NA Tech Race to 100whp per 1000cc's
- Thread starter LordWorm
- Start date
yeah man... heres the math.....
first you need to get your EVCD (effective valve closed duration)
EVCD = 720 - (intake cam duration - 30)
30 is a correction factor, and you can play around with that...the paper i have on the subject says:
Once you've got your EVCD, the formula for calculating the length of the runners is:
L = ((EVCD * 0.25 * V * 2) / (rpm * RV)) - 0.5 * D
Where RV is the reflective value (i.e. the order of the reflection you will use... 3 is a good number... 1 gives best power but you're runners will be insanely long), V = pressure wave speed (you can google for working out the speed of sound at a given air temperature), and D is runner diameter.
If possible., you taper your runners by between 1.7% and 2.5% to help force the air in..this is only possible with straight runners, and the trade off might be increasing the RV.
Next you work out the length of the ram pipe (intake pipe) and diameter of the pipe/throttlebody.
To do that...
D = SQRT(CID * VE * RPM) / (V*1130)
where CID is Cubic inch displacement
VE is volumetric effeciency
RPM is Revolutions per minute
and V is velocity in ft/sec (180ft/sec is the number you should use)
That gives you the diameter of your intake pipe, and the size of your throttlebody (allow a bit of extra cross sectional area to make up for the throttle plate width)
Ram pipe length will be 13" long for 6000rpm. For each 1000rpm drop add 1.7", for each 1000rpm increase, subtract 1.7"
plenum volume for a 4 cylinder is about 50 - 60% of total cylinder displacement for 6000rpm.... decrease the size of the plenum by 10 - 15% for every 1000 to 1500 rpm increase in the rpm you want the boost to occur.
Of course, you can "stack" the results...you can have the peak boost for the plennum earlier than the ram pipe, and that earlier than the runner hits - this helps broaden the curve and improve response - or you can have them all come on at the same RPM, which benefits top end power, but sacrifices velocity and breathability at low RPM.
It is entirely possible with a well tuned intake manifold to see 4 to 7psi of positive pressure at the valve on a naturally aspirated engine...thats right - BOOST on an NA motor....
Experimentation is the key... designing a manifold that allows you to try different tuned intake pipe lengths, and different plenum volumes is preferable to building something entirely on paper and hoping it will work.....
- :
- 03.5 YLW MSP
um.... yeah that makes my head hurt just a little. lol
hahaha...
engineering maths = fun
that stuff is relatively simple... try working out VE from BSFC and power, or determining runner length for headers, or working out dynamic compression given a cam profile and static comp
the joys of NA tuning..... its like being back in school
- :
- 02' Protege ES (Gone)
16' Mazda 6 sport manual
But At least learning this will yield some actual results
- :
- 03.5 YLW MSP
hahaha...
engineering maths = fun
that stuff is relatively simple... try working out VE from BSFC and power, or determining runner length for headers, or working out dynamic compression given a cam profile and static comp
the joys of NA tuning..... its like being back in school
well I sucketh at math! lol
- :
- 03' Mazda Protege 5
Yah, I don't know the math to design one myself or I would have done so a while ago
I'm working on a little spreadsheet (by little, i mean enormous...) which compiles all of the engineering papers and little formulas i've collected over the years into one easy to use cheat sheet.
Reason is i've been getting asked the same sorts of questions in everyones build threads, and in other places, so i thought it would be prudent to put everything I know into a nice little tool for everyone to use.
It'll be a little while before it is finished, but so far i have put in:
Basic engine information (bore, stroke, rod length, rod ratio, piston speeds, etc etc)
A detailed quick sheet for working out your intake manifold requirements
A basic fuel injector requirement sheet (this needs some work, but given thats its 4am i haven't done enough thinking about how and what needs to go here)
and Piston Kinematics (soon to have fancy graphs) which will show piston speeds, piston acceleration, rod angularity and perhaps most importantly the force of sideloading on the cylinder walls.
I'm going to try and hunt down some uber calcs for exhaust systems, as well as some cam related doohickies....
I've got some nice VE calcs that can go in too
I'm also going to chuck in the turbo calcs, as well as nitrous jetting calcs, simply because I have them here and might as well put them in....
Ditto for my gearing/tire size calcs.
I'm also going to put a glossary of terms in the back of it.
If there is any more bits of math you want me to chuck in, feel free to let me know...i'll be putting the sheet out under the creative commons license and posting it up here for everyone to use....
Reason is i've been getting asked the same sorts of questions in everyones build threads, and in other places, so i thought it would be prudent to put everything I know into a nice little tool for everyone to use.
It'll be a little while before it is finished, but so far i have put in:
Basic engine information (bore, stroke, rod length, rod ratio, piston speeds, etc etc)
A detailed quick sheet for working out your intake manifold requirements
A basic fuel injector requirement sheet (this needs some work, but given thats its 4am i haven't done enough thinking about how and what needs to go here)
and Piston Kinematics (soon to have fancy graphs) which will show piston speeds, piston acceleration, rod angularity and perhaps most importantly the force of sideloading on the cylinder walls.
I'm going to try and hunt down some uber calcs for exhaust systems, as well as some cam related doohickies....
I've got some nice VE calcs that can go in too
I'm also going to chuck in the turbo calcs, as well as nitrous jetting calcs, simply because I have them here and might as well put them in....
Ditto for my gearing/tire size calcs.
I'm also going to put a glossary of terms in the back of it.
If there is any more bits of math you want me to chuck in, feel free to let me know...i'll be putting the sheet out under the creative commons license and posting it up here for everyone to use....
- :
- 03' Mazda Protege 5
^^^That would help so much! Thanks!^^^
Heres a teaser...
its nowhere near finished, and i haven't checked the math, so seriously - USE AT YOUR OWN RISK!.
But it'll give you an idea of what i'm going for....
I can't actually license the work because it falls under "factual work", and "idea"...
only reason i WANTED to license it was so i could get a "share and share alike" thing happening...But in the absence of being able to do that......
if you find something wrong, or figure a way of improving the sheet, please don't keep it to yourself. Post it up here for all the NA guys (and others) to enjoy).
Things still to be added: Exhaust stuff, some more fuel stuff, some more piston and rod stuff (such as calculating required fuel types for given piston speeds etc) - as well as NOS and turbo calcs.
DO NOT USE THE EXHAUST RUNNER LENGTH CALC - I have just rechecked the formula and it is way way wrong.
other than that...enjoy.
its nowhere near finished, and i haven't checked the math, so seriously - USE AT YOUR OWN RISK!.
But it'll give you an idea of what i'm going for....
I can't actually license the work because it falls under "factual work", and "idea"...
only reason i WANTED to license it was so i could get a "share and share alike" thing happening...But in the absence of being able to do that......
if you find something wrong, or figure a way of improving the sheet, please don't keep it to yourself. Post it up here for all the NA guys (and others) to enjoy).
Things still to be added: Exhaust stuff, some more fuel stuff, some more piston and rod stuff (such as calculating required fuel types for given piston speeds etc) - as well as NOS and turbo calcs.
DO NOT USE THE EXHAUST RUNNER LENGTH CALC - I have just rechecked the formula and it is way way wrong.
other than that...enjoy.
- :
- 02' Protege ES (Gone)
16' Mazda 6 sport manual
Thats nice.......!!!
what is BSFC?
I punched in some numbers and it said I needed 112% VE Required To Achieve Target HP. My target was 325 crank HP (250 whp) with a KL V6 (84.5 bore x 74.2 stroke), rod length 137.8204, and max engine speed at 9000 rpm.
I put in 325 for HP to account for about a 23-25% driveline loss with a target of 250whp.
I punched in some numbers and it said I needed 112% VE Required To Achieve Target HP. My target was 325 crank HP (250 whp) with a KL V6 (84.5 bore x 74.2 stroke), rod length 137.8204, and max engine speed at 9000 rpm.
I put in 325 for HP to account for about a 23-25% driveline loss with a target of 250whp.
- :
- 02' Protege ES (Gone)
16' Mazda 6 sport manual
Brake Specific Fuel Consumption
Last edited:
- :
- 02' Protege ES (Gone)
16' Mazda 6 sport manual
I'd suppose, like Lordworm said positive boost pressure is possible with the right tuning. So I guess that would be considered above 100% efficiency.
112% may be pushing it....but its not out of the question. you'd need a decent tunnel ram intake manifold....or some kickass IRTBs. But over 100% VE is quite possible on an NA build, and guys have taken the KLZE to these kinds of numbers before.
try the formula with a BSFC of 0.45. Highly strung motors will probably be more accurate with this figure....remember, that is required VE as max power and max RPM... the highest VE in the curve occurs at MAX TORQUE.... so you may need 118% odd VE ... the next version of the spreadsheet will allow you to plot the VE curve based on data from a dyno....
I'll add the glossary as promised for the next version too.
IF anyone has any more suggestions about anything, give me a yell via pm.
The piston kinemetics is probably the most interesting bit thus far...you can see the effect of an altered rod ratio on the piston traveling through its complete journey, from TDC to BDC and back to TDC again.
try the formula with a BSFC of 0.45. Highly strung motors will probably be more accurate with this figure....remember, that is required VE as max power and max RPM... the highest VE in the curve occurs at MAX TORQUE.... so you may need 118% odd VE ... the next version of the spreadsheet will allow you to plot the VE curve based on data from a dyno....
I'll add the glossary as promised for the next version too.
IF anyone has any more suggestions about anything, give me a yell via pm.
The piston kinemetics is probably the most interesting bit thus far...you can see the effect of an altered rod ratio on the piston traveling through its complete journey, from TDC to BDC and back to TDC again.
Last edited:
hahaha - COULD THIS BE.....
A darksider considering coming back to the NA crowd?
what have we come to
nah man, good luck with it...
the KL certainly looks like the best option....I'm hooked on the FS because so few people give it love....but i whole heartedly recommend the KLZE because not only is it going to get the target easier, its going to out perform the FS in just about every way shape and form...
i'm like Darth Vader at the end of episode VI
your going to sacrifice yourself to take out the head of the dark side before you show us your face which doesnt look anything like the previous episodes?? awesome...
well i hope you do so i dont get seduced by it...
well guys, i'm pretty close to buying the motor... ive saved up enough!!
there are people who didnt think it was possible to the swap in this forum... we need to advertise!
LW: amazing work on that sheet, cant wait to see the finished product
