bsfc with nitrous
Thread Starter
TECH Junkie
Joined: Dec 2012
Posts: 3,606
Likes: 1,318
From: Iowa
bsfc with nitrous Hey all. I'm trying to size out a fuel pump and injectors for an upcoming build and i'm having a tough time getting an answer i'm confident about.
The build is an ls swapped fox. It will be an lm7 pulled from a 99 silverado with gen 4 flat tops shoved in place of the dished pistons. 862 heads with the intake valve opened up to 2". 11:1 compression. 226/234 (ish) cam, sbe with a truck intake. Hoping to make about 375 wheel on just motor then spray another 200 wet shot on top of that at the track.
Here's the question: will the stock 22 lb/hr injectors be able to flow enough to handle 375 hp or will I need to upgrade? ive read over and over and the answer never seems to be clear. There are guys that say they've made 400 easily on stock injectors and others that say they maxed them out at 350. Doing the math on the calculator in the sticky of this section, it seems like I would need about a 28 lb injector but that seems like overkill. Other calculators say around a 24 lb is needed. That's at 80% duty cycle.
Also, will a single in-tank 255 pump be able to handle it? I'm confident it could flow enough for just motor but will it be able to handle the nitrous too? Or will I need to step up to a 450?
I'm hoping someone with a similar setup or more experience than me can chime in and help me get some confidence that I won't blow the car up because I lean it out!
The build is an ls swapped fox. It will be an lm7 pulled from a 99 silverado with gen 4 flat tops shoved in place of the dished pistons. 862 heads with the intake valve opened up to 2". 11:1 compression. 226/234 (ish) cam, sbe with a truck intake. Hoping to make about 375 wheel on just motor then spray another 200 wet shot on top of that at the track.
Here's the question: will the stock 22 lb/hr injectors be able to flow enough to handle 375 hp or will I need to upgrade? ive read over and over and the answer never seems to be clear. There are guys that say they've made 400 easily on stock injectors and others that say they maxed them out at 350. Doing the math on the calculator in the sticky of this section, it seems like I would need about a 28 lb injector but that seems like overkill. Other calculators say around a 24 lb is needed. That's at 80% duty cycle.
Also, will a single in-tank 255 pump be able to handle it? I'm confident it could flow enough for just motor but will it be able to handle the nitrous too? Or will I need to step up to a 450?
I'm hoping someone with a similar setup or more experience than me can chime in and help me get some confidence that I won't blow the car up because I lean it out!
The reason for the confusing info is that people quit using HP numbers as a tool, and started using them as an E-*****. Look for "corrected horsepower" numbers in a lot of these instances. When a guy in Denver says he made 500rwhp on stock injectors he means corrected to mile high density altitude. When a guy in Phoenix says he made a 10 second pass on the stock fuel pump, he means corrected for 130 degree weather and a high DA. A single in tank 255 would only flow enough for your needs if you hotwire it to the point of premature failure or you run large enough (think 60#) injectors to flow with a significant pressure drop. Use the calculators wisely, and they will save you many headaches in the future.
