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Old 05-21-2005, 06:55 AM   #1
spoolinsuby
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I was going to search but I didnt know how to word it. How much whp does it take to max out STi pinks, 650cc, modded stocks, 800cc, and 850cc injectors?

Thanks, Frankie
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Old 05-21-2005, 09:11 AM   #2
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It's not HP per se, but the size of the turbo the injectors should go with. State your turbo wants to your Vendor or better yet your tuner and they will recommend the correct size.
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Old 05-21-2005, 11:23 AM   #3
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You can also compare the turbo flow (usually in lb/min to the injector flow, which is normally in cc's)

Just convert CC's to lb/min and you are set. Remember to keep a constant fuel pressure for the calculations, as you can also see what adding 5-10 psi in fuel pressure will do to the overall output of the injectors.
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Old 05-21-2005, 04:53 PM   #4
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For this calculation forget wheel hp, you need to work from the actual engine hp output. Don't work from your turbo flow either as that is not what your really looking for. Your looking for the amount of fuel the engine must burn to make a specific target hp. You size the turbo to supply the amount of air to make that same hp and you have a balanced system. The hp comes first the sizing of the turbo and injectors both follow from the max engine hp output.

For quick calculation purposes just multiply your target wheel hp x 1.25 and that will be the approximate amount of crankshaft hp the engine will need to generate to get to your target.

From there you simply muliply your engine crankshaft engine hp x 0.6 x 10.05 and divide that total by the number of cylinders x .80.

((Engine hp) x 0.6 x 10.05 ) / (number of injectors) x ( duty cycle -- use 0.80 ) = cc/minute flow for each injector.

Example:

You want to make 500 wheel hp. Your engine will need to be able to make about 625 hp to be sure you can do that.

(625 x 0.6 x 10.05 ) / (4 x 0.80) = (3768.75)/ (3.2) = 1177 cc/min for each injector

The 0.6 is the assumed BSFC (lbs of fuel/hour) required to make one hp in a turbocharged engine.
The 10.05 converts the lbs of fuel to cc/min
The 0.80 is the maximum recommended duty cycle of the injectors.

http://www.rceng.com/technical.htm


Larry

Last edited by hotrod; 05-21-2005 at 05:04 PM.
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Old 05-23-2005, 01:06 AM   #5
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thanks for info guys I was just wondering how much power my pinks would be able to flow for and if my modded stockers would be overkill.
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Old 06-06-2005, 04:46 PM   #6
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I've made over 370whp on Pinks with an sz49 and 2.5 hybrid engine. It was definately out of gas up top, but it was good power.
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Old 09-11-2009, 05:11 PM   #7
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Quote:
Originally Posted by hotrod View Post
For this calculation forget wheel hp, you need to work from the actual engine hp output. Don't work from your turbo flow either as that is not what your really looking for. Your looking for the amount of fuel the engine must burn to make a specific target hp. You size the turbo to supply the amount of air to make that same hp and you have a balanced system. The hp comes first the sizing of the turbo and injectors both follow from the max engine hp output.

For quick calculation purposes just multiply your target wheel hp x 1.25 and that will be the approximate amount of crankshaft hp the engine will need to generate to get to your target.

From there you simply muliply your engine crankshaft engine hp x 0.6 x 10.05 and divide that total by the number of cylinders x .80.

((Engine hp) x 0.6 x 10.05 ) / (number of injectors) x ( duty cycle -- use 0.80 ) = cc/minute flow for each injector.

Example:

You want to make 500 wheel hp. Your engine will need to be able to make about 625 hp to be sure you can do that.

(625 x 0.6 x 10.05 ) / (4 x 0.80) = (3768.75)/ (3.2) = 1177 cc/min for each injector

The 0.6 is the assumed BSFC (lbs of fuel/hour) required to make one hp in a turbocharged engine.
The 10.05 converts the lbs of fuel to cc/min
The 0.80 is the maximum recommended duty cycle of the injectors.

http://www.rceng.com/technical.htm
Larry,

Using the referred page for the original formula, I believe your lb/hr to cc/min conversion number should be corrected from 10.05 to 10.50


Les
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Old 09-11-2009, 05:49 PM   #8
Effex Unlimited
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nothing like bumping a 4 year old thread.
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Old 09-11-2009, 06:18 PM   #9
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You're right but I was doing some research and just now came across it. Probably would not have given it much thought but I ran across at least 3 different places online plus several search engine finds that referred me back ot the same thread as a reference so thought if it was being used by so many as a reference, it might be noteworthy to mention that the formula (the biggest reason for all the referrals) probably should be corrected for those who are not paying attention.

Hope I didn't ruffle anyone but I am surprised that it has been here that long and been referred to and no one had caught the error....

Les
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Old 09-11-2009, 06:52 PM   #10
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Good information nonetheless.
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Old 09-11-2009, 06:52 PM   #11
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Quote:
Originally Posted by HillbillyLes View Post
You're right but I was doing some research and just now came across it. Probably would not have given it much thought but I ran across at least 3 different places online plus several search engine finds that referred me back ot the same thread as a reference so thought if it was being used by so many as a reference, it might be noteworthy to mention that the formula (the biggest reason for all the referrals) probably should be corrected for those who are not paying attention.

Hope I didn't ruffle anyone but I am surprised that it has been here that long and been referred to and no one had caught the error....

Les
nahh... didn't ruffle my feathers, just thought it was odd. but good point on making the corrections.
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