The Basics of EFI Conversion
 

There's a lot of experience and brainpower on this board among members who have gone through the conversion from carb to EFI or from stock EFI to modified EFI. This is a subject that I would like to learn more about and I'm sure others would too.

All I know is a little bit about injectors. A little knowledge is always a dangerous thing.:rolleyes:

Q. If Johnny had eight 50 lbs/hr injectors operating at a duty cycle of 75%, how much horsepower could he support without raising fuel pressure?

A. I get 600 HP. Is that right?

I have seen custom setups with 16 injectors which could presumably support 1200 HP and work well at low speeds by using only eight injectors. I see that there are now 65 lbs/hr injectors good for 780 HP or 1560 HP with 16 of them. How do you drive 16 injectors? What's the difference between high impedance and low impedance injectors?

Let's thrash this subject like we used to thrash tech subjects on this board. Winter's coming, bench racing season is upon us!

This is a subject that I would like to learn as much as possible about as well. What is the formula you use for determining the maximum horsepower from a particular set of injectors??

If my parts ever get here we will see how 95 lbs /hp injectors work out.

Holley's web site had the formulas for coming up with what injector to use with what max HP.

I'm here to help so throw your questions at me. I have extensive knowledge of EFI systems in automotive applications, but I'm sure marine systems are very similar. I know my MPI system is.

Later
Roby

(# of injectors ) * ( injector size Lbs/hr ) * (duty cycle)
-----------------------------------------------------------------
( 1/2 Lb of fuel per hour per hp)

eg. for 38 lb injectors

8 * 38 * .90
--------------- = 547 hp
.5

The 50lbs inj. at 75% DC @ .50 BSFC will support 600hp.

A supercharged engine might run @ .58 BSFC therefore the 50lbs. @ 75% DC will only support 520hp.

Some ECU's and some injectors don't mind running 90% DC some don't like it and will heat up.

Most supercharged engines also have a 1:1 boost regulated fuel pressure regulator to keep the fuel flow to the engine constant.

The fuel pump, Fuel lines, Fuel pick-up all need to be larger to support EFI and even larger to support EFI Blown. You need a lot bigger pump
to support 600hp EFI Blown then 600hp carb natural.

I knew I shoulda paid attention in math class!!!!

Finally got 2000cfm throttle body, fast ecm, 8 injectors, wiring harness, fuel rails, & most of my sensors today. The only one they forgot to ship was the wide band O2 sensor & the manual (who needs that stinking manual). At least I was able to pull it off the web site. Since it has taken over a month to get the parts I was worried something would be missing.

Hope to call you next week TC & see if we can do a trial fitting with the 2000cfm throttle body.

I have had several engines with modified ecu's, one that was changed from carbed to EFI, a cent. supercharged EFI, and currently working on a two Merc. 575's one old 540ci merlin head,and a 575 SC. Also working with different combinations of headers and other mods on a 496 HO. All have turned out rather well.

Has anyone run an Accel Gen 6 ECU on a boat motor?

Thanks
Dick

FYI...The manual for the FAST is in the help section of the software. I've never gotten a hard copy.

Bob

I was planing on mounting the ecm next to my msd box on a plate that i have mounted on the back of the bell housing. after reading I am now concerned about mounting so close to the coil & msd box. anyone got ideas where i should mount it.

The Holley efi intake has some ears where the fuel rail can be mounted. In looking at the fuel rails there are no brackets to fasten them down. I can make my own brackets but is there anything special I need to know?

After reading about the NA 540's dyno test, which is my motor but with 335cnc AFR heads. & only 8:1 compression I started running my numbers I see where my fuel pump will not be big enough to handle the HP. I am looking at going with Aeromotive eliminator fuel pump & regulator. Do I plumb out of the fuel pump to a t-fitting then to the front of each rail, then put the regulator on the back side of the rails & return the unused fuel to the tank?

anyone interested in fuel injection should have this web site memorised. www.lindertech.com. Jim Linder is one of the leading fuel injection minds in north america. He has injected just about everything you can think of from hot rods to lawn mowers. He is a terrific technical instructer and a dam fine cook too :) Also a great supply place for things fuelish. and the worlds leader in injector rebuilding and blueprinting.

Check out www.injector.com

Turbo Tim, is that you???
Joe D. (320efis)

These injectors are the best that money can buy. I love them and they have never given me any problems. When building a high HP engine I wouldn't dream of using anything else.

http://www.rceng.com/

fuel injection calculator
 

I went to Marren Fuel Injection's website. They have a neat interactive injector calculator that tells you what size injector you need for the horsepower you make. It can also tell you how much power your injectors can make if you know how big they are. Go to www.injector.com. On the menu on top, click on information, then on injector selection guide.

Ha, Joe D How's it's going ? Hope everything is going good. Have to meet up with you @ Block this year.

Things are going, well unfortuatly I've got to pull one of the motors again, it seems like the rings did not seat or one of the pistons has a hole in it, I'll know once we get the heads off. This time we will dyno both engines before they go back in.
I'm going to paint the engine comartment white while everything is apart, and I'm sure it won't stop there....
I've been day dreaming about running out to Block... it's the only thing that keeps me going while I'm wearing long johns and three shirts
Glad to see you made it to the web site

For what it's worth I used the Marren folks to I guess what you would call blueprint some injectors and they were fine to work with. Also used Kinsler alot as I ran the Kinsler 8 indiv runners and they were great and very competent but expensive. The FAST people were super and the system worked very well!

I just saw a wiring harness off an 500 EFI and it looks like there are two set of 4 injectors wired together. Do they fire 4 injectors at a time?

Here is regulator question . I know the regulator goes on the back side (from fuel pump to fuel rail to regulator) of the fuel rails. I am wondering if the regulator location is inportant. Does it need to be mounted close to the rails or can it be mounted about 1.5-2" away?

the closer you mount it, the faster the pressure changes will happen in the rails but 1 to 2 inches would present no problem at all. Many manufacturers in the cr world are tank mounting the regulator these days.

OK, I miss typed. I should have typed 1 - 2 FEET away, not inches.

I talked to Aremotive today & they said being that far away would be OK, but would rather see it closer