Injector size
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
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From: Seattle Wa
Injector size
I’m doing a stealth ram build, and would like to hear some input on injector size. I’m using a Comp xfi 280, (says 550ish lift) afr enforcer heads. Has a 2400 stall and 3.54 rear. I have been told everything from, stock will work fine, and “You need 42s”! Lol I tried Messaging FIC and he never got back to me. Is he still the go to, for quality and performance? Tia Bart
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
I’m doing a stealth ram build, and would like to hear some input on injector size. I’m using a Comp xfi 280, (says 550ish lift) afr enforcer heads. Has a 2400 stall and 3.54 rear. I have been told everything from, stock will work fine, and “You need 42s”! Lol I tried Messaging FIC and he never got back to me. Is he still the go to, for quality and performance? Tia Bart
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
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From: Seattle Wa
And this is why I can’t make a decision. They got back to me and said 24lb, and you’re running 42s? Had a tuner tell me he “thinks” he can make 26-28 work. Why is there such a drastic difference?
Pro
Joined: Sep 2019
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From: Buchanan, Michigan
Many will simply jack up the fuel pressure to make the stock 22-24 lb injectors work. If you do wind up buying larger injectors get them from a reputable source that has accurate dead time latency data for the injectors they are selling. It can save your tuner a lot of time.
If your car is newer than 93 and has the better ecm, and is sequential injection you can typically use a larger injector without fear of idle tuning woes. Batch fire tpi and early lt1 batch fire ecu are a lot easier to tune the idle areas and part throttle drivability stuff if you stay with stock or under 30 pph injectors, at least According to everything I've read over at third gen site. Best advice is find a reputable tuner and do what he says. I can say for tpi stuff guys like Hanson prefer you stay with a 24# ford motorsports injector or something they are familiar with. In closing use the injectors that fit your needs and no larger. That's the best way to do it. Especially if using stock ecm. More confused now? 🤣
If your car is newer than 93 and has the better ecm, and is sequential injection you can typically use a larger injector without fear of idle tuning woes. Batch fire tpi and early lt1 batch fire ecu are a lot easier to tune the idle areas and part throttle drivability stuff if you stay with stock or under 30 pph injectors, at least According to everything I've read over at third gen site. Best advice is find a reputable tuner and do what he says. I can say for tpi stuff guys like Hanson prefer you stay with a 24# ford motorsports injector or something they are familiar with. In closing use the injectors that fit your needs and no larger. That's the best way to do it. Especially if using stock ecm. More confused now? 🤣
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
It all depends on the HP you will be making. HP that can be supported very easily = ((injectors size/.5 x 8)X.8) (injectors size/BSFC x number of cylinders) x injectors duty cycle
Typical BSFC = .4 to .6 so use .5
Injector duty cycle target 80% or .8
(24 lbs /.5 x 8) x .8 = 307 HP with 24 lb injectors that is very conservative HP estimate but it will work fine for your needs.
You determine your HP estimate and use the above formula to figure injector size.
Typical BSFC = .4 to .6 so use .5
Injector duty cycle target 80% or .8
(24 lbs /.5 x 8) x .8 = 307 HP with 24 lb injectors that is very conservative HP estimate but it will work fine for your needs.
You determine your HP estimate and use the above formula to figure injector size.
Last edited by bjankuski; May 19, 2021 at 10:40 AM.
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
Likes: 12
From: Seattle Wa
Many will simply jack up the fuel pressure to make the stock 22-24 lb injectors work. If you do wind up buying larger injectors get them from a reputable source that has accurate dead time latency data for the injectors they are selling. It can save your tuner a lot of time.
If your car is newer than 93 and has the better ecm, and is sequential injection you can typically use a larger injector without fear of idle tuning woes. Batch fire tpi and early lt1 batch fire ecu are a lot easier to tune the idle areas and part throttle drivability stuff if you stay with stock or under 30 pph injectors, at least According to everything I've read over at third gen site. Best advice is find a reputable tuner and do what he says. I can say for tpi stuff guys like Hanson prefer you stay with a 24# ford motorsports injector or something they are familiar with. In closing use the injectors that fit your needs and no larger. That's the best way to do it. Especially if using stock ecm. More confused now? 🤣
If your car is newer than 93 and has the better ecm, and is sequential injection you can typically use a larger injector without fear of idle tuning woes. Batch fire tpi and early lt1 batch fire ecu are a lot easier to tune the idle areas and part throttle drivability stuff if you stay with stock or under 30 pph injectors, at least According to everything I've read over at third gen site. Best advice is find a reputable tuner and do what he says. I can say for tpi stuff guys like Hanson prefer you stay with a 24# ford motorsports injector or something they are familiar with. In closing use the injectors that fit your needs and no larger. That's the best way to do it. Especially if using stock ecm. More confused now? 🤣
SB has a set of 30lb for TPI, for a good price. And everyone says they are pretty reputable co. But I also don’t want to get too big. What are the problems with getting too big? I’ve read too small can be really lean on the top end.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Lol, probably. The tuner thing is a whole other matter. Everyone I talk to says I need to buy all this tuning stuff and do it myself. I’ve tried to explain that I’m a very good wrench, but not great with a computer. Was really hoping to send my computer to someone and have a tune burned on it, but kinda sounds like that’s a thing of the past.
SB has a set of 30lb for TPI, for a good price. And everyone says they are pretty reputable co. But I also don’t want to get too big. What are the problems with getting too big? I’ve read too small can be really lean on the top end.
SB has a set of 30lb for TPI, for a good price. And everyone says they are pretty reputable co. But I also don’t want to get too big. What are the problems with getting too big? I’ve read too small can be really lean on the top end.
Who is SB? Regardless, I would find the tuner first before I do all these mods and nobody to tune them.
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Thread Starter
Pro
Joined: Sep 2012
Posts: 610
Likes: 12
From: Seattle Wa
It all depends on the HP you will be making. HP that can be supported very easily = ((injectors size/.5 x 8)X.8) (injectors size/BSFC x number of cylinders) x injectors duty cycle
Typical BSFC = .4 to .6 so use .5
Injector duty cycle target 80% or .8
(24 lbs /.5 x 8) x .8 = 307 HP with 24 lb injectors that is very conservative HP estimate but it will work fine for your needs.
You determine your HP estimate and use the above formula to figure injector size.
Typical BSFC = .4 to .6 so use .5
Injector duty cycle target 80% or .8
(24 lbs /.5 x 8) x .8 = 307 HP with 24 lb injectors that is very conservative HP estimate but it will work fine for your needs.
You determine your HP estimate and use the above formula to figure injector size.
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
Likes: 12
From: Seattle Wa
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Dont mean to be dumb but, I missed that math class 🤔 From dyno sheets I’ve seen the cam with a similar set up to mine made 415-425hp and a iroc that put 370 to the wheels. I was thinking at least the high 3s. It would really suck to spend 3 grand and only get 40hp. Maybe I should have bought nitrous. 😂
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
Likes: 12
From: Seattle Wa
You are spending more than 3 grand. The HSR will not fit without cutting. Either the intake or the hood. I did the hood. A 350 with HSR making 370 RWHP? Sounds a little high to me. I would think that the cam works with the intake and the headers, engine, etc. Just slapping on a HSR onto a 350 rated at 240 Crank HP won't make 370 RWHP. I am guessing that the 350s you saw have more than a cam and HSR.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Dont mean to be dumb but, I missed that math class 🤔 From dyno sheets I’ve seen the cam with a similar set up to mine made 415-425hp and a iroc that put 370 to the wheels. I was thinking at least the high 3s. It would really suck to spend 3 grand and only get 40hp. Maybe I should have bought nitrous. 😂
At 425 HP you could use 32lb injectors and have no issue with idle or power.
Last edited by bjankuski; May 20, 2021 at 11:21 AM.
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
Are you in driving distance of Portland Oregon? If so, I would contact TJ Wong......
Probably one of the best tuners in the nation.
He is on the forum.
For a mail order tune, Alvin at pcmofnc.com. is one of the best.......
Pick your tuner, and let them decide what injectors to use.
JMO.
,
Probably one of the best tuners in the nation.
He is on the forum.
For a mail order tune, Alvin at pcmofnc.com. is one of the best.......
Pick your tuner, and let them decide what injectors to use.
JMO.
,
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From: Wisconsin
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To get an accurate injector size for your engine, you will need to know how much horsepower your engine will make. (Or at least have a good educated guess.) The fact that yours is one of the batch fire systems makes correct injector sizing pretty important.
As long as you know how much power you need your injectors to support, you can use one of the online calculators.
There is no "one size fits all setups at x horsepower" flow number. For example: My 85 has 44lb/hr injectors in it currently and is making 371 hp at the wheel with plenty of injector duty left to be safe but is turbocharged and requires more injector than a normally aspirated engine will to make the same power. Also, I have an aftermarket EFI system that is set up as sequential (instead of batch fire) which allows me to run larger injectors with less risk of tuning issues at idle.
As long as you know how much power you need your injectors to support, you can use one of the online calculators.
There is no "one size fits all setups at x horsepower" flow number. For example: My 85 has 44lb/hr injectors in it currently and is making 371 hp at the wheel with plenty of injector duty left to be safe but is turbocharged and requires more injector than a normally aspirated engine will to make the same power. Also, I have an aftermarket EFI system that is set up as sequential (instead of batch fire) which allows me to run larger injectors with less risk of tuning issues at idle.
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Joined: Sep 2012
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From: Seattle Wa
Thank you! That’s what I was looking for, an actual answer. Just re-read my post, and it did kinda sound like I was being a dick. Very sorry, not my intention, bad day.
Thread Starter
Pro
Joined: Sep 2012
Posts: 610
Likes: 12
From: Seattle Wa
Are you in driving distance of Portland Oregon? If so, I would contact TJ Wong......
Probably one of the best tuners in the nation.
He is on the forum.
For a mail order tune, Alvin at pcmofnc.com. is one of the best.......
Pick your tuner, and let them decide what injectors to use.
JMO.
,
Probably one of the best tuners in the nation.
He is on the forum.
For a mail order tune, Alvin at pcmofnc.com. is one of the best.......
Pick your tuner, and let them decide what injectors to use.
JMO.
,