I've searched. Here and other forums, either my search filter isn't good, or I can't find a satisfactory answer.


If I need ~1600cc of fuel is it better to run a set of 1600cc injectors or run 850cc primary injectors with 850cc secondary injectors. All other variables will be the same. Engine management is via Hydra 2.6. TGV's are the APS units with provisions for secondary injectors built in.

Thanks for any useful help.

I'd run sequential injectors for better fuel atomization (assuming positioned well) and better low/no boost fuel control. You can actually gain some power by doing sequential injection.

1600cc is "like trying to fill a shotglass with a fire hose". ;)

orignally had 1300cc injectors and found that low down response was terrible. Was wasteing slot of fuel in the process only getting 100 km per tank when I gunned it.

I decided to go with 8 x wrx top feed recapped injectors which flow around 800cc. Being stock injectors the theory is the trims will be easier to control. One set will be used tip they are maxed out, then the secondaries will kick in when required.


This should dramatically improve fuel economy IMO. Got everything just waiting for installation. Should be done by chrissy. Cross the fingers.

i run 1600's on a hydra and as far as idle goes i ran a 800rpm idle just fine. the way i see it is when you buy the second rail, second fpr, all the lines, wire them in and get a tune it just not worth the effort to save a little gas. i guess i really never noticed the down low response problem. my 40r was at 23psi at 3900rpm and kicked on real hard. i thought it was just lag before that?

I'm not concerned with gas mileage this car will not be a DD. I won't have any added tuning cost as I'm going to choose a setup and go with it. I am still leaning more towards 8 850cc deatschwerks injectors vice 4 1600cc. It just seems like there will be WAY more fuel control with 8 injectors.

I'm also wondering if the over/under positioning of the APS tgv units is optimal, or if the secondaries should be directly on the top of the manifold firing straight down the runners.

The link below it to the build we are rapping up now. We are using PE 850cc injectors with the APS TGV deletes and Aux fuel rails running 650 secondary injectors. The only thing we had to change was the APS wiring that came with the secondary injectors. They come set up for batch fire. The Link ECU we are running can control all 8 individually so some re wiring had to be done.


http://fliblog.wordpress.com/2008/10/16/aps-tsr70-rfmic-06-sti/

If the car is not a daily driver, why not keep it simple and just run 1600cc injectors?

If the car is not a daily driver, why not keep it simple and just run 1600cc injectors?
cuz 2 sets will give you WAY more precise control over you fuel.

"1600cc is "like trying to fill a shotglass with a fire hose".

cuz 2 sets will give you WAY more precise control over you fuel.

"1600cc is "like trying to fill a shotglass with a fire hose".

That highly depends on the EMS being used. Phil has actually made a post somewhere about how well the Hydra deals with those injectors due to it's ability to adjust fueling at rather minute pulsewidths.

So is this a question I should be talking to Phil about?


Fine Line Imports: If I go with the 8 injector setup will I be able to purchase only parts of your setup or would I have to buy the whole thing and get rid of what I don't need?

ihadmail: its just using a APS TGV section, 4 more injectors, another set of rails, another fuel pressure reg and probably a fuel block before feed fuel is seperated between the rails...then use a y-block to join both FPR's return lines to a larger (-8AN should do) return line to the fuel tank.

Is there someplace that I can purchase that mounting bracket for the auxiliary fuel rails? I tried searching google and could only find that bracket with the kit. Im not the biggest fan of the APS rails and would like to use other rails instead, but I need that bracket. :confused:


I'm sorry for asking so many n00b questions, but I would rather ask than waste money by screwing it up.

hear is a pic of my setup:
http://i30.photobucket.com/albums/c301/fobiawrx/s374turbo099.jpg

used areomotive rails and made my own brackets to mount them to the tgv. its really easy just to make it your self. i did use the asp fuel block though and modded it to use a -10 feed. and if you plan on making your setup like i did, prepare for spending lots of $$$$ for lines and fittings

Thanks for all of your help fobia! your build is looking pretty sick right now too. I have already planned to have tons of cost on lines and fittings. I am contemplating a dry sump setup which will triple my line and fitting costs.

im looking at over 3000$ on lines and fittings. its retarded how much they cost.

im looking at over 3000$ on lines and fittings. its retarded how much they cost.




:eek::eek::eek:

Holy crap!! What kinda power are we talkin that justifys 1600cc of fuel? 500 whp+? Sick setup man, I'm super jealous. Those areomotive rails are sick, I was thinkin about grabin a set for my more modest single injector setup.

Fobia..


What size fuel line are u using from the petrol tank??

I was only going to go with one FPR as im only running standard fuel lines atm.. My tuner told me that running two FPRs will cause issues with cross talk between the FPRs??

i haven't ran the secondary set of 1600cc injectors yet because i was on the stock block last season, but on every twin rail setup i have seen in action, they all used two fpr.

im running a -10 feed which splits to 4 -6 lines to the rails. then -8 as the return.

Fair enough.. I think im going to end up going a similar setup as yourself now..

Just need to make a plate to bolt everything to..

When you have a single feed line coming from the tank going into your fuel distribution block which supplies fuel to all 4 rails will the secondary rails have any issues with fuel pressure as they are not being turned on until it sees "X" amount of boost. So that mean the secondary FPR has to return 100% of the fuel back to the return line. Hope that makes sense what I am trying to say haha.

With 2 regulators, you actually reduce the amount of fuel they need to flow as the load is shared. Also remember that at idle, the regulator(s) are already bypassing almost all of the fuel.

Let me ask this to those guys running the secondary injector setup...I really wanna get better gas mileage around town and a little more on the highway. I have DW 850cc injectors right now and looking to do aps deletes with stock wrx or sti pinks with the bosch style 850cc on top. Would this be a do-able setup? Would it work? I currently have the raw signature series motor (sleeved) and 280 cams with gt35r. thanks

Let me ask this to those guys running the secondary injector setup...I really wanna get better gas mileage around town and a little more on the highway. I have DW 850cc injectors right now and looking to do aps deletes with stock wrx or sti pinks with the bosch style 850cc on top. Would this be a do-able setup? Would it work? I currently have the raw signature series motor (sleeved) and 280 cams with gt35r. thanks

I hate to say it, but with those cams, you definitely won't be getting far between gas stations, especially in town.

You need to run a good bit richer than usual to get such a high-strung motor to run smoothly downstairs, which is where all your fuel is currently going.. It won't happily run the same AFR's your stock motor did. Price of cams really..bad fuel mileage being one of them.

Your fuel system isn't the issue.. It's a side effect of your choice of cams.

Let me ask this to those guys running teh secondary injector setup...I really wanna get better gas mileage around town and a little more on teh highway. I have DW 850cc injectors right now and looking to do aps deletes with stock wrx or sti pinks with teh bosch style 850cc on top. Would this be a do-able setup? Would it work? I currently have teh raw signature series motor (sleeved) and 280 cams with gt35r. thanks

I went from ultimate racing 1260cc injectors to 8x wrx decaps. And on a rough tune im getting nearly 100 kms extra per tank. i.e around 250kms compared to around 150km with the single big injectors. So yes there is a great improvement and i think we can make it better when i get my tune sorted out..

I would stick with one brand right through rather than two different sets of injectors this will make it easier to tune..

We are big fans of dual injectors on tehse high powered Subi engines:

- Over-all better control of teh fuel delivery. Yes, this can mean better gas mileage but we believe u get better throttle response as well. Especially off idle.

- Most modern stand-alone ECUs can now control tehse. teh AEM unit we currently have in a project has multiple ways to control teh secondary injectors: batch firing, secondary's kick in when primaries hit a determined duty cycle, secondary's kick-in at certain loads, etc. u can tune teh ECU to only go with teh secondary's once needed i.e.. as boost comes on. Also, teh AEM unit allows u to run different size primaries vs. teh secondary's via a scaling factor u input in when u describe teh secondary's in teh software. So u could run some nice responsive 440cc as primaries and tehn have some 560cc as teh secondary's.

- Less chance of starving a fuel rail. Typically a duel system will have two rails, thus doubling teh fuel volume at teh injectors.

- Lower cost for injectors. u can buy (8) 550cc for less tehn buying (4) 1100cc injectors.

tehre are some down sides of course:

- More overall project costs. Need a lower manifold boss to accept dual injectors and tehn all teh extra plumbing.

- More complexity and programming.

Keep in mind we feel quite a few fuel systems out tehre are under injected. If u run some debatable math u will c tehse are teh injector sizes u need for tehse HP engines:

• 400 Hp – u need 790 cc/min injectors
• 500 Hp – u need 990 cc/min injectors
• 600 Hp – u need 1120 cc/min injectors

Do u have enough? Duel injectors might be teh solution.

http://www.forsaindustries.com/images/Special_post_pictures/Forsa Dual Fuel.JPG

Thanks Tino and Bishop, I have the hydra 2.6...i know with the cams it asks for more fuel, but around town and such just is plain silly with fuel consumption. I'm looking at 1260cc in total max.

- Less chance of starving a fuel rail. Typically a duel system will have two rails, thus doubling teh fuel volume at teh injectors.



While theoretcal, I'm not sure how true this is to actually happen. You would need to have a natural deficit in the flow volumn from your pump. As well, the FPR after the fuel rails means that for sudden changes in fuel use (not common on a turbo application) the FPR would see the pressure drop first.


- Lower cost for injectors. u can buy (8) 550cc for less tehn buying (4) 1100cc injectors.


I'm not sure that is true either. Consider the Bosch 1000cc injectors running at say 70psi base fuel pressure. Cost is $500.


tehre are some down sides of course:
- More overall project costs. Need a lower manifold boss to accept dual injectors and tehn all teh extra plumbing.
- More complexity and programming.


Agreed.


Keep in mind we feel quite a few fuel systems out tehre are under injected. If u run some debatable math u will c tehse are teh injector sizes u need for tehse HP engines:

• 400 Hp – u need 790 cc/min injectors
• 500 Hp – u need 990 cc/min injectors
• 600 Hp – u need 1120 cc/min injectors

Do u have enough? Duel injectors might be teh solution.


What do you mean by 'under injected'? Either the car can maintain the AFRs needed or not. If you are talking dynamic enrichment due to rapid changes, that is a different story.

HP to CC's is a nearly useless metric without much greater details (fuel types, BSFC, etc)

Jeff

other than the APS tvg's how else can duals rails be added to a top feed STI motor?

you can buy injector bungs and weld them on. atp has them

I still don't know why people insist on running dual stage injectors and then don't mount the 2nd stage high in the runner. If you are going to the added expense and hassle of the 2nd stage, please put them in the top of the radius of the intake runner. You are making the setup much more complex without adding anything (by putting them in the TGV). Move the 2nd stage deep into the runner and gain some HP from the added mixing time. Cossie Convert is the only one I've seen here to realize this, and he happens to run 9s on much less turbo than anyone else in the 9s. There is a reason F1 injects outside of the throttles and intakes with their high mount injectors.

These dual stage TGV housings are best replaced with 1600cc injectors, or see above comments. IMO all above pics posted were a big waste of $$.

I still don't know why people insist on running dual stage injectors and then don't mount the 2nd stage high in the runner. If you are going to the added expense and hassle of the 2nd stage, please put them in the top of the radius of the intake runner. You are making the setup much more complex without adding anything (by putting them in the TGV). Move the 2nd stage deep into the runner and gain some HP from the added mixing time. Cossie Convert is the only one I've seen here to realize this, and he happens to run 9s on much less turbo than anyone else in the 9s. There is a reason F1 injects outside of the throttles and intakes with their high mount injectors.

These dual stage TGV housings are best replaced with 1600cc injectors, or see above comments. IMO all above pics posted were a big waste of $$.

Do you have any pics of what you are recommending?

http://i22.photobucket.com/albums/b318/tokennegro/Forsale/IMG_1765.jpg

A littel below what hes talking about but thats the idea.

Wow, that is sweet.. what fuel pump and how much fuel pressure does that setup run?