Lets talk injectors...
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Lets talk injectors...
Seems that there are multiple "rating" systems & of course styles & preferences.
Could someone care to give a nice overview to pull my current knowledge together a little better.
I see lbs ratings, flow ratings, pressure ratings, disc type, pintle type etc. etc.
Or at least point me to a good place to read up, without being a cure for insomnia would be a nice bonus.
Oh & by the way, have figures on stock injector size that would have come in my '90? I had TPIS do a clean/blueprint back in '99 & they showed 19.76 - 20.12 lbs/hr range when done...
Could someone care to give a nice overview to pull my current knowledge together a little better.
I see lbs ratings, flow ratings, pressure ratings, disc type, pintle type etc. etc.
Or at least point me to a good place to read up, without being a cure for insomnia would be a nice bonus.
Oh & by the way, have figures on stock injector size that would have come in my '90? I had TPIS do a clean/blueprint back in '99 & they showed 19.76 - 20.12 lbs/hr range when done...
Last edited by Trog; Dec 20, 2005 at 12:28 AM.
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Here's the quick run down on injectors.
Injectors are rated for a certain flow at a certain pressure. Given that you can adjust the pressure going to your injectors than you can increase the flow comming out of them. Injectors are basically a little hole that you open and the more pressure you have behind it the more fuel that comes out. And the larger the flow rate the bigger the hole.
Most injectors are rated at a given pressure, 45psi I think. So then you are comparing apples to apples. But some of them, like FMS injectors, are rated at a different pressure so you would have to convert the flow rate at the same pressure to understand the flow rate. My point here is don't just by a 42#/hr injector make sure its a 42#/hr @ 45psi injector.
You want to keep your duty cycle, or the time the injector is open, at under 80%. You can go higher than this, but in choosing the right injector keeping it under 80 should be a goal. You theoretical crank horsepower should be used to figure out your correct size.
I'm not sure about the disk or pindle types, if they work they work. I'm not sure of the advantages or disadvantages of each. Injectors aren't that complicated if you do a search on google I'm sure you can find a calculator to help you choose the correct flowrate for your application. If you aren't planning on doing anything major your current injectors should be fine.
The general rule of thumb is:
Injector size = (HP X BSFC) / (8 X duty cycle)
BSFC for a N/A engine is .45 and for a blown application is .55 is the general rule.
so for 500chp super charger we've got
500 * .55 / (8*.8) = 42.96#/hr
Injectors are rated for a certain flow at a certain pressure. Given that you can adjust the pressure going to your injectors than you can increase the flow comming out of them. Injectors are basically a little hole that you open and the more pressure you have behind it the more fuel that comes out. And the larger the flow rate the bigger the hole.
Most injectors are rated at a given pressure, 45psi I think. So then you are comparing apples to apples. But some of them, like FMS injectors, are rated at a different pressure so you would have to convert the flow rate at the same pressure to understand the flow rate. My point here is don't just by a 42#/hr injector make sure its a 42#/hr @ 45psi injector.
You want to keep your duty cycle, or the time the injector is open, at under 80%. You can go higher than this, but in choosing the right injector keeping it under 80 should be a goal. You theoretical crank horsepower should be used to figure out your correct size.
I'm not sure about the disk or pindle types, if they work they work. I'm not sure of the advantages or disadvantages of each. Injectors aren't that complicated if you do a search on google I'm sure you can find a calculator to help you choose the correct flowrate for your application. If you aren't planning on doing anything major your current injectors should be fine.
The general rule of thumb is:
Injector size = (HP X BSFC) / (8 X duty cycle)
BSFC for a N/A engine is .45 and for a blown application is .55 is the general rule.
so for 500chp super charger we've got
500 * .55 / (8*.8) = 42.96#/hr
Last edited by mn_vette; Dec 20, 2005 at 11:22 AM.
