Backpressure

[CHIQLES]

So this thought has been on my mind for a while could the bog down durring acceleration be caused by to much back pressure. I mean say your intake and intercooler pipes are on average 2.5 inches and then include boost pressure theres no way that our little stocker down pipe can kick out this much exhaust. Could that be why our car's only run good at half throttle and bog out at full.

so wouldnt a upgrade down pipe say 2.5 be the most nominal upgrade. I thought about 3 inches but to me that seems to big and our engines arnt that big, exhuast would just hang around and give faulty signals to the o2 sensor.

has any one just upgraded there down pipe and nothing else. what have there experinces been like? are they still haveing similiar issues or differnt ones.or people with 3 inch pipeing what have been your issues do you have longer lag and bo backpressure.

when I drive I can feel the back pressure on the pedal I have realy good throttle responce but as soon as i get past say 60% throttle I can almost feel the exhaust bounce back and drown the car out cuaseing the bog down.
any thought do people have the same experinces what are your theorys what are the best pipe sizes for intercooler and exhuast.
my thoughts are 2.5 hot pipe to intercooler then 2.25 cold to throttle that includes with relocated maf. my thought better responce less lag from turbo to throttle. now for exhaust I say you start at 2.5 j-pipe and get bigger as you go out. well just food for thought.

 

[brkwd51]

wow. that makes a lot of sense. haha. i have never even thought about it that way. well done(2thumbs)

 

[AusOrion]

Remember that exhaust is made up of expanding gases due to the combustion process. I would think that an ideal downpipe would be slightly larger than the intake pipe.

Also, if you think about n/a cars - they suck intake in (no boost) and the exhaust still comes out under pressure.

 

[CHIQLES]

yes but by starting at the same size diameter on the exhaust at the begining point at the j pipe and then getting bigger as you go down the line it will cause the exhaust to go to the point of less resistance which in turn will cause the exhaust to exit faster since it does want to expand.

 

[HighSpeed]

Remember that exhaust is made up of expanding gases due to the combustion process. I would think that an ideal downpipe would be slightly larger than the intake pipe.

Also, if you think about n/a cars - they suck intake in (no boost) and the exhaust still comes out under pressure.

He is right.......3 inch would be more suffice for the exhaust due to the fact that the exhaust gasses are 100x hotter than intake temps and are expanded 3 times as much.

But yeah your right about the downpipe and exhaust.......its the culprit for sure

 

[njaremka]

on a turbo car, bigger is better when it comes to exhaust.

 

[HighSpeed]

right, but the exhaust is being forced out.....exponentially by the engine and turbo. I have had many DSM's with small and big turbos. I would run a stock o2 housing(what we would call the downpipe) and then its bolted to a 3 inch full exhaust. But as soon as I put on a full 3 inch o2 housing the turbo was 2x more responsive and held boost better. The turbo responds better with the least amount of resistance as possible across the turbo overall. So basically........easy air in and easy air out= efficient turbo

 

[njaremka]

right, but the exhaust is being forced out.....exponentially by the engine and turbo. I have had many DSM's with small and big turbos. I would run a stock o2 housing(what we would call the downpipe) and then its bolted to a 3 inch full exhaust. But as soon as I put on a full 3 inch o2 housing the turbo was 2x more responsive and held boost better. The turbo responds better with the least amount of resistance as possible across the turbo overall. So basically........easy air in and easy air out= efficient turbo

like i said, the bigger the better.

 

[CHIQLES]

yes bigger is better, but in my case im going to try to make the exhaust get bigger as it goes out. Giving it direction not a place to linger. well I hope this will help people out.