Supercharging...Bigger injectors and a 2 bar MAP sensor
 

Again back for more help....I am in the process of installing an M3SC procharger on my 500 efi and have been considering doing a fuel system upgrade as well... Mark @ PMEFi has mentioned a 2 bar map sensor, bigger injectors and an ECU program to work with the fuel system upgrade, thinking this is the way to go he said it is not mandatory but would be better in the future with more upgrades. How does this work? So does the two bar map sensor take different readings of manifold preassure and adjust flow to the bigger injectors @ different boost levels or does it work in conjunction with the boost referenced fuel preassure regulater...I am still trying to figure all of this out. I believe the 500 EFI has 42 lb injectors stock and people have said they are sufficient to support the HP from the unit @5lb boost levels. I am at the point where I need to order the injectors and proceed or just proceed with the stock componants and tune from here. ANy advice ....Articfriends or anyone else with experience in this area.

And are the injectors a ***** to install. I am doing all of this my self with respect to installation but am utilizing professional help with tuning once the install is complete and will be recalibrating the ecu either way I go...

One other ? on the inductin part of the unit. I am thinking of replacing the stock Black 90 elbows that came with the kit with Blue silicone ones , I have found some , kind of pricy however any one have a lead on reasonably priced ones....I need 3 90's and one 45
Taking sunday off...............

Bryan

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

42 lb injectors will support around 700 hp at 80-85% duty cycle at 70-75 psi fuel pressure and a .5 to .55 bsfc so a upgrade is unecessary IF tuned properly.A 2 bar map sensor helps when tuning the ecm as it can help the ecm see the motor go into boost BUT as far as bigger injectors go until you go REALLY big they still will not support the extra hp without extra fuel pressure. The problem with going past 63 lb injectors to run a steady fuel pressure is they are not high inpedance,they are low impedance then the new problem with that is the mefi ecm can only fire high impedance injectors. How much hp do you want to make,your next step is 55lb injectors (good to around 800-850 hp at high enough fuel pressure) or 63 lb-good to 950-1000 at the right pressure and duty cycle at bsfc levels around .50-.55,Smitty

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

Thanks for the help.....So I am figuring that I should leave it alone and go with what I have. I am not trying to set this on kill and only want to run 5 lbs boost, so I am figuring right @ 700 hp. Mark is going to recal the computer based on his tuning of other motors in the same set up, I know not ideal but getting the motor to him to dyno is not an option at this moment. So i guess gettin it close and on the fat side is best for now.


Now what kind of FP guage are you runiing on the dash? I can only find electric to 60 lbs.....
Bryan

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

A boost referenced pressure regulator only keep the fuel pressure delta constant at different manifold vacumes and boost presures. It does NOT give you more fuel at boost, it simply allows constant flow for a given injector on-time. You absolutely must have a 2 bar map sensor if you are running boost. It's the only way the computer knows to deliver more fuel. It won't work right automatically either. You still need to have the computer reprogrammed.

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

My boost referenced regulator raises fuel pressure from 42 psi at idle to 70-75 psi under boost,its crude but does work,the alternative in my case was 96 lb injectors and a completely new computer system. I do run 1 regulator that holds fuel pressure at 42 psi and a second regulator that raises the fuel pressure and is rising rate,I also run a voltage booster to my fuel pump that turns the voltage up between 14.5 to 16 volts at 4-5 psi of boost,Smitty

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

This looks like the damn underside of a car hood... not an engine hatch on a boat....... :cool:

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

20 lbs of shiit in a 10 lb sack :D

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

Does it actually turn the "delta P" to 75psi? (not 75psi relative to atmospheric pressure) If so, where did you find injectors that fire reliably at that pressure differencial. Most stock type injectors start to get really iffy much above 65psi.

Re: Supercharging...Bigger injectors and a 2 bar MAP sensor
 

I don't know what "delta P" is,the pressure I'm running is 70-75 psi gauge,not psi-absolute if thats what your asking. The injectors are siemans if I recall correctly although I ran the stock 42lb ones at 60-65 for 3 seasons then 75 or so for 2 seasons and they were still working fine when I upgraded further. Maybe it helps that I'm running upwards of 10 psi boost so injector is firing against 8-10 psig in the manifold,Smitty