Just want to see what pressure setting that people are using with there 24lb svo inectors. (Without Vacume)

 

Standard GM pressure is 43 with the vacuum line disconnected and plugged, which should net 39-40 at idle, I beleive. They are actually rated at 43.5 PSI.

 

Maybe with a bigger cam, it should be lower than that. Otherwise I would start looking for leaks and such. I have a hot cam that sees 39 at idle and 43 at WOT.

 

56psi, but she aint stock, LOL.

 

SVO injectors aren't rated at the same pressure as GM pieces. GM injectors are rated at 43.5 and SVO injectors are either 38 or 39 IIRC. I know its in the 30s though...

 

52 psi with my mods.

Actually, the fuel pressure setting for you could be alot different. You should set the fuel pressure at whatever pressure makes the engine happiest at WOT. Dial in the fuel pressure that yields 12.8:1 AFR (or there abouts), while in PE mode. While not in PE mode, the ECM will learn and get you the desired 14.7:1 AFR at part throotle.

BTW: Our GM fuel injectors are rated at 43.5psi and the Ford injectors are flow rated at 39.5psi. However, there is a person on this board who had his SVO 24#/hr injectors flow rated at Cruizin Performance and they flowed 24#/hr @ 43psi. Go figure!!!

 

Actually, 12.8:1 is not ideal power. That is just above safe lean best torque at 13.0. Then it goes up to best rich power at 11.5.

Yes the ECM can in a sense "learn" a desired blm but if it goes +/- 0.10 from the VE table than it will set a code. Allowing the ecm to correct itself is not an approach for longetivity, rather tuning is. Too small a pulse width at idle can be unstabble and, bad.

 

11.5:1 to way rich even for best power. In all the threads I have checked and all of my tuning manuals state that best power is typically gotten at 12.6. But this can vary with the specific mods to the engine.

I stated 12.8 because its a good compromise between best power and best torque AFRs.

In the above starter post, we are talking about an injector which is close to the stock GM injector as far as flow is concerned. A chip change would be good but is not necessary. But the cost of an AFPR is well founded to dial in whats good for the motor at WOT. The part throotle stuff will take care of itself. I stand by my words on this matter.

BTW: The way BLMs work, you should not have a problem with setting an error code until you are about 16% off. That covers a pretty good range.

 

12.8 is best torque, and 13.3 is best power. Straight from several dyno shops I know of.

As for the pressure. Set it where you need it. I would leave it at the factory 43.5 and then tune w/ the chip from there.

 

Just had my 24lb SVO flow tested and they averaged 25lbs per hour at 42psi, part number crosses to ford truck 360 injector rated at 26lbs per hour.

 

Changing the fuel pressure effectively changes the flow rating of the injector.

http://www.rceng.com/technical.htm

(Squareroot(new pressure/old pressure) ) * old_flow_rate = new_flow_rate.


As an example, I have a set of SVO 30 lb/hr injectors (red top). If they are rated by Ford at 39.5 psi and I up my fuel pressure to 50 psi, my new flow rate is:

Squareroot(50/39.5) * 30 = 33.75 lbs/hr.

Or, as an extreme, if I up my fuel pressure to 60 psi: (does anyone go this high?)

Squareroot(60/39.5) * 30 = 36.97 lbs/hr

The one thing I don't know is, how different would an engine run if it has 30 lb/hr injectors running at 60 psi, versus 36 lb/hr injectors running at 39.5 psi.

-Dave

 

this was debated and argued. Ive run 2 sets in two vastly different cars.

Stock: Set the Constant at 24# with stock fuel pressure(43.5) and leave it alone :-) works perfect. Datalogged it watched it changed it, leave it at 24


Modified, start at 24 and change from there accordongly to pressure and your combo etc. Less lying you do the easier it makes your life on the VE table and thus the AE stuff

later
Jeremy

 

I don't have all this stuff figured out. One guy told me to set it at 49 some say 47, some say 43....how do i know what one to run. Have vette ported heads, XE268 cam. I do have the pump to push the high pressure too. I noticed I'm running alittle rich to right now. I just don't know where to set it at

 

snow,

Every car is different, you have ported Vette heads and a big cam, and you are in Colorado. Your car might like anything from 43 to 50psi.

You need to get on a chassis dyno with a wide band O2 sensor and tune-in the best fuel pressure to maximize your RWHP. OR go to a dragstrip and let the trap speeds (not ET) dictate whats best for your engine.

 

BTW:

From the varying flow rates given above for 24#/hr SVO injectors,
just points out the importance to have your injectors flow matched. There is alot of variation in a set of injectors. Send them to Cruzin Performance, Rich is great to work with and he knows his stuff.