Staged injection

[Sam_Q]

I would like to know how people have setup their staged injection in terms or electronicly and plubing wise.

I am sure many people are just using an extra 4 outputs in their ecu but is it possible to just have 4 relays and an rpm switch for the injection turn-over?

also do I just have a second fuel rail in series with the first and the fuel reg at the end?

[mrshin]

Just turning on four injectors suddenly is hardly beneficial for power... Plus, that kind of behaviour is best left to the guys who fits 'extra injectors' to their VL turbo. As for how serious the fuel system in question needs to be, it depends how serious the engine itself is...

[The Last Streetfighter]

There is a very good thread on here about one of the racer boys in I think it is a 3SGE.

[Sam_Q]

no I didnt mean just to turn on four extra injectors that would just stall it, I mean to switch the signal through the relays from one set to another, like a vtec setup for the fuel if you know what I mean.

streetfighter: yeah I had a read earlier, he had some amazing results and why I am interested in doing it

[Kedderz]

why not just get huge 1000cc injectors and tune properly? surely it would be easier and more cost effective to go this route?

[Sam_Q]

theres an advantage and a disadvantage to running an injector in a different position, hence the concept of switching betwen them. My standard injectors are just fine in terms of size for me. Its not just a matter of the right injector size. Besides I doubt I would get an idle anymore with injectors that big

[Norbie]

I am sure many people are just using an extra 4 outputs in their ecu but is it possible to just have 4 relays and an rpm switch for the injection turn-over?

In terms of electronics there's no reason you couldn't do it this way. The injectors have a switched ground and constant power, so you'd hook up the ECU to all 8 injectors and switch power to each group as required.

Whether you'd get a smooth transition doing it this way is another matter though. IMO you'd be better off using one of the higher-end ECU's which natively supports staged injectors.

[Sam_Q]

Norbie: I would of thought if solid state relays would be used then it would be an instant transition.

[Norbie]

Electrically speaking it will be near instant, but I was talking about how the ECU will cope with the injectors suddenly getting bigger. Having never done it I don't know, but I can't help thinking there could be some issues there.

[roadsailing]

you mean transistors?

[Hen]

Also the different location may mean different time from injection to chamber, so as they switch from the head injectors to the trumpet injectors you get a momentary lean spot, and rich spot on the reverse. This may of course turn out to be a totally negligible effect though.

I'd think that an ECU that can control it (and I think some even blend it, rather than a sharp switch) would be a good idea if you really want to do it.

Hen

[thechuckster]

this simplistic approach might be an showstopper if the ECU uses lowZ injectors and peak-and-hold to open injectors. A simple silicon switch cannot do managed current control without suitable driver circuitry.

Would make 10476% more sense to use an ECU that support staged injection.

[Sam_Q]

ok sounds like we have a verdict here, thanks guys

[Bored?]

If you wanted to do this (and I'm not saying it's a good idea), and you had an ECU which supported multiple maps, one way to do it would be to use a relay to ground one bank or the other, and using the switched ground as an input to switch between the two maps. This is necessary because you need totally different maps for the two different injector sizes anyway.

The only concern i have is that if you use a relay instead of a transistor, the switching time could result in a very (very) short lean condition. It is probably so fast you wouldn't notice though.

Of course you'd still be better off with an ECU designed for it.

[Celica RA45]

to run 2 stage properly you need to blend them together and have 2 fuel maps as my set up still has the inboards using 15 % at full throttle and 85% out board to get the right set up plus 2 different set ups for end of injection timming as well .
could not see it working with relays