Exhaust tube size

[Fordverde]

Hi all:

Quick question: what would be the best tube size for a b3(stock, resently overhauled)??
I want to change the tube from the manifold all the way to the back.
Any recommendations?

Thanks

[sasquatch]

2.25 inch is a good size i think.

[bhazard]

I would think 2.25 would be too free flowing for our little motors. 2 inch at most to provide backpressure. The b3 just doesnt move enough air to take advantage of 2.25. Cant really afford to lose low end torque when theres barely any to begin with.

[wrestler3025]

I would have to agree with bhazard on this one. The 94 5.0's came with 2.25 inch exhaust. It would be way overkill for just the stock B3.

[sasquatch]

isnt the fms exhaust 2.25 inch. and dont they say for stock and modded applications or motor swaps. if you do put a 2.25 inch on it then you can do a motor swap and no worry about doing the exhaust later.

[GenevaDirt]

^^yes....but until you do a swap you will notice a performance drop and maybe a decrease in fuel milage. I know that when I had the larger exhaust with 2 cherry bombs on it the car had no power at all...and milage fell off. I put it back to original exhaust and it was a lot more peppy and milage went up by about 3-4 mpg

[Fordverde]

So, should I go with the full 2" or an 1 5/8" tube??? What's the original tube size???

[billthekat]

i just ported my b3 manifold to match my b6 head. and went with a 2" downpipe and 1 and 7/8" tail pipe after a glass pack mufler. and it flows plenty well. i belive that for a stock b3 i wouldent want to go biger than inch and 7/8 or you would lose to much bottom end.

[nonamekid]

I would go 2 inch and then get a restrictive muffler. Later if you put a bigger motor in, switch to a less restrictive muffler.

[NovaSS]

I would not go any larger then a 2.0 and use the best flowing muffler and cat you can get ( affford), needing back pressure in an exhaust system is a myth.

In the old days guys would put on headers and free flowing pipes and the engine would run lean, any damage was caused by not adjusting the carb to compensate with the new free flowing exhuast. So they would blaim "lack of backpressure" as the cause of the problem and not the failure ( of them) to properly tune the carb afterwards.

[alpaccino]

from my personal experience i did a simple muffler pan change and the loss to the back pressure was so significant that in forth and fifth gears the car would just go to sleep on me. so i think i wouldn't want to go so big prob go with billthekat

[alpaccino]

by the way what would be the recommended size for the b5 (i wanted to know this for sometime now)

[funky technician]

I would not go any larger then a 2.0 and use the best flowing muffler and cat you can get ( affford), needing back pressure in an exhaust system is a myth.

In the old days guys would put on headers and free flowing pipes and the engine would run lean, any damage was caused by not adjusting the carb to compensate with the new free flowing exhuast. So they would blaim "lack of backpressure" as the cause of the problem and not the failure ( of them) to properly tune the carb afterwards.

that is correct, I got in an arguement on this forum before about this, few people know this fact

[skeeters_keeper]

back pressure is always bad, on modern engines.. on carb'd cars it can cause the engine to run a little lean, but that's b/c they need to be jetted to compensate for the better air flow through the engine.
here is a decent not too in depth article on exhaust theory... keep in mind this just skims the surface! i've read some much more in depth articles, and still am no where near understanding everything. I would say for a B3 no larger than 2", probably 1 5/8 would be better. a B6 with PnP/header might benefit from 2", which is what i have on my B6, but even then it may be over kill. Toss in a turbo though, and you need to move a much larger volume of air, and so the larger pipes are more efficient.

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

[GenevaDirt]

if it does not need the backpressure then why does it matter what size pipes and muffler you put on it? I am not trying to argue, I am trying to learn. I put a bigger exhaust and cherry bombs on my car and the low end torque was gone along with what little passing ability these cars have, not to mention my gas milage dropped off. Once I put it back to stock exhaust the cars pep was back and so was my gas milage. If it is not back pressure that causes this then what is it?