Engine guru's/ fuel injectors
 

I am freshening and upgrading a bit. I have a 454 Mag 60 over, 7lb boost ProCharged M3 SC, Merc ignition, and the following additional. Edelbrock aluminum heads #61559 2.50 intake 1.90 exhaust, long runners are 320 short are 310, 118 CC, compression is 10:1. Cam is 236/238 @ 50 112 LC lift is 595 total custom grind with 1.8 rockers full hydraulic roller. I am currently running 50lb injectors. Will these work or should I go with 60lb injectors.
EMI Thunder exhaust. any thing besides the the reflash and possible injector change am I'm missing anything.
Bob

50# should be okay. It all depends on how your ecm is mapped.

Do you have any idea what horse power was before making the improvments? And what about % of duty cylce on the old setup? What is the fuel PSI?
If you dont have a way of looking at duty cycle, then hp and psi #'s will help.

7 LBS on a 10-1 Motor seems on the high side .....Also 2.50 is a huge intake valve ...sure it is not 2.30?
Better get lots of fuel to it for sure.....

Bryan

50 lb injectors, base fuel pressure set at 43.5, boost referenced regulator, 700 hp.

That is surely a misprint... 2.5 intake valve on a 320 head? Highly doubt that.... the valves wouldn't clear the bore on a 454.

I think 10:1 with that much boost is gonna be really pushing it with 7 lbs on pump gas. Watch closely for detonation!!!

I think GPM has a pretty good baseline.

Estimations were in the low 700's prior, Don't have duty cycle. Fuel pressure at WOT is 78 to 80.
Bob

These are the actual speck:
Edelbrock 61559 - Edelbrock BB-Chevy Performer RPM Aluminum Cylinder Heads



BB-Chevy Performer RPM 454-R Marine Aluminum Cylinder Head
315cc/300cc (Long/Short) Rectangle Ports
118cc Comb. Chambers
2.250''/1.890'' Valves
7/16'' Rocker Studs
Sold Individually

They have been ported significanlt to the 320 -310 runner. Every thing else is correct.

why so high? what was the pressure at idle?

36

RBeyer... those are some nice heads. Will make great power with a blower especially with good port work!!! I figured that the 2.5 was a typo.

But I do have to agree with GPM on the fp. I run that much fp on my turbo alcohol car with 35-39lbs of boost.

It really does not run that fat. That is what the Aeromotive fuel pressure regulator takes it to.
I have tried two different regulators and tested at the rail and the gauge same results. This is my concern I think we are at the end of these nozzles for this appliction as I think we are forcing fuel thru them.
Bob

I run Fast EFI, I was told injectors are rated at 43.5 psi, you need roughly .5 lb per HP. Running high pressure would act like a bigger injector. There is a calculation for what you are doing. I believe you can find it on Kinsler Fuel Injection. Without knowing the duty cycle at top end there is no way of telling how close you are to static.

I always say, have more injector than you need, within reason. I'll try to find HP ratings for injectors. I'd say you are real close to 800hp if not a tad more.

Builder says 825 to 850.
Bob

Found this info on FAST's website. Looks like you need bigger injectors IMHO.

Supercharged v8 peak power:

55lb/hr = 660hp
60lb/hr = 720hp
65lb/hr = 780hp
83lb/hr = 996hp

This comes with this note:
NOTE: fuel injectors in and of themselves do nothing to produce power, so don’t choose a larger injector because of the peak HP rating of the injector –too large of an injector will only waste fuel and hurt your throttle response, much like overcarbureting a non-injected engine-. Select the right injector to support the power that your engine produces -you’ll never run out of fuel, and you’ll experience great throttle response, a smooth power curve, and good fuel economy.

Wnat is the base and peak fuel pressure in this application?

Like GPM stated, I think the base is 45psi to start. I run 48psi on my car as a base, but I also run alcohol and the fp boost ratio is 1:1. So with 30lbs of boost, I have almost 80psi. But mine is also a turbo, but boost is boost right?

Here is the FAST site.... it might help.

http://www.fuelairspark.com/Products...ection_468.asp

Base 45, adding 1psi of fuel for 1 lb of boost.

I spoke with AZ Speed and Marine this evening and they suggested a 63lb nozzle wirh a static 53psi base line and reflash the ECM accordingly. They did my setup the last time. 4 years and 200 hours with pretty much no problems.

One thing that has to be considered.. the more PSI you put to an injector the harder it is to open it. More current to open it. Causing heat. If they get too hot they can start to stick and self destruct. Also you have to know what type of driver is in the ECU and not over work it or it will die also.
Most are rated at 43.5 psi. You go up from there to get a bit more flow. But going to the next step is recommended. So you dont have to run such hi psi.

Go to Marren injection and see what they say about psi and current draw. From about 50 lbs/hr on up, they are all low Z. There are some out there that are higher and still are high Z. Low Z injectors take a lot of current. When you bump up the psi.. the current draw goes up on the driver.

AZ's recommendation is probably in the ball park.

Here is a site to play with psi.. but not the bsfc. They call it .5 for NA.. where in a blown setup, it will be more like .6-.7
http://www.rbracing-rsr.com/fuelinjectors.htm

Another site... http://www.injector.com/injectorselection.php
you can vary the bsfc on this one. Play with it..

Hope this helps.
Dick

If you use marrens fuel injection guide: scroll down to the second calculator
http://www.injector.com/injectorselection.php
You can play with the numbers and get a feel for what they will handle. Something everyone needs to remember is in a "ideal" application you would have a injector that is appropiately sized to the hp limit of your motor using 43.5 base pressure and a 1-1 boost referencing regulator. The problem guys like R beyer and myself have though is we are still using factory mefi ecm's and they will only run high impedance injectors. The biggest high impedance injector out there is the siemens 63 lb (also often rated at 60 lbs).
So in order to make 800 hp the fuel pressure needs to be raised MUCH more than 1 lb for every lb of boost. As said in earlier post,by doing this your are effectively making a medium size or fairly small injector act like a much bigger one until you reach the point it quits working completely.When calculating a supercharged motor you will want to enter at least a .55 bsfc if not a .6 bsfc for your calculations.
For example: a 50 lb injector will only support 581 hp at 43.5 psi and a bsfc of .55. Now lets say your running a blower and you plan on making 850 hp (at .55 bsfc),if you keep the pressure at a steady 43.5 you would need 73 lb injectors.Again,the only injectors over 60/63 lb are low impedance which require a aftermarket ecu and program which is great for the guy with a unlimited budget or tuning time on the dyno or water but what do you do if your sticking with a oem ecu or a cheap aftermarket one that will only run high impedance injectors? The answer is you raise fuel pressure. Now all of my hp support calculations are assuming your programming has the injectors maxed out at 80% duty cycle based on a bsfc of .55 for a blown motor,if you were going to hold it at WOT for a extended time you would possibly want to plan for a bsfc of .6 which will typically get you somewhere into the 11-1 afr.
Back to raising the fuel pressure,that same 50 lb injector that only supported 581 hp at 43.5 psi now flows 67.8 lbs
(change the injector size to 50 lbs ,the max pressure to 80 lbs then hit calc)
http://www.csgnetwork.com/fiflowcalc.html
Going back to the Marren calculator (make sure you scroll down to the second calculastor),that injector will now support 788 hp at .55 bsfc,867 hp at .50 bsfc and 723 hp at .6 bsfc.
Alot of guys will tell you that injectors will "shut down" at 80 psi,these modern siemens injectors don't seem to really have that problem,I am making over 1000 hp with the 60/63lb versions at about 80-85 psi in my blown application. I hope the links help give you guys some insight plus you can play with the numbers and see where you land at,Smitty

So back to your question,will your 50 lb injectors support 800 hp,it will be VERY marginal as they will only support 788 hp at .55 bsfc. I would buy the next size bigger and have a little safety margin,Smitty

Dick,we must have been typing our answers out at the same time:D,Smitty

Oh man, didnt even think about them being high impedance. Very good point and right on the money.

Do you think the 80 psi has any effect on your fuel pump, flow, life span, current draw ?

There is no doubt that running a fuel system basically maxed out at 80 psi is hard on the fuel pump and definately draws ALOT of current. I have been running my system this way for 7 years,I have never had a fuel pump failure BUT I have had 3 different fuel pumps,the original red aeromotive that I ran for 3 years which is now on a hopped up N/A 540 in a friends boat (it couldn't keep up with my demand when I went from a 502 to a 540. Then I bought a billet essex pump which had a better lbs per hr rating at the higher pressure,I ran this for several years on my 540 but again when I bumped up the hp it couldn't put out enough to keep up. My current pump,a aeromotive elimnator has been on my boat for 3 seasons along with a voltage booster that makes it put out even more lbs per hr at high pressure under boost,problem free so far. I imagine if I ran this current fuel pump in this configuration enough hours (probably around the 250 hr mark) it would eventually fail. I carry the essex pump with me as a spare in case I'm ever stranded or break down when on vacation out of town. I know I could have bought a weldon 2025 or 2035 like what gpm is running BUT the flow output is too great under light cruising loads for my regulators and fuel lines to handle,Smitty

I just posted this message and see you guys have been discussing it.

Another thought on this subject is if you do need to run extreme psi to make you goal, then you need a fuel system that can cope with that much psi and flow. Smitty, are you using a box to increase your voltage to fuel pump to gain that high psi? And current draw on the fuel system could effect available voltage to the ECU. I found that to be the case in one situation.. Pulse Width Modulation driver circuits for low Z injectors noised up the 12v for the ECU. I installed a circuit that is a Peak and Hold driver circuit.
An option to consider is a low Z driver box. Not sure if the Merc ECU would be compatible with such a box. If it was, then your options open up a bit more. Do you spend money to make the fuel psi.. or buy bigger injectors and maybe a driver box?
I am going to try a mechanical pump this time around to lessen the load on the electrical system. It is cheaper than buying a new pump and controller box. I will be running 96lbs injectors and figure I will need about 55psi at max boost.

I agree with Smitty.. you probably ought to make a jump to the next size. And compare prices with low Z and high Z and what it might take to setup the system.
Dick

I appreciate all of the feedback. The calculator is interesting but does not allow for increased fuel pressure. Smitty and Dick, so if I go with the 63lb and run my current fuel setup (Aeromotive red with vacuum increase) I should be in good shape? I currently run 36 psi at idle. will that need to be changed.
Bob

The increased power draw at WOT would also explain my huge voltage drop trying to trim at WOT. Correct?

Bob,
I have always removed the vaccuum line to the regulator, keeping a solid psi. My Cutler used to hunt around, so I left it at one psi..
I guess in your situation (Smitty has more experience with the Mefi) you have to figure out what flow is needed at max power. Then work backwards from there. What ever boost you have has to be added to the psi that gives you the correct fuel flow. From there if you pull a vaccuum at idle the regulator will follow what is needed.
Two schools of thought: Too much psi at idle and you pulse width may have to be reduced below min open times, to get the motor lean enough to idle clean. With the regulator, you end up lowering fuel psi/flow, now you have longer PW and are still controlling the mixture, instead of running rich because you cant open and close it for such a short PW. So less psi at idle is good, to a point. At some point the fuel will dribble out of the injector instead of spraying.
With a regulator attached to the manifold, it will end up with what it is depending on manifold air pressure, be it boost or vaccuum.

Check this site out. http://www.megamanual.com/v22manual/minj.htm#size

The calcultor doesnt allow u to change bsfc, but there is a formula that you can do that with. A 63# inj with 53 psi should flow 69.5#. Working with their formulas, 850hp would need 79.6#/hr. That would be figuring .6 bsfc and 80% duty cycle.
Moving the numbers around.. .55 bsfc and 85% duty cycle.. I calculate a 68.75#/hr.. But I think that is cutting things too close. More psi..??
Go check it out, see what you come up with. When you are on the dyno, it should tell you what fuel the motor needs to live..
Hope this helps.
Dick

They give formulas and calculators for sizing. The Megasquirt is the ECU I am running. A wealth of knowledge there.

http://www.witchhunter.com/injectorcalc1.php4
another calculator site.

Thanks Dick,
I want this correct the first time I will spend hours doing my homework not to break it.
Bob

Any suggestions of someone who can dyno near northern IL.

Dick,
Let's pretend I go this route. What can I expect to spend and what about the computer.
Bob

Seems to me, we all spend a ton of money building these blower motors. If they are done right they are capable of over 2 HP per cubic inch. We run them hard, we expect them to live. The most important part is the fuel system.

Dick,with your electrical experience you ought to design a "conversion box" that allows guys with mefi ecu's and cheap aftermarket fuel injection systems like the holley/accell to drive low impedance injectors. It would be interesting because there are quite a few guys like me who would be running bigger injectors but are limited to the 60/63 lb siemens that are available,Smitty

if you go on this link it will allow you to change the fuel pressure to see what the injector will deliver,Smitty
http://www.csgnetwork.com/fiflowcalc.html

I'm running a kenne-bell voltage booster to my fuel pump that changes the output pressure to about 80 psi after 5 psi of boost,it draws alot of current,in a earlier post of yours we discussed this,I went to a 100 plus amp alternator long ago because my stock one couldn't keep up. I also run small battery cables from my alternator to where it ties into the electrical system. I also use a 50 amp bosch relay and 10 gauge wire to my fuel pump,I know it draws alot because I have blown a 25 amp fuse to it before at wot,it needs a 30amp to keep from blowing,Smitty

your aeromotive 1000 fuel pump will have a hard time keeping up with 63 lb injectors,at 75 psi they are 82.7 lb injectors. a aeromotive 1000 pump puts out 600 lbs per hour at 43.5 psi, barely enough to feed 8- 63 lb injectors (8x 63=504 lbs) at 70 psi the output drops to 400lbs per hour,8-82.7s lb injectors need 661 lbs (at 75 psi) so a bigger fuel pump will be in your future. The aeromitive ratings are also at 13.5 volts at the pump,if it drops to 12 volts you can take another 100 lbs per hour off its rating.
http://www.aeromotiveinc.com/product...sub=1&prod=164
click on "specs" after you open the aeromotive page and you will see a flow table with voltage vs ouput pressure vs lbs per hr
Smitty