need help with what size injectors to use
05-10-2012, 07:50 PM
#1
Heel & Toe
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need help with what size injectors to use
i just installed a new cam and heads on my 86 c4 and i need to know what size injectorrs it has in it now with the factory tpi? then i need to know what size i should have after upgrade.my upgrade consisted of the following
new Aluminum brodix heads with 202/160 valves
they flow at the intake 274 and ex flows 197 . 62cc
Roller cam lifters and rockers.
cam lift is 525/525 duration is 272/278.
i have a factory bottom end only for a while and the factory tpi.
tpi/short block will be changed but i wanna know what to use for injectors so i dont burn a hole in my pistons for now plus im going to use the first TPI system . so any tips and other comments on my built
new Aluminum brodix heads with 202/160 valves
they flow at the intake 274 and ex flows 197 . 62cc
Roller cam lifters and rockers.
cam lift is 525/525 duration is 272/278.i have a factory bottom end only for a while and the factory tpi.
tpi/short block will be changed but i wanna know what to use for injectors so i dont burn a hole in my pistons for now plus im going to use the first TPI system . so any tips and other comments on my built
05-10-2012, 09:45 PM
#2
Le Mans Master
Contact Jon at FIC !
Fuel Injector Connection
Tel: 770-888-1662
Jon at FIC
http://fuelinjectorconnection.com/shop/
SEND FICINJECTORS A PM HERE
Fuel Injector Connection
Tel: 770-888-1662
Jon at FIC
http://fuelinjectorconnection.com/shop/
SEND FICINJECTORS A PM HERE
05-12-2012, 07:14 AM
#4
Le Mans Master
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What makes you think the ones you have aren't big enough?? The size you have now may be adequit for your mods. It may be all you need is a new tune to accomodate the increased flow (read: injectors are not like jetting a carb every time you mod something).
Unless your mods are in accordance with a specific and well tested plan that calls for a specific injector, you or your tuner will need to evaluate the AFR with a wideband O2 in closed loop AND at WOT to see if you're going lean. And, it is quite possible to tune the AFR tables to accomodate your mods - again w/o changing the injectors.
If you're maxing out in the program (dwell) and still leaning out, that would indicate either bigger injectors, or possibly a dynamic fuel pressure adjustment under (WOT) conditions (e.g., the LSx motors).
My point is, if you are not staving for fuel, why be sucked into installing bigger injectors?? If you ARE leaning out (at WOT) and the injectors are maxed, but just a little, a fuel pressure adjustment might get you back in the window.
But, if you DO increase injector size, know that the dwell time decreases with flow rates, and at idle it is possible that the dwell time is so short that the injector fails to respond quickly enough and idle quality suffers. (This is in part why the LSx uses variable fuel pressure over the range of demand: Low pressure = better idle quality due to long (enough) dwell time, yet at WOT the pressure is increased, effectively increasing the flow rate of the injector and thus extending the range of the single injector.)
And, then there's the alcohol and rust issues. Flow rates aside, some new stainless injectors to go along with your mods might be just what the doctor ordered!
But, whatever you decide, one of the books that should be on everyone's "required" reading list, especially if you modding an EFI motor is Charles Probts' book; "Corvette Fuel Injection & Electronic Engine Management". All of what I've said here is in this book. It is an excellent read!
P.
Unless your mods are in accordance with a specific and well tested plan that calls for a specific injector, you or your tuner will need to evaluate the AFR with a wideband O2 in closed loop AND at WOT to see if you're going lean. And, it is quite possible to tune the AFR tables to accomodate your mods - again w/o changing the injectors.
If you're maxing out in the program (dwell) and still leaning out, that would indicate either bigger injectors, or possibly a dynamic fuel pressure adjustment under (WOT) conditions (e.g., the LSx motors).
My point is, if you are not staving for fuel, why be sucked into installing bigger injectors?? If you ARE leaning out (at WOT) and the injectors are maxed, but just a little, a fuel pressure adjustment might get you back in the window.
But, if you DO increase injector size, know that the dwell time decreases with flow rates, and at idle it is possible that the dwell time is so short that the injector fails to respond quickly enough and idle quality suffers. (This is in part why the LSx uses variable fuel pressure over the range of demand: Low pressure = better idle quality due to long (enough) dwell time, yet at WOT the pressure is increased, effectively increasing the flow rate of the injector and thus extending the range of the single injector.)
And, then there's the alcohol and rust issues. Flow rates aside, some new stainless injectors to go along with your mods might be just what the doctor ordered!
But, whatever you decide, one of the books that should be on everyone's "required" reading list, especially if you modding an EFI motor is Charles Probts' book; "Corvette Fuel Injection & Electronic Engine Management". All of what I've said here is in this book. It is an excellent read!
P.
