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| 1 " EMT best flow | |
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| Tweet Topic Started: Nov 22 2013, 12:01 AM (2,629 Views) | |
| mwebb | Nov 22 2013, 12:01 AM Post #1 |
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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 | Nov 22 2013, 01:30 AM Post #2 |
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To get those type of measurements does your car have to be obd2? |
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| snowfish | Nov 22 2013, 05:28 PM Post #3 |
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Basic GearHead
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Would love to see some pictures of this exhaust set up.
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| dayle1960 | Nov 22 2013, 05:32 PM Post #4 |
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Fastest Hampster EVER
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1" EMT = Lowe's Electrical Conduit down the electrical aisle? |
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| Old Man | Nov 22 2013, 05:35 PM Post #5 |
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Damn grey plastic melts too fast
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| mwebb | Nov 23 2013, 10:58 PM Post #6 |
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FOG
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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 | Feb 24 2014, 07:42 PM Post #7 |
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New Member
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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 | Feb 26 2014, 10:15 PM Post #8 |
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Just curious - have you actually measured backpressure, or are you extrapolating that with better flow less backpressure is inevitable? |
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| mwebb | Feb 27 2014, 10:33 PM Post #9 |
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FOG
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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 | Feb 28 2014, 10:22 AM Post #10 |
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Looking forward to your continued testing. |
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| socal geo garage | Feb 28 2014, 10:54 AM Post #11 |
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| davegran | Feb 28 2014, 10:55 AM Post #12 |
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Old Fart w/Wrenches
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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 | Feb 28 2014, 07:52 PM Post #13 |
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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 | Mar 1 2014, 03:46 AM Post #14 |
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FOG
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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 ![]() 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 ![]() 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 | Mar 1 2014, 06:47 AM Post #15 |
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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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7:58 PM Jul 10