Supplementary Injectors

[S13Ka24e]

I would like to start this thread to talk about the advantages/disadvantages of supplementary injectors. Also the different systems out there. I was told by a friend to check out supplementary injectors for my project because it would be easier to tune off dyno than a piggy back, and since i have to go through emissions I can just turn the boost down and run the car stock. I have just a few questions and please add any information that could be helpful on the subject.

1. How bad is it to use supplementary injectors because your stock injectors stay at full injector duty?

2. I know that greddy e-manange can control injectors, also SDS has a system too, any others?

3. Are there any risks involved with spraying the fuel before the thottle body due to uneven feul distarbution?

Please add any thoughts and suggestions.

[WDRacing]

Please note that this is only my personal experience with secondary injectors, as well as my opinion on the matter. Everyone has different points of view

Mine happens to be not to use them. If your stock injectors run on max duty cycle eventually they will overheat and die, causeing that particular cylinder to run lean and detonate.

Personally, if your going to use a secondary system, there isn't anything better then alcohol. Its easier to install aswell as tune. It lowers the combustion temps tons farther and when ignited, produces 15% more power then 91 octane pump gas. By the way, one of the best kits on the market costs $350.

If you haven't read my thread on alcohol injection, I'd suggest it. It's very informational if nothing else.

I'd like to see some different opinions on secondary injectors as well.

WD

[C-Kwik]

I'll try to give a more objective response than WD. He's quite biased towards alcohol. Not that alcohol is a bad thing. I inject alcohol usually every weekend. Oh wait...we are talking about cars.

Personally, for simplicity, I would try to use larger injectors first on a street car. If you have no desire to run alternative fuels, then you may not need additional injectors. Larger injectors usually suffice. But there are limitations. Injectors work off pulse widths. If you go too big on the injectors the injector driver may not be able to precisley meter fuel at idle and low RPM's because it can not open them and shut them again fast enough. JWT says they can not go beyond 72 lb injectors on a Nissan ECU. In cases like this, you may still need additional injectors. You could go with a simpler set up of one or two or more injectors that spray into the intake pipe before the throttle body to add more fuel. Distribution will be fine as long as you mount it far enough from the throttle body so that it has time to mix evenly. Before throttle injectors have a disadvantage that more of the fuel may get absorbed into the intake piping and manifold walls before it gets to the cylinders. But will still be effective to add more fuel if set-up properly.

Or you can go to a full blown dual stage set-up with an additional injector per cylinder mounted in the intake runners or the like. This is much better for the fuel, but still not as good as direct port injection. Systems like this can be a bit more complicated and are more expensive.

Any kind of supplementary system can be used for alternative fuels, such as alcohol. If alcohol is not easy to access, you can also use race fuel as a supplementary fuel. Personally, I plan to stay away from alternative fuels since gas prices are already high enough as is, and is readily available.

Lastly, there may be some specific properties of a fuel like alcohol. WD can probably hed some light on this. I know Methanol is a form of alcohol, and is very corrosive and also requires more volume of fuel for a given amount of air. But it is very effective in race cars. I believe methanol race cars tend to run primarily on methanol though.

[WDRacing]

For a KA to actually need secondary injectors, you'll be making some very serious hp. If we use JWT's ECU for an example of engine management, running a 72 lb injector being tha max capacity on that ECU.

That means you'll be making close to 500hp at the wheels before you actually need to upgrade.

WD

[matt0941]

feul distarbution?

Please add any thoughts and suggestions.

Ahahha

If your stock injectors run on max duty cycle eventually they will overheat and die, causeing that particular cylinder to run lean and detonate

(running) "She's gonna blow!"

Ok I am almost done laughing I couldn't really get much information out of this post besides that due to the fact that I am really tired. But here are my questions (I think people love answering them cause there so stupid... now where's that retard smily): What is the lb. to cc conversion? And what is the stock size for injectors on KAs?

[cnichols]

And anyone actually serious about making that kind of power would not be using a JWT. 50 lb/hr injectors should be good up to a little over 400hp.

[C-Kwik]

Actually, now that I read Matt's Response to WD about the injectors dying, I've never heard this before ever. I run an FMU right now and it does max out (I guess around 4000 RPM) and no problems so far. I've never heard any problems with this on any injector. And if this was really a concern, I doubt Corky Bell would be saying that an FMU is a decent way to add additional fuel for a turbo system since pretty much most systems would max out the injectors at some point if an FMU needs to be used.

[cnichols]

Ahahha

(running) "She's gonna blow!"

Ok I am almost done laughing I couldn't really get much information out of this post besides that due to the fact that I am really tired. But here are my questions (I think people love answering them cause there so stupid... now where's that retard smily): What is the lb. to cc conversion? And what is the stock size for injectors on KAs?

Stock KA injectors are 270cc...correct me if I'm wrong.

Conversion from lbs/hr to cc/min = lbs/hr x 10.515

[matt0941]

270cc sounds familar... so lbs is 270/10.515? I hope injector size to HP is covered in the faq.

[C-Kwik]

For a KA to actually need secondary injectors, you'll be making some very serious hp. If we use JWT's ECU for an example of engine management, running a 72 lb injector being tha max capacity on that ECU.

That means you'll be making close to 500hp at the wheels before you actually need to upgrade.

WD

For any motor to need secondary injectors, it would only need to exceed the capacity of the primary injectors. My point about using large injectors is that if you go too large, the ECU, or even whatever other fuel controller will not be able to provide a stable idle.

The Direct Gasoline Injection motors (Where the injector sprays directly into the cylinders) use higher voltage electrical systems to be able to provide a more precise fuel delivery. And these motors use very high fuel pressures in order to offset the pressure in the combustion chamber. And because of this and the fact that they can be designed to run extremely lean at idle, they need very short injector pulsewidths. The higher voltage system is required to achieve this according to the articles I've read. This is a bit offtopic, but important to point out as 12 volt systems are more limited in this area. Others as well, but that would get way off.

[cnichols]

270cc sounds familar... so lbs is 270/10.515? I hope injector size to HP is covered in the faq.

Yes, approximately 26 lb. injectors...at least that sounds right.

[WDRacing]

For any motor to need secondary injectors, it would only need to exceed the capacity of the primary injectors. My point about using large injectors is that if you go too large, the ECU, or even whatever other fuel controller will not be able to provide a stable idle.

The Direct Gasoline Injection motors (Where the injector sprays directly into the cylinders) use higher voltage electrical systems to be able to provide a more precise fuel delivery. And these motors use very high fuel pressures in order to offset the pressure in the combustion chamber. And because of this and the fact that they can be designed to run extremely lean at idle, they need very short injector pulsewidths. The higher voltage system is required to achieve this according to the articles I've read. This is a bit offtopic, but important to point out as 12 volt systems are more limited in this area. Others as well, but that would get way off.

I'm far to biased towards alky like you said. But thats just me. I know a ton of people who run sub injectors on there cars with good luck. I have to quite trying to get everyone on the alky kick.

I was reading about that DGI stuff, I can't wait until that technology hits the streets.

WD

[encasemyheart]

Actually, now that I read Matt's Response to WD about the injectors dying, I've never heard this before ever. I run an FMU right now and it does max out (I guess around 4000 RPM) and no problems so far. I've never heard any problems with this on any injector. And if this was really a concern, I doubt Corky Bell would be saying that an FMU is a decent way to add additional fuel for a turbo system since pretty much most systems would max out the injectors at some point if an FMU needs to be used.

Are you serious? Your injectors run at a 100% duty cycle? The FMU is a valid way of controlling extra fuel but you have to watch out for your injectors. We have to upgrade injectors so soon on our cars because the stock injectors are so small for our needs. I believe ITR injectors are bigger, or very close to the same size with a much smaller displacement, .6 liters smaller.

Anyways you never hit 100% duty cycle, I personally wouldn't ever go past 80-85% duty cycle. If an injector fails, especially in boost when you need the fuel badly it would be an engine meltdown...not good. But I suppose it's an excuse to go to forged internals. But if I misread your post excuse me, I'm very tired.

[C-Kwik]

Are you serious? Your injectors run at a 100% duty cycle? The FMU is a valid way of controlling extra fuel but you have to watch out for your injectors. We have to upgrade injectors so soon on our cars because the stock injectors are so small for our needs. I believe ITR injectors are bigger, or very close to the same size with a much smaller displacement, .6 liters smaller.

Anyways you never hit 100% duty cycle, I personally wouldn't ever go past 80-85% duty cycle. If an injector fails, especially in boost when you need the fuel badly it would be an engine meltdown...not good. But I suppose it's an excuse to go to forged internals. But if I misread your post excuse me, I'm very tired.

I came across this in search of something else. I guess I never responded to this. so here goes. Unfortunately, the injectors are controlled by the ECU. With too much boost, it will max out the injectors. But the problem is that even then, they can't supply enough fuel. So that's where the FMU comes into play. While it is optimal to run under 85% or so, it is not because of the chance of overheating, it is because at some point, it will not have enough time to fully close and reopen. So by default, it would just fail wide open even though the signal isn't maxed out yet. Kind of like a large injector with too short a signal won't open all the way and cause idle issues.

[Red Lightning]

I read sometime ago on FA there's a guy who ran 4 sub injectors, one on each intake runner. He got good results. The search is down on FA, if anyone bookmarked that post can you please post a link. Thanks.

[tapdeznutz]

i have read everyone's replies but i still have a question or two. first off for daily driver purposes having an additional injector combined with FMU should be enough fuel for stock boost right? EI 7 psi? i know everyone talks about bigger injectors and bigger boost but for us peeps that only really want more power in a cost effective manner it should be fine right? considering this now give me your feedback on additional injectors. i really want to know because i have a couple of stock replacement injectors lying around and want to put them to use. and i dont want to go out and buy bigger injectors and go thru the extra work of having them fitted or whatnot. let me know guys thankx in advance

[sil80drifter]

Isn't Direct Port Injection same as GDI? If yes then it has been "on the streets" for a while on the newer cars, like the 4th gen maximas, etc.

sil80