Gen 2 3sgte fuel rail capabilities

[GriZZly]

Basically what i need to know is how much a stock gen2/st185 fuel rail will flow before it starts leaning out the cylinders?

[-Totenkopf-]

Im not quite sure what you mean by 'how much it'll flow' but people start to encounter problems between 250-275rwhp in the MR2. Basically the boundary of the stock injectors. If you are planning on upgrading the pump and fitting an aftermarket adjustable FPR, then you should have the rail bored out then. It doesn't cope too well with increased fuel pressure and flow.

Hope this helps a little.

[GriZZly]

the car already has a rr fpr.. however itll soon be scoring a new fuel pump and 800cc injectors..

yeh basically wanted to get an idea of power or boost pressure before it starts being an issue

thanks for the info

[thechuckster]

Unless you were thinking of running methanol or something exotic, you'll find the stock fuel rail for most EFI cars is not a limitation. The fuel lines feeding the fuel rail will have a much smaller ID and it will be they that first introduce supply issues.

fwiw, you can use the stock fuel lines from an AE86 or RA23/8/40 to run 4agze of 1GGTE engines or bigger.

A high-pressure EFI fuel supply doesn't need big fuel pipes unless you want stratospheric horsepower levels.

Given that you're running a rrfpr, larger pump and massive injectors, the return line is more likely to be an issue than the supply line.

[-Totenkopf-]

I don’t know about that. The 3S-GTE fuel rail has proved itself to be a limitation. The stock fuel lines are more then capable of flowing enough fuel for 400wheel horsepower. The fuel rail, in the gen2, must be poorly designed. When more fuel or higher pressure is forced through it, it appears to cause a pressure differential between the two ends of the rail, causing inconsistent fuel injection to each cylinder.

[spectral]

-Totenkopf- is correct. The way the stock rail feeds into the end of the rail means for large injectors, it can't maintain adaquate flow to the end of the rail. Lean outs on the end two cylinders are common.

The 3 solutions are :

* Bore out the rail to 5/16"
* Mod the rail so the CSI output becomes the main input (obviously no CSI anymore) and dual return (each end of the rail)
* Mod the rail so its dual feed, with the return in the centre

Ideally you'd do a combo of the above for really big injectors. Dual feed, Centre return and bored out to around 5/16". Don't go too big as there isn't a lot of meat in the rail.

[thechuckster]

weird that the rail should have such a small (e.g. sub 5/16) ID ... perhaps the centre-feed design of the injectors interrupts flow along the rail too much?

i leanr something new every day

[Andrew162]

have you considered going with a Gen III 3S-GTE fuel rail instead? I know that these have no probs flowing equally to 540cc injectors. would this be a do-able option?

[GriZZly]

im taking any and all options/opinions at this stage.. the cheapest safe option would be my preference..

[oldcorollas]

it's not like a full custom rail using extrusion is that expensive... why not do that?
(ie, efi hardware etc)

[RA23]

it's not like a full custom rail using extrusion is that expensive... why not do that?
(ie, efi hardware etc)

I'm not sure what a 3S fuel rail looks like exactly, but unless you can design and machine it yourself, custom is not cheap.
FWIW, we used to get custom fuel rails from extrusion for an Audi V8 based race car. By the time you design the thing with the right tolerances (CAD), add the injector brackets and cut some weight out of the rail, the assembly was something like 300 Euro
Anyway, the 3S one may be a lot simpler....

[-Totenkopf-]

No use trying to use the gen III rail. Doesn't fit up to the gen II head.

[thechuckster]

fwiw: i bought a metre of alloy fuel rail from Speed Technologies a while ago for ~$70. I had a local machinist drill 4 holes for injectors and tap the ends for screw-in fittings for even less (cash). The fuel rail has two flat sections you can screw into to mount the rail.

[oldcorollas]

http://www.twminduction.com/EFI/EFiF...Extrusion.html
http://www.directignition.com/efi_parts.html
http://www.efihardware.com/
http://www.aeromotiveinc.com/pdetail.php?prod=59
http://www.trademe.co.nz/Trade-Me-Mo...n-72111818.htm
http://www.rossmachineracing.com/extrusionhouse.html (dash 6, 8 and 10)

most places sell by the foot.

[oldcorollas]

and OT.. this is bloody snazzy
http://www.rossmachineracing.com/dplenum.html