Mounting secondary injectors

[RS/377]

Hello

I am starting my new engine tomorrow, and instead of going with larger injectors, I would like to know how feasible it is to run a second set of 450's.

I have a PMS, and they offer a secondary injector driver for that system.

The biggest question I have, is where do people physically put the second bank of injectors?

From searching the archives, I haven't seen a anyone using the secondary injector driver, and can't find a pic or description of people running secondary injectors.

Thank You

 

[T6Rocket]

450 + 450 = 900cc = a lot of injector! You would need to be in the 700 Hp range to need injectors that big!

Keep it simple & go with a single set of larger injectors.

Al

 

[rdrkt]

Injectors are phenomenally cheaper than they were 5 years ago. You can get pretty much any DSM size injector that you want for less than $550. Its so much easier from a tuning standpoint to use 4 larger injectors.

 

[L2RTSiAWD]

I have only seen 2G nT's put a second bank of injectors on the back of the intake manifold.

but Rdrkt is right. You can get injectors so cheap now and it's so much eaiser to tune.

 

[RS/377]

The main thing I'm worried about is keeping a good idle, as I do want to drive this car on the street every so often.

I also have two sets of 450's, and the driver is cheaper than a set of injectors, and I would never need 900cc of injector.

But if it truly that much harder, I'll just get a set of larger injectors.

Thank You

 

[talonted_one]

the secret to a better idle....Apex-i SAFC.

cheap and effective

 

[CraigB]

It would not be that hard. You can put 1 injector in each runner. You can probally mod a stock fuel rail to work or you can buy bulk fuel rail and make one yourself. You will need to have a machine shop make parts or I think Greddy sells injector holders.

 

[L2RTSiAWD]

Originally posted by RS/377
The main thing I'm worried about is keeping a good idle, as I do want to drive this car on the street every so often.

I also have two sets of 450's, and the driver is cheaper than a set of injectors, and I would never need 900cc of injector.

But if it truly that much harder, I'll just get a set of larger injectors.

Thank You

If you want good Idle having 550cc or 660cc worth of fuel out of 4 injectors is going to be easier to get good idle than have 900cc of fuel coming from 8 injectors.

 

[rdrkt]

John the thing with secondary injectors is that they only come on at a preset load or rpm level. If I got 650cc injectors to idle with undegreed web street cams I am supremely confident than anyone here can dial in smaller injectors with a SAFC

 

[GalantVR41062]

I had 750s idle fine but stock cams though, and if you have the injectors, and fuel controller for them I say run a T or split fiting befor the fuel rail and just install a nother stock rail then conect the two outlets again befor the FPR which with dash lines after the fuel filter and an after market threaded in and out FPR it would not be that hard to do you would just need to drill the holes in the manifold and have a way to mount them, good luck or just buy a bigger set of 4 injectors, kind of the "norm".

 

[L2RTSiAWD]

Originally posted by rdrkt
John the thing with secondary injectors is that they only come on at a preset load or rpm level.

Ok that's using the PMS. I see now.

 

[Bohrn]

how about 1 extra injector??

450 more cc's?

450x4=1800+450=2250

550x4=2200


so 5 450s would be pretty dang neat, stock idle, just have to wire in that last injector to come online at say 15psi or something.

Anyone done this?

IF you already had a larger fuel pump, the cost of a pressure switch and 1 injector should be pretty cheap. Hell a used automatic injector would be real cheap and still pretty close to the combined figure for 4x550.

I know they do this in the 2.2l turbo Dodge cars and others.

 

[pneumo]

Good idea in theory, but it doesn't work that well in practice. The best place to put one extra injector is around the throttle body or throttle body inlet, that way all 4 cylinders have a chance at getting equal flow. That's how they did electronic fuel injection in the early days. They stopped doing it that way because the fuel doesn't get spread around equally, especially at high airflow. The fuel is more dense than air, so when it's time for it to turn 90 dergrees from the intake plenum to the intake runners not all the fuel makes the turn. Some fuel sticks to the walls, forming droplets, and more ends up in cylinder #1 than in #4.

Maybe the best use for the extra injectors is to sell all 8 to someone with an auto trans 1G or a NA car and use the $ for 4 big injectors.

 

[FastRthenU]

There is a drag car here in ontario. Ian Currie, you might of heard of him? He's runing 4 450cc injectors, and i think he drives it on the street as well(Somtimes). Maybe you can talk to him. I have seen him on the Canadian Dsm board before.

 

[Bohrn]

we all get 4 450s stock with turbo 5spd cars. Do you mean with 5 of them??

that would be interesting.

 

[RS/377]

I actually hadn't thought about selling the injectors, good idea though

 

[Team Ducktape]

http://www.sdsefi.com/eic.html

 

[Bohrn]

thats kinda neat there Team Ductape, but cost prohibitive. For the cost of the controller and the 2 injector setup, I could have a set of 510s or 550s and an S-AFC.

That was my original reason to go with a standalone injector with a pressure switch to activate it. Cost.

1 used injector, $50 bucks, 1 pressure switch, $20, and a bit of fabbing.

Should be able to do it for under $100USD.

But, there must be a reason why no one has done this that I am missing.

Maybe a 190lph fuel pump, with base pressure turned up a few lbs will do fine until the bigger injectors/S-afc are needed.

 

[Team Ducktape]

All you would need is the controller, and some spare 450's- don't need the rest. So it woiuld cost like $350 for the whole thing including injectors. And anyone who is going to this "should" beable to make the injector harness, or use two injector "plugs" off a old junk harness.

 

[Bohrn]

hmmm...

 

[CraigB]

The Emanage will control sub injectors and you can buy it and the injector harness for less than 350.

 

[ItsStockOfficer]

8 injectors works great....Ive seen a car at RRE do it. Had a fuel rail from a 323 GTX on the underside of the intake manifold, its shorter so itseasier to mount with being banging against the head. I have 5 injectors....a extra non turbo injector.

 

[Bohrn]

ItsStock, do you have any pics of your extra install??

Any info on how you did it?

What fuel system mods do you have on there?

I have been thinking of doing this, as I cannot afford 4 550 injectors and an S-AFC. But I can afford one used injector, and maybe some wires etc.

 

[FastRthenU]

oppps. my bad i meant 4 extra 450 's. not jsut 4. sorry about that. Yah magnus built the car and it seems to work well.

 

[greyforestgst]

if you're going to use a secondary injector, why not inject propane?