quote:

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Originally posted by st5150:
No need for a fuel cell or bigger pump. I'll do the math for 42 lbs injectors at ~40 psi later, but I can already make a good guess that you'll be fine as-is.

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Why no need for a fuel cell? Do you know what he plans on doing with the car(roadracing, street/strip, or drag racing ect..)?

Don't forget to use the "real world load" function on your calculator when you enter your formula.
 

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Posted by 66 AC COBRA of CA PERFORMANCE (Member # 904) on :
 
im getting a cell because i am more than likely gonna backhalf the car, i know that its way over kill but i want to run a very tall tire for looks not performance, plus i think havin a 32X14 tire will be fun on the street

and bounty hunter, u dont think that a 150 shot plus a 427 stroker would require more than a 255 intank pump
 

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Posted by Jeff S (Member # 371) on :
 
66 AC COBRA of CA PERFORMANCE,

IMO your 427 stroker by itself will need more than a 255lph pump if you make ~550rwhp.
 

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Posted by Jeff S (Member # 371) on :
 

quote:

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Originally posted by st5150:
No need for a fuel cell or bigger pump. I'll do the math for 42 lbs injectors at ~40 psi later, but I can already make a good guess that you'll be fine as-is.

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I forgot to add you need to account for RPM in your calculation also.
 

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Posted by BOUNTY HUNTER VERT (Member # 2754) on :
 

quote:

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Originally posted by 66 AC COBRA of CA PERFORMANCE:
im getting a cell because i am more than likely gonna backhalf the car, i know that its way over kill but i want to run a very tall tire for looks not performance, plus i think havin a 32X14 tire will be fun on the street

and bounty hunter, u dont think that a 150 shot plus a 427 stroker would require more than a 255 intank pump

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quote:

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Originally posted by 7.3L White Whale:
did u buy 7liter's engine (kevin aka 98svtcobra)?

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quote:

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Originally posted by st5150:
Jeff S- RPM isn't a factor in any of the equations to calculate fuel requirements. You must have mistaken this post with another.


66 AC Cobra of long_name- 550 rwhp? I've seen a 429ci 351w based motor with CNC ported Brodix track 1's make 475 rwhp with 42lbs injectors. I'll do the math for 550 rwhp...... but I have a feeling by the time you put this combo together, your mechanical engineering classes will get in the way of toys like this.

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quote:

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Originally posted by st5150:
Jeff S- RPM isn't a factor in any of the equations to calculate fuel requirements. You must have mistaken this post with another.

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Do you know anything about injector duty cycle? How about you look at this graph and then get back to me with any questions.

http://www.ecanfix.com/~mdhamilton/dutycycle1.html

[ August 30, 2003, 02:13 AM: Message edited by: Jeff S ]
 

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Posted by stoauto (Member # 2803) on :
 
550 RWHP i'm not doubting you at all man but damn
 

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Posted by st5150 (Member # 51) on :
 
Jeff S- This is getting too funny. You don't even know what the term "duty cycle" means in simple terms. They didn't cover it in the few quarters of junior college you attended before you dropped out. At any RPM you can have any injector duty cycle if you wish. They're not related in any way by definition.

Again I state: RPM has nothing to do with calculation fuel requirements. This is beyond obvious why. Please stick to custom cam posts where at least you can bring up RPM into the discussion, and talk about "area under the curve", yet another topic which you don't completely understand nor know how to calculate since they....yup, didn't cover in your few quarters of junior college education.

If you want a quick and dirty lesson on the techniques discussed above, please feel free to PM me, but lets not clutter bring into this post.... just PM me.

[ August 30, 2003, 11:23 AM: Message edited by: st5150 ]
 

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Posted by st5150 (Member # 51) on :
 
66 AC COBRA of long_name: 255 lph will provide enough fuel flow to support 550 rwhp on that motor. If it truely makes 550 rwhp, that'll be about 1.3 rwhp per cubic inch.... so far for a NA motor, Mike Camara holds the rwhp per cubic inch record with a tad over 1.2rwhp per cube. So after putting things in perspective..... crazy efficient NA motors like that tend to make more rwhp per same quantity of fuel. The BSFC goes down in other words. Maybe to 0.45 or so. Keeping BSFC at 0.5, and all the other variables the same as above, but using 42 lbs injectors at 40 psi, you'll be very safe to 500 rwhp. Keep those 42 lbs injectors, but calculate a drop the BSFC due to the motors super efficiency and you'll have plenty of fuel for 550 rwhp. Keep in mind that the injectors were never pushed past 85% duty cylce in these calculations. So like Bounty Hunter vert said: run what you have since it sounds fine, and if on the dyno you find out otherwise, upgrade the restricting part of your fuel system.
 

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Posted by 93PONY (Member # 60) on :
 
RPM has nothing to do with fuel requirements??? LOL
Riiiight.
So an injectors pulse-width at 6000rpm can be as long as when the motor is running at 1000rpm. Riiiight.
Max pulse-width for ANY injector at 1000rpm can be 6 times what it can be at 6000rpm. I do think this plays a factor in selecting the correct fuel system. RPM directly affects max pulse-width of an injector. Choose too small of an injector & you will go lean at high RPM's where the injector is basically open 100% of the time, but still not keeping up with the demand for fuel. Sure...an easy way to band-aid this is to add fuel pressure, but then the demand for more pump increases.
 

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Posted by st5150 (Member # 51) on :
 
93PONY - If you have any surpressed displeasure with me for not being impressed with any of your combos, please don't take it out by starting arguements with me on every and all posts I reply to. Just PM me with your displeasure and get it out of your system that way instead of cluttering up this forum.

With that said, sure, you can have the injector pusle width be the same at 1K RPM and 6K RPM. Why can't it? The width of the pulse doesn't affect duty cycle, again by definition of the terms. Two signals with completely different duty cycles can have the same 'on pulse width'. The reasons why are very elementry and basic. I'm sure 66 AC Cobra has covered this topic and understands it.

I don't know what more to say.... I just ask that if you or Jeff S want to argue with me about this, please just PM me instead.
 

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Posted by 66 AC COBRA of CA PERFORMANCE (Member # 904) on :
 

quote:

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Originally posted by st5150:
I'm sure 66 AC Cobra has covered this topic and understands it.

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if by this u mean that i dont know what i am reading in this post, u are mistaken, i have done some injector calculating with this motor and that is why i am sticking with the 42's, because 42's have a much better track record that 50's, and i like ford injectors, and ford doesnt make 50's, and if u did mean disrespect to me with the above comment u might have another person that doesnt like ya to much, u think u are god because ur in college, im in college, shaun, i dont know, but hes smart as fuck, and jeffs is makin 600rwhp on a 331, so he is slightly qualified too, and just because someone has a different view than u, doesnt mean they hate u, it means they have a differnt opinion
 

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Posted by st5150 (Member # 51) on :
 
Scroll up and read what I typed again.... I said I'm sure you understood what duty cycle is because this basic topic is covered in your second or third quarter physics class at your school, if not highschool.
Go ahead, scroll up, its clearly written up there.

[ August 30, 2003, 01:40 PM: Message edited by: st5150 ]
 

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Posted by 66 AC COBRA of CA PERFORMANCE (Member # 904) on :
 
well then its cool, but usually u have nothing good to say about someone who usually sides with shaun
 

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Posted by Jeff S (Member # 371) on :
 
Class is now in session.

Take the following facts and draw your own conclusion:

Duty cycle is the proportion of time during which a component, device, or system is operated. The duty cycle can be expressed as a ratio or as a percentage.

Duty cycle when refering to fuel injectors is the amount of time, in a percentage, that an injector is "open" relative to the amount of AVAILBLE time for the injector to be "open".

In a sequential system, which fires one injector after another, the injector fires once per intake valve event(1 combustion cycle or 720* of crank rotation or 360* cam rotation).

At a given RPM there is only a specific amount of time in which the injector can fire per intake valve event(IVE). Lets use 6000rpms for example:

At 6000rpms there are 3000 IVE's per minute.
So... there are 3000 IVE's in 60 seconds.
Or...300 events in 6 seconds...50 events in 1 second which if you keep doing the math gets you to 1 IVE per .02 seconds which is the same as 20ms(milliseconds).

This means that there are 20ms between IVE's. If the injector fires for 10ms per IVE that means that it is at 50% duty cycle. If the injector remains open the entire 20ms it is at 100% duty cycle.

This is what Sawson doesn't understand. If at 6000rpms there are 20ms of time bewteen IVE's you have less time for the injector to potentially fire then you do at 3000rpms. This is because at 3000rpms there is twice the amount of time for the injector to be open(40ms) between IVE's. And at 8000rpms there is less time for the injector to be open(15ms). Therefore if you have a motor that makes 400hp at 6000rpms it will not need as large of an injector flow rate as an engine makeing 400hp at 8000rpms.


ANY QUESTIONS?
 

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Posted by 98slowhoe (Member # 895) on :
 
Wow Jeff your Hecka Smart man! I think after reading that about 5 times I actaully got it. I don't know much about that stuff but you sounded like you are right.
 

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Posted by 93PONY (Member # 60) on :
 
Thank you Jeff.
Maybe the idiot in this thread will now understand. Sure as hell doesn't take a genious to figure this shit out.

Sawson,
If I have something to PM you about....I will. Untill then I will continue to post relevant tech where I see fit.
 

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Posted by AaronC (Member # 86) on :
 
Sawson- Can I recommend you stay to the text books, because tech is obviously not your game Stick to what you know... The stock motor
 

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Posted by ON N2O (Member # 2067) on :
 
off to street racing
 

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Posted by MR GO FAST (Member # 2088) on :
 

quote:

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Originally posted by ON N2O:
off to street racing

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Posted by hidnn.o.s. (Member # 1219) on :
 

quote:

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Originally posted by AaronC:
Sawson- Stick to what you know... The stock motor

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Posted by Calightning (Member # 853) on :
 
Im a dumbass with a Lightning and even I knew that.

[ August 30, 2003, 11:20 PM: Message edited by: Calightning ]
 

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Posted by ON N2O (Member # 2067) on :
 
ttt
 

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