'hey so im bored and i have decided to rip my exhaust out of my 1983 245 b23f
err well i already did. . . what size exhaust should i put back in to get optimal performance?
yes i know it is a non turbo non performance engine i dont care i will be putting in a header (made by my self) and full exhaust
im not just going to throw in 3.5" monster pipes out the roof or something ridiculous i just want to get the most out of my b23f with a little bit more sound

i have a b21ft muffler and tail pipe which seems to be 2.5"
now i was thinking of doing 2.5" from the header back
with 1.5" header primaries
any thoughts or comments?

 

I doubt you'll get one more HP out of a stock engine with exhaust mods

 

im well aware of this fact pierce. im not building a race car im putting exhaust on a N/A volvo. I am mostly building an exhaust system for practice also because im bored. iv never built an exhaust system before: headers, collector, etc.

so i was wondering what sizes people have used on their volvos and the results

 

i also plan on other mods nothing extreme i would like to keep the stock engine. vx cam, maybe a t5 trans, port and polish

 

I bet you can get up around 200 or 250HP without changing the stock exhaust (turbo, cam, high flow injection, etc)... the stock systems on these cars flow really well....

lets see... intake airflow at wide open throttle for an NA engine is displacement/2 * RPM, or 2.3L/2 * 6500RPM == 124 liters/second. if we assume exhaust gasses are at 1800F (not unreasonable for WFO), the exhaust flow is around 5 times the intake flow (higher if the intake air is colder, lower if its hotter), so lets say about 1000 liters per second. a 3.5" pipe has a area of about 14 cm^2, so a meter of pipe is about 1.4L, so that 1000 liter/s will be traveling at about 700 meter/second if its at atmospheric pressure. hmmm, that sounds rather way too high (mach 2!), so my math above is likely all wrong. muahahahaha, blame it on the vicodin (I'm stuck at home with a broken right foot, so I can't even drive)