Exhaust Calculator .EXE file v 1.31

[A20A1]

Well I've been trying to work out a way to size exhaust pipe using a lot more than previous formulas I've found.
Goals;
Allow the user to find:
- Optimal Velocity of 240-260 FPS
- Optimal CFM for a given RPM and Engine Displacement as well as estimated
horsepower.
- Optimal Pipe Diamter
Inputs will be
- RPM
- C/R
- CID
- Estimated hp
- Dual or single exhaust
The trouble I've had is getting combustion temps and exhaust temps and including the cylinder volumes and pipe volumes and what not.
It's all so inter-dependant... I had a working version 1.0 and it didn't seem enough, and certainly didn't seem to add up, even if it came close.
I need the rest of the values as a means of double checking the work.
Oh and I'm just learning C++, I got the dummies book and I'm on the first project where you convert celsius to fahrenheit, from there I built my code.

[A20A1]

I found this site if it helps... I haven't finished going over it but it looks like it has what I need to complete my program.
http://www.arielcorp.com/ariel.asp?id=465
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More old rules of thumb or calculations from the tool box:
1) Increase pipe diameter of OEM exhaust by 1/4" to 1/2"
2)CID = N x 0.7854 x bore x bore x stroke (all in inches)
3)(CFM = CID x RPM x VE ÷ 3456)
cid * max rpm * volumetric efficiency/3456
119 cid
Okay
for v 1.3 below enter the values here:
119 is our CID
1.75 is the stock Exhaust diameter
the rest is up to you
RPM
and
Estimated HP.

v 1.30
This allows you to use it for any car/engine.
It gets rid of the preset values I added for the accord and allows you to enter those values yourself.
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Had to fix some computational errors... don't forget your "()" kids
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[forrest89sei]

Great job!

cool tool

[2ndGenGuy]

Man, that is some pretty interesting stuff. It seems like a ton of work to get all those calculations right. It's kinda like the Desktop Dyno, but I think they tested it on that show Trucks and turns out it was within 1 or 2hp of the actual dyno. Then again, the results vary by dyno as well... Keep up the good work! I can't run the EXE because I have a Mac. But a link to some source code will keep GCC happy on my computer. Unless you're not into the open source thing, that's cool too. :P

[A20A1]

I posted the C++ code in the first post if you want to copy that.. I dunno if thats what you need?
I made one final update for now so hopefully everyone is getting the right version.

I have desktop dyno as well, it's an old version. The book has some formulas and I plan on incorporating those as well when I find the time.

http://rapidshare.com/files/40183314...LC131.rar.html
Formatted the output some to make it easier to read.
updated the code above to v 1.31

What bothers me is the diameter when you put in values like 1000 HP, 119 CID, 5500 RPM, 1.75" Diameter.

Obviously if you had 1000 HP you wouldn't have a 1.75" diameter to start.
And I don't think 119 CID will make 1000 HP N/A. And this calculator is for N/A only, but still makes me think I need to do better, or make more options in the beginning to just throw out the user input of stock diameter when horsepower reaches a certain level above stock HP.

So far this calculator works well when simply upgrading the exhaust and muffler after adding a few mods.
On low HP low CFM, if I change to code to allow CFM to take over the role of maximum pipe diameter instead of using the stock diameter + 0.5" then I get lower numbers closer to the stock diameter. Only when HP is high and CFM is high do I need to toss out the + 0.5" and the numbers get larger, but since I don't see many of us here above 300 HP N/A I didn't bother uploading the v 1.32.

oh yeah and don't forget to round the numbers, if you round up or down it's up to you.

[CS_05_HHO]

can you help me? when is the final version going to come up? I have a Dacia Logan with a 1.4 liter engine producing aproximatively 82 to 85 horsepower at 5500 RPM and 127 NM torque at 3500 RPM. Can you help me design the diameter of the exhaust so that i could reach at least 130 NM torque and at least 90 Horsepower? The actual diameter of the exhaust is like this:
between the cat and the middle muffler is 45 mm --- 1.77165 inches
after the middfle muffler till the sport muffler is 40 mm --- 1.5748 inches
what would be the optimum diameter for my car?

Bore × stroke 79.50 mm × 70.00 mm
3.13 in × 2.76 in

Compression ratio 9.50:1

[Hauntd ca3]

i think a 2 inch exhaust would be smack on the $$ for a 1.4 liter motor.
to get the best out of any exhaust, you need to go that pipe size right from the collector all the way out
even if you have to replace the cat to do so

[CS_05_HHO]

thank you for the answer Hauntd ca3, but can anyone get a hold of the user A20A1 so i could speak with her? Has she made some improvements on the exhaust calculator?

[CS_05_HHO]

No new updates???

[A20A1]

At the point where I left off I think I was trying to figure out how to add in Forced induction figures since Under boost you can have high HP but low CID. I got the most errors when I tried to add in high HP values with low CID values. So I just need the math to figure out what a certain PSI will do to the stock CID values so that you can just type in CID and amount of boost and it will figure that in an hopefully wont give you a tiny pipe diameter.

It's been way too long to just jump in and edit the code. I don't even remember the compiler I used, but I will try to finish this.

I went here to calculate your CID since I was too lazy to do it manually.
http://www.nightrider.com/biketech/c...splacement.htm

Using the calculator v1.31
It says 1.86" pipe diameter using 84.8 as CID, 1.625" as stock diameter, 82 as your HP, and 5500 as your rpm.

Remember that exhaust isn't the only thing you need to work on to reach your HP/TQ goals.




I tried it again with these values

84.8 CID
85 HP
5500 RPM
1.75" Stock Diameter

I got 1.96" so very close to 2"

What do you plan to do with the Middle Muffler and the Cat?

If I enter the value of your goal HP and use 90 then you get 1.97" diameter.

I've been meaning to dump the whole "Enter stock diameter" line in the code because really it is garbage. I added it as a check and balance against values that might get too far out of range for us daily drivers that aren't pushing more then 200-300 HP.

Looking back at this part in my earlier post I think I came to the same conclusion... I just don't remember what the exact code changes were at the time.

So far this calculator works well when simply upgrading the exhaust and muffler after adding a few mods.
On low HP low CFM, if I change to code to allow CFM to take over the role of maximum pipe diameter instead of using the stock diameter + 0.5" then I get lower numbers closer to the stock diameter. Only when HP is high and CFM is high do I need to toss out the + 0.5" and the numbers get larger, but since I don't see many of us here above 300 HP N/A I didn't bother uploading the v 1.32.