27mm apart, center to center. the top hole is 5/16" diameter and attaches the bracket to the rail via an M8x1.25 nut and bolt, and the bottom hole is 7/16" and bolts to the head.

side view of the brackets:

some pics test fitted:

and here it is, bolted in using the stock feed, stock fuel pressure regulator and plugged into the stock wiring harness:

in retrospect i probably shouldn't have bothered painting it. this is pretty much just an interim solution until i get some rail extrusion and build a proper rail, but it's very cheap and easy to do.

all you need is:

2 x M8x1.25 bolts and nuts
1 x strip of 3/4 x 1/8 aluminum stock
DSM injector insulators or o-rings to seal injectors into cups. find a junkyard, any 4cylinder mitsu engine will have these. you'll have to sift a while to find a set that don't crack when you pull them out. or get them here (http://www.importevolution.com/product_info.php?products_id=3767) new for $10.
1 x M8x1.0 shorty bolt to plug the cold start injector feed hole. if not, the stock CSI feed should be able to be made to work.
2 ft of 1/4" ID fuel hose to extend the return line
2 ft of 3/16" ID vac hose to extend the vac hose to the regulator.

drill with 5/16 and 7/16 bits
M12x1.25 tap. if you don't have one, most local hardware stores will perform this step for a couple bucks. you could also just use the 5SFE FPR, as it's set for the same pressure and the flow characteristics are the same (at least on the ones i've cut apart).

joe's gt
04-17-2010, 07:03 AM
Awesome ingenuity man. Great Work!

How do you make sure the injectors each flow the same amount? Aren't those injectors designed to precisely meter fuel. Dremeling off the caps seems kind of imprecise.

04-17-2010, 05:17 PM
joe i think those injectors are precisly metered for fuel flow, but i think if you increase the size of the injector and they are all within the same tolerences i would think they would flow the same rate based on volume flow rates. the design of the fuel rail would play into the flow rate

correct me if im wrong karl

04-17-2010, 06:48 PM
when people started cutting the caps off of them, they would send them out to get them flowmatched/cleaned. after a while people stopped doing it because they always came back within spec.

they're essentially a high flow denso injector core with an external means of altering the flow rate for flexibility across platforms.

this was more about using the 5SFE as a top feed fuel rail anyway :D sorry, but fuck paying $200 for a foot and a half of rail extrusion with 4 holes drilled in it. i find some of the prices vendors charge for simple things to be downright offensive.

04-18-2010, 05:04 AM
Looking over this thread again makes me want in stall my rail...only wish dental work didn't cost so damn much...would've had my crap installed by now :(

What rail you moving onto for next season? I know you have at least the 3sge one and the -8 to play with

PS - if anyone wants to try out a 5S rail I've got at least one here for dirt cheap. :)

04-19-2010, 08:02 PM
Looking over this thread again makes me want in stall my rail...only wish dental work didn't cost so damn much...would've had my crap installed by now :(

What rail you moving onto for next season? I know you have at least the 3sge one and the -8 to play with

PS - if anyone wants to try out a 5S rail I've got at least one here for dirt cheap. :)

i'm setting up the 3SGE, since that's what i have fittings for. i would anodize it, but there are steel caps on the ends that i haven't figured out how to remove yet. that's the only thing that really prevents it from being anodized. i should anodize that -8 just for the hell of it :D

EDIT: also, when buying fittings for the fuel rail, check the ID of the fittings before installing. i had two fittings from earls that were -6, but choked down to about 3/16 ID through the fitting body. i threw them on the drillpress and hogged them out to 5/16, but that could be a significant restriction in the fuel system if you're not aware of it.

it's actually pretty easy. here are the porsche brake caliper brackets and my custom throttle cable bracket (i used a celica cruise control cable for my 3SGE manifold setup)

that's just RIT clothing dye. if i were going to do anything for production, i'd get the stuff caswell sells. these turned out pretty decent though, IMO. all you need is some lye (for etching), sulfuric acid (anodizing bath) and a battery charger.

05-02-2010, 03:47 AM
here's a celica 3SGE top feed rail with custom brackets ready to mount on a 2nd gen 3sgte head:



i used 1/8" aluminum angle with 2" legs. i only wanted a scrap and when i handed the cashier the order card, she said "oh for god's sake," stamped it paid and told me to have a nice day :D

for the WRX injectors, it's 33mm from the surface the injectors push into to the bottom of the bracket, and the mounting hole in the bracket to the head is 18mm from the back of the vertical leg.

i'll take a pic or two tomorrow of it mounted up in the car. didn't finish reassembling the car until about 6am today.

05-26-2014, 08:43 PM
Just wanted to add that a Honda d series fpr bolts to the stock 5sfe location so one could use a Blox adjustable diaphragm on a Honda regulator or buy an Aem to have an adjustable fpr.