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1 " EMT best flow
Topic Started: Nov 22 2013, 12:01 AM (2,631 Views)
mwebb
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FOG

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this is the second exhaust pipe made from 1" EMT measured OD is about 1 5/32" or about 29mm
replaced the first after 2+ years because i thought it had rusted through .... it did not , rusty but still intact and leak free .
so
after a computer system crash and subsequent repair
after needing to get this software operating as i had a need to test a NON VW car , on the way home from work i left the laptop on the right seat and just played a little
with 1 " EMT pipe pretty much straight from front to back with an angle cut of about 60 degrees in the "tail pipe" exit under the center of the rear bumper over
this is the best flow i have ever measured in this particular car
significantly higher than with stock exhaust with with about 1 1/2" od

so
smaller diameter exhaust pipes , may be the solution to INCREASING exhaust flow and DECREASING exhaust back pressure
depending on the variables involved

this is a stock 10g engine with 162k miles , it has a 3tech economy cam but otherwise internals are not tampered with or rebuilt
does not have a +10 cam wheel , cam timing is OEM


as measured by me , use of the +10 cam wheel significantly REDUCES flow at everyday use engine rpm and is NOT recommended
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pvr007
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To get those type of measurements does your car have to be obd2?
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snowfish
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Basic GearHead

Would love to see some pictures of this exhaust set up. :popcorn
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dayle1960
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Fastest Hampster EVER

1" EMT = Lowe's Electrical Conduit down the electrical aisle?
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Old Man


dayle1960
Nov 22 2013, 05:32 PM
1" EMT = Lowe's Electrical Conduit down the electrical aisle?
Damn grey plastic melts too fast :lol
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mwebb
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FOG

dayle1960
Nov 22 2013, 05:32 PM
1" EMT = Lowe's Electrical Conduit down the electrical aisle?
yes , i did buy mine at Lowes

straight out the back it needs two slight bends
about 5 degrees
, i make the bends by bracing the conduit between two trees in my front yard
hi tech stuff
i suggest the galvanized steel conduit / EMT

i have not tried the plastic stuff .. but i expect it might work for a short while on the rear section of the car

i suspect that at cruise
smaller diameter pipe will flow better , that value above was captured at 5400 rpm and although it shows improvement at WOT over a stock exhaust i am really seeking to improve efficiency at cruise

more testing is required

i will spend another $5 for s suitable length of 3/4" EMT when i get a spare minute , i will need to log VE over time at 60mph with this pipe first then compare to the same value with the smaller pipe

this is OBD2 software it will not work on OBD1 systems
BUT

you can compare engine vacuum measured at the MAP sensor , Teed into the vacuum sensor line , you will need a very accurate vacuum gauge OR use the actual measured MAP sensor signal using a DVOM or a DSO

on the same stretch of road at the same speed and temperature measured increases in vacuum or decreases in MAP signal = greater efficiency of engine operation and this simple test would be useful for any engine modification
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RustyMetro
New Member
[ *  * ]
Thats awesome. I used to think it would be great to have a triple exhuast on the Metro lol nice job
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Jordan


Just curious - have you actually measured backpressure, or are you extrapolating that with better flow less backpressure is inevitable?

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mwebb
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FOG

Jordan
Feb 26 2014, 10:15 PM
Just curious - have you actually measured backpressure, or are you extrapolating that with better flow less backpressure is inevitable?

when i switched to the EMT i started getting EGR faults for low flow
because there was not enough back pressure to open the

EGR back pressure transducer

so i had to bypass the transducer to get the EGR to function again

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idmetro
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Looking forward to your continued testing.
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socal geo garage
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:gp
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davegran
Old Fart w/Wrenches

Interesting stuff. Looking at your screen shot of the EScan application, I wondered why the VE was a spike instead of a sustained value? Was it recording a momentary full throttle excursion as opposed to starting at a relatively low RPM and letting the engine accelerate to peak?
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Jordan


mwebb
Feb 27 2014, 10:33 PM
Jordan
Feb 26 2014, 10:15 PM
Just curious - have you actually measured backpressure, or are you extrapolating that with better flow less backpressure is inevitable?

when i switched to the EMT i started getting EGR faults for low flow
because there was not enough back pressure to open the

EGR back pressure transducer

so i had to bypass the transducer to get the EGR to function again

So you haven't actually checked backpressure?

I think (might be wrong) that you're seeing a venturi effect... you may have increased flow, but pressure hasn't changed. That's why I'm curious as to what the backpressure spec is, if it's actually lowered, or if it's stayed the same. Mostly just idle curiousity.

Pretty cool setup - what kind of scanner are you using?
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mwebb
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FOG

ATS Escan Pro

i have measured back pressure
but
when the EGR opens all back pressure goes crazy as exhaust pulses get mixed with intake pulses
see the yellow trace
EGR opens at the white vertical curser
Posted Image
right lick image , select "view image" from dropdown menu

"have i measured exhaust back pressure ? "
does a pope shit in the woods ?
is a bear catholic ?

useing a scope
that transducer is hard to center on zero ,i have to baseline the trace then subtract that value from the finished result
with the software
having said that
as you can see back pressure is not just a fixed value
it is in constant flux
the exhaust stream pressure is very busy and i have measured it many different ways

measured at the tap for the EGR back pressure transducer
Posted Image

Posted Image
or measuring at the tail pipe , which does not measure back pressure but does measure exhaust stream pressure AND vacuum pulses

still too cold and nasty here to be doing this .... now ....

but see the VE capture above in post 1
values around 3600 rpm to 4000 rpm are 4 to 7% above what was expected .... by the VE software
that is the rpm range i was hoping to optimize for flow

looks good so far
but
who knows
more testing is required

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Jordan


What are the values on the graph? Might not have seen them, just can't tell what the numbers are actually representing.... Vacuum? PSI?

Are you measuring BP at idle, or on the road driving?

Please keep in mind, sounding skeptical is not my intent, I'm very interested in this. Just have some questions that may come across incorrectly in this medium.
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