punchdrunk

Hey

The search is down so I need your opinions on a single exit exhaust I've been offered this;

My limited knowledge of exhausts tells me that 3 inch is best for turbo application and some have noted that it could lose power low down.

Any opinions, experience of larger diameter NA exhausts. The car it's coming off also had a Spoon Manifold & 70mm throttle body and was running NA.

Thanks

s2konroids

76mm seems to big to me

IIWM I'd get a 63 mm for midrange and a little topend, 70mm max for topend.

lucky77

So is it a cut and shut Tanabe/HKS combination? Any pictures of it?

m1bjr

For a turbo car, the less backpressure after the turbine the better.
It only slows spool up and noise is reduced with having a turbine in line anyhow.
The size of manifold tubes is the important bit, and often these are smaller for similar specific output than the NA equivalent to accelerate gas entering the turbo.
Best idea would be a turbo with a stub exhaust to clear the engine bay and absolutely nothing else.

So go for it if building a turbo car, otherwise its highly likely to lose you some performance.
The reson being that the NA tubes are specifically tuned to assist with exhaust gas extraction.
The oem tubes are extremely good at this given their low volume.

lovegroova

I know nothing of exhausts but see the sticky in this forum for an alternative way to search. HTH

oxhouser

keeping the exhaust small in diameter keeps the velocity up, the pulse of gas leaving the system creates a vacuum behind it that helps drag out the remaining fumes from the next cylinder in sequence as the piston is close to TDC its speed and motion is small compared to engine rpm so without this free extraction there is a danger of leaving exhaust gas in the combustion chamber when the valve closes and the intake cycle begins.
a big exhaust will loose mid range torque on NA engine

Fierc3

If you had a 2.5 inch piping, the pipe would stay a certain temp, and gases would also stay hot.
If you had a 3.0 inch pipe, the extra diameter dissipates heat faster, there for your exhaust temps get a little colder.

Its about exhaust temps, which is why some headers are wrapped, to keep the egt's high right out of the cylinder.

Hotter gases are lighter gases, lighter gases move more freely than the denser colder gases.

2.5-2.7 seems to be the sweet spot for na, to keep egts high, and not choke the motor..

hope this made sense..

punchdrunk

Thanks for that Groova

Here's a picture of the exhaust

s2konroids

Which is why i went with 63 for more midrange.

Dont forgot noise i bet it will be mega loud

oxhouser

not quite true
if you cool a hot gas it decreases in volume, if the pipe diameter is standard a decreased volume slows down so keeping the gas warm keeps its velocity up
the down side to keeping everything small bore is it robs top end power so as in all things its about compromise between mid range and top end, longer header pipes would give more mid range but decrease top end, the exhaust system does not have as marked effect as the header but it does have an effect, thats why the small bore singles produce more power, shortest streightest system with a high velocity flow rate