Re: Question about fuel injection from a newbie
 

Talking about the MAP that I see in TunerCat showing the Fuel Curve

D

Re: Question about fuel injection from a newbie
 

That is a map. Not all caps.

Re: Question about fuel injection from a newbie
 

I wouldn't run anything bigger than a 30 lb injector on an LT1 Stocker. I actually had better results running Ford 24 lb injectors in my LT1s. I have had no issues ignoring the 80% rule. Also,any gain that you might see from running a smaller injector at a higher than rated pressure will occur down low. Otherwise, at WOT in third gear everything pretty much seems to work the same once the tune is good.

FYI, my 427 COPO was delivered with 42 lb injectors at 90 psi.

Ed is telling it true.

Re: Question about fuel injection from a newbie
 

You need to fix this first. There should not be the voltage drop that you have reported. You will burn something if you continue to run things with this problem.

I am assuming that you have your regulator plumbed after the fuel rails and that you are running a return line?

Re: Question about fuel injection from a newbie
 

I didn't think about him maybe having the regulator in the wrong place. HAS to be AFTER the fuel rails, controlling return only.

Surely his battery or batteries is/are in the trunk. I let my FAST ECU control my fuel pump relay, just like a factory vehicle. My relay is back there too. All 10 gauge wire from my batteries to the relay, then to the pump, and a ten gauge ground from the pump back to the battery's ground terminals. My batteries are grounded directly to the engine, with a long, large gauge ground cable. I have a ground cable to the body too. My battery cables have all terminals soldered on. I've logged my fuel pressure. Never changes. Solid at 60 psi.

Re: Question about fuel injection from a newbie
 

Why? Guess I will keep that little secret to myself then..........

Do some dyno testing the an ECM capable of certain things and you shall see........

I see there are a lot of know-it-alls here so I call it quits. Just trying to help the OP. I see he can listen to the other clowns.

Bye now.

Re: Question about fuel injection from a newbie
 

So, you are the expert? And the rest of us are clowns?

Why would you say that about people?

I simply asked why a B/SA car would need injectors that big.

Who are you?

I seriously doubt you have any "secrets" I need to know. LOL

Re: Question about fuel injection from a newbie
 

Not to kick the hornets nest, But
There is potential power to be gained by running over sized injectors.

I assume that CMRacing is referring to the possibility of Phasing the injector "Event" in relation to the intake valve opening and closing.

I have found some power doing this with the FAST XFI system, but I will tell you that there is no guarantee that you will find anything, and there is no set strategy that will work on every application.

If your intake duration is say, 288 degrees, that equals 40% of a complete engine cycle. So if your strategy is to only have the injector open while the intake valve is open, then you must keep your injector duty cycle equal to or less than 40%.

You may not make any more power this way than you do with smaller injectors at 80% duty cycle, but there is definitely the potential to!

As far as going over the recommended 80% duty cycle max, there are two good reasons not to do this.
One, many injectors are not linear above 80%, meaning that because of poor pintle control at high duty cycle, the pintle may never close at 80-85%. This means that at 80%, you may be getting 100% of the injectors flow potential, therefore, the ECU assumes that there is 20% more fuel that it can add that is not really there.
Two, if you have your engine tuned to run above 80% duty cycle, and you go somewhere where the air is really good, you could easily run out of injector.
The 80% rule of thumb is not there to keep from damaging the injectors or the ECU, it is to make sure that you don't get into a situation where the engine needs more fuel than the injectors can supply.
I am not bashing anyone who is running their injectors above 80%, just making those watching aware of the dangers.

Re: Question about fuel injection from a newbie
 

I haven't found conclusive proof of this, but your back to back test might. Even then, the results will only be relative to your engine and that injector.

That being said, I have never seen higher fuel pressure hurt performance so at worst, it is equal to lower pressure in terms of performance. All my statements here are assuming that you are making the proper corrections to your tune or calibration so that you are always delivering the same net amount of fuel, just one with lower pulsewidth / high pressure, the other with higher pulsewidth / low pressure.

Re: Question about fuel injection from a newbie
 

Thanks David. I appreciate your and everyone's help. I need all I can get.

Re: Question about fuel injection from a newbie
 

I don't run injectors at, or above 80% duty cycle. I do work with injector timing, or phasing. I like to end the injector pulse just before the intake valve closes.

Re: Question about fuel injection from a newbie
 

After testing Friday night I learned one thing for sure. My 4th gen f-bodies will not hook on just any track as I've been told. I made 7 runs and only hooked on three of them! As for fuel pressure test, as near as I can tell it made the et .02 quicker going from 45 lbs to 60 lbs fuel pressure. Another discovery I made....I normally launch with a 2 step. I normally run 124 mph. I tried footbraking and the et was the same but I went 127 mph. I also tried a footbrake pass the next day just to make sure and I went a high 126. I *think* it may be lean at launch on 2 step and it likes the additional fuel that it gets by footbraking. Sound right? I just don't understand the faster mph and no et change.

Re: Question about fuel injection from a newbie
 

I think you may read lean on the two step , because some of the fuel is not burned and allows O2 to pass through the engine . Does two stepping change the 60 ft time ?

Re: Question about fuel injection from a newbie
 

You can't tell anything about an O2 reading while on the 2 step. No 60' change. Only mph.

Re: Question about fuel injection from a newbie
 

The highest load and fuel demand during a run is when the car leaves and when it goes in to high gear.

Re: Question about fuel injection from a newbie
 

I will be tuning (richening) the launch area to see if I can get the same performance on the 2 step that I do footbraking.

Re: Question about fuel injection from a newbie
 

This is a smart preventative maintenance mod that is overlooked.

Our B-Body Impala/Caprice community also suffer from Fuel Pump Problems.
Key issue; GM used just enough gauge size for their Harnesses.

Over time you have dodgy fuel pumps, burned wires, corroded connectors and blown fuses.

Last week the Caprice Wagon Fuel Pump fussed at 240,000 miles.
Bought a Racetronic Harness a while back which has a larger gage wire.
Installed it with a new Delco Fuel Sending Unit and Fuel Pump.

All of a sudden the Fuel Gauge works properly again and drivability improved.

D