What Size Exhaust Tubing for how much boost? (1.8)
 

I'm not sure if I can't find it our theres not sticky post?

Is there like a common knowledge for a certain amount of boost/hp for a certain size exhaust. Like Oh a slapon greddy kit is fine with 2.5".

A begi pushing doubled that HP needs 3".. etc..

3" or greater

3" with large free flow muffler- non turbo.

3" with large free flow muffler- low boost turbo/super charger 5-10lbs

3" with large free flow muffler- higher boost levels 12-xxlbs

These are rules to live by.

With a turbo do not go less than 3" from the turbo straight to the back of the car if at all possible. Anything less is a compromise in spool and power.

Just go 8"

Can't go wrong with 8"

https://www.miataturbo.net/dynos-tim...exhaust-64145/ :party:

Miater, i had to fix your flawed post.

lololol

Does Fae really believe your 3" is 8"?

bullshit.


my BEGI 2.25" to 2.5" DP, to 2.25" cat, to 2.25" borla exhaust

to the same Begi 2.25" to 2.5" DP, 3" cat, and 3" catback:

https://www.miataturbo.net/attachmen...ine=1356112243

same dyno. same boost*.



*was getting creep, so i lifted.

Oh now you've gone and done it: Brain will school you

ah, to be fair he does say he's running less boost.

I know I'm in the minority here but does the exhaust size recommendation stay the same for supercharger applications as well or is there something different? Thanks.

bigger is always better.

just sound like absolute shit on a SC.

The only reason to not do a 3" exhaust on a turbo car is because you can't afford it AND you're too lazy to build one yourself.

N/A cars should get 2.25" straight-through systems.

Lol, don't hate at me bro! Its not my data and its the only comparison I could quickly find.

Your results are obviously better. I believe Curly has something similar going from his Frankenstein exhaust to a 3" ARTech? Couldn't find it quickly.

Ironically, I'm using Cordus old catted 2.5" FM turbo exhaust on my NB with the Rotrex and an BP6D exhaust manifold and factory downpipe. It's less than ideal, but it works for now. I will eventually be replacing manifold with a RB unit and the muffler with a 2.5" Magnaflow 5x11x22 because the ancient FM muffler has definitely seen better days. It's actually significantly quieter than expected, but it rasps on throttle stomps.

Turbo cars are much more sensitive to the exhaust size because the turbine acts as a backpressure multiplier.

The considerations for a SC car are different and more like doing the exhaust for an NA car (taking into consideration some additional flow). Things like sizing the pipe diameter and length to promote scavenging become important. Bottom line, on an SC car run a good header and an exhaust system matched to the header. That will likely be smaller than a 3".

^^ This. Everything I've read backs this up. The only person with an SC setup that I've seen that is running anything bigger is TrackDayHooky. At one point he was running one of the discontinued 949Racing 2.75" exhausts on a 400+HP C38 Rotrex build. No clue what that car has on it now.

Ok, back to the trubo stuff. Who has more apples to apples comparison data for exhaust upgrades?

curly posted a dyno log thing not too long ago.

For turbo exhaust you want a Choad

Short as possible and wide as possible.

My 4" isnt that loud. Very deep though. Balls deep

FM 2.5" DP + old (~ 2002) FM 2.5 midpipe & muffler (with ceramic cat) vs FM 2.5" to 3.0" and (current-gen) full 3.0" exhaust:

Different dynos (both the same model of dynapack, tho), and ~ 10 kpa less boost with the new exhaust, which explains the lower torque in the midrange. (sorry, the boost controller isn't as consistent as I wound like). The increased spool and top end is very evident, however.

http://www.codrus.com/dyno/agp/ian-power.png

Sorry about the colors, I blame the dynapack software.

--Ian

So not actually all that deep.:giggle:

yeah ok.

that's why you said literally the exact opposite multiple times in your threads:jerkit:

lol spool

I think you mean flow.

But yeah, that shows the results perfectly: faster spool and more topend flow. And you can easily bump boost in the midrange as well as timing and make way more torque and be less det limited.

This is one of those rare times I agree with Fae: the bigger and the shorter, the better.

well fine it is louder than god but loudness increases with the amount of air being pushed through your engine.

I also have a muffler through which you can roll a tennis ball. that enloudens it

Shouldn't that technically "delouden" it?