So I did some research but unfortunately I couldn’t find anything on having a straight pipe exhaust. I have few questions:

1) If I was about to make a straight pipe exhaust would I need a downpipe and have the Straight pipe run from there to the end?
2) Any advantages or disadvantages beside it being loud? I heard that some back pressure is needed, but the person that told me that didn’t really make much sense so ur comments are appreciated.
3) How much do they generally cost and where could I get it done?
Thanks,

 

a local muffler shop... have them fab you one up.. jus buy a downpipe and have them fab the rest... maybe cost like 300bills... and backpressure.. mehh its a turbo car so the more unrestrictive it is ... the better it is

 

i think 300 would be a lil expenisve for just a straight pipe, i was thinking more of 150. however, i see u mentioned its a turbo car this no need for backpressure, but does that mean it would matter if this was an NA? ifso, then why?
Thanks,

 

jus buy a megan downpipe and test pipe and hook it up with a ebay catback!
cost effective.. i dunno again like i said you can try and see how much they would charge you..

and NA need backpressure because they are obviously naturally aspirated. They need a certain amount of backpressure to operate well

 

its not exacty straight. requires some actual bending ect to be done properly so 300 is cheap. just got off a 16hr day so my brain isnt working well but turbo cars less back pressure the better. with n/a i just know you need some, take it for what its worth until someone smarter and more alert chimes in.

if youre worried about noise get a cutout so its only loud when you want it to be. but that would be more expensive.

 

ya that's true, iam not expecting it to be totaly straight and yes a cut out is an option as well.
how about the hp gains? would it give me more than those well known TBE's?
Thanks,

 

I did it to my car I have a full turbo back no cat and no resonators. I had the muffler hacked off and just a straight 3" pipe welded and bent to perfection. I only had it on the car for a week before I went back with a Muffler . Its just too damn loud for a dd EVO

 

Way too damn loud no difference in performance. Get a muffler!!!!

 

In an N/A car not enough back pressure can cause fresh air out the exhaust during scavenging effect. AMS makes a turn down that you can bolt to the end on a 3" down pipe for $75

http://www.amsperformance.com/store/...oducts_id=1874

 

How could fresh air sneak out of the cylinders in an NA engine? can u explain pls.
thanks,

 

Exhaust flows in pulses. With out back pressure the exhaust gas will cool more rapidly, increasing density and slowing down. With slower moving exhaust gases, you have less scavaging effect and reduced volumetric efficiency. I wasnt thinking correctly and originally typed about reversion. Exhaust gas can re enter the combustion chamber. If gases cool too rapidly and slow down too much, exhaust gas may re enter the combustion chamber. Depending on the cams overlap.

 

Thanks for the explanation but iam still having a tough time understanding ur reasoning. it seems like if the pressure inside the cylinder is greater than the pressure inside the exhuast pipe with the assumption ur running a full straight pipe without any kind of resitrictions (thus the pressure inside the exhuast is at 101 KPA right before the exhuast valve opens up) then the exit velocity should be higher. its becoming almost like a difuser system vs. a nozzle. not sure how else to state my thought, but hope this helps.
Thanks,

 

The exhaust pipe creates a vacuum, depending on the velocity of exhaust, which helps spent combustion escape the chamber as well as bring fresh air into the cylinder. Not sure where youre getting your kPa number from.

Thats why an "H" or "X" pipe makes more power than straight duel exhaust on a V engine. Balance of pulses and increase of scavaging effect.

Exhaust valve event occurs right before BDC. The pressure/energy of the combustion is used to force the piston down, not just out of the chamber. When thinking about it, with less back pressure (N/A), more energy may be wasted pushing exhaust out of the chamber instead of pushing the piston down. Maybe.

 

But back to your topic. I run the QTP cut out. Which isnt a straight pipe, but its basically restrictless. Then it can also be quiet when needed

My boosted civic was open DP. I didnt care, it was quieter than alot of N/a civics lol.

 

what do u think the pressure inside the exhuast pipe right before the exhuast valve pens up? won;t be at the same level as the autmosphere? that's where i got the kpa # from.

i agree with u that the pressure drop would help speed up the flow out of the cylinder, but don't u think if u don;t have any restrictions then u will have a greater pressure delta?

A friend of mine is an exhuast engineer and iam hoping he will get back to me with his opinion as well which i will post on here.
Thanks,