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Discussion Starter #1
Hi

I was thinking to my self... (has a good beginning, dont it :D )

...on a singleturbo with stock fuel you can get about 550rwhp before you are maxing your stock fuel system.

If I would be on a budget, which would be the next thing to upgrade? Im talking after doing the FDBP-mod and AFPR.

What is the next bottleneck? The injectors? the pump? the rail or what?

How much can the rest of the fuel system support if I would just change the injectors to 720cc and keep everything else stock exept the AFPR and FDBP?

I was just wondering, I dont need an upgraded fuelsystem for a long time.

Krister
 

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A fellow SUpra owner in MD did just that a while back and I think he even had a VPC (but no S-AFC). What happens is that your ECU still thinks that you have 550cc injectors in instead of the 720cc. That mean that your duty cycle will remain the same with your 720's, and you will run dead rich. The person I'm thinking of couldn't lean his system out enough with his VPC, and needed something to fine tune the system for it to work. Not sure what the bottleneck after that would be, though. It's all pretty constrictive.

Eric

4 digit HP
 

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Discussion Starter #3
Oh sorry, I ment that I'd have a VPC+GCC combo to tune the bigger incjectors, my bad.

Krister
 

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rockin' the JDM duct tape
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i was under the impression that there weren't any injectors that fit the stock rail and wired up directly.
 

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You can run a new Fuel pump (Walboro) or bump up the voltage to the stock one. Then tap the stock rail and add a FPR, which should be good for 600rwhp if you bump up the base fuel pressure. If you want to go even further, add a 2nd line and a 2nd pump to the stock tapped rail. The only injectors for the stock rail are the Blitz side feeds, which are alot of money (~$150 each)
 

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Discussion Starter #6
OK... how much would the stock fuel lines support if i would only change the pump + fuel rail and injectors?

Krister
 

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Krister,

You may find that it's actually cheaper/easier to buy a used aftermarket system depending on who does the work for you. I have a good friend who built a modified rail (starting with stock) for cheap, but he did ALL the work himself. Additionally, he checks it for leaks all the time...so the hassle factor is kind of there, but it has been working very well. He purchased a stock rail and some spare stock injectors, but then had the injectors cleaned and flow tested (which isn't free) and bumped up his fuel pressure via a "Boost-a-pump" mod and also an adjustable FPR. I think he has under $350 into the project though, and the car could probably put down well over 550 rwhp safely (he hasn't taken it that high). Good luck!

Steve T.
 

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So, thinking along the same lines...I'm not after big power per se but already have an aftermarket pump (external) and big fuel lines with no fpd. This type of "poor mans" system has some appeal to me as well, but I want to make sure it can support my goals.

I'll be discussing with my friend who has built his already, but more feedback is always good. Anyway, here are my own goals assuming I go with this Frankenstein stock fuel system (funny, because my fuel system is ALREADY Frankenstein like):

1. Maintain stock ECU (currently using this, with S-AFC2, VPC, BCC)
2. Allow approximately 600 rwhp on dyno with elevated fuel pressure (via A-FPR) and my aforementioned aftermarket lines/pump. This will be with a PT63 (.68) turbo.
3. Allow for about 550 rwhp on the street/strip, leaving some margin for safety.

Assuming these goals are realistic and attainable, this type of system has some appeal to me. If you guys think this isn't likely (particularly the 600 rwhp dyno figure), please let me know. My goal is not to have this type of power on tap regularly, but I'd like to achieve it every now and again.

Going to the 850cc Blitz injectors would require at least a different VPC chip, but since HKS doesn't make a chip for that size, I'm guessing I'd have some strange fuel/driveability issues to deal with. An AEM (also not in my plans for now) would probably be the easiest way to deal with that. I'm also not entirely opposed to having the stock injectors bored out a bit (say to 580cc, but I know this is expensive as well). Doing too much to the stock system is obviously not a good thing either, as the money could be spent on a pure aftermarket setup.

Please shoot down my idea completely if it's not sound! I've already found a couple friends with stock rails and injectors that I'm thinking about picking up! ;)

Steve T.
 

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Discussion Starter #11 (Edited)
I'm not very familiar with these "an" measurements? I know 10an is bigger than 6an, but how much and what does this "an" actually even mean?

And has anyone just upgraded the injectors and left everything else stock besides a VPC/GCC combo? Or is this something one shouldnt do?

Krister

EDIT: Yes these are the same goals I'm looking for:
1. Maintain stock ECU (currently using this, with S-AFC2, VPC, BCC)
2. Allow approximately 600 rwhp on dyno with elevated fuel pressure (via A-FPR) and my aforementioned aftermarket lines/pump. This will be with a PT63 (.68) turbo.
3. Allow for about 550 rwhp on the street/strip, leaving some margin for safety.
 

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The ONLY KNOWN injectors that will fit the stock rail are the Blitz 850's. You will have trouble with them because HKS only makes a 720 chip I believe and it's gunna be hard to make them idle well and adjust them with the GCC.
 

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Why 850cc injectors Steve? It has been proven the stock 550cc injectors will flow 550hp.... do you really need to upgrade the whole way to 850's?

Perhaps 720's would be a better bet, which also the VPC with a different chip should be able to handle. 720cc injectors should be adequate for your target power. With other supporting fuel mods, I don't see you having any problems. With an upgraded pump, getting a fuel pressure regulator and bigger injectors, you shouldn't be too far away from your goal with some tuning. :cool::)

CraigK
 

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Craig,

850cc Blitz squirters are the only side feed injectors I know of. The 720cc injectors require an aftermarket rail...forcing me into a completely aftermarket setup.

Steve T.
 

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I misunderstood, I thought you were looking for overall options to building a bigger fuel system without actually buying a whole kit.
 

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Discussion Starter #16
Hmmm, couldnt you upgrade the rail + injectors and keep everything else stock? Or doesnt the stock fuel line fit the aftermarket rail?

Krister
 

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if you are going to go ahead and do the Rail and injectors, just spend a little more get another line and pump!
 
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Safety is defined as the ability to support max boost on your turbo IMO.

Assume the worst: A wastegate failure, EBC/MBC failure, vacuum line failure, etc...

Hell, when I installed my single, I forgot to set my HKS EVC to external wastegate and I boosted to over 25psi on a T78. Fortunately, I had my fuel controller set to add 15%+ fuel at high rpms so I was running rich (720's also). If I would of been on the stock fuel I could have easily popped my engine.

Be careful!
 

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Been there, done that, and lived through it (on stock fuel too). No fun at all!

Steve T.

stoker6 said:
...Hell, when I installed my single, I forgot to set my HKS EVC to external wastegate and I boosted to over 25psi on a T78...

Be careful!
 

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chnco said:
The ONLY KNOWN injectors that will fit the stock rail are the Blitz 850's. You will have trouble with them because HKS only makes a 720 chip I believe and it's gunna be hard to make them idle well and adjust them with the GCC.
When I had the VPC, there was no problem with idle at all.
 
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