Here is my setup. ATI 600b with 8lb pulley. Wahlbro 255lph pump. Running Lucas 38lb injectors. Being dyno tuned with LT1 edit. Car runs 12.50-12.60 A/F at WOT. However, once 4400+ comes up the injectors are going 99% cycle and A/F climes up to 13.60 and higher. Making 331hp at 4490RPM and 371Tq at 4322 rpm. HP heads south after 4490. Can't see why these injectors aren't large enough. I was told that I should perhaps put in 36lb SVO injector offset tables to correct the injector cycle issue.

Any help on insite apprecieated

Adam

 

you need larger injectors, or will need to raise your fuel pressure quite a bit to make those 38lb work

 

What kind of fuel pressure should I be seeing....it runs 39psi at idle...climbes to 55psi at WOT then comes back down after a few seconds of WOT.

Are you talking adjustable pressure regualtor purchase?

Thanks
Adam

 

Do you have a boost referenced regulator, to increase the pressure? If not, that will help.
But I also think you will need larger injectors.
The Ford injectors are rated at a lower pressure than the GM, something like 36-38 psi? So they automatically give you more flow at GM standard 43.5 psi.

My car sees 51 psi at 6-7 psi of boost, actually a little richer than needed but I had it safe. I have SVO 47# in mine, and they are nowhere near maxed.

Just for a "crutch" on the dyno, you could try raising your pressure if you have an adjustable regulator, and see where that leads you in regards to injector sizing.

 

No boost referanced regulator. The dyno is like 2 1/2 hrs away and I keep making trips with getting nothing accomplished. Triing to guage from everyone's opinion, if it is the injectors or pressure. I will buy what it takes to get this done right but would rather buy one of the two Lord knows I've dropped some cash as it is.

Adam

 

Well, you have two ways to go with it.

1. Raise the fuel pressure with a boost referenced AFPR (make sure it is a rising rate, 1 to 1 type. Not all of them can handle boost. I have a standalone Aeromotive, they also make one to go on the stock rails.)
By increasing the pressure, you *may* be able to get away with the injectors you have.

2. get larger injectors, and use the map and LT1 edit to get the extra fuel in under boost. You do have a 2-bar map sensor? If not, then you'll have to go with the rising rate AFPR.

You say your FP goes up for a second, then drops back. Does it go back below 44-45? I don't know how the stock reg. acts under boost, just curious?

 

The boost referanced AFPR sounds like the way to go. My tuner had mentioned that. Where to purchase this? My pressure goes up but doesn't go below 44psi I believe. I don't know what bar my map sensor is. If I give more pressure that will keep in injectors from working so hard?

Thanks for you help by the way

Adam

 

Any mail order house, or speed shop specializing in fuel injection should be able to hook you up. I know Jegs or Summit has the Aeromotive brand for the stock rails.

If you haven't changed out the MAP, then it is a 1-bar, which means the computer doesn't know how much boost it is seeing. And I am not familiar enough with LT1 edit to know if the stock pcm can handle a 2-bar.

I would recommend trying the regulator first, and see what you can get. You should adjust it idling with the hose off to around 44, and then see a 1 to 1 increase with boost (so 8 psi would show 52 from a 44 base)

Do you know how much pressure the Walbro will put out? That will be the next limit, without smaller injectors. My A1000 is supposed to be good for 65-70, so we'll see when I get to that point.

 

If you are using the stock regulator, it is boost referenced. That's why your FP rises as the boost increases. IOW, the stock regulator is a 1:1 FMU, in a manner of speaking. You do have two basic choices. Larger injectors or higher FP. You can get higher FP by using an FMU (ie a boost referenced FPR that operates at a ratio >1:1) or an adjustable FPR (that is boost refernced at 1:1). If you go the AFPR route, you will need a lot of tuning because it will function by raising the base FP. This will prevent the leanout at high rpm, but will make it rich down low and at part throttle.

I agree that the best approach will simply be larger injectors. Something in the range of 50lb/hr would be my recommendation. Keep the stock regulator if you go to larger injectors, as it should work fine.

Rich

 

First off thanks to everyone.
Rich I've allready beaten this poor car in tuning it. First it was a pulley that was two small making to much boost (bought the charger used ) so we changed that after a few runs seeing way to much boost and now this. Yesterday we made a ton of passes triing to add in fuel up high on each run. We kept adding fuel values but to to avail. Then we found the injectors were topped out. It sounds like bigger injectors are the way to go. Would 42.5lb injectors do the trick you think? My tuner mentioned that 50lb would be harder to tune down low because its hard to slow a big injector down at idle and part throttle. Basicaly I'd be real rich at low rpm. The car is more street then race so I'm triing to keep it drivable.

Thanks
Adam

 

50lb injectors work fine, in my experience. I am not sure that the 42lb injectors would be big enough.

Rich

 

Everyone else kind of ignored this, but, I am worried abotu this. You are saying your fuel pressure climbs when you first punch it then comes back down? It should stay high and continue going higher as your RPMs increase. If it is coming back down, what is it coming back down to?

This could be a sign your fuel pump isn't keeping up with the demand.

--Sean

 

Well ya see at the time I was holding the fuel guage while up on the dyno watching as he did some runs. I was also watching a boost guage at the same time. With the comotion and all it could be that I was seeing the pressure drop as he knowticed it was going lean therefore letting off, and the boost would drop, as would the pressure. Now you have me doubting myself.....hmm.

 

Take a fuel pressure gauge, duct tape it to the windshield and make a run on the street. You dont' need to look at the boost gauge, just see if the pressure climbs as the RPMs increase, it should never decrease until you back off the throttle..

--Sean

 

Hello, I am the guy who sold Adam his kit. Boy, what a pain in the butt this has turned into..... Anyways, I sold him the kit sans inline fuel pump. He has a 255 lph in-tank pump that I suspect may not be able to keep up with the demands of his 38 lb injectors. ATI says that 38 lbers should be able to keep up with the fuel requirements, but recommends that the 255 inline be used. Adding the FMU to the setup at the moment does not seem to be the solution to this problem. I will put a FP gauge on the car and verify that this is indeed the problem. This sure explains a lot. I hope that Adam does not hate me for getting him into this mess. I am really trying to help him get this done right.
Any thoughts?