ClubRoadster.net banner

1 - 20 of 75 Posts

·
Registered
Joined
·
103 Posts
Discussion Starter #1
Hi guys.

Does anyone know or have a formula for calculating the optimum exhaust size?

I’m talking exhaust I.D

Power gained and just the right back pressure.
(There are arguments on whether back pressure is good or bad also)

What size ID against the amount of horse power you’re chucking out and the size of your engine (if relevant)

Eg. You wouldn’t but a 3” pipe on a 1ltr 50bhp micra or something. The optimum size would be a lot smaller. Like 1.75” or 2” but how do you actually figure it out?
What’s the maths behind it?

Thanks
 

·
Mufasa in Training
Joined
·
31,471 Posts
There is no magic formula, if for no other reason than it has to take in your ability to deal with noise and, especially, droning.

Basically, 2.25-2.5" n/a, 3" turbo.

/thread
 

·
Registered
Joined
·
103 Posts
Discussion Starter #3
There is no magic formula, if for no other reason than it has to take in your ability to deal with noise and, especially, droning.



Basically, 2.25-2.5" n/a, 3" turbo.



/thread


And engine size and power doesn’t matter?

I heard that for example
exhaust A is good for upto 150bhp
Exhaust b is good for upto 200bhp

And so on...

What is the reason behind having a bigger exhaust for a blown engine against N/A?


Sent from my iPhone using Tapatalk
 

·
Administrator
Joined
·
15,155 Posts
No formula. Look at what people are doing successfully. Use brain. Do what you think is right from there.

No n/a BP needs bigger than 2.5". Turbo cars like 3" minimum.

K series, rotaries, actual good motors, benefit from 3" even n/a.

This is the year 2018, we don't need to have a discussion about backpressure. It's not a thing.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #5
No formula. Look at what people are doing successfully. Use brain. Do what you think is right from there.

No n/a BP needs bigger than 2.5". Turbo cars like 3" minimum.

K series, rotaries, actual good motors, benefit from 3" even n/a.

This is the year 2018, we don't need to have a discussion about backpressure. It's not a thing.


You said no N/A motors need bigger than 2.5 then listed N/A motors that run 3.




Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
103 Posts
Discussion Starter #6
No formula. Look at what people are doing successfully. Use brain. Do what you think is right from there.

No n/a BP needs bigger than 2.5". Turbo cars like 3" minimum.

K series, rotaries, actual good motors, benefit from 3" even n/a.

This is the year 2018, we don't need to have a discussion about backpressure. It's not a thing.


With 2.5 in mind for a big engine, high power N/A engine. Is that ‘too big’ for a standard ish 1.6cc eunos? Will it lose out or benefit?


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
509 Posts
You said no N/A motors need bigger than 2.5 then listed N/A motors that run 3.




Sent from my iPhone using Tapatalk
He said NO N/A BP Motors need anything bigger, which means that an N/A miata does not need anything bigger.
 

·
Registered
Joined
·
509 Posts
I assumed he meant bhp not bp engine.

Why do I now have a bp engine?


Sent from my iPhone using Tapatalk
See how providing SPECIFIC information helps out? Are you from outside of the US because I really believe that there is a communication gap here?
 

·
100% Jakedashian
Joined
·
6,599 Posts
You said no N/A motors need bigger than 2.5 then listed N/A motors that run 3.
No NA Miata motor needs bigger than a 2.5 because our little sewing machines have the specific power output of a hamster.

With 2.5 in mind for a big engine, high power N/A engine. Is that ‘too big’ for a standard ish 1.6cc eunos? Will it lose out or benefit?
It will be more expensive, harder to fit, and probably sound like doodoo while providing no benefit.

When I had a 1.6 my exhaust rusted off and for a brief while I had every exhaust configuration imaginable. Open stock header? Yup. Stock header with 3" glasspack and turnout? Yup. Stock header with 2.5" Buick muffler? Yup. eBay header? Yup. eBay header with a new OEM exhaust? Yup.

Did any of it make any change whatsoever to how my engine ran or how much power it produced? Nope. The only change was how much I hated my life due to the noise.

Feel free to disregard the combined knowledge of a full forum and put a straight 4" pipe on your exhaust. It'll sound great and get much swags/****.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #15
See how providing SPECIFIC information helps out? Are you from outside of the US because I really believe that there is a communication gap here?


You mean like in the post right after?
Not really. Why do you need to know what size my engine is to answer my question?
The only reason anyone has specified any engine before I said what mine was, was to try and have a bit of banter I guess. Not that it went very well
From earlier threads he’s replied on he knows that my engine is a 1.6 so why would I think he was trying to tell me how much power a 1.8 can have?
I obviously thought it was a typo coz why would you intentionally give someone useless info then make look silly by commenting asking if someone can read.
Oh I do love this forum


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
103 Posts
Discussion Starter #16
No NA Miata motor needs bigger than a 2.5 because our little sewing machines have the specific power output of a hamster.







It will be more expensive, harder to fit, and probably sound like doodoo while providing no benefit.



When I had a 1.6 my exhaust rusted off and for a brief while I had every exhaust configuration imaginable. Open stock header? Yup. Stock header with 3" glasspack and turnout? Yup. Stock header with 2.5" Buick muffler? Yup. eBay header? Yup. eBay header with a new OEM exhaust? Yup.



Did any of it make any change whatsoever to how my engine ran or how much power it produced? Nope. The only change was how much I hated my life due to the noise.



Feel free to disregard the combined knowledge of a full forum and put a straight 4" pipe on your exhaust. It'll sound great and get much swags/****.


Wow you spent a lot on parts.


Sent from my iPhone using Tapatalk
 

·
Administrator
Joined
·
15,155 Posts
I assumed he meant bhp not bp engine.

Why do I now have a bp engine?


Sent from my iPhone using Tapatalk
I didn't know what you had because you didn't tell me. I said BP, not "bhp." Those are different things and i'm not fan of using my shift key for things that aren't actually capitalized.

Using logic, you can still get the answer you desire from the statement i made. N/A BPs of any kind don't need anything bigger than 2.5". Your B6 is like a BP, but way worse, so it also doesn't need anything bigger than 2.5".

Any difference in bhp (whoa! does this ACTUALLY mean BP engine? Nobody knows!) in a B6 between 2" and 2.5" is probably just noise.
 

·
Administrator
Joined
·
15,155 Posts
You mean like in the post right after?
Not really. Why do you need to know what size my engine is to answer my question?
The only reason anyone has specified any engine before I said what mine was, was to try and have a bit of banter I guess. Not that it went very well
From earlier threads he’s replied on he knows that my engine is a 1.6 so why would I think he was trying to tell me how much power a 1.8 can have?
I obviously thought it was a typo coz why would you intentionally give someone useless info then make look silly by commenting asking if someone can read.
Oh I do love this forum


Sent from my iPhone using Tapatalk
It's not banter. I gave extremely clear information that anyone with an IQ surpassing that of eggplant would have been able to come to a conclusion with.

But because you decided to be a child, NOW we're having banter.

Keep treating this place like your personal Google Machine and then arguing with the helpful information that you're given and you'll find your stay truncated.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #19
It's not banter. I gave extremely clear information that anyone with an IQ surpassing that of eggplant would have been able to come to a conclusion with.

But because you decided to be a child, NOW we're having banter.

Keep treating this place like your personal Google Machine and then arguing with the helpful information that you're given and you'll find your stay truncated.






Sent from my iPhone using Tapatalk
 
1 - 20 of 75 Posts
Top