I have a 90 GT with very minor mods (exhaust, bigger TB + mass air, k+n filter). I am about to have an edlebrock performer intake manifold (upper and lower) put on the car and I wanted to also have the injectors replaced while the manifold is off because I just went over 100k. Should I go to 24 pound injectors or are new 19's sufficient? I do not have any crazy power plans for the car in the future, Possible new heads at some point but no forced induction. What should I get, 24 or 19 pund injectors? Also, if I get 24's is there any other mod I need to do, such as a different mass air, in order to accomodate the 24's. Thanks for the help.
injectors
- Thread starter habiv
- Start date
19lbs should be enough, but some people will suggest 24's. I guess thats why they say every car is different.
jector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines.
Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP
The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.
304 HP x .85 = 258 HP
385 HP x .85 = 326 HP
480 HP x .85 = 408 HP
576 HP x .85 = 490 HP
672 HP x .85 = 571 HP
Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.
See http://users.erols.com/srweiss/ to get the calculators used in these examples.
If you use larger injectors, you will neeed either a Tweecer, custom dyno tune or an aftermarket MAF calibrated to match the injector size.
Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP
The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.
304 HP x .85 = 258 HP
385 HP x .85 = 326 HP
480 HP x .85 = 408 HP
576 HP x .85 = 490 HP
672 HP x .85 = 571 HP
Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.
See http://users.erols.com/srweiss/ to get the calculators used in these examples.
If you use larger injectors, you will neeed either a Tweecer, custom dyno tune or an aftermarket MAF calibrated to match the injector size.
An intake, alone, shouldn't be enough to warrant upgrading to 24's. If you had a full H/C/I setup, then yeah, 24's would be a must, but with stock E7's and the stock H.O. cam ... nah. You're safe.
HOWEVER ... since you'll have the fuel rail off, that would be a VERY good time to upgrade to a different KIND of 19# injector. Go nab some newer-design 4-hole injectors from a 4.6L T-Bird or Cougar (orange-ish yellow in color ... some other new Fords use them, as well), put on some new O-rings, and plug them puppies in there. I switched to 'em when my three of my stock injectors cracked and started drooling fuel out the sides, and they haven't given me a problem since. Supposedly, they provide a smoother idle and better combustion because they've got a finer spray pattern - I dunno if there's any reality to that or not, but they are a better quality design, overall.
Even if you don't swap out the injectors for new/different ones, DEFINITELY replace the O-rings and pintle caps while you've got 'em out. You do NOT wanna have to deal with that leaky headache later on, trust me.
HOWEVER ... since you'll have the fuel rail off, that would be a VERY good time to upgrade to a different KIND of 19# injector. Go nab some newer-design 4-hole injectors from a 4.6L T-Bird or Cougar (orange-ish yellow in color ... some other new Fords use them, as well), put on some new O-rings, and plug them puppies in there. I switched to 'em when my three of my stock injectors cracked and started drooling fuel out the sides, and they haven't given me a problem since. Supposedly, they provide a smoother idle and better combustion because they've got a finer spray pattern - I dunno if there's any reality to that or not, but they are a better quality design, overall.
Even if you don't swap out the injectors for new/different ones, DEFINITELY replace the O-rings and pintle caps while you've got 'em out. You do NOT wanna have to deal with that leaky headache later on, trust me.
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