Downzero

I would appreciate it if you guys would look at my data logs from today. I borrowed a wideband O2 from my friend and so it is included. My VSS isn't hooked up.

My truck isn't even remotely close to street legal so it's really hard to get data. I can't take it out on the road and log too much, and so it's been a real bear to get i tuned.

It does run a lot better. I've been doing a lot of VE tuning.

I am running a TPI pump (Airtex E3210) at about 30 psi, BPC is set at 109 with 55# injectors. I put the fuel pressure gauge on with it running, and the fuel pressure drops quite a bit if I rev the engine. Is this normal? How much should it drop? The pump and fuel filter are new.

I've managed to tune out all of the lean pops, but as you'll be able to tell from the logs, there are places in the VE tables where it still falls flat on its face, especially the high load areas. I may also bump up the fuel pressure a bit more because some of my VE numbers are over 90%. I'm starting to wonder if my injectors are flowing as much fuel as they're supposed to because according to RBob's utility, my engine should be able to make over 300 HP on the fuel these injectors can flow at the pressure they're set at, and my high VE numbers are in the 1600-2000 RPM range at relatively low loads (35-40 kpa). I do have another pair of injectors I could swap in, but the ones I have are actually putting out a nice cone shaped pattern so I'm reluctant to conclude that they're messed up.

I also haven't touched the SA tables at all yet.

Engine is a 383 stroker, Dart Iron Eagle 180cc heads, 9.6:1 CR.

I am fairly certain that this is my camshaft:
http://www.jegs.com/i/Comp%20Cams/249/12-365-4/10002/-1?sendroicid=bbef8492-2d00-41d6-b158-38db0de2603c&catargetid=1716046196&sendroikwd={keyword}&gclid=CMX9uIzWw7QCFelDMgodCyIABA

It's 216/223 @ .050", 113 LSA.

Any suggestions would be appreciated (or if additional info is necessary, please let me know).

Downzero

And the other log from today (oops, sorry, it's over 1 mb)

RBob

iTrader: (1)

Shouldn't drop at all, fuel pressure has to be rock solid (when not using a VRFPR).

Once you correct the fuel delivery issue the engine is going to be rich in all of those areas where the pressure is dropping off. With AE likely being very rich.

RBob.

Downzero

I'm not really sure what to do about that. It's a TPI pump, it's less than 2 weeks old, and the filter is new. What could cause it to not be able to push enough fuel?

I can crank the pressure up more (and the pump will make more pressure), but what can I do to keep the fuel pressure from dropping?

RBob

iTrader: (1)

Two most common issues is a leak in the tank caused by the hose between the pump & outlet line. And a crimped or clogged return line.

The FPR is not vacuum referenced, correct?

RBob.

Downzero

I just replaced the hose in the tank with a piece of Gates immersion hose that fits very tight and has hose clamps on it, so I'm fairly certain that it's not leaking. (Cranking up the fuel pressure regulator, I saw it spike to up to 60 psi, so if there was a leak, I'd think that'd not be happening).

I will try to blow out the return line today. I do know that I'm getting fuel flow back to the tank as I used the return line to drain the tank (truck was sitting for quite a while and I wanted to get fresh gas in it).

Is it possible that the spring is weak or something in the regulator? The regulator is not vacuum adjustable, it's just an adjustable from Turbo City or Jet (I can't remember which; I think the former).

Downzero

Blew out return line, it was fine.

Took apart throttle body looking for any trash that might have been in the fuel path or damages to the fuel pressure regulator; found nothing. The fuel pressure regulator spring is super stiff and seems fine.

Replaced fuel pump again, no change. Fuel pressure drops to 15-20 psi or so when I rev the engine. I'm starting to wonder if either the fuel pressure gauge is bad, or if it's simply not reading accurately because of where it is placed in the fuel line (at the throttle body supply).

I'm really at a loss. Also, the wideband doesn't report a lean mixture when the throttle is opened. the fuel pressure drops on the gauge from 30 psi to 15, and yet, the engine doesn't go lean. I'd normally never tell someone not to trust an instrument, but what should I think when the fuel delivery appears fine, the engine runs fine and doesn't go lean, yet the gauge says that the fuel pressure is dropping?

RBob

iTrader: (1)

I doubt it is a bad gauge. They usually either don't move (jammed) or read off. It likely isn't showing lean as you tuned it for the pressure drop.

At the TB supply is the correct location for the gauge. This is the drivers side, larger of the two lines.

Few more things to check, voltage at the pump. Make sure that it is close to the vehicle voltage. Bulk head connector on sending unit. These are known to go bad and severely reduce the voltage going to the pump.

Back off the regulator, make sure that it can go as low as 20 psi while being regulated. This is to verify that the spring is being compressed some. Not right on the edge of being compressed.

Does the FPR have a vacuum port to the inside area of the TB? Some do, and a restriction in the air intake/cleaner can cause the fuel pressure to drop.

This issue needs to be corrected, otherwise the tune will not work out.

RBob.

Downzero

The fuel pump in this vehicle is wired directly to the ignition switch. I will double check the voltage right at the connector to make sure it is the full battery voltage.

With the regulator backed off, the fuel pressure can go as low as 15 psi or so, and up to 70+ psi if one pinches the return line or cranks up the regulator.

FPR looks like this:
http://www.autosportcatalog.com/part...FexAMgodlxYA4w

And does not have any vacuum reference at all.

Maybe I should put an old .bin in it and see if it will show lean when I rev the engine.

The strange thing is, no matter how high the pressure is, it still drops. If I crank it up to 50 psi and start the engine and rev it up, it drops. If I crank it down to 20 and rev the engine, it drops.

Key on engine off, I set it at 32 psi.

Key on engine running, needle bounces around 34-36 psi.

Free rev, drops to 20.

And you're right, if I can't figure this out, it'll never be right.

Downzero

Went out to check voltages and opened a can of worms!

The wire for the fuel pump was rubbing on the braided fuel lines near the engine. It was nasty and corroded. Chopped out that piece of wire and soldered in a nice new piece and pump voltage went from 10.5 volts to battery voltage (~12.5).

I also attached a ground wire to the sending unit on the tank.

It's running to warm up now and I'm data logging; I assume that with the proper pump voltage, my fuel delivery issues are solved.

To those of you reading this, let this be a lesson to not assume the worst and make sure you check the basics, even if it might seem unlikely. That wire that was all chewed up would have been easily checked prior to all the tuning I did with a basically dead fuel pump.

I will have to check the fuel pressure but I suspect that at least this problem is solved.

Downzero

Still dropping on the gauge as of today. I'm at a loss; it appears I've checked everything.

If I open the throttle, fuel pressure drops to about 20 psi and quickly recovers to the low 30s.

Talked to Airtex tech support and he said that this pump should produce plenty of volume.

RBob

iTrader: (1)

This puzzles me a bit. There needs to be a reference port on the FPR. And needs to be open into the top area of the TBI unit. The backside of the diaphragm requires this to operate correctly.

This is so that the FPR is referenced to the same pressure that the injector outlets are exposed to.

If there is no vent, or if it is vented in the area of the adjustment screw, the FPR won't operate correctly.

You may need to drill a small hole into the side of the FPR.

RBob.

Downzero

I just got off the phone with Turbo City, who told me that there's no way this regulator with a stock spring will have any ability to keep the fuel pressure that high. They said that their fuel pressure regulator was made to vary the stock pressure by a few PSI, but that 30 psi is beyond that which it can regulate. A lot of things are starting to make sense now, if he is right. I have checked everything imaginable in my fuel system, replaced my flexible lines at the TBI with AN lines.

Tuned Performance

iTrader: (92)

sounds like you will need to make a block off plate and use a external regulator.

Downzero

Yep. I'm plumbing an Aeromotive adjustable fpr right now.

I guess I'll have a vacuum referenced FRP now.

And it wasn't cheap!

Downzero

Problem solved (at least this one). Tough lesson learned: don't bother with that adjustable FPR that fits in the throttle body unless all you need is a minor increase in fuel pressure.

I put a stock fuel pressure regulator in my throttle body for now and am using the Aeromotive 13301 fuel pressure regulator in my return line. It holds a consistent 30+ psi of fuel pressure now.

I may make a block-off plate for the factory FPR later if there's any significant benefit. For now, I no longer have to rely on that crappy spring that GM thought was a fuel pressure regulator.

Now that my fuel issues are solved, hopefully my future tuning will be more productive.

I haven't hooked the vaccum line to this fuel pressure regulator, but I may do that before I dial in the tune, although mine seems to idle fine at 30 PSI and 3-4% duty cycle on the injectors.

Once I got the idle mixture tuned with a few VE learns, it really idles nice and rock solid.

RBob

iTrader: (1)

Good deal getting it going. Tuning will go a lot better now. It will likely be rich in many areas now that the fuel pressure is stable. Your posts in the EBL tuning thread outlined a lot of going lean and popping out the TB.

I like to use a block off plate as that eliminates a failure point of the stock diaphragm possible breaking or leaking.

Connecting the vacuum line to the FPR helps in making the engine run smoother. I was surprised at the difference between using a VRFPR and not having it vacuum referenced.

Be sure to change the BPC vs VAC table when you connect the vacuum line. Use the base 30 psi in the EBL Utility when entering the values.

RBob.

Downzero

I went back to an earlier ve table so that it doesn't drown in fuel.

I am going to hook up a vacuum line before any further tuning and change that bpc vs vac variable.

I will make a block off plate next just to eliminate the stock regulator. Hopefully I can sell my turbo city regulator to someone who needs it to offset some of the cost of the Aeromotive. By the way, I used Aeromitive pn 13301, for anyone who searches for this later. The part number I posted previously was the wrong number.

Downzero

I have to thank RBob for all of his help. He really is a great resource for tuning advice.

I wish Fast355 was around as well, he really helped me a few years back.

I won't be doing any more tuning until my Spring break, but I'm so glad that after 5 days out in the 25 degree garage to get this fuel system figured out, that it's fixed. The truck runs and idles great with the vacuum referenced regulator and I am really looking forward to dialing it in better. I took it out for a spin around the block just to do some VE learns with the wideband, of course the VE tables aren't even close yet but the idle and off-idle is getting a lot better with some work.

Ronny

iTrader: (1)

Would it not be better to fab the block off plate accomodating the tangs for better sealing?

Downzero

That's what I plan on doing. I'm going to use my adjustable FPR as a template and drill the holes for the locating dowels and everything.

xch3no2

You can knock off the tiny posts for a slightly larger sealing surface. They become pointless at this build stage.
Working the return passage is important when the flow gets serious.