Question about fuel injection from a newbie - Page 5

Dan Fahey · 05-09-2017, 11:30 AM

Quote:

Originally Posted by Ed Wright

Wow! You have no clue. For one thing, MAP is Manifold Absolute Pressure.

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

D

Ed Wright · 05-09-2017, 11:32 AM

Quote:

Originally Posted by Dan Fahey

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

D

That is a map. Not all caps.

GUMP · 05-09-2017, 04:28 PM

Quote:

Originally Posted by Darrel Goheen

I didn't think I needed 60 lb. 36 lb would be plenty. I only bought the 60 lb because I had a friend with a set that had very little time on them that he sold to me cheap. I think my LS1 has 42's in it.

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.

GUMP · 05-09-2017, 04:36 PM

Quote:

Originally Posted by Kdw1403

Data show instantly fuel pressure dropped to 25 and stayed there till I let off at 6700rpm.

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?

Ed Wright · 05-09-2017, 08:34 PM

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.

cmracing · 05-09-2017, 10:16 PM

Quote:

Originally Posted by Ed Wright

Why in the world would anybody think a B/SA car needed 60 lb injectors? That is forced induction stuff.

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.

Ed Wright · 05-10-2017, 08:41 AM

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

pbp1 · 05-10-2017, 10:33 AM

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.

pbp1 · 05-10-2017, 10:39 AM

Quote:

Originally Posted by Darrel Goheen

Are you in agreement that 60 lbs of pressure will offer better performance/fuel burning than 45 lbs.? My plan is to run 4 back to back runs Fri night. Two at current 45 lbs. pressure then change to 60, change fuel pressure in software and make two passes to see if it makes any noticeable change in performance. Thanks.

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.

Darrel Goheen · 05-10-2017, 10:45 AM

Quote:

Originally Posted by pbp1

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.

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

05-09-2017, 08:34 PM	#45
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	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. __________________ Ed Wright 4156 SS/JA

05-10-2017, 08:41 AM	#47
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	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 __________________ Ed Wright 4156 SS/JA

05-10-2017, 10:33 AM	#48
pbp1 Junior Member Join Date: Mar 2013 Posts: 78 Likes: 11 Liked 18 Times in 5 Posts	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. __________________ David Page Fuel Air Spark Technology (FAST)