Why is it neccesary to have the 1:1 fpr? If you use stock injectors for primaries wouldn't the stock fpr do the trick? I think I am missing a key point of the fpr. Does the fpr just keep pressure constant in the two rails? I'm going to be using the HKS AIC III, I've seen it setup with no fpr before, but maybe it was because the rails are not in series. Any help on understanding this would be appreciated.

you need a 1:1 because you need to keep fuel that comes out of the injectors, at a constant flow rate. You have to remember that fuel is under pressure, and also under boost, you have pressure in the manifold, and pressure acting on the injector outlets. If fuel pressure was constant, then once your boost pressure increases, the increased pressure would start to limit flow from the injector, UNLESS you increase the fuel pressure at the injector, one psi fuel, for one psi boost increase. Hopefully that makes sense.

It makes sense yeah, what is the best 1:1 to use. The one in corbins setup

Originally posted by safedawg
It makes sense yeah, what is the best 1:1 to use. The one in corbins setup

"Best" is hard to define. But I use the Aeromotive(IIRC) FPR as many others. Any 1:1 boost referenced FPR should work. But please be aware that with a high performance fuel pump, such as a Walbro 255, any ordinary or stock FPR may be overran if the fuel pump overpowers it.

The only thing I did was tap the extra fuel rail into the supply line tha goes to the stock fuel rail. I'm using the stock fpr and works fine. No other modification was needed. My fuel gauge read at idle 33-35psi, under boost it goes up to like 50psi.

Do you have a 95 fuel rail with its corresponding FPR?

Yes, I didn't touch the stock fuel system for nothing. I only tap into the supply line. The extra fuel rail I have is from a GST complete with fpr, I added a cap on it. It works as if the fpr is capped at the end.

That is what I thought we could do. Do you just have the stock fpr in-line with the stock return? Do you have the rails in parallel then? If you could e-mail me or post how you have yours setup I would appreciate it. It would make this much easier, my setup will be a lot like yours.

Originally posted by safedawg
That is what I thought we could do. Do you just have the stock fpr in-line with the stock return? Do you have the rails in parallel then? If you could e-mail me or post how you have yours setup I would appreciate it. It would make this much easier, my setup will be a lot like yours.

Yes, I have the stock fpr in line with the stock return, I didn't touch it. And No, I just tap a tee into the supply line, after the fuel filter and connect the extra fuel rail. One end of the fuel rail has the fuel line and the other is capped. I Will try to post some pictures. For how much did you get the AIC III, they go new for around $900.00

I got the AIC III from ebay, and all I have to say is e-bay is awesome. You can come around them pretty cheap. Thanks for the help, this setup seems complicated at first, but once you get things figured out its pretty simple. I hope I can get it tuned well.

Edit: I actually have another question. what do I do with the return line that I had setup for the s-fmu. Would I just cap both rails at the ends? If I got rid of the return line, where would the stock fpr go? I had the later model fuel system.

Great deal! I also got mine from e-bay. I got the old unit and let me tell you, after I tuned the car, is the best modification to the car ever. You will not believe the advantage with this system. Now just raise the boost, because you have plenty of fuel.

The only thing with my set-up is that I have plenty of fuel, but a small turbo and stock engine. Now I will start saving for new internals and rebuild kit for my 16G. Or should I get a t3/t4?

I would just get another t3/t4, or t04e. So just to clarify, what did you do with your return lines, did you have the returnless fuel system?

Another issue, is it not possible to place 2 large injectors before the throttle body, much like a wet nitrous system. I cannot see a reason why this can't be done. I figure that the air is moving at such a velocity that the placement of the injectors really does not matter. The fuel in my opinion would get evenly distributed into the manifold with the forced air. Is this possible, or is this just a problem waiting to happen? Could you do this? Wouldn't there have to be an absolutly leak free seal prior to the throttle body.

I have the return line system.

If you are going with the 8-injector set-up, there is no need for the other two injectors. You can do it, but thre is no need. Before I finished my set-up, I had one injector in the ic piping before the throttle boby. I had better response with the 8-injector set-up.

I'd be a little leary of not using a 1:1 with a boosted app, even though it works. Lets see if I can clarify a bit..

Lets theoretically say you have 400cc injectors, which can spray 400cc's of fuel at 45 psi fuel pressure. Now, when we put boost pressure in the manifold, that pressure acts upon the fuel injector, and lets say we are running 10 psi. So now, the differential pressure accross the injector is 35 psi. You will NOT get 400cc's of fuel now at 35 psi. Maybe thats a better explanation. Using the 034 to add fuel in this situation, helps, because if you don't use a 1:1, you can program in the extra injector pulse width needed to compensate for the pressure differential at the injector, but IMO, I would want a constant pressure/flow rate from the injector using a 1:1 regulator. Its just the *proper* way to do it. I also use an Aeromotive 1:1, its small, extremely good quality, has 2 ports on it, and a top adjustment bolt for your idle fuel pressure. Its pretty cheap too, at around 140-150 bucks. The biggest concern when not using a 1:1, would be using injectors that are not large enough for the application, or just big enough for your power level. If you run injectors that are theoretically *just* large enough when used with a 1:1 regulator, there would NOT be enough fuel flow if you did not use a 1:1.

Lets say you want to run 20 psi of boost, and run a 45 psi idle fuel pressure. Well now, at 20 psi boost, you only have 25 psi of fuel flow coming out your injectors..thats bad, and is why you should use a 1:1 FPR

I agree, Matt.

I do think thouch that "customrsturbo" is indicating through his posted fuel pressures that the 95 return lined FPR is boost referenced at about 1:1 ratio. That doesn't really surpris me given those FPR's look very similar, at least to me, to stock turbo fpr's.

Yeah, the stock regulator is 1:1. I guess what I think is interesting about it is that it seems to work as well in boost as it does in vaccuum. I wonder how much boost it can take before it bursts or looses pressure control. :shrug


95 Eclipse RS : 5 speed
15.7 @ 87.9mph
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

I know that stock 4g63 guys have issues with their stock fpr's not able to maintain pressures, especially static, when using a high pressure fuel pump. That's one of the main reasons they have to upgrade.

Yeah, I guess thats what I am trying to get at, is that I would not trust the stock FPR in a boosted application, even though it may *work*. Its not like it costs an arm and a leg for good, reliable, well made FPR such as the Aeromotive, and that alone can give you peace of mind..ehh that's just me though :)

I understand the point that you all want to make. As for now I haven't had any problem with my set-up. Even, it was too easy to make the 8-injector setup with the less money spend and I'm running rich for safe issues. I am even running on the stock fuel pressure and haven't had any problems. I drive the car daily and boosting even 15psi in some ocasions two to three times a day. I just try to take an idea from the theory and an put it to practice. If I had the money I will replace the entire fuel system, bottom end, etc. But as a family man, other expenses are more important. I just try to have fun with this hobby & my kids, and try different ideas with the less money involved. This is why I'm planning on only buying just low compression pistons and use the stock rods. I have read some post and people had done it, even running 20 psi. I know this will be bad idea for some of you, but $ is limited. Also, you have to know when to reach to a point and don't push the envelope when pushing your engine. I hope nobody gets offended, this is not my intention and I am not mad at anybody. I just try to be different and try my own methods based on this forum with a lot of information and everybody experience.

^^ wouldnt a turbododge t03 fit your setup better? i mean, iirc, it has hte same flange as your teo4h

Yes I thought of that, but I got a 16g for free. I will have to work on another turbo manifold and downpipe. So I'm still don't know wich one. Either one is a good choice. Obviusly, the t3 will fit with no other modification. So I will see what happends.

Sorry to bring this bck up, but what did you do with a return line for the secondary fuel rail? Does it have a return, did you just t-off of the factory supply line? Thanks.

No, I just put a cap on the return port and don't put any vaccum line neither. The fpr from the secoundary fuel rail will work now as a cap only. Or you can fabricate the cap, for me is not necessary.

Be careful with the stock rods brother, the highest I have heard them lasting is 13-14psi. You may also want to look at the cost of just buying the rods the first time vs. the cost of tearing the engine down again to rebuild it when they fail... not a sermon, just a thought...

Yeah, I know. You know what, I'm still not making my mind on this issue. I will make the desicion when a get the money in my hand. But thanks anyway.:thumbsup

I think I am going to attempt using just two injectors before the TB. They will be 550cc injectors, so plenty of fuel. Do you think this will be a problem, or will I be fine with this setup. I plan to just weld in two injector bosses not directly at each other, but close for better atomization, would it work ok?

Would two injectors right before the TB give you equal fuel distribution? The intake manifold is meant to flow air not and air/fuel mix. You might not get the best distribution and you might get some fuel puddling and evaporating effects during transition periods. People do it, but it doesn't sound like a great idea to me.

Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

Thats what I'm not sure about, supposedly you get better atomization if you place the injectors before the throttle body, it gives more time for the air and fuel to mix, but our manifolds are not designed to carry gas. I have seen this done before, and it seems to work for most who try it. Basically what it comes down to is money, I have everything i need to do just 2 injectors, and I also have everything I need to do 4 injectors, except drilling the mani. So at this point is seems a lot easier to drill the intake pipe than the mani. Either way I just need to get my car in running condition, I can probably do the 8-injector setup in a few months, but I need something to just get me running for a bit. I know customrsturbo said he had a single injector in the intake stream and didn't have problems, just not as responsive which seems kinda obvious.

Drilling the intake is not a big deal. The important part is marking the drill places and aligning the injector tubing. The intake layer is less than a 1/4" thick and been aluminum is easy to drill. It will give you greater response installing the injectors in the intake. I had some backfiring thru the intake when too much fuel was injected with only one injector on the ic piping. To keep driving your car, buy a second lower intake to work on it and then make the swap. Beleive in yourself!:thumbsup

I think I will most likely just drill the mani, I guess I got time to do it, my car isn't back together yet, any special technique to drilling. Should I make a jig, or just something to keep the drill straight, and what is the best kind of bit to use, and what size of bit is needed for the injector bosses?

use a punch to gently make dent so the bit will not wander when you start to drill.