Gauge

iTrader: (3)

Hey all,

I've got a new D1-SC setup running 650RWHP @ 13psi of boost. This setup has far exceeded my expectations (I was looking for 575-600), so it's also far exceeded my fuel system. At 5500RPM or so, it's now losing fuel pressure.

I am currently running dual 255L Walbros, stock lines, stock regulator, stock rails, and 60# injectors. Another side issue is that I'm making 72-74psi of fuel pressure at idle. It does drop to 58psi pretty quickly, and then it's solid until about 5500RPMs. The tuner seems to have been able to work around that.

Now, I'm more than happy to pulley up and tame the car down a bit in order to make things safe and save some money. However, if the fuel fix is easy and relatively cheap, I'll keep the power.

I've read a lot on here where people have taken the dual Walbro setup way beyond what I'm doing. So, I'm assuming that I'm not running out of fuel pump. I'm guessing this has something to do with either line restriction, the fact that regulator is so close to the tank, or both. What's my next step? Should I get a front mounted FPR, run a return, and then see if the issue persists?

If I'm going to have to change everything (feed line, front mount regulator, rails, etc), then I'd rather just pulley up and avoid the hassel.

Ryan K

iTrader: (11)

I would try the front mounted FPR/return line first. You hit the nail on the head.

Gauge

iTrader: (3)

Thanks for the response, Ryan. I have a couple questions about the FPR installation:

1) I currently have this with my fuel pressure sending unit screwed into it:

http://www.nitrousoutlet.com/catalog...roduct_id=2717

Is there a FPR you guys would recommend that would go on the end of that fitting (the -4AN male on the end, which I currently have capped)? Or, will I need to get an adapter? Most of the FPRs I'm seeing on Summit have either -6an or -8an inlets.

2) When I run the return line, what type of fitting do I need to plug in to the rubber line coming down the front of the tank?

3) Do I need to remove the stock regulator from the tank? I'm assuming that I won't want two regulators in series like that.

donnyshane69

iTrader: (8)

I need to Know about the regulator in the tank and the line outside that (T's) back to it. How do you bypass them or remove them?
Thanks for this thread. I was looking for the same answers.

98Camarod

iTrader: (43)

If you put a regulator on, you need to remove the one in the tank.

I'm looking for some answers also. I don't have fuel pressure. I started my own thread, we will see if we get some replies, I've got a 98 so mines a little different.

donnyshane69

iTrader: (8)

Thanks for the reply. Mine is a 98 to. I'll keep watching.

Gauge

iTrader: (3)

donny,

In order to bypass the stock return setup, you just remove that line coming from the T fitting going back to the tank and plug the T. It's an NPT fitting of some sort, but I don't know the size for sure. A quick search will probably reveal that answer.

Based on what 98Camarod is saying, the regulator in the tank has to be removed as well (which makes sense). It's in the bucket, so it should be pretty straight-forward to get rid of it.

My main question is what fitting you need to put on your new return line so it will connect to the line going up to the top of the tank.

donnyshane69

iTrader: (8)

That is what I was looking for. Thanks. I am going to use my evap line as the return so I'm hooking up upfront.

98Camarod

iTrader: (43)

So you will be doing what I'm doing.

I'm pretty sure what you are looking for is a -6 gm quick disconnect

Gauge

iTrader: (3)

It's brand-specific? Will I be able to find a fitting like this that will connect to some cheap-o fuel line from Auto Zone?

98Camarod

iTrader: (43)

I found it on ebay, speed inc sells them:

http://cgi.ebay.com/ebaymotors/LS1-L...Q5fAccessories

Gauge

iTrader: (3)

Well, I now have a frount mounted regulator on the rail and a new return line. The car made 647RWHP at 14psi, and the fuel pressure dropped to 52psi and the AFR is 11.8:1. Now, the tuner says this is borderline, but I thought a pressure drop like that was a real serious issue. Is it not? They also mentioned that the injectors are at 96% duty cycle.

What's next? Are the pumps not up to the task, or do you think the line is becoming a restriction? The tuner is suggesting a boost-a-pump, but I refuse to use a bullshit bandaid fix like that.

Packy

iTrader: (11)

What is your static fuel pressure now with the FPR at the rail and do you have it boost referenced? With a front mounted regulator you should be running around 60-65psi static and when under boost your fuel pressure should go up 1psi for every pound of boost you are running if it is boost referenced. Your fuel set-up looks like it should support up to 650-700 rwhp. A boost-a-pump is not a band aid fix they really work well. Also you may want to look into Methanol injection.

98Camarod

iTrader: (43)

How do you figure it will drop? Mine is 58 psi steady throughout the power band.

What is your fuel system like gauge as far as fuel pump feed and return. If your injectors are at 96% you need some injectors either way. What size do you have now?

Packy

iTrader: (11)

I never said it would drop. If anything it should rise while under boost if it is boost referenced. His sig says he has Mototron 60's which at 65psi are more like 65 lb/hr injectors.

98Camarod

iTrader: (43)

I miss read what you said, but either way, how would it increase when its set for a certain fuel pressure while being boost referenced?

Gauge

iTrader: (3)

The regulator can be boost referenced, but I don't have a vacuum line connected to it because I figured a steady 60lbs of pressure (which is where it is at) would be fine. As 98Camarod pointed out, I don't imagine the pressure will rise when boost referenced if it's already falling at a static 60lb setting.

I'm running dual Walbro 255's with a T-block from Home Depot (too cheap for the Y-block), stock feed, stock rails, Edelbrock fuel pressure regulator, 60# Mototron injectors, and a 6AN return line.

I've seen the dual Walbro setup support a lot more power than I'm putting down, so I'm hoping it's not the pumps. I figured the issue before was that the stock regulator was keeping the pressure up near the tank but it was falling at the rails. I've dispelled that with the addition of the front mounted fuel pressure regulator. That tells me that it's either the plumbing (the T-block or the size of the stock feed), or the pumps really aren't up to the task.

I've also seen 60# injectors do a lot more than what I'm doing. I'm assuming that if the fuel pressure stayed at 60lbs, or if it rose to say 65-70psi with boost referencing, the injectors would be okay.

About all I'm willing to do now is to put in a new, bigger feed and possibly some new rails. I'm not willing to drop the cash on new injectors or pumps. If that's necessary, I'll just pulley up.

Packy

iTrader: (11)

You removed your stock intank regulator correct?

You need to boost reference the fuel regulator and see what that does for you. Most regulators boost reference on a 1:1 ratio which means if you run 60psi static fuel pressure and you make 12 psi of boost then your fuel pressure will rise 1psi per 1 psi of boost. So your fuel pressure should climb to 72psi when at WOT.

I have also seen people just turn their regulator up to 75 psi and have it tuned to run like that. I would rather boost reference it though so you are near stock pressure and then while at WOT you rise to the pressure to make you not run lean.

Gauge

iTrader: (3)

All a regulator does is bleed off excess fuel pressure to keep it down to the set pressure (60psi in my case). If it's falling to 52psi at redline, then the regulator isn't bleeding the pressure off, and boost referencing it shouldn't have any impact... correct?

Packy

iTrader: (11)

Yes, but what is happening is when you are under boost your tune is compensating by adding more fuel via your injectors which in turn is decreasing the psi in your lines/rails. Your regulator when boost referenced will compensate for this drop by adding more pressure while the boost rises on a 1:1 ratio.