Went racing last night. Got to log a run FINALLY after fighting off stupid issues every other time we have been to the track.

So what happens? We hit the wall of the injectors. Left the line off idle and then stabbed it. @ 4300 rpms the motor pegged 30psi of boost and the injector duty cycles hit 116%. Im using 84# injectors which are now looking too small. The AF ratio went to 13.2:1 at that point too. I grannied it the rest of the way down the track and got some other readings at various throttles and boost. It starts going lean on me about 15psi of boost.

Time to step up to larger injectors I think or *TRY* to be conservative and only run about 22psi. Ha right. Probably start looking into 160# to feed this thing.

 

What about increasing the fuel pressure to increase the injector flow? Say like running 72 lbs of fuel pressure would increase the injector flow from 83 lbs to 107. What do you think the approximate hp you are going to be making? An 83# injector should support up to 1300 hp or more. I know of a guy who is making around 1400-1500 hp running 83# injectors but at very high fuel pressure.

 

Hmm, that is an interesting theory. I hadnt thought about that. My fuel pressure is set ~ 48psi. I dont have a rising rate regulator since I have the speed pro to control pulse width. Hmm

EDIT: let me rephrase that. I DO have a rising rate regulator but dont have the line hooked up to it

 

Next time try the car with the vacuum line hooked up to the regulator so it can raise fuel pressure as boost builds. What fuel pump are you running and what regulator? How do you like the Speed Pro is yours bank to bank?

 

Guido,

Am I to understand that your fuel pressure does not increase with boost? Is it because your vacuum line to the regulator is not connected?

If I make the assumption that your fuel pressure does not rise under boost, the following holds true. If I'm wrong, never mind!!

Think about this: Let's say your fuel pressure vacuum line is not connected. Let's further say that it's set at 50-psig. Now, at 20-psig boost, the injectors have to open and spray fuel in an environment that's under 20 pounds of pressure. That literally means your 50-psig in the fuel lines and shown on your gauge is effectively reduced to 30-psig.

If you connect the vacuum line to the regulator, then the following occurs: Let's say that for every pound of boost you make, your fuel pressure rises ~1 pound. I've found this to be almost the case. Then at 20-psig boost, your fuel pressure will be at 70-psig (in the rails and on your gauge). Realistically though, you're really at 50-psig. Keep in mind that you must subtract the amount of boost you're making from your gauge to determine your REAL fuel pressure.

Willie

 

Guido,
The vacuum reference must be hooked up!
Everything that Willie said is 100% correct. Another thing to consider is raising the static fuel pressure. Second Street Speed wants no less than 65# with an 83# injector. Tory's and my car are both set at 65# static.
But most importantly, Add that boost reference!
So... how did the 60' and 330' look?

 

LOL....for as smart as you are sometimes Guido you leave out the LITTLE things

hook that damn line back up and go racing....sheesh

Mr. "i didn't know those wires wouldn't work with that MSD box"

I still love ya!

 

nobody mentioned that the fuel flow is relative to pressure on both sides of the injectors, if your at 100kpa and 43psi fuel pressure your squirting with 43 psi. If your at 30 psi above atm and the fuel pressure is at 43psi your about as effective as 13 fuel psi .

I would say like everyone else get the regulator working right, no sence and running any big injector when pressure is all you need..

of course my setup is no where near as wicked and i'm talking from what i dream up

 

rooster433,
Isn't that exactly what Willie had said?
I believe it is

 

Some people on another board Im on told me the same thing about the regulator. Im going to get it hooked up.

No good times on it that night Don. Not even good 60'. The track was terrible and the second run I just rolled out off of idle and stabbed it.

 

I really like the idea of 65 # static "and" the reference hooked up like blown bird suggested.

 

B4Ctom1,
Thanks, I was told by S.S.Speed that a higher fuel pressure on a large "pintle type" injector (such as the 83#) would help atomize the fuel, rather than "squirt" the fuel. It all seemed to make sense, and has worked so far for myself, and T.Hess.
DonB.

 

Nice Guido… since no one bothered (and I was curious), here are some exact #’s for you.

Assuming “pegged the 30psi gauge” meant 30psi boost (best possible scenario, if you saw more boost you saw even less fuel), that meant that the pressure differential across the injector was 15psi. At that pressure your monster 83lb/hr injectors were only flowing 48lb/hr, which is roughly enough to feed 650hp at 100% duty cycle.

Lets say that that was actually 35psi boost, then you saw only 39lb/hr fuel from each injector, only enough for 530hp at 100% duty cycle…

I’d hope that 30psi boost on that big small block is worth quite a bit more then that.

 

I appreicate the advise guys. I took a couple days away from the car over the weekend and let my brain air out from working so much on it.

Last night I pulled the plugs and did a little investigating. We are going to do some more investigating tonight to see if there is a blown headgasket.

Boost is cranked all the way back down to 5psi now and we will be doing some driving this week to get her ready to go to Bowling Green. Some of the best f-body racers will be there and hopefully, if I need it, i can get some help.