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Old February 27th, 2007, 10:21 PM   #1
landrollover
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Default Anyone here good with microsoft excell? need some help with formulas for dyno class

Hey everyone, i have a project for dyno class where I have to try to make the most horsepower out of a 400cid engine with the powercurve flatlining or dropping at 6000rpm. using dyno 2000 software. it cannot make more power over 6000rpm. Im using excell to try to come up with as many combinations for 400cid as possible. I know it can chage everything with the size of the bore and the stroke. So what im trying to do is come up with the formulas to plug into excell that will alow me to see combinations that come up with 400cid or less. All i have so far is the cid formula( # cyl * 0.7854 * bore * bore * stroke) anyone got any ideas for forumlas. I have a chart with three colums bore, stroke and cid. thanks-Nick
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Old February 27th, 2007, 10:23 PM   #2
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rovers.....
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Old February 27th, 2007, 10:29 PM   #3
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Here are some equations. I think most of them are right.

Cfm=(rpm*cid)/3456*VE


VE= volumetric efficiency


HP= (torque*rpm)/5252


Power from mph= horsepower=weight*(velocity/234)cubed


Required cfm=(CID*RPM*VE0/2820


VE=(Actual CFM*1728)/CID*RPM


CID=Number of cylinders*.7854*bore*bore*stroke


Compression height= Subtract deck height - (stroke divided by 2) - rod length


CR=(D + PV + DC + G + CC) / (PV + DC + G + CC)

CR = Compression Ratio

D = Displacement

PV = Piston Volume

DC = Deck Clearance Volume

G = Gasket Volume

CC = Combustion Chamber Volume



ET = ((Weight / HP)^.333) * 5.825


Gear ratio = rpm x tire diameter /Mph x 336

Mph = rpm x tire diameter /Gear ratio x 336


piston speed in fpm = stroke in inches x rpm / 6
rpm = piston speed in fpm x 6 / stroke in inches
HP from headflow =.2575*cfm*number of cylinders33
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Old February 27th, 2007, 11:08 PM   #4
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if you use desktop dyno you can run the iterator for boreXstroke and it will help you find a combination that will work. ask me tomarow if you dont know what im talkin about, ill be at that trail run.

Last edited by GMCsonoma94; February 27th, 2007 at 11:12 PM.
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Old February 27th, 2007, 11:34 PM   #5
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if you use desktop dyno you can run the iterator for boreXstroke and it will help you find a combination that will work. ask me tomarow if you dont know what im talkin about, ill be at that trail run.

Ive used the iterator. ahh you just gave me an idea, thanks bud
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Old February 27th, 2007, 11:40 PM   #6
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I wish I still had my file for that class. I can't remember my peak HP, but I was within the top 10 in the class.
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Old February 28th, 2007, 12:04 AM   #7
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I wish I still had my file for that class. I can't remember my peak HP, but I was within the top 10 in the class.
nice, im at about 642 right now, my buddie has 680 so i have some things i still need to mess with.
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Old February 28th, 2007, 11:11 AM   #8
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nice, im at about 642 right now, my buddie has 680 so i have some things i still need to mess with.
The high for our class was high 800's or low 900's. It wasn't practical at all though, because the HP curve on the graph jumped around all over the place.
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Old February 28th, 2007, 11:35 AM   #9
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what was the rpm limit for your class, supposidly hes changing it each year?
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Old February 28th, 2007, 12:27 PM   #10
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what was the rpm limit for your class, supposidly hes changing it each year?
I think it was 6000 for us too.

I remember the engine that won was wither a V10 or V12. It was pretty close to being square (bore = stroke) too. Play around with cam timing. You will be able to gain more HP doing that than anything else on that program.
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Old February 28th, 2007, 02:02 PM   #11
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ahh, ive been messing with the 12 not the 10. but my stroke has been really small.
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Old February 28th, 2007, 02:10 PM   #12
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Rolf - excell is not where it's at


You need to use the iderator on the dyno program....I used it extensively and IIRC my engine was the top one of the three classes.....I'm going to check to see if I've still got my file....


Edit....our assignment was different than yours - we were limited at 350 cid and a 1000 cfm max induction flow, along with the fact that it had to be N/A....

Again, All I can say is you have to use the iterator, and it's all about cam shafts.....I'd set mine up and let it run while I went to class....

but honestly, I see zero need for excell on this project....have you already had 310?? If so, you should know about bore/stroke and rod/stroke combo's and where the power is made with them as far as RPM range goes.....since you don't want power over 6000 rpm, you don't want some short stroke screamer that rev's to the moon......

Last edited by chris1044; February 28th, 2007 at 02:19 PM.
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