Anyone running 2 sets of injectors?

[2muchboost]

So I have been doing a little bit of research to get a better understanding of how to properly run 2 sets of injectors. The theory is that a smaller set of "primary" injectors are used under normal driving conditions and a set of "secondary" injectors are setup to kick in at a programmed rpm/boost level/spark....etc.

This concept interests me for a number of reasons but one being fuel consumption and driveability. In the future I will be using my car 2-3 times a week to commute to work (70+ miles a day) in order to give my poor daily a rest. It would be awesome if I could keep close to stock mpg when driving the car under normal conditions and then have a set of upgraded injectors kick in when they are truly needed at which point I would watch my mpg disappear.

I would like to hear from anyone that has done this and what their experience has been like...both good and bad. To be honest I am not hell bent on keeping good mpg on my 240sx because I have a daily but if I could set the car up with a setup like this then I would be interested in possibly doing so.

FYI if anyone cares to know, the setup would be controlled by a Pro Efi 128 unit since its already waiting to be installed.

I have posted a link to SF where one of the members a different setup with his RB30 swap and so far has had great success. I frequently talk to the member there but am interested if anyone here has some insight to further the knowledge. He is running a Walbro 255 at "low" demand and a Bosch 044 under "high" demand.

Supraforums.com (http://www.supraforums.com/forum/showthread.php?667680-RB30-240-finally-brakes-into-the-10s!&p=8746965&highlight=#post8746965)

PS: Mods if this is in the wrong section please feel free to move.

[[email protected]]

what size are your primaries?
I daily'd 1000CC injectors no problem

[2muchboost]

I actually have 1200s which I havent installed but for some reason it interests me to have something like FIC 650's which would be used under normal daily driving and then having the added benefit of having the 1200's kick on at the track or those very few times I may decide to drop the hammer on the streets (im too old for street racing lol).

I was also talking to another SF member who uses both 2 fuel pumps and 2 sets of injectors. I dont mind running 2 pumps similar to the guys post which I referenced but it always intrigued me when I first saw a VW that was running primary and secondary injectors, with the secondaries only kicking on at +50% throttle and over a set RPM (which I forget now).

The 2 pump setup that was mentioned in that SF post has also triggered my interest.

How was your mpg affected with 1000's daily driven? I have daily'd 750's before and the mpg on my SR20 was pretty awesome even with all of the mods I had done to it.

Again, this post is meant to open the discussion up and get some knowledge.

[AsleepAltima]

i know i got really good mileage on 740's. 24mpg pulling a 500lb motorcycle on a 500lb trailer. even my sr before the rebuild was getting close to 30 with a 2871 and 740's. i think running 2 sets would just be a pain in the ass. how long before it pays itself off would be an issue too.

[[email protected]]

the 1000cc was on my old EVO8, my MPG wasnt effected
MPG is effect based on driving habits and a good part throttle tune which a street tune will do wonders for in regards to MPG.
my idle was fine too with them, my current SR has 1680's and have no idle problems

there are lots of 1200+ injected cars running around DD'd without trouble

[2muchboost]

ASLEEP very similar setup. I had the 2871 and 740's (sorry not 750's...typo before) and a full rebuild. I was getting between 25-28 mpg under normal driving.

But with the 1200's I am assuming the daily drive-ability and mpg will be decreased rather drastically especially on a 6 cyl vs a 4 cyl. Again, I could be wrong so those who have more experience please feel free to chime in.

Huh.....we shall see how I make out with the 1200's. I agree that MPG is very much dictated by street tune and driving habits. Again, with the kind of $ spent on this project and the fact that I am too old for Fast and Furious style racing, I will likely drive the 240 the same way I drive my Durango, slow as shit haha.

Im still interested in learning from those who have setup the two pumps like in the article and also those who run 2 set of injectors. I am not looking to run 2 sets of injectors now but for the near future it would be interesting to see what kind of info is out there and what it would take. Im still really looking at the at 2-pump setup.....liking that idea more and more.

[[email protected]]

Why double pumper? Aeromotive and DW intanks can support plenty

[2muchboost]

Santos I think we are saying the same but I may be wrong.

I am saying that I like the in-tank + an in-line pump idea is intriguing. Having to only use the smaller in-tank under normal driving and then having the in-line kick in when the added fuel is needed, both feeding into the rail and 1200cc injectors.

I already have a walbro 400lph ready for in-tank and have a Bosch 044 ready to be installed in-line. The reason this interests me is because A) I have both pumps ready for install and B) I bought both pumps for cheap and C) If I did twin in-tank I would have to run the same pump which means getting rid of my Walbro or Bosch to match either one of those up.

I have seen many people run twin in-tank setups but I am just trying to learn about the added advantage of different setups. The idea of twin injectors is so far from becoming a reality......its just more of a brainstorm then an idea at this moment.

[[email protected]]

it can be and has been done but its used a lot by the rotories because they eat up so much fuel on alky.
all set ups you will see with staged injection is running a alky based fuel system.
if you really wanted to do it its gonna take a lot of street tuning at different load tables and TPS%'s because it will vary greatly based on where your driving at the time etc.
plus the inline will have to be running continiously anyways because i dont think you can pump thru it if its not running

[Highway Riding]

I've only heard of this on rx7's.. In4moreinfo

[2muchboost]

Santos Agreed if there is 2 set of injectors it will make things much more complicated. I have seen it done on a few Supras but mostly on Rx 7's. i agree it would be a bitch to street tune and get the twin set of injectors setup correctly.....but thats what the EFI is there for hehe. Again for the twin set of injector ideas...I am merely at the wishful thinking stage and no where near enough knowledge and parts to even consider this a possibility.

Like I said I am really digging this In-tank plus In-line filter idea (dont make fun of me...for some reason this hadnt crossed my mind) running to my fuel rail with 1200cc injectors. If I could get this to work, in theory I would run the smaller in-tank daily and set it up so the in-line kicks on and off as needed. I could see how this setup would satisfy my requirement as long as its done correctly.

[Croustibat]

So I have been doing a little bit of research to get a better understanding of how to properly run 2 sets of injectors. The theory is that a smaller set of "primary" injectors are used under normal driving conditions and a set of "secondary" injectors are setup to kick in at a programmed rpm/boost level/spark....etc.

This concept interests me for a number of reasons but one being fuel consumption and driveability. In the future I will be using my car 2-3 times a week to commute to work (70+ miles a day) in order to give my poor daily a rest. It would be awesome if I could keep close to stock mpg when driving the car under normal conditions and then have a set of upgraded injectors kick in when they are truly needed at which point I would watch my mpg disappear.

I would like to hear from anyone that has done this and what their experience has been like...both good and bad. To be honest I am not hell bent on keeping good mpg on my 240sx because I have a daily but if I could set the car up with a setup like this then I would be interested in possibly doing so.

FYI if anyone cares to know, the setup would be controlled by a Pro Efi 128 unit since its already waiting to be installed.

I have posted a link to SF where one of the members a different setup with his RB30 swap and so far has had great success. I frequently talk to the member there but am interested if anyone here has some insight to further the knowledge. He is running a Walbro 255 at "low" demand and a Bosch 044 under "high" demand.

Supraforums.com (http://www.supraforums.com/forum/showthread.php?667680-RB30-240-finally-brakes-into-the-10s!&p=8746965&highlight=#post8746965)

PS: Mods if this is in the wrong section please feel free to move.


There is absolutely no gain to get in using 2 sets of injectors, on our engines anyway. there WAS an advantage before, because big injectors also meant big latencies, but it is not true anymore.

Some engines use dual injector setup, but they are BUILT for that in the first place. Most of these are bike engines that have specs like 15.000 rpm before redline, 200HP/L AND still meet emission regulations.

Your fuel system just delivers the fuel needed, if you deliver less you will just run lean and kill your engine. Want better MPG ? Get an economical engine. There is just no miracle in engine management. You could get slight better MPG by running higher compression ratio, but it also means high octane fuel ( read: use a 1mm HG and e85 fuel )

[2muchboost]

Croustibat Thanks for the information......this is why I started this post.

As noted this project will not be my daily per say but since I have spent countless hours building it I would like to use it a few times a week. I am not hell bent on mpg as building a setup the way I am...its basically asinine to try and keep 25 mpg and make the power I am aiming for. But it is wishful thinking to keep somewhat of an economical setup or at least better than the 12mpg that I have estimated I will get when the project is done lol.

I do see what you mean about only needing secondary injectors on high revving engines which is why it makes sense that rotary engines would run a secondary set.

But on the topic of not providing enough fuel I wonder how the guy on the SF post is running the smaller in-tank pump though he is using 1100cc injectors without having issues? I truly do not believe that the Walbro 255 would provide the required fuel for anything more then 3k rpm shift with his setup...but then again I could be wrong. I am not trying to be sarcastic so please feel free to educate me a bit. I can honestly say that fuel management is not one of my strengths when understanding the complexity of the fuel system and the engine & engine management.

I am running slightly higher compression then the typical 2jz since it will be somewhere around 9.2:1 vs the usual 8.5:1 GTE compression.

[[email protected]]

What is your current power level and what fuel?
Auto or standard trans?

[2muchboost]

Current power level is 0hp because the engine and trans are out of the car at the moment lol. From August to February 2013 I will be running the stock 2jzge while my spare head and trans get some work done. Keeping my fingers crossed hopefully next year I will be shooting for low 700s.

Trans is an R154 and the fuel I will be using is 93 Oct and E85 whenever I plan to have fun. All of this is dropping into my S14 chassis.

[Croustibat]

Croustibat Thanks for the information......this is why I started this post.

As noted this project will not be my daily per say but since I have spent countless hours building it I would like to use it a few times a week. I am not hell bent on mpg as building a setup the way I am...its basically asinine to try and keep 25 mpg and make the power I am aiming for. But it is wishful thinking to keep somewhat of an economical setup or at least better than the 12mpg that I have estimated I will get when the project is done lol.

I do see what you mean about only needing secondary injectors on high revving engines which is why it makes sense that rotary engines would run a secondary set.

But on the topic of not providing enough fuel I wonder how the guy on the SF post is running the smaller in-tank pump though he is using 1100cc injectors without having issues? I truly do not believe that the Walbro 255 would provide the required fuel for anything more then 3k rpm shift with his setup...but then again I could be wrong. I am not trying to be sarcastic so please feel free to educate me a bit. I can honestly say that fuel management is not one of my strengths when understanding the complexity of the fuel system and the engine & engine management.

I am running slightly higher compression then the typical 2jz since it will be somewhere around 9.2:1 vs the usual 8.5:1 GTE compression.

I cant talk about the 2JZ, i have a CA18. I can tell you a single sard 280L/h is enough to power 4 ID1000s on it, and get roughly 580HP out of it (with a PT5858 turbo). So unless you really are aiming for 500+ HP, dont bother with a dual pump setup, and forget dual injector setup too.

Using dual injectors is a pain in the ass and really not required on these engines. You can get injectors as big as 2000+cc /min, which will be enough for 1000+ HP on e85... and still get the car to idle. That and there really is no benefit. Using 300cc/min instead of 600cc/min injectors just mean they will be opened twice longer, because the fuel quantity that has to be delivered is the same.

[2muchboost]

I can say I have learned a lot from this post and then taking this info and doing more research. I am actually aiming for low 700's as my power goal just because of the setup that I have and the tidbits I am picking up over the winter. Twin pumps will def be needed for my setup....no doubt about that unless I get a large external pump....but I am trying to stay away from that. I already have a set of 1200cc injectors which I would like to use and like to stick with if possible.

I think I am more so leaning toward the smaller in-tank running under normal driving and setup a secondary external pump to kick on as it is needed under heavy loads. I am constantly looking at new ideas so this was just another thought (twin injector setup)......that taught me that it would be a dumb idea lol.

[[email protected]]

your current pump set up will work leave as is no need to over think or re-invent the wheel.
im running 1 DW intake with 1680's and sitting at 595whp on E85 and my Duty cycle is at like 65%. i idle fine with my injectors and i dont even have a IACV installed.
you want good MPG with a good sized turbo you wont be making much of any boost on the street without loading it up so just tune your vacuum section of the map well and watch your foot your MPG should be near stock.

[Breitling]

I had a KAT with 8 injectors.... 1000cc and 600cc (and 1000 + 300 at one point) and we did the same thing (primary and high boost settings). We were using an electromotive TEC3 to control it. the only issue that we ever ran into was killign spark plugs because of the angle in which the secondary set were positioned... it looked like this.

http://img.photobucket.com/albums/v202/s15driftking/Random%20People/man2.jpg

http://img.photobucket.com/albums/v202/s15driftking/Random%20People/man6.jpg

http://img.photobucket.com/albums/v202/s15driftking/Random%20People/man8.jpg



Could support 800HP @80% duty
Could support 900HP @90% duty


Primary was 450-650whp, secondary was 650-850whp


the injectors ran in sync (all 8 all-time), in sequence (4 on low rpm, 8 on high rpm), in stages (4 on low boost setting, 4 on high boost setting), or single stage (whichever 4 are chosen). The idea behind it was for more fuel and better bottom end with superior top end fuel support. the majority of the time it ran it with 18 lbs of boost making 570whp.


I would not recommend it simply because we were replacing plugs frequently.

Had a high score on cool factor, high score on perfomance factor, and a low score on maintenence factor.

[Croustibat]

Breitling > I think you would have had the same or better performance with only 1 set of 1600cc. Most ECUs are made to open injectors sequentially under small /medium load, then all at the same time at higher load. The CA18 ECU does that. And when it switches to batch opening, it opens the injectors twice per cycle to get a better spray.

2muchboost > forget that pump setting either. Stick to what is known to be working: 1 single in tank pump, dual in tank pump, or high flow pump > surge tank > high pressure pump.
Having ideas is fun, making things work is better.

[2muchboost]

Croustibat Haha nicely put. Me over thinking is the engineering part of me and since I had never really brainstormed the fuel system much (I have a design laid out which is a sure thing based on others I have seen running somewhat high powered 2js). This is what happens when my brain gets in the way lol. But honestly, thanks again to all for the learning experience.

Breitling You def get a +1000 on the COOL FACTOR for a unique setup. The same reasons and idea that you had about a happy medium between mpg economy/drive-ability and top end power is what got my hamster wheel turning.

[Croustibat]

The thing is, there is no mpg to gain / lose in fuel delivery system. Think of your fuel system as the power supply of your computer. If your power supply has a 500W sticker on it, it means it CAN deliver up to 500W of combined power, but it wont deliver 500W unless asked for.

Your fuel system works the same. You have to deliver (approx) 1g of fuel for every 11 to 15g of air, always.

2 things dictate fuel consumption:

1/ engine efficiency, which you cant do anything about as increase in performance quite always decrease it (high octane fuel allows higher compression ratio, which increase efficiency, but as soon as you start to use bigger turbos, you need to lower the comp ratio to relieve stress from engine, not just remove DET)

2/ quantity of air going through it.

The 2/ is what your throttle is for, and is the best way to get better mpg.

There is a little gain to get in mpg while having a perfect mapping and best VE at cruising speed, the latter being obtained with an oem set of cams - which also means you wont be able to get the best of a high flowing turbo. As always, there is a trade off ( variable cam timing allows a better VE though )

But no gain from fuel supply, you either have the capacity to fuel or you dont, and if you dont ... well you can try with your computer, it will be less expensive to fix.

[2muchboost]

Im sure my builder/tuner would have slapped me back into common sense if he felt that my idea is dumb lol. I havent even run this idea by him because I can already imagine his face if I did. This is why I would rather ask here and learn before bringing dumb ideas his way.

[Croustibat]

It is not completely pointless, and it has an awesome cool factor. But it is completely overkill for a sub 1000HP setup, even more since you can now get very big injectors with around 1ms opening time.

Going dual manageable fuel pump is somewhat pointless though, and the guys who will have to map it will surely kill you for that :D

[2muchboost]

Lol so the bitch slap is heading my way anyways....here we go.